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Sample records for pedicle screw insertion

  1. True anteroposterior view pedicle screw insertion technique

    PubMed Central

    Bai, Jia-yue; Zhang, Wei; An, Ji-long; Sun, Ya-peng; Ding, Wen-yuan; Shen, Yong

    2016-01-01

    Background The wide use of minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) surgery in the treatment of degenerative disc disease of lumbar spine in spinal surgery highlights the gradual decrease in the use of traditional pedicle screw insertion technology. This study aims to analyze the accuracy of the true anteroposterior view pedicle screw insertion technique in MIS-TLIF surgery, compare it with conventional pedicle screw insertion technology, and discuss its clinical application value. Methods Fifty-two patients undergoing true anteroposterior view (group A) and 87 patients undergoing conventional pedicle screw insertion (group B) were diagnosed with lumbar disc herniation or lumbar spinal stenosis. Time for screw placement, intraoperative irradiation exposure, accuracy rate of pedicle screw insertion, and incidence of neurovascular injury were compared between the two groups. Results The time for screw placement and intraoperative irradiation exposure was significantly less in group A. Penetration rates of the paries lateralis of vertebral pedicle, medial wall of vertebral pedicle, and anterior vertebral wall were 1.44%, 0%, and 2.40%, respectively, all of which were significantly lower than that in group B. No additional serious complications caused by the placement of screw were observed during the follow-up period in patients in group A, but two patients with medial penetration underwent revision for unbearable radicular pain. Conclusion The application of true anteroposterior view pedicle screw insertion technique in MIS-TLIF surgery shortens time for screw placement and reduces the intraoperative irradiation exposure along with a higher accuracy rate of screw placement, which makes it a safe, accurate, and efficient technique. PMID:27418828

  2. Isthmus-guided cortical bone trajectory for pedicle screw insertion.

    PubMed

    Iwatsuki, Koichi; Yoshimine, Toshiki; Ohnishi, Yu-ichiro; Ninomiya, Kosi; Ohkawa, Toshika

    2014-08-01

    Herein is described cortical bone trajectory (CBT), a new path for pedicle screw insertion for lumbar vertebral fusion. Because the points of insertion are under the end of the inferior articular process, and because the screws are inserted toward the lateral side, there is less soft tissue development than with the conventional technique; the CBT technique therefore enables less invasive surgery than the conventional technique. However, it has some drawbacks. For example, in the original CBT approach, the points of insertion are in the vicinity of the end of the inferior articular process. Because this joint has been destroyed in many patients who have indications for intervertebral fusion surgery, it is sometimes difficult to use it as a reference point for screw insertion location. With severe lateral slippage, the screw insertion site can become significantly dislocated sideways, with possible resultant damaging to the spinal canal and/or nerve root. The CBT technique here involved inserting the screws while keeping clear of the intervertebral foramen with the assistance of side view X-ray fluoroscopy and using the end of the inferior articular process and the isthmus as points of reference for screw location.

  3. Evaluation of pedicle screw insertion monitored by intraoperative evoked electromyography.

    PubMed

    Darden, B V; Wood, K E; Hatley, M K; Owen, J H; Kostuik, J

    1996-02-01

    The insertion of pedicle screws monitored by evoked electromyography (EMG) was prospectively evaluated in the 132 consecutive patients. The technique involved constant-voltage stimulation and was statistically evaluated at both the arbitrary 20- and 40-V settings. The patients were postoperatively evaluated clinically and radiographically. Computed tomography (CT) scanning was performed for new neurologic deficits. Results were divided into three groups: type 1, a negative EMG response; type 2, a positive EMG response, but no corrective action taken; and type 3, a positive EMG response and corrective action undertaken. Nonparametric statistics were used to evaluate the results at both the 20- and 40-V settings. In the type 3 group, in which corrective action was undertaken, there were no neurologic injuries or screw removals, a statistically significant result. Looking at the two intensity levels, at 20- and 40-V settings, there were no statistically significant differences in the three classifications at either intensity level. We concluded the evoked EMG for monitoring pedicle screw insertion is an efficacious adjunct. A positive response at < 20 V with the constant-voltage technique warrants corrective action.

  4. Quantitative comparison between the straight-forward and anatomical insertion technique for pedicle screw placement

    NASA Astrophysics Data System (ADS)

    Knez, Dejan; Mohar, Janez; Likar, Boštjan; Pernuš, Franjo; Vrtovec, Tomaž

    2016-03-01

    Spinal deformity correction with vertebral fixation is nowadays the preferred surgical treatment, where pedicle screws are inserted through pedicles into corresponding vertebral bodies and afterwards connected with rods. In clinical practice, the straight-forward and anatomical insertion technique are currently being used for pedicle screw placement surgery. However, it is difficult to quantitatively compare both techniques and determine which technique is more adequate for each planned pedicle screw before surgery (i.e. preoperatively). In this paper, we therefore describe a framework for quantitative comparison between the straight-forward and anatomical insertion technique for pedicle screw placement surgery by evaluating the screw fastening strength. Quantitative comparisons were performed on computed tomography images of 11 patients with 74 manually planned pedicle screws, who underwent the vertebral fixation procedure. The first quantitative comparison was performed between the straight-forward and anatomical pedicle screw insertion technique, which resulted in a relatively high agreement with mean absolute difference of 0.0mm in screw diameter, 2.9mm in screw length, 1.2mm in pedicle crossing point and 6.5° in screw inclinations. The second quantitative comparison was performed between the best resulting pedicle screw insertion technique and manually obtained pedicle screw plans, which again resulted in a relatively high agreement with mean absolute difference of 0.5mm in screw diameter, 4.7mm in screw length, 2.4mm in pedicle crossing point and 6.0° in screw inclinations. Both the straight-forward and anatomical insertion technique proved approximately equal in terms of the screw fastening strength.

  5. Subaxial cervical pedicle screw insertion with newly defined entry point and trajectory: accuracy evaluation in cadavers.

    PubMed

    Zheng, Xiujun; Chaudhari, Rahul; Wu, Chunhui; Mehbod, Amir A; Transfeldt, Ensor E

    2010-01-01

    Successful placement of cervical pedicle screws requires accurate identification of both entry point and trajectory. However, literature has not provided consistent recommendations regarding the direction of pedicle screw insertion and entry point location. The objective of this study was to define a guideline regarding the optimal entry point and trajectory in placing subaxial cervical pedicle screws and to evaluate the screw accuracy in cadaver cervical spines. The guideline for entry point and trajectory for each vertebra was established based on the recently published morphometric data. Six fresh frozen cervical spines (C3-C7) were used. There were two men and four women. After posterior exposure, the entry point was determined and the cortical bone of the entry point was removed using a 2-mm burr. Pilot holes were created with a cervical probe based on the guideline using fluoroscopy. After tapping, 3.5-mm screws with appropriate length were inserted. After screw insertion, every vertebra was dissected and inspected for pedicle breach. The pedicle width, height, pedicle transverse angulation and actual screw insertion angle were measured. A total of 60 pedicle screws were inserted. No statistical difference in pedicle width and height was found between the left and right sides for each level. The overall accuracy of pedicle screws was 83.3%. The remaining 13.3% screws had noncritical breach, and 3.3% had critical breach. The critical breach was not caused by the guideline. There was no statistical difference between the pedicle transverse angulation and the actual screw trajectory created using the guideline. There was statistical difference in pedicle width between the breach and non-breach screws. In conclusion, high success rate of subaxial cervical pedicle screw placement can be achieved using the recently proposed operative guideline and oblique views of fluoroscopy. However, careful preoperative planning and good surgical skills are still required to

  6. Novel Landmark for Cervical Pedicle Screw Insertion Point from Computed Tomography-Based Study

    PubMed Central

    2017-01-01

    Study Design Cross-sectional study. Purpose The purpose of this study was to evaluate a novel landmark for the cervical pedicle screw insertion point. Overview of Literature To improve the accuracy of pedicle screw placement, several studies have employed the lateral mass, lateral vertical notch, and/or inferior articular process as landmarks; however, we often encounter patients in whom we cannot identify accurate insertion points for pedicle screws using these landmarks because of degenerative changes in the facet joints. The superomedial edge of the lamina is less affected by degenerative changes, and we hypothesized that it could be a new landmark for identifying an accurate cervical pedicle screw insertion point. Methods A total of 327 consecutive patients, who had undergone neck computed tomographic scanning for determination of neck disease in our institute, were included in the study. At first, the line was drawn parallel to the superior border of the pedicle in the sagittal plane and parallel to the vertical body in the coronal plane. The line was moved downward in 1-mm increments to the inferior border of the pedicle. We determined whether the line passing through the superomedial edge of the lamina (termed the “N-line”) was located between the superior and inferior borders of the pedicle in the sagittal plane. Results The percentages of N-lines located between the superior and inferior borders of the pedicle were 100% at C3, 100% at C4, 99% at C5, 96% at C6, and 97% at C7. The lower cervical spine has the higher N-line location. Conclusions The N-line was frequently located at the level of the pedicle of each cervical spine in the sagittal plane. The superomedial edge of the lamina could be a new landmark for the insertion point of the cervical pedicle screw. PMID:28243374

  7. Medially-shifted rather than high-riding vertebral arteries preclude safe pedicle screw insertion.

    PubMed

    Maki, Satoshi; Koda, Masao; Iijima, Yasushi; Furuya, Takeo; Inada, Taigo; Kamiya, Koshiro; Ota, Mitsutoshi; Saito, Junya; Okawa, Akihiko; Takahashi, Kazuhisa; Yamazaki, Masashi

    2016-07-01

    We enrolled 100 patients who underwent preoperative CT angiography before cervical spine instrumentation and investigated the morphology of the C2 pedicle from the perspective of pedicle screw (PS) trajectory using volume rendering and multiplanar reconstruction. The narrowest portion of the pedicle was identified as the pedicle isthmus. Safe C2 PS insertion was regarded to be not feasible when the height of the medullary cavity of the pedicle isthmus and/or width of the medullary cavity of the pedicle isthmus was ⩽4mm. Forty-five (22.5%) pedicles were ⩽4mm in width, and safe insertion of a PS was determined to be not feasible. Among these, seven pedicles were ⩽4mm in both height and width. The remaining 38 pedicles were ⩽4mm in width with heights >4mm. There was no pedicle with a width >4mm and height <4mm. In other words, short pedicles were always concomitantly narrow. Therefore, the seven pedicles ⩽4mm in both height and width were considered to be morphologically narrow. The heights of the pedicle isthmus were not limited by the vertebral artery groove (VAG) and safe C2 PS insertion can be considered feasible where the VAG is marginally cranial, whereas the widths of the pedicle isthmus are limited by the VAG. Therefore, safe C2 PS insertion is precluded only when the VAG courses cranially and medially. It is a medially-shifted, rather than a high-riding, vertebral artery that precludes safe C2 PS insertion. Therefore to avoid vertebral artery injury an axial CT scan, parallel to the pedicle axis, should be evaluated before C2 PS insertion.

  8. Morphometric analysis of the seventh cervical vertebra for pedicle screw insertion

    PubMed Central

    Liao, Wensheng; Guo, Liangbing; Bao, Heng; Wang, Limin

    2015-01-01

    Background: Anatomy of the pedicles of the seventh cervical vertebra (C7) at the cervicothoracic junction is different from other cervical vertebrae. Fixation of C7 is required during cervical vertebra and upper thoracic injuries in clinical practice. However, the typical pedicle screw insertion methods may have problems in clinical practice based on the anatomical features of C7. This study is to explore a new pedicle screw insertion technique for C7 and to provide anatomical and radiographic basis for clinical application. Materials and Methods: C7 vertebral specimens from six human cadavers were observed for the relative position between the posterior bony landmark and the pedicle projection. Computed tomography (CT) was performed for 30 patients with cervical spondylosis (26–61 years old, mean age was 42.3 years old). The CT scan data were processed by Mimics 8.1 software for associated parameter measurement. Appropriate screw entry points (Eps) and insertion angles were selected. A total of 12 pedicle screws were inserted and then observed. The six specimens were observed after inserting the screw using this method. The junction site of the middle 1/3 and outer 1/3 segment of line G [The junction between point A (the intersection point of the superior margin of the lamina of C7 and the medial margin of the superior articular process) and point B (the intersection point of the lateral margin of the inferior articular process and the transverse process)] was taken as the Ep. The screw insertion direction parallel horizontally to the upper terminal lamina of C7 and the sagittal angle was between 35° and 45°. Results: Gross and imaging observations revealed that pedicle projection was on the line (line G) between point A (the intersection point of the superior margin of the lamina of C7 and the medial margin of the superior articular process) and point B (the intersection point of the lateral margin of the inferior articular process and the transverse process

  9. In vitro study of accuracy of cervical pedicle screw insertion using an electronic conductivity device (ATPS part III).

    PubMed

    Koller, Heiko; Hitzl, Wolfgang; Acosta, Frank; Tauber, Mark; Zenner, Juliane; Resch, Herbert; Yukawa, Yasutsugu; Meier, Oliver; Schmidt, Rene; Mayer, Michael

    2009-09-01

    Reconstruction of the highly unstable, anteriorly decompressed cervical spine poses biomechanical challenges to current stabilization strategies, including circumferential instrumented fusion, to prevent failure. To avoid secondary posterior surgery, particularly in the elderly population, while increasing primary construct rigidity of anterior-only reconstructions, the authors introduced the concept of anterior transpedicular screw (ATPS) fixation and plating. We demonstrated its morphological feasibility, its superior biomechanical pull-out characteristics compared with vertebral body screws and the accuracy of inserting ATPS using a manual fluoroscopically assisted technique. Although accuracy was high, showing non-critical breaches in the axial and sagittal plane in 78 and 96%, further research was indicated refining technique and increasing accuracy. In light of first clinical case series, the authors analyzed the impact of using an electronic conductivity device (ECD, PediGuard) on the accuracy of ATPS insertion. As there exist only experiences in thoracolumbar surgery the versatility of the ECD was also assessed for posterior cervical pedicle screw fixation (pCPS). 30 ATPS and 30 pCPS were inserted alternately into the C3-T1 vertebra of five fresh-frozen specimen. Fluoroscopic assistance was only used for the entry point selection, pedicle tract preparation was done using the ECD. Preoperative CT scans were assessed for sclerosis at the pedicle entrance or core, and vertebrae with dense pedicles were excluded. Pre- and postoperative reconstructed CT scans were analyzed for pedicle screw positions according to a previously established grading system. Statistical analysis revealed an astonishingly high accuracy for the ATPS group with no critical screw position (0%) in axial or sagittal plane. In the pCPS group, 88.9% of screws inserted showed non-critical screw position, while 11.1% showed critical pedicle perforations. The usage of an ECD for posterior and

  10. Position and complications of pedicle screw insertion with or without image-navigation techniques in the thoracolumbar spine: a meta-analysis of comparative studies.

    PubMed

    Tang, Jinshan; Zhu, Ziqiang; Sui, Tao; Kong, Dechao; Cao, Xiaojian

    2014-05-01

    Computer-navigated pedicle screw insertion is applied to the thoracic and lumbar spine to attain high insertion accuracy and a low rate of screw-related complications. However, some in vivo and in vitro studies have shown that no advantages are gained with the use of navigation techniques compared to conventional techniques. Additionally, inconsistent conclusions have been drawn in various studies due to different population characteristics and methods used to assess the accuracy of screw placement. Moreover, it is not clear whether pedicle screw insertion with navigation techniques decreases the incidence of screw-related complications. Therefore, this study was sought to perform a meta-analysis of all available prospective evidence regarding pedicle screw insertion with or without navigation techniques in human thoracic and lumbar spine. We considered in vivo comparative studies that assessed the results of pedicle screw placement with or without navigation techniques. PubMed, Ovid MEDLINE and EMBASE databases were searched. Three published randomized controlled trials (RCTs) and nine retrospective comparative studies met the inclusion criteria. These studies included a total of 732 patients in whom 4,953 screws were inserted. In conclusion, accuracy of the position of grade I, II, III and IV screws and complication rate related to pedicle screw placement were significantly increased when navigation techniques were used in comparison to conventional techniques. Future research in this area should include RCTs with well-planned methodology to limit bias and report on validated, patient-based outcome measures.

  11. Evaluating Accuracy of Free-hand Pedicle Screw Insertion in Adolescent Idiopathic Scoliosis Using Postoperative Multi-Slice Computed Tomography Scan

    PubMed Central

    Etemadifar, Mohammadreza; Jamalaldini, Mohammadhossein

    2017-01-01

    Background: Pedicle screw instrumentation has many advantages for correction of adolescent idiopathic scoliosis (AIS) deformity including better correction and fewer late complications. On the other hand, screw insertion in AIS is challenging. Intraoperative fluoroscopy or navigation techniques are expensive, time-consuming, and exposed to high radiation. Free-hand technique relies on the surgeon's experience and locating the pedicle entry point with anatomical landmarks. There are few studies that evaluated pedicle screw position accuracy with postoperative multi-slice computed tomography scan. Materials and Methods: We prospectively considered 38 consecutive AIS cases, who underwent corrective surgery with all pedicle screw technique. All the screws were inserted with free-hand technique using anatomic landmarks as a guide for an entry site. We divided pedicle penetration in medial, lateral, inferior, superior, and anterior vertebral body as Grades 0–4, that Grade 0 is fully contained within the pedicle, Grade 1 (<2 mm), Grade 2 (2.1–4 mm), Grade 3 (4.1–6 mm), and Grade 4 (>6 mm). Results: A total of 720 screws were inserted, of which 623 screws (86.5%) were perfect and 97 screws (13.5%) were misplaced. Of those which were misplaced, 39 screws (40.2%) were medial and 58 (59.8%) were lateral, which shows that the prevalence of lateral misplacement was more in comparison to medial misplacement. However, in all misplaced cases, the deviation of the screw was <2 mm (Grade 1). There was no misplacement in the inferior and superior. Conclusion: Pedicle screw insertion in AIS with the free-hand technique is a safe and reliable method. PMID:28349022

  12. Comparison study of the pullout strength of conventional spinal pedicle screws and a novel design in full and backed-out insertions using mechanical tests.

    PubMed

    Amaritsakul, Yongyut; Chao, Ching-Kong; Lin, Jinn

    2014-03-01

    Recently, new pedicle screw designs have been developed. However, these designs' performances are still unclear, especially when backed out after insertion. The objective of this study was to investigate the performances of different screw designs when backed out from full insertion. Seven conventional designs of the pedicle screw and one novel design were inserted into polyurethane foam (0.32 g/cm(3)). All screws were first fully inserted (43 mm) and were backed out 360°. Axial pullout tests were performed and the reaction force was measured. The results showed that the conical screw of type 1 with a small inner diameter provided the highest pullout strength in both full insertion and backed-out insertion (2401.85 and 2169.82 N, respectively). However, this screw's pullout strength significantly decreased (9.7%) when backed out from full insertion. There was no significant difference between the conical screw of type 1 with a small inner diameter and double duo core screw (p > 0.01) in backed-out insertion. The cylindrical screw with a small diameter, dual inner core screw and double dual core screw also provided good results in both full insertion (2115.44, 2182.99 and 2226.93 N, respectively) and backed-out conditions (2065.80, 2014.28 and 1941.29 N, respectively). The increased pullout strength of the conical design could be due to the effect of bone compaction. However, the screw exhibited less consistent pullout strength when backed out when compared with the other designs. The conical screw should be inserted to the precise position without turning back, especially in osteoporosis patients. The dual inner core screw and double dual core screw could provide greater stability in both conditions. Care should be taken when using both the cylindrical screw with a small thread depth and the dual outer core screw.

  13. A Novel Patient-Specific Drill Guide Template for Pedicle Screw Insertion into the Subaxial Cervical Spine Utilizing Stereolithographic Modelling: An In Vitro Study

    PubMed Central

    Delgado, Giorgio De Guzman; Grozman, Samuel Arsenio Munoz

    2017-01-01

    Study Design Cadaveric study. Purpose The purpose of this study was to assess the accuracy and feasibility of cervical pedicle screw (CPS) insertion into the subaxial cervical spine placed using a patient-specific drill guide template constructed from a stereolithographic model. Overview of Literature CPS fixation is an invaluable tool for posterior cervical fixation because of its biomechanical advantages. The major drawback is its narrow corridor that allows very little clearance for neural and vascular injuries. Methods Fifty subaxial pedicles of the cervical vertebrae from five cadavers were scanned into thin slices using computed tomography (CT). Digital imaging and communications in medicine images of the cadaver spine were digitally processed and printed to scale as a three-dimensional (3D) model. Drill guide templates were manually moulded over the 3D-printed models incorporating pins inserted in the pedicles. The drill guide templates were used for precise placement of the drill holes in the pedicles of cadaveric specimens for pedicle screw fixation. Results The instrumented cadaveric spines were subjected to CT to assess the accuracy of our pedicle placement by an external observer. Our patient-specific drill guide template had an accuracy of 94%. Conclusions The use of a patient-specific drill guide constructed using stereolithography improved the accuracy of CPS placement in a cadaveric model. PMID:28243363

  14. Surgeon's view of pedicle screw implantation for the monitoring neurophysiologist.

    PubMed

    Joglekar, Siddharth B; Mehbod, Amir A

    2012-12-01

    Pedicle screws have become the gold standard of spinal instrumentation over the past decade owing to their biomechanical superiority. Despite their advantages, pedicle screw instrumentation is potentially dangerous, and surgeons wish to improve accuracy of screw placement to avoid complications associated with screw misplacement. The anatomy of the pedicles is variable throughout the spine, and several landmarks and trajectories have been suggested to aid safe placement of pedicle screws in the spine. Several techniques such as x-ray and computed tomography scan imaging coupled with computer-aided navigation are available to improve accuracy of screw insertion. Intraoperative neuromonitoring with the help of triggered electromyographic recordings has evolved as an objective evidence of assessing pedicle breach and proximity of the screw to neural structures. While all imaging and electrophysiological modalities should be applied on an individualized basis, finally no adjunctive technique can fully replace the need for surgical expertise and experience.

  15. Electromagnetic Navigation in Minimally Invasive Spine Surgery: Results of a Cadaveric Study to Evaluate Percutaneous Pedicle Screw Insertion

    PubMed Central

    Fraser, Justin F.; Von Jako, Ron; Carrino, John A.

    2008-01-01

    Background This cadaveric study compared efficacy and safety of an electromagnetic (EM) guidance system versus conventional fluoroscopy for percutaneous pedicle screw fixation. As percutaneous pedicle screw fixation becomes increasingly common in spinal surgery, intraoperative imaging systems that maximize efficiency while minimizing radiation exposure and inaccurate trajectories will be progressively more important. Published studies have validated the safety of percutaneous screw fixation using conventional fluoroscopic guidance and frameless optical stereotaxy, though EM guidance systems have not been evaluated for percutaneous placement in the lumbosacral spine. The aim of the study was to evaluate the clinical applicability of an EM system for minimally invasive spine fusion in the lumbosacral spine. Methods Five human cadaveric specimens underwent bilateral lumbosacral percutaneous screw fixation from L1 to S1 using conventional anteroposterior (AP) and lateral fluoroscopic techniques on one side and 2-dimesional (2D) EM guidance on each matching side. Intraoperative efficiency was evaluated, and pedicle, vertebral, and critical breach rates were assessed on postoperative computed tomography (CT). Results Overall mean fluoroscopy time per screw was 58.9 ± 44.7 seconds for conventional fluoroscopy compared to 27.4 ± 13.5 seconds for electromagnetic guidance (P = .0003). Pedicle, vertebral, and critical breach rates for the L1-S1 were 32.1%, 10.7%, and 25.0% for conventional fluoroscopy and 42.8%, 10.7%, and 14.1% for electromagnetic guidance (difference not statistically significant [ns]). In comparing critical breaches in the lumbar spine (L1-L5), there was a significant difference between 2-D EM guidance (0) and CF guidance (6) (P = .02). Conclusions Two-dimensional EM navigation provides a modality for lumbosacral percutaneous pedicle screw fixation that is more efficient and safer than conventional fluoroscopy. This data provides a foundation for further

  16. Occam Paradox? A Variation of Tapia Syndrome and an Unreported Complication of Guidewire-Assisted Pedicle Screw Insertion

    PubMed Central

    Emohare, Osa; Peterson, Erik; Slinkard, Nathaniel; Janus, Seth; Morgan, Robert

    2013-01-01

    Study Design Case report. Clinical Question The clinical aim is to report on a previously unknown association between guidewire-assisted pedicle screw insertion and neuropraxia of the recurrent laryngeal nerve (RLN), and how this may overlap with the signs of Tapia syndrome; we also report our approach to the clinical management of this patient. Methods A 17-year-old male patient with idiopathic scoliosis experienced Tapia syndrome after posterior instrumentation and arthrodesis at the level of T1–L1. After extubation, the patient had a hoarse voice and difficulty in swallowing. Imaging showed a breach in the cortex of the anterior body of T1 corresponding to the RLN on the right. Results Otolaryngological examination noted right vocal fold immobility, decreased sensation of the endolarynx, and pooling of secretions on flexible laryngoscopy that indicated right-sided cranial nerve X injury and left-sided tongue deviation. Aspiration during a modified barium swallow prompted insertion of a percutaneous endoscopic gastrostomy tube before the patient was sent home. On postoperative day 20, a barium swallow demonstrated reduced aspiration, and the patient reported complete resolution of symptoms. The feeding tube was removed, and the patient resumed a normal diet 1 month later. Tapia syndrome, or persistent unilateral laryngeal and hypoglossal paralysis, is an uncommon neuropraxia, which has previously not been observed in association with a breached vertebral body at T1 along the course of the RLN. Conclusion Tapia syndrome should be a differential diagnostic consideration whenever these symptoms persist postoperatively and spine surgeons should be aware of this as a potential complication of guidewires in spinal instrumentation. PMID:24436711

  17. A biomechanical study of two different pedicle screw methods for fixation in osteoporotic and nonosteoporotic vertebrae.

    PubMed

    Higashino, Kosaku; Kim, Jin Hwan; Horton, William C; Hutton, William C

    2012-01-01

    In reconstruction of the osteoporotic spine, patients often show poor outcome because of pedicle screw failure. This study used osteoporotic and nonosteoporotic vertebrae to determine the difference in fixation strength between pedicle screws inserted straight forward and pedicle screws inserted in an upward trajectory toward the superior end plate (i.e., end-plate screws). There is some evidence to suggest that end-plate screws have a strength advantage. The particular focus was on osteoporotic vertebrae. Thirty-three vertebrae (T10-L2) were harvested. The bone mineral density (BMD) was measured: 15 vertebrae were greater than 0.8 g/cm(2) and designated as nonosteoporotic (average BMD 1.146 ± 0.186 g/cm(2)) and 18 vertebrae were designated as osteoporotic (average BMD 0.643 ± 0.088 g/cm(2)). On one pedicle the screw was inserted straight forward and on the other pedicle the screw was inserted as an end-plate screw. The torque of insertion was measured (Proto 6106 torque screwdriver). Using an MTS Mini Bionix, two types of mechanical testing were carried out on each pedicle: (a) cephalocaudad toggling was first carried out to simulate some physiological type loading: 500 cycles at 0.3 Hz, at ±50 N; and (b) then each pedicle screw was pulled out at a displacement rate of 12.5 cm/min.There was no difference in pullout force between the pedicle screws inserted straight forward and the pedicle screws inserted as end-plate screws. This result applies whether the vertebrae were osteoporotic or nonosteoporotic. For both the straight-forward screws and the end-plate screws, a statistically significant correlation was observed between torque of insertion and pullout force. The results of this experiment indicate that pedicle screws inserted as end-plate screws do not provide a strength advantage over pedicle screws inserted straight forward, whether the vertebrae are osteoporotic or not.

  18. Accuracy of Percutaneous Pedicle Screw Insertion Technique with Conventional Dual Fluoroscopy Units and a Retrospective Comparative Study Based on Surgeon Experience.

    PubMed

    Nakahara, Masayuki; Yasuhara, Takao; Inoue, Takafumi; Takahashi, Yuichi; Kumamoto, Shinji; Hijikata, Yasukazu; Kusumegi, Akira; Sakamoto, Yushi; Ogawa, Koichi; Nishida, Kenki

    2016-06-01

    Study Design Retrospective comparative study. Objective To evaluate the accuracy of percutaneous pedicle screw (PPS) placement and intraoperative imaging time using dual fluoroscopy units and their differences between surgeons with more versus less experience. Methods One hundred sixty-one patients who underwent lumbar fusion surgery were divided into two groups, A (n = 74) and B (n = 87), based on the performing surgeon's experience. The accuracy of PPS placement and radiation time for PPS insertion were compared. PPSs were inserted with classic technique under the assistance of dual fluoroscopy units placed in two planes. The breach definition of PPS misplacement was based on postoperative computed tomography (grade I: no breach; grade II: <2 mm; grade III: ≤2 to <4 mm). Results Of 658 PPSs, only 21 screws were misplaced. The breach rates of groups A and B were 3.3% (grade II: 3.4%, grade III: 0%) and 3.1% (grade II: 2.6%, grade III: 0.6%; p = 0.91). One patient in grade III misplacement had a transient symptom of leg numbness. Median radiation exposure time during PPS insertion was 25 seconds and 51 seconds, respectively (p < 0.01). Conclusions Without using an expensive imaging support system, the classic technique of PPS insertion using dual fluoroscopy units in the lumbar and sacral spine is fairly accurate and provides good clinical outcomes, even among surgeons lacking experience.

  19. Pullout performance comparison of novel expandable pedicle screw with expandable poly-ether-ether-ketone shells and cement-augmented pedicle screws.

    PubMed

    Aycan, Mehmet Fatih; Tolunay, Tolga; Demir, Teyfik; Yaman, Mesut Emre; Usta, Yusuf

    2017-02-01

    Aim of this study is to assess the pullout performance of various pedicle screws in different test materials. Polyurethane foams (Grade 10 and Grade 40) produced in laboratory and bovine vertebrae were instrumented with normal, cannulated (cemented), novel expandable and normal (cemented) pedicle screws. Test samples were prepared according to the ASTM F543 standard testing protocols and surgical guidelines. To examine the screw placement and cement distribution, anteriosuperior and oblique radiographs were taken from each sample after insertion process was completed. Pullout tests were performed in an Instron 3369 testing device. Load versus displacement graphs were recorded and the ultimate pullout force was defined as the maximum load (pullout strength) sustained before failure of screw. Student's t-test was performed on each group whether the differences between pullout strength of pedicle screws were significant or not. While normal pedicle screws have the lowest pullout strength in all test materials, normal pedicle screws cemented with polymethylmethacrylate exhibit significantly higher pullout performance than others. For all test materials, there is a significant improvement in pullout strength of normal screws by augmentation. While novel expandable pedicle screws with expandable poly-ether-ether-ketone shells exhibited lower pullout performance than normal screws cemented with polymethylmethacrylate, their pullout performances in all groups were higher than the ones of normal and cannulated pedicle screws. For all test materials, although cannulated pedicle screws exhibit higher pullout strength than normal pedicle screws, there are no significant differences between the two groups. The novel expandable pedicle screws with expandable poly-ether-ether-ketone shells may be used instead of normal and cannulated pedicle screws cemented with polymethylmethacrylate due to their good performances.

  20. Accuracy of pedicle screw placement using intraoperative neurophysiological monitoring and computed tomography.

    PubMed

    Mavrogenis, Andreas F; Papagelopoulos, Panayiotis J; Korres, Demetrios S; Papadopoulos, Konstantinos; Sakas, Damianos E; Pneumaticos, Spiros

    2009-01-01

    Fifty consecutive patients with posterior thoracolumbar spine fusion were included in a prospective study to determine the accuracy of intraoperative neurophysiological monitoring (IONM) for safe pedicle screw placement using postoperative computed tomography (CT). The patients were allocated into two equal groups. Pedicle screw placement was evaluated intraoperatively by using the image intensifier. In group A, the integrity of the pedicle wall was evaluated intraoperatively with monopolar stimulation of each screw head with a hand-held single-tip stimulator; the compound muscle action potentials were recorded. A constant current threshold of 7 mA was considered indicative of pedicle breach; < 7 mA was considered as direct contact with neural elements, and > 7mA was considered normal. In group B, pedicle screw placement was performed without IONM. Overall, 306 pedicle screws were inserted in both groups. Postoperatively, all patients underwent CT scans of the spine to evaluate pedicle screw placement. Intraoperatively, five screws in respective group A patients had to be repositioned after IONM (threshold of < 7 mA); in these patients, postoperative CT scans showed proper screw placement. Postoperative CT scans showed eight misdirected screws; two screws (1.26%) in group A patients and six screws (4%) in group B patients. Two screws were misdirected through the medial pedicle wall and six screws were misdirected through the lateral pedicle wall. Both medially misdirected screws were observed in group B patients (1.35%); these patients developed neurologic symptoms postoperatively and underwent revision surgery, with redirection of the misdirected screws and subsequent resolution of the neurologic symptoms. Two of the six laterally misdirected screws were observed in group A patients (1.26%); the remaining four laterally misdirected screws were observed in group B patients (2.7%). None of these patients had neurologic sequelae; no revision surgery was required. The

  1. Safety of thoracic pedicle screw application using the funnel technique in Asians: a cadaveric evaluation.

    PubMed

    Chan, Chris Yin Wei; Kwan, Mun Keong; Saw, Lim Beng

    2010-01-01

    The objective of this cadaveric study is to determine the safety and outcome of thoracic pedicle screw placement in Asians using the funnel technique. Pedicle screws have superior biomechanical as well as clinical data when compared to other methods of instrumentation. However, misplacement in the thoracic spine can result in major neurological implications. There is great variability of the thoracic pedicle morphometry between the Western and the Asian population. The feasibility of thoracic pedicle screw insertion in Asians has not been fully elucidated yet. A pre-insertion radiograph was performed and surgeons were blinded to the morphometry of the thoracic pedicles. 240 pedicle screws were inserted in ten Asian cadavers from T1 to T12 using the funnel technique. 5.0 mm screws were used from T1 to T6 while 6.0 mm screws were used from T7 to T12. Perforations were detected by direct visualization via a wide laminectomy. The narrowest pedicles are found between T3 and T6. T5 pedicle width is smallest measuring 4.1 +/- 1.3 mm. There were 24 (10.0%) Grade 1 perforations and only 1 (0.4%) Grade 2 perforation. Grade 2 or worse perforation is considered significant perforation which would threaten the neural structures. There were twice as many lateral and inferior perforations compared to medial perforations. 48.0% of the perforations occurred at T1, T2 and T3 pedicles. Pedicle fracture occurred in 10.4% of pedicles. Intra-operatively, the absence of funnel was found in 24.5% of pedicles. In conclusion, thoracic pedicle screws using 5.0 mm at T1-T6 and 6.0 mm at T7-T12 can be inserted safely in Asian cadavers using the funnel technique despite having smaller thoracic pedicle morphometry.

  2. The rate of screw misplacement in segmental pedicle screw fixation in adolescent idiopathic scoliosis

    PubMed Central

    2011-01-01

    Background and purpose There are no reports in the literature on the influence of learning on the pedicle screw insertion. We studied the effect of learning on the rate of screw misplacement in patients with adolescent idiopathic scoliosis treated with segmental pedicle screw fixation. Method We retrospectively evaluated low-dose spine computed tomography of 116 consecutive patients (aged 16 (12–24) years, 94 females) who were operated during 4 periods over 2005–2009 (group 1: patients operated autumn 2005–2006; group 2: 2007; group 3: 2008; and group 4: 2009). 5 types of misplacement were recorded: medial cortical perforation, lateral cortical perforation, anterior cortical perforation of the vertebral body, endplate perforation, and perforation of the neural foramen. Reslts 2,201 pedicle screws were evaluated, with an average of 19 screws per patient. The rate of screw misplacement for the whole study was 14%. The rate of lateral and medial cortical perforation was 7% and 5%. There was an inverse correlation between the occurrence of misplacement and the patient number, i.e. the date of operation (r = –0.35; p < 0.001). The skillfulness of screw insertion improved with reduction of the rate of screw misplacement from 20% in 2005–2006 to 11% in 2009, with a breakpoint at the end of the first study period (34 patients). Interpretation We found a substantial learning curve; cumulative experience may have contributed to continued reduction of misplacement rate. PMID:21189100

  3. Cervical pedicle screw fixation in traumatic cervical subluxation after laminectomy using the pedicle axis view technique under fluoroscopy.

    PubMed

    Machino, Masaaki; Yukawa, Yasutsugu; Ito, Keigo; Nakashima, Hiroaki; Kanbara, Shunsuke; Morita, Daigo; Kato, Fumihiko

    2012-10-10

    Cervical pedicle screw (CPS) fixation has recently been performed in patients in need of cervical reconstruction. We report the case of a 50-year-old man who was operated for traumatic cervical vertebra subluxation using CPS fixation, in whom laminectomy had been performed in the past. We performed CPS fixation using the pedicle axis view technique under fluoroscopy. The four pedicle screws were accurately inserted within the pedicles without perforating the bone cortex of the pedicles. A navigation system is useful for cervical spine surgery because it enables a surgeon to perform relatively safe and accurate surgery during transpedicular screw fixation. However, attachment of the stereotactic reference arc to the spinous process is impossible, and the application of a navigation system is limited in cases in which laminectomy has been performed in the past. We have been using the pedicle axis view technique under fluoroscopy and have found that if we take care of the entry point accurately, we can safely insert the pedicle screw in cases with fewer landmarks.

  4. Innovative approach in the development of computer assisted algorithm for spine pedicle screw placement.

    PubMed

    Solitro, Giovanni F; Amirouche, Farid

    2016-04-01

    Pedicle screws are typically used for fusion, percutaneous fixation, and means of gripping a spinal segment. The screws act as a rigid and stable anchor points to bridge and connect with a rod as part of a construct. The foundation of the fusion is directly related to the placement of these screws. Malposition of pedicle screws causes intraoperative complications such as pedicle fractures and dural lesions and is a contributing factor to fusion failure. Computer assisted spine surgery (CASS) and patient-specific drill templates were developed to reduce this failure rate, but the trajectory of the screws remains a decision driven by anatomical landmarks often not easily defined. Current data shows the need of a robust and reliable technique that prevents screw misplacement. Furthermore, there is a need to enhance screw insertion guides to overcome the distortion of anatomical landmarks, which is viewed as a limiting factor by current techniques. The objective of this study is to develop a method and mathematical lemmas that are fundamental to the development of computer algorithms for pedicle screw placement. Using the proposed methodology, we show how we can generate automated optimal safe screw insertion trajectories based on the identification of a set of intrinsic parameters. The results, obtained from the validation of the proposed method on two full thoracic segments, are similar to previous morphological studies. The simplicity of the method, being pedicle arch based, is applicable to vertebrae where landmarks are either not well defined, altered or distorted.

  5. Cortical bone trajectory screws placement via pedicle or pedicle rib unit in the pediatric thoracic spine (T9-T12)

    PubMed Central

    Xuan, Jun; Chen, Jian; He, Hui; Jin, Hai-Ming; Zhang, Di; Wu, Yao-Sen; Tian, Nai-Feng; Wang, Xiang-Yang

    2017-01-01

    Abstract Thoracic cortical bone trajectory (CBT) screw fixation can maximize the thread contact with cortical bone, and it is 53.8% higher than that of the traditional pedicle screws. Moreover, it can also enable less tissue dissection and retraction for reduced muscle disruption. Eighty pediatric patients are divided into 4 age groups and their thoracic vertebrae are analyzed on computed tomography (CT) images. The maximal screw length, maximal screw diameter, screw diameter, and the cephalad angle are measured. The statistical analysis is performed using the Student's t-test and Pearson's correlation analysis. Maximal screw length increases from T9 to T12 and there are significant differences between girls and boys at T9, T10, T11, and T12 in majority of groups (P < 0.05). The maximal screw diameter and screw diameter increase from T9 to T12. The maximal screw diameter ranges from 6.27 mm to 10.20 mm, whereas the screw diameter ranges from 3.87 mm to 6.75 mm. Meanwhile, the maximum cephalad angle is 23.06° and the minimum is 13.11°. No statistically significant differences in the cephalad angle are found at all levels. Our study establishes the feasibility of 4.5 to 5.5 mm CBT screws fixation via pedicle or pedicle rib unit in the pediatric thoracic spine. The entry point of the pediatric thoracic CBT screws is 6 o’clock orientation of the pedicle. Findings of our study also provide insights into the screw insertion angle and screw size decision. PMID:28151859

  6. [Cement augmentation of pedicle screws : Pros and cons].

    PubMed

    Schnake, K J; Blattert, T R; Liljenqvist, U

    2016-09-01

    Cement augmentation of pedicle screws biomechanically increases screw purchase in the bone. However, clinical complications may occur. The pros and cons of the technique are discussed from different clinical perspectives.

  7. Short-Term Results of Transforaminal Lumbar Interbody Fusion Using Pedicle Screw with Cortical Bone Trajectory Compared with Conventional Trajectory

    PubMed Central

    Miyakoshi, Naohisa; Hongo, Michio; Ishikawa, Yoshinori; Kudo, Daisuke; Shimada, Yoichi

    2015-01-01

    Study Design Case-control study. Purpose To evaluate clinical and radiological results of transforaminal lumbar interbody fusion (TLIF) performed with cortical bone trajectory (CBT) pedicle screw insertion with those of TLIF using 'conventional' or percutaneous pedicle screw insertion. Overview of Literature CBT is a new trajectory for pedicle screw insertion in the lumbar spine; clinical and radiological results of TLIF using pedicle screws inserted with CBT are unclear. Methods In total, 26 patients (11 males, 15 females) were enrolled in this retrospective study and divided into three groups: TLIF with pedicle screw insertion by conventional minimally invasive methods via the Wiltse approach (M-TLIF, n=10), TLIF with percutaneous pedicle screw insertion (P-TLIF, n=6), and TLIF with pedicle screw insertion with CBT (CBT-TLIF, n=10). Surgical results and preand postoperative radiological findings were evaluated and compared. Results Intraoperative blood loss was significantly less with CBT-TLIF (p=0.03) than with M-TLIF. Postoperative lordotic angles did not differ significantly among the three groups. Complete fusions were obtained in 10 of 12 levels (83%) with M-TLIF, in seven levels (100%) with P-TLIF, and in 10 of 11 levels (91%) with CBT-TLIF. On postoperative computed tomography, correct positioning was seen in 84.1% of M-TLIF screws, 88.5% of P-TLIF screws, and 90% of CBT-TLIF screws. Conclusions CBT-TLIF resulted in less blood loss and a shorter operative duration than M-TLIF or P-TLIF. Postoperative rates of bone union, maintenance of lordotic angles, and accuracy of pedicle screw positions were similar among the three groups. PMID:26097661

  8. Biomechanical comparison of anatomic trajectory pedicle screw versus injectable calcium sulfate graft-augmented pedicle screw for salvage in cadaveric thoracic bone.

    PubMed

    Derincek, Alihan; Wu, Chunhui; Mehbod, Amir; Transfeldt, Ensor E

    2006-06-01

    Many salvage options for failed thoracic pedicle screws exist including the use of a different trajectory or the augmentation of the screw with polymethylmethacrylate cement. Although polymethylmethacrylate immediately increases the construct stiffness and the pull-out strength, it may cause bone necrosis, toxin relaxation, and/or neural injury. On the other hand, calcium sulfate bone grafts have a high potential for biologic incorporation and no thermal damage effect. In the current study, polyaxial pedicle screws were first inserted with a straightforward approach on both sides in 17 fresh human cadaveric thoracic vertebrae. The maximal insertion torque for each screw was measured and then the pull-out strengths were recorded. Afterward, these pedicle screws were randomly assigned to be replaced either by graft augmentation or by anatomic trajectory technique for salvage. The graft-augmented screws were placed using the previous holes. The maximum insertional torque for each anatomic trajectory screw was measured. Finally, the pull-out strengths of the revision screws were recorded. The mean maximum insertional torque decreased with the anatomic trajectory salvage technique when compared with the straightforward approach, 0.23 versus 0.38 Nm, respectively (P=0.003). The anatomic trajectory revision resulted in decreased pull-out strength when compared with the pull-out strength of the straightforward technique, 297 versus 469 N, respectively (P=0.003). The calcium sulfate graft augmentation increased the pull-out strength when compared with the pull-out strength of the straightforward technique, 680 versus 477 N, respectively (P=0.017). The mean pull-out strength ratio of revised screw to original was 0.71 for anatomic trajectory and 1.8 for graft-augmented screws, a statistically significant difference (P=0.002).

  9. Robot assisted navigated drilling for percutaneous pedicle screw placement: A preliminary animal study

    PubMed Central

    Wang, Hongwei; Zhou, Yue; Liu, Jun; Han, Jianda; Xiang, Liangbi

    2015-01-01

    Background: There is much more radiation exposure to the surgeons during minimally invasive pedicle screws placement. In order to ease the surgeon's hand-eye coordination and to reduce the iatrogenic radiation injury to the surgeons, a robot assisted percutaneous pedicle screw placement is useful. This study assesses the feasibility and clinical value of robot assisted navigated drilling for pedicle screw placement and the results thus achieved formed the basis for the development of a new robot for pedicle screw fixation surgery. Materials and Methods: Preoperative computed tomography (CT) of eight bovine lumbar spines (L1–L5) in axial plane were captured for each vertebra, the entry points and trajectories of the screws were preoperatively planned. On the basis of preoperative CT scans and intraoperative fluoroscopy, we aligned the robot drill to the desired entry point and trajectory, as dictated by the surgeon's preoperative plan. Eight bovine lumbar spines were inserted 80 K-wires using the spine robot system. The time for system registration and pedicle drilling, fluoroscopy times were measured and recorded. Postoperative CT scans were used to assess the position of the K-wires. Results: Assisted by spine robot system, the average time for system registration was (343.4 ± 18.4) s, the average time for procedure of drilling one pedicle screw trajectory was (89.5 ± 6.1) s, times of fluoroscopy for drilling one pedicle screw were (2.9 ± 0.8) times. Overall, 12 (15.0%) of the 80 K-wires violated the pedicle wall. Four screws (5.0%) were medial to the pedicle and 8 (10.5%) were lateral. The number of K-wires wholly within the pedicle were 68 (85%). Conclusions: The preliminary study supports the view that computer assisted pedicle screw fixation using spinal robot is feasible and the robot can decrease the intraoperative fluoroscopy time during the minimally invasive pedicle screw fixation surgery. As spine robotic surgery is still in its infancy, further

  10. Effect of the pilot hole preparation on the anchorage of pedicle screws

    PubMed Central

    Abrahão, Gustavo Silva; Rosa, Rodrigo César; Okubo, Rodrigo; Shimano, Antônio Carlos

    2012-01-01

    Objective We evaluated the influence of the diameter and the preparation of the pilot hole on the resistance to the pulling out and the strength when inserting pedicle screws with conical internal diameter. Methods Mechanical experiments were performed with pedicle conical screws of 4.2 mm and 5.2 mm diameter. They were inserted in the vertebral pedicles of swine. The hole was manufactured with a drill and probes with different diameters. Results While testing the 4.2 mm screw, the perforation of holes with measure equal or inferior to the lesser internal diameter of the screw increased the torque and the resistance to pull-out strength. Perforations with different instruments have presented similar results. Perforations with probes allowed the holes manufactured with dimensions superior to the lesser internal diameter of the screw to show similar resistance to that of the perforations with dimensions equal to the lesser internal diameter of the implant, made with probes and drills. Conclusion For 4.2 mm screws, the diameter and the preparation of the hole influence the torque and the resistance. For 5.2 mm screws, there is only influence on the insertion torque. There is no correlation between pulling out strength and insertion torque. Level of Evidence II, Therapeutic Studies - Investigating the Results of Treatment. PMID:24453617

  11. Pedicle screw placement in the thoracic spine: a comparison study of computer-assisted navigation and conventional techniques.

    PubMed

    Han, Wu; Gao, Zhong-li; Wang, Jin-cheng; Li, Ying-pu; Peng, Xia; Rui, Jiang; Jun, Wei

    2010-08-11

    The technique of computer-assisted pedicle screw installation and its clinical benefit as compared with conventional pedicle screw installation was evaluated. Twenty-two patients had thoracic screw insertion under 3-dimentional computer-assisted navigation (92 screws) and 20 patients under conventional fluoroscopic control (84 screws). The 2 groups were compared for accuracy of screw placement, screw insertion time by postoperative thin-cut computed tomography scans, and statistical analysis. The cortical perforations were graded by 2-mm increments. In the computer group, 88 (95.65%) were grade I (good), 4 (4.35%) were grade II (<2 mm), and 0 were grade III (>2 mm) violations. There were 4 cortical violations (3.57%). In the conventional group, there were 14 cortical violations (16.67%), 70 (83.33%) were grade I (good), 11 (13.1%) were grade II (<2 mm), and 3 (3.57%) were grade III (>2 mm) violations (P<.001). The number (19.57%) of upper thoracic pedicle screws (T1-T4) inserted under 3-dimensional computer-assisted navigation was significantly higher than that (3.57%) by conventional fluoroscopic control (P<.001). Average screw insertion time in the conventional group was more than in the computer group (P<.001). Three-dimensional computer-assisted navigation pedicle screw placement can increase accuracy, reduce surgical time, and be performed safely and effectively at all levels of the thoracic spine, particularly the upper thoracic spine.

  12. Accuracy and safety of pedicle screw placement in neuromuscular scoliosis with free-hand technique.

    PubMed

    Modi, Hitesh N; Suh, Seung Woo; Fernandez, Harry; Yang, Jae Hyuk; Song, Hae-Ryong

    2008-12-01

    It is a retrospective analytic study of 1,009 transpedicular screws (689 thoracic and 320 lumbosacral), inserted with free-hand technique in neuromuscular scoliosis using postoperative CT scan. The aim of paper was to determine the accuracy and safety of transpedicular screw placement with free-hand technique in neuromuscular scoliosis and to compare the accuracy at different levels in such population. All studies regarding accuracy and safety of pedicle screw in scoliosis represent idiopathic scoliosis using various techniques such as free-hand, navigation, image intensifier, etc., for screw insertion. Anatomies of vertebrae and pedicle are distorted in scoliosis, hence accurate and safe placement of pedicle screw is prerequisite for surgery. Between 2004 and 2006, 37 consecutive patients, average age 20 years (9-44 years), of neuromuscular scoliosis were operated with posterior pedicle screw fixation using free-hand technique. Accuracy of pedicle screws was studied on postoperative CT scan. Placement up to 2 mm medial side and 4 mm lateral side was considered within-safe zone. Of the 1,009 screws, 273 screws were displaced medially, laterally or on the anterior side showing that 73% screws (68% in thoracic and 82.5% in lumbar spine) were accurately placed within pedicle. Considering the safe zone, 93.3% (942/1009, 92.4% in thoracic and 95.3% in lumbar spine) of the screws were within the safe zone. Comparing accuracy according to severity of curve, accuracy was 75% in group 1 (curve <90 degrees ) and 69% in group 2 (curve >90 degrees) with a safety of 94.8 and 91.2%, respectively (P = 0.35). Comparing the accuracy at different thoracic levels, it showed 67, 64 and 72% accuracy in upper, middle and lower thoracic levels with safety of 96.6, 89.2 and 93.1%, respectively, exhibiting no statistical significant difference (P = 0.17). Pedicle screw placement in neuromuscular scoliosis with free-hand technique is accurate and safe as other conditions.

  13. Plan to procedure: combining 3D templating with rapid prototyping to enhance pedicle screw placement

    NASA Astrophysics Data System (ADS)

    Augustine, Kurt E.; Stans, Anthony A.; Morris, Jonathan M.; Huddleston, Paul M.; Matsumoto, Jane M.; Holmes, David R., III; Robb, Richard A.

    2010-02-01

    Spinal fusion procedures involving the implantation of pedicle screws have steadily increased over the past decade because of demonstrated improvement in biomechanical stability of the spine. However, current methods of spinal fusion carries a risk of serious vascular, visceral, and neurological injury caused by inaccurate placement or inappropriately sized instrumentation, which may lead to patient paralysis or even fatality. 3D spine templating software developed by the Biomedical Imaging Resource (BIR) at Mayo Clinic allows the surgeon to virtually place pedicle screws using pre-operative 3D CT image data. With the template plan incorporated, a patient-specific 3D anatomic model is produced using a commercial rapid prototyping system. The pre-surgical plan and the patient-specific model then are used in the procedure room to provide real-time visualization and quantitative guidance for accurate placement of each pedicle screw, significantly reducing risk of injury. A pilot study was conducted at Mayo Clinic by the Department of Radiology, the Department of Orthopedics, and the BIR, involving seven complicated pediatric spine cases. In each case, pre-operative 3D templating was carried out and patient specific models were generated. The plans and the models were used intra-operatively, providing precise pedicle screw starting points and trajectories. Postoperative assessment by the surgeon confirmed all seven operations were successful. Results from the study suggest that patient-specific, 3D anatomic models successfully acquired from 3D templating tools are valuable for planning and conducting pedicle screw insertion procedures.

  14. Three-dimensional Fluoroscopy-based Navigation for the Pedicle Screw Placement in Patients with Primary Invasive Spinal Tumors

    PubMed Central

    Jin, Bo; Su, Yi-Bing; Zhao, Ji-Zong

    2016-01-01

    Background: Although pedicle screw placement (PSP) is a well-established technique for spine surgery, the treatment of patients with primary invasive spinal tumor (PIST) has high surgical risks secondary to destroyed pedicles. Intraoperative three-dimensional fluoroscopy-based navigation (ITFN) system permits safe and accurate instrumentation of the spine with the advantage of obtaining intraoperative real-time three-dimensional images and automatic registration. The aim of this study is to evaluate the feasibility and accuracy of PSP using ITFN system for patients afflicted with PIST in the thoracic spine. Methods: Fifty-one patients diagnosed with PISTs were retrospectively analyzed, and 157 pedicles screws were implanted in 23 patients using the free-hand technique (free-hand group) and 197 pedicle screws were implanted in 28 patients using the ITFN system (ITFN group). Modified classification of Gertzbein and Robbins was used to evaluate the accuracy of PSP, and McCormick classification was applied for assessment of neurological function. Demographic data and factors affecting accuracy of screw insertion were compared using independent t-test while comparison of accuracy of screw insertion between the two groups was analyzed with Chi-square test. Results: Of 51 patients, 39 demonstrated improved neurological status and the other 12 patients reported that symptoms remained the same. In the free-hand group, 145 screws (92.4%) were Grade I, 9 screws (5.7%) were Grade II, and 3 screws (1.9%) were Grade III. In the ITFN group, 192 screws (97.4%) were Grade I, 5 screws (2.6%) were Grade II, and no Grade III screw was detected. Statistical analysis showed that the accuracies of pedicle screws in the two groups are significantly different (χ2 = 4.981, P = 0.026). Conclusions: The treatments of PISTs include total tumor resection and reconstruction of spine stability. The ITFN system provides a high accuracy of pedicle screw placement. PMID:27779161

  15. The use of pedicle-screw internal fixation for the operative treatment of spinal disorders.

    PubMed

    Gaines, R W

    2000-10-01

    Pedicle screws have dramatically improved the outcomes of spinal reconstruction requiring spinal fusion. Short-segment surgical treatments based on the use of pedicle screws for the treatment of neoplastic, developmental, congenital, traumatic, and degenerative conditions have been proved to be practical, safe, and effective. The Funnel Technique provides a straightforward, direct, and inexpensive way to very safely apply pedicle screws in the cervical, thoracic, or lumbar spine. Carefully applied pedicle-screw fixation does not produce severe or frequent complications. Pedicle-screw fixation can be effectively and safely used wherever a vertebral pedicle can accommodate a pedicle screw--that is, in the cervical, thoracic, or lumbar spine. Training in pedicle-screw application should be standard in orthopaedic training programs since pedicle-screw fixation represents the so-called gold standard of spinal internal fixation.

  16. The usefulness of electrical stimulation for assessing pedicle screw placements.

    PubMed

    Toleikis, J R; Skelly, J P; Carlvin, A O; Toleikis, S C; Bernard, T N; Burkus, J K; Burr, M E; Dorchak, J D; Goldman, M S; Walsh, T R

    2000-08-01

    The purpose of this study was to further establish the efficacy of pedicle screw stimulation as a monitoring technique to avoid nerve root injury during screw placement. The study population consisted of 662 patients in whom 3,409 pedicle screws were placed and tested by electrical stimulation. If stimulation resulted in a myogenic response at a stimulation intensity of 10 mA or less, the placement of the screw was inspected. Inspection was necessary for 3.9% of the screw placements in 15.4% of the study population. None of the patients in the study experienced any new postoperative neurologic deficits. These findings provide guidelines for the interpretation of stimulation data and support the use of this technique as an easy, inexpensive, and quick method to reliably assess screw placements and protecting neurological function.

  17. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae

    PubMed Central

    Leichtle, C. I.; Rothstock, S.; Happel, J.; Walter, F.; Shiozawa, T.; Leichtle, U. G.

    2016-01-01

    Objectives Cement augmentation of pedicle screws could be used to improve screw stability, especially in osteoporotic vertebrae. However, little is known concerning the influence of different screw types and amount of cement applied. Therefore, the aim of this biomechanical in vitro study was to evaluate the effect of cement augmentation on the screw pull-out force in osteoporotic vertebrae, comparing different pedicle screws (solid and fenestrated) and cement volumes (0 mL, 1 mL or 3 mL). Materials and Methods A total of 54 osteoporotic human cadaver thoracic and lumbar vertebrae were instrumented with pedicle screws (uncemented, solid cemented or fenestrated cemented) and augmented with high-viscosity PMMA cement (0 mL, 1 mL or 3 mL). The insertion torque and bone mineral density were determined. Radiographs and CT scans were undertaken to evaluate cement distribution and cement leakage. Pull-out testing was performed with a material testing machine to measure failure load and stiffness. The paired t-test was used to compare the two screws within each vertebra. Results Mean failure load was significantly greater for fenestrated cemented screws (+622 N; p ⩽ 0.001) and solid cemented screws (+460 N; p ⩽ 0.001) than for uncemented screws. There was no significant difference between the solid and fenestrated cemented screws (p = 0.5). In the lower thoracic vertebrae, 1 mL cement was enough to significantly increase failure load, while 3 mL led to further significant improvement in the upper thoracic, lower thoracic and lumbar regions. Conclusion Conventional, solid pedicle screws augmented with high-viscosity cement provided comparable screw stability in pull-out testing to that of sophisticated and more expensive fenestrated screws. In terms of cement volume, we recommend the use of at least 1 mL in the thoracic and 3 mL in the lumbar spine. Cite this article: C. I. Leichtle, A. Lorenz, S. Rothstock, J. Happel, F. Walter, T. Shiozawa, U. G. Leichtle. Pull

  18. A Modified Personalized Image-Based Drill Guide Template for Atlantoaxial Pedicle Screw Placement: A Clinical Study

    PubMed Central

    Jiang, Lianghai; Dong, Liang; Tan, Mingsheng; Qi, Yingna; Yang, Feng; Yi, Ping; Tang, Xiangsheng

    2017-01-01

    Background Atlantoaxial posterior pedicle screw fixation has been widely used for treatment of atlantoaxial instability (AAI). However, precise and safe insertion of atlantoaxial pedicle screws remains challenging. This study presents a modified drill guide template based on a previous template for atlantoaxial pedicle screw placement. Material/Methods Our study included 54 patients (34 males and 20 females) with AAI. All the patients underwent posterior atlantoaxial pedicle screw fixation: 25 patients underwent surgery with the use of a modified drill guide template (template group) and 29 patients underwent surgery via the conventional method (conventional group). In the template group, a modified drill guide template was designed for each patient. The modified drill guide template and intraoperative fluoroscopy were used for surgery in the template group, while only intraoperative fluoroscopy was used in the conventional group. Results Of the 54 patients, 52 (96.3%) completed the follow-up for more than 12 months. The template group had significantly lower intraoperative fluoroscopy frequency (p<0.001) and higher accuracy of screw insertion (p=0.045) than the conventional group. There were no significant differences in surgical duration, intraoperative blood loss, or improvement of neurological function between the 2 groups (p>0.05). Conclusions Based on the results of this study, it is feasible to use the modified drill guide template for atlantoaxial pedicle screw placement. Using the template can significantly lower the screw malposition rate and the frequency of intraoperative fluoroscopy. PMID:28301445

  19. Accuracy of Free Hand Pedicle Screw Installation in the Thoracic and Lumbar Spine by a Young Surgeon: An Analysis of the First Consecutive 306 Screws Using Computed Tomography

    PubMed Central

    Lee, Chang-Hyun; Kim, Yongjung J; Kim, Ki-Jeong; Jahng, Tae-Ahn; Kim, Hyun-Jib

    2014-01-01

    Study Design A retrospective cross-sectional study. Purpose The purpose of this study is to evaluate the accuracy and safety of free-hand pedicle screw insertion performed by a young surgeon. Overview of Literature Few articles exist regarding the safety of the free-hand technique without inspection by an experienced spine surgeon. Methods The index surgeon has performed spinal surgery for 2 years by himself. He performed fluoroscopy-assisted pedicle screw installation for his first year. Since then, he has used the free-hand technique. We retrospectively reviewed the records of all consecutive patients undergoing pedicle screw installation using the free-hand technique without fluoroscopy in the thoracic or lumbar spine by the index surgeon. Incidence and extent of cortical breach by misplaced pedicle screw was determined by a review of postoperative computed tomography (CT) images. Results A total of 36 patients received 306 free-hand placed pedicle screws in the thoracic or lumbar spine. A total of 12 screws (3.9%) were identified as breaching the pedicle in 9 patients. Upper thoracic spine was the most frequent location of screw breach (10.8%). Lateral breach (2.3%) was more frequent than any other direction. Screw breach on the right side (9 patients) was more common than that on the left side (3 patients) (p<0.01). Conclusions An analysis by CT scan shows that young spine surgeons who have trained under the supervision of an experienced surgeon can safely place free-hand pedicle screws with an acceptable breach rate through repetitive confirmatory steps. PMID:24967036

  20. Virtual estimates of fastening strength for pedicle screw implantation procedures

    NASA Astrophysics Data System (ADS)

    Linte, Cristian A.; Camp, Jon J.; Augustine, Kurt E.; Huddleston, Paul M.; Robb, Richard A.; Holmes, David R.

    2014-03-01

    Traditional 2D images provide limited use for accurate planning of spine interventions, mainly due to the complex 3D anatomy of the spine and close proximity of nerve bundles and vascular structures that must be avoided during the procedure. Our previously developed clinician-friendly platform for spine surgery planning takes advantage of 3D pre-operative images, to enable oblique reformatting and 3D rendering of individual or multiple vertebrae, interactive templating, and placement of virtual pedicle implants. Here we extend the capabilities of the planning platform and demonstrate how the virtual templating approach not only assists with the selection of the optimal implant size and trajectory, but can also be augmented to provide surrogate estimates of the fastening strength of the implanted pedicle screws based on implant dimension and bone mineral density of the displaced bone substrate. According to the failure theories, each screw withstands a maximum holding power that is directly proportional to the screw diameter (D), the length of the in-bone segm,ent of the screw (L), and the density (i.e., bone mineral density) of the pedicle body. In this application, voxel intensity is used as a surrogate measure of the bone mineral density (BMD) of the pedicle body segment displaced by the screw. We conducted an initial assessment of the developed platform using retrospective pre- and post-operative clinical 3D CT data from four patients who underwent spine surgery, consisting of a total of 26 pedicle screws implanted in the lumbar spine. The Fastening Strength of the planned implants was directly assessed by estimating the intensity - area product across the pedicle volume displaced by the virtually implanted screw. For post-operative assessment, each vertebra was registered to its homologous counterpart in the pre-operative image using an intensity-based rigid registration followed by manual adjustment. Following registration, the Fastening Strength was computed

  1. Intraoperative stimulation of pedicle screws: a new method for verification of screw placement.

    PubMed

    Young, W F; Morledge, D E; Martin, W; Park, K B

    1995-12-01

    Pedicular fixation of the lumbosacral spine has become a popular procedure for improving fusion rates. Even in experienced hands, it can be associated with a significant rate of screw malpositioning and potential nerve root injury. In this report, we describe a technique for improving screw localization utilizing evoked electromyography responses from direct stimulation of pedicle instrumentation.

  2. Pedicle screw fixation combined with intermediate screw at the fracture level for treatment of thoracolumbar fractures

    PubMed Central

    Li, Kunpeng; Zhang, Wen; Liu, Dan; Xu, Hui; Geng, Wei; Luo, Dawei; Ma, Jinzhu

    2016-01-01

    Abstract Background: Use of a pedicle screw at the level of fracture, also known as an intermediate screw, has been shown to improve clinical results in managing thoracolumbar(TL) fractures, but there is a paucity of powerful evidence to support the claim. The aim of this study was to compare outcomes between pedicle screw fixation combined with intermediate screw at the fracture level and conventional pedicle screw fixation (one level above and one level below the fracture level) for thoracolumbar (TL) fractures. Methods: A meta-analysis of cohort studies was conducted between pedicle screw fixation combined with intermediate screw at the fracture level (combined screw group) and conventional pedicle screw fixation (conventional group) for the treatment of TL fractures from their inception to December 2015. An extensive search of studies was performed in PubMed, Medline, Embase, and the Cochrane library. The following outcome measures were extracted: visual analogue scale (VAS), operation time and intraoperative blood loss, Cobb angle and anterior vertebral height (AVH), and complications. Data analysis was conducted with RevMan 5.3.5. Results: From 10 relevant studies identified, 283 patients undergoing pedicle screw fixation combined with intermediate screw at the fracture level were compared with 285 conventional pedicle screw procedures. The pooled analysis showed that there was statistically significant difference in terms of postoperative Cobb angle (95% confidence interval (CI), −3.00, −0.75; P = 0.001) and AVH (95% CI, 0.04, 12.23; P = 0.05), correction loss (Cobb angle: P < 0.0001; AVH: P < 0.0001) and implant failure rate (95% CI, 0.06, 0.62; P = 0.006), and blood loss (W 95% CI, 2.22, 23.60; P = 0.02) between 2 groups. But in terms of other complications, there were no differences between 2 groups (95% CI, 0.23, 2.04; P = 0.50). No difference was found in operation time (95% CI, −5.36, 14.67; P = 0.36) and VAS scores (95% CI, −0.44, 0

  3. Pedicle screw placement accuracy of bone-mounted miniature robot system.

    PubMed

    Tsai, Tai-Hsin; Tzou, Rong-Dar; Su, Yu-Feng; Wu, Chieh-Hsin; Tsai, Cheng-Yu; Lin, Chih-Lung

    2017-01-01

    This article describes factors affecting the accuracy of transpedicle screw placements performed with the Renaissance robot-guided system and reviews the relevant literature. Between January 2013 and January 2015, Renaissance robot-guided spinal surgery was performed in 125 patients at Kaohsiung Medical University Hospital in Kaohsiung, Taiwan. The surgeries included 662 transpedicle screw implants and 49 Kirschner wire (K-wire) reimplants performed by intraoperative repositioning. The lead author evaluated the accuracy of all K-wire insertions and classified their accuracy into 3 categories relative to the preoperative plan for transpedicle screw placement. For cases in which screws required repositioning after the registration step, factors affecting pedicle screw placement were determined according to the consensus of 3 experienced spinal surgeons. According to the scheme developed by Kuo et al (PLoS One 2016;11:e0153235), the K-wire placement accuracies before and after repositioning were respectively classified as follows: 76.1% and 77.6% in type I; 12.2% and 17.7% in type IIa; 4.3% and 4.5% in type IIb; 6.4% and 0% in type IIIa; and 1% and 1% in type IIIb. The percentage of screws requiring repositioning due to drilling error was 85.7% (42/49). Comparisons of preoperative and postoperative function showed significantly improved accuracy. This study showed that inaccurate pedicle screw placement mainly results from errors in preoperative planning, mounting, registration, drilling, and robot assembly. Pedicle screw placement using a bone-mounted miniature robot system requires meticulous preoperative planning to minimize these errors.

  4. Pedicle screw placement accuracy of bone-mounted miniature robot system

    PubMed Central

    Tsai, Tai-Hsin; Tzou, Rong-Dar; Su, Yu-Feng; Wu, Chieh-Hsin; Tsai, Cheng-Yu; Lin, Chih-Lung

    2017-01-01

    Abstract This article describes factors affecting the accuracy of transpedicle screw placements performed with the Renaissance robot-guided system and reviews the relevant literature. Between January 2013 and January 2015, Renaissance robot-guided spinal surgery was performed in 125 patients at Kaohsiung Medical University Hospital in Kaohsiung, Taiwan. The surgeries included 662 transpedicle screw implants and 49 Kirschner wire (K-wire) reimplants performed by intraoperative repositioning. The lead author evaluated the accuracy of all K-wire insertions and classified their accuracy into 3 categories relative to the preoperative plan for transpedicle screw placement. For cases in which screws required repositioning after the registration step, factors affecting pedicle screw placement were determined according to the consensus of 3 experienced spinal surgeons. According to the scheme developed by Kuo et al (PLoS One 2016;11:e0153235), the K-wire placement accuracies before and after repositioning were respectively classified as follows: 76.1% and 77.6% in type I; 12.2% and 17.7% in type IIa; 4.3% and 4.5% in type IIb; 6.4% and 0% in type IIIa; and 1% and 1% in type IIIb. The percentage of screws requiring repositioning due to drilling error was 85.7% (42/49). Comparisons of preoperative and postoperative function showed significantly improved accuracy. This study showed that inaccurate pedicle screw placement mainly results from errors in preoperative planning, mounting, registration, drilling, and robot assembly. Pedicle screw placement using a bone-mounted miniature robot system requires meticulous preoperative planning to minimize these errors. PMID:28099339

  5. Prediction of Deformity Correction by Pedicle Screw Instrumentation in Thoracolumbar Scoliosis Surgery

    NASA Astrophysics Data System (ADS)

    Kiriyama, Yoshimori; Yamazaki, Nobutoshi; Nagura, Takeo; Matsumoto, Morio; Chiba, Kazuhiro; Toyama, Yoshiaki

    In segmental pedicle screw instrumentation, the relationship between the combinations of pedicle screw placements and the degree of deformity correction was investigated with a three-dimensional rigid body and spring model. The virtual thoracolumbar scoliosis (Cobb’s angle of 47 deg.) was corrected using six different combinations of pedicle-screw placements. As a result, better correction in the axial rotation was obtained with the pedicle screws placed at or close to the apical vertebra than with the screws placed close to the end vertebrae, while the correction in the frontal plane was better with the screws close to the end vertebrae than with those close to the apical vertebra. Additionally, two screws placed in the convex side above and below the apical vertebra provided better correction than two screws placed in the concave side. Effective deformity corrections of scoliosis were obtained with the proper combinations of pedicle screw placements.

  6. A Biomechanical Comparison of Expansive Pedicle Screws for Severe Osteoporosis: The Effects of Screw Design and Cement Augmentation

    PubMed Central

    Tai, Ching-Lung; Tsai, Tsung-Ting; Lai, Po-Liang; Chen, Yi-Lu; Liu, Mu-Yi; Chen, Lih-Huei

    2015-01-01

    Expansive pedicle screws significantly improve fixation strength in osteoporotic spines. However, the previous literature does not adequately address the effects of the number of lengthwise slits and the extent of screw expansion on the strength of the bone/screw interface when expansive screws are used with or without cement augmentation. Herein, four designs for expansive pedicle screws with different numbers of lengthwise slits and different screw expansion levels were evaluated. Synthetic bones simulating severe osteoporosis were used to provide a comparative platform for each screw design. The prepared specimens were then tested for axial pullout failure. Regardless of screw design, screws with cement augmentation demonstrated significantly higher pullout strength than pedicle screws without cement augmentation (p < 0.001). For screws without cement augmentation, solid screws exhibited the lowest pullout strength compared to the four expansive groups (p < 0.01). No significant differences in pullout strength were observed between the expansive screws with different designs (p > 0.05). Taken together, our results show that pedicle screws combined with cement augmentation may greatly increase screw fixation regardless of screws with or without expansion. An increase in both the number of slits and the extent of screw expansion had little impact on the screw-anchoring strength. Cement augmentation is the most influential factor for improving screw pullout strength. PMID:26720724

  7. Recording triggered EMG thresholds from axillary chest wall electrodes: a new refined technique for accurate upper thoracic (T2-T6) pedicle screw placement.

    PubMed

    Regidor, Ignacio; de Blas, Gema; Barrios, Carlos; Burgos, Jesús; Montes, Elena; García-Urquiza, Sergio; Hevia, Edurado

    2011-10-01

    This study was aimed at evaluating the sensitivity and safety of a new technique to record triggered EMG thresholds from axillary chest wall electrodes when inserting pedicle screws in the upper thoracic spine (T2-T6). A total of 248 (36.6%) of a total of 677 thoracic screws were placed at the T2-T6 levels in 92 patients with adolescent idiopathic scoliosis. A single electrode placed at the axillary midline was able to record potentials during surgery from all T2-T6 myotomes at each side. Eleven screws were removed during surgery because of malposition according to intraoperative fluoroscopic views. Screw position was evaluated after surgery in the remaining 237 screws using a CT scan. Malposition was detected in 35 pedicle screws (14.7%). Pedicle medial cortex was breached in 24 (10.1%). Six screws (2.5%) were located inside the spinal canal. Mean EMG threshold was 24.44 ± 11.30 mA in well-positioned screws, 17.98 ± 8.24 mA (p < 0.01) in screws violating the pedicle medial cortex, and 10.38 ± 3.33 mA (p < 0.005) in screws located inside the spinal canal. Below a threshold of 12 mA, 33.4% of the screws (10/30) were malpositioned. Furthermore, 36% of the pedicle screws with t-EMG stimulation thresholds within the range 6-12 mA were malpositioned. In conclusion, assessment of upper thoracic pedicle screw placement by recording tEMG at a single axillary electrode was highly reliable. Thresholds below 12 mA should alert surgeons to suspect screw malposition. This technique simplifies tEMG potential recording to facilitate safe placement of pedicle screws at upper thoracic levels.

  8. Control of Pedicle Screw Placement with an Electrical Conductivity Measurement Device: Initial Evaluation in the Thoracic and Lumbar Spine

    PubMed Central

    Schomacher, Markus

    2016-01-01

    Aim. Transpedicular screw fixation is widely used in spinal surgery. But the insertion of pedicle screws can sometimes be challenging because of the variability in pedicle size and the proximity of nerve roots. Methods. We detected intraoperatively the sensitivity for iatrogenic pedicel perforation with a hand-held electronic conductivity measurement device (ECD) that measures electrical conductivity of tissue-medium surrounding the instrument tip. ECD was used to guide the placement of 84 pedicle screws in 15 patients undergoing surgery for tumor or degenerative spinal disease at various spinal levels from T8 to L5. Additionally a CT-scan controlled screw positioning postoperatively. Results. The placement was “correct” (no mediocaudal pedicle wall penetration) for 78 of 84 (92,8%) screws, “suboptimal but acceptable” (0–2 mm penetration) for 4 of 84 (4,8%) screws, and “misplaced” (penetration > 2 mm) for 2 of 84 (2,4%) screws. Conclusion. Although this study was not designed to compare electronic conductivity technique to other guidance methods, such as fluoroscopy or navigation, a convincing “proof of concept” for ECD use in spinal instrumentation could be demonstrated. Advantages include easy handling without time-consuming setup and reduced X-ray exposure. However, further investigations are necessary to evaluate i.a. the economic aspects for this single-use developed instrument. PMID:27699203

  9. A comparative study of pedicle screw fixation in dorsolumbar spine by freehand versus image-assisted technique: A cadaveric study

    PubMed Central

    Agarwal, Archit; Chauhan, Vijendra; Singh, Deepa; Shailendra, Raghuvanshi; Maheshwari, Rajesh; Juyal, Anil

    2016-01-01

    Background: New and expensive technology such as three-dimensional computer assisted surgery is being used for pedicle screw fixation in dorsolumbar spine. Their availability, expenses and amount of radiation exposure are issues in a developing country. On the contrary, freehand technique of pedicle screw placement utilizes anatomic landmarks and tactile palpation without fluoroscopy or navigation to place pedicle screws. The purpose of this study was to analyze and compare the accuracy of freehand and image-assisted technique to place pedicle screws in the dorsolumbar spine of cadavers by an experienced surgeon and a resident. Evaluation was done using dissection of pedicle and computed tomography (CT) imaging. Materials and Methods: Ten cadaveric dorsolumbar spines were exposed by a posterior approach. Titanium pedicle screws were inserted from D5 to L5 vertebrae by freehand and image-assisted technique on either side by an experienced surgeon and a resident. CT was obtained. A blinded radiologist reviewed the imaging. The spines were then dissected to do a macroscopic examination. Screws, having evidence of cortical perforation of more than 2 mm on CT, were considered to be a significant breach. Results: A total of 260 pedicle screws were placed. The surgeon and the resident placed 130 screws each. Out of 130 screws, both of them placed 65 screws each by freehand and image- assisted technique each. The resident had a rate of 7.69% significant medial and 10.76% significant lateral breach with freehand technique while with image-assisted had a rate of 3.07% significant medial and 9.23% significant lateral breach. The expert surgeon had a rate of 6.15% significant medial and 1.53% significant lateral breach with freehand technique while with image-assisted had a rate of 3.07% significant medial and 6.15% significant lateral breach on CT evaluation. Conclusion: Freehand technique is as good as the image-assisted technique. Under appropriate supervision, residents

  10. Thoracic Aortic Stent-Graft Placement for Safe Removal of a Malpositioned Pedicle Screw

    SciTech Connect

    Hu Hongtao; Shin, Ji Hoon Hwang, Jae-Yeon; Cho, Young Jun; Ko, Gi-Young; Yoon, Hyun-Ki

    2010-10-15

    We describe a case of percutaneous placement of a thoracic aortic stent-graft for safe removal of a malpositioned pedicle screw in a 52-year-old man. The patient had undergone posterior thoracic spinal instrumentation for pyogenic spondylitis and spinal deformity 8 months previously. Follow-up CT images showed a malpositioned pedicle screw which was abutting the thoracic aorta at the T5 level. After percutaneous stent-graft placement, the malpositioned pedicle screw was safely and successfully removed.

  11. Insertion Profiles of 4 Headless Compression Screws

    PubMed Central

    Hart, Adam; Harvey, Edward J.; Lefebvre, Louis-Philippe; Barthelat, Francois; Rabiei, Reza; Martineau, Paul A.

    2013-01-01

    Purpose In practice, the surgeon must rely on screw position (insertion depth) and tactile feedback from the screwdriver (insertion torque) to gauge compression. In this study, we identified the relationship between interfragmentary compression and these 2 factors. Methods The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple implants were tested using a polyurethane foam scaphoid model. A specialized testing jig simultaneously measured compression force, insertion torque, and insertion depth at half-screw-turn intervals until failure occurred. Results The peak compression occurs at an insertion depth of −3.1 mm, −2.8 mm, 0.9 mm, and 1.5 mm for the Acutrak Mini, Acutrak Standard, Herbert-Whipple, and Synthes screws respectively (insertion depth is positive when the screw is proud above the bone and negative when buried). The compression and insertion torque at a depth of −2 mm were found to be 113 ± 18 N and 0.348 ± 0.052 Nm for the Acutrak Standard, 104 ± 15 N and 0.175 ± 0.008 Nm for the Acutrak Mini, 78 ± 9 N and 0.245 ± 0.006 Nm for the Herbert-Whipple, and 67 ± 2N, 0.233 ± 0.010 Nm for the Synthes headless compression screws. Conclusions All 4 screws generated a sizable amount of compression (> 60 N) over a wide range of insertion depths. The compression at the commonly recommended insertion depth of −2 mm was not significantly different between screws; thus, implant selection should not be based on compression profile alone. Conically shaped screws (Acutrak) generated their peak compression when they were fully buried in the foam whereas the shanked screws (Synthes and Herbert-Whipple) reached peak compression before they were fully inserted. Because insertion torque correlated poorly with compression, surgeons should avoid using tactile judgment of torque as a proxy for compression. Clinical relevance Knowledge of the insertion profile may improve our understanding of the implants, provide a better basis for comparing screws

  12. Computer navigation versus fluoroscopy-guided navigation for thoracic pedicle screw placement: a meta-analysis.

    PubMed

    Meng, Xiao-Tong; Guan, Xiao-Fei; Zhang, Hai-Long; He, Shi-Sheng

    2016-07-01

    Although application of intraoperative computer navigation technique had been integrated into placement of pedicle screws (PSs) in thoracic fusion for years, its security and practicability remain controversial. The aim of this study is to evaluate the accuracy, the operative time consumption, the amount of intraoperative blood loss, time of pedicle insertion and the incidence of complications of thoracic pedicle screw placement in patients with thoracic diseases such as scoliosis and kyphosis. Pubmed, Web of Knowledge, and Google scholar were searched to identify comparative studies of thoracic pedicle screw placement between intraoperative computer navigation and fluoroscopy-guided navigation. Outcomes of malposition rate, operative time consumption, insertion time, intraoperative blood loss, and the incidence of complications are evaluated. Fourteen articles including 1723 patients and 9019 PSs were identified matching inclusion criteria. The malposition rate was lower (RR: 0.33, 95 % CI: 0.28-0.38, P < 0.01) in computer navigation group than that in fluoroscopy-guided navigation group; the operative time was significantly longer [weighted mean difference (WMD) = 23.66, 95 % CI: 14.74-32.57, P < 0.01] in computer navigation group than that in fluoroscopy-guided navigation group. The time of insertion was shorter (WMD = -1.88, 95 % CI: -2.25- -1.52, P < 0.01) in computer navigation group than that in fluoroscopy-guided navigation group. The incidence of complications was lower (RR = 0. 23, 95 % CI: 0.12-0.46, P < 0.01) in computer navigation group than that in the other group. The intraoperative blood loss was fewer (WMD = -167.49, 95 % CI: -266.39- -68.58, P < 0.01) in computer navigation group than that in the other. In conclusion, the meta-analysis of thoracic pedicle screw placement studies clearly demonstrated lower malposition rate, less intraoperative blood loss, and fewer complications when using computer

  13. Biomechanical effects of pedicle screw fixation on adjacent segments.

    PubMed

    Kyaw, Thein Aung; Wang, Zhuo; Sakakibara, Toshihiko; Yoshikawa, Takamasa; Inaba, Tadashi; Kasai, Yuichi

    2014-07-01

    Various biomechanical investigations have attempted to clarify the aetiology of adjacent segment disease (ASD). However, no biomechanical study has examined in detail the deformation behaviour of the adjacent segments when both pure torque and an angular displacement load are applied to the vertebrae along multiple segments. The purpose of this study is to investigate the biomechanical effects of pedicle screw fixation on adjacent segments. Ten cadaveric lumbar spines (L2-L5) of boars were used. Control and fusion models were prepared by disc damage and pedicle screw fixation of each specimen, and then, bending and rotation tests were performed using a six-axis material tester. In the biomechanical tests regulated by an angular displacement load, the range of motion (ROM) of the cranial and caudal adjacent segments in antero-posterior flexion and lateral bending was increased by about 20 % (p < 0.05), and the maximal torque in the fusion model was about threefold (p < 0.05) that in the control model. And in axial rotation, the ROM of cranial and caudal adjacent segments was increased by about 100 % (p < 0.001), and the maximal torque was about sixfold (p < 0.01) that in the control model. The ROM of adjacent segments was significantly increased after pedicle screw fixation as assessed by biomechanical tests regulated by an angular displacement load, but not in those regulated by torque. We present the results of biomechanical tests regulated by torque and angular displacement and show that the maximum torque of the fusion model was larger than that of the control model in the biomechanical test regulated by an angular displacement load, suggesting that mechanical stress on the segments adjacent to the fused segment is large. We think that ASD arises after spinal fusion surgery as a mechanism to compensate for the ROM lost due to excessive fusion by pedicle screw fixation, so that a large torque may be applied to adjacent segments within a physiologically

  14. Accuracy of Percutaneous Lumbosacral Pedicle Screw Placement Using the Oblique Fluoroscopic View Based on Computed Tomography Evaluations

    PubMed Central

    Sato, Koji; Kanemura, Tokumi; Iwase, Toshiki; Togawa, Daisuke; Matsuyama, Yukihiro

    2016-01-01

    Study Design Retrospective. Purpose This study aims to investigate the accuracy of the oblique fluoroscopic view, based on preoperative computed tomography (CT) images for accurate placement of lumbosacral percutaneous pedicle screws (PPS). Overview of Literature Although PPS misplacement has been reported as one of the main complications in minimally invasive spine surgery, there is no comparative data on the misplacement rate among different fluoroscopic techniques, or comparing such techniques with open procedures. Methods We retrospectively selected 230 consecutive patients who underwent posterior spinal fusion with a pedicle screw construct for degenerative lumbar disease, and divided them into 3 groups, those who had undergone: minimally invasive percutaneous procedure using biplane (lateral and anterior-posterior views using a single C-arm) fluoroscope views (group M-1), minimally invasive percutaneous procedure using the oblique fluoroscopic view based on preoperative CT (group M-2), and conventional open procedure using a lateral fluoroscopic view (group O: controls). The relative position of the screw to the pedicle was graded for the pedicle breach as no breach, <2 mm, 2–4 mm, or >4 mm. Inaccuracy was calculated and assessed according to the spinal level, direction and neurological deficit. Inter-group radiation exposure was estimated using fluoroscopy time. Results Inaccuracy involved an incline toward L5, causing medial or lateral perforation of pedicles in group M-1, but it was distributed relatively equally throughout multiple levels in groups M-2 and controls. The mean fluoroscopy time/case ranged from 1.6 to 3.9 minutes. Conclusions Minimally invasive lumbosacral PPS placement using the conventional fluoroscopic technique carries an increased risk of inaccurate screw placement and resultant neurological deficits, compared with that of the open procedure. Inaccuracy tended to be distributed between medial and lateral perforations of the L5 pedicle

  15. Effect of Off-Axis Screw Insertion, Insertion Torque, and Plate Contouring on Locked Screw Strength

    PubMed Central

    Gallagher, Bethany; Silva, Matthew J.; Ricci, William M.

    2015-01-01

    Objectives This study quantifies the effects of insertion torque, off-axis screw angulation, and plate contouring on the strength of locking plate constructs. Methods Groups of locking screws (n = 6–11 screws) were inserted at 50%, 100%, 150%, and 200% of the manufacturer-recommended torque (3.2 Nm) into locking compression plates at various angles: orthogonal (control), 5-degree angle off-axis, and 10-degree angle off-axis. Screws were loaded to failure by a transverse force (parallel to the plate) either in the same (“+”) or opposite direction (“−”) of the initial screw angulation. Separately, locking plates were bent to 5 and 10-degree angles, with the bend apex at a screw hole. Locking screws inserted orthogonally into the apex hole at 100% torque were loaded to failure. Results Orthogonal insertion resulted in the highest average load to failure, 2577 ± 141 N (range, 2413–2778 N), whereas any off-axis insertion significantly weakened constructs (165–1285 N, at 100% torque) (P < 0.05). For “+” loading, torque beyond 100% did not increase strength, but 50% torque reduced screw strength (P < 0.05). Loading in the “−” direction consistently resulted in higher strengths than “+” loading (P < 0.05). Plate contouring of 5-degree angle did not significantly change screw strength compared with straight plates but contouring of 10-degree angle significantly reduced load to failure (P < 0.05). Conclusions To maximize the screw plate interface strength, locking screws should be inserted without cross-threading. The mechanical stability of locked screws is significantly compromised by loose insertion, off-axis insertion, or severe distortion of the locking mechanism. PMID:24343255

  16. Cortical bone trajectory screws placement via pedicle or pedicle rib unit in the pediatric thoracic spine (T9-T12): A 2-dimensional multiplanar reconstruction study using computed tomography.

    PubMed

    Xuan, Jun; Chen, Jian; He, Hui; Jin, Hai-Ming; Zhang, Di; Wu, Yao-Sen; Tian, Nai-Feng; Wang, Xiang-Yang

    2017-02-01

    Thoracic cortical bone trajectory (CBT) screw fixation can maximize the thread contact with cortical bone, and it is 53.8% higher than that of the traditional pedicle screws. Moreover, it can also enable less tissue dissection and retraction for reduced muscle disruption.Eighty pediatric patients are divided into 4 age groups and their thoracic vertebrae are analyzed on computed tomography (CT) images. The maximal screw length, maximal screw diameter, screw diameter, and the cephalad angle are measured. The statistical analysis is performed using the Student's t-test and Pearson's correlation analysis.Maximal screw length increases from T9 to T12 and there are significant differences between girls and boys at T9, T10, T11, and T12 in majority of groups (P < 0.05). The maximal screw diameter and screw diameter increase from T9 to T12. The maximal screw diameter ranges from 6.27 mm to 10.20 mm, whereas the screw diameter ranges from 3.87 mm to 6.75 mm. Meanwhile, the maximum cephalad angle is 23.06° and the minimum is 13.11°. No statistically significant differences in the cephalad angle are found at all levels.Our study establishes the feasibility of 4.5 to 5.5 mm CBT screws fixation via pedicle or pedicle rib unit in the pediatric thoracic spine. The entry point of the pediatric thoracic CBT screws is 6 o'clock orientation of the pedicle. Findings of our study also provide insights into the screw insertion angle and screw size decision.

  17. A new alternative to expandable pedicle screws: Expandable poly-ether-ether-ketone shell.

    PubMed

    Demir, Teyfik

    2015-05-01

    Screw pullout is a very common problem in the fixation of sacrum with pedicle screws. The principal cause of this problem is that the cyclic micro motions in the fixation of sacrum are higher than the other regions of the vertebrae that limit the osteo-integration between bone and screw. In addition to that, the bone quality is very poor at sacrum region. This study investigated a possible solution to the pullout problem without the expandable screws' handicaps. Newly designed poly-ether-ether-ketone expandable shell and classical pedicle screws were biomechanically compared. Torsion test, pullout tests, fatigue tests, flexion/extension moment test, axial gripping capacity tests and torsional gripping capacity tests were conducted in accordance with ASTM F543, F1798 and F1717. Standard polyurethane foam and calf vertebrae were used as embedding medium for pullout tests. Classical pedicle screw pullout load on polyurethane foam was 564.8 N compared to the failure load for calf vertebrae's 1264 N. Under the same test conditions, expandable poly-ether-ether-ketone shell system's pullout loads from polyurethane foam and calf vertebrae were 1196.3 and 1890 N, respectively. The pullout values for expandable poly-ether-ether-ketone shell were 33% and 53% higher than classical pedicle screw on polyurethane foam and calf vertebrae, respectively. The expandable poly-ether-ether-ketone shell exhibited endurance on its 90% of yield load. Contrary to poly-ether-ether-ketone shell, classical pedicle screw exhibited endurance on 70% of its yield load. Expandable poly-ether-ether-ketone shell exhibited much higher pullout performance than classical pedicle screw. Fatigue performance of expandable poly-ether-ether-ketone shell is also higher than classical pedicle screw due to damping the micro motion capacity of the poly-ether-ether-ketone. Expandable poly-ether-ether-ketone shell is a safe alternative to all other expandable pedicle screw systems on mechanical perspective.

  18. Unilateral Pedicle Screw Fixation with Bone Graft vs. Bilateral Pedicle Screw Fixation with Bone Graft or Cage: A Comparative Study

    PubMed Central

    Yang, Si-Dong; Chen, Qian; Ding, Wen-Yuan; Zhao, Jian-Qiang; Zhang, Ying-Ze; Shen, Yong; Yang, Da-Long

    2016-01-01

    Background The aim of this study was to explore the clinical efficacy of unilateral pedicle screw fixation with bone graft (UPSFB) in treating single-segment lumbar degenerative diseases (LDD), as compared to bilateral pedicle screw fixation with bone graft (BPSFB) or with cage (BPSFC). Material/Methods Medical records were retrospectively collected between 01/2010 and 02/2015 in Longyao County Hospital. According to surgical methods used, all patients were divided into 3 groups: UPSFB group, BPSFB group, and BPSFC group. Clinical outcomes were evaluated by blood loss, blood transfusion, duration of operation, hospital stay, postoperative complications, interbody fusion rate, reoperation rate, medical expenses, patient satisfaction survey, and JOA score. Results Ninety-five patients were included and underwent 2.5-year follow-up, with 7 patients lost to regular follow-up. As compared to the BPSFB group and BPSFC group, the UPSFB group had less blood loss and less blood transfusion, as well as shorter hospital stay (p<0.05). Medical expenses were far lower in the UPSFB group (p<0.001). There were no significant differences among the 3 groups in postoperative complications, interbody fusion rate, reoperation rate, JOA score, and patient satisfaction (all p>0.05). Conclusions As compared to BPSFB and BPSFC, UPSFB has the same reliability and effectiveness in treating single-segment LDD with unilateral radicular symptoms in a single lower extremity, with the additional advantage being less expensive. PMID:26988532

  19. Transforaminal lumbar interbody fusion using unilateral pedicle screws and a translaminar screw

    PubMed Central

    Lee, Sandra; Vaidya, Rahul

    2008-01-01

    Lumbar spinal fusion is advancing with minimally invasive techniques, bone graft alternatives, and new implants. This has resulted in significant reductions of operative time, duration of hospitalization, and higher success in fusion rates. However, costs have increased as many new technologies are expensive. This study was carried out to investigate the clinical outcomes and fusion rates of a low implant load construct of unilateral pedicle screws and a translaminar screw in transforaminal lumbar interbody fusion (TLIF) which reduced the cost of the posterior implants by almost 50%. Nineteen consecutive patients who underwent single level TLIF with this construct were included in the study. Sixteen patients had a TLIF allograft interbody spacer placed, while in three a polyetheretherketone (PEEK) cage was used. Follow-up ranged from 15 to 54 months with a mean of 32 months. A clinical and radiographic evaluation was carried out preoperatively and at multiple time points following surgery. An overall improvement in Oswestry scores and visual analogue scales for leg and back pain (VAS) was observed. Three patients underwent revision surgery due to recurrence of back pain. All patients showed radiographic evidence of fusion from 9 to 26 months (mean 19) following surgery. This study suggests that unilateral pedicle screws and a contralateral translaminar screw are a cheaper and viable option for single level lumbar fusion. PMID:19015896

  20. Thoracic Pedicle Screw Placement Guide Plate Produced by Three-Dimensional (3-D) Laser Printing

    PubMed Central

    Chen, Hongliang; Guo, Kaijing; Yang, Huilin; Wu, Dongying; Yuan, Feng

    2016-01-01

    Background The aim of this study was to evaluate the accuracy and feasibility of an individualized thoracic pedicle screw placement guide plate produced by 3-D laser printing. Material/Methods Thoracic pedicle samples of 3 adult cadavers were randomly assigned for 3-D CT scans. The 3-D thoracic models were established by using medical Mimics software, and a screw path was designed with scanned data. Then the individualized thoracic pedicle screw placement guide plate models, matched to the backside of thoracic vertebral plates, were produced with a 3-D laser printer. Screws were placed with assistance of a guide plate. Then, the placement was assessed. Results With the data provided by CT scans, 27 individualized guide plates were produced by 3-D printing. There was no significant difference in sex and relevant parameters of left and right sides among individuals (P>0.05). Screws were placed with assistance of guide plates, and all screws were in the correct positions without penetration of pedicles, under direct observation and anatomic evaluation post-operatively. Conclusions A thoracic pedicle screw placement guide plate can be produced by 3-D printing. With a high accuracy in placement and convenient operation, it provides a new method for accurate placement of thoracic pedicle screws. PMID:27194139

  1. Spinal pedicle screw planning using deformable atlas registration

    NASA Astrophysics Data System (ADS)

    Goerres, J.; Uneri, A.; De Silva, T.; Ketcha, M.; Reaungamornrat, S.; Jacobson, M.; Vogt, S.; Kleinszig, G.; Osgood, G.; Wolinsky, J.-P.; Siewerdsen, J. H.

    2017-04-01

    Spinal screw placement is a challenging task due to small bone corridors and high risk of neurological or vascular complications, benefiting from precision guidance/navigation and quality assurance (QA). Implicit to both guidance and QA is the definition of a surgical plan—i.e. the desired trajectories and device selection for target vertebrae—conventionally requiring time-consuming manual annotations by a skilled surgeon. We propose automation of such planning by deriving the pedicle trajectory and device selection from a patient’s preoperative CT or MRI. An atlas of vertebrae surfaces was created to provide the underlying basis for automatic planning—in this work, comprising 40 exemplary vertebrae at three levels of the spine (T7, T8, and L3). The atlas was enriched with ideal trajectory annotations for 60 pedicles in total. To define trajectories for a given patient, sparse deformation fields from the atlas surfaces to the input (CT or MR image) are applied on the annotated trajectories. Mean value coordinates are used to interpolate dense deformation fields. The pose of a straight trajectory is optimized by image-based registration to an accumulated volume of the deformed annotations. For evaluation, input deformation fields were created using coherent point drift (CPD) to perform a leave-one-out analysis over the atlas surfaces. CPD registration demonstrated surface error of 0.89  ±  0.10 mm (median  ±  interquartile range) for T7/T8 and 1.29  ±  0.15 mm for L3. At the pedicle center, registered trajectories deviated from the expert reference by 0.56  ±  0.63 mm (T7/T8) and 1.12  ±  0.67 mm (L3). The predicted maximum screw diameter differed by 0.45  ±  0.62 mm (T7/T8), and 1.26  ±  1.19 mm (L3). The automated planning method avoided screw collisions in all cases and demonstrated close agreement overall with expert reference plans, offering a potentially valuable tool in support

  2. Accuracy of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis in the pediatric population.

    PubMed

    Macke, Jeremy J; Woo, Raymund; Varich, Laura

    2016-06-01

    This is a retrospective review of pedicle screw placement in adolescent idiopathic scoliosis (AIS) patients under 18 years of age who underwent robot-assisted corrective surgery. Our primary objective was to characterize the accuracy of pedicle screw placement with evaluation by computed tomography (CT) after robot-assisted surgery in AIS patients. Screw malposition is the most frequent complication of pedicle screw placement and is more frequent in AIS. Given the potential for serious complications, the need for improved accuracy of screw placement has spurred multiple innovations including robot-assisted guidance devices. No studies to date have evaluated this robot-assisted technique using CT exclusively within the AIS population. Fifty patients were included in the study. All operative procedures were performed at a single institution by a single pediatric orthopedic surgeon. We evaluated the grade of screw breach, the direction of screw breach, and the positioning of the patient for preoperative scan (supine versus prone). Of 662 screws evaluated, 48 screws (7.2 %) demonstrated a breach of greater than 2 mm. With preoperative prone position CT scanning, only 2.4 % of screws were found to have this degree of breach. Medial malposition was found in 3 % of screws, a rate which decreased to 0 % with preoperative prone position scanning. Based on our results, we conclude that the proper use of image-guided robot-assisted surgery can improve the accuracy and safety of thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis. This is the first study to evaluate the accuracy of pedicle screw placement using CT assessment in robot-assisted surgical correction of patients with AIS. In our study, the robot-assisted screw misplacement rate was lower than similarly constructed studies evaluating conventional (non-robot-assisted) procedures. If patients are preoperatively scanned in the prone position, the misplacement rate is further

  3. Individualized 3D printing navigation template for pedicle screw fixation in upper cervical spine

    PubMed Central

    Guo, Fei; Dai, Jianhao; Zhang, Junxiang; Ma, Yichuan; Zhu, Guanghui; Shen, Junjie; Niu, Guoqi

    2017-01-01

    Purpose Pedicle screw fixation in the upper cervical spine is a difficult and high-risk procedure. The screw is difficult to place rapidly and accurately, and can lead to serious injury of spinal cord or vertebral artery. The aim of this study was to design an individualized 3D printing navigation template for pedicle screw fixation in the upper cervical spine. Methods Using CT thin slices data, we employed computer software to design the navigation template for pedicle screw fixation in the upper cervical spine (atlas and axis). The upper cervical spine models and navigation templates were produced by 3D printer with equal proportion, two sets for each case. In one set (Test group), pedicle screws fixation were guided by the navigation template; in the second set (Control group), the screws were fixed under fluoroscopy. According to the degree of pedicle cortex perforation and whether the screw needed to be refitted, the fixation effects were divided into 3 types: Type I, screw is fully located within the vertebral pedicle; Type II, degree of pedicle cortex perforation is <1 mm, but with good internal fixation stability and no need to renovate; Type III, degree of pedicle cortex perforation is >1 mm or with the poor internal fixation stability and in need of renovation. Type I and Type II were acceptable placements; Type III placements were unacceptable. Results A total of 19 upper cervical spine and 19 navigation templates were printed, and 37 pedicle screws were fixed in each group. Type I screw-placements in the test group totaled 32; Type II totaled 3; and Type III totaled 2; with an acceptable rate of 94.60%. Type I screw placements in the control group totaled 23; Type II totaled 3; and Type III totaled 11, with an acceptable rate of 70.27%. The acceptability rate in test group was higher than the rate in control group. The operation time and fluoroscopic frequency for each screw were decreased, compared with control group. Conclusion The individualized 3D

  4. Utilization of paraspinal muscles for triggered EMG during thoracic pedicle screw placement.

    PubMed

    Silverstein, Justin W; Mermelstein, Laurence E

    2010-03-01

    A novel intraoperative neurophysiological technique for testing the integrity of the pedicle during screw fixation for spinal deformity surgery is presented. The thoracic paraspinal muscles at the appropriate level are used as the electromyogram (EMG) pick-up for direct current stimulation of the thoracic pedicle screw at that level. This technique is shown to give reliable and reproducible results. This technique is found to produce more reliable data than the methods most commonly used at this time.

  5. Comparative analysis of pedicle screw versus hybrid instrumentation in adolescent idiopathic scoliosis surgery

    PubMed Central

    Rafi, Sohail; Munshi, Naseem; Abbas, Asad; Shaikh, Rabia Hassan; Hashmi, Imtiaz

    2016-01-01

    Introduction: Adolescent idiopathic scoliosis is the most common type of scoliosis. A Cobb angle of 50° will progress beyond the age of spinal maturity. Surgery over bracing is advised at a Cobb angle above or equal to 50°. The aim of surgery is to bring the Cobb angle down below 50° to prevent reprogression as well as improve the quality of life. The objective of the study is to analyze the efficacy and significance in lifestyle improvement of pedicle screw-only fixation system versus the more common hybrid instrumentation system used for the surgical treatment of adolescent idiopathic scoliosis. Materials and Methods: A prospective cohort study was conducted involving two groups of patients were included in the study. One group was operated with pedicle screw-only method while the other with hybrid instrumentation system. The pre- and post-operative Cobb's angles were taken across a follow-up of 4 years. An SRS-30 questionnaire was given in a yearly follow-up to assess the lifestyle improvement of the patient. Results: Pedicle screw-only method was significantly more effective in reducing Cobb's angle (P = 0.0487). It was showed less loss of correction (P = 0.009) pedicle screw-only surgery was also better at reducing thoracic curves (P = 0.001). There seemed a better recovery time with pedicle screw surgery (P = 0.003). Conclusion: Pedicle screws are more effective and durable than hybrid systems at when treating adolescent idiopathic scoliosis. PMID:27695235

  6. Comparison Between Gearshift And Drill Techniques For Pedicle Screw Placement By Resident Surgeons

    PubMed Central

    Allen, Jonathan; Akpolat, Yusuf T.; Kishan, Shyam; Peppers, Tim; Asgarzadie, Farbod

    2015-01-01

    Background Various techniques have been described for pedicle screw placement with established clinical and radiological success. Suboptimal screw trajectories can compromise bony purchase and, worse yet, cause neurological and vascular injuries. Thus, it is of paramount importance to achieve maximum accuracy of screw placement. Our objective is to evaluate the accuracy of pedicle screw placement in the thoracolumbar spine by resident surgeons. Two popular techniques, gearshift versus drill, were compared. Methods This is a a cadaveric surgical technique comparison study. Six resident surgeons instrumented the spine from T1 to S1 using both gearshift and drill techniques. Each pedicle was randomly assigned to either of the techniques. Pedicle screws were placed freehand without radiographic guidance. Violations (medial, lateral, anterior, superior and inferior) were recorded by studying the computerized tomographic scans of instrumented cadavers by blinded observers. Critical perforations were defined as greater than 2mm breach of the pedicle wall. Results A total of 100 vertebrae (200 pedicles) were instrumented in the six cadavers. 103 pedicles were breached (51.5% of total pedicles). Lateral violations were the most encountered (65% of violations, 67 total, 48 critical, 19 noncritical) followed by medial (24%, 25 total, 13 critical, 12 noncritical), and the rest were anterior (3%), superior (4%) and inferior (4%). There was no overall difference in violations comparing the gearshift technique (49.5%, 51 total, 37 critical, 14 noncritical) with drill technique (50.5%, 52 total, 33 critical, 19 noncritical). Analyzing the breaches at individual vertebra indicated most violations at T6 (11), T5 (10), followed by T3 (9) and T4 (9), decreasing towards the lumbosacral vertebrae. Conclusion The results of this study suggest that the gearshift and drill techniques for placement of pedicle screws in the thoracolumbar spine fare similarly with regards to risk of breach

  7. Reliability of the Planned Pedicle Screw Trajectory versus the Actual Pedicle Screw Trajectory using Intra-operative 3D CT and Image Guidance

    PubMed Central

    Ledonio, Charles G.; Hunt, Matthew A.; Siddiq, Farhan; Polly, David W.

    2016-01-01

    Background Technological advances, including navigation, have been made to improve safety and accuracy of pedicle screw fixation. We evaluated the accuracy of the virtual screw placement (Stealth projection) compared to actual screw placement (intra-operative O-Arm) and examined for differences based on the distance from the reference frame. Methods A retrospective evaluation of prospectively collected data was conducted from January 2013 to September 2013. We evaluated thoracic and lumbosacral pedicle screws placed using intraoperative O-arm and Stealth navigation by obtaining virtual screw projections and intraoperative O-arm images after screw placement. The screw trajectory angle to the midsagittal line and superior endplate was compared in the axial and sagittal views, respectively. Percent error and paired t-test statistics were then performed. Results Thirty-one patients with 240 pedicle screws were analyzed. The mean angular difference between the virtual and actual image in all screws was 2.17° ± 2.20° on axial images and 2.16° ± 2.24° on sagittal images. There was excellent agreement between actual and virtual pedicle screw trajectories in the axial and sagittal plane with ICC = 0.99 (95%CI: 0.992-0.995) (p<0.001) and ICC= 0.81 (95%CI: 0.759-0.855) (p<0.001) respectively. When comparing thoracic and lumbar screws, there was a significant difference in the sagittal angulation between the two distributions. No statistical differences were found distance from the reference frame. Conclusion The virtual projection view is clinically accurate compared to the actual placement on intra-operative CT in both the axial and sagittal views. There is slight imprecision (~2°) in the axial and sagittal planes and a minor difference in the sagittal thoracic and lumbar angulation, although these did not affect clinical outcomes. In general, we find that pedicle screw placement using intraoperative cone beam CT and navigation to be accurate and reliable, and as such

  8. Current trends in pedicle screw stimulation techniques: lumbosacral, thoracic, and cervical levels.

    PubMed

    Isley, Michael R; Zhang, Xiao-Feng; Balzer, Jeffrey R; Leppanen, Ronald E

    2012-06-01

    Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that "pedicle screw fixation improves radiographically demonstrated fusion rates;" however the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement of pedicle screws during open instrumentation procedures, and more recently, guiding percutaneous placement (minimally invasive) where the pedicle cannot be easily inspected visually. The latter technique, evoked or triggered EMG when applied to pedicle screw instrumentation surgeries, has been referred to as the pedicle screw stimulation technique. As concluded in the Position Statement by the American Society of Neurophysiological Monitoring (ASNM), multimodality neuromonitoring using free-run EMG and the pedicle screw stimulation technique was considered a practice option and not yet a standard of care (Leppanen 2005). Subsequently, the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Section on Disorders of the Spine and Peripheral Nerves published their "Guidelines for the Performance of Fusion Procedures for Degenerative Disease of the Lumbar Spine" (Heary 2005, Resnick et al. 2005a, Resnick et al. 2005b). It was concluded that the "primary

  9. Accuracy of Pedicle Screw Placement in Scoliosis Surgery: A Comparison between Conventional Computed Tomography-Based and O-Arm-Based Navigation Techniques

    PubMed Central

    Akazawa, Tsutomu; Sakuma, Tsuyoshi; Koyama, Kayo; Nemoto, Tetsuharu; Nawata, Kento; Yamazaki, Atsuro; Minami, Shohei

    2014-01-01

    Study Design Retrospective study. Purpose We compared the accuracy of O-arm-based navigation with computed tomography (CT)-based navigation in scoliotic surgery. Overview of Literature No previous reports comparing the results of O-arm-based navigation with conventional CT-based navigation in scoliotic surgery have been published. Methods A total of 222 pedicle screws were implanted in 29 patients using CT-based navigation (group C) and 416 screws were implanted in 32 patients using O-arm-based navigation (group O). Postoperative CT was performed to assess the screw accuracy, using the established Neo classification (grade 0: no perforation, grade 1: perforation <2 mm, grade 2: perforation ≥2 and <4, and grade 3: perforation ≥4 mm). Results In group C, 188 (84.7%) of the 222 pedicle screw placements were categorized as grade 0, 23 (10.4%) were grade 1, 11 (5.0%) were grade 2, and 0 were grade 3. In group O, 351 (84.4%) of the 416 pedicle screw placements were categorized as grade 0, 52 (12.5%) were grade 1, 13 (3.1%) were grade 2, and 0 were grade 3. Statistical analysis showed no significant difference in the prevalence of grade 2.3 perforations between groups C and O. The time to position one screw, including registration, was 10.9±3.2 minutes in group C, but was significantly decreased to 5.4±1.1 minutes in group O. Conclusions O-arm-based navigation facilitates pedicle screw insertion as accurately as conventional CT-based navigation. The use of O-arm-based navigation successfully reduced the time, demonstrating advantages in the safety and accuracy of pedicle screw placement for scoliotic surgery. PMID:24967047

  10. Fixation Strength of Caudal Pedicle Screws after Posterior Lumbar Interbody Fusion with the Modified Cortical Bone Trajectory Screw Method

    PubMed Central

    Miwa, Toshitada; Yamashita, Tomoya; Kuroda, Yusuke; Ohwada, Tetsuo

    2016-01-01

    Study Design Clinical case series. Purpose In the posterior lumbar interbody fusion (PLIF) procedure in our institute, the cephalad screw trajectory follows a mediolateral and caudocephalad directed path according to the original cortical bone trajectory (CBT) method. However, the starting point of the caudal screw is at the medial border of the pedicle on an articular surface of the superior articular process, and the trajectory takes a mediolateral path parallel to the cephalad endplate. The incidence of caudal screw loosening after PLIF with this modified CBT screw method was investigated, and significant risk factors for caudal screw loosening were evaluated. Overview of Literature A biomechanical study of this modified caudal screw trajectory using the finite element method reported about a 20% increase in uniaxial yield pullout load compared with the traditional trajectory. However, there has been no clinical study concerning the fixation strength of this modified caudal screw trajectory. Methods The subjects were 193 consecutive patients who underwent single-level PLIF with modified CBT screw fixation. Caudal screw loosening was checked in computed tomography at 6 months after surgery, and screw loosening was defined as a radiolucency of 1 mm or more at the bone-screw interface. Results The incidence of caudal screw loosening after lumbosacral PLIF (46.2%) was significantly higher than that after floating PLIF (6.0%). No significant differences in sex, brand of the instruments, and diameter and length of the caudal screw were evident between patients with and without caudal screw loosening. Patients with caudal screw loosening were significantly older at the time of surgery than patients without caudal screw loosening. Conclusions Fixation strength of the caudal screw after floating PLIF with this modified CBT screw technique was sufficiently acceptable. Fixation strength after the lumbosacral procedure was not. PMID:27559442

  11. Early clinical results with cortically based pedicle screw trajectory for fusion of the degenerative lumbar spine.

    PubMed

    Glennie, R Andrew; Dea, Nicolas; Kwon, Brian K; Street, John T

    2015-06-01

    This study reviews the outcomes and revision rates of degenerative lumbar fusion surgery using cortical trajectory pedicle screws in lieu of traditional pedicle screw instrumentation. Pedicle screw fixation can be a challenge in patients with low bone mineral density. Wide posterior approaches to the lumbar spine exposing lateral to the facet joints and onto transverse processes causes an additional degree of muscular damage and blood loss not present with a simple laminectomy. A cortical bone trajectory pedicle screw has been proposed as an alternative to prevent screw pullout and decrease the morbidity associated with the wide posterior approach to the spine. We present a series of eight consecutive patients using a cortical bone trajectory instead of traditional pedicle screw fixation for degenerative conditions of the lumbar spine. A retrospective review of our institutional registry data identified eight patients who had cortical screws placed with the assistance of O-arm Stealth navigation (Medtronic Sofamor Danek, Memphis, TN, USA) from 2010-2013. We analyzed the need for revision, the maintenance of reduction and the incidence of screw pullout or breakage. Our review demonstrated that two of eight patients were revised at an average of 12months. The reasons for these revisions were pseudarthrosis and caudal adjacent segment failure. All patients who were revised had frank screw loosening. We present early clinical results of a new technique that has been shown to have a better fixation profile in laboratory testing. Our less than favorable early clinical results should be interpreted with caution and highlight important technical issues which should be considered.

  12. Assessing the Intraoperative Accuracy of Pedicle Screw Placement by Using a Bone-Mounted Miniature Robot System through Secondary Registration

    PubMed Central

    Wu, Chieh-Hsin; Tsai, Cheng-Yu; Chang, Chih-Hui; Lin, Chih-Lung; Tsai, Tai-Hsin

    2016-01-01

    Introduction Pedicle screws are commonly employed to restore spinal stability and correct deformities. The Renaissance robotic system was developed to improve the accuracy of pedicle screw placement. Purpose In this study, we developed an intraoperative classification system for evaluating the accuracy of pedicle screw placements through secondary registration. Furthermore, we evaluated the benefits of using the Renaissance robotic system in pedicle screw placement and postoperative evaluations. Finally, we examined the factors affecting the accuracy of pedicle screw implantation. Results Through use of the Renaissance robotic system, the accuracy of Kirschner-wire (K-wire) placements deviating <3 mm from the planned trajectory was determined to be 98.74%. According to our classification system, the robot-guided pedicle screw implantation attained an accuracy of 94.00% before repositioning and 98.74% after repositioning. However, the malposition rate before repositioning was 5.99%; among these placements, 4.73% were immediately repositioned using the robot system and 1.26% were manually repositioned after a failed robot repositioning attempt. Most K-wire entry points deviated caudally and laterally. Conclusion The Renaissance robotic system offers high accuracy in pedicle screw placement. Secondary registration improves the accuracy through increasing the precision of the positioning; moreover, intraoperative evaluation enables immediate repositioning. Furthermore, the K-wire tends to deviate caudally and laterally from the entry point because of skiving, which is characteristic of robot-assisted pedicle screw placement. PMID:27054360

  13. Surgical safety of cervical pedicle screw placement with computer navigation system.

    PubMed

    Shimokawa, Nobuyuki; Takami, Toshihiro

    2017-04-01

    Cervical pedicle screw (CPS) may be the biomechanically best system for posterior cervical segmental fixation, but may carry a surgery-related risk. The purpose of this study was to evaluate the safety of CPS placement using computer navigation system for posterior cervical instrumented fixation and discuss its complication avoidance and management. Posterior cervical instrumented fixation using CPS was performed in a total of 128 patients during the period between 2007 and 2015. Intraoperative image guidance was achieved using a preoperative 3D CT-based or an intraoperative 3D CT-based navigation system. A total of 762 CPSs were placed in the spine level of C2 to Th3. The radiological accuracy of CPS placement was evaluated using postoperative CT. Accuracy of CPS placement using a preoperative 3D CT-based navigation system was 93.6 % (423 of 452 screws) in grade 0; the screw was completely contained in the pedicle, and accuracy of CPS placement using an intraoperative 3D CT-based navigation system was a little bit improved to 97.1 % (301 of 310 screws) in grade 0. CPS misplacement (more than half of screw) was 3.3 % (15 of 452 screws) using a preoperative 3D CT-based navigation system, and CPS misplacement (more than half of screw) was 0.6 % (2 of 310 screws) using an intraoperative 3D CT-based navigation system. In total, 38 screws (5.0 %) were found to perforate the cortex of pedicle, although any neural or vascular complications closely associated with CPS placement were not encountered. Twenty nine of 38 screws (76.3 %) were found to perforate laterally, and seven screws (18.4 %) were found to perforate medially. Image-guided CPS placement has been an important advancement to secure the safe surgery, although the use of CPS placement needs to be carefully determined based on the individual pathology.

  14. Inter- and Intra-Observer Reliability of Measurement of Pedicle Screw Breach Assessed by Postoperative CT Scans

    PubMed Central

    Ranade, Ashish; Samdani, Amer F.; Gaughan, John P.; D'Andrea, Linda P.; Betz, Randal R.

    2014-01-01

    Background Pedicle screws are used increasingly in spine surgery. Concerns of complications associated with screw breach necessitates accurate pedicle screw placement. Postoperative CT imaging helps to detect screw malposition and assess its severity. However, accuracy is dependent on the reading of the CT scans. Inter- and intra-observer variability could affect the reliability of CT scans to assess multiple screw types and sites. The purpose of this study was to assess the reliability of multi-observer analysis of CT scans for determining pedicle screw breach for various screw types and sites in patients with spinal deformity or degenerative pathologies. Methods Axial CT scan images of 23 patients (286 screws) were read by four experienced spine surgeons. Pedicle screw placement was considered 'In' when the screw was fully contained and/or the pedicle wall breach was ≤2 mm. 'Out' was defined as a breach in the medial or lateral pedicle wall >2 mm. Intra-class coefficients (ICC) were calculated to assess the inter- and intra-observer reliability. Results Marked inter- and intra-observer variability was noticed. The overall inter-observer ICC was 0.45 (95% confidence limits 0.25 to 0.65). The intra-observer ICC was 0.49 (95% confidence limits 0.29 to 0.69). Underlying spinal pathology, screw type, and patient age did not seem to impact the reliability of our CT assessments. Conclusion Our results indicate the evaluation of pedicle screw breach on CT by a single surgeon is highly variable, and care should be taken when using individual CT evaluations of millimeters of breach as a basis for screw removal. This was a Level III study. PMID:25694925

  15. SU-E-T-609: Perturbation Effects of Pedicle Screws On Radiotherapy Dose Distributions

    SciTech Connect

    Bar-Deroma, R; Borzov, E; Nevelsky, A

    2015-06-15

    Purpose: Radiation therapy in conjunction with surgical implant fixation is a common combined treatment in case of bone metastases. However, metal implants generally used in orthopedic implants perturb radiation dose distributions. Carbon-Fiber Reinforced (CFR) PEEK material has been recently introduced for production of intramedullary screws and plates. Gold powder can be added to the CFR-PEEK material in order to enhance visibility of the screws during intraoperative imaging procedures. In this work, we investigated the perturbation effects of the pedicle screws made of CFR-PEEK, CFR-PEEK with added gold powder (CFR-PEEK-AU) and Titanium (Ti) on radiotherapy dose distributions. Methods: Monte Carlo (MC) simulations were performed using the EGSnrc code package for 6MV beams with 10×10 fields at SSD=100cm. By means of MC simulations, dose distributions around titanium, CFR- PEEK and CFR-PEEK-AU screws (manufactured by Carbo-Fix Orthopedics LTD, Israel) placed in a water phantom were calculated. The screw axis was either parallel or perpendicular to the beam axis. Dose perturbation (relative to dose in homogeneous water phantom) was assessed. Results: Maximum overdose due to backscatter was 10% for the Ti screws, 5% for the CFR-PEEK-AU screws and effectively zero for the CFR-PEEK screws. Maximum underdose due to attenuation was 25% for the Ti screws, 15% for the CFR-PEEK-AU screws and 5% for the CFR-PEEK screws. Conclusion: Titanium screws introduce the largest distortion on the radiation dose distribution. The gold powder added to the CFR-PEEK material improves visibility at the cost of increased dose perturbation. CFR-PEEK screws caused minimal alteration on the dose distribution. This can decrease possible over and underdose of adjacent tissue and thus favorably influence treatment efficiency. The use of such implants has potential clinical advantage in the treatment of neoplastic bone disease.

  16. Fretting corrosion behavior of nitinol spinal rods in conjunction with titanium pedicle screws.

    PubMed

    Lukina, Elena; Kollerov, Mikhail; Meswania, Jay; Khon, Alla; Panin, Pavel; Blunn, Gordon W

    2017-03-01

    Untypical corrosion damage including erosions combined with the build-up of titanium oxide as a corrosion product on the surface of explanted Nitinol spinal rods in the areas where it was in contact with titanium pedicle screw head is reported. It was suggested that Nitinol rods might have inferior fretting corrosion resistance compared with that made of titanium or CoCr. Fretting corrosion of Nitinol spinal rods with titanium (Ti6Al4V) pedicle screws were tested in-vitro by conducting a series of potentiostatic measurements of the peak-to-peak values of fretting corrosion current under bending in a 10% solution of calf serum in PBS. The test included Nitinol rods locked in titanium pedicle screws of different designs. Performance of commercially available titanium (Ti6Al4V) and CoCr spinal rods was also investigated for a comparison. Corrosion damage observed after the in-vitro tests was studied using SEM and EDAX analysis and was compared with patterns on Nitinol rods retrieved 12months after initial surgery. Metal ions level was measured in the test media after in-vitro experiments and in the blood and tissues of the patients who had the rods explanted. The results of this study revealed that Nitinol spinal rods locked in Ti pedicle screws are susceptible to fretting corrosion demonstrating higher fretting corrosion current compared with commercially used Ti6Al4V and CoCr rods. On the surface of Nitinol rods after in-vitro tests and on those retrieved from the patients similar corrosion patterns were observed. Improved resistance to fretting corrosion was observed with Nitinol rods in the in-vitro tests where pedicle screws were used with a stiffer locking mechanism. Since the development of the localized corrosion damage might increase the risk of premature fatigue failure of the rods and result in leaching of Ni ions, it is concluded that Nitinol rods should not be used in conjunction with Ti pedicle screws without special protection especially where the

  17. Fluoroscopy-guided pedicle screw accuracy with a mini-open approach: a tomographic evaluation of 470 screws in 125 patients

    PubMed Central

    Soriano-Sánchez, José Antonio; Gutiérrez-Partida, Carlos Francisco; Ramírez-Barrios, Luis Rodolfo; Ortíz-Leyva, Ramses Uriel; Rodríguez-García, Manuel; Sánchez-Escandón, Oscar

    2015-01-01

    Background Transpedicular screws are currently placed with open free hand and minimally invasive techniques assisted with either fluoroscopy or navigation. Screw placement accuracy had been investigated with several methods reaching accuracy rates from 71.9% to 98.8%. The objective of this study was to assess the accuracy and safety for 2-D fluoroscopy-guided screw placement assisted with electrophysiological monitoring and the inter-observer agreement for the breach classification. Methods A retrospective review was performed on 125 consecutive patients who underwent minimally invasive transforaminal lumbar interbody fusion and transpedicular screws placement between the levels of T-12 and S-1. Screw accuracy was evaluated using a postoperative computed tomography by three independent observers. Pedicle breach was documented when there was a violation in any direction of the pedicle. Inter-observer agreement was assessed with the Kappa coefficient. Results A total of 470 transpedicular screws were evaluated between the levels of T-12 and S-1. In 57 patients the instrumentation was bilateral and in 68 unilateral. A substantial degree of agreement was found between the observers AB (κ=0.769) and A-C (κ=0.784) and almost perfect agreement between observers B-C (κ=0.928). There were a total of 427.33 (90.92%) screws without breach, 39.33 (8.37%) minor breach pedicles and 3.33 (0.71%) major breach pedicles. The pedicle breach rate was 9.08% Trajectory pedicle breach percentages were as follows: minor medial pedicle breach 4.68%, minor lateral pedicle breach 3.47%, minor inferior pedicle breach 0.22%, and major medial breach 0.70%. No intraoperative instrumentation-related or postoperative clinical complications were encountered and no surgical revision was needed. Conclusions Our study demonstrated a high accuracy (90.2%) for 2-D fluoroscopy-guided pedicle screw using electromonitoring. Only 0.71% of the 470 screws had a major breach. Knowing the radiological spine

  18. Designs and Techniques That Improve the Pullout Strength of Pedicle Screws in Osteoporotic Vertebrae: Current Status

    PubMed Central

    Shea, Thomas M.; Laun, Jake; Gonzalez-Blohm, Sabrina A.; Doulgeris, James J.; Lee, William E.; Vrionis, Frank D.

    2014-01-01

    Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein. PMID:24724097

  19. Triggered electromyography for placement of thoracic pedicle screws: is it reliable?

    PubMed

    Samdani, Amer F; Tantorski, Mark; Cahill, Patrick J; Ranade, Ashish; Koch, Stephen; Clements, David H; Betz, Randal R; Asghar, Jahangir

    2011-06-01

    Reliable electromyography (EMG) thresholds for detecting medial breaches in the thoracic spine are lacking, and there is a paucity of reports evaluating this modality in patients with adolescent idiopathic scoliosis (AIS). This retrospective analysis evaluates the ability of triggered EMG to detect medial breaches with thoracic pedicle screws in patients with AIS. We reviewed 50 patients (937 pedicle screws) undergoing posterior spinal fusion (PSF) with intraoperative EMG testing. Postoperative CT scans were used for breach identification, and EMG values were analyzed. There were 47 medial breaches noted with a mean threshold stimulus of 10.2 mA (milliamperes). Only 8/47 breaches stimulated at 2-6 mA. Thirteen of the forty-seven screws tested at an EMG value ≤6 mA and/or a decrease of ≥65% compared with intraosseously placed screws. The sensitivity and positive predictive value for EMG was 0.28 and 0.21. A subanalysis of T10-T12 screws identified six of seven medial breaches. Using guidelines from the current literature, EMG does not appear to be reliable in detecting medial breaches from T2 to T9 but may have some utility from T10 to T12.

  20. Effects on Subtalar Joint Stress Distribution After Cannulated Screw Insertion at Different Positions and Directions.

    PubMed

    Yuan, Cheng-song; Chen, Wan; Chen, Chen; Yang, Guang-hua; Hu, Chao; Tang, Kang-lai

    2015-01-01

    We investigated the effects on subtalar joint stress distribution after cannulated screw insertion at different positions and directions. After establishing a 3-dimensional geometric model of a normal subtalar joint, we analyzed the most ideal cannulated screw insertion position and approach for subtalar joint stress distribution and compared the differences in loading stress, antirotary strength, and anti-inversion/eversion strength among lateral-medial antiparallel screw insertion, traditional screw insertion, and ideal cannulated screw insertion. The screw insertion approach allowing the most uniform subtalar joint loading stress distribution was lateral screw insertion near the border of the talar neck plus medial screw insertion close to the ankle joint. For stress distribution uniformity, antirotary strength, and anti-inversion/eversion strength, lateral-medial antiparallel screw insertion was superior to traditional double-screw insertion. Compared with ideal cannulated screw insertion, slightly poorer stress distribution uniformity and better antirotary strength and anti-inversion/eversion strength were observed for lateral-medial antiparallel screw insertion. Traditional single-screw insertion was better than double-screw insertion for stress distribution uniformity but worse for anti-rotary strength and anti-inversion/eversion strength. Lateral-medial antiparallel screw insertion was slightly worse for stress distribution uniformity than was ideal cannulated screw insertion but superior to traditional screw insertion. It was better than both ideal cannulated screw insertion and traditional screw insertion for anti-rotary strength and anti-inversion/eversion strength. Lateral-medial antiparallel screw insertion is an approach with simple localization, convenient operation, and good safety.

  1. Treatment strategies for early neurological deficits related to malpositioned pedicle screws in the lumbosacral canal

    PubMed Central

    Du, J-Y.; Wu, J-S.; Wen, Z-Q.

    2016-01-01

    Objectives To employ a simple and fast method to evaluate those patients with neurological deficits and misplaced screws in relatively safe lumbosacral spine, and to determine if it is necessary to undertake revision surgery. Methods A total of 316 patients were treated by fixation of lumbar and lumbosacral transpedicle screws at our institution from January 2011 to December 2012. We designed the criteria for post-operative revision scores of pedicle screw malpositioning (PRSPSM) in the lumbosacral canal. We recommend the revision of the misplaced pedicle screw in patients with PRSPSM = 5′ as early as possible. However, patients with PRSPSM < 5′ need to follow the next consecutive assessment procedures. A total of 15 patients were included according to at least three-stage follow-up. Results Five patients with neurological complications (PRSPSM = 5′) underwent revision surgery at an early stage. The other ten patients with PRSPSM < 5′ were treated by conservative methods for seven days. At three-month follow-up, only one patient showed delayed onset of neurological complications (PRSPSM 7′) while refusing revision. Seven months later, PRSPSM decreased to 3′ with complete rehabilitation. Conclusions This study highlights the significance of consecutively dynamic assessments of PRSPSMs, which are unlike previous implementations based on purely anatomical assessment or early onset of neurological deficits.and also confirms our hypothesis that patients with early neurological complications may not need revision procedures in the relatively broad margin of the lumbosacral canal. Cite this article: X-J. Lin. Treatment strategies for early neurological deficits related to malpositioned pedicle screws in the lumbosacral canal: A pilot study. Bone Joint Res 2016;5:46–51. DOI: 10.1302/2046-3758.52.2000477. PMID:26868892

  2. Subsidence of metal interbody cage after posterior lumbar interbody fusion with pedicle screw fixation.

    PubMed

    Tokuhashi, Yasuaki; Ajiro, Yasumitsu; Umezawa, Natsuki

    2009-04-01

    Posterior lumbar interbody fusion is considered to be an excellent fusion procedure to stabilize anterior support, correct alignment in the sagittal and coronal plane, and achieve foraminal decompression by lifting the disk height. The metal interbody cage in posterior lumbar interbody fusion is thought to be useful to prevent collapse of the graft bone and to correct and maintain disk height; however, some studies have noted a gradual decrease of disk height due to cage subsidence. Therefore, to investigate the significance of cage subsidence, 86 disk levels radiographically confirmed to have good union in 66 patients with posterior lumbar interbody fusion combined with pedicle screw fixation and a single metal cage for degenerative lumbar disease were retrospectively evaluated. The follow-up period ranged from 3 years to 10 years 3 months, with a mean of 7 years 9 months. Cage subsidence often showed a gradual increase over time. At final follow-up, subsidence averaged 4.0 mm on the cranial surface and 2.7 mm on the caudal surface. Although the average increase of disk height was 3.2 mm immediately postoperatively, the final disk height decreased by 4.2 mm on average from that time. The degree of cage subsidence and decrease of disk height were not correlated with the final clinical results. Subsidence was not correlated with bone mineral density in the vertebral body, body weight, or site of the insertion. On the other hand, the wedge shape of the cage and the thickness of the resected endplate had a significant influence on cage subsidence.

  3. Computer analysis of the safety of using three different pedicular screw insertion points in the lumbar spine in the Chinese population.

    PubMed

    Hailong, Yu; Wei, Lei; Zhensheng, Ma; Hongxun, Sang

    2007-05-01

    To help decide the best starting point for lumbar spine pedicle screw insertion in the Chinese population using three different techniques (Roy-Camille, Magerl, and Du). Three-dimensional CT reconstructions were created from 40 adult lumbar vertebral segments. Three different starting points for lumbar pedicle screw insertion were used. The direction of the pedicle screw through each hole was simulated on three-dimensional reconstructed images. Precise CT measurements were made to assess the distance from the simulated screw and the medial and lateral pedicle walls at the smallest transverse section of each pedicle. To measure a pedicle transverse section angle (TSA) lines were drawn on a CT scan in the direct axis of the pedicle, tangential to the medial, and separately lateral, walls of the pedicles at the isthmus. The angle these lines made with an anterior to posterior line, which directly bisected the mid-portion of the vertebral body was called the TSA. The greater the difference between the TSA between the medial and lateral walls provides the greatest flexibility for the insertion angle of the pedicle screw. Additionally, the distance from a line drawn in the direct central axis of the pedicle was measured from the point of exit from the pedicle to the entry point of each of three insertion techniques (Du, Mageral, and Roy-Camille), to help understand potential risk factors. There were statistically significant differences between the distances from the entrance point to the direct pedicle axis among the three methods (P < 0.001). Du's insertion point was the shortest from L1 to L4. The distances measured following Magerl's technique were shortest at L5 (P < 0.05). There was no significant difference of the safe range of the TSA between the three methods from L1 and L2 (P > 0.05), but significant differences at L3, L4, and L5 (P < 0.05). At L3 and L4 the safe ranges of TSA using Du and Magerl's methods were significantly larger than those measured by Roy

  4. Feasibility study of patient-specific surgical templates for the fixation of pedicle screws.

    PubMed

    Salako, F; Aubin, C-E; Fortin, C; Labelle, H

    2002-01-01

    Surgery for scoliosis, as well as other posterior spinal surgeries, frequently uses pedicle screws to fix an instrumentation on the spine. Misplacement of a screw can lead to intra- and post-operative complications. The objective of this study is to design patient-specific surgical templates to guide the drilling operation. From the CT-scan of a vertebra, the optimal drilling direction and limit angles are computed from an inverse projection of the pedicle limits. The first template design uses a surface-to-surface registration method and was constructed in a CAD system by subtracting the vertebra from a rectangular prism and a cylinder with the optimal orientation. This template and the vertebra were built using rapid prototyping. The second design uses a point-to-surface registration method and has 6 adjustable screws to adjust the orientation and length of the drilling support device. A mechanism was designed to hold it in place on the spinal process. A virtual prototype was build with CATIA software. During the operation, the surgeon places either template on patient's vertebra until a perfect match is obtained before drilling. The second design seems better than the first one because it can be reused on different vertebra and is less sensible to registration errors. The next step is to build the second design and make experimental and simulations tests to evaluate the benefits of this template during a scoliosis operation.

  5. C1-c2 pedicle screw fixation for treatment of old odontoid fractures.

    PubMed

    Qi, Lei; Li, Mu; Zhang, Shuai; Si, Haipeng; Xue, Jingsong

    2015-02-01

    Nonunion and C1-C2 instability of odontoid fractures usually result from delayed diagnosis and inappropriate treatment. However, the available treatment options for odontoid fractures remain controversial. The authors evaluated the effectiveness of internal screw fixation via the C1 and C2 pedicle in cases of old odontoid fractures. This retrospective study included 21 patients with old odontoid fractures (13 men and 8 women; mean age, 46.5 years; range, 24-69 years). Internal screw fixation via the C1 and C2 pedicle was performed in all patients. Fracture reduction and C1-C2 fusion were assessed with imaging. The neck pain visual analog scale score and cervical spinal cord functional Japanese Orthopaedic Association score (for those who had cervical spinal cord injury) were used to evaluate the effectiveness of treatment. Postoperative complications were recorded. Postoperative imaging showed that the C1-C2 dislocation was satisfactorily repositioned in all patients. Bone fusion was observed 1 year after surgery in all patients. No loosening or breaking of internal fixation occurred. The preoperative neck pain visual analog scale score was 5.9±1.5 and improved significantly to 1.8±0.8 after surgery (P<.001). The Japanese Orthopaedic Association score in patients with cervical spinal injury (n=14) was 9.2±1.9 and also significantly improved to 13.8±1.9 at the last follow-up examination (P<.001), with an average improvement rate of 61.0%. No iatrogenic vertebral artery injury or severe spinal cord injury occurred. Screw fixation via the C1 and C2 pedicle was found to be an effective and safe surgical approach for the treatment of old odontoid fractures with C1-C2 dislocation or instability.

  6. Biomechanical Analysis of a Pedicle Screw-Rod System with a Novel Cross-Link Configuration

    PubMed Central

    Hara, Masahito; Umebayashi, Daisuke; Haimoto, Shoichi; Yamamoto, Yu; Nishimura, Yusuke; Wakabayashi, Toshihiko

    2016-01-01

    Study Design The strength effects of a pedicle screw-rod system supplemented with a novel cross-link configuration were biomechanically evaluated in porcine spines. Purpose To assess the biomechanical differences between a conventional cross-link pedicle screw-rod system versus a novel cross-link instrumentation, and to determine the effect of the cross-links. Overview of Literature Transverse cross-link systems affect torsional rigidity, but are thought to have little impact on the sagittal motion of spinal constructs. We tested the strength effects in pullout and flexion-compression tests of novel cross-link pedicle screw constructs using porcine thoracic and lumbar vertebrae. Methods Five matched thoracic and lumbar vertebral segments from 15 porcine spines were instrumented with 5.0-mm pedicle screws, which were then connected with 6.0-mm rods after partial corpectomy in the middle vertebral body. The forces required for construct failure in pullout and flexion-compression tests were examined in a randomized manner for three different cross-link configurations: un-cross-link control, conventional cross-link, and cross-link passing through the base of the spinous process. Statistical comparisons of strength data were analyzed using Student's t-tests. Results The spinous process group required a significantly greater pullout force for construct failure than the control group (p=0.036). No difference was found between the control and cross-link groups, or the cross-link and spinous process groups in pullout testing. In flexion-compression testing, the spinous processes group required significantly greater forces for construct failure than the control and cross-link groups (p<0.001 and p=0.003, respectively). However, there was no difference between the control and cross-link groups. Conclusions A novel cross-link configuration that features cross-link devices passing through the base of the spinous processes increased the mechanical resistance in pullout and

  7. Mid-Term Results of Computer-Assisted Cervical Pedicle Screw Fixation

    PubMed Central

    Uehara, Masashi; Mukaiyama, Keijiro; Kuraishi, Shugo; Shimizu, Masayuki; Ikegami, Shota; Futatsugi, Toshimasa; Ogihara, Nobuhide; Hashidate, Hiroyuki; Hirabayashi, Hiroki; Kato, Hiroyuki

    2014-01-01

    Study Design A retrospective study. Purpose The present study aimed to evaluate mid-term results of cervical pedicle screw (CPS) fixation for cervical instability. Overview of Literature CPS fixation has widely used in the treatment of cervical spinal instability from various causes; however, there are few reports on mid-term surgical results of CPS fixation. Methods Record of 19 patients who underwent cervical and/or upper thoracic (C2-T1) pedicle screw fixation for cervical instability was reviewed. The mean observation period was 90.2 months. Evaluated items included Japanese Orthopaedic Association (JOA) score and C2-7 lordotic angle before surgery and at 5 years after surgery. Postoperative computerized tomography was used to determine the accuracy of screw placement. Visual analog scale (VAS) for neck pain and radiological evidence of adjacent segment degeneration (ASD) at the 5-year follow-up were also evaluated. Results Mean JOA score was significantly improved from 9.0 points before surgery to 12.8 at 5 years after surgery (p=0.001). The C2-7 lordotic angle of the neutral position improved from 6.4° to 7.8° at 5 years after surgery, but this was not significant. The major perforation rate was 5.0%. There were no clinically significant complications such as vertebral artery injury, spinal cord injury, or nerve root injury caused by any screw perforation. Mean VAS for neck pain was 49.4 at 5 years after surgery. The rate of ASD was 21.1%. Conclusions Our mid-term results showed that CPS fixation was useful for treating cervical instability. Severe complications were prevented with the assistance of a computed tomography-based navigation system. PMID:25558318

  8. Elective thoracotomy for pedicle screw removal to prevent severe aortic bleeding

    PubMed Central

    Decker, Sebastian; Omar, Mohamed; Krettek, Christian; Müller, Christian W

    2014-01-01

    We present a case of a 33-year-old female who sustained multiple injuries of her spine, including spinous process fractures of C5 to C7 and a lamina fracture of C6 and C7. Her thoracic spine showed transverse process fractures of T4 to T10, a compression fracture and lamina fracture of T3, spinous process and transverse process fractures of T4 and T5, a rotation injury of T6, as well as a compression fracture of L1. Thirteen months after posterior thoracic spinal instrumentation, a pedicle screw was suspected to be in contact with the aorta, which was proved by computed tomography angiograms. Consequently, implant removal was planned with direct exposure of the aorta in order to allow for immediate repair if needed. So far, studies that compare different techniques to remove pedicle screws that are suspected to penetrate the aorta are missing. However, different techniques have been described in case reports, mainly minimally invasive endovascular techniques vs open techniques such as thoracotomy. PMID:24749121

  9. Improving fixation strength of pedicle screw by microarc oxidation treatment: an experimental study of osteoporotic spine in sheep.

    PubMed

    Shi, Lei; Wang, Ling; Zhang, Yang; Guo, Zheng; Wu, Zi-xiang; Liu, Da; Gao, Ming-xuan; Chen, Huan; Fu, Suo-chao; Lei, Wei

    2012-08-01

    Failure of fixation caused by loosening of pedicle screws in osteoporosis is a problem in spinal surgery. We compared the in vivo fixation strength between pedicle screws treated with microarc oxidation (MAO) and untreated screws in an osteoporotic model of ovariectomized sheep. The MAO treated and untreated screws were placed in lumbar vertebral bodies. After 3 months of implantation, biomechanical tests, micro-CT analysis, and histological observations were conducted to examine the performance of the two groups. At time 0, no significant difference was found between the two groups in biomechanical tests (p > 0.05); 3 months later, higher pull-out strength and load with less displacement were detected in the MAO-treated group (p < 0.05). Micro-CT analysis showed that the tissue mineral density, bone volume fraction, trabecular thickness, and trabecular number in the MAO-treated group were all higher than those in untreated group (p < 0.05), and trabecular spacing was smaller (p < 0.05). Histologically, the bone-implant interface in the MAO-treated group was better than that in untreated group (p < 0.05). In conclusion, pedicle screws with a bioactive surface treated by MAO can improve screw fixation strength in osteoporotic spines in sheep.

  10. Short Segment versus Long Segment Pedicle Screws Fixation in Management of Thoracolumbar Burst Fractures: Meta-Analysis

    PubMed Central

    2017-01-01

    Posterior pedicle screw fixation has become a popular method for treating thoracolumbar burst fractures. However, it remains unclear whether additional fixation of more segments could improve clinical and radiological outcomes. This meta-analysis was performed to evaluate the effectiveness of fixation levels with pedicle screw fixation for thoracolumbar burst fractures. MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, Springer, and Google Scholar were searched for relevant randomized and quasirandomized controlled trials that compared the clinical and radiological efficacy of short versus long segment for thoracolumbar burst fractures managed by posterior pedicle screw fixation. Risk of bias in included studies was assessed using the Cochrane Risk of Bias tool. Based on predefined inclusion criteria, Nine eligible trials with a total of 365 patients were included in this meta-analysis. Results were expressed as risk difference for dichotomous outcomes and standard mean difference for continuous outcomes with 95% confidence interval. Baseline characteristics were similar between the short and long segment fixation groups. No significant difference was identified between the two groups regarding radiological outcome, functional outcome, neurologic improvement, and implant failure rate. The results of this meta-analysis suggested that extension of fixation was not necessary when thoracolumbar burst fracture was treated by posterior pedicle screw fixation. More randomized controlled trials with high quality are still needed in the future. PMID:28243383

  11. Addressing Stretch Myelopathy in Multilevel Cervical Kyphosis with Posterior Surgery Using Cervical Pedicle Screws

    PubMed Central

    Mahesh, Bijjawara; Vijay, Shekarappa; Arun, Kumar; Srinivasa, Reddy

    2016-01-01

    Study Design Technique description and retrospective data analysis. Purpose To describe the technique of cervical kyphosis correction with partial facetectomies and evaluate the outcome of single-stage posterior decompression and kyphosis correction in multilevel cervical myelopathy. Overview of Literature Kyphosis correction in multilevel cervical myelopathy involves anterior and posterior surgery. With the advent of cervical pedicle screw-rod instrumentation, single-stage posterior kyphosis correction is feasible and can address stretch myelopathy by posterior shortening. Methods Nine patients underwent single-stage posterior decompression and kyphosis correction for multilevel cervical myelopathy using cervical pedicle screw instrumentation from March 2011 to February 2014 and were evaluated preoperatively and postoperatively with modified Japanese Orthopaedic Association (mJOA) scoring and computed tomography scans for radiological measurements. Kyphosis assessment was made with Ishihara curvature index and C2–C7 Cobb's angle. The linear length of the spinal canal and the actual spinal canal length were also evaluated. The average follow-up was 40.56 months (range, 20 to 53 months). Results The average preoperative C2–7 Cobb's angle of 6.3° (1° to 12°) improved to 2° (10° to −9°). Ishihara index improved from −15.8% (−30.5% to −4.7%) to −3.66% (−14.5% to +12.6%). The actual spinal canal length decreased from 83.64 mm (range, 76.8 to 91.82 mm) to 82.68 mm (range, 75.85 to 90.78 mm). The preoperative mJOA score of 7.8 (range, 3 to 11) improved to 15.0 (range, 13 to 17). Conclusions Single-stage posterior decompression and kyphosis correction using cervical pedicle screws for multilevel cervical myelopathy may address stretch myelopathy, in addition to decompression in the transverse plane. However, cervical lordosis was not achieved with this method as predictably as by the anterior approach. The present study shows evidence of mild

  12. Percutaneous pedicle screw for unstable spine fractures in polytraumatized patients: A report of two cases

    PubMed Central

    Tan, Boon Beng; Chan, Chris Yin Wei; Saw, Lim Beng; Kwan, Mun Keong

    2012-01-01

    Unstable spine fractures commonly occur in the setting of a polytraumatized patient. The aim of management is to balance the need for early operative stabilization and prevent additional trauma due to the surgery. Recent published literature has demonstrated the benefits of early stabilization of an unstable spine fracture particularly in patients with higher injury severity score (ISS). We report two cases of polytrauma with unstable spine fractures stabilized with a minimally invasive percutaneous pedicle screw instrumentation system as a form of damage control surgery. The patients had good recovery from the polytrauma injuries. These two cases illustrate the role of minimally invasive stabilization, its limitations and technical pitfalls in the management of unstable spine fractures in the polytrauma setting as a form of damage control surgery. PMID:23325978

  13. The surgical learning curve and accuracy of minimally invasive lumbar pedicle screw placement using CT based computer-assisted navigation plus continuous electromyography monitoring – a retrospective review of 627 screws in 150 patients

    PubMed Central

    McMillen, Jason

    2014-01-01

    Objective This study retrospectively assessed the accuracy of placement of lumbar pedicle screws placed by a single surgeon using a minimally-invasive, intra-operative CT-based computer navigated technique in combination with continuous electromyography (EMG) monitoring. The rates of incorrectly positioned screws were reviewed in the context of the surgeon's experience and learning curve. Methods Data was retrospectively reviewed from all consecutive minimally invasive lumbar fusions performed by the primary author over a period of over 4 years from April 2008 until October 2012. All cases that had utilized computer-assisted intra-operative CT-based image guidance and continuous EMG monitoring to guide percutaneous pedicle screw placement were analysed for the rates of malposition of the pedicle screws. Pedicle screw malposition was defined as having occurred if the screw trajectory was adjusted intraoperatively due to positive EMG responses, or due to breach of the pedicle cortex by more than 2mm on intraoperative CT imaging performed at the end of the instrumentation procedure. Further analysis of the data was undertaken to determine if the rates of malposition changed with the surgeon's experience with the technique. Results Six hundred and twenty-seven pedicle screws were placed in one hundred and fifty patients. The overall rate of intraoperative malposition and subsequent adjustment of pedicle screw placement was 3.8% (24 of 627 screws). Screw malposition was detected by intraoperative CT imaging. Warning of potential screw misplacement was provided by use of the EMG monitoring. With increased experience with the technique, rates of intraoperative pedicle screw malposition were found to decrease from 5.1% of screws in the first fifty patients, to 2.0% in the last 50 patients. Only one screw was suboptimally placed at the end of surgery, which did not result in a neurological deficit. Conclusion The use of CT-based computer-assisted navigation in combination

  14. Cervical anterior transpedicular screw fixation (ATPS)—Part II. Accuracy of manual insertion and pull-out strength of ATPS

    PubMed Central

    Acosta, Frank; Tauber, Mark; Fox, Michael; Martin, Hudelmaier; Forstner, Rosmarie; Augat, Peter; Penzkofer, Rainer; Pirich, Christian; Kässmann, H.; Resch, Herbert; Hitzl, Wolfgang

    2008-01-01

    Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications in a previous study in Part I of our project. Consequently, the objectives of the current study were to assess the ex vivo accuracy of placing ATPS into the cervical vertebra as well as the biomechanical performance of ATPS in comparison to traditional vertebral body screws (VBS) in terms of pull-out strength (POS). Twenty-three ATPS were inserted alternately to two screws into the pedicles and vertebral bodies, respectively, of six cadaveric specimens from C3–T1. For insertion of ATPS, a manual fluoroscopically assisted technique was used. Pre- and post insertional CT-scans were used to assess accuracy of ATPS insertion in the axial and sagittal planes. A newly designed grading system and accuracy score were used to delineate accuracy of ATPS insertion. Following insertion of screws, 23 ATPS and 22 VBS were subjected to pull-out testing (POT). The bone mineral density (BMD) of each specimen was assessed prior to POT. Statistical analysis showed that the incidence of correctly placed screws and non-critical pedicles breaches in axial plane was 78.3%, and 95.7% in sagittal plane. Hence, according to our definition of “critical” pedicle breach that exposes neurovascular structures at risk, 21.7% (n = 5) of all ATPS inserted showed a critical pedicle breach in axial plane. Notably, no critical pedicle perforation occurred at the C6 to T1 levels. Pull-out testing of ATPS and VBS revealed that pull-out resistance of ATPS was 2.5-fold that of VBS. Mean POS of 23 ATPS with a mean BMD of 0.566

  15. Pedicle screw-based posterior dynamic stabilisation of the lumbar spine: in vitro cadaver investigation and a finite element study.

    PubMed

    Oktenoglu, T; Erbulut, D U; Kiapour, A; Ozer, A F; Lazoglu, I; Kaner, T; Sasani, M; Goel, V K

    2015-08-01

    Pedicle screw-based dynamic constructs either benefit from a dynamic (flexible) interconnecting rod or a dynamic (hinged) screw. Both types of systems have been reported in the literature. However, reports where the dynamic system is composed of two dynamic components, i.e. a dynamic (hinged) screw and a dynamic rod, are sparse. In this study, the biomechanical characteristics of a novel pedicle screw-based dynamic stabilisation system were investigated and compared with equivalent rigid and semi-rigid systems using in vitro testing and finite element modelling analysis. All stabilisation systems restored stability after decompression. A significant decrease in the range of motion was observed for the rigid system in all loadings. In the semi-rigid construct the range of motion was significantly less than the intact in extension, lateral bending and axial rotation loadings. There were no significant differences in motion between the intact spine and the spine treated with the dynamic system (P>0.05). The peak stress in screws was decreased when the stabilisation construct was equipped with dynamic rod and/or dynamic screws.

  16. The pedicle screw-rod system is an acceptable method of reconstructive surgery after resection of sacroiliac joint tumours

    PubMed Central

    Zhou, Yi-Jun; Yunus, Akbar; Tian, Zheng; Chen, Jiang-Tao; Wang, Chong; Xu, Lei-Lei

    2016-01-01

    Hemipelvic resections for primary bone tumours require reconstruction to restore weight bearing along anatomic axes. However, reconstruction of the pelvic arch remains a major surgical challenge because of the high rate of associated complications. We used the pedicle screw-rod system to reconstruct the pelvis, and the purpose of this investigation was to assess the oncology, functional outcome and complication rate following this procedure. The purpose of this study was to investigate the operative indications and technique of the pedicle screw-rod system in reconstruction of the stability of the sacroiliac joint after resection of sacroiliac joint tumours. The average MSTS (Musculoskeletal Tumour Society) score was 26.5 at either three months after surgery or at the latest follow-up. Seven patients had surgery-related complications, including wound dehiscence in one, infection in two, local necrosis in four (including infection in two), sciatic nerve palsy in one and pubic symphysis subluxation in one. There was no screw loosening or deep vein thrombosis occurring in this series. Using a pedicle screw-rod after resection of a sacroiliac joint tumour is an acceptable method of pelvic reconstruction because of its reduced risk of complications and satisfactory functional outcome, as well as its feasibility of reconstruction for type IV pelvis tumour resection without elaborate preoperative customisation. Level of evidence: Level IV, therapeutic study. PMID:27095944

  17. Decisive factor in increase of loading at adjacent segments after lumbar fusion: operative technique, pedicle screws, or fusion itself: biomechanical analysis using finite element

    NASA Astrophysics Data System (ADS)

    Park, Joon-Hee; Kim, Ho-Joong; Kang, Kyoung-Tak; Kim, Ka-Yeon; Chun, Heoung-Jae; Moon, Seong-Hwan; Lee, Hwan-Mo

    2009-12-01

    The aim of this study is to investigate the change in biomechanical milieu following removal of pedicle screws or removal of spinous process with posterior ligament complex in instrumented single level lumbar arthrodesis. We developed and validated a finite element model (FEM) of the intact lumbar spine (L2-4). Four scenarios of L3-4 lumbar fusion were simulated: posterolateral fusion (PLF) at L3-4 using pedicle screw system with preservation of PLC (Pp WiP), L3-4 lumbar posterolateral fusion state after removal of pedicle screw system with preservation of PLC (Pp WoP), L3-4 using pedicle screw system without preservation PLC (Sp WiP), L3-4 lumbar posterolateral fusion state after removal of pedicle screw system without preservation of PLC (Sp WoP). For these models, we investigated the range of motion and maximal Von mises stress of disc in all segments under various moments. All fusion models demonstrated increase in range of motion at adjacent segments compared to the intact model.For the four fusion models, the WiP model s P had the largest increase in range of motion at each adjacent segment. This study demonstrated that removal of pedicle screw system and preservation of PLC after complete lumbar spinal fusion could reduce the stress of adjacent segments synergistically and might have beneficial effects in preventing ASD.

  18. Decisive factor in increase of loading at adjacent segments after lumbar fusion: operative technique, pedicle screws, or fusion itself: biomechanical analysis using finite element

    NASA Astrophysics Data System (ADS)

    Park, Joon-Hee; Kim, Ho-Joong; Kang, Kyoung-Tak; Kim, Ka-yeon; Chun, Heoung-Jae; Moon, Seong-Hwan; Lee, Hwan-Mo

    2010-03-01

    The aim of this study is to investigate the change in biomechanical milieu following removal of pedicle screws or removal of spinous process with posterior ligament complex in instrumented single level lumbar arthrodesis. We developed and validated a finite element model (FEM) of the intact lumbar spine (L2-4). Four scenarios of L3-4 lumbar fusion were simulated: posterolateral fusion (PLF) at L3-4 using pedicle screw system with preservation of PLC (Pp WiP), L3-4 lumbar posterolateral fusion state after removal of pedicle screw system with preservation of PLC (Pp WoP), L3-4 using pedicle screw system without preservation PLC (Sp WiP), L3-4 lumbar posterolateral fusion state after removal of pedicle screw system without preservation of PLC (Sp WoP). For these models, we investigated the range of motion and maximal Von mises stress of disc in all segments under various moments. All fusion models demonstrated increase in range of motion at adjacent segments compared to the intact model.For the four fusion models, the WiP model s P had the largest increase in range of motion at each adjacent segment. This study demonstrated that removal of pedicle screw system and preservation of PLC after complete lumbar spinal fusion could reduce the stress of adjacent segments synergistically and might have beneficial effects in preventing ASD.

  19. Diathermy testing: a novel method with electric knife stimulation to avoid nerve injuries during lumbar pedicle screw placement. Technical note.

    PubMed

    Yamazaki, Takashi; Matsudaira, Ko

    2007-05-01

    The purpose of this retrospective study was to demonstrate the utility of diathermy in avoiding nerve injuries due to misplacement of lumbar pedicle screws (PSs). The authors used diathermy to assess whether a screw deviated from the pedicle by observing synchronous leg movements caused by intermittently touching an electric knife to the pedicular instrument. Diathermy was performed in 259 cases in which 1301 PSs had been placed. Leg movements were observed in 36 cases, and the sensitivity of diathermy was 85.7%, with a specificity of 99.5%. No neurological complications associated with the placement of PSs were observed after adding diathermy testing to conventional methods. Diathermy testing may be a way to avoid nerve injuries during lumbar PS placement.

  20. Treatment of Unstable Posterior Pelvic Ring Fracture with Pedicle Screw-Rod Fixator Versus Locking Compression Plate: A Comparative Study

    PubMed Central

    Bi, Chun; Wang, Qiugen; Nagelli, Christopher; Wu, Jianhong; Wang, Qian; Wang, Jiandong

    2016-01-01

    Background The aim of this study was to assess the clinical results of treatment for unstable posterior pelvic fractures using a pedicle screw-rod fixator compared to use of a locking compression plate. Material/Methods A retrospective study was performed between June 2010 and May 2014 and the data were collected from 46 patients with unstable posterior pelvic ring fractures. All patients were treated using either a pedicle screw-rod fixator (study group, 24 patients) or locking compression plate (control group, 22 patients). In these patients, causes of injury included traffic accidents (n=27), fall from height (n=12), and crushing accidents (n=7). The quality of reduction and radiological grading were assessed. Clinical assessments included the operation time, times of X-ray exposures, bleeding volume during operation, incision length, and Majeed postoperative functional evaluation. Results No iatrogenic neurovascular injuries occurred during the operations in these 2 groups. The average follow-up time was 24.5 months. All fractures were healed. The significant differences (P<0.05) between the 2 groups were operation duration, size of incision, and intraoperative bleeding volume. Statistically significant differences in the Majeed postoperative functional evaluation and times of X-ray exposures were not found between the 2 groups. Conclusions Similar clinical effects were achieved in treating the posterior pelvic ring fractures using the pedicle screw-rod fixator and the locking compression plate. However, the pedicle screw-rod fixator has the advantages of smaller incision, shorter duration of the operation, and less bleeding volume compared to using the locking compression plate. PMID:27748355

  1. Biomechanical Comparison of Spinal Fusion Methods Using Interspinous Process Compressor and Pedicle Screw Fixation System Based on Finite Element Method

    PubMed Central

    Choi, Jisoo; Kim, Sohee

    2016-01-01

    Objective To investigate the biomechanical effects of a newly proposed Interspinous Process Compressor (IPC) and compare with pedicle screw fixation at surgical and adjacent levels of lumbar spine. Methods A three dimensional finite element model of intact lumbar spine was constructed and two spinal fusion models using pedicle screw fixation system and a new type of interspinous devices, IPC, were developed. The biomechanical effects such as range of motion (ROM) and facet contact force were analyzed at surgical level (L3/4) and adjacent levels (L2/3, L4/5). In addition, the stress in adjacent intervertebral discs (D2, D4) was investigated. Results The entire results show biomechanical parameters such as ROM, facet contact force, and stress in adjacent intervertebral discs were similar between PLIF and IPC models in all motions based on the assumption that the implants were perfectly fused with the spine. Conclusion The newly proposed fusion device, IPC, had similar fusion effect at surgical level, and biomechanical effects at adjacent levels were also similar with those of pedicle screw fixation system. However, for clinical applications, real fusion effect between spinous process and hooks, duration of fusion, and influence on spinous process need to be investigated through clinical study. PMID:26962413

  2. The Use of Percutaneous Lumbar Fixation Screws for Bilateral Pedicle Fractures with an Associated Dislocation of a Lumbar Disc Prosthesis

    PubMed Central

    Harrison, William D.; Harrison, David J.

    2013-01-01

    Study Design. Case report. Objective. To identify a safe technique for salvage surgery following complications of total disc replacement. Summary of Background Data. Lumbar total disc replacement (TDR) is considered by some as the gold standard for discogenic back pain. Revision techniques for TDR and their complications are in their infancy. This case describes a successful method of fixation for this complex presentation. Methods and Results. A 48-year-old male with lumbar degenerative disc disease and no comorbidities. Approximately two weeks postoperatively for a TDR, the patient represented with acute severe back pain and the TDR polyethylene inlay was identified as dislocated anteriorly. Subsequent revision surgery failed immediately as the polyethylene inlay redislocated intraoperatively. Further radiology identified bilateral pedicle fractures, previously unseen on the plain films. The salvage fusion of L5/S1 reutilized the anterior approach with an interbody fusion cage and bone graft. The patient was then turned intraoperatively and redraped. The percutaneous pedicle screws were used to fix L5 to the sacral body via the paracoccygeal corridor. Conclusion. The robust locking screw in the percutaneous screw allowed a complete fixation of the pedicle fractures. At 3-year followup, the patient has an excellent result and has returned to playing golf. PMID:24294533

  3. Comparative Analysis of Interval, Skipped, and Key-vertebral Pedicle Screw Strategies for Correction in Patients With Lenke Type 1 Adolescent Idiopathic Scoliosis

    PubMed Central

    Wang, Fei; Xu, Xi-Ming; Lu, Yanghu; Wei, Xian-Zhao; Zhu, Xiao-Dong; Li, Ming

    2016-01-01

    Abstract Pedicle screw constructs have become the mainstay for surgical correction in patients with spinal deformities. To reduce or avoid the risk of pedicle screw-based complications and to decrease the costs associated with pedicle screw instrumentation, some authors have introduced interval, skipped, and key-vertebral pedicle screw strategies for correction. However, there have been no comparisons of outcomes among these 3 pedicle screw-placement strategies. The aim of this study was to compare the correlative clinical outcomes of posterior correction and fusion with pedicle screw fixation using these 3 surgical strategies. Fifty-six consecutive patients with Lenke type 1 adolescent idiopathic scoliosis were included in this study. Twenty patients were treated with the interval pedicle screw strategy (IPSS), 20 with the skipped pedicle screw strategy (SPSS), and 16 with the key-vertebral pedicle screw strategy (KVPSS). Coronal and sagittal radiographs were analyzed before surgery, at 1 week after surgery, and at the last follow-up after surgery. There were no significant differences among the 3 groups regarding preoperative radiographic parameters. No significant difference was found between the IPSS and SPSS groups in correction of the main thoracic curve (70.8% vs 70.0%; P = 0.524). However, there were statistically significant differences between the IPSS and KVPSS groups (70.8% vs 64.9%) and between the SPSS and KVPSS groups (70.0% vs 64.9%) in correction of the main thoracic curve (P < 0.001 for both). Additionally, there were no significant differences among the 3 strategies for sagittal parameters at the immediate postoperative and last postoperative follow-up periods, though there were significant differences in the Cobb angle between the preoperative and immediate postoperative periods among the 3 groups, but not between the immediate postoperative and last follow-up periods. The amount of hospital charges in the SPSS group was significantly

  4. Freehand Thoracic Pedicle Screw Placement: Review of Existing Strategies and a Step-by-Step Guide Using Uniform Landmarks for All Levels

    PubMed Central

    Baaj, Ali A

    2016-01-01

    Pedicle screw fixation in the thoracic spine presents certain challenges due to the critical regional neurovascular anatomy as well as the narrow pedicular corridor that typically exists. With increased awareness of the dangers of intraoperative radiation, the ability to place pedicle screws with anatomic landmarks alone is paramount. In this study, we reviewed the literature from 1990 to 2015 for studies that included freehand pedicle screw placement in the thoracic spine with special emphasis on entry points and the trajectories of the screws. We excluded studies that used fluoroscopy guidance, navigation techniques, cadaveric and biomechanical articles, case reports, and experimental studies on animals. The search retrieved 40 articles, and after careful selection, seven articles were analyzed. Over 8,000 screws were placed in the different studies. The mean accuracy for placement of the thoracic screws was 93.3%. However, there is little consensus between studies in entry points, sagittal, and axial trajectories of the screws. We complete this review by presenting our step-by-step technique for the placement of freehand pedicle screws in the thoracic spine. PMID:27014535

  5. Comparison of Surgical Outcomes Between Short-Segment Open and Percutaneous Pedicle Screw Fixation Techniques for Thoracolumbar Fractures

    PubMed Central

    Fu, Zhiguo; Zhang, Xi; Shi, Yaohua; Dong, Qirong

    2016-01-01

    Background This study aimed to compare the surgical outcomes between open pedicle screw fixation (OPSF) and percutaneous pedicle screw fixation (PPSF) for the treatment of thoracolumbar fractures, which has received scant research attention to date. Material/Methods Eight-four patients with acute and subacute thoracolumbar fractures who were treated with SSPSF from January 2013 to June 2014 at the Changzhou Hospital of Traditional Chinese Medicine (Changzhou, China) were retrospectively reviewed. The patients were divided into 4 groups: the OPSF with 4 basic screws (OPSF-4) group, the OPSF with 4 basic and 2 additional screws (OPSF-6) group, the PPSF with 4 basic screws (PPSF-4) group, and the PPSF with 4 basic and 2 additional screws (PPSF-6) group. The intraoperative, immediate postoperative, and over 1-year follow-up outcomes were evaluated and compared among these groups. Results Blood loss in the PPSF-4 group and the PPSF-6 group was significantly less than in the OPSF-4 group and the OPSF-6 group (P<0.05). The OPSF-6 group exhibited significantly higher immediate postoperative correction percentage of anterior column height of fractured vertebra than the other 3 groups (P<0.05), and higher correction of sagittal regional Cobb angle and kyphotic angle of injured vertebra than in the PPSF-4 and -6 groups (P<0.05). In addition, there was no significant difference in the correction loss of percentage of anterior column height, and loss of sagittal Cobb angle and kyphotic angle of fractured vertebrae at final follow-up among the 4 groups (P>0.05). Conclusions OPSF with 6 screws had an advantage in the correction of injured vertebral height and kyphosis, and PPSF reduced the intraoperative blood loss of patients. PMID:27602557

  6. Known-component 3D-2D registration for quality assurance of spine surgery pedicle screw placement

    PubMed Central

    Uneri, A; De Silva, T; Stayman, JW; Kleinszig, G; Vogt, S; Khanna, AJ; Gokaslan, ZL; Wolinsky, J-P; Siewerdsen, JH

    2015-01-01

    Purpose A 3D-2D image registration method is presented that exploits knowledge of interventional devices (e.g., K-wires or spine screws – referred to as “known components”) to extend the functionality of intraoperative radiography/fluoroscopy by providing quantitative measurement and quality assurance (QA) of the surgical product. Methods The known-component registration (KC-Reg) algorithm uses robust 3D-2D registration combined with 3D component models of surgical devices known to be present in intraoperative 2D radiographs. Component models were investigated that vary in fidelity from simple parametric models (e.g., approximation of a screw as a simple cylinder, referred to as “parametrically-known” component [pKC] registration) to precise models based on device-specific CAD drawings (referred to as “exactly-known” component [eKC] registration). 3D-2D registration from three intraoperative radiographs was solved using the covariance matrix adaptation evolution strategy (CMA-ES) to maximize image-gradient similarity, relating device placement relative to 3D preoperative CT of the patient. Spine phantom and cadaver studies were conducted to evaluate registration accuracy and demonstrate QA of the surgical product by verification of the type of devices delivered and conformance within the “acceptance window” of the spinal pedicle. Results Pedicle screws were successfully registered to radiographs acquired from a mobile C-arm, providing TRE 1–4 mm and <5° using simple parametric (pKC) models, further improved to <1 mm and <1° using eKC registration. Using advanced pKC models, screws that did not match the device models specified in the surgical plan were detected with an accuracy of >99%. Visualization of registered devices relative to surgical planning and the pedicle acceptance window provided potentially valuable QA of the surgical product and reliable detection of pedicle screw breach. Conclusions 3D-2D registration combined with 3D models

  7. Known-component 3D-2D registration for quality assurance of spine surgery pedicle screw placement.

    PubMed

    Uneri, A; De Silva, T; Stayman, J W; Kleinszig, G; Vogt, S; Khanna, A J; Gokaslan, Z L; Wolinsky, J-P; Siewerdsen, J H

    2015-10-21

    A 3D-2D image registration method is presented that exploits knowledge of interventional devices (e.g. K-wires or spine screws-referred to as 'known components') to extend the functionality of intraoperative radiography/fluoroscopy by providing quantitative measurement and quality assurance (QA) of the surgical product. The known-component registration (KC-Reg) algorithm uses robust 3D-2D registration combined with 3D component models of surgical devices known to be present in intraoperative 2D radiographs. Component models were investigated that vary in fidelity from simple parametric models (e.g. approximation of a screw as a simple cylinder, referred to as 'parametrically-known' component [pKC] registration) to precise models based on device-specific CAD drawings (referred to as 'exactly-known' component [eKC] registration). 3D-2D registration from three intraoperative radiographs was solved using the covariance matrix adaptation evolution strategy (CMA-ES) to maximize image-gradient similarity, relating device placement relative to 3D preoperative CT of the patient. Spine phantom and cadaver studies were conducted to evaluate registration accuracy and demonstrate QA of the surgical product by verification of the type of devices delivered and conformance within the 'acceptance window' of the spinal pedicle. Pedicle screws were successfully registered to radiographs acquired from a mobile C-arm, providing TRE 1-4 mm and  <5° using simple parametric (pKC) models, further improved to  <1 mm and  <1° using eKC registration. Using advanced pKC models, screws that did not match the device models specified in the surgical plan were detected with an accuracy of  >99%. Visualization of registered devices relative to surgical planning and the pedicle acceptance window provided potentially valuable QA of the surgical product and reliable detection of pedicle screw breach. 3D-2D registration combined with 3D models of known surgical devices offers a

  8. Biomechanical Analysis of Fusion Segment Rigidity Upon Stress at Both the Fusion and Adjacent Segments: A Comparison between Unilateral and Bilateral Pedicle Screw Fixation

    PubMed Central

    Kim, Ho-Joong; Kang, Kyoung-Tak; Chang, Bong-Soon; Lee, Choon-Ki; Kim, Jang-Woo

    2014-01-01

    Purpose The purpose of this study was to investigate the effects of unilateral pedicle screw fixation on the fusion segment and the superior adjacent segment after one segment lumbar fusion using validated finite element models. Materials and Methods Four L3-4 fusion models were simulated according to the extent of decompression and the method of pedicle screws fixation in L3-4 lumbar fusion. These models included hemi-laminectomy with bilateral pedicle screw fixation in the L3-4 segment (BF-HL model), total laminectomy with bilateral pedicle screw fixation (BF-TL model), hemi-laminectomy with unilateral pedicle screw fixation (UF-HL model), and total laminectomy with unilateral pedicle screw fixation (UF-TL model). In each scenario, intradiscal pressures, annulus stress, and range of motion at the L2-3 and L3-4 segments were analyzed under flexion, extension, lateral bending, and torsional moments. Results Under four pure moments, the unilateral fixation leads to a reduction in increment of range of motion at the adjacent segment, but larger motions were noted at the fusion segment (L3-4) in the unilateral fixation (UF-HL and UF-TL) models when compared to bilateral fixation. The maximal von Mises stress showed similar patterns to range of motion at both superior adjacent L2-3 segments and fusion segment. Conclusion The current study suggests that unilateral pedicle screw fixation seems to be unable to afford sufficient biomechanical stability in case of bilateral total laminectomy. Conversely, in the case of hemi-laminectomy, unilateral fixation could be an alternative option, which also has potential benefit to reduce the stress of the adjacent segment. PMID:25048501

  9. Vertebroplasty plus short segment pedicle screw fixation in a burst fracture model in cadaveric spines.

    PubMed

    Grossbach, Andrew J; Viljoen, Stephanus V; Hitchon, Patrick W; DeVries Watson, Nicole A; Grosland, Nicole M; Torner, James

    2015-05-01

    The current project investigates the role of vertebroplasty in supplementing short segment (SS) posterior instrumentation, only one level above and below a fracture. In the treatment of thoracolumbar burst fractures, long segment (LS) posterior instrumentation two levels above and below the fracture level has been used. In our study, burst fractures were produced at L1 in eight fresh frozen human cadaveric spines. The spines were then tested in three conditions: 1) intact, 2) after LS (T11-L3), 3) SS (T12-L2) instrumentation with pedicle screws and rods, and 4) short segment instrumentation plus cement augmentation of the fracture level (SSC). LS instrumentation was found to significantly reduce the motion at the instrumented level (T12-L2) as well as the levels immediately adjacent in flexion, extension and lateral bending. Similarly, SSC augmentation was found to significantly reduce the motion compared to intact at T12-L2 but still maintained the adjacent level motion. However, SS instrumentation alone did not significantly reduce the motion at T12-L2 except for left lateral bending. While LS instrumentation remains the most stable construct, SS instrumentation augmented with vertebroplasty at the fracture level increases rigidity in flexion, extension and right lateral bending beyond SS instrumentation alone.

  10. A New Electromagnetic Navigation System for Pedicle Screws Placement: A Human Cadaver Study at the Lumbar Spine

    PubMed Central

    Hahn, Patrick; Oezdemir, Semih; Komp, Martin; Giannakopoulos, Athanasios; Heikenfeld, Roderich; Kasch, Richard; Merk, Harry; Godolias, Georgios; Ruetten, Sebastian

    2015-01-01

    Introduction Technical developments for improving the safety and accuracy of pedicle screw placement play an increasingly important role in spine surgery. In addition to the standard techniques of free-hand placement and fluoroscopic navigation, the rate of complications is reduced by 3D fluoroscopy, cone-beam CT, intraoperative CT/MRI, and various other navigation techniques. Another important aspect that should be emphasized is the reduction of intraoperative radiation exposure for personnel and patient. The aim of this study was to investigate the accuracy of a new navigation system for the spine based on an electromagnetic field. Material and Method Twenty pedicle screws were placed in the lumbar spine of human cadavers using EMF navigation. Navigation was based on data from a preoperative thin-slice CT scan. The cadavers were positioned on a special field generator and the system was matched using a patient tracker on the spinous process. Navigation was conducted using especially developed instruments that can be tracked in the electromagnetic field. Another thin-slice CT scan was made postoperatively to assess the result. The evaluation included the position of the screws in the direction of trajectory and any injury to the surrounding cortical bone. The results were classified in 5 groups: grade 1: ideal screw position in the center of the pedicle with no cortical bone injury; grade 2: acceptable screw position, cortical bone injury with cortical penetration ≤ 2 mm; grade 3: cortical bone injury with cortical penetration 2,1-4 mm, grad 4: cortical bone injury with cortical penetration 4,1-6 mm, grade 5: cortical bone injury with cortical penetration >6 mm. Results The initial evaluation of the system showed good accuracy for the lumbar spine (65% grade 1, 20% grade 2, 15% grade 3, 0% grade 4, 0% grade 5). A comparison of the initial results with other navigation techniques in literature (CT navigation, 2D fluoroscopic navigation) shows that the accuracy of

  11. Known-component 3D-2D registration for quality assurance of spine surgery pedicle screw placement

    NASA Astrophysics Data System (ADS)

    Uneri, A.; De Silva, T.; Stayman, J. W.; Kleinszig, G.; Vogt, S.; Khanna, A. J.; Gokaslan, Z. L.; Wolinsky, J.-P.; Siewerdsen, J. H.

    2015-10-01

    A 3D-2D image registration method is presented that exploits knowledge of interventional devices (e.g. K-wires or spine screws—referred to as ‘known components’) to extend the functionality of intraoperative radiography/fluoroscopy by providing quantitative measurement and quality assurance (QA) of the surgical product. The known-component registration (KC-Reg) algorithm uses robust 3D-2D registration combined with 3D component models of surgical devices known to be present in intraoperative 2D radiographs. Component models were investigated that vary in fidelity from simple parametric models (e.g. approximation of a screw as a simple cylinder, referred to as ‘parametrically-known’ component [pKC] registration) to precise models based on device-specific CAD drawings (referred to as ‘exactly-known’ component [eKC] registration). 3D-2D registration from three intraoperative radiographs was solved using the covariance matrix adaptation evolution strategy (CMA-ES) to maximize image-gradient similarity, relating device placement relative to 3D preoperative CT of the patient. Spine phantom and cadaver studies were conducted to evaluate registration accuracy and demonstrate QA of the surgical product by verification of the type of devices delivered and conformance within the ‘acceptance window’ of the spinal pedicle. Pedicle screws were successfully registered to radiographs acquired from a mobile C-arm, providing TRE 1-4 mm and  <5° using simple parametric (pKC) models, further improved to  <1 mm and  <1° using eKC registration. Using advanced pKC models, screws that did not match the device models specified in the surgical plan were detected with an accuracy of  >99%. Visualization of registered devices relative to surgical planning and the pedicle acceptance window provided potentially valuable QA of the surgical product and reliable detection of pedicle screw breach. 3D-2D registration combined with 3D models of known surgical

  12. Multiobjective optimization design of spinal pedicle screws using neural networks and genetic algorithm: mathematical models and mechanical validation.

    PubMed

    Amaritsakul, Yongyut; Chao, Ching-Kong; Lin, Jinn

    2013-01-01

    Short-segment instrumentation for spine fractures is threatened by relatively high failure rates. Failure of the spinal pedicle screws including breakage and loosening may jeopardize the fixation integrity and lead to treatment failure. Two important design objectives, bending strength and pullout strength, may conflict with each other and warrant a multiobjective optimization study. In the present study using the three-dimensional finite element (FE) analytical results based on an L25 orthogonal array, bending and pullout objective functions were developed by an artificial neural network (ANN) algorithm, and the trade-off solutions known as Pareto optima were explored by a genetic algorithm (GA). The results showed that the knee solutions of the Pareto fronts with both high bending and pullout strength ranged from 92% to 94% of their maxima, respectively. In mechanical validation, the results of mathematical analyses were closely related to those of experimental tests with a correlation coefficient of -0.91 for bending and 0.93 for pullout (P < 0.01 for both). The optimal design had significantly higher fatigue life (P < 0.01) and comparable pullout strength as compared with commercial screws. Multiobjective optimization study of spinal pedicle screws using the hybrid of ANN and GA could achieve an ideal with high bending and pullout performances simultaneously.

  13. Minimally invasive transforaminal lumbar interbody fusion with unilateral pedicle screw fixation: comparison between primary and revision surgery.

    PubMed

    Kang, Moo Sung; Park, Jeong Yoon; Kim, Kyung Hyun; Kuh, Sung Uk; Chin, Dong Kyu; Kim, Keun Su; Cho, Yong Eun

    2014-01-01

    Minimally invasive surgery with a transforaminal lumbar interbody fusion (MIS TLIF) is an important minimally invasive fusion technique for the lumbar spine. Lumbar spine reoperation is challenging and is thought to have greater complication risks. The purpose of this study was to compare MIS TLIF with unilateral screw fixation perioperative results between primary and revision surgeries. This was a prospective study that included 46 patients who underwent MIS TLIF with unilateral pedicle screw. The patients were divided into two groups, primary and revision MIS TLIF, to compare perioperative results and complications. The two groups were similar in age, sex, and level of operation, and were not significantly different in the length of follow-up or clinical results. Although dural tears were more common with the revision group (primary 1; revision 4), operation time, blood loss, total perioperative complication, and fusion rates were not significantly different between the two groups. Both groups showed substantial improvements in VAS and ODI scores one year after surgical treatment. Revision MIS TLIF performed by an experienced surgeon does not necessarily increase the risk of perioperative complication compared with primary surgery. MIS TLIF with unilateral pedicle screw fixation is a valuable option for revision lumbar surgery.

  14. Construction and Accuracy Assessment of Patient-Specific Biocompatible Drill Template for Cervical Anterior Transpedicular Screw (ATPS) Insertion: An In Vitro Study

    PubMed Central

    Kong, Xiangxue; Zhao, Weidong; Tang, Lei; Li, Jianyi; Ouyang, Jun

    2013-01-01

    Background With the properties of three-column fixation and anterior-approach-only procedure, anterior transpedicular screw (ATPS) is ideal for severe multilevel traumatic cervical instabilities. However, the accurate insertion of ATPS remains challenging. Here we constructed a patient-specific biocompatible drill template and evaluated its accuracy in assisting ATPS insertion. Methods After ethical approval, 24 formalin-preserved cervical vertebrae (C2–C7) were CT scanned. 3D reconstruction models of cervical vertebra were obtained with 2-mm-diameter virtual pin tracts at the central pedicles. The 3D models were used for rapid prototyping (RP) printing. A 2-mm-diameter Kirschner wire was then inserted into the pin tract of the RP model before polymethylmethacrylate was used to construct the patient-specific biocompatible drill template. After removal of the anterior soft tissue, a 2-mm-diameter Kirschner wire was inserted into the cervical pedicle with the assistance of drill template. Cadaveric cervical spines with pin tracts were subsequently scanned using the same CT scanner. A 3D reconstruction was performed of the scanned spines to get 3D models of the vertebrae containing the actual pin tracts. The deviations were calculated between 3D models with virtual and actual pin tracts at the middle point of the cervical pedicle. 3D models of 3.5 mm-diameter screws were used in simulated insertion to grade the screw positions. Findings The patient-specific biocompatible drill template was constructed to assist ATPS insertion successfully. There were no significant differences between medial/lateral deviations (P = 0.797) or between superior/inferior deviations (P = 0.741). The absolute deviation values were 0.82±0.75 mm and 1.10±0.96 mm in axial and sagittal planes, respectively. In the simulated insertion, the screws in non-critical position were 44/48 (91.7%). Conclusions The patient-specific drill template is biocompatible, easy-to-apply and accurate

  15. The outcome of pedicle screw instrumentation removal for ongoing low back pain following posterolateral lumbar fusion

    PubMed Central

    Brumby-Rendell, Oscar P.; McDonald, Ben; Fisher, Tom; Tsimiklis, Christovalantis; Yoon, Wai Weng; Osti, Orso L.

    2015-01-01

    Background Our aim was to determine whether patients derived benefit from removal of pedicle screw instrumentation for axial pain without other cause using our surgical technique and patient selection. A secondary aim was to investigate factors that were associated with poorer outcomes for this procedure as well as complication rate in this cohort. Methods Theater records from a single spinal surgeon’s practice were reviewed to identify patients that had undergone lumbar fusion for discogenic back pain with subsequent pedicle screw instrumentation removal (Expedium, DePuy Synthes) in the preceding 3 years with a minimum of 18 months follow-up. Inclusion criteria were persisting midline axial back pain with computed tomography (CT)−confirmed solid fusion with non-radicular symptoms and nil other potential causes found, e.g., infection. Case note review along with pre- and post-operative Oswestry disability index (ODI) questionnaires and visual analog scores (VAS) were assessed for all patients. Surgical technique included re-use of previous midline posterior incision and the Wiltse approach with removal of implants, confirmation of a solid fusion mass, washout and bone grafting of removal sites. Results From 50 consecutive patients who underwent removal of posterolateral instrumentation for an index elective lumbar fusion for discogenic back pain, 34 patients were identified that met the criteria with a mean follow-up of 25 months (range, 18-36 months). The VAS and ODI improved in 22/34 (65%) of participants. The mean cohort VAS score was 6.6 pre-surgery and 4.3 post-surgery (P=0.04). Preoperative and postoperative mean Oswestry disability scores were 64 and 41, respectively (P=0.05). There was a statistically significant difference in the proportion of patients with poorer compared to satisfactory outcomes with regards to compensable status, preoperative grade II opioid use and shorter time between fusion and removal procedure. Complications were one

  16. A demineralized calf vertebra model as an alternative to classic osteoporotic vertebra models for pedicle screw pullout studies.

    PubMed

    Akbay, Atilla; Bozkurt, Gokhan; Ilgaz, Ozgur; Palaoglu, Selcuk; Akalan, Nejat; Benzel, Edward C

    2008-03-01

    Screws, clamps and other spinal instrumentation materials are tested using healthy animal and healthy human vertebrae, but the application of similar tests to an osteoporotic vertebra is generally neglected because of high costs and limited availability of high quality and consistent osteoporotic vertebrae. The objective of this study is to develop an in-vitro method to decrease the mineral content of an animal vertebra utilizing decalcifying chemical agents that alters the bone mineral density and some biomechanical properties to such an extent that they biomechanically mimic the osteoporotic spine. This study was performed on 24 fresh calf lumbar vertebrae. Twelve out of these 24 vertebrae were demineralized and the others served as control. A hole was opened in the pedicles of each vertebrae and the bone mineral density was measured. Each vertebra was then placed into a beher-glass filled with hydrochloric acid decalcifier solution. The decalcifier solution was introduced through the holes in the pedicles with an infusion pump. The vertebrae were then subjected to DEXA to measure post process BMD. Pedicle screws were introduced into both pedicles of each vertebrae and pullout testing was performed at a rate of 5 mm/min. The difference of BMD measurements between pre- and post-demineralizing process were also statistically significant (p < 0.001). The difference of pullout loads between pre- and post-demineralizing process were also statistically significant (p < 0.001). The acid demineralizing process may be useful for producing a vertebra that has some biomechanical properties that are consistent with osteopenia or osteoporosis in humans.

  17. One-stage posterior C2 and C3 pedicle screw fixation or combined anterior C2-C3 fusion for the treatment of unstable hangman's fracture.

    PubMed

    Liu, Jingchen; Li, Ye; Wu, Yuntao

    2013-03-01

    The present study aimed to evaluate the effect of using one-stage posterior C2 and C3 pedicle screw fixation or combined anterior C2-C3 fusion in the treatment of unstable hangman's fracture. A total of 13 patients with unstable hangman's fractures underwent C2 and C3 pedicle screw fixation, lamina interbody fusion or combined anterior C2-C3 fusion and imaging examinations to evaluate the fracture fixation and healing condition at three days and three months following surgery. Postoperative X-ray and computed tomography (CT) results showed high fracture reduction, good internal fixation position and reliable fracture fixation. The three-month postoperative CT showed good vertebral fracture healing. C2 and C3 pedicle screw fixation has a good curative effect in the treatment of unstable hangman's fracture. The direct fixation of the fracture enables early ambulation by the patients.

  18. A Universal Pedicle Screw and V-Rod System for Lumbar Isthmic Spondylolysis: A Retrospective Analysis of 21 Cases

    PubMed Central

    Chen, Xiong-sheng; Zhou, Sheng-yuan; Jia, Lian-shun; Gu, Xiao-min; Fang, Lei; Zhu, Wei

    2013-01-01

    Objective To investigate the surgical outcome of a universal pedicle screw-V rod system and isthmic bone grafting for isthmic spondylolysis. Methods Twenty-four patients with isthmic spondylolysis at L5 and grade 0–I spondylolisthesis (Meyerding classification) received isthmic bone graft and stabilization using the universal pedicle screw-V rod system. Back pain was evaluated using the visual analog scale (VAS) and time to bone healing, improvement in spondylolisthesis and intervertebral space height at L5/S1 and L4/L5 were assessed. Results Twenty-one patients were followed up for 24 months and included in the analysis. Back pain was markedly improved at 3 months postoperatively with a statistical difference in VAS scores compared with preoperative VAS scores (P<0.001). The VAS scores were 0 to 3 at 6 months postoperatively in all patients and no back pain was reported in all patients except 2 patients who complained of back pain after prolonged sitting. X-ray examination showed a bone graft healing time of 3 to 12 months. Grade I spondylolisthesis improved to grade 0 in 4 patients and no noticeable change was observed in the remaining 17 cases. The intervertebral space height at L5/S1 was statistically increased (P<0.05) while no statistically significant change was seen at L4/L5. There was no statistically significant difference in the ROM of the intervertebral disks of L5/S1 and L4/5 before and after surgery. Conclusions The universal pedicle screw-V rod system and isthmic bone grafting directly repairs isthmic spondylolysis and reduces back pain, prevents anterior displacement of the diseased segment and maintains intervertebral space height, thus offering a promising alternative to current approaches for isthmic spondylolysis. PMID:23691090

  19. Posterior fusion only for thoracic adolescent idiopathic scoliosis of more than 80°: pedicle screws versus hybrid instrumentation

    PubMed Central

    Bakaloudis, Georgios; Lolli, Francesco; Vommaro, Francesco; Martikos, Konstantinos; Parisini, Patrizio

    2008-01-01

    The treatment of thoracic adolescent idiopathic scoliosis (AIS) of more than 80° traditionally consisted of a combined procedure, an anterior release performed through an open thoracotomy followed by a posterior fusion. Recently, some studies have reassessed the role of posterior fusion only as treatment for severe thoracic AIS; the correction rate of the thoracic curves was comparable to most series of combined anterior and posterior surgery, with shorter surgery time and without the negative effect on pulmonary function of anterior transthoracic exposure. Compared with other studies published so far on the use of posterior fusion alone for severe thoracic AIS, the present study examines a larger group of patients (52 cases) reviewed at a longer follow-up (average 6.7 years, range 4.5–8.5 years). The aim of the study was to evaluate the clinical and radiographic outcome of surgical treatment for severe thoracic (>80°) AIS treated with posterior spinal fusion alone, and compare comprehensively the results of posterior fusion with a hybrid construct (proximal hooks and distal pedicle screws) versus a pedicle screw instrumentation. All patients (n = 52) with main thoracic AIS curves greater than 80° (Lenke type 1, 2, 3, and 4), surgically treated between 1996 and 2000 at one institution, by posterior spinal fusion either with hybrid instrumentation (PSF–H group; n = 27 patients), or with pedicle screw-only construct (PSF–S group; n = 25 patients) were reviewed. There were no differences between the two groups in terms of age, Risser’s sign, Cobb preoperative main thoracic (MT) curve magnitude (PSF–H: 92° vs. PSF–S: 88°), or flexibility on bending films (PSF–H: 27% vs. PSF–S: 25%). Statistical analysis was performed using the t test (paired and unpaired), Wilcoxon test for non-parametric paired analysis, and the Mann–Whitney test for non-parametric unpaired analysis. At the last follow-up, the PSF–S group, when compared to the PSF

  20. Finite element analysis of Stryker Xia pedicle screw in artificial bone samples with and without supplemental cement augmentation.

    PubMed

    Pfeiffer, Ferris M; Choma, Theodore J; Kueny, Rebecca

    2015-01-01

    A validated, using in vitro biomechanical testing, finite element model was used to evaluate the affects of (1) cement augmentation and (2) an intact posterior cortex in osteoporotic bone. The presence of augmentation and/or a posterior cortical cortex increased the stabilization of the pedicle screw 2-5 fold. Placement of cement influenced failure load and toggle; with distal placement having the largest increase in failure load and decrease in cephalad-caudad toggle. The presence of posterior cortex caused a decrease in the amount of toggle, a proximal shift of the center of rotation and an increase in the maximum failure force.

  1. The effect of screw insertion torque on tendons fixed with spiked washers.

    PubMed

    Beynnon, B D; Meriam, C M; Ryder, S H; Fleming, B C; Johnson, R J

    1998-01-01

    The long-term success of a hamstring tendon graft depends not only on the type of device that is used for fixation but also on the mechanical interlocking of the soft tissue between the fixation device and bone. The purpose of this study was to evaluate the effect of screw insertion torque on the structural properties of soft tissue fixed to bone with a spiked metal washer. Two bovine tendons, one similar in size to a human semitendinosus tendon and the other similar in size to a human gracilis tendon, were secured to a bovine femur using a figure-of-8 technique with screws and metal spiked washers. A single load to failure was applied at 25 mm/sec. A significant positive linear correlation was observed between fixation screw insertion torque magnitude and the ultimate failure load value. An increase in the fixation screw insertion torque produced an increase in the ultimate failure load value. Similarly, there was a significant positive linear correlation between fixation screw insertion torque magnitude and the average maximum linear load value. No relationship was detected between screw insertion torque magnitude and the linear stiffness values of the tendon-fixation construct, indicating that a reproducible model was used. This study demonstrates that screw insertion torque is an important variable that controls the initial strength of soft tissue fixation to bone.

  2. The effect of insertion angle on orthodontic mini-screw torque

    PubMed Central

    Raji, Seyed Hamid; Noorollahian, Saeed; Niknam, Seyed Mohsen

    2014-01-01

    Background: Primary stability is an important factor for the clinical success of orthodontic mini-screws. The present study made an attempt to evaluate the effect of insertion angle changes on the maximum insertion and removal torque of orthodontic mini-screws. Materials and Methods: In this experimental study, 72 mini-screws (Dual Top Anchor System, Jeil, 1.6 mm diameter, 8 mm length) were used. They were randomly divided into four equal groups and inserted in poly-carbonate plates with 3 mm thickness. Then, their maximum insertion torque (MIT) and maximum removal torque (MRT) were recorded using a digital torque tester/screwdriver. Each group had a different insertion angle (90°, 75°, 60° and 45°). The data were analyzed by SPSS software (version 18) using one-way ANOVA and post-hoc Tukey's tests. The level of significance was set at 0.05. Results: The maximum MIT was observed in 45° insertion angle (14.84 Ncm) and the minimum MIT was reported in 75° insertion angle (12.66 Ncm). The maximum MRT was observed in 45° insertion angle (23.21 Ncm) and the minimum MRT was reported in the 90° insertion angle (17.43 Ncm). Conclusion: Oblique insertion of the mini-screws results in higher insertion and removal torques and probably more primary stability compared to the vertical insertion. PMID:25225557

  3. The use of computer-assisted surgery as an educational tool for the training of orthopedic surgery residents in pedicle screw placement: a pilot study and survey among orthopedic residents

    PubMed Central

    Aoude, Ahmed; Alhamzah, Hamzah; Fortin, Maryse; Jarzem, Peter; Ouellet, Jean; Weber, Michael H.

    2016-01-01

    Background The training of orthopedic residents in adequate pedicle screw placement is very important. We sought to investigate orthopedic residents’ perspectives on the use of computer-assisted surgery (CAS) in a training trial. Methods Orthopedic residents were randomly assigned to independently place a screw using the free-hand technique and the CAS technique on 1 of 3 cadavers (Cobb angles 5º, 15º and 67º) at randomly selected thoracolumbar vertebral levels. All residents were blinded to their colleagues’ pedicle screw placements and were asked to complete a short questionnaire at the end of the session to evaluate their experience with CAS. We obtained CT images for each cadaver to assess pedicle screw placement accuracy and classified placement as A) screw completely in pedicle, B) screw < 2 mm outside pedicle, C) screw 2–4 mm outside pedicle, or D) screw > 4 mm outside pedicle. Results Twenty-four orthopedic residents participated in this trial study. In total, 65% preferred using the free-hand technique in an educational setting even though most (60%) said that CAS is safer. The main reason for free-hand technique preference was the difficult technical aspects encountered with CAS. In addition, accuracy of pedicle screw placement in this trial showed that 5 screws were classified as A or B (safe zone) and 19 as grade C or D (unsafe zone) using the free-hand technique compared with 15 and 9, respectively, using CAS (p = 0.008). Conclusion Orthopedic residents perceived CAS as safe and demonstrated improved accuracy in pedicle screw placement in a single setting. However, the residents preferred the free-hand technique in an educational stetting owing to the difficult technical aspects of CAS. PMID:28234614

  4. Less invasive lumbopelvic fixation technique using a percutaneous pedicle screw system for unstable pelvic ring fracture in a patient with severe multiple traumas.

    PubMed

    Yano, Sei; Aoki, Yasuchika; Watanabe, Atsuya; Nakajima, Takayuki; Takazawa, Makoto; Hirasawa, Hiroyuki; Takahashi, Kazuhisa; Nakagawa, Koichi; Nakajima, Arata; Takahashi, Hiroshi; Orita, Sumihisa; Eguchi, Yawara; Suzuki, Takane; Ohtori, Seiji

    2017-02-01

    Pelvic ring fractures are defined as life-threatening injuries that can be treated surgically with external or internal fixation. The authors report on an 81-year-old woman with an unstable pelvic fracture accompanying multiple traumas that was successfully treated with a less invasive procedure. The patient was injured in a traffic accident and sustained a total of 20 fractures, including pelvic ring, bilateral rib, and lumbar transverse processes fractures, and multiple fractures of both upper and lower extremities. The pelvic ring fracture was unstable with fractures of the bilateral sacrum with right sacroiliac disruption, right superior and inferior pubic rami, left superior pubic ramus, and ischium. During emergency surgery, bilateral external fixation was applied to the iliac crest to stabilize the pelvic ring. Second and third surgeries were performed 11 and 18 days after the first emergency surgery, respectively, to treat the multiple fractures. At the third surgery, the pelvic ring fracture was stabilized surgically using a less invasive posterior fixation technique. In this technique, 2 iliac screws were inserted on each side following an 8-cm midline posterior incision from the S-1 to S-3 spinous process, with the subcutaneous tissue detached from the fascia of the paraspinal muscles. The S-2 spinous process was removed and 2 rods were connected to bilateral iliac screws to stabilize the bilateral ilium in a switchback fashion. A crosslink device was applied to connect the 2 rods at the base of the S-2 spinous process. Following pelvic fixation, percutaneous pedicle screws were inserted into L-4 and L-5 vertebral bodies on both sides, and connected to the cranial rod connecting the bilateral iliac screws, thus completing the lumbopelvic fixation. The postoperative course was favorable with no postoperative complications. At the 10-month follow-up, bone union had been achieved at the superior ramus of the pubis, the patient did not complain of pain, and

  5. Posterior lumbar interbody fusion with cortical bone trajectory screw fixation versus posterior lumbar interbody fusion using traditional pedicle screw fixation for degenerative lumbar spondylolisthesis: a comparative study.

    PubMed

    Sakaura, Hironobu; Miwa, Toshitada; Yamashita, Tomoya; Kuroda, Yusuke; Ohwada, Tetsuo

    2016-11-01

    OBJECTIVE Several biomechanical studies have demonstrated the favorable mechanical properties of the cortical bone trajectory (CBT) screw. However, no reports have examined surgical outcomes of posterior lumbar interbody fusion (PLIF) with CBT screw fixation for degenerative spondylolisthesis (DS) compared with those after PLIF using traditional pedicle screw (PS) fixation. The purposes of this study were thus to elucidate surgical outcomes after PLIF with CBT screw fixation for DS and to compare these results with those after PLIF using traditional PS fixation. METHODS Ninety-five consecutive patients underwent PLIF with CBT screw fixation for DS (CBT group; mean followup 35 months). A historical control group consisted of 82 consecutive patients who underwent PLIF with traditional PS fixation (PS group; mean follow-up 40 months). Clinical status was assessed using the Japanese Orthopaedic Association (JOA) scale score. Fusion status was assessed by dynamic plain radiographs and CT. The need for additional surgery and surgery-related complications was also evaluated. RESULTS The mean JOA score improved significantly from 13.7 points before surgery to 23.3 points at the latest follow-up in the CBT group (mean recovery rate 64.4%), compared with 14.4 points preoperatively to 22.7 points at final follow-up in the PS group (mean recovery rate 55.8%; p < 0.05). Solid spinal fusion was achieved in 84 patients from the CBT group (88.4%) and in 79 patients from the PS group (96.3%, p > 0.05). Symptomatic adjacent-segment disease developed in 3 patients from the CBT group (3.2%) compared with 9 patients from the PS group (11.0%, p < 0.05). CONCLUSIONS PLIF with CBT screw fixation for DS provided comparable improvement of clinical symptoms with PLIF using traditional PS fixation. However, the successful fusion rate tended to be lower in the CBT group than in the PS group, although the difference was not statistically significant between the 2 groups.

  6. Two levels above and one level below pedicle screw fixation for the treatment of unstable thoracolumbar fracture with partial or intact neurology

    PubMed Central

    Modi, Hitesh N; Chung, Kook Jin; Seo, Il Woo; Yoon, Hoi Soo; Hwang, Ji Hyo; Kim, Hong Kyun; Noh, Kyu Cheol; Yoo, Jung Han

    2009-01-01

    Background Treatment of unstable thoracolumbar fractures is controversial regarding short or long segment pedicle screw fixation. Although long level fixation is better, it can decrease one motion segment distally, thus increasing load to lower discs. Methods We retrospectively analyzed 31 unstable thoracolumbar fractures with partial or intact neurology. All patients were operated with posterior approach using pedicle screws fixed two levels above and one level below the fracture vertebra. No laminectomy, discectomy or decompression procedure was done. Posterior fusion was achieved in all. Post operative and at final follow-up radiological evaluation was done by measuring the correction and maintenance of kyphotic angle at thoracolumbar junction. Complications were also reported including implant failure. Results Average follow-up was 34 months. All patients had full recovery at final follow-up. Average kyphosis was improved from 26.7° to 4.1° postoperatively and to 6.3° at final follow-up. And mean pain scale was improved from 7.5 to 3.9 postoperatively and to 1.6 at final follow-up, All patients resumed their activity within six months. Only 4 (12%) complications were noted including only one hardware failure. Conclusion Two levels above and one level below pedicle screw fixation in unstable thoracolumbar burst fracture is useful to prevent progressive kyphosis and preserves one motion segment distally. PMID:19635134

  7. Comparison of Radiation Exposure in Lumbar Pedicle Screw Placement With Fluoroscopy Vs Computer-Assisted Image Guidance With Intraoperative Three-Dimensional Imaging

    PubMed Central

    Smith, Harvey E; Welsch, Matthew D; Sasso, Rick C; Vaccaro, Alexander R

    2008-01-01

    Background/Objective: Little is known about the long-term effects of chronic exposure to ionizing radiation. Studies have shown that spine surgeons may be exposed to significantly more radiation than that observed in surgery on the appendicular skeleton. Computer-assisted image guidance systems have been shown in preliminary studies to enable accurate instrumentation of the spine. Computer-assisted image guidance systems may have significant application to the surgical management of spinal trauma and deformity. The objective of this study was to compare C-arm fluoroscopy and computer-assisted image guidance in terms of radiation exposure to the operative surgeon when placing pedicle screw-rod constructs in cadaver specimens. Methods: Twelve single-level (2 contiguous vertebral bodies) lumbar pedicle screw-rod constructs (48 screws) in 4 fresh cadavers were placed using standard C-arm fluoroscopy and computer-assisted image guidance (Stealth Station with Iso-C3D). Pedicle screw-rod constructs were placed at L1–L2, L3–L4, and L5–S1 in 4 fresh cadaver specimens. Imaging was alternated between C-arm fluoroscopy and computer-assisted image guidance with StealthStation Iso-C3D. Radiation exposure was measured using ring and badge dosimeters to monitor the thyroid, torso, and index finger. Postprocedure CT scans were obtained to judge accuracy of screw placement. Results: Mean radiation exposure to the torso was 4.33 ± 2.66 mRem for procedures performed with standard fluoroscopy and 0.33 ± 0.82 mRem for procedures performed with computer-assisted image guidance. This difference was statistically significant (P = 0.012). Radiation exposure to the index finger and thyroid was negligible for all procedures. The accuracy of screw placement was similar for both techniques. Conclusions: Computer-assisted image guidance systems allow for the safe and accurate placement of pedicle screw-rod constructs with a significant reduction in exposure to ionizing radiation to the

  8. Postoperative quality-of-life assessment in patients with spine metastases treated with long-segment pedicle-screw fixation.

    PubMed

    Bernard, Florian; Lemée, Jean-Michel; Lucas, Olivier; Menei, Philippe

    2017-03-24

    OBJECTIVE In recent decades, progress in the medical management of cancer has been significant, resulting in considerable extension of survival for patients with metastatic disease. This has, in turn, led to increased attention to the optimal surgical management of bone lesions, including metastases to the spine. In addition, there has been a shift in focus toward improving quality of life and reducing hospital stay for these patients, and many minimally invasive techniques have been introduced with the aim of reducing the morbidity associated with more traditional open approaches. The goal of this study was to assess the efficacy of long-segment percutaneous pedicle screw stabilization for the treatment of instability associated with thoracolumbar spine metastases in neurologically intact patients. METHODS This study was a retrospective review of data from a prospective database. The authors analyzed cases in which long-segment percutaneous pedicle screw fixation was performed for the palliative treatment of thoracolumbar spinal instability due to spinal metastases in neurologically intact patients. All of the patients included in the study underwent surgery between January 2014 and May 2015 at the authors' institution. Postoperative radiation therapy was planned within 10 days following the stabilization in all cases. Clinical and radiological follow-up assessments were planned for 3 days, 3 weeks, 6 weeks, 3 months, 6 months, and 1 year after surgery. Outcome was assessed by means of standard postoperative evaluation and oncological and spinal quality of life measures (European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Version 3.0 [EORTC QLQ-C30] and Oswestry Disability Index [ODI], respectively). Moreover, 5 patients were given an activity monitoring device for recording the distance walked daily; preoperative and postoperative daily distances were compared. RESULTS Data from 17 cases were analyzed. There were no

  9. Known-Component 3D-2D Registration for Image Guidance and Quality Assurance in Spine Surgery Pedicle Screw Placement

    PubMed Central

    Uneri, A.; Stayman, J. W.; De Silva, T.; Wang, A. S.; Kleinszig, G.; Vogt, S.; Khanna, A. J.; Wolinsky, J.-P.; Gokaslan, Z. L.; Siewerdsen, J. H.

    2015-01-01

    Purpose To extend the functionality of radiographic/fluoroscopic imaging systems already within standard spine surgery workflow to: 1) provide guidance of surgical device analogous to an external tracking system; and 2) provide intraoperative quality assurance (QA) of the surgical product. Methods Using fast, robust 3D-2D registration in combination with 3D models of known components (surgical devices), the 3D pose determination was solved to relate known components to 2D projection images and 3D preoperative CT in near-real-time. Exact and parametric models of the components were used as input to the algorithm to evaluate the effects of model fidelity. The proposed algorithm employs the covariance matrix adaptation evolution strategy (CMA-ES) to maximize gradient correlation (GC) between measured projections and simulated forward projections of components. Geometric accuracy was evaluated in a spine phantom in terms of target registration error at the tool tip (TREx), and angular deviation (TREϕ) from planned trajectory. Results Transpedicle surgical devices (probe tool and spine screws) were successfully guided with TREx <2 mm and TREϕ<0.5° given projection views separated by at least >30° (easily accommodated on a mobile C-arm). QA of the surgical product based on 3D-2D registration demonstrated the detection of pedicle screw breach with TREx <1 mm, demonstrating a trend of improved accuracy correlated to the fidelity of the component model employed. Conclusions 3D-2D registration combined with 3D models of known surgical components provides a novel method for near-real-time guidance and quality assurance using a mobile C-arm without external trackers or fiducial markers. Ongoing work includes determination of optimal views based on component shape and trajectory, improved robustness to anatomical deformation, and expanded preclinical testing in spine and intracranial surgeries. PMID:26028805

  10. Known-component 3D-2D registration for image guidance and quality assurance in spine surgery pedicle screw placement

    NASA Astrophysics Data System (ADS)

    Uneri, A.; Stayman, J. W.; De Silva, T.; Wang, A. S.; Kleinszig, G.; Vogt, S.; Khanna, A. J.; Wolinsky, J.-P.; Gokaslan, Z. L.; Siewerdsen, J. H.

    2015-03-01

    Purpose. To extend the functionality of radiographic / fluoroscopic imaging systems already within standard spine surgery workflow to: 1) provide guidance of surgical device analogous to an external tracking system; and 2) provide intraoperative quality assurance (QA) of the surgical product. Methods. Using fast, robust 3D-2D registration in combination with 3D models of known components (surgical devices), the 3D pose determination was solved to relate known components to 2D projection images and 3D preoperative CT in near-real-time. Exact and parametric models of the components were used as input to the algorithm to evaluate the effects of model fidelity. The proposed algorithm employs the covariance matrix adaptation evolution strategy (CMA-ES) to maximize gradient correlation (GC) between measured projections and simulated forward projections of components. Geometric accuracy was evaluated in a spine phantom in terms of target registration error at the tool tip (TREx), and angular deviation (TREΦ) from planned trajectory. Results. Transpedicle surgical devices (probe tool and spine screws) were successfully guided with TREx<2 mm and TREΦ <0.5° given projection views separated by at least >30° (easily accommodated on a mobile C-arm). QA of the surgical product based on 3D-2D registration demonstrated the detection of pedicle screw breach with TREx<1 mm, demonstrating a trend of improved accuracy correlated to the fidelity of the component model employed. Conclusions. 3D-2D registration combined with 3D models of known surgical components provides a novel method for near-real-time guidance and quality assurance using a mobile C-arm without external trackers or fiducial markers. Ongoing work includes determination of optimal views based on component shape and trajectory, improved robustness to anatomical deformation, and expanded preclinical testing in spine and intracranial surgeries.

  11. Does cancellous screw insertion torque depend on bone mineral density and/or microarchitecture?

    PubMed

    Ab-Lazid, Rosidah; Perilli, Egon; Ryan, Melissa K; Costi, John J; Reynolds, Karen J

    2014-01-22

    During insertion of a cancellous bone screw, the torque level reaches a plateau, at the engagement of all the screw threads prior to the screw head contact. This plateau torque (T(Plateau)) was found to be a good predictor of the insertion failure torque (stripping) and also exhibited strong positive correlations with areal bone mineral density (aBMD) in ovine bone. However, correlations between T(Plateau) and aBMD, as well as correlations between T(Plateau) and bone microarchitecture, have never been explored in human bone. The aim of this study was to determine whether T(Plateau), a predictor of insertion failure torque, depends on aBMD and/or bone microarchitecture in human femoral heads. Fifty-two excised human femoral heads were obtained. The aBMD and microarchitecture of each specimen were evaluated using dual X-ray Absorptiometry and micro-computed tomography. A cancellous screw was inserted into specimens using an automated micro-mechanical test device, and T(Plateau) was calculated from the insertion profile. T(Plateau) exhibited the strongest correlation with the structure model index (SMI, R=-0.82, p<0.001), followed by bone volume fraction (BV/TV, R=0.80, p<0.01) and aBMD (R=0.76, p<0.01). Stepwise forward regression analysis showed an increase for the prediction of T(Plateau) when aBMD was combined with microarchitectural parameters, i.e., aBMD combined with SMI (R(2) increased from 0.58 to 0.72) and aBMD combined with BV/TV and BS/TV (R(2) increased from 0.58 to 0.74). In conclusion, T(Plateau), a strong predictor for insertion failure torque, is significantly dependent on bone microarchitecture (particularly SMI and BV/TV) and aBMD.

  12. Error Analysis and Experimental Study of a Bi-Planar Parallel Mechanism in a Pedicle Screw Robot System.

    PubMed

    Duan, Qingjuan; Du, Zhijiang; Yu, Hongjian; Wang, Yongfeng; Dong, Wei

    2016-11-30

    Due to the urgent need for high precision surgical equipment for minimally invasive spinal surgery, a novel robot-assistant system was developed for the accurate placement of pedicle screws in lumbar spinal surgeries. The structure of the robot was based on a macro-micro mechanism, which includes a serial mechanism (macro part) and a bi-planar 5R parallel mechanism (micro part). The macro part was used to achieve a large workspace, while the micro part was used to obtain high stiffness and accuracy. Based on the transfer function of dimension errors, the factors affecting the accuracy of the end effectors were analyzed. Then the manufacturing errors and joint angle error on the position-stance of the end effectors were investigated. Eventually, the mechanism of the strain energy produced by the deformation of linkage via forced assembly and displacements of the output point were calculated. The amount of the transfer errors was quantitatively analyzed by the simulation. Experimental tests show that the error of the bi-planar 5R mechanism can be controlled no more than 1 mm for translation and 1° for rotation, which satisfies the required absolute position accuracy of the robot.

  13. Radiological Evaluation of the Initial Fixation between Cortical Bone Trajectory and Conventional Pedicle Screw Technique for Lumbar Degenerative Spondylolisthesis

    PubMed Central

    Iwatsuki, Koichi; Ohnishi, Yu-Ichiro; Yoshimine, Toshiki

    2016-01-01

    Study Design Retrospective study. Purpose To compare initial fixation using the cortical bone trajectory (CBT) technique versus conventional pedicle screws (PS) in radiographs of postsurgical lumbar degenerative spondylolisthesis. Overview of Literature Few reports have documented the holding strength of CBT technique for spondylolisthesis cases. Methods From October 2009 to June 2014, 21 cases of degenerative spondylolisthesis were surgically treated in our institution. Ten were treated with conventional PS technique and 11 of with CBT technique. Mean lumbar lordosis and percent slippage were evaluated preoperatively, immediately after surgery, and 6 months and 1 year postoperatively using radiographs. We also investigated percent loss of slip reduction. Results There were statistically significant differences between preoperative percent slippage and postoperative slippage in both PS and CBT procedures over 1 year, and both techniques showed good slip reduction. On the other hand, lumbar lordosis did not change significantly in either the PS or CBT groups over 1 year. Conclusions CBT technique showed similarly good initial fixation compared with the PS procedure in the treatment of lumbar degenerative spondylolisthesis. PMID:27114765

  14. Error Analysis and Experimental Study of a Bi-Planar Parallel Mechanism in a Pedicle Screw Robot System

    PubMed Central

    Duan, Qingjuan; Du, Zhijiang; Yu, Hongjian; Wang, Yongfeng; Dong, Wei

    2016-01-01

    Due to the urgent need for high precision surgical equipment for minimally invasive spinal surgery, a novel robot-assistant system was developed for the accurate placement of pedicle screws in lumbar spinal surgeries. The structure of the robot was based on a macro-micro mechanism, which includes a serial mechanism (macro part) and a bi-planar 5R parallel mechanism (micro part). The macro part was used to achieve a large workspace, while the micro part was used to obtain high stiffness and accuracy. Based on the transfer function of dimension errors, the factors affecting the accuracy of the end effectors were analyzed. Then the manufacturing errors and joint angle error on the position-stance of the end effectors were investigated. Eventually, the mechanism of the strain energy produced by the deformation of linkage via forced assembly and displacements of the output point were calculated. The amount of the transfer errors was quantitatively analyzed by the simulation. Experimental tests show that the error of the bi-planar 5R mechanism can be controlled no more than 1 mm for translation and 1° for rotation, which satisfies the required absolute position accuracy of the robot. PMID:27916869

  15. Computer navigation-assisted spinal fusion with segmental pedicle screw instrumentation for scoliosis with Rett syndrome: a case report.

    PubMed

    Tanaka, Masato; Nakanishi, Kazuo; Sugimoto, Yoshihisa; Misawa, Haruo; Takigawa, Tomoyuki; Nishida, Keiichiro; Ozaki, Toshifumi

    2009-12-01

    Scoliosis is a common clinical manifestation of Rett syndrome, a neurodevelopmental disorder that almost exclusively affects females. The spinal curve in patients with Rett syndrome is typically a long C curve of a neuromuscular type. As the onset of the scoliosis is very early and shows rapid progression, early surgical intervention has been recommended to prevent a life-threatening collapsing spine syndrome. However, there are high perioperative risks in Rett syndrome patients who undergo spinal surgery, such as neurological compromise and respiratory dysfunction due to rigid spinal curve. We herein report the surgical result of treating severe rapid progressive thoracic scoliosis in a 16-year-old girl with Rett syndrome. Posterior segmental pedicle screw fixation was performed from T1 to L3 using a computer-assisted technique. Post-operative radiography demonstrated a good correction of the curve in both the sagittal and coronal alignment. There were no postoperative complications such as neurological compromise. The patient had maintained satisfactory spinal balance as of the 3-year follow-up examination.

  16. Morphological study of subaxial cervical pedicles by using three-dimensional computed tomography reconstruction image.

    PubMed

    Wasinpongwanich, Kanthika; Paholpak, Permsak; Tuamsuk, Panya; Sirichativapee, Winai; Wisanuyotin, Taweechok; Kosuwon, Weerachai; Jeeravipoolvarn, Polasak

    2014-01-01

    Malpositioning of cervical screws risks neurovascular injury. A cervical screw fixation system can provide proper rigidity, alignment correction, and high rates of fusion afforded by high pullout biomechanical strength. The objective is to assess the dimensions and axis of the C3-C7 cervical pedicles. A 1-mm slice thickness computed tomography (CT) scan of the cervical spine of 30 patients (15 males, 15 females) were analyzed and reconstructed in three-dimensions using Mimics(®) 10.01 software. We measured pedicle axis length (PAL), pedicle and lateral mass length (PL-LM), pedicle length (PL), outer pedicle width (OPW), and pedicle transverse angle (PTA) from the axial image and outer pedicle height (OPH) and pedicle sagittal angle (PSA) from the sagittal image. The OPH and OPW at all subaxial cervical spines were suitable for insertion of 3.5 mm cervical pedicle screws. PSA was directed cranially at C3 to C5 (13.84, 7.09, and 2.71) and directed caudally at C6 and C7 (-4.55, -6.94). PTA was greatest at C5 and smallest at C7. The respective difference between the left and right side for nearly all parameters was not statistically significant (except for C6 PL and C7 OPH). Females had a significantly smaller OPH and OPW than males at nearly all levels. The PTA was not significantly different between the sexes. Cervical pedicle screw fixation in the Thai population can be safely performed and guidelines for insertion at each vertebra documented. Appropriate preoperative planning is necessary to achieve safe and accurate placement of the screws.

  17. The biomechanical effect of artificial and human bone density on stopping and stripping torque during screw insertion.

    PubMed

    Tsuji, Matthew; Crookshank, Meghan; Olsen, Michael; Schemitsch, Emil H; Zdero, Rad

    2013-06-01

    Orthopedic surgeons apply torque to metal screws manually by "subjective feel" to obtain adequate fracture fixation, i.e. stopping torque, and attempt to avoid accidental over-tightening that leads to screw-bone interface failure, i.e. stripping torque. Few studies have quantified stripping torque in human bone, and only one older study from 1980 reported stopping/ stripping torque ratio. The present aim was to measure stopping and stripping torque of cortical and cancellous screws in artificial and human bone over a wide range of densities. Sawbone blocks were obtained having densities from 0.08 to 0.80g/cm(3). Sixteen fresh-frozen human femurs of known standardized bone mineral density (sBMD) were also used. Using a torque screwdriver, 3.5-mm diameter cortical screws and 6.5-mm diameter cancellous screws were inserted for adequate tightening as determined subjectively by an orthopedic surgeon, i.e. stopping torque, and then further tightened until failure of the screw-bone interface, i.e. stripping torque. There were weak (R=0.25) to strong (R=0.99) linear correlations of absolute and normalized torque vs. density or sBMD. Maximum stopping torques normalized by screw thread area engaged by the host material were 15.2N/mm (cortical screws) and 13.4N/mm (cancellous screws) in sawbone blocks and 20.9N/mm (cortical screws) and 6.1N/mm (cancellous screws) in human femurs. Maximum stripping torques normalized by screw thread area engaged by the host material were 23.4N/mm (cortical screws) and 16.8N/mm (cancellous screws) in sawbone blocks and 29.3N/mm (cortical screws) and 8.3N/mm (cancellous screws) in human femurs. Combined average stopping/ stripping torque ratios were 80.8% (cortical screws) and 76.8% (cancellous screws) in sawbone blocks, as well as 66.6% (cortical screws) and 84.5% (cancellous screws) in human femurs. Surgeons should be aware of stripping torque limits for human femurs and monitor stopping torque during surgery. This is the first study of the

  18. Modified C1 lateral mass screw insertion using a high entry point to avoid postoperative occipital neuralgia.

    PubMed

    Lee, Sun-Ho; Kim, Eun-Sang; Eoh, Whan

    2013-01-01

    For the past decade, a screw-rod construct has been used commonly to stabilize the atlantoaxial joint, but the insertion of the screw through the C1 lateral mass (LM) can cause several complications. We evaluated whether using a higher screw entry point for C1 lateral mass (LM) fixation than in the standard procedure could prevent screw-induced occipital neuralgia. We enrolled 12 consecutive patients who underwent bilateral C1 LM fixation, with the modified screw insertion point at the junction of the C1 posterior arch and the midpoint of the posterior inferior portion of the C1 LM. We measured postoperative clinical and radiological parameters and recorded intraoperative complications, postoperative neurological deficits and the occurrence of occipital neuralgia. Postoperative plain radiographs were used to check for malpositioning of the screw or failure of the construct. Four patients underwent atlantoaxial stabilization for a transverse ligament injury or a C1 or C2 fracture, six patients for os odontoideum, and two patients for C2 metastasis. No patient experienced vertebral artery injury or cerebrospinal fluid leak, and all had minimal blood loss. No patient suffered significant occipital neuralgia, although one patient developed mild, transient unilateral neuralgia. There was also no radiographic evidence of construct failure. Twenty screws were positioned correctly through the intended entry points, but three screws were placed inferiorly (that is, below the arch), and one screw was inserted too medially. When performing C1-C2 fixation using the standard (Harms) construct, surgeons should be aware of the possible development of occipital neuralgia. A higher entry point may prevent this complication; therefore, we recommend that the screw should be inserted into the arch of C1 if it can be accommodated.

  19. Minimally Invasive Unilateral vs. Bilateral Pedicle Screw Fixation and Lumbar Interbody Fusion in Treatment of Multi-Segment Lumbar Degenerative Disorders

    PubMed Central

    Liu, Xiaoyang; Li, Guangrun; Wang, Jiefeng; Zhang, Heqing

    2015-01-01

    Background The choice for instrumentation with minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) in treatment of degenerative lumbar disorders (DLD) remains controversial. The goal of this study was to investigate clinical outcomes in consecutive patients with multi-segment DLD treated with unilateral pedicle screw (UPS) vs. bilateral pedicle screw (BPS) instrumented TLIF. Material/Methods Eighty-four consecutive patients who had multi-level MIS-TLIF were retrospectively reviewed. All data were collected to compare the clinical outcomes between the 2 groups. Results Both groups showed similar clinical function scores in VAS and ODI. The two groups differed significantly in operative time (P<0.001), blood loss (P<0.001), and fusion rate (P=0.043), respectively. Conclusions This study demonstrated similar clinical outcomes between UPS fixation and BPS procedure after MIS-TLIF for multi-level DLD. Moreover, UPS technique was superior in operative time and blood loss, but represented lower fusion rate than the BPS construct did. PMID:26603050

  20. Kinematic Accuracy Analysis of Lead Screw W Insertion Mechanism with Flexibility

    NASA Astrophysics Data System (ADS)

    He, Hu; Zhang, Lei; Kong, Jiayuan

    According to the actual requirements of w insertion, a set of variable lead screw w mechanism was designed, motion characteristics of the mechanism were analyzed and kinematics simulation was carried out with MATLAB. Mechanism precision was analyzed with the analytical method and the error coefficient curve of each component in the mechanism was obtained. Dynamics simulation for rigid mechanism and mechanism with flexibility in different speed was conducted with ADAMS, furthermore, real-time elastic deformation of the flexible Connecting rod was obtained. In consideration of the influences of the elastic connecting rod, the outputs motion error and elastic deformation of components were increased with the speed of the loom.

  1. Accuracy and complications of transpedicular C2 screw placement without the use of spinal navigation.

    PubMed

    Mueller, Christian-Andreas; Roesseler, Lukas; Podlogar, Martin; Kovacs, Attlila; Kristof, Rudolf Andreas

    2010-05-01

    The objective of the study was to describe the technique, accuracy of placement and complications of transpedicular C2 screw fixation without spinal navigation. Patients treated by C2 pedicle screw fixations were identified from the surgical log book of the department. Clinical data were extracted retrospectively from the patients' charts. Pedicle screw placement accuracy was assessed on postoperative CT scans according to Gertzbein and Robbins (GRGr). A total of 27 patients were included in the study. The mean age of the patients was 56 +/- 22.0 years; 51.9% of them were female. As much as 17 patients suffered from trauma, 5 of degenerative disease, 3 of inflammations and 2 of metastatic disease. A total of 47 C2 transpedicular screw fixations were performed. The canulated screws were inserted under visual control following the preparation of the superior surface of the isthmus and of the medial surface of the pedicles of the C2. Intraoperative fluoroscopy was additionally used. The postoperative CT findings showed in 55.3% GRGr 1, in 27.7% GRGr 2, in 10.6% GRGr 3, and in 6.3% GRGr 4 pedicle screw insertion accuracy. Screw insertions GRGr 5 were not observed. Screw malpositioning (i.e., GRGr 3 and 4) was significantly associated with thin (<5 mm) pedicle diameters and with surgery for C2 fractures. In the three patients with screw insertions GRGr 4, postoperative angiographies were performed to exclude vertebral artery affections. In one of these three cases, the screw caused a clinically asymptomatic vertebral artery compression. Hardware failures did not occur. In one patient, postoperative pneumonia resulted in the death of the patient. Careful patient selection and surgical technique is necessary to avoid vertebral artery injury in C2 pedicle screw fixation without spinal navigation. A slight opening of the vertebral artery canal (Gertzbein and Robbins grade < or =3) does not seem to put the artery at risk. However, the high rate of misplaced screws when

  2. Significance of the Pars Interarticularis in the Cortical Bone Trajectory Screw Technique: An In Vivo Insertional Torque Study

    PubMed Central

    Iwatsuki, Koichi; Ohnishi, Yu-Ichiro; Ohkawa, Toshika; Yoshimine, Toshiki

    2016-01-01

    Study Design Retrospective study. Purpose Cortical bone trajectory (CBT), a more medial-to-lateral and shorter path than the traditional one for spinal fusion, is thought to be effective for severely degenerated vertebrae because screws are primarily stabilized at the posterior elements. We evaluated the efficacy of this approach through in vivo insertional torque measurement. Overview of Literature There has been only one prior in vivo study on CBT insertional torque. Methods Between January 2013 and April 2014, a total of 22 patients underwent posterior lumbar fusion using the CBT technique. The maximum insertional torque, which covers the radial strength needed for insertion, was measured for 113 screws, 8 of which were inserted for L5 spondylolysis. The insertional torque for cases with (n=8) and without (n=31) spondylolysis of L5 were compared using one-way analysis of variance (ANOVA). To evaluate vertebral degeneration, we classified 53 vertebrae without spondylolysis by lumbar radiography using semiquantitative methods; the insertional torque for the 105 screws used was compared on the basis of this classification. Additionally, differences in insertional torque among cases grouped by age, sex, and lumbar level were evaluated for these 105 screws using ANOVA and the Tukey test. Results The mean insertional torque was significantly lower for patients with spondylolysis than for those without spondylolysis (4.25 vs. 8.24 in-lb). There were no statistical differences in insertional torque according to vertebral grading or level. The only significant difference in insertional torque between age and sex groups was in men <75 years and women ≥75 years (10 vs. 5.5 in-lb). Conclusions Although CBT should be used with great caution in patient with lysis who are ≥75 years, it is well suited for dealing with severely degenerated vertebrae because the pars interarticularis plays a very important role in the implementation of this technique. PMID:27790318

  3. The Efficacy of Hydroxyapatite for Screw Augmentation in Osteoporotic Patients

    PubMed Central

    Jang, Sang Hoon; Lee, June Ho; Cho, Ji Young; Lee, Ho-Yeon; Lee, Sang-Ho

    2013-01-01

    The stability of screw constructs is of considerable importance in determining the outcome, especially in spinal osteoporosis. Polymethylmethacrylate (PMMA) has been proven as an effective material for increasing the pullout strength of pedicle screws inserted into the osteoporotic bones. However, PMMA has several disadvantages, such as its exothermic properties, the risk of neural injury in the event of extravasation, and difficulties in performing revision surgery. In the current study, we used hydroxyapatite (HA) cement for screw augmentation in spinal osteoporosis. We conclude that HA cement is a useful tool for screw augmentation and recommend it as a promising option for spinal instrumentation in osteoporotic patients. PMID:24201099

  4. [Analysis of the Cochrane Review: Pedicle Screw Fixation for Traumatic Fractures of the Thoracic and Lumbar Spine. Cochrane Database Syst Rev. 2013;05:CD009073].

    PubMed

    Linhares, Daniela; Neves, Nuno; Ribeiro da Silva, Manuel; Almeida Fonseca, João

    2016-05-01

    Traumatic fractures of the thoracic and lumbar spine are common causes of spine surgery. Pedicle screw fixation is usually chosen, using monosegmentar, short or long segment instrumentations, with or without bone graft. This review aims to evaluate the effect of transpedicular fixation in traumatic fractures of the thoracic and lumbar spine. A systematic search on controlled, randomized or quasi-randomized trials comparing different methods of surgical treatment of this fractures was performed, followed by a process of article selection, data extraction and bias assessment by 3 independent authors. Eight articles were included in a total of 5 comparisons, between different transpedicular fixation techniques. No significant differences on function or quality of life, neurologic status or limitation of motion were found. Only instrumentation with fracture level screw incorporation showed significant decrease of pain when compared with instrumentation alone. Several techniques resulted in significant improvements of different radiological parameters. Significantly, surgeries with smaller duration were associated with lesser blood loss. Bone graft use caused a significant raise in post-operative complications, namely donor site pain. So, this paper showed that significative improvements in radiological parameters do not associate with correspondent clinical benefits, and only instrumentation with level screw incorporation is associated with a clear benefit on pain. Moreover, the need for bone graft is questioned, since it leads to no clinic-radiological improvement with a raise of complications. However, a small number of controlled studies is available on this topic.

  5. Augmented PMMA distribution: improvement of mechanical property and reduction of leakage rate of a fenestrated pedicle screw with diameter-tapered perforations.

    PubMed

    Tan, Quan-Chang; Wu, Jian-Wei; Peng, Fei; Zang, Yuan; Li, Yang; Zhao, Xiong; Lei, Wei; Wu, Zi-Xiang

    2016-06-01

    OBJECTIVE This study investigated the optimum injection volume of polymethylmethacrylate (PMMA) to augment a novel fenestrated pedicle screw (FPS) with diameter-tapered perforations in the osteoporotic vertebral body, and how the distribution characteristics of PMMA affect the biomechanical performance of this screw. METHODS Two types of FPSs were designed (FPS-A, composed of 6 perforations with an equal diameter of 1.2 mm; and FPS-B, composed of 6 perforations each with a tapered diameter of 1.5 mm, 1.2 mm, and 0.9 mm from tip to head. Each of 28 human cadaveric osteoporotic vertebrae were randomly assigned to 1 of 7 groups: FPS-A1.0: FPS-A+1.0 ml PMMA; FPS-A1.5: FPS-A+1.5 ml PMMA; FPS-A2.0: FPS-A+2.0 ml PMMA; FPS-B1.0: FPS-B+1.0 ml PMMA; FPS-B1.5: FPS-B+1.5 ml PMMA; FPS-B2.0: FPS-B+2.0 ml PMMA; and conventional pedicle screws (CPSs) without PMMA. After the augmentation, 3D CT was performed to assess the cement distribution characteristics and the cement leakage rate. Axial pullout tests were performed to compare the maximum pullout force thereafter. RESULTS The CT construction images showed that PMMA bone cement formed a conical mass around FPS-A and a cylindrical mass around FPS-B. When the injection volume was increased from 1.0 ml to 2.0 ml, the distribution region of the PMMA cement was enlarged, the PMMA was distributed more posteriorly, and the risk of leakage was increased. When the injection volume reached 2.0 ml, the risk of cement leakage was lower for screws having diameter-tapered perforations. The pullout strengths of the augmented FPS-A groups and FPS-B groups were higher than that of the CPS group (p < 0.0001). All FPS-B groups had a higher pullout strength than the FPS-A groups. CONCLUSIONS The diameter of the perforations affects the distribution of PMMA cement. The diameter-tapered design enabled PMMA to form larger bone-PMMA interfaces and achieve a relatively higher pullout strength, although statistical significance was not reached. Study

  6. A retrospective study to validate an intraoperative robotic classification system for assessing the accuracy of kirschner wire (K-wire) placements with postoperative computed tomography classification system for assessing the accuracy of pedicle screw placements.

    PubMed

    Tsai, Tai-Hsin; Wu, Dong-Syuan; Su, Yu-Feng; Wu, Chieh-Hsin; Lin, Chih-Lung

    2016-09-01

    This purpose of this retrospective study is validation of an intraoperative robotic grading classification system for assessing the accuracy of Kirschner-wire (K-wire) placements with the postoperative computed tomography (CT)-base classification system for assessing the accuracy of pedicle screw placements.We conducted a retrospective review of prospectively collected data from 35 consecutive patients who underwent 176 robotic assisted pedicle screws instrumentation at Kaohsiung Medical University Hospital from September 2014 to November 2015. During the operation, we used a robotic grading classification system for verifying the intraoperative accuracy of K-wire placements. Three months after surgery, we used the common CT-base classification system to assess the postoperative accuracy of pedicle screw placements. The distributions of accuracy between the intraoperative robot-assisted and various postoperative CT-based classification systems were compared using kappa statistics of agreement.The intraoperative accuracies of K-wire placements before and after repositioning were classified as excellent (131/176, 74.4% and 133/176, 75.6%, respectively), satisfactory (36/176, 20.5% and 41/176, 23.3%, respectively), and malpositioned (9/176, 5.1% and 2/176, 1.1%, respectively)In postoperative CT-base classification systems were evaluated. No screw placements were evaluated as unacceptable under any of these systems. Kappa statistics revealed no significant differences between the proposed system and the aforementioned classification systems (P <0.001).Our results revealed no significant differences between the intraoperative robotic grading system and various postoperative CT-based grading systems. The robotic grading classification system is a feasible method for evaluating the accuracy of K-wire placements. Using the intraoperative robot grading system to classify the accuracy of K-wire placements enables predicting the postoperative accuracy of pedicle screw

  7. C7 pars fracture subadjacent to C7 pedicle screw instrumentation at the caudal end of a posterior cervical instrumentation construct.

    PubMed

    Halim, Andrea; Grauer, Jonathan

    2014-07-01

    We report a case of a C7 pars fracture subadjacent to C7 pedicle screw instrumentation at the caudal end of posterior cervical instrumentation construct. To date, posterior cervical instrumentation has been "off label"; however, the US Food and Drug Administration is considering approving label indication of such instrumentation for this common surgical practice. Complications related to the techniques are reported to be relatively low. We know of no previous reports of pars fractures occurring subadjacent to such instrumentation. A 43-year-old man underwent posterior C5-C7 instrumented fusion. Postoperatively, the patient experienced cervical spine injury after a mechanical fall down stairs. Work-up detected bilateral C7 pars fractures subadjacent to the posterior instrumentation construct. After we treated the pars fracture with distal extension of the posterior fusion to the level of T2, the patient progressed to union and marked improvement of initial clinical symptoms that was maintained 2.5 years after posterior instrumentation. To our knowledge, a C7 pars fracture subadjacent to posterior cervical instrumentation construct has not been reported. We hypothesize that the pars may have been vulnerable to fracture because of excessive bone resection during foraminotomy or decortication. This complication was successfully treated by extending the fusion caudally.

  8. Comparative study on thermal performance of helical screw tape inserts in laminar flow using Al 2O 3/water and CuO/water nanofluids

    NASA Astrophysics Data System (ADS)

    Suresh, S.; Venkitaraj, K. P.; Selvakumar, P.

    2011-06-01

    This paper presents a comparison of thermal performance of helical screw tape inserts in laminar flow of Al 2O 3/water and CuO/water nanofluids through a straight circular duct with constant heat flux boundary condition. The helical screw tape inserts with twist ratios Y = 1.78, 2.44 and 3 were used in the experimental study using 0.1% volume concentration Al 2O 3/water and CuO/water nanofluids. Nanofluids with required volume concentration of 0.1% were prepared by dispersing specified amounts of Al 2O 3 and CuO nanoparticles in deionised water. The performance analysis of helical screw tape inserts in laminar flow of Al 2O 3/water and CuO/water nanofluids is done by evaluating thermal performance factor for constant pumping power condition. Thermal performance factor of helical screw tape inserts using CuO/water nanofluid is found to be higher when compared with the corresponding value using Al 2O 3/water. Therefore, the helical screw tape inserts show better thermal performance when used with CuO/water nanofluid than with Al 2O 3/water nanofluid.

  9. A preliminary study of reliability of impedance measurement to detect iatrogenic initial pedicle perforation (in the porcine model).

    PubMed

    Bolger, Ciaran; Carozzo, C; Roger, T; McEvoy, Linda; Nagaria, Jabir; Vanacker, Gerard; Bourlion, Maurice

    2006-03-01

    Accidental perforation of the vertebral pedicle wall is a well-known complication associated with standard approach of pedicle screw insertion. Depending on detection criteria, more than 20% of screws are reported misplaced. Serious clinical consequences, from dysesthesia to paraplegia, although not common, may result from these misplaced screws. Many techniques have been described to address this issue such as somatosensory evoked potentials, electromyography, surgical navigation, etc. Each of these techniques presents advantages and drawbacks, none is simple and ergonomic. A new drilling tool was evaluated which allows for instant detection of pedicle perforation by emission of variable beeps. This new device is based on two original principles: the device is integrated in the drilling or screwing tool, the technology allows real-time detection of perforation through two independent parameters, impedance variation and evoked muscular contractions. A preliminary animal study was conducted to assess the safety and efficacy of this system based upon electrical conductivity. A total of 168 manual pedicle drillings followed by insertion of implants were performed in 11 young porcine lumbar and thoracic spines. The presence or absence of perforation detection, which defines the reliability of the device, was correlated with necropsic examination of the spines. Using this protocol the device demonstrated 100% positive predictive value, 96% negative predictive value, 100% specificity, and 97% sensitivity. Of 168 drillings there were three (1.79%) false-negatives, leading to a minor effraction, cranially in the intervertebral disks, nine (5.36%) screw threads breaching the vertebral cortex when inserting screws, although preparation of the holes did not indicate any perforation, 34 (36%) breaches detected by the instrument and not detected by the surgeon. These results confirm that the impedance variation detection capability of this device offers a simple and effective

  10. Clinical application of a pedicle nail system with polymethylmethacrylate for osteoporotic vertebral fracture

    PubMed Central

    Tanaka, Masato; Sugimoto, Yoshihisa; Takigawa, Tomoyuki; Ozaki, Toshifumi; Konishi, Hitoshi

    2010-01-01

    The instrumentation of the osteoporotic spine may sometimes result in failure due to the loosening or pullout of the conventional pedicle screw. Moreover, augmentation of screws with polymethylmethacrylate (PMMA) has risks of complications. We developed a new and original pedicle nail system with PMMA for osteoporotic vertebral fractures. A clinical evaluation of this novel pedicle nail system utilized in patients with an osteoporotic vertebral collapse was performed to determine the effectiveness and safety of this technique. Thirty-four elderly patients who suffered from osteoporotic compression fractures were treated by posterolateral fusion using the pedicle nail system. The mean follow-up period was 37 months. Of the 25 patients with neurological symptoms, two patients improved two stages at the Frankel level. Fifteen patients improved one stage at the Frankel level, and eight other patients improved, however, their improvement did not exceed a Frankel level. Nine cases with neuralgia symptoms improved from 4.4 to 2.2 points on average on the Denis pain scale (p < 0.01). The fusion rate was 94% as determined by X-rays of flexion and extension, and the correction of the compression fracture site was maintained well. A pedicle nail system stabilizes the spinal column with osteoporosis and reduces the instrumentation failure. The technique for the insertion of the pedicle nail reduces complication from cement augmentation. The authors speculate that the strategy using the pedicle nail system for osteoporotic spine may be effective and safe when the surgery is performed through a posterior approach. PMID:20414689

  11. A novel method of C1–C2 transarticular screw insertion for symptomatic atlantoaxial instability using a customized guiding block

    PubMed Central

    Huang, Kuo-Yuan; Lin, Ruey-Mo; Fang, Jing-Jing

    2016-01-01

    Abstract Atlantoaxial instability treated with the C1-2 transarticular screw fixation is biomechanically more stable; however, the technique demanding and the potential risk of neurovascular injury create difficulties for clinical usage, and there is still lack of clinical experience till now. We reported an adult female patient with symptomatic atlantoaxial instability due to rheumatoid arthritis that was successfully treated with a bilateral C1–C2 transarticular screw fixation using a customized guiding block. We preoperatively determined the trajectories for bilateral C1–C2 transarticular screws on a 3-dimensional reconstruction model from the computed tomography (CT) and self-developed computer software, and designed a rapid prototyping customized guiding block in order to offer a guide for the entry point and insertion angle of the C1–C2 transarticular screws. The clinical outcome was good, and the follow-up period was >3 years. The accuracy of the screws is good in comparison with preoperative and postoperative CT findings, and no neurovascular injury occurred. The patient was accurately and successfully treated with a bilateral C1–C2 transarticular screw fixation using a customized guiding block. PMID:27787362

  12. Experimental studies on heat transfer and friction factor characteristics of laminar flow through a circular tube fitted with regularly spaced helical screw-tape inserts

    SciTech Connect

    Sivashanmugam, P.; Suresh, S.

    2007-02-15

    Experimental investigation of heat transfer and friction factor characteristics of circular tube fitted with full-length helical screw element of different twist ratio, and helical screw inserts with spacer length 100, 200, 300 and 400mm have been studied with uniform heat flux under laminar flow condition. The experimental data obtained are verified with those obtained from plain tube published data. The effect of spacer length on heat transfer augmentation and friction factor, and the effect of twist ratio on heat transfer augmentation and friction factor have been presented separately. The decrease in Nusselt number for the helical twist with spacer length is within 10% for each subsequent 100mm increase in spacer length. The decrease in friction factor is nearly two times lower than the full length helical twist at low Reynolds number, and four times lower than the full length helical twist at high Reynolds number for all twist ratio. The regularly spaced helical screw inserts can safely be used for heat transfer augmentation without much increase in pressure drop than full length helical screw inserts. (author)

  13. Anatomical evaluation of the groove for the vertebral artery in the axis vertebrae for atlanto-axial transarticular screw fixation technique.

    PubMed

    Kazan, S; Yildirim, F; Sindel, M; Tuncer, R

    2000-01-01

    Anatomical measurements were studied on 40 dry axis vertebrae to determine the suitability of the groove for the vertebral artery for atlanto-axial transarticular screw fixation technique. We measured 13 parameters including three angular and 10 linear dimensions related to the groove of the vertebral artery, pedicle, and pars interarticularis and evaluated 80 measurements for each parameter. All measurements were done after placing a Kischner guide wire through the pedicle. We found that differences between measurements on the left and right sides of each vertebra were nonsignificant. In spite of the variability in measurements such as height, width, and median angle of the pedicle, the decline angle for instrumentation, the depth of the groove for the vertebral artery, and the internal height of the pars interarticularis, all of these had good symmetry. However, there were statistically significant differences between the sides in measurements for both the width (P=0.05) and the angle (P<0.02) of the pedicle allowing instrumentation and they did not show good symmetry. The risk of vertebral artery injury was found to be 22.5% per specimen, or 16.25% per screw inserted because the internal height of the pars interarticularis at point of fixation was pedicle width allowing instrumentation was not suitable in 12.5% of screws inserted because their values were pedicle for instrumentation and the internal height of the pars interarticularis were both evaluated together, we also found that this technique would be extremely dangerous in 7.5% of specimens. In conclusion, the internal height of the pars interarticularis and the width of the pedicle for instrumentation should be evaluated together in thin CT sections preoperatively, because of the risk of vertebral artery injury in patients upon which atlanto-axial transarticular screw fixation is to be performed.

  14. Feasibility of C2 Vertebra Screws Placement in Patient With Occipitalization of Atlas: A Tomographic Study.

    PubMed

    Ji, Wei; Liu, Xiang; Huang, Wenhan; Huang, Zucheng; Li, Xueshi; Chen, Jianting; Wu, Zenghui; Zhu, Qingan

    2015-09-01

    Occipitalization of atlas (OA) is a congenital disease with the possibility of anomalous bony anatomies and the C2 pedicle screw insertion is technically challenging. However, there are no existing literatures clarified the dimensions and angulations of the C2 pedicles, lamina and lateral masses for screw insertion in patients with OA. Therefore, the aim of this study was to assess the morphometric features of C2 for screw placement in OA to guide the use of surgical screws. Measurements of the OA patients on the computer tomography (CT) images including lamina angle, length and thickness, pedicle angle, length and thickness, and lateral mass thickness and length of the axis vertebra. The OA patients data were compared with age and gender matched cohort of randomly selected patients in a control group without OA. The picture archiving and communication system was used for all patients who had received cervical CT scanning between January 2001 and January 2015. Measurements were performed independently by 2 experienced observers who reviewed the CT scans and recorded the patients with OA. Statistical analysis was performed at a level of significance P < 0.05. A total of 73 patients (29 males and 44 females) were eligible to be included in the OA group. In most of the measurements the pathological cohort had significantly smaller values compared to the control group (P < 0.05). In the OA group, only 45% of the pedicles and 88% of the lamina had thicknesses bigger than 3.5 mm. Both groups had all pedicle and lamina lengths bigger than 12 mm. Regarding the length of the lateral mass, no value was bigger than 12 mm in the OA group, whereas 40% of the values in the control group were bigger than 12 mm. The average pedicle and laminar angles were 37° and 49° in the patients with OA, respectively. The variable anatomy in patients with OA needs to be taken into account when performing spinal stabilization as the C2 bony architectures are significantly

  15. Feasibility of C2 Vertebra Screws Placement in Patient With Occipitalization of Atlas

    PubMed Central

    Ji, Wei; Liu, Xiang; Huang, Wenhan; Huang, Zucheng; Li, Xueshi; Chen, Jianting; Wu, Zenghui; Zhu, Qingan

    2015-01-01

    Abstract Occipitalization of atlas (OA) is a congenital disease with the possibility of anomalous bony anatomies and the C2 pedicle screw insertion is technically challenging. However, there are no existing literatures clarified the dimensions and angulations of the C2 pedicles, lamina and lateral masses for screw insertion in patients with OA. Therefore, the aim of this study was to assess the morphometric features of C2 for screw placement in OA to guide the use of surgical screws. Measurements of the OA patients on the computer tomography (CT) images including lamina angle, length and thickness, pedicle angle, length and thickness, and lateral mass thickness and length of the axis vertebra. The OA patients data were compared with age and gender matched cohort of randomly selected patients in a control group without OA. The picture archiving and communication system was used for all patients who had received cervical CT scanning between January 2001 and January 2015. Measurements were performed independently by 2 experienced observers who reviewed the CT scans and recorded the patients with OA. Statistical analysis was performed at a level of significance P < 0.05. A total of 73 patients (29 males and 44 females) were eligible to be included in the OA group. In most of the measurements the pathological cohort had significantly smaller values compared to the control group (P < 0.05). In the OA group, only 45% of the pedicles and 88% of the lamina had thicknesses bigger than 3.5 mm. Both groups had all pedicle and lamina lengths bigger than 12 mm. Regarding the length of the lateral mass, no value was bigger than 12 mm in the OA group, whereas 40% of the values in the control group were bigger than 12 mm. The average pedicle and laminar angles were 37° and 49° in the patients with OA, respectively. The variable anatomy in patients with OA needs to be taken into account when performing spinal stabilization as the C2 bony architectures are

  16. A Novel Guidewire Aiming Device to Improve the Accuracy of Guidewire Insertion in Femoral Neck Fracture Surgery Using Cannulated Screw Fixation

    PubMed Central

    Yin, Wenjing; Xu, Haitao; Xu, Peijun; Hu, Tu; An, Zhiquan; Zhang, Changqing; Sheng, Jiagen

    2016-01-01

    Background The aim of this study was to improve the accuracy of guidewire insertion in the femoral neck fracture surgery using cannulated screw fixation. Material/Methods A novel aiming device was designed and manufactured. Between January 2010 and June 2012, 64 femoral neck fracture patients were included into the study. All 64 patients were divided into 2 groups randomly. The aiming device was used during the operation for patients in the experimental group, but not in the control group. Results There were no statistically significant differences in operative time or bleed volume between the groups (P>0.05). The frequency of guidewire drilling was significantly lower in the experimental group than in the control group (P<0.05). The angle between the first cannulated screw and the central axis of the femoral neck in coronal plane and sagittal plane, and the distance between the bottom cannulated screw and the medial calcar femorale rim, were significantly smaller in the experimental group than in the control group (P<0.05). Conclusions The aiming device is simple in structure and easy to use. It could help surgeons to accurately insert cannulated screw guidewires. The aiming device is suitable for broad clinical use. PMID:27529374

  17. Design and fabrication of a low-frequency (1-3 MHz) ultrasound transducer for accurate placement of screw implants in the spine

    NASA Astrophysics Data System (ADS)

    Manbachi, Amir; Lee, Mike; Foster, F. Stuart; Ginsberg, Howard J.; Cobbold, Richard S. C.

    2014-03-01

    In 2012 approximately 800,000 spinal fusion surgeries were performed in the United States, requiring the insertion of screws into the pedicles. Their exact placement is critical and made complex due to limited visibility of the spine, continuous bleeding in the exposed regions, and variability in morphologies. The alarmingly high rate of screw misplacements (up to 20%) reported in the literature is of major concern since such misplacements can place the surrounding vital structures at risk. A potential guidance method for determining the best screw trajectory is by the use of real-time ultrasound imaging similar to that used for intravascular imaging. An endovascular transducer could be inserted into the pedicle to image the anatomy from within and identify bone boundaries. A major challenge of imaging within bone is high signal attenuation. The rapid increase of attenuation with frequency requires much lower frequencies (1-3 MHz) than those used in intravascular imaging. This study describes the custom design and fabrication of 2 MHz ultrasound probes (3.5 mm diameter/ 11 Fr) for pedicle screw guidance. Three transducer designs are explored to provide improved sensitivity and signal to noise ratio, compared to the previously tested transducer within the pedicle. Experimental measurements are compared with the results obtained using various simulation tools. The work reported in this paper represents the first stage in our ultimate goal of developing a 32- element phased array that is capable of generating a radial B-mode image.

  18. Midline Lumbar Fusion with Cortical Bone Trajectory Screw

    PubMed Central

    MIZUNO, Masaki; KURAISHI, Keita; UMEDA, Yasuyuki; SANO, Takanori; TSUJI, Masanori; SUZUKI, Hidenori

    2014-01-01

    A novel cortical bone trajectory (CBT) screw technique provides an alternative fixation technique for lumbar spine. Trajectory of CBT screw creates a caudo-cephalad path in sagittal plane and a medio-lateral path in axial plane, and engages cortical bone in the pedicle. The theoretical advantage is that it provides enhanced screw grip and interface strength. Midline lumbar fusion (MIDLF) is composed of posterior mid-line approach, microsurgical laminectomy, and CBT screw fixation. We adopted the MIDLF technique for lumbar spondylolisthesis. Advantages of this technique include that decompression and fusion are available in the same field, and it minimizes approach-related damages. To determine whether MIDLF with CBT screw is as effective as traditional approach and it is minimum invasive technique, we studied the clinical and radiological outcomes of MIDLF. Our results indicate that MIDLF is effective and minimum invasive technique. Evidence of effectiveness of MIDLF is that patients had good recovery score, and that CBT screw technique was safety in clinical and stable in radiological. MIDLF with CBT screw provides the surgeon with additional options for fixation. This technique is most likely to be useful for treating lumbar spondylolisthesis in combination with midline decompression and insertion of an interbody graft, such as the transforaminal lumbar interbody fusion or posterior lumbar interbody fusion techniques. PMID:25169139

  19. Caudally directed Inferior facetal and transfacetal screws for C1-C2 and C1-2-3 fixation.

    PubMed

    Goel, Atul

    2017-01-13

    An alternative caudally directed C2 inferior facetal screw is described. Such screw insertion can form the axial stabilization point in cases undergoing atlantoaxial lateral mass plate/rod and screw fixation and those undergoing C1-2and C1-2-3 spinal fixation. The C2 screw courses from the medial point of pedicle-laminar junction and travels caudally and laterally towards the C2-3 articulation. Deploying a longer screw that traverses in a transarticular fashion into the facetal mass of C3 vertebra one can perform C1-2-3 stabilization.Sixteen patients underwent C2 inferior facetal or C2-3 transarticular screw in combination with C1 screw for atlantoaxial fixation. Three of these patients with multilevel spinal instability underwent atlantoaxial and C2-3 fixation using the discussed technique. The technical issues, anatomical subtleties and indication for the use of the C2 inferior facetal screws are discussed. With an average follow-up of 9 months, all screws have successfully provided stability that resulted in arthrodesis of the treated spinal segments. Caudally directed C2 inferior facetal screw can enhance the armamentarium of the surgeon, provide an alternative to conventional techniques or a bailout option and add to safety of the procedure of atlantoaxial lateral mass fixation in anatomically challenged situations.

  20. Congenital hypoplasia of the lumbar pedicle with spondylolisthesis: report of 2 cases.

    PubMed

    Hsieh, Chang-Sheng; Lee, Sang-Ho; Lee, Hyung Chang; Oh, Hyeong-Seok; Hwang, Byeong-Wook; Park, Sang-Joon; Chen, Jian-Han

    2017-04-01

    Congenital hypoplasia of the spinal pedicle is a rare condition. Previously reported cases were treated conservatively or with posterior instrumented fusion. However, the absence or hypoplasia of the lumbar pedicle may increase the difficulty of pedicle screw fixation and fusion. Herein, the authors describe 2 cases of rare adult congenital hypoplasia of the right lumbar pedicles associated with spondylolisthesis. The patients underwent anterior lumbar interbody fusion with a stand-alone cage as well as percutaneous pedicle screw fixation. This method was used to avoid the difficulties associated with pedicle screw fixation and to attain solid fusion. Both patients achieved satisfactory outcomes after a minimum of 2 years of follow-up. This method may be an alternative for patients with congenital hypoplasia of the lumbar spinal pedicle.

  1. Comparison Study between Conventional Sequence and Slice-Encoding Metal Artifact Correction (SEMAC) in the Diagnosis of Postoperative Complications in Patients Receiving Lumbar Inter-Body Fusion and Pedicle Screw Fixation Surgery

    PubMed Central

    Han, Sol Bee; Kwon, Jong Won

    2016-01-01

    Background and Purpose Slice-Encoding Metal Artifact Correction (SEMAC) sequence is one of the metal artifact reduction techniques of anatomical structure, but there has been no report about evaluation of post-operative complications. The purpose of this article is to compare the anatomical visibility between fast spin echo (FSE) and FSE-SEMAC and to evaluate the additional value of FSE-SEMAC in diagnostic confidence of the complications. Materials and Methods We conducted a retrospective study with 54 patients who received lumbar spinal surgery and MR images including FSE-SEMAC. For the semi-quantitative evaluation, the visibility of anatomical structures (neural foramen, bone-inter-body cage interface, central canal, nerve root in epidural space, back muscle, and bone-pedicle screw interface) was evaluated. For qualitative evaluation, we evaluated FSE and FSE with FSE-SEMAC independently, and recorded the diagnostic confidence level of post-operative complications. Generalized estimating equation regression analysis was used for statistical analysis, and a weighted kappa was used for inter-observer agreement. Results Scores of 6 imaging findings with FSE-SEMAC were significantly higher than that of FSE (P-value < .0001). Inter-observer agreements show good reliability (weighted kappa = 0.45–0.75). Both reviewers deemed 37 (reviewer 1) or 19 more (reviewer 2) post-operative complications with FSE plus FSE-SEMAC, compared to FSE only. Except for central canal stenosis (P-value = .2408), diagnostic confidence level for other post-operative complications were significantly higher with FSE plus FSE-SEMAC (P-value = .0000) than FSE. Conclusions FSE-SEMAC significantly reduces image distortion, compared to FSE sequence in 3.0-T MR. Also, diagnostic confidence for post-operative complications was higher when FSE with additional FSE-SEMAC compared to FSE only. PMID:27711137

  2. Adjacent-Level Hypermobility and Instrumented-Level Fatigue Loosening With Titanium and PEEK Rods for a Pedicle Screw System: An In Vitro Study.

    PubMed

    Agarwal, Aakas; Ingels, Marcel; Kodigudla, Manoj; Momeni, Narjes; Goel, Vijay; Agarwal, Anand K

    2016-05-01

    Adjacent-level disease is a common iatrogenic complication seen among patients undergoing spinal fusion for low back pain. This is attributed to the postsurgical differences in stiffness between the spinal levels, which result in abnormal forces, stress shielding, and hypermobility at the adjacent levels. In addition, as most patients undergoing these surgeries are osteoporotic, screw loosening at the index level is a complication that commonly accompanies adjacent-level disease. Recent studies indicate that a rod with lower rigidity than that of titanium may help to overcome these detrimental effects at the adjacent level. The present study was conducted in vitro using 12 L1-S1 specimens divided into groups of six, with each group instrumented with either titanium rods or PEEK (polyetheretherketone) rods. The test protocol included subjecting intact specimens to pure moments of 10 Nm in extension and flexion using an FS20 Biomechanical Spine Test System (Applied Test Systems) followed by hybrid moments on the instrumented specimens to achieve the same L1-S1 motion as that of the intact specimens. During the protocol's later phase, the L4-L5 units from each specimen were segmented for cyclic loading followed by postfatigue kinematic analysis to highlight the differences in motion pre- and postfatigue. The objectives included the in vitro comparison of (1) the adjacent-level motion before and after instrumentation with PEEK and titanium rods and (2) the pre- and postfatigue motion at the instrumented level with PEEK and titanium rods. The results showed that the adjacent levels above the instrumentation caused increased flexion and extension with both PEEK and titanium rods. The postfatigue kinematic data showed that the motion at the instrumented level (L4-L5) increased significantly in both flexion and extension compared to prefatigue motion in titanium groups. However, there was no significant difference in motion between the pre- and postfatigue data in the PEEK

  3. Short segment screw fixation without fusion in treatment for unstable thoracolumbar burst fracture.

    PubMed

    Tang, Jiaguang; Liu, Yishan; Cao, Zheng; Hu, Yuan; Lu, Xiang; Lin, Bin

    2014-01-01

    This study aims to evaluate clinical efficacy of short segment pedicle screw fixation without bone fusion for unstable thoracolumbar burst fracture. Nineteen patients younger than 40 years old with unstable thoracolumbar burst fractures were included. The surgical procedure included postural reduction for 3 days and screw fixations at one level above, one level below and at the fractured level itself. The implants were removed 12 months after initial operation. Imaging and clinical findings were analyzed at preoperative, 12 months after surgery, just before implant removal, and at six months after implant removal. Results indicated that difference was statistically significant between preoperative period or postoperative 1 year follow-up, just before implant removal and 6 months after implant removal (P < 0.05). Results at postoperative 1 year follow-up, just before implant removal and 6 months after implant removal were better than preoperative period. There were no significant complications or neurological deterioration after screws insert and removal in any patient. The rate of clinical outcome with excellent and good was 94.7%. In conclusion, short segment pedicle screw fixation without bone fusion can be an effective and safe operative srategytechnique in the management of young patients suffering from unstable burst fracture.

  4. Spondylolisthesis Accompanying Bilateral Pedicle Stress Fracture at Two Vertebrae

    PubMed Central

    Kim, Hyeun Sung; Lee, Won Tae

    2012-01-01

    There has been no report of bilateral pedicle stress fractures involving two vertebrae. The authors describe a unique case of spondylolisthesis accompanying a bilateral pedicle stress fracture involving two vertebrae. De novo development of spondylolisthesis at the L5-S1 vertebrae accompanying a bilateral pedicle stress fracture at L4 and L5 was observed in a 70-year-old woman. The patient's medical history was unremarkable and she did not have any predisposing factors except severe osteoporosis. Interbody fusion with bone cement augmented screw fixation was performed. Surgical treatment resulted in good pain management and improved functional recovery. PMID:22949973

  5. Clear Zone Formation around Screws in the Early Postoperative Stages after Posterior Lumbar Fusion Using the Cortical Bone Trajectory Technique

    PubMed Central

    Iwatsuki, Koichi; Ohnishi, Yu-Ichiro; Ohkawa, Toshika; Yoshimine, Toshiki

    2015-01-01

    Study Design Retrospective study. Purpose To evaluate the initial fixation using the cortical bone trajectory (CBT) technique for posterior lumbar fusion through assessment of the clear zones around the screws and the risk factors involved. Overview of Literature Postoperative radiolucent zones (clear zones) are an indicator of poor conventional pedicle screw fixation. Methods Between January 2013 and April 2014, 19 patients (8 men and 11 women) underwent posterior lumbar interbody fusion or posterior lumbar fusion using the CBT technique. A total of 109 screws were used for evaluation with measurement of the maximum insertional torque of last two screw rotations. Clear zone-positivity on plain radiographs was investigated 6 months after surgery. The relation between intraoperative insertional torque and clear zone-positivity was investigated by one-way analysis of variance. In addition, the correlation between clear zone-positivity and gender, age (<75 years old or >75 years old), or operative stabilization level (<2 or >3 vertebral levels) was evaluated using the chi-square test. Results Clear zones were observed around six screws (5.50%) in five patients (26.3%). The mean insertional torque (4.00±2.09 inlbs) of clear zone-positive screws was lower than that of clear zone-negative screws (8.12±0.50 in-lbs), but the difference was not significant. There was a significant correlation between clear zone-positivity and operative level of stabilization. Conclusions The low incidence of clear zone-positive screws indicates good initial fixation using the CBT technique. Multilevel fusions may be risk factors for clear zone generation. PMID:26713120

  6. Biodegradable Magnesium Screws Accelerate Fibrous Tissue Mineralization at the Tendon-Bone Insertion in Anterior Cruciate Ligament Reconstruction Model of Rabbit.

    PubMed

    Wang, Jiali; Xu, Jiankun; Fu, Weimin; Cheng, Wenxiang; Chan, Kaiming; Yung, Patrick Shu-Hang; Qin, Ling

    2017-01-10

    The incorporation of tendon graft into bone tunnel is one of the most challenging clinical issues in anterior cruciate ligament (ACL) reconstruction. As a biodegradable metal, Mg has appropriate mechanical strength and osteoinductive effects, thus may be a promising alternative to commercialized products used for graft fixation. Therefore, it was hypothesized that Mg based interference screws would promote tendon graft-bone junction healing when compared to Ti screws. Herein, we compared the effects of Mg and Ti screws on tendon graft healing in rabbits with ACL reconstruction via histological, HR-pQCT and mechanical analysis. The histological results indicated that Mg screws significantly improved the graft healing quality via promoting mineralization at the tendon graft enthesis. Besides, Mg screws significantly promoted bone formation in the peri-screw region at the early healing stage. Importantly, Mg screws exhibited excellent corrosion resistance and the degradation of Mg screws did not induce bone tunnel widening. In tensile testing, there were no significant differences in the load to failure, stress, stiffness and absorption energy between Mg and Ti groups due to the failure mode at the midsubstance. Our findings demonstrate that Mg screws can promote tendon graft healing after ACL reconstruction, implying a potential alternative to Ti screws for clinical applications.

  7. Biodegradable Magnesium Screws Accelerate Fibrous Tissue Mineralization at the Tendon-Bone Insertion in Anterior Cruciate Ligament Reconstruction Model of Rabbit

    PubMed Central

    Wang, Jiali; Xu, Jiankun; Fu, Weimin; Cheng, Wenxiang; Chan, Kaiming; Yung, Patrick Shu-hang; Qin, Ling

    2017-01-01

    The incorporation of tendon graft into bone tunnel is one of the most challenging clinical issues in anterior cruciate ligament (ACL) reconstruction. As a biodegradable metal, Mg has appropriate mechanical strength and osteoinductive effects, thus may be a promising alternative to commercialized products used for graft fixation. Therefore, it was hypothesized that Mg based interference screws would promote tendon graft-bone junction healing when compared to Ti screws. Herein, we compared the effects of Mg and Ti screws on tendon graft healing in rabbits with ACL reconstruction via histological, HR-pQCT and mechanical analysis. The histological results indicated that Mg screws significantly improved the graft healing quality via promoting mineralization at the tendon graft enthesis. Besides, Mg screws significantly promoted bone formation in the peri-screw region at the early healing stage. Importantly, Mg screws exhibited excellent corrosion resistance and the degradation of Mg screws did not induce bone tunnel widening. In tensile testing, there were no significant differences in the load to failure, stress, stiffness and absorption energy between Mg and Ti groups due to the failure mode at the midsubstance. Our findings demonstrate that Mg screws can promote tendon graft healing after ACL reconstruction, implying a potential alternative to Ti screws for clinical applications. PMID:28071744

  8. Drill Free Screws: a new form of osteosynthesis screw.

    PubMed

    Heidemann, W; Gerlach, K L; Gröbel, K H; Köllner, H G

    1998-06-01

    Although the application of self-tapping and non self-tapping screws is virtually universal in cranio-maxillofacial surgery, the inevitable, time consuming procedure of drilling a pilot hole has some potential disadvantages, such as damage to nerves, tooth roots or tooth germs, thermal necrosis of the bone and drill bit breakage. Drill Free Screws (DFS) are a recently developed type of osteosynthesis screws, having a tip like a cork screw and specially formed cutting flutes which enable insertion of the screws without drilling. DFS 1.5 and 2 mm were inserted into discs of wood, polyvinylchloride (PVC) and porcine mandibular bone of varying thicknesses between 2 and 4 mm. The values of insertion torque and maximum torque were recorded using an electric torque tester. Thereafter, the screws were inserted with a fixed torque and uniaxial pull out tests were performed. In comparison with this, the same procedure was performed using 1.5 and 2 mm self-tapping titanium screws. Ten trials for each screw-material-combination were conducted to determine insertion torque, maximum torque and pull out analysis. The results showed that the holding power of DFS lay between 70 and 104% of the holding power of self-tapping titanium screws; only in PVC was the difference more than 15%.

  9. The "medio-latero-superior trajectory technique": an alternative cortical trajectory for pedicle fixation.

    PubMed

    Mobbs, Ralph J

    2013-02-01

    An alternative pedicle trajectory for use at the superior end of a construct to limit dissection of the mobile superior facet joint and reduce incision length and muscle dissection, thus minimizing approach-related trauma during pedicle fixation, is reported. The medio-latero-superior trajectory technique involves a starting point on the medial aspect of the pars and angulation of the pedicle screw in a mediolateral and caudocranial direction. This approach takes advantage of a predominantly cortical trajectory to assist with bone fixation. Drawbacks of this new screw trajectory are discussed along with its potential benefits.

  10. Simultaneous anterior and posterior screw fixations confined to the axis for stabilization of a 3-part fracture of the axis (odontoid, dens, and hangman fractures): report of 2 cases.

    PubMed

    Shinbo, Jun; Sameda, Hiroaki; Ikenoue, Sumio; Takase, Kan; Yamaguchi, Takeshi; Hashimoto, Eiko; Enomoto, Takahiro; Kanazuka, Aya; Mimura, Masaya

    2014-03-01

    Fractures of the axis are considered to be one of the most common injuries to the cervical spine, accounting for more than 20% of all cervical spine fractures. Multiple fractures of the axis are much rarer, accounting for 1% of all cervical fractures. Management of such complex fractures is still challenging, and there is no strong consensus for the treatment. The authors describe the cases of 2 patients who presented with 3-part fractures of the axis consisting of an odontoid Type II fracture and a Levine-Edwards Type IA fracture, which were treated with concurrent insertion of an anterior odontoid screw and bilateral posterior pedicle screws. The cases presented were characterized by 1) a Type II odontoid fracture; 2) a Type IA traumatic spondylolisthesis with no or a little translation and angulation of C-2 on C-3 in a ring fracture of the axis; and 3) no disorders at the C2-3 disc on MR images. Therefore, the authors performed surgery confined to the axis by concurrently inserting an anterior odontoid screw and posterior bilateral pedicle screws without arthrodesis of C2-3. This was followed with cervical soft collar fixation for only 1-2 weeks. The outcomes were favorable, including good osteosynthesis, high primary stability, early patient mobilization, and preserved range of motion of the cervical spine at C2-3 as well as at C1-2.

  11. Unilateral Pedicle Stress Fracture in a Long-Term Hemodialysis Patient with Isthmic Spondylolisthesis

    PubMed Central

    Maruo, Keishi; Tachibana, Toshiya; Inoue, Shinichi; Arizumi, Fumihiro; Yoshiya, Shinichi

    2015-01-01

    Most unilateral pedicle stress fractures occur on the contralateral side of patients with unilateral spondylolysis. However, there are few reports of unilateral pedicle stress fractures in patients with bilateral spondylolysis and spondylolisthesis. We report a unique case of unilateral pedicle stress fracture in a long-term hemodialysis patient with isthmic spondylolisthesis. A 65-year-old man who had undergone hemodialysis presented with lower back pain that had persisted for several years. The patient experienced severe right lower extremity pain with no history of trauma. Computed tomography revealed unilateral pedicle fracture with bilateral L5 spondylolysis and spondylolisthesis with progression of scoliosis. The patient underwent Gill laminectomy of L5 with pedicle screw fixation at L4-S1 and interbody fusion at L5-S1. The patient's leg pain ceased immediately, and he began walking without leg pain. In our present patient, development of scoliosis caused by destructive spondyloarthropathy may have contributed to a unilateral pedicle fracture. PMID:25737789

  12. The USS pedicle hook system: a morphometric analysis of its safety in the thoracic spine. Universal Spine System.

    PubMed

    Berlet, G C; Boubez, G; Gurr, K R; Bailey, S I

    1999-06-01

    The Universal Spine System (USS) pedicle hook design includes a fixation screw that passes obliquely in the anterocranial direction in the pedicle. The addition of the fixation screw was to address concerns with rotation of the hook and hook disengagement. This study was designed to evaluate the safety of the USS screw locked pedicle hook. Eleven cadaveric thoracic spines were instrumented posteriorly with USS pedicle hooks from T1 to T12. Spinal instrumentation was performed by a spinal surgeon experienced with the USS system. Spinal deformity was created prior to instrumentation, ranging from 0 to 55 degrees in the horizontal plane (rotation) and from 0 to 50 degrees in the frontal plane (scoliosis). Radiographs, computed tomography (CT), and segmental dissection were used for data acquisition. Morphometric CT analysis before instrumentation demonstrated that the transverse pedicular diameter was the smallest at T5 with a mean of 3.7 mm. The transverse pedicular angle (TPA) was found to always point toward the midline. The largest TPA was observed at T1 with a mean TPA of 28.4 degrees. The pedicle with the least angular deviation from the midline was T11 with a mean TPA of 7 degrees. Postinstrumentation CT analysis and segmental dissection revealed perforations of the pedicle cortex by the fixation screw in 15% of instrumented pedicles (26/172). There were 6 medial and 20 lateral perforations. Medial perforations occurred exclusively in the three most proximal spinal segments, whereas the lateral perforations occurred throughout the thoracic spine. The mean encroachment of the fixation screw was 1.67 mm medially and 1.95 mm laterally. This study demonstrates the variation in caliber and direction of the thoracic pedicles. Medial and lateral perforations of the pedicle can occur with the USS pedicle hook instrumented system.

  13. A novel indication for a method in the treatment of lumbar tuberculosis through minimally invasive extreme lateral interbody fusion (XLIF) in combination with percutaneous pedicle screws fixation in an elderly patient

    PubMed Central

    Wang, Qiyou; Xu, Yichun; Chen, Ruiqiang; Dong, Jianwen; Liu, Bin; Rong, Limin

    2016-01-01

    Abstract Rationale: To describe a novel indication for a method through minimally invasive extreme lateral interbody fusion (XLIF) in combination with percutaneous pedicle screwsfixation in the treatment of lumbar tuberculosis (TB) in an elderly patient, and its clinical efficacy and feasibility. Lumbar TB is a destructive form of TB. Antituberculous treatment should be started as early as possible. In some circumstances, however, surgical debridement with or without stabilization of the spine appears to be beneficial and may be recommended. Surgeries through the approach of anterior or posterior are still challenging and often involve some complications. Patient concerns: The case is a 68-year-old female who was misdiagnosed as simple vertebral compression fracture and underwent L1 and L2 percutaneous vertebroplasty in another hospital 7 years ago. He complained of lumbosacral pain for 1 month this time. Magnetic resonance imaging (MRI) and computed tomography (CT) showed intervertebral space in L1/2 was seriously damaged like TB. Diagnoses: Lumbar tuberculosis Interventions: Antitubercular drugs, mini-invasive debridement with XLIF in combination with percutaneous pedicle screwsfixation was performed. This patient was followed up for 12 months. Outcomes: No obvious complication occurred during the operation and the wound healed well. Oswestry Disability Index (ODI: 56 vs 22) and visual analog scale (VAS: 4 vs 0) score significantly decreased atfinal follow-up of 12 months. Obvious recovery of kyphosis angle was found postoperatively (post: 14.8° vs pre: 33.5°). No recurrent infection occurred at the last follow-up. Lessons: Mini-invasive surgery by debridement through XLIF and percutaneous pedicle screwsfixation may be an effective and innovative treatment method for lumbar TB in the elderly. PMID:27902591

  14. Role of rod diameter in comparison between only screws versus hooks and screws in posterior instrumentation of thoracic curve in idiopathic scoliosis.

    PubMed

    Lamartina, Claudio; Petruzzi, Maria; Macchia, Marcello; Stradiotti, Paola; Zerbi, Alberto

    2011-05-01

    Since the introduction of Cotrel-Dubousset instrumentation in 1984, the correction techniques in scoliosis surgery have changed from Harrington principles of concave distraction to segmental realignment to a variety of possibilities including the rod rotation manoeuvres, and to segmental approximation via cantilever methods. Additionally, pedicle screw utilization in lumbar curves enhanced correction and stabilization of various deformities, and various studies have strongly supported the clinical advantages of lumbar pedicle screws versus conventional hook instrumentation. Pedicle screw constructs have become increasingly popular in the treatment of patients with spinal deformity. When applied to adolescent idiopathic scoliosis patients, pedicle screw fixation has demonstrated increased corrective ability compared with traditional hook/hybrid instrumentation. In our study, we do a retrospective review of idiopathic scoliosis patients (King 2-Lenke 1 B/C) treated with a selective thoracic posterior fusion using an all-screw construct versus a hybrid (pedicle screws and hooks) construct and, compare the percentage of correction of the scoliotic curves obtained with screws alone and screws and hooks. Special attention was given to the rod diameter and correction technique. Our results show that the percentage of correction of idiopathic thoracic scoliosis is similar when treating the scoliosis with rods and screws alone or with rods, screws and hooks; therefore, we and the majority of authors in the literature do not consider the rod section. This can be an important parameter in the evaluation of the superiority of treatment with screws only or screws and hooks. In our study, even if not of statistical significance, the better thoracic curve correction obtained with the hybrid group should be ascribed to the fact that in this group mostly 6 mm rods were used.

  15. A pedicled muscle flap based solely on a neural pedicle.

    PubMed

    Avci, Gulden; Akan, Mithat; Akoz, Tayfun; Kuzon, William; Gul, Aylin Ege

    2009-01-01

    We tested the hypothesis that the intrinsic vascular plexus of the motor nerve could support viability in a rat hindlimb muscle flap. In a preliminary study, we examined the course and vascularity of the sciatic nerve, the peroneal nerve, and the peroneous longus muscle in the rat hindlimb via anatomic dissection, microangiography, and histologic study (n = 10 animals). On the basis of this examination, the peroneous longus muscle was chosen as our experimental model in this study. In 12 animals, the peroneus longus was acutely elevated, which severed all tendinous and vascular structures, this left the muscle pedicled on the motor nerve only (Group I). Animals in Group II underwent a staged elevation of the flap with division of the vascular pedicle, the tendon of insertion, and the tendon of origin during separate procedures that were 5 days apart (n = 12). Muscle viability was evaluated by gross inspection, measurement of muscle weight and length, nitroblue tetrazlium (NBT) staining, microangiography, and histology. NBT staining demonstrated that immediate elevation of the peroneus longus muscle flaps led to an average necrotic area of 80.6% +/- 9.8% (Group I). A significant improvement in viability was observed for muscle flaps of animals in Group II, with peroneus longus muscle necrosis averaging 25.6% +/- 9.3%. Microangiography demonstrated that the intrinsic vascularity of nerve was increased dramatically in Group II. These data support the hypothesis that the intrinsic vascular plexus of the motor nerve of a skeletal muscle can support at least partial viability of a muscle flap. However, this vascular axis is inadequate to support complete viability of a muscle flap if the flap is elevated immediately. If a staged elevation affects a surgical delay, the viability of a muscle flap elevated on a neural pedicle can be increased significantly. With adjustments in the delay procedure, this strategy may allow transfer of muscle flaps when maintenance or

  16. Translaminar screws of the axis--an alternative technique for rigid screw fixation in upper cervical spine instability.

    PubMed

    Meyer, D; Meyer, F; Kretschmer, Th; Börm, W

    2012-04-01

    C2 pedicle screws or transarticular atlantoaxial screws are technically demanding and carry an increased risk of vertebral artery injury. In up to 20% of cases, pedicle and transarticular screw placement is not possible due to a high-riding vertebral artery or very small C2 pedicles in addition to other anatomical variations. Translaminar screws have been reported to rigidly capture posterior elements of C2 and therefore appear to be a suitable alternative. We present our first experiences and clinical results with this new method in two neurosurgical spine centers. Twenty-seven adult patients were treated between 2007 and 2010 in two neurosurgical spine departments with C2 translaminar screw fixation for upper cervical spine instability of various origins (e.g., trauma, tumor, dens pseudarthrosis). Eight patients were men and 19 were women. Mean age was 68.9 years. In most cases, translaminar screws were used because of contraindications for pedicle or transarticular screws as a salvage technique. All patients were clinically assessed and had CT scans postoperatively to verify correct screw placement. Follow-up was performed with reexamination on an ambulatory basis. Mean follow-up was 7.6 months for all patients. In 27 patients, 52 translaminar screws were placed. There were no intraoperative complications. Postoperatively, we identified four screw malpositions using a new accuracy grading scale. One screw had to be revised because of violation of the spinal canal >4 mm. None of the patients had additional neurological deficits postoperatively, and all showed stable cervical conditions at follow-up. Two patients died due to causes not associated with the stabilization technique. The fusion rate for patients with C1/C2 fixation is 92.9%. Translaminar screws can be used at least as an additional technique for cases of upper cervical spine instability when pedicle screw placement is contraindicated or not possible. The current data suggest comparable

  17. Electrical conductivity measurement: a new technique to detect iatrogenic initial pedicle perforation.

    PubMed

    Bolger, Ciaran; Kelleher, Michael O; McEvoy, Linda; Brayda-Bruno, M; Kaelin, A; Lazennec, J-Y; Le Huec, J-C; Logroscino, C; Mata, P; Moreta, P; Saillant, G; Zeller, R

    2007-11-01

    Pedicle screw fixation has achieved significant popularity amongst spinal surgeons for both single and multi-level spinal fusion. Misplacement and pedicle cortical violation occurs in over 20% of screw placement and can result in potential complications such as dysthesia, paraparesis or paraplegia. There have been many advances in techniques available for navigating through the pedicle; however, these techniques are not without drawbacks. A new electrical conductivity-measuring device, previously evaluated on the porcine model to detect the pedicle violation, was evaluated amongst nine European Hospitals to be used in conjunction with the methods currently used in that centre. This new device is based on two original principles; the device is integrated in the drilling or screwing tool. The technology allows real-time detection of perforation through two independent parameters, impedance variation and evoked muscle contractions. Data was collected twofold. Initially, the surgeon was given the device and a comparison was made between the devices ability to detect a breech and the surgeon's ability to detect one using his traditional methods of pedicle preparation. In the second module of the study, the surgeon was limited to using the electrical conductivity detection device as their sole guide to detect pedicle breaches. A comparison was made between the detection ability of the device and the other detection possibilities. Post-operative fine cut CT scanning was used to detect the pedicle breaches. Overall, the 11 trial surgeons performed a total of 521 pedicle drillings on 97 patients. Initially there were 147 drillings with 23 breaches detected. The detection rate of these breaches were 22/23 for the device compared to 10/23 by the surgeon. Over both parts of the study 64 breaches (12.3%) were confirmed on post-operative CT imaging. The electrical conductivity detection device detected 63 of the 64 breaches (98.4%). There was one false negative and four false

  18. Anterograde Fixation Module for Posterior Acetabular Column Fracture: Computer-Assisted Determination of Optimal Entry Point, Angle, and Length for Screw Insertion

    PubMed Central

    Xu, Yongqiang; Lin, Chuangxin; Zhang, Lifeng; Lin, Miaoxiong; Lai, Jianqiang; Cao, Shenglu; Peng, Geng; Feng, Kai; Yan, Ge; Cai, Daozhang; Wang, Gang

    2016-01-01

    Background The aim of this study was to provide valid data for a plate-screw fixation model for fractured posterior-anterior columns of the acetabulum. Material/Methods Nineteen cadaveric bony hemi-pelvis specimens were obtained and 50 healthy adults were enrolled. The modified Stoppa approach and computed tomography (CT) imaging were used to collect the measured parameter data of the module. Results The measured parameter data were as follows: OP, 0.96±0.32 cm in females and 0.92±0.16 cm in males (P>0.05); PI, 0.98±0.28 cm in females, and 0.75±0.23 cm in males (P>0.05); ∠θ, 59.68°±6.28° in females and 56.75°±3.22° in males (P>0.05); and ∠ϕ, 41.27°±2.76° in females and 34.31°±2.78° in males (P<0.05). The corresponding CT image data were as follows: PI, 1.08±0.22 cm in females and 0.85±0.27 cm in males (P>0.05); OP, 1.06±0.29 cm in females and 1.12±0.24 cm in males (P>0.05); ∠θ, 55.33°±4.00° in females and 55. 50°±3.43° in males (P>0.05); and ∠ϕ was 39.21°±2.45°in females and 35.58°±2.31°in males (P<0.05). No significant difference with respect to sex and side existed between specimens and healthy adults (P>0.05). Conclusions The measured parameter data obtained in healthy adults and cadaveric specimens provided an anatomic basis for the designation of the guide module, and thus confirmed the accuracy and safety of screw placement in fractured columns of the acetabulum. PMID:27584820

  19. Relative effectiveness of electrically- vs mechanically-elicited EMGs in detecting pedicle wall perforation and surgically-induced nerve root damage.

    PubMed

    Kobara, N; Owen, J H; Kostuik, J; Huckell, C; Tooke, S M

    2000-02-01

    Electrical stimulation of a pedicle hole and screw with recording EMGs from the lower extremities has been used as an indicator in detecting perforations of the pedicle. Mechanically-elicited EMGs are reported to be sensitive to mechanical irritation of nerve roots. This study analyzed the sensitivity of the data elicited by two EMG monitoring methods in the presence of a neurologic deficit caused by a malpositioned screw to determine the relative effectiveness of electrically- vs mechanically-elicited EMGs in detecting pedicle wall perforations and nerve root damage in patients undergoing spinal surgery utilizing transpedicular instrumentation. One hundred and four surgeries were monitored using the two EMG methods. Six hundred and fifty-four pedicle holes were prepared and 650 placed pedicle screws were electrically tested. Mechanically-elicited EMGs were monitored from a total of 618 muscles. Electrically-elicited EMGs showed a 62% true-positive rate and a 0.2% false-negative rate in detecting pedicle wall perforations. None of the patients who initially demonstrated abnormal electrically-elicited EMGs demonstrated any post-operative neurologic problems due to an incorrect screw placement. Only one patient who had abnormal mechanically-elicited EMGs during the procedures related to instrumentation developed new L4 radiculopathy immediately post-operatively which was consistent with the level of mechanically-elicited EMGs. Mechanically-elicited EMGs showed a 100% true-positive rate for nerve root irritation and a 3.5% false-negative rate in detecting pedicle wall perforations by malpositioned screw. In conclusion, although mechanically-elicited EMGs were an insensitive technique in detecting a perforation of the pedicle, mechanically-elicited EMGs were more beneficial than electrically-elicited EMGs in detecting the risk of nerve root irritation.

  20. Minimally Invasive Technique for PMMA Augmentation of Fenestrated Screws

    PubMed Central

    Kogias, Evangelos; Sircar, Ronen; Krüger, Marie T.; Volz, Florian; Scheiwe, Christian; Hubbe, Ulrich

    2015-01-01

    Purpose. To describe the minimally invasive technique for cement augmentation of cannulated and fenestrated screws using an injection cannula as well as to report its safety and efficacy. Methods. A total of 157 cannulated and fenestrated pedicle screws had been cement-augmented during minimally invasive posterior screw-rod spondylodesis in 35 patients from January to December 2012. Retrospective evaluation of cement extravasation and screw loosening was carried out in postoperative plain radiographs and thin-sliced triplanar computed tomography scans. Results. Twenty-seven, largely prevertebral cement extravasations were detected in 157 screws (17.2%). None of the cement extravasations was causing a clinical sequela like a new neurological deficit. One screw loosening was noted (0.6%) after a mean follow-up of 12.8 months. We observed no cementation-associated complication like pulmonary embolism or hemodynamic insufficiency. Conclusions. The presented minimally invasive cement augmentation technique using an injection cannula facilitates convenient and safe cement delivery through polyaxial cannulated and fenestrated screws during minimally invasive screw-rod spondylodesis. Nevertheless, the optimal injection technique and design of fenestrated screws have yet to be identified. This trial is registered with German Clinical Trials DRKS00006726. PMID:26075297

  1. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ..., including alloys such as 316L stainless steel, 316LVM stainless steel, 22Cr-13Ni-5Mn stainless steel, Ti-6Al-4V, and unalloyed titanium, that allow the surgeon to build an implant system to fit the patient's anatomical and physiological requirements. Such a spinal implant assembly consists of a combination...

  2. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ..., including alloys such as 316L stainless steel, 316LVM stainless steel, 22Cr-13Ni-5Mn stainless steel, Ti-6Al-4V, and unalloyed titanium, that allow the surgeon to build an implant system to fit the patient's anatomical and physiological requirements. Such a spinal implant assembly consists of a combination...

  3. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... spondylolisthesis with objective evidence of neurologic impairment; fracture; dislocation; scoliosis; kyphosis... with objective evidence of neurologic impairment, fracture, dislocation, scoliosis, kyphosis,...

  4. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... spondylolisthesis with objective evidence of neurologic impairment; fracture; dislocation; scoliosis; kyphosis... with objective evidence of neurologic impairment, fracture, dislocation, scoliosis, kyphosis,...

  5. 21 CFR 888.3070 - Pedicle screw spinal system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... spondylolisthesis with objective evidence of neurologic impairment; fracture; dislocation; scoliosis; kyphosis... with objective evidence of neurologic impairment, fracture, dislocation, scoliosis, kyphosis,...

  6. Spline screw autochanger

    NASA Astrophysics Data System (ADS)

    Vranish, John M.

    1993-06-01

    A captured nut member is located within a tool interface assembly and being actuated by a spline screw member driven by a robot end effector. The nut member lowers and rises depending upon the directional rotation of the coupling assembly. The captured nut member further includes two winged segments which project outwardly in diametrically opposite directions so as to engage and disengage a clamping surface in the form of a chamfered notch respectively provided on the upper surface of a pair of parallel forwardly extending arm members of a bifurcated tool stowage holster which is adapted to hold and store a robotic tool including its end effector interface when not in use. A forward and backward motion of the robot end effector operates to insert and remove the tool from the holster.

  7. Range of motion, sacral screw and rod strain in long posterior spinal constructs: a biomechanical comparison between S2 alar iliac screws with traditional fixation strategies

    PubMed Central

    Field, Antony; Ferrara, Lisa A.; Freeman, Andrew L.; Phan, Kevin

    2016-01-01

    Background S1 screw failure and L5/S1 non-union are issues with long fusions to S1. Improved construct stiffness and S1 screw offloading can help avoid this. S2AI screws have shown to provide similar stiffness to iliac screws when added to L3–S1 constructs. We sought to examine and compare the biomechanical effects on an L2–S1 pedicle screw construct of adding S2AI screws, AxiaLIF, L5–S1 interbody support via transforaminal lumbar interbody fusion (TLIF), and to examine the effect of the addition of cross connectors to each of these constructs. Methods Two S1 screws and one rod with strain gauges (at L5/S1) were used in L2–S1 screw-rod constructs in 7 L1-pelvis specimens (two with low BMD). ROM, S1 screw and rod strain were assessed using a pure-moment flexibility testing protocol. Specimens were tested intact, and then in five instrumentation states consisting of: (I) Pedicle screws (PS) L2–S1; (II) PS + S2AI screws; (III) PS + TLIF L5/S1; (IV) PS + AxiaLIF L5/S1; (V) PS + S2AI + AxiaLIF L5/S1. The five instrumentation conditions were also tested with crosslinks at L2/3 and S1/2. Tests were conducted in flexion-extension, lateral bending and axial torsion with no compressive preload. Results S2A1 produces reduced S1 screw strain for flexion-extension, lateral bending and axial torsion, as well as reduced rod strain in lateral bending and axial torsion in comparison to AxiaLIF and interbody instrumentation, at the expense of increased rod flexion-extension strain. Cross-connectors may have a role in further reduction of S1 screw and rod strain. Conclusions From a biomechanical standpoint, the use of the S2AI technique is at least equivalent to traditional iliac screws, but offers lower prominence and ease of assembly compared to conventional sacroiliac stabilization. PMID:28097243

  8. Congenitally absent lumbar pedicle: a reappraisal

    SciTech Connect

    Wortzman, G.; Steinhardt, M.I.

    1984-09-01

    Three patients who had a diagnosis of congenitally absent lumbar pedicle underwent CT examination. Findings showed that each patient had an aberrant hypoplastic pedicle plus a retroisthmic defect in their ipsilateral lamina rather than an absent pedicle. Axial CT was the diagnostic modality of choice; reformated images were of little value. The differential diagnosis to be considered from the findings of plain film radiography includes pediculate thinning, neoplastic disease, neurofibroma, mesodermal dysplasia associated with neurofibromatosis, and vascular anomalies.

  9. Z-2 Threaded Insert Design and Testing

    NASA Technical Reports Server (NTRS)

    Ross, Amy; Rhodes, Richard; Jones, Robert J.; Graziosi, David; Ferl, Jinny; Sweeny, Mitch; Scarborough, Stephen

    2016-01-01

    NASA's Z-2 prototype space suit contains several components fabricated from an advanced hybrid composite laminate consisting of IM10 carbon fiber and fiber glass. One requirement was to have removable, replaceable helicoil inserts to which other suit components would be fastened. An approach utilizing bonded in inserts with helicoils inside of them was implemented. During initial assembly, cracking sounds were heard followed by the lifting of one of the blind inserts out of its hole when the screws were torqued. A failure investigation was initiated to understand the mechanism of the failure. Ultimately, it was determined that the pre-tension caused by torqueing the fasteners is a much larger force than induced from the pressure loads of the suit which was not considered in the insert design. Bolt tension is determined by dividing the torque on the screw by a k value multiplied by the thread diameter of the bolt. The k value is a factor that accounts for friction in the system. A common value used for k for a non-lubricated screw is 0.2. The k value can go down by as much as 0.1 if the screw is lubricated which means for the same torque, a much larger tension could be placed on the bolt and insert. This paper summarizes the failure investigation that was performed to identify the root cause of the suit failure and details how the insert design was modified to resist a higher pull out tension.

  10. Screw fixation for atlantoaxial dislocation related to Down syndrome in children younger than 5 years.

    PubMed

    Ito, Kenyu; Imagama, Shiro; Ito, Zenya; Ando, Kei; Kobayashi, Kazuyoshi; Hida, Tetsuro; Ishikawa, Yoshimoto; Ishiguro, Naoki

    2017-01-01

    The aim of this study was to present cases of upper cervical fixation in Down syndrome patients younger than 5 years. In two cases, C1 lateral mass screws were installed. However, owing to the irreducible atlantoaxial dislocation, the screw backed out and fractured. Therefore, O-C2 fusion was performed. Furthermore, C2 bilateral lamina screws were added to the C2 pedicle screw for reinforcement. C1-C2 fusion is an option for Down syndrome patients younger than 5 years with atlantoaxial dislocation, when the dislocation is reducible. If the dislocation is irreducible, or the implant cannot be firmly secured, the fixation range should be expanded to O-C2 or below.

  11. Lumbo-sacro-pelvic Fixation Using Iliac Screws for the Complex Lumbo-sacral Fractures.

    PubMed

    Rhee, Woo-Tack; You, Seung-Hoon; Jang, Yeon-Gyu; Lee, Sang-Youl

    2007-12-01

    Fractures of lumbo-sacral junction involving bilateral sacral wings are rare. Posterior lumbo-sacral fixation does not always provide with sufficient stability in such cases. Various augmentation techniques including divergent sacral ala screws, S2 pedicle screws and Galveston rods have been reported to improve lumbo-sacral stabilization. Galveston technique using iliac bones would be the best surgical approach especially in patients with bilateral comminuted sacral fractures. However, original Galveston surgery is technically demanding and bending rods into the appropriate alignment is time consuming. We present a patient with unstable lumbo-sacral junction fractures and comminuted U-shaped sacral fractures treated by lumbo-sacro-pelvic fixation using iliac screws and discuss about the advantages of the iliac screws over the rod system of Galveston technique.

  12. Lateral mass screw stimulation thresholds in posterior cervical instrumentation surgery: a predictor of medial deviation.

    PubMed

    Wilson, Bayard; Curtis, Erik; Hirshman, Brian; Oygar, Ahmet; Chen, Karen; Gabel, Brandon C; Vaida, Florin; Allison, David W; Ciacci, Joseph D

    2017-03-01

    OBJECTIVE Normative data exists for stimulus-evoked pedicle screw electromyography (EMG) current thresholds in the lumbar spine, and is routinely referenced during spine surgeries to detect a screw breach, prevent injury of neural elements, and ensure the most biomechanically sound instrumentation construct. To date, similar normative data for cervical lateral mass screws is limited, thus the utility of lateral mass screw testing remains unclear. To address this disparity, in this study the authors describe cumulative lateral mass screw stimulation threshold data in patients undergoing posterior cervical instrumentation with lateral mass screws. These data are correlated with screw placement on postoperative imaging, and a novel correlation is discovered with direct clinical implications. METHODS Using a ball-tip probe, 154 lateral mass screws in 21 patients were electrically tested intraoperatively. In each case, for each screw, the lowest (or threshold) current at which the first polyphasic stimulus-evoked EMG response was reproducibly observed by a neurophysiologist was recorded. All patients underwent postoperative CT. Screw position within the lateral mass was first measured in the axial and sagittal planes for each lateral mass screw using the CT images. Screw placement was also evaluated by 2 independent physicians, blinded to current threshold data, on a binary scale of acceptability. The predictive capacity of screw EMG threshold data was evaluated via multivariable regression analyses and receiver operating characteristic (ROC) analyses. Predictive capacity was examined with respect to screw position within the lateral mass, as well as screw acceptability. RESULTS Lateral mass screw EMG thresholds did not appear to differ significantly for screws considered "acceptable" versus "unacceptable" according to the radiographic criteria. Accordingly, ROC analysis confirmed that EMG current threshold data were of minimal utility in predicting screw radiographic

  13. “Two-step” technique with OsiriX™ to evaluate feasibility of C2 pedicle for surgical fixation

    PubMed Central

    Marques, Luis Miguel Sousa; d’Almeida, Gonçalo Neto; Cabral, José

    2016-01-01

    Background: Surgical treatment of craniovertebral junction pathology has evolved considerably in recent decades with the implementation of short atlanto-axial fixation techniques, notwhithstanding increasing neurovascular risks. Also, there is strong evidence that fixation of C2 anatomical pedicle has the best biomechanical profile of the entire cervical spine. However, it is often difficult and misleading, to evaluate anatomical bony and vascular anomalies using the three orthogonal planes (axial, coronal, and sagittal) of CT. Objectives: The authors describe an innovative and simple technique to evaluate the feasibility of C2 pedicle for surgical screw fixation using preoperative planning with the free DICOM (Digital Imaging and Communications in Medicine) software OsiriX™. Materials and Methods: The authors report the applicatin of this novel technique in 5 cases (3 traumatic, 1 Os Odontoideum, and 1 complex congenital malformation) collected from our general case series of the Department in the last 5 years. Results: In this proof of concept study, the pre-operative analysis with the two-step tecnique was detrimental for choosing the surgical tecnique. Detailed post-operative analysis confirmed correct position of C2 screws without cortical breach. There were no complications or mortality reported. Conclusion: This two-step technique is an easy and reliable way to determine the feasibility of C2 pedicle for surgical fixation. The detailed tridimensional radiological preoperative evaluation of craniovertebral junction anatomy is critical to the sucess and safety of this surgeries, and can avoid, to certain degree, expensive intra-operative tridimensional imaging facilities. PMID:27217652

  14. Accuracy Assessment of Using Rapid Prototyping Drill Templates for Atlantoaxial Screw Placement: A Cadaver Study

    PubMed Central

    Guo, Shuai; Lu, Teng; Hu, Qiaolong; Yang, Baohui; He, Xijing

    2016-01-01

    Purpose. To preliminarily evaluate the feasibility and accuracy of using rapid prototyping drill templates (RPDTs) for C1 lateral mass screw (C1-LMS) and C2 pedicle screw (C2-PS) placement. Methods. 23 formalin-fixed craniocervical cadaver specimens were randomly divided into two groups. In the conventional method group, intraoperative fluoroscopy was used to assist the screw placement. In the RPDT navigation group, specific RPDTs were constructed for each specimen and were used intraoperatively for screw placement navigation. The screw position, the operating time, and the fluoroscopy time for each screw placement were compared between the 2 groups. Results. Compared with the conventional method, the RPDT technique significantly increased the placement accuracy of the C2-PS (p < 0.05). In the axial plane, using RPDTs also significantly increased C1-LMS placement accuracy (p < 0.05). In the sagittal plane, although using RPDTs had a very high accuracy rate (100%) in C1-LMS placement, it was not statistically significant compared with the conventional method (p > 0.05). Moreover, the RPDT technique significantly decreased the operating and fluoroscopy times. Conclusion. Using RPDTs significantly increases the accuracy of C1-LMS and C2-PS placement while decreasing the screw placement time and the radiation exposure. Due to these advantages, this approach is worth promoting for use in the Harms technique. PMID:28004004

  15. Ball Screw Actuator Including a Compliant Ball Screw Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Hanlon, Casey (Inventor)

    2017-01-01

    An actuator includes a ball nut, a ball screw, and a ball screw stop. The ball nut is adapted to receive an input torque and in response rotates and supplies a drive force. The ball screw extends through the ball nut and has a first end and a second end. The ball screw receives the drive force from the ball nut and in response selectively translates between a retract position and a extend position. The ball screw stop is mounted on the ball screw proximate the first end to translate therewith. The ball screw stop engages the ball nut when the ball screw is in the extend position, translates, with compliance, a predetermined distance toward the first end upon engaging the ball nut, and prevents further rotation of the ball screw upon translating the predetermined distance.

  16. Ball Screw Actuator Including a Compliant Ball Screw Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Hanlon, Casey (Inventor)

    2015-01-01

    An actuator includes a ball nut, a ball screw, and a ball screw stop. The ball nut is adapted to receive an input torque and in response rotates and supplies a drive force. The ball screw extends through the ball nut and has a first end and a second end. The ball screw receives the drive force from the ball nut and in response selectively translates between a retract position and a extend position. The ball screw stop is mounted on the ball screw proximate the first end to translate therewith. The ball screw stop engages the ball nut when the ball screw is in the extend position, translates, with compliance, a predetermined distance toward the first end upon engaging the ball nut, and prevents further rotation of the ball screw upon translating the predetermined distance.

  17. The Effects of Spinopelvic Parameters and Paraspinal Muscle Degeneration on S1 Screw Loosening

    PubMed Central

    Kim, Jin-Bum; Lee, Young-Seok; Nam, Taek-Kyun; Park, Yong-Sook; Kim, Young-Baeg

    2015-01-01

    Objective To investigate risk factors for S1 screw loosening after lumbosacral fusion, including spinopelvic parameters and paraspinal muscles. Methods We studied with 156 patients with degenerative lumbar disease who underwent lumbosacral interbody fusion and pedicle screw fixation including the level of L5-S1 between 2005 and 2012. The patients were divided into loosening and non-loosening groups. Screw loosening was defined as a halo sign larger than 1 mm around a screw. We checked cross sectional area of paraspinal muscles, mean signal intensity of the muscles on T2 weight MRI as a degree of fatty degeneration, spinopelvic parameters, bone mineral density, number of fusion level, and the characteristic of S1 screw. Results Twenty seven patients showed S1 screw loosening, which is 24.4% of total. The mean duration for S1 screw loosening was 7.3±4.1 months after surgery. Statistically significant risk factors were increased age, poor BMD, 3 or more fusion levels (p<0.05). Among spinopelvic parameters, a high pelvic incidence (p<0.01), a greater difference between pelvic incidence and lumbar lordotic angle preoperatively (p<0.01) and postoperatively (p<0.05). Smaller cross-sectional area and high T2 signal intensity in both multifidus and erector spinae muscles were also significant muscular risk factors (p<0.05). Small converging angle (p<0.001) and short intraosseous length (p<0.05) of S1 screw were significant screw related risk factors (p<0.05). Conclusion In addition to well known risk factors, spinopelvic parameters and the degeneration of paraspinal muscles also showed significant effects on the S1 screw loosening. PMID:26587190

  18. Horizontal ridge expansion and implant placement using screws: a report of two cases

    PubMed Central

    Kim, Young-Kyun

    2014-01-01

    Implants are typically placed after performing ridge expansion by inserting screws of gradually increasing thickness and good clinical outcomes are often obtained. We placed 11 implants in 6 patients, and one implant failed during osseointegration but it was replaced immediately after removal and successful prosthetic treatments were completed. During these surgeries, buccal cortical plate complete fractures do not occur. Inserting screws for ridge expansion is a successful and predictable technique for implant placement in narrow alveolar bone. PMID:25368836

  19. Scaphoid Proximal Pole Fracture Following Headless Screw Fixation

    PubMed Central

    Rancy, Schneider K.; Zelken, Jonathan A.; Lipman, Joseph D.; Wolfe, Scott W.

    2015-01-01

    Background Headless screw fixation of scaphoid fractures and nonunions yields predictably excellent outcomes with a relatively low complication profile. However, intramedullary implants affect the load to failure and stress distribution within bone and may be implicated in subsequent fracture. Case Description We describe a posttraumatic fracture pattern of the scaphoid proximal pole originating at the previous headless screw insertion site in three young male patients with healed scaphoid nonunions. Each fracture was remarkably similar in shape and size, comprised the volar proximal pole, and was contiguous with the screw entry point. Treatment was challenging but successful in all cases. Literature Review Previous reports have posited that stress-raisers secondary to screw orientation may be implicated in subsequent peri-implant fracture of the femoral neck. Repeat scaphoid fracture after screw fixation has also been reported. However, the shape and locality of secondary fracture have not been described, nor has the potential role of screw fixation in the production of distinct fracture patterns. Clinical Relevance Hand surgeons must be aware of this difficult complication that may follow antegrade headless screw fixation of scaphoid fracture nonunion, and of available treatment strategies. PMID:26855840

  20. Use of the Composite Pedicled Pectoralis Minor Flap after Resection of Soft Tissue Sarcoma in Reconstruction of the Glenohumeral Joint

    PubMed Central

    van de Sande, Michiel A. J.; Cosker, Tom; McDonnell, Stephen M.; Gibbons, C. L. M. H.; Giele, Henk

    2014-01-01

    The surgical repair of an extensive anterior glenohumeral soft tissue defect is complicated by glenohumeral instability and subsequent significant functional deficit. This surgical note offers a relatively simple reconstruction of the anterior capsule and subscapularis muscle using a pectoralis minor pedicle flap. This reconstruction is supplemented with functional reconstruction of the anterior glenohumeral joint. A conventional deltopectoral approach is utilized and pectoralis minor is freed from its coracoid insertion, released, and mobilized without compromising the pedicle entering from the dorsum and inferior one-third of the muscle. The mobilized pectoralis minor vascular pedicle has sufficient length for the pectoralis minor to be transferred to provide coverage of the anterior shoulder joint even in full external rotation, providing anterior stability. To further improve glenohumeral stability and shoulder function, the pectoralis major muscle can be split with the clavicular part reinserted lateral to the bicipital groove onto the lesser tuberosity replacing subscapularis function while stabilising the glenohumeral joint. PMID:25610683

  1. Biomechanical analysis of stiffness and fracture displacement after using PMMA-augmented sacroiliac screw fixation for sacrum fractures.

    PubMed

    Höch, Andreas; Schimpf, Richard; Hammer, Niels; Schleifenbaum, Stefan; Werner, Michael; Josten, Christoph; Böhme, Jörg

    2017-03-15

    Cement augmentation of pedicle screws is the gold standard for the stabilization of osteoporotic fractures of the spine. In-screw cement augmentation, in which cement is injected through the cannula, is another option for fracture stabilization of fragility fractures of the sacrum. However, biomechanical superiority of this technique compared to conventional sacroiliac screw fixation has not been tested. The present study compares the stability of cement-augmented and non-cement-augmented sacroiliac screw fixation in osteoporotic sacrum fractures under cyclic loading. Eight human donor pelvises with intact ligaments and 5th lumbar vertebra were dissected. A vertical shear fracture was created as a combination of a sacrum fracture and cutting of the symphysis. Both sides were tested in a single-limb-stance setup with 10,000 loading cycles applied. Stiffness of the pelvis and displacement of the fracture were measured using a hydraulic testing machine and a 3D image correlation system. The augmented screw fixation failed in two of eight pelvises, and the non-augmented screws failed in three of eight pelvises. CT scans showed no leakage of cement. In-screw polymethylmethacrylate (PMMA) augmentation showed no advantage based on measured displacement of the sacrum fractures or stiffness for sacroiliac screw fixation of fragility fractures of the sacrum.

  2. Helical screw viscometer

    DOEpatents

    Aubert, J.H.; Chapman, R.N.; Kraynik, A.M.

    1983-06-30

    A helical screw viscometer for the measurement of the viscosity of Newtonian and non-Newtonian fluids comprising an elongated cylindrical container closed by end caps defining a circular cylindrical cavity within the container, a cylindrical rotor member having a helical screw or ribbon flight carried by the outer periphery thereof rotatably carried within the cavity whereby the fluid to be measured is confined in the cavity filling the space between the rotor and the container wall. The rotor member is supported by axle members journaled in the end caps, one axle extending through one end cap and connectable to a drive source. A pair of longitudinally spaced ports are provided through the wall of the container in communication with the cavity and a differential pressure meter is connected between the ports for measuring the pressure drop caused by the rotation of the helical screw rotor acting on the confined fluid for computing viscosity.

  3. Anatomic Study of Anterior Transdiscal Axial Screw Fixation for Subaxial Cervical Spine Injuries.

    PubMed

    Ji, Wei; Zheng, Minghui; Qu, Dongbin; Zou, Lin; Chen, Yongquan; Chen, Jianting; Zhu, Qingan

    2016-08-01

    Anterior transdiscal axial screw (ATAS) fixation is an alternative or supplement to the plate and screw constructs for the upper cervical spine injury. However, no existing literatures clarified the anatomic feasibility of this technique for subaxial cervical spine. Therefore, the objective of this study was to evaluate the anatomical feasibility and to establish guidelines for the use of the ATAS fixation for the subaxial cervical spine injury.Fifty normal cervical spines had radiographs to determine the proposed screw trajectory (the screw length and insertion angle) and the interbody graft-related parameters (the disc height and depth, and the distance between anterior vertebral margin and the screw) for all levels of the subaxial cervical spine. Following screw insertion in 8 preserved human cadaver specimens, surgical simulation and dissection verified the feasibility and safety of the ATAS fixation.Radiographic measurements showed the mean axial screw length and cephalic incline angle of all levels were 41.2 mm and 25.2°, respectively. The suitable depth of the interbody graft was >11.7 mm (the distance between anterior vertebral margin and the screw), but <17.1 mm (disc depth). Except the axial screw length, increase in all the measurements was seen with level up to C5-C6 segment. Simulated procedure in the preserved specimens demonstrated that ATAS fixation could be successfully performed at C2-C3, C3-C4, C4-C5, and C5-C6 levels, but impossible at C6-C7 due to the obstacle of the sternum. All screws were placed accurately. None of the screws penetrated into the spinal canal and caused fractures determined by dissecting the specimens.The anterior transdiscal axial screw fixation, as an alternative or supplementary instrumentation for subaxial cervical spine injuries, is feasible and safe with meticulous surgical planning.

  4. Cytotoxicity of a new antimicrobial coating for surgical screws: an in vivo study

    PubMed Central

    Güzel, Yunus; Elmadag, Mehmet; Uzer, Gokcer; Yıldız, Fatih; Bilsel, Kerem; Tuncay, İbrahim

    2017-01-01

    INTRODUCTION The risk of surgery-related infection is a persistent problem in orthopaedics and infections involving implants are particularly difficult to treat. This study explored the responses of bone and soft tissue to antimicrobial-coated screws. We investigated whether such screws, which have never been used to fix bony tissues, would result in a cytotoxic effect. We hypothesised that the coated screws would not be toxic to the bone and that the likelihood of infection would be reduced since bacteria are not able to grow on these screws. METHODS Titanium screws were inserted into the left supracondylar femoral regions of 16 rabbits. The screws were either uncoated (control group, n = 8) or coated with a polyvinylpyrrolidone-polyurethane interpolymer with tertiary amine functional groups (experimental group, n = 8). At Week 6, histological samples were obtained and examined. The presence of necrosis, fibrosis and inflammation in the bony tissue and the tissue surrounding the screws was recorded. RESULTS Live, cellular bone marrow was present in all the rabbits from the experimental group, but was replaced with connective tissue in four rabbits from the control group. Eight rabbits from the control group and two rabbits from the experimental group had necrosis in fatty bone marrow. Inflammation was observed in one rabbit from the experimental group and five rabbits from the control group. CONCLUSION Titanium surgical screws coated with polyvinylpyrrolidone-polyurethane interpolymer were associated with less necrosis than standard uncoated screws. The coated screws were also not associated with any cytotoxic side effect. PMID:26805670

  5. Feeding tube insertion - gastrostomy

    MedlinePlus

    ... tube insertion; G-tube insertion; PEG tube insertion; Stomach tube insertion; Percutaneous endoscopic gastrostomy tube insertion ... and down the esophagus, which leads to the stomach. After the endoscopy tube is inserted, the skin ...

  6. Evaluation of contributions of orthodontic mini-screw design factors based on FE analysis and the Taguchi method.

    PubMed

    Lin, Chun-Li; Yu, Jian-Hong; Liu, Heng-Liang; Lin, Chih-Hao; Lin, Yang-Sung

    2010-08-10

    This study determines the relative effects of changes in bone/mini-screw osseointegration and mini-screw design factors (length, diameter, thread shape, thread depth, material, head diameter and head exposure length) on the biomechanical response of a single mini-screw insertion. Eighteen CAD and finite element (FE) models corresponding to a Taguchi L(18) array were constructed to perform numerical simulations to simulate mechanical responses of a mini-screw placed in a cylindrical bone. The Taguchi method was employed to determine the significance of each design factor in controlling strain. Simulation results indicated that mini-screw material, screw exposure length and screw diameter were the major factors affecting bone strain, with percentage contributions of 63%, 24% and 7%, respectively. Bone strain decreased obviously when screw material had the high elastic modulus of stainless/titanium alloys, a small exposure length and a large diameter. Other factors had no significant on bone strain. The FE analysis combined with the Taguchi method efficiently identified the relative contributions of several mini-screw design factors, indicating that using a strong stainless/titanium alloys as screw material is advantageous, and increase in mechanical stability can be achieved by reducing the screw exposure length. Simulation results also revealed that mini-screw and bone surface contact can provide sufficient mechanical retention to perform immediately load in clinical treatment.

  7. Foreign body reaction after PLC reconstruction caused by a broken PLLA screw.

    PubMed

    Kim, Tae-Kwon; Jeong, Tae-Wan; Lee, Dae-Hee

    2014-12-01

    Foreign body reactions may occur in patients who receive bioabsorbable implants during orthopedic surgery for fractures and ligament repair. The authors describe a 34-year-old man who presented with a palpable tender mass on the lateral aspect of the left knee of 1 month's duration. He underwent posterior cruciate ligament and posterolateral corner reconstruction 3 years earlier. Physical examination showed a 1×1-cm soft, nontender mass without localized warmth on the lateral epicondyle of the distal femur. Magnetic resonance imaging showed a broken screw fragment surrounded by a cyst-like mass. Under general anesthesia, the surgeon excised the screw fragment and the fibrotic mass, enclosing it in the subcutaneous tissue at the lateral epicondyle, the site at which a poly-L-lactic acid bioabsorbable screw had been inserted to fix the graft for posterolateral corner reconstruction. Histologic evaluation showed a foreign body reaction to the degraded screw particles. To the authors' knowledge, this report is the first description of a patient presenting with a delayed foreign body reaction to a broken poly-L-lactic acid bioabsorbable screw at the lateral femoral epicondyle after posterolateral corner reconstruction. Because delayed foreign body reactions can occur at any site of poly-L-lactic acid bioabsorbable screw insertion, care should be taken to avoid screw protrusion during ligament reconstruction because it can lead to screw breakage and delayed foreign body reaction.

  8. C2 laminar screw and C1-2 transarticular screw combined with C1 laminar hooks for atlantoaxial instability with unilateral vertebral artery injury.

    PubMed

    Guo, Qunfeng; Liu, Jun; Ni, Bin; Lu, Xuhua; Zhou, Fengjin

    2011-09-01

    Transarticular screw fixation (TASF) is technically demanding, with high risk of vertebral artery (VA) injury. How to manage intraoperative VA injury and choose optimal alternative fixation becomes a concern of spinal surgeons. In this study, the management strategy for a patient with suspected intraoperative VA injury was analyzed. A 53-year-old woman developed type II odontoid fracture and brain stem injury due to a motor vehicle accident 3 months earlier. After conservative treatments, the brain stem injury improved, but with residual ocular motility defect in the right eye. The odontoid fracture did not achieve fusion with displacement and absorption of fracture fragments. After admission, atlantoaxial fixation using bilateral C1-2 transarticular screws (TASs) combined with C1 laminar hooks was planed. The first TAS was inserted successfully. Unfortunately, suspected VA injury developed during tapping the tract for the second TAS. Considering the previous brain stem injury and that directly inserting the screw to tamponade the hemorrhage might cause VA stenosis or occlusion, we blocked the screw trajectory with bone wax. C2 laminar screw was implanted instead of intended TAS on the injured side. The management strategy for suspected VA injury should depend on intraoperative circumstances and be tailored to patients. Blocking screw trajectory with bone wax is a useful method to stop bleeding. Atlantoaxial fixation using C2 laminar screw and C1-2 TAS combined with C1 laminar hooks is an ideal alternative procedure.

  9. NUT SCREW MECHANISMS

    DOEpatents

    Glass, J.A.F.

    1958-07-01

    A reactor control mechanism is described wherein the control is achieved by the partial or total withdrawal of the fissile material which is in the form of a fuel rod. The fuel rod is designed to be raised and lowered from the reactor core area by means of two concentric ball nut and screw assemblies that may telescope one within the other. These screw mechanisms are connected through a magnetic clutch to a speed reduction gear and an accurately controllable prime motive source. With the clutch energized, the fuel rod may be moved into the reactor core area, and fine adjustments may be made through the reduction gearing. However, in the event of a power failure or an emergency signal, the magnetic clutch will become deenergized, and the fuel rod will drop out of the core area by the force of gravity, thus shutting down the operation of the reactor.

  10. A capillary Archimedes' screw

    NASA Astrophysics Data System (ADS)

    Darbois Texier, Baptiste; Dorbolo, Stephane

    2014-11-01

    As used by Egyptians for irrigation and reported by Archimedes, a screw turning inside a hollow pipe can pull out a fluid againt gravity. At a centimetric scale, an analagous system can be found with a drop pending on a rotating spiral which is tilted toward the horizontal. The ascent of the drop to the top of the spiral is considered and a theoretical model based on geometrical considerations is proposed. The climb of the drop is limited by the fluid deposition on the screw at high capillary number and by a centrifugation phenomenon. We find out the range of fluid proprities and spiral characteristics for which an ascending motion of the drop is possible. Finally we discuss the efficiency of such system to extract a fluid from a bath at a centrimetric scale.

  11. Prevalence of High-Riding Vertebral Artery and Morphometry of C2 Pedicles Using a Novel Computed Tomography Reconstruction Technique

    PubMed Central

    Wajanavisit, Wiwat; Fuangfa, Praman; Chanplakorn, Pongsthorn; Kraiwattanapong, Chaiwat; Jaovisidha, Supaneewan

    2016-01-01

    Study Design Cross-sectional, matched-pair comparative study. Purpose To determine whether a thin-sliced pedicular-oriented computed tomography (TPCT) scan reconstructed from an existing conventional computed tomography (CCT) scan is more accurate for identifying vertebral artery groove (VAG) anomalies than CCT. Overview of Literature Posterior atlantoaxial transarticular screw fixation and C2 pedicle screws can cause vertebral artery (VA) injury. Two anatomic variations of VAG anomalies are associated with VA injury: a high-riding VA (HRVA) and a narrow pedicle of the C2 vertebra. CCT scan is a reliable method used to evaluate VAG anomalies; however, its accuracy level remains debatable. Literature comparing the prevalence of C2 VAG anomalies between CCT and TPCT is limited. Methods A total of 200 computed tomography scans of the upper cervical spine obtained between January 2008 and December 2011 were evaluated for C2 VAG anomalies (HRVA and narrow pedicular width) using CCT and TPCT. The prevalence of C2 VAG anomalies was compared using these two different measurement methods via a McNemar's test. Results Of the 200 patients studied, 23 HRVA (6.01%; 95% confidence interval [CI], 3.61%–8.39%) were detected with CCT, whereas 66 HRVA (16.54%; 95% CI, 12.85%–20.23%) were detected with TPCT (p<0.001). Sixty-two narrow pedicles (15.58%; 95% CI, 11.99%–19.15%) were detected with CCT, whereas 90 narrow pedicles (22.83%; 95% CI, 18.58%–26.87%) were detected with TPCT (p<0.001). Conclusions VAG anomalies are commonly observed. A preoperative evaluation using TPCT reconstructed from an existing CCT revealed a significantly higher prevalence of C2 VAG anomalies than did CCT and showed comparable prevalence to previously published studies using more sophisticated and higher risk techniques. Therefore, we propose TPCT as an alternative preoperative evaluation for C2 screw placement and trajectory planning. PMID:27994792

  12. Stainless steel screws coated with bisphosphonates gave stronger fixation and more surrounding bone. Histomorphometry in rats.

    PubMed

    Wermelin, K; Suska, F; Tengvall, P; Thomsen, P; Aspenberg, P

    2008-02-01

    Coating of stainless steel screws with bisphosphonate in a fibrinogen matrix leads to an enhancement of the pullout strength 2 weeks after insertion in rat tibiae. This effect then increases over time until at least 8 weeks. The pullout force reflects the mechanical properties of the bone within the threads, which acts as a screw nut. The aim of the present study was to find descriptive and morphometric histological correlates to the increased pullout strength. Because the bisphosphonates are applied via the implant surface, we also measured bone to implant contact and how far away from the surface any effects could be seen. Stainless steel screws underwent one of three treatments: uncoated control, controls coated with a layer of cross-linked fibrinogen, or screws further modified with bisphosphonates covalently linked and physically adsorbed to the fibrinogen layer. At 1 (n=33) and 8 (n=27) weeks, bone to implant contact and bone area density in the threads were measured, as well as bone area density at 250 and 500 microm from the outer edge of the threads. Additionally, removal torque for each screw treatment was measured at 2 weeks (n=28). At 8 weeks, the part of the bisphosphonate screw that was located in the marrow cavity had become surrounded with bone, whereas there was almost no bone surrounding the controls. The bone area density in the threads along the entire bisphosphonate screw was increased by 40% compared with uncoated controls, and at 250 microm distance it was more than doubled. At 1 week, coated screws had less implant-bone contact, but at 8 weeks there was no difference between uncoated and bisphosphonate-coated screws. The bisphosphonate screws had 50% increased removal torque at 2 weeks compared to uncoated screws. Howship's lacunae and osteoclasts were found near the screws with bisphosphonates at 8 weeks, suggesting that some bone remodeling took place near the implant, in spite of the presence of bisphosphonates.

  13. Low noise lead screw positioner

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1986-01-01

    A very precise and low noise lead screw positioner, for positioning a retroreflector in an interferometer is described. A gas source supplies inert pressurized gas, that flows through narrow holes into the clearance space between a nut and the lead screw. The pressurized gas keeps the nut out of contact with the screw. The gas flows axially along the clearance space, into the environment. The small amount of inert gas flowing into the environment minimizes pollution. By allowing such flow into the environment, no seals are required between the end of the nut and the screw.

  14. Comparison of Isocentric C-Arm 3-Dimensional Navigation and Conventional Fluoroscopy for Percutaneous Retrograde Screwing for Anterior Column Fracture of Acetabulum

    PubMed Central

    He, Jiliang; Tan, Guoqing; Zhou, Dongsheng; Sun, Liang; Li, Qinghu; Yang, Yongliang; Liu, Ping

    2016-01-01

    Abstract Percutaneous screw insertion for minimally displaced or reducible acetabular fracture using x-ray fluoroscopy and computer-assisted navigation system has been advocated by some authors. The purpose of this study was to compare intraoperative conditions and clinical results between isocentric C-arm 3-dimensional (Iso-C 3D) fluoroscopy and conventional fluoroscopy for percutaneous retrograde screwing of acetabular anterior column fracture. A prospective cohort study was conducted. A total of 22 patients were assigned to 2 different groups: 10 patients in the Iso-C 3D navigation group and 12 patients in the conventional group. The operative time, fluoroscopic time, time of screw insertion, blood loss, and accuracy were analyzed between the 2 groups. There were significant differences in operative time, screw insertion time, fluoroscopy time, and mean blood loss between the 2 groups. Totally 2 of 12 (16.7%) screws were misplaced in the conventional fluoroscopy group, and all 10 screws were in safe zones in the navigation group. Percutaneous screw fixation using the Iso-C 3D computer-assisted navigation system significantly reduced the intraoperative fluoroscopy time and blood loss in percutaneous screwing for acetabular anterior column fracture. The Iso-C 3D computer-assisted navigation system provided a reliable and effective method for percutaneous screw insertion in acetabular anterior column fractures compared to conventional fluoroscopy. PMID:26765448

  15. Insertion Sequences

    PubMed Central

    Mahillon, Jacques; Chandler, Michael

    1998-01-01

    Insertion sequences (ISs) constitute an important component of most bacterial genomes. Over 500 individual ISs have been described in the literature to date, and many more are being discovered in the ongoing prokaryotic and eukaryotic genome-sequencing projects. The last 10 years have also seen some striking advances in our understanding of the transposition process itself. Not least of these has been the development of various in vitro transposition systems for both prokaryotic and eukaryotic elements and, for several of these, a detailed understanding of the transposition process at the chemical level. This review presents a general overview of the organization and function of insertion sequences of eubacterial, archaebacterial, and eukaryotic origins with particular emphasis on bacterial elements and on different aspects of the transposition mechanism. It also attempts to provide a framework for classification of these elements by assigning them to various families or groups. A total of 443 members of the collection have been grouped in 17 families based on combinations of the following criteria: (i) similarities in genetic organization (arrangement of open reading frames); (ii) marked identities or similarities in the enzymes which mediate the transposition reactions, the recombinases/transposases (Tpases); (iii) similar features of their ends (terminal IRs); and (iv) fate of the nucleotide sequence of their target sites (generation of a direct target duplication of determined length). A brief description of the mechanism(s) involved in the mobility of individual ISs in each family and of the structure-function relationships of the individual Tpases is included where available. PMID:9729608

  16. Thoracic pedicle subtraction osteotomy in the treatment of severe pediatric deformities.

    PubMed

    Bakaloudis, Georgios; Lolli, Francesco; Di Silvestre, Mario; Greggi, Tiziana; Astolfi, Stefano; Martikos, Konstantinos; Vommaro, Francesco; Barbanti-Brodano, Giovanni; Cioni, Alfredo; Giacomini, Stefano

    2011-05-01

    The traditional surgical treatment of severe spinal deformities, both in adult and pediatric patients, consisted of a 360° approach. Posterior-based spinal osteotomy has recently been reported as a useful and safe technique in maximizing kyphosis and/or kyphoscoliosis correction. It obviates the deleterious effects of an anterior approach and can increase the magnitude of correction both in the coronal and sagittal plane. There are few reports in the literature focusing on the surgical treatment of severe spinal deformities in large pediatric-only series (age <16 years old) by means of a posterior-based spinal osteotomy, with no consistent results on the use of a single posterior-based thoracic pedicle subtraction osteotomy in the treatment of such challenging group of patients. The purpose of the present study was to review our operative experience with pediatric patients undergoing a single level PSO for the correction of thoracic kyphosis/kyphoscoliosis in the region of the spinal cord (T12 and cephalad), and determine the safety and efficacy of posterior thoracic pedicle subtraction osteotomy (PSO) in the treatment of severe pediatric deformities. A retrospective review was performed on 12 consecutive pediatric patients (6 F, 6 M) treated by means of a posterior thoracic PSO between 2002 and 2006 in a single Institution. Average age at surgery was 12.6 years (range, 9-16), whereas the deformity was due to a severe juvenile idiopathic scoliosis in seven cases (average preoperative main thoracic 113°; 90-135); an infantile idiopathic scoliosis in two cases (preoperative main thoracic of 95° and 105°, respectively); a post-laminectomy kypho-scoliosis of 95° (for a intra-medullar ependimoma); an angular kypho-scoliosis due to a spondylo-epiphisary dysplasia (already operated on four times); and a sharp congenital kypho-scoliosis (already operated on by means of a anterior-posterior in situ fusion). In all patients a pedicle screws instrumentation was used

  17. Effects of screw eccentricity on the initial stability of the acetabular cup in artificial foam bone of different qualities.

    PubMed

    Hsu, Jui-Ting; Lin, Dan-Jae

    2010-01-01

    Acetabular cup loosening is one of the major failure models of total hip replacement (THR), which is mostly due to insufficient initial stability of the cup. Previous studies have demonstrated that cup stability is affected by the quality of the host bone and the surgical skill when inserting screws. The purpose of this study was to determine the effects on the initial stability of the acetabular cup of eccentric screws in bone of different qualities. In this study, hemispherical cups were fixed into bone specimens constructed from artificial foam with three elastic moduli using one to three screws. The effects of two types of screw eccentricity (offset and angular) on the stability of the acetabular cup were also evaluated. The experimental results indicate that in the presence of ideal screwing, the cup was stable in bone specimens constructed from foam with the highest elastic modulus. In addition, increasing the number of ideal screws enhanced the cup stability, especially in bone specimens constructed from soft foam. Moreover, the cup stability was most affected by offset eccentric screw(s) in the hard-foam bone specimens and by angular eccentric screw(s) in the soft-foam bone specimens. The reported results indicate that the presence of screw eccentricity affects the initial stability of the acetabular cup. Surgeons should keep this in mind when performing screw insertions in THR. However, care is necessary when translating these results to the intraoperative situation due to the experiments being conducted under laboratory conditions, and hence, future studies should attempt to replicate the results reported here in vivo.

  18. An intermaxillary fixation screw traction wire: an aid for facial bone fracture repair.

    PubMed

    Kim, Myung-Good; Yoo, Roh-Eul; Chang, Hak; Kwon, Sung-Tack; Baek, Rong-Min; Minn, Kyung-Won

    2009-07-01

    We have devised a new technique to improve stabilization of fractured facial bone fractures (frontal sinus fractures, zygomatic fractures, mandibular condyle fractures) by intermaxillary fixation screw traction wires (stainless steel wires through intermaxillary fixation screws). A retrospective study evaluating intermaxillary fixation screw traction wires was performed. We have used this technique for 3 cases of frontal sinus fractures, 9 cases of zygomatic fractures, and 7 cases of mandibular condyle fractures. After dissection of a fractured site, a hole is drilled on the fractured bone where it does not interfere with positioning the plate across the fracture line. After an intermaxillary fixation screw is inserted, a stainless steel wire is tied through a hole in the screw head. By the aid of wire for traction, the displaced fractured bone is easily aligned to the proper position. Plates and screws are applied readily on the predetermined area. A retrospective study on 19 patients using intermaxillary fixation screw traction wires was performed. The diagnoses and associated complications of the cases were recorded. No associated complication as a result of using this technique was identified. The use of intermaxillary fixation screw traction wire enhances stabilization and visualization without possible risk for surrounding soft tissue injury using, a sharp traction device like a bone hook. An intermaxillary fixation screw traction wire is an useful aid for visualization and stabilization during facial bone fracture reduction, particularly where exposure is difficult such as in the condylar region of the mandible. And unlike a classic traction wire, the intermaxillary fixation screw traction wire has almost no risk of having it loosened from the screw.

  19. [Management of Odontoid Fractures with Compression Screw and Anterior Transarticular Screw Fixation in Elderly Patients].

    PubMed

    Kočiš, J; Kelbl, M; Veselý, R; Kočiš, T

    2017-01-01

    PURPOSE OF THE STUDY In the management of dens axis fractures in patients older than 65 years of age the posterior approach is preferred due to osteoporosis and the risk of a failure of anterior osteosynthesis. The posterior approach, however, is associated with a higher incidence of complications. A combination of anterior transarticular fixation of C1/2 (ATS) with compression osteosynthesis of dens axis significantly increases the stability of osteosynthesis. MATERIAL AND METHODS In the period from 2009 to 2015 our hospital admitted 13 patients older than 65 years of age with a diagnosed type III dens axis fracture based on AO classification. 8 patients sustained a dens axis fracture combined with a stable atlas fracture. The cohort consisted of 13 women aged 67 to 90 years, with the mean age of 82.3 years. None of the female patients were affected neurologically. The dens axis fracture was treated by anterior approach. Once the screw was inserted in the dens axis, two more screws were added, the entrance points of those screws were medial and lateral to the odontoid screw and direction was divergently via C1/2 joints in order to reinforce stability. The patients were monitored at 6-week, 3-, 6- and 12-month follow-ups. Bone healing was confirmed by CT scan. RESULTS No complications were recorded during the surgery in any of the 13 patients. In one female patient the stabilization failed in the early postoperative period. A reoperation from anterior approach with the use of the same method was necessary. In eleven patients bone healing occurred after 6 to 12 months. In two patients pseudoarthrosis was formed with no clinical symptoms. No neurological deterioration or a patient s death was reported in the monitored period within 12 months after the treatment. DISCUSSION Where dens axis fractures in elderly patients are managed operatively, the posterior approach and transarticular fixation of C1/2 with sublaminar loop are preferred. This procedure is considered

  20. Factors influencing the length of stay in patients with lumbar pedicle screw fixation

    PubMed Central

    El-Kadi, Matt; Ibinson, James; Donovan, Erin; Sullivan, Dan; Kadi, Rayyan

    2016-01-01

    Background: Current health care practices aim for cost reduction to achieve maximal benefit. Because of the increasing number of spinal fusions, this area has become a target for both hospitals and payment organizations. Length of stay (LOS) is one potentially modifiable variable to help reduce overall cost. Attempting to predict the LOS in spinal surgery based on patient factors has not revealed a set of variables that are consistently associated with increased stay. Methods: Medical records from all patients who underwent posterior lumbar spinal fusion by a single neurosurgeon at a single facility were retrospectively examined in a blind fashion. Data were obtained including age, gender, body mass index (BMI), American society of Anesthesiologists (ASA) and analyzed to determine a potential relationship with LOS. Results: A total of 1360 patients were identified for analysis. There were significant but small correlations between age, ASA, BMI, and LOS. Conclusions: There is an effect of age, ASA, and BMI on LOS. However, the significance of this effect is small. Future studies aiming to identify additional factors, which could potentially be modifiable, in order to work on decreasing LOS in lumbar spinal fusion patients. PMID:27843684

  1. Miniarthrotomy assisted percutaneous screw fixation for displaced medial malleolus fractures – A novel technique

    PubMed Central

    Saini, Pramod; Aggrawal, Abhinav; Meena, Sanjay; Trikha, Vivek; Mittal, Samarth

    2014-01-01

    Aim To describe here a technique of miniarthrotomy assisted percutaneous screw insertion for displaced Herscovici type B and C medial malleolar fractures. Method Incision was made centred over the superomedial angle of the ankle mortise, about half a cm medial to tibialis anterior. Arthrotomy was done and reduction obtained. Percuntaneously, two 4 mm cancellous cannulated screws were inserted through medial malleolus. Results and conclusion This approach allows direct visualization of reduction, removal of entrapped soft tissue and preservation of saphenous vein and nerve. PMID:25983507

  2. Z-2 Threaded Insert Design and Testing Abstract

    NASA Technical Reports Server (NTRS)

    Rhodes, RIchard; Graziosi, Dave; Jones, Bobby; Ferl, Jinny; Scarborough, Steve; Sweeney, Mitch

    2016-01-01

    The Z-2 Prototype Planetary Extravehicular Space Suit Assembly is a continuation of NASA's Z series of spacesuits. The Z-2 is another step in the NASA's technology development roadmap leading to human exploration of the Martian surface. To meet a more challenging set of requirements than previous suit systems standard design features, such as threaded inserts, have been re-analyzed and improved. NASA's Z-2 prototype space suit contains several components fabricated from an advanced hybrid composite laminate consisting of IM10 carbon fiber and fiber glass. One requirement NASA levied on the suit composites was the ability to have removable, replaceable helicoil inserts to which other suit components would be fastened. An approach utilizing bonded in inserts with helicoils inside of them was implemented. The design of the interface flanges of the composites allowed some of the inserts to be a "T" style insert that was installed through the entire thickness of the laminate. The flange portion of the insert provides a mechanical lock as a redundancy to the adhesive aiding in the pullout load that the insert can withstand. In some locations it was not possible to utilize at "T" style insert and a blind insert was used instead. These inserts rely completely on the bond strength of the adhesive to resist pullout. It was determined during the design of the suit that the inserts did not need to withstand loads induced from pressure cycling but instead tension induced from torqueing the screws to bolt on hardware which creates a much higher stress on them. Bolt tension is determined by dividing the torque on the screw by a k value multiplied by the thread diameter of the bolt. The k value is a factor that accounts for friction in the system. A common value used for k for a non-lubricated screw is 0.2. The k value can go down by as much as 0.1 if the screw is lubricated which means for the same torque, a much larger tension could be placed on the bolt and insert. This paper

  3. Carbon nanotube Archimedes screws.

    PubMed

    Oroszlány, László; Zólyomi, Viktor; Lambert, Colin J

    2010-12-28

    Recently, nanomechanical devices composed of a long stationary inner carbon nanotube and a shorter, slowly rotating outer tube have been fabricated. In this paper, we study the possibility of using such devices as nanoscale transducers of motion into electricity. When the outer tube is chiral, we show that such devices act like quantum Archimedes screws, which utilize mechanical energy to pump electrons between reservoirs. We calculate the pumped charge from one end of the inner tube to the other, driven by the rotation of a chiral outer nanotube. We show that the pumped charge can be greater than one electron per 360° rotation, and consequently, such a device operating with a rotational frequency of 10 MHz, for example, would deliver a current of ≈1 pAmp.

  4. Split spline screw

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1993-01-01

    A split spline screw type payload fastener assembly, including three identical male and female type split spline sections, is discussed. The male spline sections are formed on the head of a male type spline driver. Each of the split male type spline sections has an outwardly projecting load baring segment including a convex upper surface which is adapted to engage a complementary concave surface of a female spline receptor in the form of a hollow bolt head. Additionally, the male spline section also includes a horizontal spline releasing segment and a spline tightening segment below each load bearing segment. The spline tightening segment consists of a vertical web of constant thickness. The web has at least one flat vertical wall surface which is designed to contact a generally flat vertically extending wall surface tab of the bolt head. Mutual interlocking and unlocking of the male and female splines results upon clockwise and counter clockwise turning of the driver element.

  5. Evaluation of anatomic landmarks and safe zones for screw placement in the atlas via the posterior arch.

    PubMed

    Gebauer, Matthias; Barvencik, Florian; Briem, Daniel; Kolb, Jan P; Seitz, Sebastian; Rueger, Johannes M; Püschel, Klaus; Amling, Michael

    2010-01-01

    Several studies have evaluated quantitative anatomic data for direct lateral mass screw fixation. To analyze anatomic landmarks and safe zones for optimal screw placement through the posterior arc of the human atlas, morphometric parameters of 41 adult native human atlas specimens were quantitatively measured. Internal dimensions of the atlas (lateral mass, maximum and minimum intraosseous screw length), minimum height and width of the posterior arc and optimal screw insertion angles were defined on pQCT scans. By this, an optimal posterior screw insertion point (OIP) and a preferable screw direction (PSD) through the posterior arch into the lateral mass of C1 were defined. External dimensions (transverse and sagittal diameter) as well as the width of the mid-portion of C1 lateral mass were significantly higher in male specimens. The mean height of the posterior arch at the vertebral artery groove was 4.1 +/- 0.8 mm in female and 4.6 +/- 0.9 mm in male specimens. The optimal screw insertion point was located 21.6 +/- 1.7 mm in female and 23.6 +/- 2.3 mm in male lateral from the posterior tubercle of C1 (P < 0.01). The preferable screw direction was a mean medial inclination of 7.9 +/- 1.9 degrees in female and 7.3 +/- 2.7 degrees in male specimens and a mean rostral direction of 2.4 +/- 1.8 degrees in female and 3.1 +/- 1.7 degrees in male specimens. In conclusion, the presented study provides information for the use and design of upper cervical spine instrumentation techniques, such as screw placement to C1 via the posterior arch. The characterization of working areas and safe zones (OIP, PSD) might contribute to a minimization of screw malposition in this highly demanding instrumentation technique.

  6. Predictive value of pedicle involvement with MRI in spine metastases

    PubMed Central

    Bian, Chong; Liang, Yun; Jiang, Libo; Qian, Chen; Dong, Jian

    2016-01-01

    Objectives The study aimed to retrospectively evaluate the accuracy and value of magnetic resonance imaging (MRI) in predicting pedicle involvement for patients with spine metastases. Methods Forty-five patients with a vertebral metastasis encroaching at least one pedicle were studied using MRI before surgery and regularly after surgery. Patients were categorized on the basis of their numbers of pedicle involvement (Group 1: one pedicle was involved, n = 23; Group 2: two pedicles were involved, n = 22). The diagnostic accuracy was calculated, and comparisons of intraoperative blood loss and recurrence rate between the two groups were performed. Results The overall performance of MRI in predicting the pedicle involvement was as follows: accuracy, 94.4%; sensitivity, 95.5%; and specificity, 91.3%. Less intraoperative blood loss was observed for Group 1 compared with Group 2 (1,661 ± 672 ml and 2,173 ± 790 ml, respectively, P = 0.024). Tumor relapse occurred in 8.7% (2/23) of Group 1 and in 22.7% (5/22) of Group 2 with median recurrence free survival time 14 and 9 months, respectively. Conclusions MRI is a reliable approach to assess pedicle involvement. It has potential for use in the evaluation of the clinical characteristics of patients with spine metastases. PMID:27486876

  7. Transalveolar screw: a new concept for orthodontic anchorage.

    PubMed

    Hernández-Alfaro, Federico; Egio, Elisabeth; Ruiz, Vanessa

    2009-04-01

    The purpose of this article is to describe the use of a new trans-alveolar screw (TAS) as a temporary orthodontic anchorage device for the posterior maxilla, to intrude overerupted maxillary molars. To date, five consecutive patients have been treated with these newly designed screws. Intrusions achieved ranged from 2.1 and 6mm (mean 4.7 mm). The TAS is cheap, easy to place and remove by the orthodontist, has bicortical anchorage, and is loaded on both sides. The main advantage of TAS is that when placed in the maxilla to intrude upper molars, it allows application of intrusive force from both buccal and palatal aspects simultaneously, so that the line of force in relation to the center of resistance of the posterior segment, permits an in-mass intrusion, avoiding buccal tipping or rotations. Moreover the surgical procedure for inserting and removing the bicortical screw is simple and does not require any surgical flap, so complications are minimal and screws can be loaded immediately, without requiring any waiting healing period of time.

  8. Effect of cortical thickness and cancellous bone density on the holding strength of internal fixator screws.

    PubMed

    Seebeck, J; Goldhahn, J; Städele, H; Messmer, P; Morlock, M M; Schneider, E

    2004-11-01

    Internal fixators are a new class of implants designed to preserve the periosteal blood supply of the bone. In contrast to conventional plate fixation in which the screws have spherical heads and are loaded mainly by axial pullout forces, screws in internal fixators are "locked" within the plate and therefore subjected to axial as well as bending loads. In this study the ultimate loads of screws of a commercially available internal fixator system were tested in a pullout (n = 72) and cantilever bending mode (n = 72) in metaphyseal and diaphyseal regions of four pairs of human tibiae with different bone qualities. Cortical thickness and cancellous bone density were determined at the screw insertion sites. Stepwise multiple linear regression revealed that cortical thickness and cancellous density can explain 93% and 98% of the variance of the ultimate load of the screws in an axial pullout and cantilever bending mode. Screws in internal fixators are better suited to transmit shear forces and thereby make better use of the strength potential of bone than screws used in conventional plate fixation: this is especially advantageous when bone strength is reduced, e.g. due to osteoporosis.

  9. Does screw-bone interface modelling matter in finite element analyses?

    PubMed

    MacLeod, Alisdair R; Pankaj, Pankaj; Simpson, A Hamish R W

    2012-06-01

    The effect of screw-bone interface modelling strategies was evaluated in the setting of a tibial mid-shaft fracture stabilised using locking plates. Three interface models were examined: fully bonded interface; screw with sliding contact with bone; and screw with sliding contact with bone in an undersized pilot hole. For the simulation of the last interface condition we used a novel thermal expansion approach to generate the pre-stress that the bone would be exposed to during screw insertion. The study finds that the global load-deformation response is not influenced by the interface modelling approach employed; the deformation varied by less than 1% between different interaction models. However, interface modelling is found to have a considerable impact on the local stress-strain environment within the bone in the vicinity of the screws. Frictional and tied representations did not have significantly different peak strain values (<5% difference); the frictional interface had higher peak compressive strains while the tied interface had higher tensile strains. The undersized pilot hole simulation produced the largest strains. The peak minimum principal strains for the frictional interface were 26% of those for the undersized pilot hole simulation at a load of 770 N. It is concluded that the commonly used tie constraint can be used effectively when the only interest is the global load-deformation behaviour. Different contact interface models, however, alter the mechanical response around screw holes leading to different predictions for screw loosening, bone damage and stress shielding.

  10. Evaluation of different screw fixation techniques and screw diameters in sagittal split ramus osteotomy: finite element analysis method.

    PubMed

    Sindel, A; Demiralp, S; Colok, G

    2014-09-01

    Sagittal split ramus osteotomy (SSRO) is used for correction of numerous congenital or acquired deformities in facial region. Several techniques have been developed and used to maintain fixation and stabilisation following SSRO application. In this study, the effects of the insertion formations of the bicortical different sized screws to the stresses generated by forces were studied. Three-dimensional finite elements analysis (FEA) and static linear analysis methods were used to investigate difference which would occur in terms of forces effecting onto the screws and transmitted to bone between different application areas. No significant difference was found between 1·5- and 2-mm screws used in SSRO fixation. Besides, it was found that 'inverted L' application was more successful compared to the others and that was followed by 'L' and 'linear' formations which showed close rates to each other. Few studies have investigated the effect of thickness and application areas of bicortical screws. This study was performed on both advanced and regressed jaws positions.

  11. A novel in silico method to quantify primary stability of screws in trabecular bone.

    PubMed

    Steiner, Juri A; Christen, Patrik; Affentranger, Remo; Ferguson, Stephen J; van Lenthe, Gerrit Harry

    2017-02-27

    Insufficient primary stability of screws in bone leads to screw loosening and failure. Unlike conventional continuum finite-element models, micro-CT based finite-element analysis (micro-FE) is capable of capturing the patient-specific bone micro-architecture, providing accurate estimates of bone stiffness. However, such in silico models for screws in bone highly overestimate the apparent stiffness. We hypothesized that a more accurate prediction of primary implant stability of screws in bone is possible by considering insertion-related bone damage. We assessed two different screw types and loading scenarios in 20 trabecular bone specimens extracted from 12 cadaveric human femoral heads (N = 5 for each case). In the micro-FE model, we predicted specimen-specific Young's moduli of the peri-implant bone damage region based on morphometric parameters such that the apparent stiffness of each in silico model matched the experimentally measured stiffness of the corresponding in vitro specimen as closely as possible. The standard micro-FE models assuming perfectly intact peri-implant bone overestimated the stiffness by over 330%. The consideration of insertion related damaged peri-implant bone corrected the mean absolute percentage error down to 11.4% for both loading scenarios and screw types. Cross-validation revealed a mean absolute percentage error of 14.2%. We present the validation of a novel micro-FE modeling technique to quantify the apparent stiffness of screws in trabecular bone. While the standard micro-FE model overestimated the bone-implant stiffness, the consideration of insertion-related bone damage was crucial for an accurate stiffness prediction. This approach provides an important step toward more accurate specimen-specific micro-FE models. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

  12. Dihalocarbene Insertion Experiment

    ERIC Educational Resources Information Center

    Goh, S. H.

    1975-01-01

    Describes the insertion reaction using the insertion of carbenes into carbon-hydrogen bonds as an example. Outlines an experiment that will illustrate dihalocarbene insertions into diisopropyl ether. (GS)

  13. Chest tube insertion

    MedlinePlus

    Chest drainage tube insertion; Insertion of tube into chest; Tube thoracostomy; Pericardial drain ... When your chest tube is inserted, you will lie on your side or sit partly upright, with one arm over your head. Sometimes, ...

  14. Titanium integration with bone, welding, and screw head destruction complicating hardware removal of the distal radius: report of 2 cases.

    PubMed

    Van Nortwick, Sara S; Yao, Jeffrey; Ladd, Amy L

    2012-07-01

    Increasingly, surgeons treat distal radius fractures with locking plate systems. Recent case reports have focused on technical insertion errors resulting in removal difficulties: poor drilling orientation or cross-threading, destruction of the screw head, and filling of the screw recess with tissue. We report 2 complications of titanium locked plate removal secondary to in vivo reactions including titanium integration with bone and mechanical binding between the titanium screw and plate. We clarify and discuss terminology relevant to implant removal, including cold-welding, galling, fretting, and anodization. Even with optimal technique, in situ reactions can complicate titanium implant removal.

  15. Effect of surface coating on the screw loosening of dental abutment screws

    NASA Astrophysics Data System (ADS)

    Park, Chan-Ik; Choe, Han-Cheol; Chung, Chae-Heon

    2004-12-01

    Regardless of the type of performed restoration, in most cases, a screw connection is employed between the abutment and implant. For this reason, implant screw loosening has remained a problem in restorative practices. The purpose of this study was to compare the surface of coated/plated screws with titanium and gold alloy screws and to evaluate the physical properties of coated/plated material after scratch tests via FE-SEM (field emission scanning electron microscopy) investigation. GoldTite, titanium screws provided by 3i (Implant Innovation, USA) and TorqTite, titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, Korea) were selected for this study. The surface, crest, and root of the abutment screws were observed by FE-SEM. A micro-diamond needle was also prepared for the scratch test. Each abutment screw was fixed, and a scratch on the surface of the head region was made at constant load and thereafter the fine trace was observed with FE-SEM. The surface of GoldTite was smoother than that of other screws and it also had abundant ductility and malleability compared with titanium and gold screws. The scratch tests also revealed that teflon particles were exfoliated easily in the screw coated with teflon. The titanium screw had rough surface and low ductility. The clinical use of gold-plated screws is recommended as a means of preventing screw loosening.

  16. Metallurgical examination of gun barrel screws

    SciTech Connect

    Bird, E.L.; Clift, T.L.

    1996-06-01

    The examination was conducted to determine the extent of degradation that had occurred after a series of firings; these screws prevent live rounds of ammunition from being loaded into the firing chamber. One concern is that if the screw tip fails and a live round is accidentally loaded into the chamber, a live round could be fired. Another concern is that if the blunt end of the screw begins to degrade by cracking, pieces could become small projectiles during firing. All screws used in firing 100 rounds or more exhibited some degree degradation, which progressively worsened as the number of rounds fired increased. (SEM, metallography, x-ray analysis, and microhardness were used.) Presence of cracks in these screws after 100 fired rounds is a serious concern that warrants the discontinued use of these screws. The screw could be improved by selecting an alloy more resistant to thermal and chemical degradation.

  17. Minimally Invasive Spinal Arthrodesis in Osteoporotic Population Using a Cannulated and Fenestrated Augmented Screw: Technical Description and Clinical Experience

    PubMed Central

    Lubansu, Alphonse; Rynkowski, Michal; Abeloos, Laurence; Appelboom, Geoffrey; Dewitte, Olivier

    2012-01-01

    We describe a percutaneous or minimally invasive approach to apply an augmentation of pedicle fenestrated screws by injection of the PMMA bone cement through the implant and determine the safety and efficiency of this technique in a clinical series of 15 elderly osteoporotic patients. Clinical outcome and the function were assessed using respectively the Visual Analogue Scale (VAS) score and the Oswestry Disability Index (ODI). Peri- and post-operative complications were monitored during a minimum of 2 years of follow-up. Radiographic follow-up was based on plain fluoroscopic control at 3, 6 and 12 months and every year. In this approach, four steps were considered with care: optimal positioning of the screws, correct alignment of the screw heads, waiting time before the injection of cement, fluoroscopic control of the cement injection. Using these precautions, only 2 minor complications occurred. VAS scores and ODI questionnaires showed a statistically significant improvement up to 13.3 months postoperatively. No radiological complications were observed. Based on this experience, PMMA augmentation technique through the novel fenestrated screws provided an effective and long lasting fixation in osteoporotic patients. Applying this procedure through percutaneous or minimally invasive approach under fluoroscopic control seems to be safe. PMID:22970360

  18. Stability of the prosthetic screws of three types of craniofacial prostheses retention systems

    PubMed Central

    2016-01-01

    Objectives This study aimed to evaluate the stability of prosthetic screws from three types of craniofacial prostheses retention systems (bar-clip, ball/O-ring, and magnet) when submitted to mechanical cycling. Materials and Methods Twelve models of acrylic resin were used with implants placed 20 mm from each other and separated into three groups: (1) bar-clip (Sistema INP, São Paulo, Brazil), (2) ball/O-ring (Sistema INP), and (3) magnet (Metalmag, São Paulo, Brazil), with four samples in each group. Each sample underwent a mechanical cycling removal and insertion test (f=0.5 Hz) to determine the torque and the detorque values of the retention screws. A servo-hydraulic MTS machine (810-Flextest 40; MTS Systems, Eden Prairie, MN, USA) was used to perform the cycling with 2.5 mm and a displacement of 10 mm/s. The screws of the retention systems received an initial torque of 30 Ncm and the torque values required for loosening the screw values were obtained in three cycles (1,080, 2,160, and 3,240). The screws were retorqued to 30 Ncm before each new cycle. Results The sample was composed of 24 screws grouped as follows: bar-clip (n=8), ball/O-ring (n=8), and magnet (n=8). There were significant differences between the groups, with greater detorque values observed in the ball/O-ring group when compared to the bar-clip and magnet groups for the first cycle. However, the detorque value was greater in the bar-clip group for the second cycle. Conclusion The results of this study indicate that all prosthetic screws will loosen slightly after an initial tightening torque, also the bar-clip retention system demonstrated greater loosening of the screws when compared with ball/O-ring and magnet retention systems. PMID:28053905

  19. Trans-sacral screw fixation in the treatment of high dyplastic developmental spondylolisthesis

    PubMed Central

    Landi, Alessandro; Marotta, Nicola; Mancarella, Cristina; Tarantino, Roberto; Delfini, Roberto

    2013-01-01

    We describe the case of a 67-year-old woman with L5-S1 ontogenetic spondylolisthesis treated with pedicle fixation associated with interbody arthrodesis performed with S1-L5 trans-sacral screwing according to the technique of Bartolozzi. The procedure was followed by a wide decompressive laminectomy. The patient had a progressive improvement of the symptoms which gradually disappeared in 12 mo. The radiograph at 6 and 12 mo showed complete fusion system. The choice of treatment in L5-S1 ontogenetic spondylolithesis is related to a correct clinical and diagnostic planning (X-ray, computer tomography magnetic resonance imaging, Measurement). In particular, the severity index and the square of unstable zone, and the standard measurements already described in the literature, are important to understand and to plane the correct surgical strategy, that require, in most of the times, fusion and interbody artrodesis. PMID:24303480

  20. Screw-fed pump system

    SciTech Connect

    Sprouse, Kenneth M

    2014-11-25

    A pump system includes a pump that includes a first belt and a second belt that are spaced apart from each other to provide generally straight sides of a passage there between. There is an inlet at one end of the passage and an outlet at an opposite end of the passage, with a passage length that extends between the inlet and the outlet. The passage defines a gap distance in a width direction between the straight sides at the passage inlet. A hopper includes an interior space that terminates at a mouth at the passage inlet. At least one screw is located within the interior space of the hopper and includes a screw diameter in the width direction that is less than or equal to the gap distance.

  1. Helical screw expander evaluation project

    NASA Astrophysics Data System (ADS)

    McKay, R.

    1982-03-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  2. Helical screw expander evaluation project

    NASA Technical Reports Server (NTRS)

    Mckay, R.

    1982-01-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  3. The Use of MMF Screws: Surgical Technique, Indications, Contraindications, and Common Problems in Review of the Literature

    PubMed Central

    Cornelius, Carl-Peter; Ehrenfeld, Michael

    2010-01-01

    Mandibulo-maxillary fixation (MMF) screws are inserted into the bony base of both jaws in the process of fracture realignment and immobilisation. The screw heads act as anchor points to fasten wire loops or rubber bands connecting the mandible to the maxilla. Traditional interdental chain-linked wiring or arch bar techniques provide the anchorage by attached cleats, hooks, or eyelets. In comparison to these tooth-borne appliances MMF screws facilitate and shorten the way to achieve intermaxillary fixation considerably. In addition, MMF screws help to reduce the hazards of glove perforation and wire stick injuries. On the downside, MMF screws are attributed with the risk of tooth root damage and a lack of versatility beyond the pure maintenance of occlusion such as stabilizing loose teeth or splinting fragments of the alveolar process. The surgical technique of MMF screws as well as the pros and cons of the clinical application are reviewed. The adequate screw placement to prevent serious tooth root injuries is still an issue to rethink and modify conceptual guidelines. PMID:22110819

  4. The Use of MMF Screws: Surgical Technique, Indications, Contraindications, and Common Problems in Review of the Literature.

    PubMed

    Cornelius, Carl-Peter; Ehrenfeld, Michael

    2010-06-01

    Mandibulo-maxillary fixation (MMF) screws are inserted into the bony base of both jaws in the process of fracture realignment and immobilisation. The screw heads act as anchor points to fasten wire loops or rubber bands connecting the mandible to the maxilla. Traditional interdental chain-linked wiring or arch bar techniques provide the anchorage by attached cleats, hooks, or eyelets. In comparison to these tooth-borne appliances MMF screws facilitate and shorten the way to achieve intermaxillary fixation considerably. In addition, MMF screws help to reduce the hazards of glove perforation and wire stick injuries. On the downside, MMF screws are attributed with the risk of tooth root damage and a lack of versatility beyond the pure maintenance of occlusion such as stabilizing loose teeth or splinting fragments of the alveolar process. The surgical technique of MMF screws as well as the pros and cons of the clinical application are reviewed. The adequate screw placement to prevent serious tooth root injuries is still an issue to rethink and modify conceptual guidelines.

  5. Are allogenic or xenogenic screws and plates a reasonable alternative to alloplastic material for osteosynthesis--a histomorphological analysis in a dynamic system.

    PubMed

    Jacobsen, C; Obwegeser, J A

    2010-12-01

    Despite invention of titanium and resorbable screws and plates, still, one of the main challenges in bone fixation is the search for an ideal osteosynthetic material. Biomechanical properties, biocompatibility, and also cost effectiveness and clinical practicability are factors for the selection of a particular material. A promising alternative seems to be screws and plates made of bone. Recently, xenogenic bone pins and screws have been invented for use in joint surgery. In this study, screws made of allogenic sheep and xenogenic human bone were analyzed in a vital and dynamic sheep-model and compared to conventional titanium screws over a standard period of bone healing of 56 days with a constant applied extrusion force. Biomechanical analysis and histomorphological evaluation were performed. After 56 days of insertion xenogenic screws made of human bone showed significantly larger distance of extrusion of on average 173.8 μm compared to allogenic screws made of sheep bone of on average 27.8 and 29.95 μm of the titanium control group. Severe resorption processes with connective tissue interposition were found in the histomorphological analysis of the xenogenic screws in contrast to new bone formation and centripetal vascularization of the allogenic bone screw, as well as in processes of incorporation of the titanium control group. The study showed allogenic cortical bone screws as a substantial alternative to titanium screws with good biomechanical properties. In contrast to other reports a different result was shown for the xenogenic bone screws. They showed insufficient holding strength with confirmative histomorphological signs of degradation and insufficient osseointegration. Before common clinical use of xenogenic osteosynthetic material, further evaluation should be performed.

  6. [Resorbable rods and screws for fixation of ankle fractures. A randomized clinical prospective study].

    PubMed

    Springer, M A; van Binsbergen, E A; Patka, P; Bakker, F C; Haarman, H J

    1998-05-01

    A prospective randomized clinical trial was performed to evaluate the use of self-reinforced absorbable composites (Biofix) in the fixation of ankle fractures. The aim of this study was to demonstrate that fixation with Biofix rods and screws is as good as the standard A.O. fixation. The benefits of Biofix rods and screws are: a reduction in costs since no secondary operation is needed, prevention of stress-shielding and thereby diminishing the risk of bone porosity. Patients aged between 16 and 75 years old with closed, non-comminuted fractures of the lateral and/or medial malleolus and dislocation of the fracture fragments greater than 2 mm were included in the study. 22 patients were treated with Biofix rods and screws and the control group of 19 patients with a standard technique. After 3, 6 and 12 months, rontgenograms were taken. At the same time functional results were evaluated following the criteria of Olerud and Molander. Two patients were withdrawn from the trial for non-medical reasons. 22 patients (12 from the Biofix group, 10 from the AO group) operated two or more years ago were contacted to see if any complications had occurred since they were last seen. In 4 cases a Biofix screw broke down just beneath the head during insertion. This did not result in an insufficient fixation of the fracture. There were no early post-operative complications. The functional and rontgenological results in both groups were equal. In three cases a sterile sinus developed at the site of screw insertion. Biofix rods and screws, made of polylactic acid, are a good alternative for the fixation of fractures of the ankle. The use of resorbable fracture fixation material has the advantage that a second operation to remove osteosynthesis material is not necessary. The long term results are good. There is, however, a possibility of development of tissue reaction to the resorbable material.

  7. Shock-Absorbent Ball-Screw Mechanism

    NASA Technical Reports Server (NTRS)

    Hirr, Otto A., Jr.; Meneely, R. W.

    1986-01-01

    Actuator containing two ball screws in series employs Belleville springs to reduce impact loads, thereby increasing life expectancy. New application of springs increases reliability of equipment in which ball screws commonly used. Set of three springs within lower screw of ball-screw mechanism absorbs impacts that result when parts reach their upper and lower limits of movement. Mechanism designed with Belleville springs as shock-absorbing elements because springs have good energy-to-volume ratio and easily stacked to attain any stiffness and travel.

  8. Does higher screw density improve radiographic and clinical outcomes in adolescent idiopathic scoliosis? A systematic review and pooled analysis.

    PubMed

    Luo, Ming; Wang, Wengang; Shen, Mingkui; Luo, Xin; Xia, Lei

    2017-02-03

    OBJECTIVE The radiographic and clinical outcomes of low-density (LD) versus high-density (HD) screw constructs in patients with adolescent idiopathic scoliosis (AIS) treated with all-pedicle screw constructs are still controversial. A systematic review and pooled analysis were performed to compare radiographic, perioperative, and quality-of-life (QOL) outcomes and complications in patients with moderate AIS treated with LD or HD screw constructs. METHODS The MEDLINE, Embase, and Web of Science databases were searched for English-language articles addressing LD versus HD screw constructs in AIS patients treated with all-pedicle screw constructs. The division of LD and HD groups was based on relative screw density and screw techniques. This systematic analysis strictly followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, and all articles included in the analysis met the criteria specified in the guidelines. Two reviewers independently assessed the quality of the studies using the Newcastle-Ottawa Scale. Date on radiographic, perioperative, and QOL outcomes and complications were extracted from the included studies. RESULTS Twelve studies, involving a total of 827 patients (480 treated with LD constructs, 347 with HD), were analyzed-1 randomized controlled trial, 1 quasi-randomized controlled trial, and 10 retrospective studies. The patients' age at surgery, preoperative Cobb angle of the major curve, amount of thoracic kyphosis, and major curve flexibility were reasonably distributed, and no statistically significant differences were found. Regarding the outcomes at most recent follow-up, there were no significant differences in the Cobb angle of the major curve (mean difference 0.96°, 95% CI -0.06° to 1.98°, p = 0.06, I(2) = 1%), major curve correction (mean difference -0.72%, 95% CI -2.96% to 1.52%, p = 0.53, I(2) = 0%), thoracic kyphosis (mean difference -1.67°, 95% CI -4.59° to 1.25°, p = 0.26, I(2) = 79

  9. Absorbable screws through the greater trochanter do not disturb physeal growth: rabbit experiments.

    PubMed

    Gil-Albarova, J; Fini, M; Gil-Albarova, R; Melgosa, M; Aldini-Nicolo, N; Giardino, R; Seral, F

    1998-06-01

    We studied the effect of implantation of self-reinforced polyglycolic acid (SR-PGA) screws through the greater trochanter in rabbits. 15 rabbits aged 10 weeks had an SR-PGA screw inserted through the left trochanter physis. A similar drilling was made through the right greater trochanter without screw implantation. The animals were assigned to 3 groups of 5, and were killed after 1, 2 or 3 months. Radiographs of both femurs were obtained monthly and the articulo-trochanteric distance and the neck-shaft angle were measured. After killing the animals, a histological study was performed. The drilling on the right trochanter generated a bony bridge in all the animals. The SR-PGA screws did not give rise to an epiphysiodesis. The progressive peripheral degradation of the implants gave rise to the formation of only modest bridges, which were smaller in size than those observed in the control trochanter. Our findings suggest that absorbable PGA screws implanted through a growth plate cause only minor bone formation and no epiphyseodesis.

  10. Linear motion device and method for inserting and withdrawing control rods

    DOEpatents

    Smith, Jay E.

    1984-01-01

    A linear motion device, more specifically a control rod drive mechanism (CRDM) for inserting and withdrawing control rods into a reactor core, is capable of independently and sequentially positioning two sets of control rods with a single motor stator and rotor. The CRDM disclosed can control more than one control rod lead screw without incurring a substantial increase in the size of the mechanism.

  11. Twin screw granulation: steps in granule growth.

    PubMed

    Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2012-11-15

    The present work focuses on the study of the progression of granules in different compartments along the length of screws in a twin screw granulator (TSG). The effects of varying powder feed rate; liquid to solid ratio and viscosity of granulation liquid on properties of granules was studied. The bigger granules produced at the start of the process were found to change in terms of size, shape and strength along the screw length at all the conditions investigated. The granules became more spherical and their strength increased along the screw length. Tracer granules were also introduced in order to understand the role of kneading and conveying elements in the TSG. The kneading elements promoted consolidation and breakage while the conveying elements led to coalescence, breakage and some consolidation. The results presented here help to provide a qualitative and quantitative understanding of the twin screw granulation process.

  12. 100 Consecutive Cases of Degenerative Lumbar Conditions Using a Non-Threaded Locking Screw System With a 90-Degree Locking Cap

    PubMed Central

    Cunningham, Bryan W.; Tortolani, P. Justin; Fedder, Ira L.; Sefter, John C.; Davis, Charles

    2009-01-01

    Background This prospective study analyzes the perioperative outcomes and long-term fusion success of 100 consecutive lumbar degenerative cases. The cases were managed using a non-threaded locking screw system, in conjunction with polyetheretherketone (PEEK) cages, for posterior lumbar interbody fusion (PLIF) procedures. These 100 cases were compared to another prospective study treating patients with the same inclusion and exclusion criteria using conventional plate-based pedicle screw spinal instrumentation augmented with carbon fiber interbody cages. Methods A total of 167 operative levels were treated in 100 patients (51 single-level, 39 two-level and 10 three-level cases). Eleven cases were revisions and 67 patients received interbody fusion cages. Patients had an average of 22.8 ± 4.0 months followup. Results: There was one instrumentation failure but no significant subsidence at the interbody fusion level. The disc space height was restored as part of the surgical procedure at the interbody cage levels: from 7.5 ± 2.3 mm preoperative to 9.0 ± 2.1 mm postoperative. There were 2 cases of pseudarthrosis (2 / 100 = 2%). The average operative time for 1-level cases was 111 ± 25 minutes; for 2-level cases it was 132.4 ± 21.8 minutes; and for 3-level cases it was 162.6 ± 33 minutes. Blood loss averaged 800 ± 473 cc for 1-level cases, 1055 ± 408 cc for 2 levels, and 1155 ± 714 cc for 3 levels. The length of stay was similar between the 3 groups (4.4 ± 1.2 days for single-level cases, 4.7 ± 1.1 for 2 levels, and 5.0 ± 1.1 for 3 levels; P > .05). There were 3 incidental durotomies, and 4 other patients developed infections postoperatively that required reoperation. Conclusion The disc and foraminal heights can be restored and maintained with a unilateral cage and pedicle screw construct. Unilateral transforaminal lumbar interbody fusion using a PEEK cage combined with a non-threaded locking pedicle screw and rod system results in similar fusion rates to

  13. Simulation-based particle swarm optimization and mechanical validation of screw position and number for the fixation stability of a femoral locking compression plate.

    PubMed

    Lee, Chian-Her; Shih, Kao-Shang; Hsu, Ching-Chi; Cho, Tomas

    2014-01-01

    Locking compression plates (LCPs) have been used to fix femoral shaft fractures. Previous studies have attempted to identify the best LCP screw positions and numbers to achieve the fixation stability. However, the determined screw positions and numbers were mainly based on the surgeons' experiences. The aim of this study was to discover the best number and positions of LCP screws to achieve acceptable fixation stability. Three-dimensional numerical models of a fractured femur with the LCP were first developed. Then, the best screw position and number of LCPs were determined by using a simulation-based particle swarm optimization algorithm. Finally, the results of the numerical study were validated by conducting biomechanical tests. The results showed that the LCP with six locking screws resulted in the necessary fixation stability, and the best combination of positions of locking screws inserted into the LCP was 1-5-6-7-8-12 (three locking screws on either side of the bone fragment with two locking screws as close as practicable to the fracture site). In addition, the numerical models and algorithms developed in this study were validated by the biomechanical tests. Both the numerical and experimental results can provide clinical suggestions to surgeons and help them to understand the biomechanics of LCP systems.

  14. Pelvic Girdle Reconstruction Based on Spinal Fusion and Ischial Screw Fixation in a Case of Aneurysmal Bone Cyst

    PubMed Central

    Westphal, Florian; Carrero, Volker; Morlock, Michael; Schwieger, Karsten; Hille, Ekkehard; Delling, G.

    2003-01-01

    A case of lytic lesion of the pelvis in a 23-year-old woman is presented. A biopsy led to the diagnosis aneurysmal bone cyst (ABC). Due to the histologically very aggressive growth of the tumor, a low malignant osteosarcoma could not be excluded. In an initial operation the tumour, affecting the sacrum, the iliac crest and the lower lumbar spine was resected. Temporary restabilisation of the pelvic ring was achieved by a titanium plate. The histological examination of the entire tumour confirmed the diagnosis ABC. After 6 months, the MRI showed no recurrence. The observed tilt of the spine to the operated side on the sacral base prompted a second surgical procedure: a transpedicular fixation of L5 and L4 was connected via bent titanium stems to the ischium, where the fixation was achieved by two screws. This construction allowed the correction of the base angle and yielded a stable closure of the pelvic ring. The patient has now been followed for 6 years: the bone grafts have been incorporated and, in spite of radiological signs of screw loosening in the ischium, the patient is fully rehabilitated and free of symptoms. Pedicle screws in the lower spine can be recommended for fixation of a pelvic ring discontinuity. PMID:18521384

  15. Pelvic girdle reconstruction based on spinal fusion and ischial screw fixation in a case of aneurysmal bone cyst.

    PubMed

    Honl, Matthias; Westphal, Florian; Carrero, Volker; Morlock, Michael; Schwieger, Karsten; Hille, Ekkehard; Delling, G

    2003-01-01

    A case of lytic lesion of the pelvis in a 23-year-old woman is presented. A biopsy led to the diagnosis aneurysmal bone cyst (ABC). Due to the histologically very aggressive growth of the tumor, a low malignant osteosarcoma could not be excluded. In an initial operation the tumour, affecting the sacrum, the iliac crest and the lower lumbar spine was resected. Temporary restabilisation of the pelvic ring was achieved by a titanium plate. The histological examination of the entire tumour confirmed the diagnosis ABC. After 6 months, the MRI showed no recurrence. The observed tilt of the spine to the operated side on the sacral base prompted a second surgical procedure: a transpedicular fixation of L5 and L4 was connected via bent titanium stems to the ischium, where the fixation was achieved by two screws. This construction allowed the correction of the base angle and yielded a stable closure of the pelvic ring. The patient has now been followed for 6 years: the bone grafts have been incorporated and, in spite of radiological signs of screw loosening in the ischium, the patient is fully rehabilitated and free of symptoms. Pedicle screws in the lower spine can be recommended for fixation of a pelvic ring discontinuity.

  16. [Hypogastric abdominal wall reconstruction with a pedicled anterolateral thigh flap].

    PubMed

    Moullot, P; Philandrianos, C; Gonnelli, D; Casanova, D

    2014-10-01

    Looking at a full-thickness abdominal wall defect, it is necessary to use reconstructive surgery techniques. The authors present an original case of reconstruction of the abdominal wall, using an anterolateral thigh flap (ALT) harvested with vascularised fascia lata. We describe the advantages of this technique, which has rarely been used for this indication. An 80-year-old woman presenting a full-thickness abdominal wall defect of 15×18cm was reconstructed by a pedicled ALT flap. Skin wound healing was obtained within 15 days, with no complication. There was no donor site sequela. The pedicled ALT flap appears to be a good solution for hypogastric abdominal wall defect in a one step procedure. Vacularised fascia lata bring with the cutaneous flap is useful to reconstruct the abdominal fascia.

  17. Grommet Having Metal Insert

    DTIC Science & Technology

    1998-09-28

    axially with respect to the body. The 1 means for releasably securing a tool to the insert comprises 2 female threads formed on an inner surface of the...below 10 the flange 32. These surfaces 34, 36 are threaded ( female 11 threads) so that the end of a tool 38 having male threads can 12 engage the...further includes a rigid insert secured to the body in the 12 centrally located aperture. The insert has female threads formed 13 therein for releasably

  18. Segmental gracilis free flap based on secondary pedicles: anatomical study and clinical series.

    PubMed

    Cavadas, Pedro C; Sanz-Giménez-Rico, Juan R; Landín, Luis; Martínez-Soriano, Francisco

    2004-09-01

    The gracilis muscle has been used extensively in reconstructive surgery, based on the proximal dominant pedicle. In the literature, little attention has been paid to the secondary distal pedicles. The distribution of the secondary pedicles of the gracilis muscle was investigated in 20 cadaver thighs. The mean number of secondary pedicles was 2.2 (range, two to three). When two pedicles were present-the most common situation-they were located at a mean distance of 12.4 and 17.5 cm from the knee joint line. The most proximal secondary pedicle was injected with barium sulfate in five specimens, and constant and abundant connections with the main pedicle were noted. A series of seven clinical cases of segmental gracilis free muscle flaps based on a secondary pedicle is reported. The flaps were successfully transferred to reconstruct traumatic defects of limited size, with one case of partial necrosis caused by a technical error. The morbidity of this flap is minimal, the scar is well hidden, the muscle need not be sacrificed, elevation is fast and straightforward under tourniquet control, and the pedicle is sizable. This flap should be considered a viable option when a small, straightforward free flap is needed.

  19. Plastic pipe insertion

    SciTech Connect

    Diskin, J.

    1987-05-01

    In March 1987 KPL changed all that when the utility inserted 1,000 ft of 16-in. SDR 15.5 Phillips Driscopipe 8000 pipe with a wall thickness of 1.032-in., into an abandoned 24-in. cast-iron line in downtown Kansas City. This is believed to be the largest diameter insert removal job ever done for gas distribution in the U.S. For KPL it was a natural progression from the smaller sizes used earlier. The procedure is the same, and the operation was quick and comparatively simple. Lower construction costs were the bottom line because with insert renewal there is no need to cut up the streets, a major expense in any urban pipeline work. There are other significant costs savings as well because the insert renewal construction process is faster than other techniques.

  20. Ear tube insertion - slideshow

    MedlinePlus

    ... this page: //medlineplus.gov/ency/presentations/100045.htm Ear tube insertion - series—Normal anatomy To use the ... 4 Overview The eardrum (tympanic membrane) separates the ear canal from the middle ear. Review Date 8/ ...

  1. Screw-actuated displacement micropumps for thermoplastic microfluidics.

    PubMed

    Han, J Y; Rahmanian, O D; Kendall, E L; Fleming, N; DeVoe, D L

    2016-10-05

    The fabrication of on-chip displacement pumps integrated into thermoplastic chips is explored as a simple and low cost method for achieving precise and programmable flow control for disposable microfluidic systems. The displacement pumps consist of stainless steel screws inserted into threaded ports machined into a thermoplastic substrate which also serve as on-chip reagent storage reservoirs. Three different methods for pump sealing are investigated to enable high pressure flows without leakage, and software-defined control of multiple pumps is demonstrated in a self-contained platform using a compact and self-contained microcontroller for operation. Using this system, flow rates ranging from 0.5-40 μl min(-1) are demonstrated. The pumps are combined with on-chip burst valves to fully seal multiple reagents into fabricated chips while providing on-demand fluid distribution in a downstream microfluidic network, and demonstrated for the generation of size-tunable water-in-oil emulsions.

  2. Feasibility of detecting orthopaedic screw overtightening using acoustic emission.

    PubMed

    Pullin, Rhys; Wright, Bryan J; Kapur, Richard; McCrory, John P; Pearson, Matthew; Evans, Sam L; Crivelli, Davide

    2017-03-01

    A preliminary study of acoustic emission during orthopaedic screw fixation was performed using polyurethane foam as the bone-simulating material. Three sets of screws, a dynamic hip screw, a small fragment screw and a large fragment screw, were investigated, monitoring acoustic-emission activity during the screw tightening. In some specimens, screws were deliberately overtightened in order to investigate the feasibility of detecting the stripping torque in advance. One set of data was supported by load cell measurements to directly measure the axial load through the screw. Data showed that acoustic emission can give good indications of impending screw stripping; such indications are not available to the surgeon at the current state of the art using traditional torque measuring devices, and current practice relies on the surgeon's experience alone. The results suggest that acoustic emission may have the potential to prevent screw overtightening and bone tissue damage, eliminating one of the commonest sources of human error in such scenarios.

  3. Fixed-angle screws vs standard screws in acetabular prosthesis fixation: a cadaveric biomechanical study.

    PubMed

    Hugate, Ronald R; Dickey, Ian D; Chen, Qingshan; Wood, Christina M; Sim, Franklin H; Rock, Michael G

    2009-08-01

    Secure fixation of acetabular components in total hip arthroplasty can be challenging. The purpose of this study was to perform biomechanical analysis of cup fixation strength using fixed-angle vs standard screw fixation. Multihole, porous-backed acetabular prostheses were implanted in both acetabuli of 8 cadaveric pelves using standard press-fit techniques. Fixed-angle screws were used on the left side, and standard cancellous screws were used in the right. The use of fixed-angle screws enhanced acetabular fixation substantially under subfailure cyclic loading conditions and load-to-failure. The triradiate screw configuration increases the bending moment required to fail the specimens as well. Fixed-angle screws may be useful for achieving rigid fixation of acetabular prostheses in challenging clinical scenarios.

  4. Screw-released roller brake

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1999-01-01

    A screw-released roller brake including an input drive assembly, an output drive assembly, a plurality of locking sprags, a mechanical tripper nut for unlocking the sprags, and a casing therefor. The sprags consist of three dimensional (3-D) sprag members having pairs of contact surface regions which engage respective pairs of contact surface regions included in angular grooves or slots formed in the casing and the output drive assembly. The sprags operate to lock the output drive assembly to the casing to prevent rotation thereof in an idle mode of operation. In a drive mode of operation, the tripper is either self actuated or motor driven and is translated linearly up and down against a spline and at the limit of its travel rotates the sprags which unlock while coupling the input drive assembly to the output drive assembly so as to impart a turning motion thereto in either a clockwise or counterclockwise direction.

  5. Vertical-Screw-Auger Conveyer Feeder

    NASA Technical Reports Server (NTRS)

    Walton, Otis (Inventor); Vollmer, Hubert J. (Inventor)

    2016-01-01

    A conical feeder is attached to a vertically conveying screw auger. The feeder is equipped with scoops and rotated from the surface to force-feed regolith the auger. Additional scoops are possible by adding a cylindrical section above the conical funnel section. Such then allows the unit to collect material from swaths larger in diameter than the enclosing casing pipe of the screw auger. A third element includes a flexible screw auger. All three can be used in combination in microgravity and zero atmosphere environments to drill and recover a wide area of subsurface regolith and entrained volatiles through a single access point on the surface.

  6. Concomitant Correction of a Soft-Tissue Fenestration with Keratinised Tissue Augmentation By Using A Rotated Double-Pedicle Flap During Second-Stage Implant Surgery- A Case Report

    PubMed Central

    Reddy, Aileni Amarender; Kumar, P. Anoop; Sailaja, Sistla; Chakravarthy, Yshs

    2015-01-01

    Soft tissue deficiencies and defects around dental implants have been observed frequently. Soft-tissue defects after implant procedures originate from the process of modelling of periimplant mucosa and often cause aesthetic disharmony, food debris accumulation and soft tissue shrinkage. Periimplant mucogingival surgery focuses on creating an optimum band of keratinized tissue resulting in soft tissue architecture similar to the gingiva around natural teeth. A 23-year-old male reported to the Department of Periodontology with a complaint of gum soreness, foul smell and food accumulation at a site where a 3.75 x 11.5mm implant was placed previously. On clinical examination, fenestration of tissue above the cover screw was observed and there appeared to be a keratinized tissue of 1mm surrounding the implant. The case was managed by use of a rotated double-pedicle flap during second-stage implant surgery to correct the soft-tissue fenestration defect and to obtain a keratinized periimplant soft tissue. A periosteal bed was prepared by giving a horizontal incision at the mucogingival junction to a depth of 4 mm. Two split-thickness keratinized pedicles were dissected from the mesial and distal interproximal tissues near the implant. After rotation, both the pedicles were sutured to each other mid-buccally and the pedicles were rigidly immobilized with sutures. At 1 month, there was a 3mm band of stable and firm keratinized tissue over the underlying tissues. The procedure resulted in an aesthetic improvement due to enhanced soft tissue architecture and optimum integration between the peri-implant soft tissue and the final prosthesis. PMID:26816998

  7. The development and evaluation of individualized templates to assist transoral C2 articular mass or transpedicular screw placement in TARP-IV procedures: adult cadaver specimen study

    PubMed Central

    Li, Xue-Shi; Wu, Zeng-Hui; Xia, Hong; Ma, Xiang-Yang; Ai, Fu-Zhi; Zhang, Kai; Wang, Jian-Hua; Mai, Xiao-Hong; Yin, Qing-Shui

    2014-01-01

    OBJECTIVES: The transoral atlantoaxial reduction plate system treats irreducible atlantoaxial dislocation from transoral atlantoaxial reduction plate-I to transoral atlantoaxial reduction plate-III. However, this system has demonstrated problems associated with screw loosening, atlantoaxial fixation and concealed or manifest neurovascular injuries. This study sought to design a set of individualized templates to improve the accuracy of anterior C2 screw placement in the transoral atlantoaxial reduction plate-IV procedure. METHODS: A set of individualized templates was designed according to thin-slice computed tomography data obtained from 10 human cadavers. The templates contained cubic modules and drill guides to facilitate transoral atlantoaxial reduction plate positioning and anterior C2 screw placement. We performed 2 stages of cadaveric experiments with 2 cadavers in stage one and 8 in stage two. Finally, guided C2 screw placement was evaluated by reading postoperative computed tomography images and comparing the planned and inserted screw trajectories. RESULTS: There were two cortical breaching screws in stage one and three in stage two, but only the cortical breaching screws in stage one were ranked critical. In stage two, the planned entry points and the transverse angles of the anterior C2 screws could be simulated, whereas the declination angles could not be simulated due to intraoperative blockage of the drill bit and screwdriver by the upper teeth. CONCLUSIONS: It was feasible to use individualized templates to guide transoral C2 screw placement. Thus, these drill templates combined with transoral atlantoaxial reduction plate-IV, may improve the accuracy of transoral C2 screw placement and reduce related neurovascular complications. PMID:25518033

  8. Interfragmentary compression and pull-out properties of 6.5-mm AO cancellous lag screws in a uniform synthetic material during tightening procedures.

    PubMed

    Sun, Peidong; Xu, Daqiang; Zhao, Weidong; Jiao, Peifeng; Li, Zeyu; Liu, Chang; Ouyang, Jun

    2017-04-01

    AO lag screws are widely used in surgical intra-articular fracture treatment for anatomical reduction and rigid fixation. Interfragmentary compressive force (IFCF) and pull-out strength (POS) are two critical parameters generated by AO lag screws during tightening, and both of these parameters could be used to estimate screw insert conditions to prevent screw stripping. The aim of this study is to evaluate the IFCF and POS of AO cancellous screws inserted into uniform synthetic cancellous bone during tightening procedures. Seven synthetic cancellous bone blocks were used for this research. Each test contained two continuous portions as follows: the rotation test portion and the pull-out test portion. IFCF and POS were captured by the pressure transducer and the sensor of the test machine. The properties of IFCF and POS based on tightening degrees were obtained in this study. The ideal balance between POS and IFCF during screw tightening exists, and the peak values of these parameters cannot be simultaneously achieved. Moreover, rotation angles of 100-150° appear to serve as the optimum balance between IFCF and POS in the present study.

  9. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

    Smythe, Robert; Palmer, Dean; Gursel, Yekta; Reder, Leonard; Savedra, Raymond

    2004-01-01

    Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor . or equivalent) that provide linear motion controllable, in principle, to within increments .30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator.

  10. Helical rotary screw expander power system

    NASA Technical Reports Server (NTRS)

    Mckay, R. A.; Sprankle, R. S.

    1974-01-01

    An energy converter for the development of wet steam geothermal fields is described. A project to evaluate and characterize a helical rotary screw expander for geothermal applications is discussed. The helical screw expander is a positive displacement machine which can accept untreated corrosive mineralized water of any quality from a geothermal well. The subjects of corrosion, mineral deposition, the expansion process, and experience with prototype devices are reported.

  11. ALS insertion devices

    NASA Astrophysics Data System (ADS)

    Hoyer, E.; Chin, J.; Halbach, K.; Hassenzahl, W. V.; Humphries, D.; Kincaid, B.; Lancaster, H.; Plate, D.

    1991-08-01

    The Advanced Light Source (ALS), the first US third generation synchrotron radiation source, is currently under construction at the Lawrence Berkeley Laboratory. The low-emittance, 1.5 GeV electron storage ring and the insertion devices are specifically designed to produce high brightness beams in the UV to soft X-Ray range. The planned initial complement of insertion devices includes four 4.6 m long undulators, with period lengths of 3.9 cm, 5.0 cm (2) and 8.0 cm, and a 2.9 m long wiggler of 16 cm period length. Undulator design is well advanced and fabrication has begun on the 5.0 cm and 8.0 cm period length undulators. This paper discusses ALS insertion device requirements; general design philosophy; and design of the magnetic structure, support structure/drive systems, control system and vacuum system.

  12. Ball Screw Actuator Including a Stop with an Integral Guide

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Perek, John (Inventor); Geck, Kellan (Inventor)

    2015-01-01

    An actuator includes a housing assembly, a ball nut, a ball screw, and a ball screw stop. The ball nut is rotationally mounted in the housing assembly, is adapted to receive an input torque, and is configured, upon receipt thereof, to rotate and supply a drive force. The ball screw is mounted within the housing assembly and extends through the ball nut. The ball screw has a first end and a second end, and is coupled to receive the drive force from the ball nut. The ball screw is configured, upon receipt of the drive force, to selectively translate between a stow position and a deploy position. The ball screw stop is mounted on the ball screw to translate therewith and is configured to at selectively engage the housing assembly while the ball screw is translating, and engage the ball nut when the ball screw is in the deploy position.

  13. Spectacles under Pedicles: Eyewear Modification with the Paramedian Forehead Flap

    PubMed Central

    Qu, Linda T.; Kelpin, John P.; Komorowska-Timek, Ewa

    2016-01-01

    Summary: The paramedian forehead flap is a widely used method of nasal reconstruction. The flap requires a bridge of tissue from forehead to the nose, for a period of 2 to 3 weeks, before it can be divided at a second procedure. During this time, patients often have difficulty positioning and wearing their eyewear underneath the pedicle of the flap. Here we present a novel approach to the problem. It requires only a simple modification to the patient’s eyewear and greatly facilitates wear and removal. PMID:27622084

  14. Periosteal Pedicle Flap Harvested during Vestibular Extension for Root Coverage

    PubMed Central

    Kumar, Shubham; Gupta, Krishna Kumar; Agrawal, Rahul; Srivastava, Pratima; Soni, Shalabh

    2015-01-01

    Root exposure along with inadequate vestibular depth is a common clinical finding. Treatment option includes many techniques to treat such defects for obtaining predictable root coverage. Normally, the vestibular depth is increased first followed by a second surgery for root coverage. The present case report describes a single-stage technique for vestibular extension and root coverage in a single tooth by using the Periosteal Pedicle Flap (PPF). This technique involves no donor site morbidity and allows for reflection of sufficient amount of periosteal flap tissue with its own blood supply at the surgical site, thus increasing the chances of success of root coverage with simultaneous increase in vestibular depth. PMID:26788377

  15. Standard Waste Box Lid Screw Removal Option Testing

    SciTech Connect

    Anast, Kurt Roy

    2016-03-11

    This report provides results from test work conducted to resolve the removal of screws securing the standard waste box (SWB) lids that hold the remediated nitrate salt (RNS) drums. The test work evaluated equipment and process alternatives for removing the 42 screws that hold the SWB lid in place. The screws were secured with a red Loctite thread locker that makes removal very difficult because the rivets that the screw threads into would slip before the screw could be freed from the rivet, making it impossible to remove the screw and therefore the SWB lid.

  16. Thionoglycine as a multifunctional spectroscopic reporter of screw-sense preference in helical foldamers.

    PubMed

    De Poli, Matteo; Clayden, Jonathan

    2014-02-07

    A single thionoglycine (glycine thioamide, -HNCH2C(=S)-) residue inserted into a peptide foldamer provides both a pair of germinal protons for use as a (1)H NMR stereochemical probe and a chromophore giving rise to a well defined Cotton effect in CD. Comparison of the response of these two features to a local helically chiral environment validates them as independent methods for quantifying the conformational screw-sense preference of a helical oligomer, in this case a peptide made of repeated Aib units. The sign of the Cotton effect provides a measure of the sign of the screw-sense preference, while both the chemical shift separation of the anisochronous signals of the glycine CH2 group and the magnitude of the Cotton effect give an estimate of the helicity excess of the oligomer. The thionoglycine unit is readily introduced synthetically by a thionation of a BocGlyAibOMe dipeptide.

  17. [Image-guided bone consolidation in oncology: Cementoplasty and percutaneous screw fixation].

    PubMed

    Buy, Xavier; Cazzato, Roberto Luigi; Catena, Vittorio; Roubaud, Guilhem; Kind, Michele; Palussiere, Jean

    2017-03-17

    Bone metastases are a common finding in oncology. They often induce pain but also fractures which impair quality of life, especially when involving weight-bearing bones. Percutaneous image-guided consolidation techniques play a major role for the management of bone metastases. Cementoplasty aims to stabilize bone and control pain by injecting acrylic cement into a weakened bone. This minimally invasive technique has proven its efficacy for bones submitted to compression forces: vertebra, acetabular roof, and condyles. However, long bone diaphysis should be treated with caution due to lower resistance of the cement subject to torsional forces. The recent improvements of navigation systems allow percutaneous image-guided screw fixation without requiring open surgery. This fast-track procedure avoids postponing introduction of systemic therapies. If needed, cementoplasty can be combined with screw insertion to ensure better anchoring in major osteolysis. Interventional radiology bone consolidation techniques increase the therapeutic field in oncology. A multidisciplinary approach remains mandatory to select the best indications.

  18. Preventing surgical complications: A survey on surgeons' perception of intra-articular malleolar screw misplacement in a cadaveric study

    PubMed Central

    2011-01-01

    Background Intra-articular hardware penetration can occur during osteosynthesis of ankle fractures, jeopardizing patients' outcomes. The intraoperative recognition of misplaced screws may be difficult due to the challenge of adequate interpretation of specific radiographic views. The present study was designed to investigate the diagnostic accuracy of standardized radiographic ankle views to determine the accuracy of diagnosis for intra-articular hardware placement of medial malleolar screws in a cadaveric model. Methods Nine preserved human cadaveric lower extremity specimens were used. Under direct visualization, two 4.0 mm cancellous screws were inserted into the medial malleolus. Each specimen was analyzed radiographically using antero-posterior (AP) and mortise views. The X-rays were randomly uploaded on a CD-ROM and included in a survey submitted to ten selected orthopaedic surgeons. The "Standards for Reporting of Diagnostic Accuracy" (STARD) questionnaire was used to determine the surgeons' perception of accuracy of screw placement in the medial malleolus. The selection of items was based on evidence whenever possible, therefore the "inconclusive" category was added. Inter and intraobserver variations were analyzed by kappa statistics to measure the amount of agreement. Results There was a poor level of agreement (kappa 0.4) both in the AP and in the mortise view among all the examiners. Associating the two x-rays, the agreement remained poor (kappa 0.4). In the cases in which there was a diagnosis of articular penetration, there was a poor agreement related to which of the screws was intra-articular. The number of "inconclusive" responses was low and constant, without a statistically significant difference between the subspecialists Conclusion The routine intraoperative radiographic imaging of the ankle is difficult to interpret and unreliable for detection of intra-articular hardware penetration. We therefore recommend to reposition medial malleolar

  19. Development of a DIPG Orthotopic Model in Mice Using an Implantable Guide-Screw System

    PubMed Central

    Domínguez, Pablo D.; Idoate, Miguel Angel; Xipell, Enric; Patiño-García, Ana; Gonzalez-Huarriz, Marisol; García-Moure, Marc; Junier, Marie-Pierre; Chneiweiss, Hervé; El-Habr, Elías; Diez-Valle, Ricardo; Tejada-Solís, Sonia

    2017-01-01

    Objective In this work we set to develop and to validate a new in vivo frameless orthotopic Diffuse Intrinsic Pontine Glioma (DIPG) model based in the implantation of a guide-screw system. Methods It consisted of a guide-screw also called bolt, a Hamilton syringe with a 26-gauge needle and an insulin-like 15-gauge needle. The guide screw is 2.6 mm in length and harbors a 0.5 mm central hole which accepts the needle of the Hamilton syringe avoiding a theoretical displacement during insertion. The guide-screw is fixed on the mouse skull according to the coordinates: 1mm right to and 0.8 mm posterior to lambda. To reach the pons the Hamilton syringe is adjusted to a 6.5 mm depth using a cuff that serves as a stopper. This system allows delivering not only cells but also any kind of intratumoral chemotherapy, antibodies or gene/viral therapies. Results The guide-screw was successfully implanted in 10 immunodeficient mice and the animals were inoculated with DIPG human cell lines during the same anesthetic period. All the mice developed severe neurologic symptoms and had a median overall survival of 95 days ranging the time of death from 81 to 116 days. Histopathological analysis confirmed tumor into the pons in all animals confirming the validity of this model. Conclusion Here we presented a reproducible and frameless DIPG model that allows for rapid evaluation of tumorigenicity and efficacy of chemotherapeutic or gene therapy products delivered intratumorally to the pons. PMID:28107439

  20. Twin screw wet granulation: Binder delivery.

    PubMed

    Saleh, Mohammed F; Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2015-06-20

    The effects of three ways of binder delivery into the twin screw granulator (TSG) on the residence time, torque, properties of granules (size, shape, strength) and binder distribution were studied. The binder distribution was visualised through the transparent barrel using high speed imaging as well as quantified using offline technique. Furthermore, the effect of binder delivery and the change of screw configuration (conveying elements only and conveying elements with kneading elements) on the surface velocity of granules across the screw channel were investigated using particle image velocimetry (PIV). The binder was delivered in three ways; all solid binder incorporated with powder mixture, 50% of solid binder mixed with powder mixture and 50% mixed with water, all the solid binder dissolved in water. Incorporation of all solid binder with powder mixture resulted in the relatively longer residence time and higher torque, narrower granule size distribution, more spherical granules, weaker big-sized granules, stronger small-sized granules and better binder distribution compared to that in other two ways. The surface velocity of granules showed variation from one screw to another as a result of uneven liquid distribution as well as shown a reduction while introducing the kneading elements into the screw configuration.

  1. Traumatic Fracture of Thin Pedicles Secondary to Extradural Meningeal Cyst

    PubMed Central

    Yanni, Daniel S.; Mammis, Antonios; Thaker, Nikhil G.; Goldstein, Ira M.

    2011-01-01

    Spinal dural meningoceles and diverticula are meningeal cysts that have a myriad of clinical presentations and sequelae, secondary to local mass effect. Our objective is to report a technical case report, illustrating a traumatic spinal injury with multiple pedicle fractures, secondary to atrophic lumbar pedicles as well as the diagnostic workup and surgical management of this problem. Posterior lumbar decompression, resection of the meningeal cyst, ligation of the cyst ostium, instrumentation, and fusion were performed with the assistance of intraoperative isocentric fluoroscopy. The cyst's point of communication was successfully located with intraoperative fluoroscopy and the lesion was successfully excised. We suggest that patients with traumatic spinal injuries, having evidence of pre-existing anomalous bony architecture, undergo advanced imaging studies, to rule out intraspinal pathology. The positive clinical and radiographic results support the removal and closure of the pre-existing meningeal cyst at the time of treatment of traumatic spinal injury. Intraoperative isocentric fluoroscopy is a helpful tool in the operative management of these lesions. PMID:22022654

  2. Impact of screw configuration on the particle size distribution of granules produced by twin screw granulation.

    PubMed

    Vercruysse, J; Burggraeve, A; Fonteyne, M; Cappuyns, P; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

    2015-02-01

    Twin screw granulation (TSG) has been reported by different research groups as an attractive technology for continuous wet granulation. However, in contrast to fluidized bed granulation, granules produced via this technique typically have a wide and multimodal particle size distribution (PSD), resulting in suboptimal flow properties. The aim of the current study was to evaluate the impact of granulator screw configuration on the PSD of granules produced by TSG. Experiments were performed using a 25 mm co-rotating twin screw granulator, being part of the ConsiGma™-25 system (a fully continuous from-powder-to-tablet manufacturing line from GEA Pharma Systems). Besides the screw elements conventionally used for TSG (conveying and kneading elements), alternative designs of screw elements (tooth-mixing-elements (TME), screw mixing elements (SME) and cutters) were investigated using an α-lactose monohydrate formulation granulated with distilled water. Granulation with only conveying elements resulted in wide and multimodal PSD. Using kneading elements, the width of the PSD could be partially narrowed and the liquid distribution was more homogeneous. However, still a significant fraction of oversized agglomerates was obtained. Implementing additional kneading elements or cutters in the final section of the screw configuration was not beneficial. Furthermore, granulation with only TME or SME had limited impact on the width of the PSD. Promising results were obtained by combining kneading elements with SME, as for these configurations the PSD was narrower and shifted to the size fractions suitable for tableting.

  3. Thought Insertion Clarified

    PubMed Central

    Ratcliffe, Matthew; Wilkinson, Sam

    2016-01-01

    ‘Thought insertion’ in schizophrenia involves somehow experiencing one’s own thoughts as someone else’s. Some philosophers try to make sense of this by distinguishing between ownership and agency: one still experiences oneself as the owner of an inserted thought but attributes it to another agency. In this paper, we propose that thought insertion involves experiencing thought contents as alien, rather than episodes of thinking. To make our case, we compare thought insertion to certain experiences of ‘verbal hallucination’ and show that they amount to different descriptions of the same phenomenon: a quasi-perceptual experience of thought content. We add that the agency/ownership distinction is unhelpful here. What requires explanation is not why a person experiences a type of intentional state without the usual sense of agency, but why she experiences herself as the agent of one type of intentional state rather than another. We conclude by sketching an account of how this might happen. PMID:28123340

  4. Screw expander for light duty diesel engines

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Preliminary selection and sizing of a positive displacement screw compressor-expander subsystem for a light-duty adiabatic diesel engine; development of a mathematical model to describe overall efficiencies for the screw compressor and expander; simulation of operation to establish overall efficiency for a range of design parameters and at given engine operating points; simulation to establish potential net power output at light-duty diesel operating points; analytical determination of mass moments of inertia for the rotors and inertia of the compressor-expander subsystem; and preparation of engineering layout drawings of the compressor and expander are discussed. As a result of this work, it was concluded that the screw compressor and expander designed for light-duty diesel engine applications are viable alternatives to turbo-compound systems, with acceptable efficiencies for both units, and only a moderate effect on the transient response.

  5. A modified technique for removing a failed abutment screw from an implant with a custom guide tube.

    PubMed

    Taira, Yohsuke; Sawase, Takashi

    2012-04-01

    Fracture of abutment screw is a serious prosthodontic complication. When the abutment screw is fractured at the junction of the screw shank and screw thread, removal of the fractured screw fragment from the screw hole can be difficult. This article describes a modified technique for removing the failed abutment screw with a custom guide tube and tungsten carbide bur. The failed screw can be removed speedily without damaging the screw hole of the implant body or the screw threads.

  6. Evaluation with evoked and spontaneous electromyography during lumbar instrumentation: a prospective study.

    PubMed

    Welch, W C; Rose, R D; Balzer, J R; Jacobs, G B

    1997-09-01

    The neuroanatomical structures that approximate the bony pedicles of the lumbar spine allow little room for technical error or compromise of the bone during pedicle screw insertion. Currently available neurophysiological monitoring techniques detect compromised bone and nerve root injury after it occurs. The purpose of this prospective study is to evaluate the reliability and efficacy of a unique neurophysiological monitoring technique. This technique provides immediate evaluation of pedicle cortical bone integrity in patients undergoing lumbar fusion with instrumentation by using electrified surgical instruments throughout the pedicle screw fusion procedure. Spontaneous electromyographic (EMG) activity was also monitored. Intraoperative evoked EMG stimulation was performed using a pedicle probe and feeler as monopolar stimulators during the insertion of 164 pedicle bone screws in 32 patients. The EMG response to subthreshold stimulation intensities indicated cortical bone compromise. Immediate and conclusive feedback via evoked EMG activity using stimulating pedicle probes in appropriate muscle groups was successful in identifying pedicle cortical bone compromise in four patients. One false-negative evoked EMG study was noted but was identified via spontaneous EMG activity. Intraoperative EMG monitoring alerted the surgeon that redirection of the pedicle probe or screw was necessary to avoid nerve root irritation or injury and served as an early warning system. Evoked EMG stimulation proved to be reliable and efficacious, especially when used in combination with spontaneous EMG. This technique may provide an added safeguard during implant placement procedures at centers where intraoperative neurophysiological monitoring is routinely performed.

  7. Subcutaneous pedicled V-Y advancement flap for surgical reconstruction of the auricle of the ear.

    PubMed

    González-Sixto, B; Pérez-Bustillo, A; Otero-Rivas, M M; Rodríguez-Prieto, M Á

    2014-05-01

    The subcutaneous pedicled V-Y advancement flap is useful for the repair of small and medium-sized defects in areas where it is easy to obtain a good subcutaneous pedicle (upper lip, cheek, eyebrow, and nasal tip and ala). The almost complete absence of subcutaneous tissue on the anterior aspect of the auricle of the ear can limit the use of this approach in this region. We present 4 patients in whom subcutaneous pedicled V-Y advancement flaps were used to repair surgical defects of the helix, scaphoid fossa, and antitragus, achieving a good functional and aesthetic result in all cases.

  8. Spline-Screw Multiple-Rotation Mechanism

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

    Mechanism functions like combined robotic gripper and nut runner. Spline-screw multiple-rotation mechanism related to spline-screw payload-fastening system described in (GSC-13454). Incorporated as subsystem in alternative version of system. Mechanism functions like combination of robotic gripper and nut runner; provides both secure grip and rotary actuation of other parts of system. Used in system in which no need to make or break electrical connections to payload during robotic installation or removal of payload. More complicated version needed to make and break electrical connections. Mechanism mounted in payload.

  9. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Intraosseous fixation screw or wire. 872.4880... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  10. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Intraosseous fixation screw or wire. 872.4880... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  11. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Intraosseous fixation screw or wire. 872.4880... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  12. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Intraosseous fixation screw or wire. 872.4880... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  13. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Intraosseous fixation screw or wire. 872.4880... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  14. Linear motion device and method for inserting and withdrawing control rods

    DOEpatents

    Smith, J.E.

    Disclosed is a linear motion device and more specifically a control rod drive mechanism (CRDM) for inserting and withdrawing control rods into a reactor core. The CRDM and method disclosed is capable of independently and sequentially positioning two sets of control rods with a single motor stator and rotor. The CRDM disclosed can control more than one control rod lead screw without incurring a substantial increase in the size of the mechanism.

  15. Inserts Automatically Lubricate Ball Bearings

    NASA Technical Reports Server (NTRS)

    Hager, J. A.

    1983-01-01

    Inserts on ball-separator ring of ball bearings provide continuous film of lubricant on ball surfaces. Inserts are machined or molded. Small inserts in ball pockets provide steady supply of lubricant. Technique is utilized on equipment for which maintenance is often poor and lubrication interval is uncertain, such as household appliances, automobiles, and marine engines.

  16. Periosteal pedicle graft: A novel root coverage approach.

    PubMed

    Shah, Mishal Piyush; Patel, Akash Prahlad; Shah, Kinnari Mishal

    2015-01-01

    Gingival recession along with reduced width of attached gingiva and inadequate vestibular depth is a very common finding. Many techniques have been adopted in order to treat such defects and obtain predictable root coverage. Several graft procedures are used to obtain the coverage, but they have not been able to deliver predictable and satisfactory results (except connective tissue graft). Some of them also resulted in the secondary surgical site that was very uncomfortable for the patients. There was an intense need for a technique that provides not only good and predictable root coverage, but also reduces the need for secondary surgical site. Hence, this paper describes a single stage technique for increasing the width of attached gingiva and root coverage by using the periosteal pedicle graft.

  17. Fatigue strength of common tibial intramedullary nail distal locking screws

    PubMed Central

    Griffin, Lanny V; Harris, Robert M; Zubak, Joseph J

    2009-01-01

    Background Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws. Methods Fatigue tests were conducted to simulate a comminuted fracture that was treated by IM nailing assuming that all load was carried by the screws. Each screw type was tested ten times in a single screw configuration. One screw type was tested an additional ten times in a two-screw parallel configuration. Fatigue tests were performed using a servohydraulic materials testing system and custom fixturing that simulated screws placed in the distal region of an appropriately sized tibial IM nail. Fatigue loads were estimated based on a seventy-five kilogram individual at full weight bearing. The test duration was one million cycles (roughly one year), or screw fracture, whichever occurred first. Failure analysis of a representative sample of titanium alloy and stainless steel screws included scanning electron microscopy (SEM) and quantitative metallography. Results The average fatigue life of a single screw with a diameter of 4.0 mm was 1200 cycles, which would correspond roughly to half a day of full weight bearing. Single screws with a diameter of 4.5 mm or larger have approximately a 50 percent probability of withstanding a week of weight bearing, whereas a single 5.0 mm diameter screw has greater than 90 percent probability of

  18. Improvements to the single screw extruder

    NASA Technical Reports Server (NTRS)

    Hiemenz, C.; Ziegmann, G.; Franzkoch, B.; Hoffmanns, W.; Michaeli, W.

    1977-01-01

    The extrusion on a single screw extruder is examined. The process is divided into several steps: the dosage of the materials to be conveyed; the modification of the shape of the feeding opening which influences the feeding process and consequently the throughput of the extruder; optimizing the shape of the feeding zone to meet the specific material requirements; and plasticizing and homogenizing.

  19. Nylon screws make inexpensive coil forms

    NASA Technical Reports Server (NTRS)

    Aucoin, G.; Rosenthal, C.

    1978-01-01

    Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

  20. Improvements In Ball-Screw Linear Actuators

    NASA Technical Reports Server (NTRS)

    Iskenderian, Theodore; Joffe, Benjamin; Summers, Robert

    1996-01-01

    Report describes modifications of design of type of ball-screw linear actuator driven by dc motor, with linear-displacement feedback via linear variable-differential transformer (LVDT). Actuators used to position spacecraft engines to direct thrust. Modifications directed toward ensuring reliable and predictable operation during planned 12-year cruise and interval of hard use at end of cruise.

  1. Long Term Follow up and Patient Satisfaction after Reduction Mammoplasty: Superomedial versus Inferior Pedicle

    PubMed Central

    Makboul, Mohamed; Abdelhamid, Mahmoud; Al-Attar, Ghada

    2017-01-01

    BACKGROUND Surgery for hypertrophied breast represents a challenge for plastic surgeons. The search for a good cosmetic breast has led to the development of many techniques. Objectives for reduction mammoplasty are to achieve elevated, symmetrical breasts, with round shape, good projection, small cicatrices that are not very perceptible, and a lasting result. METHODS This study was carried out on 60 cases who had done reduction mammoplasty from January 2009 to December 2014. All patients were examined and asked for late post-operative results and overall patients’ satisfaction. RESULTS Long term projection and contour of the breast were more satisfactory among patients who had superomedial pedicle with a statistical significant difference. No statistical significant difference was observed between patients undergone either types of operations concerning breast symmetry, nipple symmetry and sensation. The mean score of satisfaction was higher among patients undergone superomedial pedicle than inferior pedicle. CONCLUSION The superomedial pedicle shows better long term cosmetic result in reduction mammoplasty. PMID:28289618

  2. Initial strength of highpressed extrusion poly-L-lactide screw.

    PubMed

    Matsushita, T; Nakamura, K; Shiro, R; Takazawa, H; Tsuji, K; Kurokawa, T

    2000-01-01

    We developed a poly-L-lactide material strengthened by a highpressed extrusion technique. The bending strength of a rod made of that material is higher than that of the same size rods made of poly-L-lactide strengthened by drawing technique, which has been used in clinical cases. The purposes of this study were, first to clarify if the initial strength of extrusion-strengthened poly-L-lactide screws is higher than that of draw-strengthened poly-L-lactide screws, and, secondly to investigate the safe torque for driving the screws in clinical usage. In accordance with AO screw design, five kinds of screws were manufactured. In a pull-out test and a twisting test using a DYRACON blocks, the strength of the highpressed extrusion-strengthened poly-L-lactide material was also higher than that of the draw-strengthened poly-L-lactide material after milling into screws. In the simulation using minipig bones and the 4.5 mm psi cortical screws, when the thickness was below 0.5 mm, between 0.5 and 2 mm or over 3 mm, the break locations were in the cortical bone, the thread of the screw and the under head fillet respectively. In the simulation using minipig bones and the 4.0 mm psi cancellous screws, breakage occurred not on the screws but on the cancellous bone in all screws.

  3. Surgical screw segmentation for mobile C-arm CT devices

    NASA Astrophysics Data System (ADS)

    Görres, Joseph; Brehler, Michael; Franke, Jochen; Wolf, Ivo; Vetter, Sven Y.; Grützner, Paul A.; Meinzer, Hans-Peter; Nabers, Diana

    2014-03-01

    Calcaneal fractures are commonly treated by open reduction and internal fixation. An anatomical reconstruction of involved joints is mandatory to prevent cartilage damage and premature arthritis. In order to avoid intraarticular screw placements, the use of mobile C-arm CT devices is required. However, for analyzing the screw placement in detail, a time-consuming human-computer interaction is necessary to navigate through 3D images and therefore to view a single screw in detail. Established interaction procedures of repeatedly positioning and rotating sectional planes are inconvenient and impede the intraoperative assessment of the screw positioning. To simplify the interaction with 3D images, we propose an automatic screw segmentation that allows for an immediate selection of relevant sectional planes. Our algorithm consists of three major steps. At first, cylindrical characteristics are determined from local gradient structures with the help of RANSAC. In a second step, a DBScan clustering algorithm is applied to group similar cylinder characteristics. Each detected cluster represents a screw, whose determined location is then refined by a cylinder-to-image registration in a third step. Our evaluation with 309 screws in 50 images shows robust and precise results. The algorithm detected 98% (303) of the screws correctly. Thirteen clusters led to falsely identified screws. The mean distance error for the screw tip was 0.8 +/- 0.8 mm and for the screw head 1.2 +/- 1 mm. The mean orientation error was 1.4 +/- 1.2 degrees.

  4. Effect of Vertical Misfit on Screw Joint Stability of Implant-Supported Crowns

    NASA Astrophysics Data System (ADS)

    Assunção, Wirley Gonçalves; Delben, Juliana Aparecida; Tabata, Lucas Fernando; Barão, Valentim Adelino Ricardo; Gomes, Érica Alves

    2011-08-01

    The passive fit between prosthesis and implant is a relevant factor for screw joint stability and treatment success. The aim of this study was to evaluate the influence of vertical misfit in abutment-implant interface on preload maintenance of retention screw of implant-supported crowns. The crowns were fabricated with different abutments and veneering materials and divided into 5 groups ( n = 12): Gold UCLA abutments cast in gold alloy veneered with ceramic (Group I) and resin (Group II), UCLA abutments cast in titanium veneered with ceramic (Group III) and resin (Group IV), and zirconia abutments with ceramic veneering (Group V). The crowns were attached to implants by gold retention screws with 35-N cm insertion torque. Specimens were submitted to mechanical cycling up to 106 cycles. Measurements of detorque and vertical misfit in abutment-implant interface were performed before and after mechanical cycling. ANOVA revealed statistically significant difference ( P < 0.05) among groups for vertical misfit measured before and after mechanical cycling. The abutments cast in titanium exhibited the highest misfit values. Pearson correlation test did not demonstrate significant correlation ( P > 0.05) between vertical misfit and detorque value. It was concluded that vertical misfit did not influence torque maintenance and the abutments cast in titanium exhibited the highest misfit values.

  5. Intradermal Infiltration of Local Anesthetic—Rapid and Bloodless Deepithelialization of the Breast Pedicle

    PubMed Central

    Bennett, Katelyn G.

    2017-01-01

    Summary: Breast reduction is one of the most commonly performed plastic surgery procedures, and pedicle deepithelialization remains a time-consuming step of the operation. This is especially true when using an inferior pedicle. We present a novel technique of intradermal infiltration of the breast pedicle with local anesthetic to facilitate efficient, bloodless deepithelialization. The senior author uses a 20-ml syringe to inject 0.25% lidocaine and 1:400,000 epinephrine just beneath the epidermis of the breast pedicle to create a series of wheals. Approximately 20 ml of local anesthetic is used per pedicle. After injection of local anesthetic, the breast pedicle is deepithelialized in less than 3 minutes. The plane is bloodless, allowing improved visualization secondary to the epinephrine-induced hemostasis. The senior author has had only one case of nipple necrosis in 20 years of experience. Intradermal infiltration of local anesthetic with epinephrine hydrodissects between the epidermis and dermis and provides hemostasis to facilitate rapid deepithelialization. PMID:28280667

  6. Facility target insert shielding assessment

    SciTech Connect

    Mocko, Michal

    2015-10-06

    Main objective of this report is to assess the basic shielding requirements for the vertical target insert and retrieval port. We used the baseline design for the vertical target insert in our calculations. The insert sits in the 12”-diameter cylindrical shaft extending from the service alley in the top floor of the facility all the way down to the target location. The target retrieval mechanism is a long rod with the target assembly attached and running the entire length of the vertical shaft. The insert also houses the helium cooling supply and return lines each with 2” diameter. In the present study we focused on calculating the neutron and photon dose rate fields on top of the target insert/retrieval mechanism in the service alley. Additionally, we studied a few prototypical configurations of the shielding layers in the vertical insert as well as on the top.

  7. Impact of screw elements on continuous granulation with a twin-screw extruder.

    PubMed

    Djuric, Dejan; Kleinebudde, Peter

    2008-11-01

    The influence of different screw element types on wet granulation process with a twin-screw extruder was investigated. Lactose granules were prepared with different screw configurations such as conveying, combing mixer and kneading elements. The use of kneading blocks led to an almost complete agglomeration of lactose, whereas kneading and combing mixer elements resulted in smaller granules in comparison. Granule porosity varied between 17.4% and 50.6%. Granule friability values ranged from 1.2% to 38.5%. Conveying elements led to the most porous and friable granules, whereas kneading blocks produced the densest and least friable granules. Combing mixer elements produced granules with median properties. A linear correlation between granule porosity and the natural logarithm of granule friability was detected. Flowability of granules was also influenced by the element type. Compressed granules with higher granule porosities resulted in tablets with higher tensile strength values and vice versa. Twin-screw extruders proved to be a versatile tool for wet granulation. By the choice of a suitable screw element granule and tablet characteristics were influenced.

  8. Impedance calculation for ferrite inserts

    SciTech Connect

    Breitzmann, S.C.; Lee, S.Y.; Ng, K.Y.; /Fermilab

    2005-01-01

    Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.

  9. Analysis of Modeling Parameters on Threaded Screws.

    SciTech Connect

    Vigil, Miquela S.; Brake, Matthew Robert; Vangoethem, Douglas

    2015-06-01

    Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry cause issues when generating a mesh of the model. This paper will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.

  10. Twin screw granulation - review of current progress.

    PubMed

    Thompson, M R

    2015-01-01

    Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique.

  11. Mechanisms for Complex Chromosomal Insertions

    PubMed Central

    Szafranski, Przemyslaw; Akdemir, Zeynep Coban; Yuan, Bo; Cooper, Mitchell L.; Magriñá, Maria A.; Bacino, Carlos A.; Lalani, Seema R.; Patel, Ankita; Song, Rodger H.; Bi, Weimin; Cheung, Sau Wai; Carvalho, Claudia M. B.; Lupski, James R.

    2016-01-01

    Chromosomal insertions are genomic rearrangements with a chromosome segment inserted into a non-homologous chromosome or a non-adjacent locus on the same chromosome or the other homologue, constituting ~2% of nonrecurrent copy-number gains. Little is known about the molecular mechanisms of their formation. We identified 16 individuals with complex insertions among 56,000 individuals tested at Baylor Genetics using clinical array comparative genomic hybridization (aCGH) and fluorescence in situ hybridization (FISH). Custom high-density aCGH was performed on 10 individuals with available DNA, and breakpoint junctions were fine-mapped at nucleotide resolution by long-range PCR and DNA sequencing in 6 individuals to glean insights into potential mechanisms of formation. We observed microhomologies and templated insertions at the breakpoint junctions, resembling the breakpoint junction signatures found in complex genomic rearrangements generated by replication-based mechanism(s) with iterative template switches. In addition, we analyzed 5 families with apparently balanced insertion in one parent detected by FISH analysis and found that 3 parents had additional small copy-number variants (CNVs) at one or both sides of the inserting fragments as well as at the inserted sites. We propose that replicative repair can result in interchromosomal complex insertions generated through chromothripsis-like chromoanasynthesis involving two or three chromosomes, and cause a significant fraction of apparently balanced insertions harboring small flanking CNVs. PMID:27880765

  12. Central pedicled breast reduction technique in male patients after massive weight loss.

    PubMed

    Stoff, Alexander; Velasco-Laguardia, Fernando J; Richter, Dirk F

    2012-03-01

    Male patients after massive weight loss often suffer from redundant skin and soft tissue in the anterior and lateral chest region, causing various deformities of pseudogynecomastia. Techniques with free or pedicled nipple-areola complex (NAC) transposition are widely accepted. The authors present their approach to male breast reduction with preservation of the NAC on a central dermoglandular pedicle and a wide elliptical tissue excision of breast and lateral thorax tissue in combination with liposuction. Male breast reduction was performed on patients after moderate to massive weight loss due to diet or bariatric procedures. Former procedures included free nipple-areola grafts or inferior pedicled techniques for NAC preservation. As a modification, we performed a central pedicled breast reduction on nine male patients with excessive liposuction of the pedicle and a horizontal elliptical skin removal, allowing for sufficient tissue removal at the lateral thorax. From October 2010 until June 2011, nine male patients had central pedicled breast reconstructions after massive weight loss. Mean age was 29.1 years, mean preoperative body mass index was 29.2, and mean preoperative weight loss was 63.9 kg. The chest wall improvement was rated "very good" by eight patients. No major complications occurred in all nine patients. Male chest deformities after massive weight loss can be dealt by several approaches. The optimal scar positioning and the preservation of NAC may be the most challenging aspects of these procedures. Therefore, the preservation of the NAC on a central dermoglandular pedicle with a horizontal submammary scar course may optimize the esthetic outcome.

  13. Biomechanical analysis of expansion screws and cortical screws used for ventral plate fixation on the cervical spine

    PubMed Central

    Ullrich, Bernhard; Huber, Gerd; Morlock, Michael M.

    2009-01-01

    Compared to bicortical screws, the surgical risk of injuring intraspinal structures can be minimized with the use of monocortical screws. However, this reduction should not be achieved at the expense of the stability of the fixation. With monocortical stabilization, the expansion screws have the potential of absorbing high loads. Therefore, they are expected to be a suitable alternative to bicortical screws for revision surgeries and in osteoporotic bone. The purpose of this in vitro study was to investigate the stiffness of the two screw-plate systems used for ventral stabilization of the cervical spine, by focusing on the suitability of expansion screws as tools for revision treatments. The study was conducted in ten functional units of human cervical spines. The device sample stiffness was determined for four conditions using a turning moment of 2.25 N m each around one of the three principle axes. The conditions were native, destabilized, primarily stabilized with one of the screw-plate systems, followed by secondary stabilization using the expansion screw implant. The stabilized samples achieved a comparable, in most cases higher stiffness than the native samples. The samples undergoing secondary stabilization using expansion screws tend to display greater stiffness for all three axes compared to the primarily stabilized samples. The achieved tightening moment of the screws was higher than the one achieved with primary fixation. Both plates revealed similar primary stability. Revision surgeries with secondary instrumentation achieve a high stiffness of the screwed up segments. Monocortical expansion screws combined with a trapezoidal plate allow ventral stabilization of the cervical spine that is comparable to the plate fixation using bicortical screws. PMID:19588171

  14. Nonlinear contact analysis of preload in dental implant screws.

    PubMed

    Sakaguchi, R L; Borgersen, S E

    1995-01-01

    Clinical studies indicate that loosening or fracture of dental implant prostheses occurs in 5% to 45% of cases during the first year. The nature of loosening or displacement of prosthetic components is complex, since it involves cycling fatigue, oral fluids, and varied chewing patterns and loads. A finite element contact analysis method was used to study the load-transfer mechanism between prosthetic components caused by torque application to the threaded fasteners used for assembly. Screw elongation is achieved while allowing for elastic recovery of the screw to produce a clamping force on the fastened elements. Clamping forces were additive along the axis of the prosthetic components. When the gold retaining screw is fastened into the abutment screw, clamping force on the implant is increased at the expense of decreasing the clamping force at the abutment screw-abutment interface by 50%. Maximum tensile stresses in the screws after preload were less than 55% of the yield stress.

  15. Passage of an Anterior Odontoid Screw through Gastrointestinal Tract

    PubMed Central

    Leitner, L.; Brückmann, C. I.; Gilg, M. M.; Bratschitsch, G.; Radl, R.

    2017-01-01

    Purpose. Anterior screw fixation has become a popular surgical treatment method for instable odontoid fractures. Screw loosening and migration are a rare, severe complication following anterior odontoid fixation, which can lead to esophagus perforation and requires revision operation. Methods. We report a case of screw loosening and migration after anterior odontoid fixation, which perforated the esophagus and was excreted without complications in a 78-year-old male patient. Results. A ventral dislocated anterior screw perforated through the esophagus after eight years after implantation and was excreted through the gastrointestinal (GI) tract. At a 6-month follow-up after the event the patient was asymptomatic. Conclusion. Extrusion via the GI tract is not safe enough to be considered as a treatment option for loosened screws. Some improvements could be implemented to prevent such an incident. Furthermore, this case is a fine example that recent preoperative imaging is mandatory before revision surgery for screw loosening. PMID:28194180

  16. Pullout strength of fixation screws from polymethylmethacrylate bone cement.

    PubMed

    Flahiff, C M; Gober, G A; Nicholas, R W

    1995-05-01

    Polymethylmethacrylate bone cement is often used to fill voids and increase the strength of osteoporotic and pathological bone. However, it is unclear as to which method of cement augmentation provides optimal screw fixation. This study was conducted to determine which of the current cement augmentation techniques provides the strongest construct when used in association with orthopaedic fixation screws. Pullout strength was determined for screws placed in sawbones with no cement, soft cement, doughy cement and hard cement after drilling and tapping. All cement-screw constructs were significantly stronger than the no cement group. Screws placed in doughy cement had a significantly higher pullout force than those placed in hard cement. Pullout strength of screws placed in soft cement was intermediate between the other cement techniques but not significantly different from either group.

  17. Research on an intelligent ball-screw measuring instrument

    NASA Astrophysics Data System (ADS)

    Fu, Pan; Chen, Yong-Le; Zeng, Quan-Kun; Xiang, Lin-Kui

    1993-09-01

    Ball screw are widely used in the steering-gear of automobile, aero-mechanism, machine tools and precision instrument. Since the thread form is referred to as a Gothic arch, so it is difficult to measure the ball screw. The traditional screw measuring method is "three wire" method or "three ball" method. The weakness of these methods is that the measuring process is too complicated or the measuring precision is not high. We have developed an intelligent ball screw measuring instrument. The instrument can measure the ball center diameter of ball screw. Using a new measuring method("two wire and one ball" method), the instrument has high measuring precision, high reliability and it is easy to operate.The 8098 microcomputer system in the instrument can control the measuring process and accomplish data collecting and processing automatically. This measuring instrument can be used on the production site for fast and precise measurement of ball screw.

  18. Sink Inserts for Flood Prevention

    NASA Astrophysics Data System (ADS)

    Fleming, Fraser F.; Bodnar, Daniel J.; Hardesty, David L.

    2004-09-01

    A simple, inexpensive insert is described for preventing flooding in lab sinks. The insert is essentially a tube with slots cut into the side that fits snugly into the drain outlet, preventing water buildup and providing additional drainage sites to avoid constriction by small lab items and paper towels.

  19. Screws, Propellers and Fans Based on a Mobius Strip

    NASA Technical Reports Server (NTRS)

    Seiner, John M.; Backley, Floyd D.; Gilinsky, Mikhail

    1998-01-01

    A Mobius strip concept is intended for improving the working efficiency of propellers and screws. Applications involve cooling, boat propellers, mixing in appliance, blenders, and helicopters. Several Mobius shaped screws for the average size kitchen mixers have been made and tested. The tests have shown that the mixer with the Mobius shaped screw pair is most efficient, and saves more than 30% of the electric power by comparison with the standard. The created video film about these tests illustrates efficiency of Mobius shaped screws.

  20. Retrieval of a stripped abutment screw: a clinical report.

    PubMed

    Maalhagh-Fard, Ahmad; Jacobs, Leyvee Cabanilla

    2010-10-01

    Mechanical complications, such as loosening or damaging of the prosthetic components of an osseointegrated implant, may occur. Stripping of the implant abutment screw head can be a serious problem which can render an implant unusable. This report describes a clinical situation involving a patient who presented with a fractured screw-retained interim crown. Upon further examination, it was determined that the abutment screw head was stripped. There was limited access and visibility in this situation since the implant was a bone-level implant. The procedure used for the removal of the stripped abutment screw head is described in detail in this clinical report.

  1. Long-term follow-up and patient satisfaction after reduction mammoplasty: Superomedial versus inferior pedicle

    PubMed Central

    Makboul, Mohamed; Abdelhamid, Mahmoud S.; Al-Attar, Ghada S.

    2016-01-01

    Background: Surgery for hypertrophied breasts represents a challenge for plastic surgeons. The search for a good post-surgical cosmetic breast has led to the development of many techniques. Objectives for reduction mammoplasty are to achieve elevated, symmetrical breasts, a round shape, good projection, small cicatrices that are not very perceptible, and a lasting result. Patients and Methods: This study was carried out on sixty cases who had done reduction mammoplasty from January 2009 to December 2014. All patients were examined and were asked for late post-operative results and overall patients' satisfaction. Results: Long-term projection and contour of the breast were more satisfactory among patients who had superomedial pedicle with a statistically significant difference. No statistically significant difference was observed between patients underwent either superomedial or inferior pedicle reduction mammoplasty with regard to breast shape symmetry, nipple symmetry and sensation. The mean score for satisfaction was higher among patients who underwent superomedial pedicle rather than the inferior pedicle method. Conclusion: The superomedial pedicle shows better long-term cosmetic results. PMID:27833284

  2. Pedicled posteromedial thigh (PMT) flap: A new alternative for groin defect reconstruction.

    PubMed

    Scaglioni, Mario F; Enrique Carrillo Jimenez, Leonardo; Kuo, Yur-Ren; Chen, Yen-Chou

    2015-11-26

    The posterior medial thigh is mainly vascularized by the profunda femoris artery (PFA), which nourishes the adductor magnus muscle and overlying skin, to supply a number of perforators that can potentially be used as pedicles for local perforator flaps. Here we present two cases utilizing the pedicled posteromedial thigh flap (PMT) to reconstruct the groin defects. Two patients underwent resection for metastatic malignant melanoma resulting in large defects of the groin with exposure of major inguinal vessels; the dimensions of the skin defects were 15 cm × 5 cm and 16 cm × 6 cm, two ipsilateral pedicled PMT flaps were designed to cover the defects. The pedicled PMT flaps were based on perforators arising from the PFA and were transposed through a submuscular tunnel into the defect. The postoperative course was uneventful and the wounds were reconstructed successfully. The pedicled PMT flap may be an option for reconstruction of groin defects and could be incorporated into the armamentarium of the reconstructive microsurgeon. © 2015 Wiley Periodicals, Inc. Microsurgery, 2015.

  3. Use of the coventry infant hip screw in the treatment of nonunion of fractures of the distal humerus.

    PubMed

    Simonis, R B; Nuñez, V A; Khaleel, A

    2003-01-01

    Between 1993 and 2000 we treated 14 patients with nonunion of fractures of the distal humerus; 11 had already had previous fixation which had failed. The mean time to surgery was 21 months after injury. All the fractures were very low which made it difficult to obtain a firm hold of the small distal fragment. The problem of fixation was addressed by inserting a Coventry infant hip screw into the humeral condyles. The screw has a thread of wide diameter which gives excellent purchase on the small distal fragment. The condyles can then be compressed on to the humeral shaft using a 4.5 mm narrow tibial dynamic plate. Of these 14 difficult cases of nonunion, 12 progressed to union.

  4. Can we predict the insertion torque using the bone density around the implant?

    PubMed

    Wada, M; Suganami, T; Sogo, M; Maeda, Y

    2016-02-01

    The purpose of this study was to examine the correlation between initial stability and bone density in patients undergoing implant treatment. Twenty-five screw-type dental implants were inserted in 12 patients. All patients underwent multi-detector computed tomography (CT) examination prior to implant insertion. The implant sockets were prepared according to the drilling protocol, and peak insertion torque values were measured. CT values around the implants were measured using preoperatively scanned CT data, which were combined with actual implant positions. Spearman's rank correlation coefficient was used to investigate the correlation between insertion torque values and CT values (in Hounsfield units, HU). Twenty-three implants (8 or 10 mm in length) were inserted in the mandibular molar region and two (10mm length) in the maxillary molar region. The mean CT value of the 8-mm implants was 508.6 ± 187.0 HU and mean insertion torque was 27.2 ± 12.1 N·cm; for the 10-mm implants, these values were 579.6 ± 224.3 HU and 28.1 ± 14.6 N·cm, respectively. Statistical analysis revealed a strong positive correlation between the insertion torque and mean CT values (r=0.699, 8 mm; r=0.771, 10 mm). The results revealed that bone density around the implant is a useful index. This study indicates that preoperative CT may enable the prediction of initial implant stability.

  5. Finite element analysis of osteosynthesis screw fixation in the bone stock: an appropriate method for automatic screw modelling.

    PubMed

    Wieding, Jan; Souffrant, Robert; Fritsche, Andreas; Mittelmeier, Wolfram; Bader, Rainer

    2012-01-01

    The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent

  6. Safety screw fixation technique in a case of coracoid base fracture with acromioclavicular dislocation and coracoid base cross-sectional size data from a computed axial tomography study.

    PubMed

    Kawasaki, Yoshiteru; Hirano, Tetsuya; Miyatake, Katsutoshi; Fujii, Koji; Takeda, Yoshitsugu

    2014-07-01

    Coracoid base fracture accompanied by acromioclavicular joint dislocation with intact coracoclavicular ligaments is a rare injury. Generally, an open reduction with screw fixation is the first treatment choice, as it protects the important structures around the coracoid process. This report presents a new technique of screw fixation for coracoid base fracture and provides anatomic information on cross-sectional size of the coracoid base obtained by computed tomography (CT). An axial image of the coracoid base was visualized over the neck of the scapula, and a guidewire was inserted into this circle under fluoroscopic guidance. The wire was inserted easily into the neck of scapula across the coracoid base fracture with imaging in only 1 plane. In addition, 25 measurements of the coracoid base were made in 25 subjects on axial CT images. Average length of the long and short axes at the thinnest part of the coracoid base was 13.9 ± 2.0 mm (range 10.6-17.0) and 10.5 ± 2.2 mm (6.6-15.1), respectively. This new screw fixation technique and measurement data on the coracoid base may be beneficial for safety screw fixation of coracoid base fracture.

  7. Screw Placement and Osteoplasty Under Computed Tomographic-Fluoroscopic Guidance in a Case of Advanced Metastatic Destruction of the Iliosacral Joint

    SciTech Connect

    Trumm, Christoph Gregor; Rubenbauer, Bianca; Piltz, Stefan; Reiser, Maximilian F.; Hoffmann, Ralf-Thorsten

    2011-02-15

    We present a case of combined surgical screw placement and osteoplasty guided by computed tomography-fluoroscopy (CTF) in a 68-year-old man with unilateral osteolytic destruction and a pathological fracture of the iliosacral joint due to a metastasis from renal cell carcinoma. The patient experienced intractable lower back pain that was refractory to analgesia. After transarterial particle and coil embolization of the tumor-feeding vessels in the angiography unit, the procedure was performed under general anesthesia by an interdisciplinary team of interventional radiologists and trauma surgeons. Under intermittent single-shot CTF, two K wires were inserted into the left iliosacral joint from a lateral transiliac approach at the S1 level followed by two self-tapping surgical screws. Continuous CTF was used for monitoring of the subsequent polymethylmethacrylate injection through two vertebroplasty cannulas for further stabilization of the screw threads within the osteolytic sacral ala. Both the screw placement and cement injection were successful, with no complications occurring during or after the procedure. With additional nonsteroidal anti-inflammatory and opioid medication, the patient reported a marked decrease in his lower back pain and was able to move independently again at the 3-month follow-up assessment. In our patient with intolerable back pain due to tumor destruction and consequent pathological fracture of the iliosacral joint, CTF-guided iliosacral screw placement combined with osteoplasty was successful with respect to joint stabilization and a reduction in the need for analgesic therapy.

  8. Magnesium Alloys as a Biomaterial for Degradable Craniofacial Screws

    PubMed Central

    Henderson, Sarah E.; Verdelis, Konstantinos; Maiti, Spandan; Pal, Siladitya; Chung, William L.; Chou, Da-Tren; Kumta, Prashant N.; Almarza, Alejandro J.

    2014-01-01

    Recently, magnesium (Mg) alloys have received significant attention as a potential biomaterial for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available Mg-alloys (pure Mg and AZ31) in-vivo in a rabbit mandible. First, Mg-alloy screws were compared to stainless steel screws in an in-vitro pull-out test and determined to have a similar holding strength (~40N). A finite element model of the screw was created using the pull-out test data, and the model can be used for future Mg-alloy screw design. Then, Mg-alloy screws were implanted for 4, 8, and 12 weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12 weeks. MicroCT (computed tomography) was used to assess bone remodeling and Mg-alloy degradation, both visually and qualitatively through volume fraction measurements for all time points. Histologic analysis was also completed for the Mg-alloys at 12 weeks. The results showed that craniofacial bone remodeling occurred around both Mg-alloy screw types. Pure Mg had a different degradation profile than AZ31, however bone growth occurred around both screw types. The degradation rate of both Mg-alloy screw types in the bone marrow space and the muscle were faster than in the cortical bone space at 12 weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg-alloys for craniofacial applications. PMID:24384125

  9. Radius graft pedicled on the anterior interosseous artery for recurrent ulnar nonunion.

    PubMed

    Andro, C; Richou, J; Schiele, P; Hu, W; Le Nen, D

    2011-06-01

    Recurrent ulnar nonunion challenges the functional prognosis and raises major problems concerning the best therapeutic strategy to follow. The case of a female patient presenting recurrent nonunion of the ulnar diaphysis despite successive treatments is reported. The radius graft pedicled on the anterior interosseous artery from a retrograde approach obtained bone union in 3 months with no functional sequelae. For the first time, we propose a therapeutic alternative calling on a proximally pedicled anterior interosseous flap. This technique can be performed under locoregional anesthesia and does not sacrifice the main artery of the forearm. However, the size of the graft does not entirely compensate for segmentary bone loss. The radius graft pedicled on the anterior interosseus artery is an inventive technique that can solve the problem of difficult ulna nonunions without the disadvantages of vascularized fibula harvesting.

  10. The use of the serratus anterior muscle vascular pedicle as recipient site in DIEP flap transfer for breast reconstruction.

    PubMed

    Santanelli di Pompeo, Fabio; Longo, Benedetto; Laporta, Rosaria; Pagnoni, Marco; Cavalieri, Enrico

    2014-04-01

    Currently, the choice for recipient vessels in microvascular breast reconstruction is made between axillary and internal mammary regions. The authors report their experience with anastomosis to a new, unconventional, axillary recipient vessel, the serratus anterior muscle vascular pedicle. Among 340 deep inferior epigastric perforator (DIEP) flap breast reconstructions performed between 2004 and 2013, 11 were successfully revascularised to the serratus anterior (SA) pedicle: In three cases, complications led to a salvage procedure, while in eight cases, anastomosis to this recipient site was electively planned. The pedicle was constantly present, with calibre always comparable to that of flap's pedicle. At the mean 24-month follow-up, no recipient site complications were observed. The SA muscle pedicle resulted as a reliable choice in salvage procedures and a suitable option for recipient vessel selection in elective cases.

  11. Wet granulation in a twin-screw extruder: implications of screw design.

    PubMed

    Thompson, M R; Sun, J

    2010-04-01

    Wet granulation in twin-screw extrusion machinery is an attractive technology for the continuous processing of pharmaceuticals. The performance of this machinery is integrally tied to its screw design yet little fundamental knowledge exists in this emerging field for granulation to intelligently create, troubleshoot, and scale-up such processes. This study endeavored to systematically examine the influence of different commercially available screw elements on the flow behavior and granulation mechanics of lactose monohydrate saturated at low concentration (5-12%, w/w) with an aqueous polyvinyl-pyrrolidone binder. The results of the work showed that current screw elements could be successfully incorporated into designs for wet granulation, to tailor the particle size as well as particle shape of an agglomerate product. Conveying elements for cohesive granular flows were shown to perform similar to their use in polymer processing, as effective transport units with low specific mechanical energy input. The conveying zones provided little significant change to the particle size or shape, though the degree of channel fill in these sections had a significant influence on the more energy-intensive mixing elements studied. The standard mixing elements for this machine, kneading blocks and comb mixers, were found to be effective for generating coarser particles, though their mechanisms of granulation differed significantly.

  12. Dynamic Change of CD34 Level during the Survival Process of Narrow Pedicle Flap

    PubMed Central

    Wu, Lijun; Zhao, Tianlan; Yu, Daojiang; Chen, Qi; Han, Wenya; Yu, Wenyuan; Sun, Wei

    2015-01-01

    Objective To evaluate the dynamic change of CD34 level during the survival process of narrow pedicle flaps. Methods Twenty-five white pigs were randomly and equally divided into 5 experimental groups. Five different type of narrow pedicle with different length-to-width ratio were employed, and each type of narrow pedicle was covered with 5 different size random flaps and which was classified into A, B, C, D and E for 5 groups. Group A was control group. Each type narrow pedicle with 5 different skin flaps were implanted onto the back of the pigs along the midline of back with a reverse direction. A 0.3 cm×0.3 cm full thickness skin flap in the middle of distal segment was collected and on 3rd, 5th, 7th and 14th days of post-operation. The expression of CD34 was measured by immunohistochemistry and enzyme-linked immunosorbent (ELISA). Results Histological examination showed that with the increasing of length-to-width ratio of the narrow pedicle skin flaps, the expression of CD34 increased in the skin flaps. Increased level of CD34 was found on 3rd day post-operation, and the peak expression was found on 7th day. Persistent high level of CD34 was found until 14th day. Conclusion Increased CD34 level in the distal skin flap, there is the association between CD34 level and ischemia injury. Moreover, CD34 expression plays an important role during the repair processes of pedicle flaps. PMID:26561392

  13. Injection of coal by screw feed

    NASA Technical Reports Server (NTRS)

    Fisher, R.

    1977-01-01

    The use of the screw feeder for injecting solids through a 20 to 30 psi barrier is common practice in the cement making industry. An analytical extrapolation of that design, accounting for pressure holding characteristics of a column of solids, shows that coal can be fed to zones at several hundred psi with minimal or no loss of gas. A series of curves showing the calculated pressure gradient through a moving column of solids is presented. Mean particle size, solids velocity, and column length are parameters. Further study of this system to evaluate practicality is recommended.

  14. Roller screw electric motor ventricular assist device.

    PubMed

    Richenbacher, W E; Pae, W E; Magovern, J A; Rosenberg, G; Snyder, A J; Pierce, W S

    1986-01-01

    The roller screw electric VAD is easier to manufacture and 25% lighter than the previously described drum cam model. This device requires 12 to 15 W to pump 6 to 8 l/min with minimal hemolysis. The motor drive has functioned for periods up to 93 days in vivo with no measurable wear. The compliance chamber volume varies by 100 cc during VAD function but does so while maintaining pressure variations below 15 mmHg. Compliance chamber volume loss of 2 to 5 cc/day is explained by gas transport through SPU. The subcutaneous sampling port provides ready access to the sealed system.

  15. Salvage of extensively burned upper limbs by a pedicled latissimus dorsi flap.

    PubMed

    Delay, E; Foyatier, J L; el Kollali, R; Comparin, J P; Weil, E; Latarjet, J

    1995-09-01

    Very deep burns of the arm and elbow lead to soft tissue necrosis and infection with exposure of important structures. Aggressive debridement should be performed as early as possible to cut the vicious circle, and the defect, which may be extensive, should be covered by well-vascularized tissues. The reliability and versatility of the pedicled latissimus dorsi muscle or musculocutaneous flap make it our first choice in the management of this problem. A retrospective study of three patients for whom salvage of the upper limb has been achieved by the use of a pedicled latissimus dorsi flap is presented, illustrating the advantages of this technique.

  16. [Loosening of a Calcaneo-Stop Screw after Trampolining].

    PubMed

    Trieb, K; Fingernagel, T; Petershofer, A; Hofstaetter, S G

    2015-06-01

    Flexible flatfoot is a common malalignment in the paediatric population. Arthroereisis with a calcaneo-stop screw is an effective surgical procedure for treating juvenile flexible flatfoot after conservative measures have been fully exploited. In the present report, we describe the case of a loosening of a calcaneo-stop screw in a 12-year-old youth after excessive trampolining.

  17. Periodic Stresses in Gyroscopic Bodies, with Applications to Air Screws

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1918-01-01

    Report discusses periodic stresses in gyroscopic bodies with applications to air screws caused by particle mass. Report concludes that all modern air screws obey the laws found for plane groups of particles. In particular the two-bladers exert on the shaft a rhythmic gyroscopic torque; the multibladers a steady one; both easily calculable for any given conditions of motion and mass distribution.

  18. Percutaneously inserted central catheter - infants

    MedlinePlus

    PICC - infants; PQC - infants; Pic line - infants; Per-Q cath - infants ... A percutaneously inserted central catheter (PICC) is a long, very thin, soft plastic tube that is put into a small blood vessel. This article addresses PICCs in ...

  19. Tool Removes Coil-Spring Thread Inserts

    NASA Technical Reports Server (NTRS)

    Collins, Gerald J., Jr.; Swenson, Gary J.; Mcclellan, J. Scott

    1991-01-01

    Tool removes coil-spring thread inserts from threaded holes. Threads into hole, pries insert loose, grips insert, then pulls insert to thread it out of hole. Effects essentially reverse of insertion process to ease removal and avoid further damage to threaded inner surface of hole.

  20. A simple model of throughput calculation for single screw

    NASA Astrophysics Data System (ADS)

    Béreaux, Yves; Charmeau, Jean-Yves; Moguedet, Maël

    2007-04-01

    To be able to predict the throughput of a single-screw extruder or the metering time of an injection moulding machine for a given screw geometry, set of processing conditions and polymeric material is important both for practical and designing purposes. Our simple model show that the screw geometry is the most important parameter, followed by polymer rheology and processing conditions. Melting properties and length seem to intervene to a lesser extent. The calculations hinges on the idea of viewing the entire screw as a pump, conveying a solid and a molten fraction. The evolution of the solid fraction is the essence of the plastication process, but under particular circumstances, its influence on the throughput is nil. This allows us to get a very good estimate on the throughput and pressure development along the screw. Our calculations are compared to different sets of experiments available from the literature. We have consistent agreement both in throughput and pressure with published data.

  1. A four lumen screwing device for multiparametric brain monitoring.

    PubMed

    Feuerstein, T H; Langemann, H; Gratzl, O; Mendelowitsch, A

    2000-01-01

    We describe multiparametric monitoring in severe head trauma using a new screwing device. Our aim was to create a screw which would make the implantation of the probes and thus multiparametric monitoring easier. The new screw allows us to implant 3 probes (microdialysis, Paratrend and an intracranial pressure device) through one burr hole. The screw has four channels, the fourth being for ventricular drainage. We monitored 13 patients with severe head trauma (GCS = 3-8) for up to 7 days. Brain tissue pO2, pCO2, pH, and temperature were measured on-line with the Paratrend 7 machine. The microdialytic parameters glucose, lactate, pyruvate and glutamate were determined semi on-line with a CMA 600 enzymatic analyser. There were no complications in any of the patients that could be ascribed to the screw.

  2. Ball Screw Actuator Including an Axial Soft Stop

    NASA Technical Reports Server (NTRS)

    Wingett, Paul T. (Inventor); Forrest, Steven Talbert (Inventor); Abel, Steve (Inventor); Woessner, George (Inventor); Hanlon, Casey (Inventor)

    2016-01-01

    An actuator includes an actuator housing, a ball screw, and an axial soft stop assembly. The ball screw extends through the actuator housing and has a first end and a second end. The ball screw is coupled to receive a drive force and is configured, upon receipt of the drive force, to selectively move in a retract direction and an extend direction. The axial soft stop assembly is disposed within the actuator housing. The axial soft stop assembly is configured to be selectively engaged by the ball screw and, upon being engaged thereby, to translate, with compliance, a predetermined distance in the extend direction, and to prevent further movement of the ball screw upon translating the predetermined distance.

  3. Asymmetric distribution in twin screw granulation.

    PubMed

    Chan Seem, Tim; Rowson, Neil A; Gabbott, Ian; de Matas, Marcel; Reynolds, Gavin K; Ingram, Andy

    2016-09-01

    Positron Emission Particle Tracking (PEPT) was successfully employed to validate measured transverse asymmetry in material distribution in the conveying zones of a Twin Screw Granulator (TSG). Flow asymmetry was established to be a property of the granulator geometry and dependent on fill level. The liquid distribution of granules as a function of fill level was determined. High flow asymmetry at low fill level negatively affects granule nucleation leading to high variance in final uniformity. Wetting of material during nucleation was identified as a critical parameter in determining final granule uniformity and fill level is highlighted as a crucial control factor in achieving this. Flow asymmetry of dry material in conveying zones upstream of binder fluid injection leads to poor non-uniform wetting at nucleation and results in heterogeneous final product. The granule formation mechanism of 60°F kneading blocks is suggested to be primarily breakage of agglomerates formed during nucleation. Optimisation of screw configuration would be required to provide secondary growth. This work shows how fill dependent flow regimes affect granulation mechanisms.

  4. Scar due to skin incision for screw fixation through the transbuccal approach after sagittal split ramus osteotomy.

    PubMed

    Muto, Toshitaka

    2012-05-01

    Most rigid fixation techniques after sagittal split ramus osteotomies of the mandible involve the transbuccal approach. A skin incision in the cheek carries with it possible undesirable sequelae, such as noticeable scarring. The aim of this study was to investigate whether there is scarring in the face after this technique. For screw insertion, a 5-mm stab incision was performed on 40 Japanese patients (20 men and 20 women) with class III occlusion. After surgery, gross examination (via the naked eyes) of the skin incision was performed monthly for 1 year by the same oral surgeon. In all cases, the skin incision had disappeared by 1 year after the surgery.

  5. In vitro characteristics of a bioabsorbable suspension screw and suture system for endoscopic brow lift surgery.

    PubMed

    Pietrzak, William S; Eppley, Barry L

    2007-03-01

    The time requirement for endoscopic subperiosteal brow lift fixation is as little as 10-14 days. Many types of bioabsorbable fixation have been applied to this procedure, including bioabsorbable suture coupled with a bioabsorbable bone anchor, with excellent outcomes. Typically, the anchor and suture materials differ, each having their own hydrolytic strength loss profile. The dynamic relationship between the instantaneous state of degradation of the bone anchor and the suture components can affect fixation strength and failure mode, a poorly understood phenomenon. We examined the use of 2x5 mm PLLA-PGA (82:18) copolymer screws containing a suture eyelet in the head, paired with one of four types of bioabsorbable suture (2-0 and 3-0 Vicryl and 2-0 and 3-0 PDS-II), in a model system designed to mimic brow lift fixation. Constructs were inserted into a synthetic bone substrate and incubated in pH 7.4 buffer at 37 degrees C for up to 3 weeks, then loaded to failure. Initial failure loads were dependent upon suture size but not suture material, with 2-0 suture constructs (63-70N) failing at twice the load of the 3-0 suture constructs (30-35N). The following 3 week strength retentions were obtained: 40-55% for 2-0 and 3-0 Vicryl suture, 100% for 3-0 PDS-II suture, and 58% for 2-0 PDS-II suture constructs. The predominant failure mode was suture breakage at the knot, with the later intervals utilizing 2-0 PDS-II suture including some screw head failures. This suspension screw, when coupled with an appropriate suture, appears to have suitable mechanical properties for endoscopic brow lift fixation.

  6. In vivo evaluation of immediately loaded stainless steel and titanium orthodontic screws in a growing bone.

    PubMed

    Gritsch, Kerstin; Laroche, Norbert; Bonnet, Jeanne-Marie; Exbrayat, Patrick; Morgon, Laurent; Rabilloud, Muriel; Grosgogeat, Brigitte

    2013-01-01

    The present work intends to evaluate the use of immediate loaded orthodontic screws in a growing model, and to study the specific bone response. Thirty-two screws (half of stainless steel and half of titanium) were inserted in the alveolar bone of 8 growing pigs. The devices were immediately loaded with a 100 g orthodontic force. Two loading periods were assessed: 4 and 12 weeks. Both systems of screws were clinically assessed. Histological observations and histomorphometric analysis evaluated the percent of "bone-to-implant contact" and static and dynamic bone parameters in the vicinity of the devices (test zone) and in a bone area located 1.5 cm posterior to the devices (control zone). Both systems exhibit similar responses for the survival rate; 87.5% and 81.3% for stainless steel and titanium respectively (p = 0.64; 4-week period), and 62.5% and 50.0% for stainless steel and titanium respectively (p = 0.09; 12-week period). No significant differences between the devices were found regarding the percent of "bone-to-implant contact" (p = 0.1) or the static and dynamic bone parameters. However, the 5% threshold of "bone-to-implant contact" was obtained after 4 weeks with the stainless steel devices, leading to increased survival rate values. Bone in the vicinity of the miniscrew implants showed evidence of a significant increase in bone trabecular thickness when compared to bone in the control zone (p = 0.05). In our study, it is likely that increased trabecular thickness is a way for low density bone to respond to the stress induced by loading.

  7. In Vivo Evaluation of Immediately Loaded Stainless Steel and Titanium Orthodontic Screws in a Growing Bone

    PubMed Central

    Gritsch, Kerstin; Laroche, Norbert; Bonnet, Jeanne-Marie; Exbrayat, Patrick; Morgon, Laurent; Rabilloud, Muriel; Grosgogeat, Brigitte

    2013-01-01

    The present work intends to evaluate the use of immediate loaded orthodontic screws in a growing model, and to study the specific bone response. Thirty-two screws (half of stainless steel and half of titanium) were inserted in the alveolar bone of 8 growing pigs. The devices were immediately loaded with a 100 g orthodontic force. Two loading periods were assessed: 4 and 12 weeks. Both systems of screws were clinically assessed. Histological observations and histomorphometric analysis evaluated the percent of “bone-to-implant contact” and static and dynamic bone parameters in the vicinity of the devices (test zone) and in a bone area located 1.5 cm posterior to the devices (control zone). Both systems exhibit similar responses for the survival rate; 87.5% and 81.3% for stainless steel and titanium respectively (p = 0.64; 4-week period), and 62.5% and 50.0% for stainless steel and titanium respectively (p = 0.09; 12-week period). No significant differences between the devices were found regarding the percent of “bone-to-implant contact” (p = 0.1) or the static and dynamic bone parameters. However, the 5% threshold of “bone-to-implant contact” was obtained after 4 weeks with the stainless steel devices, leading to increased survival rate values. Bone in the vicinity of the miniscrew implants showed evidence of a significant increase in bone trabecular thickness when compared to bone in the control zone (p = 0.05). In our study, it is likely that increased trabecular thickness is a way for low density bone to respond to the stress induced by loading. PMID:24124540

  8. Breast-feeding after inferior pedicle reduction mammaplasty.

    PubMed

    Brzozowski, D; Niessen, M; Evans, H B; Hurst, L N

    2000-02-01

    The breast-feeding practices of a series of postpartum women, who had undergone prior reduction mammaplasty by means of an inferior pedicle approach, are reported in this retrospective study. Also identified are the factors that influenced the decision to breast-feed postoperatively. From a patient pool of 544 individuals who elected to have reduction mammaplasty between 1984 and 1994 (age range, 15 to 35 years), 334 could be contacted and interviewed by means of telephone by using a standardized questionnaire. Successful breast-feeding was defined as the ability to feed for a duration equal to or greater than 2 weeks. Seventy-eight patients had children after their breast reduction surgery. Fifteen of the 78 patients (19.2 percent) breast-fed exclusively, 8 (10.3 percent) breast-fed with formula supplementation, 14 (17.9 percent) had an unsuccessful breast-feeding attempt, and 41 (52.6 percent) did not attempt breast-feeding. Of the 41 patients not attempting to breast-feed, 9 patients did so as a direct consequence of discouragement by a health care professional. Further reasons for feeding with supplementation, having an unsuccessful attempt, and not attempting to breast-feed are presented. Of the 78 women who had children postoperatively, a total of 27 were discouraged from breast-feeding by medical professionals with only 8 of the 27 (29.6 percent) subsequently attempting, despite this recommendation. In comparison, 26 patients were encouraged to breast-feed; nineteen (73.1 percent) of them did subsequently attempt breast-feeding. This rate is statistically significant by using a chi2 test with 1 df(p = 0.0016). Postpartum breast engorgement and lactation was experienced by 31 of the 41 patients not attempting to breast-feed. Of these 31 patients, 19 believed that they would have been able to breast-feed due to the extent of breast engorgement and lactation experienced. Given the use of an inferior flap mammaplasty technique and patient encouragement, the

  9. Identification of key tissue type for antler regeneration through pedicle periosteum deletion.

    PubMed

    Li, Chunyi; Mackintosh, Colin G; Martin, Shirley K; Clark, Dawn E

    2007-04-01

    Epimorphic regeneration is the "holy grail" of regenerative medicine. Research aimed at investigating the various models of epimorphic regeneration is essential if a fundamental understanding of the factors underpinning this process are to be established. Deer antlers are the only mammalian appendages that are subject to an annual cycle of epimorphic regeneration. In our previous studies, we have reported that histogenesis of antler regeneration relies on cells resident within the pedicle periosteum (PP). The present study elaborates this finding by means of functional studies involving the deletion of PP. Four yearling and four 2-year-old stags were selected for total PP deletion or partial PP deletion experiments. Of the animals in the total PP deletion group, one showed no signs of antler regeneration throughout the antler growth season. Two showed substantial and one showed marginal delays in antler regeneration (at 34, 20 and 7 days, respectively) compared with the corresponding sham-operated sides. Histological investigation revealed that the delayed antlers were derived from regenerated PP. Unexpectedly, the regenerative capacity of the antler from the total periosteum-deleted pedicles depended on antler length at surgery. Of the four deer that had partial PP deletion, two regenerated antlers exclusively from the left-over PP on the pedicle shafts in the absence of participation from the pedicle bone proper. The combined results from the PP deletion experiments convincingly demonstrate that the cells of the PP are responsible for antler regeneration.

  10. Complications and oncologic outcomes of pedicled transverse rectus abdominis myocutaneous flap in breast cancer patients

    PubMed Central

    Somintara, Ongart; Lertsithichai, Panuwat; Kongdan, Youwanush; Supsamutchai, Chairat; Sukpanich, Rupporn

    2016-01-01

    Background There are several techniques for harvesting the pedicled transverse rectus abdominis myocutaneous (TRAM) flap after mastectomy in breast cancer patients. We examined the whole muscle with partial sheath sparing technique and determined factors associated with its complications and oncological outcomes. Methods We retrospectively reviewed the results of 168 TRAM flaps performed between January 2003 and December 2010, focusing on complications and oncologic outcomes. Results Among the 168 pedicled TRAM flap procedures in 158 patients, flap complications occurred in 34%. Most of the flap complications included some degree of fat necrosis. There was no total flap loss. Flap complications were associated with elderly patients and the presence of major donor site complications. Abdominal bulging and hernia occurred in 12% of patients. The bi-pedicled TRAM flap and higher body mass index (BMI) were significant factors associated with increased donor site complications. Seven patients (4%) developed loco-regional recurrence. Within a median follow-up of 27 months, distant metastasis and death occurred in 6% and 4% of patients, respectively. Conclusions The pedicled TRAM flap using the whole muscle with partial sheath sparing technique in the present study is consistent with the results from previous studies in flap complication rates and oncological outcomes. PMID:27563562

  11. An extended approach for the vascular pedicle of the lateral arm free flap.

    PubMed

    Moffett, T R; Madison, S A; Derr, J W; Acland, R D

    1992-02-01

    We present an extension of the surgical approach for harvesting the lateral upper arm free flap by which an additional 6 to 8 cm of pedicle length may be gained. First, the flap is raised by the standard lateral approach. Then, by proceeding proximally and posteriorly, the triceps muscle is split between its lateral and long heads to expose the entire length of the profunda brachii vessels in the spiral groove. A tunnel is developed beneath the lateral head of the triceps, and the flap or its pedicle is delivered through this. We describe the surgical technique and present details of a dissection study on 25 fresh cadaver limbs. The nerve branches to the lateral head of the triceps, which are close to the vessels of the flap, are highly variable in number and location. When unusually short and distally placed, they are at risk of damage, but damage can be avoided if the tunnel is not unduly widened. We present our early clinical experience in 10 consecutive cases using the extended-pedicle lateral arm flap. The free pedicle length in this series ranged from 8 to 13 cm. The maximum flap size was 5 x 19 cm. All cases were successful, although one required reoperation for venous thrombosis. Although postoperative testing of upper arm muscle function showed some weakness and impaired endurance, this was found equally in the surgically disturbed triceps and in the untouched elbow flexors and thus could not be attributed to motor nerve damage to the triceps muscle.

  12. A new Simplified Method of Selective Exposure of Hepatic Pedicles for Controlled Hepatectomies

    PubMed Central

    Karagiulian, S. R.

    1989-01-01

    Our experience of 90 hepatectomies (HE) and examinations of 64 cadaver livers resulted in the elaboration of a simplified technique for the exposure of hepatic pedicles (HP) and the rapid selective ligation without significant normothermal ischemia of the retained parts of the liver. The method comprises 4 consecutive steps: 1) a superficial T-shaped incision of Glisson's capsule at the site of HP projection on the liver's inferior surface, 2) introduction of the surgeon's forefinger into the liver parenchyma, controlled by clamping the hepatoduodenal ligament, the fingertip finding a tubular structure well distinguished by its smooth elastic surface from the friable parenchyma and bending the finger to hook the pedicle, 3) drawing the hooked pedicle downwards through the slit in the capsule and temporarily clamping it, while releasing the hepatoduodenal ligament so as to restore blood supply to the retained parts of the liver, 4) checking for correct ligature position on the HP before its final ligation by matching the actual ischemic area with the intended line of resection and moving the clamp proximally or distally along the exposed pedicle for the release or clamping of lateral branches as necessary. Whereupon resection can be performed by any of the known methods. This method has been used in 8 major HE, allowing to reduce intraoperative blood loss from 2200±247 ml to 1000±225 ml and reducing general liver ischemia from 10 minutes and more to 2–3 minutes. PMID:2487059

  13. Mammaplasty with a single, vertical, superiorly-based pedicle to support the nipple-areola.

    PubMed

    Arufe, H N; Erenfryd, A; Saubidet, M

    1977-08-01

    We present our technique for mammaplasty, using a vertical, single-pedicled, flap with a superior base. The procedure is simple, and it allows final determination of the areola and nipple location after the newly shaped and positioned mound is closed.

  14. Intraoperative computed tomography navigation for transpedicular screw fixation to treat unstable thoracic and lumbar spine fractures: clinical analysis of a case series (CARE-compliant).

    PubMed

    Lee, Ching-Yu; Wu, Meng-Huang; Li, Yen-Yao; Cheng, Chin-Chang; Hsu, Chu-Hsiang; Huang, Tsung-Jen; Hsu, Robert Wen-Wei

    2015-05-01

    Transpedicular screw (TPS) fixation in unstable thoracic and lumbar (TL) spine fractures remains technically difficult because of destroyed anatomical landmarks, unstable gross segments, and discrepancies in anatomic orientation using conventional anatomic landmarks, fluoroscopic guidance, or computed tomography (CT)-based navigation. In this study, we evaluated the safety and accuracy of TPS placement under intraoperative computed tomography (iCT) navigation in managing unstable TL spine fractures.From 2010 to 2013, we retrospectively reviewed the Spine Operation Registry records of patients who underwent posterior instrumented fusion to treat unstable TL spine fractures via the iCT navigation system. An unstable spine fracture was identified as AO/Magerl classification type B or type C.In all, 316 screws in 37 patients with unstable TL spine fractures were evaluated and involved 7 thoracic, 23 thoracolumbar junctional, and 7 lumbar fractures. The accuracy of TPS positioning in the pedicle without breach was 98% (310/316). The average number of iCT scans per patient was 2.1 (range 2-3). The average total radiation dose to patients was 15.8 mSv; the dose per single level exposure was 2.7 mSv. The TPS intraoperative revision rate was 0.6% (2/316) and no neurovascular sequela was observed. TPS fixation using the iCT navigation system obtained a 98% accuracy in stabilizing unstable TL spine fractures. A malplaced TPS could be revised during real-time confirmation of the TPS position, and no secondary operation was required to revise malplaced screws.The iCT navigation system provides accurate and safe management of unstable TL spine fractures. In addition, operating room personnel, including surgeons and nurses, did not need to wear heavy lead aprons as they were not exposed to radiation.

  15. Proximal screws placement in intertrochanteric fractures treated with external fixation: comparison of two different techniques

    PubMed Central

    2011-01-01

    Background To compare two different techniques of proximal pin placement for the treatment of intertrochanteric fractures in elderly patients utilizing the Orthofix Pertrochanteric Fixator. Methods Seventy elderly high-risk patients with an average age of 81 years were treated surgically for intertrochanteric fracture, resulting from a low energy trauma. Patients were randomly divided in two groups regarding to the proximal pin placement technique. In Group A the proximal pins were inserted in a convergent way, while in Group B were inserted in parallel. Results All fractures healed uneventfully after a mean time of 98 days. The fixator was well accepted and no patient had significant difficulties while sitting or lying. The mean VAS score was 5.4 in group A and 5.7 in group B. At 12 months after surgery, in group A the average Harris Hip Score and the Palmer and Parker mobility score was 67 and 5.8, respectively. In group B, the average Harris Hip Score and the Palmer and Parker mobility score was 62 and 5.6, respectively. No statistically significant difference was found regarding the functional outcome. The mean radiographic exposure during pin insertion in Group A and Group B was 15 and 6 seconds, respectively. The difference between the two groups, regarding the radiographic exposure, was found to be significant. Conclusion Proximal screw placement in a parallel way is simple, with significant less radiation exposure and shorter intraoperative duration. In addition, fixation stability is equal compared to convergent pin placement. PMID:21939534

  16. The biomechanical advantages of bilateral lumbo-iliac fixation in unilateral comminuted sacral fractures without sacroiliac screw safe channel

    PubMed Central

    Song, Wenhao; Zhou, Dongsheng; He, Yu

    2016-01-01

    Abstract Background: The aim of this study was to compare the biomechanical characteristics between bilateral and unilateral lumbo-iliac fixation in unilateral comminuted sacral fractures (USF) by finite element analysis. Methods: A 3-dimensional finite element model of unilateral sacral fractures was simulated. Three kinds of implants were instrumented into the model, including the unilateral lumbopelvic fixation (ULF), bilateral lumbopelvic fixation (BLF), and unilateral iliac fixation with bilateral lumbar pedicle screws (UBF). Loads of compression and rotation were distributed to the superior endplate of L3. To evaluate the biomechanical properties, the construct stiffness, the micromotion of the fractures, the stress distribution of implants, and the balance of hemilumbar vertebra are recorded and analyzed. Results: The highest construct stiffness was provided by BLF. In BLF model, the displacement between iliums was only 0.009 mm (compressional) and 0.001 mm (rotational), which was less than that under normal condition (0.02 mm). The maximum von Misses stress of implants appeared on the UBF. By using unilateral fixation, the L4 endured obvious imbalance on bilateral hemivertebra. A marked difference was exposed in BLF and UBF models, and the equilibrium of stress and activity was shown. Conclusion: From the finite element view, the stability of ULF is insufficient to reconstruct the posterior pelvic ring. Furthermore, the unilateral fixation may lead to imbalance of lumbar vertebra and pelvis. On the contrary, the BLF can provide satisfied stability and lumbar balance. PMID:27749563

  17. Economics of water injected air screw compressor systems

    NASA Astrophysics Data System (ADS)

    Venu Madhav, K.; Kovačević, A.

    2015-08-01

    There is a growing need for compressed air free of entrained oil to be used in industry. In many cases it can be supplied by oil flooded screw compressors with multi stage filtration systems, or by oil free screw compressors. However, if water injected screw compressors can be made to operate reliably, they could be more efficient and therefore cheaper to operate. Unfortunately, to date, such machines have proved to be insufficiently reliable and not cost effective. This paper describes an investigation carried out to determine the current limitations of water injected screw compressor systems and how these could be overcome in the 15-315 kW power range and delivery pressures of 6-10 bar. Modern rotor profiles and approach to sealing and cooling allow reasonably inexpensive air end design. The prototype of the water injected screw compressor air system was built and tested for performance and reliability. The water injected compressor system was compared with the oil injected and oil free compressor systems of the equivalent size including the economic analysis based on the lifecycle costs. Based on the obtained results, it was concluded that water injected screw compressor systems could be designed to deliver clean air free of oil contamination with a better user value proposition than the oil injected or oil free screw compressor systems over the considered range of operations.

  18. Fracture mechanisms of retrieved titanium screw thread in dental implant.

    PubMed

    Yokoyama, Ken'ichi; Ichikawa, Tetsuo; Murakami, Hiroki; Miyamoto, Youji; Asaoka, Kenzo

    2002-06-01

    Titanium and its alloy are increasingly attracting attention for use as biomaterials. However, delayed fracture of titanium dental implants has been reported, and factors affecting the acceleration of corrosion and fatigue have to be determined. The fractured surface of a retrieved titanium screw and metallurgical structures of a dental implant system were analyzed. The outer surface of the retrieved screw had a structure different from that of the as-received screw. It was confirmed that a shear crack initiated at the root of the thread and propagated into the inner section of the screw. Gas chromatography revealed that the retrieved screw had absorbed a higher amount of hydrogen than the as-received sample. The grain structure of a titanium screw, immersed in a solution known to induce hydrogen absorption, showed features similar to those of the retrieved screw. It was concluded that titanium in a biological environment absorbs hydrogen and this may be the reason for delayed fracture of a titanium implant.

  19. Optically driven Archimedes micro-screws for micropump applications: multiple blade design

    NASA Astrophysics Data System (ADS)

    Baldeck, Patrice L.; Lin, Chih-Lang; Lin, Yu-Sheng; Lin, Chin-Te; Chung, Tien-Tung; Bouriau, Michel; Vitrant, Guy

    2011-10-01

    We study the rotation of photo-driven Archimedes screw with multiple blades. The micron-sized Archimedes screws are readily made by the two-photon polymerization technique. Free-floating screws that are trapped by optical tweezers align in the laser irradiation direction, and rotate spontaneously. In this study we demonstrate that the rotation speeds of two-blade-screws is twice the rotation speed of one-blade-screw. However, more complex 3-blade-screws rotate slower than 2-blade-screws due to their limited geometry resolution at this micron scale.

  20. Vibration analysis of three-screw pumps under pressure loads and rotor contact forces

    NASA Astrophysics Data System (ADS)

    Li, Wanyou; Lu, Hanfeng; Zhang, Yue; Zhu, Chuan; Lu, Xiqun; Shuai, Zhijun

    2016-01-01

    Two main vibration sources in three-screw pumps, the fluid exciting force and the screw contact force, are studied to provide the basis for vibration control in this paper. A fluid exciting force model and a screw contact model are proposed to calculate these forces. An experimental test is carried out to obtain the vibration response of a three-screw pump. A calibrated finite element model of the three-screw pump is used to verify the vibration response under the fluid exciting force and the screw contact force obtained from the proposed models. The results show that the screw contact force is more dominant than the fluid exciting force.

  1. Gene Insertion Patterns and Sites

    NASA Astrophysics Data System (ADS)

    Vain, Philippe; Thole, Vera

    During the past 25 years, the molecular analysis of transgene insertion patterns and sites in plants has greatly contributed to our understanding of the mechanisms underlying transgene integration, expression, and stability in the nuclear genome. Molecular characterization is also an essential step in the safety assessment of genetically modified crops. This chapter describes the standard experimental procedures used to analyze transgene insertion patterns and loci in cereals and grasses transformed using Agrobacterium tumefaciens or direct transfer of DNA. Methods and protocols enabling the determination of the number and configuration of transgenic loci via a combination of inheritance studies, polymerase chain reaction, and Southern analyses are presented. The complete characterization of transgenic inserts in plants is, however, a holistic process relying on a wide variety of experimental approaches. In this chapter, these additional approaches are not detailed but references to relevant bibliographic records are provided.

  2. Implant Dentistry: Monitoring of Bacteria Along the Transmucosal Passage of the Healing Screw in Absence of Functional Load

    PubMed Central

    MEYNARDI, F.; PASQUALINI, M.E.; ROSSI, F.; DAL CARLO, L.; NARDONE, M.; BAGGI, L.

    2016-01-01

    SUMMARY Purpose To assess the changes in bacterial profile along the transmucosal path of healing screws placed immediately after insertion of two-piece endosseus implants during the 4-month osseointegration phase, in absence of functional load. Materials and methods Two site-specific samples were collected at the peri-implant mucosa of the healing screws of 80 two-piece implants, for a total of 640 samples. Implants placement was performed following a single protocol with flapless technique, in order to limit bacterial contamination of the surgical site. Identical healing screws (5 mm diameter/4 mm height) were used for each of the 80 implants. During the 4 months of the study, the patients followed a standard oral care regimen with no special hygiene maneuvers at the collection sites. Results The present research documents that during the 4-month period prior to application of function load the bacterial profile of all sites exhibited a clear prevalence of cocci at the interface between implant neck and osteoalveolar crest margin. Conclusions A potentially pathogenic bacterial flora developed only along the peri-implant transmucosal path. PMID:28280528

  3. Preliminary Design on Screw Press Model of Palm Oil Extraction Machine

    NASA Astrophysics Data System (ADS)

    Firdaus, Muhammad; Salleh, S. M.; Nawi, I.; Ngali, Z.; Siswanto, W. A.; Yusup, E. M.

    2017-01-01

    The concept of the screw press is to compress the fruit bunch between the main screw and travelling cones to extract the palm oil. Visual inspection, model development and simulation of screw press by using Solidworks 2016 and calculation of design properties were performed to support the investigation. The project aims to analyse different design of screw press which improves in reducing maintenance cost and increasing lifespan. The currently existing of screw press can endure between 500 to 900 hours and requires frequent maintenance. Different configurations have been tried in determination of best design properties in screw press. The results specify that screw press with tapered inner shaft has more total lifespan (hours) compared existing screw press. The selection of the screw press with tapered inner shaft can reduce maintenance cost and increase lifespan of the screw press.

  4. Spline-locking screw fastening strategy

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1992-01-01

    A fastener was developed by NASA Goddard for efficiently performing assembly, maintenance, and equipment replacement functions in space using either robotics or astronaut means. This fastener, the 'Spline Locking Screw' (SLS) would also have significant commercial value in advanced space manufacturing. Commercial (or DoD) products could be manufactured in such a way that their prime subassemblies would be assembled using SLS fasteners. This would permit machines and robots to disconnect and replace these modules/parts with ease, greatly reducing life cycle costs of the products and greatly enhancing the quality, timeliness, and consistency of repairs, upgrades, and remanufacturing. The operation of the basic SLS fastener is detailed, including hardware and test results. Its extension into a comprehensive fastening strategy for NASA use in space is also outlined. Following this, the discussion turns toward potential commercial and government applications and the potential market significance of same.

  5. Spline-Locking Screw Fastening Strategy (SLSFS)

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1991-01-01

    A fastener was developed by NASA Goddard for efficiently performing assembly, maintenance, and equipment replacement functions in space using either robotic or astronaut means. This fastener, the 'Spline Locking Screw' (SLS) would also have significant commercial value in advanced manufacturing. Commercial (or DoD) products could be manufactured in such a way that their prime subassemblies would be assembled using SLS fasteners. This would permit machines and robots to disconnect and replace these modules/parts with ease, greatly reducing life cycle costs of the products and greatly enhancing the quality, timeliness, and consistency of repairs, upgrades, and remanufacturing. The operation of the basic SLS fastener is detailed, including hardware and test results. Its extension into a comprehensive fastening strategy for NASA use in space is also outlined. Following this, the discussion turns toward potential commercial and government applications and the potential market significance of same.

  6. Spline-Screw Payload-Fastening System

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1994-01-01

    Payload handed off securely between robot and vehicle or structure. Spline-screw payload-fastening system includes mating female and male connector mechanisms. Clockwise (or counter-clockwise) rotation of splined male driver on robotic end effector causes connection between robot and payload to tighten (or loosen) and simultaneously causes connection between payload and structure to loosen (or tighten). Includes mechanisms like those described in "Tool-Changing Mechanism for Robot" (GSC-13435) and "Self-Aligning Mechanical and Electrical Coupling" (GSC-13430). Designed for use in outer space, also useful on Earth in applications needed for secure handling and secure mounting of equipment modules during storage, transport, and/or operation. Particularly useful in machine or robotic applications.

  7. Analysis of Material Flow in Screw Extrusion of Aluminum

    SciTech Connect

    Haugen, Bjoern; Oernskar, Magnus; Welo, Torgeir; Wideroee, Fredrik

    2010-06-15

    Screw extrusion of aluminum is a new process for production of aluminum profiles. The commercial potential could be large. Little experimental and numerical work has been done with respect to this process.The material flow of hot aluminum in a screw extruder has been analyzed using finite element formulations for the non-Newtonian Navier-Stokes equations. Aluminum material properties are modeled using the Zener-Holloman material model. Effects of stick-slip conditions are investigated with respect to pressure build up and mixing quality of the extrusion process.The numerical results are compared with physical experiments using an experimental screw extruder.

  8. Noninvasive method for retrieval of broken dental implant abutment screw

    PubMed Central

    Gooty, Jagadish Reddy; Palakuru, Sunil Kumar; Guntakalla, Vikram Reddy; Nera, Mahipal

    2014-01-01

    Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants. PMID:24963261

  9. Posterior Titanium Screw Fixation without Debridement of Infected Tissue for the Treatment of Thoracolumbar Spontaneous Pyogenic Spondylodiscitis

    PubMed Central

    Iacoangeli, Maurizio; Nasi, Davide; Nocchi, Niccolo; Di Rienzo, Alessandro; di Somma, Lucia; Colasanti, Roberto; Vaira, Carmela; Benigni, Roberta; Liverotti, Valentina; Scerrati, Massimo

    2016-01-01

    Study Design Retrospective study. Purpose The aim of our study was to analyze the safety and effectiveness of posterior pedicle screw fixation for treatment of pyogenic spondylodiscitis (PSD) without formal debridement of the infected tissue. Overview of Literature Posterior titanium screw fixation without formal debridement of the infected tissue and anterior column reconstruction for the treatment of PSD is still controversial. Methods From March 2008 to June 2013, 18 patients with PSD underwent posterior titanium fixation with or without decompression, according to their neurological deficit. Postero-lateral fusion with allograft transplantation alone or bone graft with both the allogenic bone and the autologous bone was also performed. The outcome was assessed using the visual analogue scale (VAS) for pain and the Frankel grading system for neurological status. Normalization both of C-reactive protein (CRP) and erythrocyte sedimentation rate was adopted as criterion for discontinuation of antibiotic therapy and infection healing. Segmental instability and fusion were also analyzed. Results At the mean follow-up time of 30.16 months (range, 24–53 months), resolution of spinal infection was achieved in all patients. The mean CRP before surgery was 14.32±7.9 mg/dL, and at the final follow-up, the mean CRP decreased to 0.5±0.33 mg/dL (p <0.005). Follow-up computed tomography scan at 12 months after surgery revealed solid fusion in all patients. The VAS before surgery was 9.16±1.29 and at the final follow-up, it improved to 1.38±2.03, which was statistically significant (p <0.05). Eleven patients out of eighteen (61.11%) with initial neurological impairment had an average improvement of 1.27 grades at the final follow-up documented with the Frankel grading system. Conclusions Posterior screw fixation with titanium instrumentation was safe and effective in terms of stability and restoration of neurological impairment. Fixation also rapidly reduced back pain

  10. [The use of blade plate and dynamic screw plate osteosynthesis].

    PubMed

    Oestern, H J; Gänsslen, A

    2010-02-01

    Osteosynthesis in fracture treatment and in some reconstructive procedures with blade plates or dynamic screw systems was the standard procedure for several decades. In this review, the current options and concepts using blade plate osteosynthesis, stabilization of proximal and distal femur fractures and reconstructive procedures with the dynamic hip screw or the dynamic condylar blade are discussed. On the basis of a literature review, the present indications, results and region-specific complications are reported and discussed.Blade plates are used mainly in the context of reconstructive procedures, as well as in the treatment of pseudoarthroses. The Pauwel procedure in femoral neck non-unions is one of the best known indications. In contrast, the dynamic hip screw is the gold standard for stabilization of femoral neck and most pertrochanteric fractures, whereas the dynamic condylar screw is still an alternative to internal fixators for proximal and distal femoral fracture fixations.

  11. Screw pumps cost effective for heavy crude operations

    SciTech Connect

    Brennan, J.R. )

    1992-12-21

    This paper reports that in petroleum production, screw pumps fulfill the requirements for pumping crude oil with an API gravity of 20[degrees] or less (0.93 sp gr or greater). In many cases, these pumps provide more efficiency than centrifugal and reciprocating pumps. Heavy crude oils typically have viscosities at pumping temperatures in excess of 500 SSU (100 cSt). While screw pumps can handle viscosities ranging from fractional centistokes to millions of centistokes, the normal range for crude oil, from cost and efficiency viewpoints, is above 100 SSU (20 cSt). Bitumens can also be handled by screw pumps. Invented in 1922, rotary, positive-displacement multiple-screw pumps have been used for pumping fuel for burning, lubricating oil, fluid power, process feed, food, chemicals, synthetic-fiber slurries, general transfer, and many other applications.

  12. 21. NBS SUIT LAB. THREE GLOVES, HELMET, AND SCREW DRIVER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. NBS SUIT LAB. THREE GLOVES, HELMET, AND SCREW DRIVER TORQUE WRENCH FOR ASSEMBLY AND REPAIR OF BOTH. - Marshall Space Flight Center, Neutral Buoyancy Simulator Facility, Rideout Road, Huntsville, Madison County, AL

  13. Effects of Multilevel Facetectomy and Screw Density on Postoperative Changes in Spinal Rod Contour in Thoracic Adolescent Idiopathic Scoliosis Surgery

    PubMed Central

    Kokabu, Terufumi; Sudo, Hideki; Abe, Yuichiro; Ito, Manabu; Ito, Yoichi M.; Iwasaki, Norimasa

    2016-01-01

    Flattening of the preimplantation rod contour in the sagittal plane influences thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery. The effects of multilevel facetectomy and screw density on postoperative changes in spinal rod contour have not been documented. This study aimed to evaluate the effects of multilevel facetectomy and screw density on changes in spinal rod contour from before implantation to after surgical correction of thoracic curves in patients with AIS prospectively. The concave and convex rod shapes from patients with thoracic AIS (n = 49) were traced prior to insertion. Postoperative sagittal rod shape was determined by computed tomography. The angle of intersection of the tangents to the rod end points was measured. Multiple stepwise linear regression analysis was used to identify variables independently predictive of change in rod contour (Δθ). Average Δθ at the concave and convex side were 13.6° ± 7.5° and 4.3° ± 4.8°, respectively. The Δθ at the concave side was significantly greater than that of the convex side (P < 0.0001) and significantly correlated with Risser sign (P = 0.032), the preoperative main thoracic Cobb angle (P = 0.031), the preoperative TK angle (P = 0.012), and the number of facetectomy levels (P = 0.007). Furthermore, a Δθ at the concave side ≥14° significantly correlated with the postoperative TK angle (P = 0.003), the number of facetectomy levels (P = 0.021), and screw density at the concave side (P = 0.008). Rod deformation at the concave side suggests that corrective forces acting on that side are greater than on the convex side. Multilevel facetectomy and/or screw density at the concave side have positive effects on reducing the rod deformation that can lead to a loss of TK angle postoperatively. PMID:27564683

  14. Screw thread parameter measurement system based on image processing method

    NASA Astrophysics Data System (ADS)

    Rao, Zhimin; Huang, Kanggao; Mao, Jiandong; Zhang, Yaya; Zhang, Fan

    2013-08-01

    In the industrial production, as an important transmission part, the screw thread is applied extensively in many automation equipments. The traditional measurement methods of screw thread parameter, including integrated test methods of multiparameters and the single parameter measurement method, belong to contact measurement method. In practical the contact measurement exists some disadvantages, such as relatively high time cost, introducing easily human error and causing thread damage. In this paper, as a new kind of real-time and non-contact measurement method, a screw thread parameter measurement system based on image processing method is developed to accurately measure the outside diameter, inside diameter, pitch diameter, pitch, thread height and other parameters of screw thread. In the system the industrial camera is employed to acquire the image of screw thread, some image processing methods are used to obtain the image profile of screw thread and a mathematics model is established to compute the parameters. The C++Builder 6.0 is employed as the software development platform to realize the image process and computation of screw thread parameters. For verifying the feasibility of the measurement system, some experiments were carried out and the measurement errors were analyzed. The experiment results show the image measurement system satisfies the measurement requirements and suitable for real-time detection of screw thread parameters mentioned above. Comparing with the traditional methods the system based on image processing method has some advantages, such as, non-contact, easy operation, high measuring accuracy, no work piece damage, fast error analysis and so on. In the industrial production, this measurement system can provide an important reference value for development of similar parameter measurement system.

  15. Far cortical locking screws in distal femur fractures.

    PubMed

    Adams, John D; Tanner, Stephanie L; Jeray, Kyle J

    2015-03-01

    Distal femur fractures routinely heal by secondary bone healing, which relies on interfragmentary motion. Periarticular locking plates are commonly used for fixation in distal femur fractures but are associated with a high nonunion rate, likely due to the stiffness of the constructs. Far cortical locking (FCL) screws are designed to allow micromotion at the near cortex while maintaining purchase in only the far cortex. Although clinical data are limited, these screws have been shown in biomechanical studies to provide excellent interfragmentary motion, and animal models have shown increased callus formation compared with traditional locking screws. The purpose of this study was to examine the clinical effects that FCL screws have on healing in distal femur fractures treated with locked constructs. In this retrospective case series, 15 patients with a distal femur fracture treated with MotionLoc screws (Zimmer, Warsaw, Indiana) were analyzed. Serial radiographs were evaluated for callus presence and time to union. All fractures were either 33-A3 or 33-C2 according to the AO classification system, and 5 (33%) were open. Bone loss was recorded in 2 patients. There were no nonunions, and average time to union was 24 weeks. There were no implant failures, and all 5 open fractures, including the 2 with bone loss, healed without intervention. There was 1 reoperation due to painful hardware. Although this is a small case series, these results are promising. Far cortical locking screws may provide the answer to the high nonunion rate associated with distal femur fractures treated with traditional locked constructs.

  16. Backflow in twin-screw-type multiphase pump

    SciTech Connect

    Egashira, Kazuyuki; Shoda, Shinji; Tochikawa, Tetsuro; Furukawa, Akinori

    1998-02-01

    The performance of a twin-screw-type multiphase pump was investigated from the viewpoints of backflow in a gap along the twin-screw shafts and of scaleup parameters. Although both the backflow and the scaleup parameters have been recognized as important factors in developing multiphase pumps, they have not yet been clarified. The twin-screw pump was equipped with pressure sensors, set in the multiphase-test facility, and experimented with under various conditions to clarify the relationship between backflow rates and factors such as differential pressure, gas-void fractions (GVF`s), and the rotation speed of the shaft. A physical model was proposed with the empirical relationship of pressure distribution along the screw, and was successfully associated with scaleup parameters, such as the geometrical data of the twin-screw pump. Then it was used successfully to simulate the backflow in twin-screw pumps on relatively broad experimental conditions, judging from the comparison between the model and the experimental data.

  17. Measurement of Tip Apex Distance and Migration of Lag Screws and Novel Blade Screw Used for the Fixation of Intertrochanteric Fractures

    PubMed Central

    Cheng, Cheng-Kung

    2017-01-01

    Fixation with a dynamic hip screw (DHS) is one of the most common methods for stabilizing intertrochanteric fractures, except for unstable and reverse oblique fracture types. However, failure is often observed in osteoporotic patients whereby the lag screw effectively ‘cuts out’ through the weak bone. Novel anti-migration blades have been developed to be used in combination with a lag screw (‘Blade Screw’) to improve the fixation strength in osteoporotic intertrochanteric fractures. An in-vitro biomechanical study and a retrospective clinical study were performed to evaluate lag screw migration when using the novel Blade Screw and a traditional threaded DHS. The biomechanical study showed both the Blade Screw and DHS displayed excessive migration (≥10 mm) before reaching 20,000 loading cycles in mild osteoporotic bone, but overall migration of the Blade Screw was significantly less (p ≤ 0.03). Among the patients implanted with a Blade Screw in the clinical study, there was no significant variation in screw migration at 3-months follow-up (P = 0.12). However, the patient’s implanted with a DHS did display significantly greater migration (P<0.001) than those implanted with the Blade Screw. In conclusion, the Blade Screw stabilizes the bone fragments during dynamic loading so as to provide significantly greater resistance to screw migration in patients with mild osteoporosis. PMID:28085930

  18. Development and Testing of X-Ray Imaging-Enhanced Poly-L-Lactide Bone Screws

    PubMed Central

    Tzeng, Jy-Jiunn; Wu, Ting-Lin; Fong, Tsorng-Harn; Feng, Sheng-Wei; Huang, Haw-Ming

    2015-01-01

    Nanosized iron oxide particles exhibit osteogenic and radiopaque properties. Thus, iron oxide (Fe3O4) nanoparticles were incorporated into a biodegradable polymer (poly-L-lactic acid, PLLA) to fabricate a composite bone screw. This multifunctional, 3D printable bone screw was detectable on X-ray examination. In this study, mechanical tests including three-point bending and ultimate tensile strength were conducted to evaluate the optimal ratio of iron oxide nanoparticles in the PLLA composite. Both injection molding and 3D printing techniques were used to fabricate the PLLA bone screws with and without the iron oxide nanoparticles. The fabricated screws were implanted into the femoral condyles of New Zealand White rabbits. Bone blocks containing the PLLA screws were resected 2 and 4 weeks after surgery. Histologic examination of the surrounding bone and the radiopacity of the iron-oxide-containing PLLA screws were evaluated. Our results indicated that addition of iron oxide nanoparticles at 30% significantly decreased the ultimate tensile stress properties of the PLLA screws. The screws with 20% iron oxide exhibited strong radiopacity compared to the screws fabricated without the iron oxide nanoparticles. Four weeks after surgery, the average bone volume of the iron oxide PLLA composite screws was significantly greater than that of PLLA screws without iron oxide. These findings suggested that biodegradable and X-ray detectable PLLA bone screws can be produced by incorporation of 20% iron oxide nanoparticles. Furthermore, these screws had significantly greater osteogenic capability than the PLLA screws without iron oxide. PMID:26466309

  19. Development and Testing of X-Ray Imaging-Enhanced Poly-L-Lactide Bone Screws.

    PubMed

    Chang, Wei-Jen; Pan, Yu-Hwa; Tzeng, Jy-Jiunn; Wu, Ting-Lin; Fong, Tsorng-Harn; Feng, Sheng-Wei; Huang, Haw-Ming

    2015-01-01

    Nanosized iron oxide particles exhibit osteogenic and radiopaque properties. Thus, iron oxide (Fe3O4) nanoparticles were incorporated into a biodegradable polymer (poly-L-lactic acid, PLLA) to fabricate a composite bone screw. This multifunctional, 3D printable bone screw was detectable on X-ray examination. In this study, mechanical tests including three-point bending and ultimate tensile strength were conducted to evaluate the optimal ratio of iron oxide nanoparticles in the PLLA composite. Both injection molding and 3D printing techniques were used to fabricate the PLLA bone screws with and without the iron oxide nanoparticles. The fabricated screws were implanted into the femoral condyles of New Zealand White rabbits. Bone blocks containing the PLLA screws were resected 2 and 4 weeks after surgery. Histologic examination of the surrounding bone and the radiopacity of the iron-oxide-containing PLLA screws were evaluated. Our results indicated that addition of iron oxide nanoparticles at 30% significantly decreased the ultimate tensile stress properties of the PLLA screws. The screws with 20% iron oxide exhibited strong radiopacity compared to the screws fabricated without the iron oxide nanoparticles. Four weeks after surgery, the average bone volume of the iron oxide PLLA composite screws was significantly greater than that of PLLA screws without iron oxide. These findings suggested that biodegradable and X-ray detectable PLLA bone screws can be produced by incorporation of 20% iron oxide nanoparticles. Furthermore, these screws had significantly greater osteogenic capability than the PLLA screws without iron oxide.

  20. Usefulness of absorbable screws in the Sauvé-Kapandji procedure for rheumatoid wrist reconstruction.

    PubMed

    Nakamura, K; Oda, H; Tanaka, S; Kuga, Y; Yamamoto, M; Nishikawa, T; Juji, T; Shimizu, M

    2002-06-01

    Abstract  In the Sauvé-Kapandji (S-K) procedure for rheumatoid wrist reconstruction, the distal end of the ulna is fixed to the radius with screws. Recently, absorbable screws have increasingly been used instead of metal ones. However, the clinical usefulness of absorbable screws in S-K procedures for rheumatoid patients is still unknown. The purpose of this article is to evaluate the effect of absorbable screws in this procedure by comparing their clinical results with those of metal screws. Poly-l-lactic acid (PLLA) absorbable screws were used in 23 wrists, and metal screws were used in 20 wrists. We evaluated the presence of general or local reactions to PLLA, the stability of the ulnar head, the time to bone union, changes in the shape of the distal ulna, and the presence of bone resorption around the screws. There were no complications with the use of PLLA screws, and their fixation stability was adequate to form sufficient bone union. In five cases in the metal screw group, bone resorption around the screws occurred between 1 and 2 years after surgery. Bone resorption around the PLLA screws was not observed. We conclude that absorbable screws may be more useful than metal screws in the S-K procedure for rheumatoid wrist reconstruction.

  1. Ultrasound guided spine needle insertion

    NASA Astrophysics Data System (ADS)

    Chen, Elvis C. S.; Mousavi, Parvin; Gill, Sean; Fichtinger, Gabor; Abolmaesumi, Purang

    2010-02-01

    An ultrasound (US) guided, CT augmented, spine needle insertion navigational system is introduced. The system consists of an electromagnetic (EM) sensor, an US machine, and a preoperative CT volume of the patient anatomy. Three-dimensional (3D) US volume is reconstructed intraoperatively from a set of two-dimensional (2D) freehand US slices, and is coregistered with the preoperative CT. This allows the preoperative CT volume to be used in the intraoperative clinical coordinate. The spatial relationship between the patient anatomy, surgical tools, and the US transducer are tracked using the EM sensor, and are displayed with respect to the CT volume. The pose of the US transducer is used to interpolate the CT volume, providing the physician with a 2D "x-ray vision" to guide the needle insertion. Many of the system software components are GPU-accelerated, allowing real-time performance of the guidance system in a clinical setting.

  2. Insertion device calculations with mathematica

    SciTech Connect

    Carr, R.; Lidia, S.

    1995-02-01

    The design of accelerator insertion devices such as wigglers and undulators has usually been aided by numerical modeling on digital computers, using code in high level languages like Fortran. In the present era, there are higher level programming environments like IDL{reg_sign}, MatLab{reg_sign}, and Mathematica{reg_sign} in which these calculations may be performed by writing much less code, and in which standard mathematical techniques are very easily used. The authors present a suite of standard insertion device modeling routines in Mathematica to illustrate the new techniques. These routines include a simple way to generate magnetic fields using blocks of CSEM materials, trajectory solutions from the Lorentz force equations for given magnetic fields, Bessel function calculations of radiation for wigglers and undulators and general radiation calculations for undulators.

  3. The influence of screw configuration on the pretreatment performance of a continuous twin screw-driven reactor (CTSR).

    PubMed

    Choi, Chang Ho; Um, Byung-Hwan; Oh, Kyeong Keun

    2013-03-01

    A combination of a continuous twin screw-driven reactor (CTSR) and a dilute acid pretreatment was used for the pretreatment of biomass with a high cellulose content and high monomeric xylose hydrolyzate. With the newly modified CTSR screw configuration (Config. 3), the influences of the screw rotational speed (30-60 rpm), of the pretreatment conditions such as acid concentration (1-5%) and reaction temperature (160-175 °C) at the operating condition of biomass feeding rate (1.0 g/min) and acid feeding rate (13.4 mL/min) on the pretreatment performance were investigated. The cellulose content in the pretreated rape straw was 67.1% at the following optimal conditions: barrel temperature of 165 °C, acid concentration of 3.0% (w/v), and screw rotational speed of 30 rpm. According to the three screw configurations, the glucose yields from enzymatic hydrolysis were 70.1%, 72.9%, and 78.7% for screw Configs. 1, 2, and 3, respectively.

  4. Investigation of an 11mm diameter twin screw granulator: Screw element performance and in-line monitoring via image analysis.

    PubMed

    Sayin, Ridade; Martinez-Marcos, Laura; Osorio, Juan G; Cruise, Paul; Jones, Ian; Halbert, Gavin W; Lamprou, Dimitrios A; Litster, James D

    2015-12-30

    As twin screw granulation (TSG) provides one with many screw element options, characterization of each screw element is crucial in optimizing the screw configuration in order to obtain desired granule attributes. In this study, the performance of two different screw elements - distributive feed screws and kneading elements - was studied in an 11 mm TSG at different liquid-to-solid (L/S) ratios. The kneading element configuration was found to break large granules more efficiently, leading to narrower granule size distributions. While pharmaceutical industry shifts toward continuous manufacturing, inline monitoring and process control are gaining importance. Granules from an 11 mm TSG were analysed using the Eyecon™, a real-time high speed direct imaging system, which has been used to capture accurate particle size distribution and particle count. The size parameters and particle count were then assessed in terms of their ability to be a suitable control measure using the Shewhart control charts. d10 and particle count were found to be good indicators of the change in L/S ratio. However, d50 and d90 did not reflect the change, due to their inherent variability even when the process is at steady state.

  5. Inserting Agility in System Development

    DTIC Science & Technology

    2012-07-01

    Agile IT Acquisition, IT Box, Scrum Inserting Agility in System Development Matthew R. Kennedy and Lt Col Dan Ward, USAF With the fast-paced nature...1,700 individuals and 71 countries, found Scrum and eXtreme Programming to be the most widely followed method- ologies (VersionOne, 2007). Other...University http://www.dau.mil 259 Defense ARJ, July 2012, Vol. 19 No. 3 : 249–264 Scrum Scrum is a framework used for project management, which is

  6. Cadaveric Spinal Surgery Simulation: A Comparison of Cadaver Types

    PubMed Central

    Tomlinson, James E.; Yiasemidou, Marina; Watts, Anna L.; Roberts, Dave J. H.; Timothy, Jake

    2015-01-01

    Study Design Single-blinded study. Objective To assess the suitability of three types of cadaver for simulating pedicle screw insertion and establish if there is an ideal. Methods Three types of cadaver—Thiel-embalmed, Crosado-embalmed, and formaldehyde-embalmed—were draped and the spines exposed. Experienced surgeons were asked to place pedicle screws in each cadaver and give written questionnaire feedback using a modified Likert scale. Soft tissue and bony properties were assessed, along with the role of simulation in spinal surgery training. Results The Thiel cadaver rated highest for soft tissue feel and appearance with a median score of 6 for both (range 2 to 7). The Crosado cadaver rated highest for bony feel, with a median score of 6 (range 2 to 7). The formaldehyde cadaver rated lowest for all categories with median scores of 2, 2.5, and 3.5, respectively. All surgeons felt pedicle screw insertion should be learned in a simulated setting using human cadavers. Conclusion Thiel and Crosado cadavers both offered lifelike simulation of pedicle screw insertion, with each having advantages depending on whether the focus is on soft tissue approach or technical aspects of bony screw insertion. Both cadaver types offer the advantage of long life span, unlike fresh frozen tissue, which means cadavers can be used multiple times, thus reducing the costs. PMID:27190738

  7. Posterior arch C-1 screw technique: a cadaveric comparison study.

    PubMed

    Moisi, Marc; Fisahn, Christian; Tkachenko, Lara; Jeyamohan, Shiveindra; Reintjes, Stephen; Grunert, Peter; Norvell, Daniel C; Tubbs, R Shane; Page, Jeni; Newell, David W; Nora, Peter; Oskouian, Rod J; Chapman, Jens

    2017-03-17

    OBJECTIVE Posterior atlantoaxial stabilization and fusion using C-1 lateral mass screw fixation has become commonly used in the treatment of instability and for reconstructive indications since its introduction by Goel and Laheri in 1994 and modification by Harms in 2001. Placement of such lateral mass screws can be challenging because of the proximity to the spinal cord, vertebral artery, an extensive venous plexus, and the C-2 nerve root, which overlies the designated starting point on the posterior center of the lateral mass. An alternative posterior access point starting on the posterior arch of C-1 could provide a C-2 nerve root-sparing starting point for screw placement, with the potential benefit of greater directional control and simpler trajectory. The authors present a cadaveric study comparing an alternative strategy (i.e., a C-1 screw with a posterior arch starting point) to the conventional strategy (i.e., using the lower lateral mass entry site), specifically assessing the safety of screw placement to preserve the C-2 nerve root. METHODS Five US-trained spine fellows instrumented 17 fresh human cadaveric heads using the Goel/Harms C-1 lateral mass (GHLM) technique on the left and the posterior arch lateral mass (PALM) technique on the right, under fluoroscopic guidance. After screw placement, a CT scan was obtained on each specimen to assess for radiographic screw placement accuracy. Four faculty spine surgeons, blinded to the surgeon who instrumented the cadaver, independently graded the quality of screw placement using a modified Upendra classification. RESULTS Of the 17 specimens, the C-2 nerve root was anatomically impinged in 13 (76.5%) of the specimens. The GHLM technique was graded Type 1 or 2, which is considered "acceptable," in 12 specimens (70.6%), and graded Type 3 or 4 ("unacceptable") in 5 specimens (29.4%). In contrast, the PALM technique had 17 (100%) of 17 graded Type 1 or 2 (p = 0.015). There were no vertebral artery injuries found

  8. [Surgical correction of post-vertebroplasty kyphosis by pedicle substraction osteotomy. Regarding three cases].

    PubMed

    Bachour, E; Coloma, P; Freitas, E; Messerer, R; Michel, F; Barrey, C

    2016-12-01

    We report a case of three patients treated with pedicle subtraction osteotomy for post-vertebroplasty kyphosis. These patients were initially treated with a vertebroplasty for vertebral fracture (two cases) and spinal lymphoma (1 case). All of these patients worsened progressively on a clinical and radiographic level with progression of the spinal deformity in the form of kyphosis. The surgery consisted of transpedicular osteotomy instrumented at the level of the vertebra cemented with maximum removal of intra-corporeal cement. One of the three patients required a supplementary anterior approach to achieve good quality bone fusion. In all three cases the post-vertebroplasty kyphosis was able to be reduced by at least 50 % emphasizing the feasibility and relevance of the pedicle subtraction osteotomy in a context of cemented vertebra.

  9. Misdiagnosing Absent Pedicle of Cervical Spine in the Acute Trauma Setting

    PubMed Central

    Rossel, Felipe; Nooh, Anas; Jarzem, Peter

    2015-01-01

    Congenital absence of cervical spine pedicle can be easily misdiagnosed as facet dislocation on plain radiographs especially in the acute trauma setting. Additional imaging, including computed tomography (CT)-scan with careful interpretation is required in order to not misdiagnose cervical posterior arch malformation with subsequent inappropriate management. A 39-year-old patient presented to the emergency unit of our university hospital after being trampled by a cow over her back and head followed by loss of consciousness, retrograde amnesia and neck pain. Her initial cervical CT-scan showed possible C5-C6 dislocation, then, it became clear that her problem was a misdiagnosed congenital cervical abnormality. Patient was treated symptomatically without consequences. The congenital absence of a cervical pedicle is a very unusual condition that is easily misdiagnosed. Diagnosis can be accurately confirmed with a CT-scan of the cervical spine. Symptomatic conservative treatment will result in resolution of the symptoms. PMID:26605026

  10. Conjunctival pedicle flap in management of open globe injury with corneal tissue loss.

    PubMed

    Nawani, Nishant; Vazirani, Jayesh; Ojha, Hindukush; Sangwan, Virender S

    2016-03-14

    Accidental injury with scissors led to an open globe injury with iris prolapse and corneal tissue loss in the right eye of a 15-year-old girl. Attempts to suture the laceration normally, led to persistent aqueous leak, and tight suturing was leading to unacceptable distortion of the corneal contour. In the absence of donor tissue or tissue glue, a bulbar conjunctival pedicle flap was used to augment sutures placed without undue tension, and watertight closure of the globe was achieved. Postoperatively, the flap retracted, and excellent tectonic, cosmetic and refractive outcomes were achieved. A conjunctival pedicle flap can be a useful adjunct in the armamentarium of the corneal surgeon while dealing with open globe injuries with corneal tissue loss.

  11. Implant stability related to insertion torque force and bone density: An in vitro study.

    PubMed

    Tricio, J; van Steenberghe, D; Rosenberg, D; Duchateau, L

    1995-12-01

    Seventy-five implants were installed in 12 fresh ethanol-treated bovine ribs by use of a torque gauge manometer to measure the force needed to screw the implants fully into the bone. Digital radiographs were taken and a density histogram of the bone at the implant/bone interface was obtained. The damping characteristics of the implant/bone interface were assessed by tapping the abutment with the Periotest (PT) device. Abutments of several lengths screwed at 20 N/cm were used to conduct PT measurements and the PT values (PTVs) were related to the insertion torque force, the bone density, and implant and abutment length. The results indicated that high correlations exist between PTVs and insertion torque force (R value -0.74579), and PTVs and bone density (R value -0.83031). There was also a significant difference (p 0.001) among the PTVs of the different abutment lengths used. Implant length did not demonstrate influence on PTVs (p 0.3847).

  12. Could the Topping-Off Technique Be the Preventive Strategy against Adjacent Segment Disease after Pedicle Screw-Based Fusion in Lumbar Degenerative Diseases? A Systematic Review

    PubMed Central

    Chou, Po-Hsin; Lin, Hsi-Hsien; An, Howard S.; Liu, Kang-Ying

    2017-01-01

    The “topping-off” technique is a new concept applying dynamic or less rigid fixation such as hybrid stabilization device (HSD) or interspinous process device (IPD) for the purpose of avoiding adjacent segment disease (ASD) proximal to the fusion construct. A systematic review of the literature was performed on the effect of topping-off techniques to prevent or decrease the occurrence of ASD after lumbar fusion surgery. We searched through major online databases, PubMed and MEDLINE, using key words related to “topping-off” technique. We reviewed the surgical results of “topping-off” techniques with either HSD or IPD, including the incidence of ASD at two proximal adjacent levels (index and supra-adjacent level) as compared to the fusion alone group. The results showed that the fusion alone group had statistically higher incidence of radiographic (52.6%) and symptomatic (11.6%) ASD at the index level as well as higher incidence (8.1%) of revision surgery. Besides, the HSD (10.5%) and fusion groups (24.7%) had statistically higher incidences of radiographic ASD at supra-adjacent level than the IPD (1%). The findings suggest that the “topping-off” technique may potentially decrease the occurrence of ASD at the proximal motion segments. However, higher quality prospective randomized trials are required prior to wide clinical application. PMID:28321409

  13. Helical Screw Expander Evaluation Project. Final report

    SciTech Connect

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing operation on two-phase geothermal fluids. The Project also produced a computer-equipped data system, an instrumentation and control van, and a 1000-kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  14. Reconstruction of the distal humerus and elbow joint using a pedicled scapular flap: case report.

    PubMed

    Nthumba, Peter; George, Susan; Jami, Michael; Nyoro, Partick

    2013-06-01

    Loss of elbow function resulting from major bone loss negatively affects quality of life and leaves limited options for reconstruction and restoration of function. To overcome this disabling problem, we reconstructed the distal humerus of a child in a single stage using a scapular flap based on the angular branch of the thoracodorsal artery as a pedicled flap. We also reconstructed the proximal ulna using an iliac crest bone graft with dermal graft interposition arthroplasty, which enabled the restoration of useful elbow function.

  15. Metabolism in pedicled and free TRAM flaps: a comparison using the microdialysis technique.

    PubMed

    Edsander-Nord, Asa; Röjdmark, Jonas; Wickman, Marie

    2002-02-01

    The most common complication in flap surgery is of a circulatory nature. Impeded blood flow leads to altered metabolism in the tissue. Possible metabolic differences between different zones of the transverse rectus abdominis muscle (TRAM) flap were studied and the metabolism of pedicled and free TRAM flaps was compared intraoperatively and postoperatively. The method used was microdialysis, which is a useful technique for following local metabolic changes continuously in various tissues.Twenty-two patients with a pedicled or free TRAM flap were monitored using the microdialysis technique. Two microdialysis catheters were placed subcutaneously in the flap (zone I and zone II), and a third one was placed subcutaneously in the flank to serve as a control. The flaps were monitored intraoperatively and postoperatively for 3 days with repeated analyses of extracellular glucose, lactate, and glycerol concentrations. An additional analysis of pyruvate was performed in some patients to calculate the lactate-to-pyruvate ratio. This study showed that glucose, lactate, and glycerol change in a characteristic way when complete ischemia (i.e., complete inhibition of the blood circulation) is present. A slower stabilization with prolonged metabolic signs of ischemia, such as lower glucose and higher lactate and glycerol concentrations, was seen in zone II compared with zone I, and more pronounced metabolic signs of ischemia, but with a faster recovery, were detected in the free TRAM flap group than in the pedicled TRAM flap group. The fact that the metabolites returned to normal earlier in free flaps than in pedicled flaps may indicate that free TRAM flaps sustain less ischemic damage because of better and more vigorous perfusion.

  16. Management of complications following radiofrequency ablation of a pedicle osteoid osteoma.

    PubMed

    Owen, Joseph W; Bridwell, Keith H; Gilula, Louis A

    2014-06-01

    Radiofrequency ablation (RFA) has become an accepted first-line treatment for osteoid osteomas. Ablation of spinal osteoid osteomas has presented a particular challenge because of their proximity to delicate neural structures. Although many case series have reported multiple successfully treated spinal osteoid osteomas, there are no reports of thermal injury or insufficiency fracture associated with RFA of spinal osteoid osteomas. We report the management of complications that result from treating a spinal osteoid osteoma within a pedicle.

  17. Successfully treated descending necrotizing mediastinitis through thoracotomy using a pedicled muscular serratus anterior flap.

    PubMed

    Haremza, Céline; De Dominicis, Florence; Merlusca, Geoni; Berna, Pascal

    2011-10-01

    Descending necrotizing mediastinitis (DNM) is rare and aggressive. A 68-year-old female with no medical history, was admitted to our institution for cervical cellulitis. After a conventional medical treatment, multiple abscesses of the upper mediastinum appeared on computed tomography (CT) findings. Although two cervicotomies were performed, a new necrotic abscess appeared in the anterior upper and middle mediastinum. An extensive debridement of cellulitis and abscess extended to the pericardium was made by thoracotomy. Middle mediastinum and pericardium were covered and reconstructed by a right pedicled serratus anterior flap. After radical surgery, follow-up was uneventful. Early extensive and complete debridement of cervical and mediastinal collections and irrigation with broad-spectrum intravenous antibiotics is essential. Combined surgery is the best approach in DNM. The use of a pedicled muscular flap helps control the sepsis. In such cases, serratus anterior flap is a flap of choice because it is reliable and always available even in a skinny patient, contrary to omentum. In this life-threatening disease, an early aggressive combined surgery with debridement of all necrotic tissues extended to the pericardium if necessary associated with a pedicled flap is mandatory.

  18. The regenerating antler blastema: the derivative of stem cells resident in a pedicle stump.

    PubMed

    Li, Chunyi; Chu, Wenhui

    2016-01-01

    Antlers of the deer are the only mammalian organs that can fully grow back once lost from their pedicles, hence offer the only opportunity to learn how nature has bestowed mammalian epimorphic regeneration. Investigations have demonstrated that it is the proliferation and differentiation of pedicle periosteal cells (PPCs), but not dedifferentiation of the local differentiated cells, that give rise to the antler blastema. PPCs express key embryonic stem cell markers and can be induced to differentiate into multiple cell lineages, so are termed antler stem cells. Further research has found that PPCs can initiate antler regeneration only when they have interacted with cells of the pedicle skin. Histologically, the process of early antler regeneration resembles that of healing of a mouse leg stump wound. However what sets these two apart is the difference in proliferation potential between the PPCs and the periosteal cells of the long bone. We believe that if we can impart a greater proliferation potential to the long bone periosteal cells, we might be able to achieve the dream of regenerating limbs in mammals.

  19. 77 FR 42318 - Orthopaedic and Rehabilitation Devices Panel of the Medical Devices Advisory Committee; Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-18

    ... discuss and make recommendations regarding the classification of posterior cervical screws, including pedicle and lateral mass screws. Cervical pedicle and lateral mass screws are components of rigid..., failed previous fusion, tumor, infection, and inflammatory disorders in the cervical spine. FDA...

  20. The best location for proximal locking screw for femur interlocking nailing: A biomechanical study

    PubMed Central

    Karaarslan, Ahmet A; Karakaşli, Ahmet; Aycan, Hakan; Çeçen, Berivan; Yildiz, Didem Venüs; Sesli, Erhan

    2016-01-01

    Background: Proximal locking screw deformation and screw fracture is a frequently seen problem for femur interlocking nailing that affects fracture healing. We realized that there is lack of literature for the right level for the proximal locking screw. We investigated the difference of locking screw bending resistance between the application of screws on different proximal femoral levels. Materials and Methods: We used a total of 80 proximal locking screws for eight groups, 10 screws for each group. Three-point bending tests were performed on four types of screws in two different trochanteric levels (the lesser trochanter and 20 mm proximal). We determined the yield points at three-point bending tests that a permanent deformation started in the locking screws using an axial compression testing machine. Results: The mean yield point value of 5 mm threaded locking screws applied 20 mm proximal of lesser trochanter was 1022 ± 49 (range 986–1057) (mean ± standard deviation, 95% confidence interval). On the other hand, the mean yield point value of the same type of locking screws applied on the lesser trochanteric level was 2089 ± 249 (range 1911–2268). Which means 103% increase of screw resistance between two levels (P = 0.000). In all screw groups, on the lesser trochanter line we determined 98–174% higher than the yield point values of the same type of locking screws in comparison with 20 mm proximal to the lesser trochanter (P = 0.000). Conclusion: According to our findings, there is twice as much difference in locking screw bending resistance between these two application levels. To avoid proximal locking screw deformation, locking screws should be placed in the level of the lesser trochanter in nailing of 1/3 middle and distal femur fractures. PMID:26955183

  1. Field errors in hybrid insertion devices

    SciTech Connect

    Schlueter, R.D.

    1995-02-01

    Hybrid magnet theory as applied to the error analyses used in the design of Advanced Light Source (ALS) insertion devices is reviewed. Sources of field errors in hybrid insertion devices are discussed.

  2. Interfragmentary compression forces of scaphoid screws in a sawbone cylinder model.

    PubMed

    Hausmann, J T; Mayr, W; Unger, E; Benesch, T; Vécsei, V; Gäbler, C

    2007-07-01

    Various screws have been developed to stabilise fractures of the scaphoid. Commonly used are the Herbert, the HBS, the 3-mm AO and the Acutrak screws. Not long ago a new screw, the Twin Fix, was introduced. This is cannulated and similar in shape and appearance to the classical Herbert screw. In our test series we compared the maximum achievable compression forces of the Twin Fix screw with that of three other screws (AO, HBS and Acutrak screws). To avoid the variations of density, stiffness and rigidity in natural bone, a polyurethane sawbone-based test setup was used. The test series included 10 screws of each type. The compression force was measured using a special strain gauge. The mean compression force was significantly higher for the Twin Fix screw (8+/-1N) and the Acutrak screw (7.6+/-0.4/0.6N) in relation to the AO screw (6.8+/-1.0/1.4N) and HBS screw (2+/-1N). We found the Twin Fix and Acutrak screws to be promising in the treatment of scaphoid fractures.

  3. Insert metering plates for gas turbine nozzles

    DOEpatents

    Burdgick, Steven S.; Itzel, Gary; Chopra, Sanjay; Abuaf, Nesim; Correia, Victor H.

    2004-05-11

    The invention comprises a metering plate which is assembled to an impingement insert for use in the nozzle of a gas turbine. The metering plate can have one or more metering holes and is used to balance the cooling flow within the nozzle. A metering plate with multiple holes reduces static pressure variations which result from the cooling airflow through the metering plate. The metering plate can be assembled to the insert before or after the insert is inserted into the nozzle.

  4. Mechanical and biological complication rates of the modified lateral-screw-retained implant prosthesis in the posterior region: an alternative to the conventional Implant prosthetic system

    PubMed Central

    2016-01-01

    PURPOSE The modified lateral-screw-retained implant prosthesis (LSP) is designed to combine the advantages of screw- and cement-retained implant prostheses. This retrospective study evaluated the mechanical and biological complication rates of implant-supported single crowns (ISSCs) inserted with the modified LSP in the posterior region, and determined how these complication rates are affected by clinical factors. MATERIALS AND METHODS Mechanical complications (i.e., lateral screw loosening [LSL], abutment screw loosening, lateral screw fracture, and ceramic fracture) and biological complications (i.e., peri-implant mucositis [PM] and peri-implantitis) were identified from the patients' treatment records, clinical photographs, periapical radiographs, panoramic radiographs, and clinical indices. The correlations between complication rates and the following clinical factors were determined: gender, age, position in the jaw, placement location, functional duration, clinical crown-to-implant length ratio, crown height space, and the use of a submerged or nonsubmerged placement procedure. RESULTS Mechanical and biological complications were present in 25 of 73 ISSCs with the modified LSP. LSL (n=11) and PM (n=11) were the most common complications. The incidence of mechanical complications was significantly related to gender (P=.018). The other clinical factors were not significantly associated with mechanical and biological complication rates. CONCLUSION Within the limitations of this study, the incidence of mechanical and biological complications in the posterior region was similar for both modified LSP and conventional implant prosthetic systems. In addition, the modified LSP is amenable to maintenance care, which facilitates the prevention and treatment of mechanical and biological complications. PMID:27141260

  5. Numerical and experimental study of an Archimedean Screw Generator

    NASA Astrophysics Data System (ADS)

    Dellinger, G.; Garambois, P.-A.; Dufresne, M.; Terfous, A.; Vazquez, J.; Ghenaim, A.

    2016-11-01

    Finding new, safe and renewable energy is becoming more and more of a priority with global warming. One solution that is gaining popularity is the Archimedean Screw Generator (ASG). This kind of hydroelectric plant allows transforming potential energy of a fluid into mechanical energy and is convenient for low-head hydraulic sites. As it is a new and growing technology, there are few references dealing with their design and performance optimization. The present contribution proposes to investigate experimentally and numerically the ASG performances. The experimental study is performed for various flow conditions and a laboratory scale screw device installed at the fluid mechanics laboratory of the INSA of Strasbourg. The first results show that the screw efficiencies are higher than 80% for various hydraulic conditions. In order to study the structure of 3D turbulent flows and energy losses in a screw, the 3D Navier Stokes equations are solved with the k-w SST turbulence model. The exact geometry of the laboratory-scale screw was used in these simulations. Interestingly, the modeled values of efficiency are in fairly good agreement with experimental results while any friction coefficient is involved.

  6. Numerical simulation of a twin screw expander for performance prediction

    NASA Astrophysics Data System (ADS)

    Papes, Iva; Degroote, Joris; Vierendeels, Jan

    2015-08-01

    With the increasing use of twin screw expanders in waste heat recovery applications, the performance prediction of these machines plays an important role. This paper presents a mathematical model for calculating the performance of a twin screw expander. From the mass and energy conservation laws, differential equations are derived which are then solved together with the appropriate Equation of State in the instantaneous control volumes. Different flow processes that occur inside the screw expander such as filling (accompanied by a substantial pressure loss) and leakage flows through the clearances are accounted for in the model. The mathematical model employs all geometrical parameters such as chamber volume, suction and leakage areas. With R245fa as working fluid, the Aungier Redlich-Kwong Equation of State has been used in order to include real gas effects. To calculate the mass flow rates through the leakage paths formed inside the screw expander, flow coefficients are considered as constant and they are derived from 3D Computational Fluid Dynamic calculations at given working conditions and applied to all other working conditions. The outcome of the mathematical model is the P-V indicator diagram which is compared to CFD results of the same twin screw expander. Since CFD calculations require significant computational time, developed mathematical model can be used for the faster performance prediction.

  7. JT/LJT connector insert material evaluation

    SciTech Connect

    Baca, J.R.F.

    1991-10-01

    Different insert (insulator) materials are undergoing evaluation to replace the Fiberite E-3938 BE96 material currently used. Also being evaluated is the reconfiguration of the insert and metal shell-edge geometries for the purpose of reducing the alleged interference principally responsible for insert damage.

  8. Effects of lag screw design and lubrication on sliding in trochanteric nails.

    PubMed

    Kummer, Frederick J

    2010-01-01

    This study compared the sliding characteristics of three lag screw designs used with trochanteric nails and determined the effects of lubrication on sliding. They were tested by an established method to measure initiation and ease of lag screw sliding. These tests were then repeated with calf serum lubrication. There were significant differences (p < 0.05) between the loads required to initiate lag screw sliding that appeared to be related to design. Screw sliding was similar for all three designs; however, the presence of lag screw locking slots affected sliding in that region. Lubrication did not affect either parameter. Lag screw design aspects, such as diameter and, particularly, surface finish, affect sliding. Due to the small contact area between the lag screw and nail creating high interface stresses, lubrication had no effect on lag screw sliding.

  9. Optically driven Archimedes micro-screws for micropump application.

    PubMed

    Lin, Chih-Lang; Vitrant, Guy; Bouriau, Michel; Casalegno, Roger; Baldeck, Patrice L

    2011-04-25

    Archimedes micro-screws have been fabricated by three-dimensional two-photon polymerization using a Nd:YAG Q-switched microchip laser at 532nm. Due to their small sizes they can be easily manipulated, and made to rotate using low power optical tweezers. Rotation rates up to 40 Hz are obtained with a laser power of 200 mW, i.e. 0.2 Hz/mW. A photo-driven micropump action in a microfluidic channel is demonstrated with a non-optimized flow rate of 6 pL/min. The optofluidic properties of such type of Archimedes micro-screws are quantitatively described by the conservation of momentum that occurs when the laser photons are reflected on the helical micro-screw surface.

  10. Study on the performance prediction of screw vacuum pump

    NASA Astrophysics Data System (ADS)

    Ohbayashi, T.; Sawada, T.; Hamaguchi, M.; Miyamura, H.

    2001-01-01

    Pumping characteristics of the screw vacuum pump were investigated. The aim of this study was to establish a method of the performance prediction and a way to design the pump that satisfies specific requirements. The performance was analysed by the balance among geometrical pumping speed, net throughput and leaks. The leaks flow through clearances between a screw rotor and a stator, and clearances between two meshing rotors. These leaks were estimated with the results based on the linearised BGK model and the flows through ideal labyrinthes. Experiments were carried out by rotors of 120 mm diameter, and pumping speed and ultimate pressure were measured. The comparison between the measurements and the predicted values shows that the present method predicts the performance of the screw pump with a sufficient accuracy for practical applications.

  11. Mechanical Properties of Nanotextured Titanium Orthopedic Screws for Clinical Applications.

    PubMed

    Descamps, Stephane; Awitor, Komla O; Raspal, Vincent; Johnson, Matthew B; Bokalawela, Roshan S P; Larson, Preston R; Doiron, Curtis F

    2013-06-01

    In this work, we modified the topography of commercial titanium orthopedic screws using electrochemical anodization in a 0.4 wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterized using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and [Formula: see text]. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter. Results showed that the fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations.

  12. Efficiency study of oil cooling of a screw compressor

    SciTech Connect

    Tree, D.R.; McKellar, M.G.

    1989-04-01

    One of the major goals of all compressor manufacturers is to build as efficient a compressor as possible. Over the last several years improvements to the design of screw compressors has made them efficiently competitive with other types of compressors, especially at large loads. The primary purpose of this research is to investigate four different methods of cooling a 250 horsepower compressor and determine their effects on the efficiency of the compressor. Two conventional methods, liquid injection and thermosyphon cooling, and two new methods, V-PLUS and Fresco oil injection, are investigated. The screw compressor used in the tests was a VRS-500 screw compressor made by the Vilter Manufacturing Corporation. 6 figs.

  13. Mild coal gasification screw pyrolyzer development and design

    SciTech Connect

    Camp, D.W.

    1990-08-01

    Our objective is to produce information and design recommendations needed for the development of an efficient continuous process for the mild gasification of caking bituminous coals. We have focused on the development of an externally heated pyrolyzer in which the sticky, reacting coal is conveyed by one or more screws. We have taken a multifaceted approach to forwarding the development of the externally-heated screw pyrolyzer. Small scale process experiments on a 38-mm single screw pyrolyzer have been a major part of our effort. Engineering analyses aimed at producing design and scaleup equations have also been important. Process design recommendations follow from these. We critically review our experimental data and experience, and information from the literature and equipment manufactures for the purpose of making qualitative recommendations for improving practical pyrolyzer design and operation. Benchscale experiments are used to supply needed data and test some preliminary concepts. 6 refs., 4 figs., 1 tab.

  14. Screw-in forces during instrumentation by various file systems

    PubMed Central

    2016-01-01

    Objectives The purpose of this study was to compare the maximum screw-in forces generated during the movement of various Nickel-Titanium (NiTi) file systems. Materials and Methods Forty simulated canals in resin blocks were randomly divided into 4 groups for the following instruments: Mtwo size 25/0.07 (MTW, VDW GmbH), Reciproc R25 (RPR, VDW GmbH), ProTaper Universal F2 (PTU, Dentsply Maillefer), and ProTaper Next X2 (PTN, Dentsply Maillefer, n = 10). All the artificial canals were prepared to obtain a standardized lumen by using ProTaper Universal F1. Screw-in forces were measured using a custom-made experimental device (AEndoS-k, DMJ system) during instrumentation with each NiTi file system using the designated movement. The rotation speed was set at 350 rpm with an automatic 4 mm pecking motion at a speed of 1 mm/sec. The pecking depth was increased by 1 mm for each pecking motion until the file reach the working length. Forces were recorded during file movement, and the maximum force was extracted from the data. Maximum screw-in forces were analyzed by one-way ANOVA and Tukey's post hoc comparison at a significance level of 95%. Results Reciproc and ProTaper Universal files generated the highest maximum screw-in forces among all the instruments while M-two and ProTaper Next showed the lowest (p < 0.05). Conclusions Geometrical differences rather than shaping motion and alloys may affect the screw-in force during canal instrumentation. To reduce screw-in forces, the use of NiTi files with smaller cross-sectional area for higher flexibility is recommended. PMID:27847752

  15. Comparison of effectiveness between cork-screw and peg-screw electrodes for transcranial motor evoked potential monitoring using the finite element method

    PubMed Central

    Tomio, Ryosuke; Akiyama, Takenori; Ohira, Takayuki; Yoshida, Kazunari

    2016-01-01

    Background: Intraoperative monitoring of motor evoked potentials by transcranial electric stimulation is popular in neurosurgery for monitoring motor function preservation. Some authors have reported that the peg-screw electrodes screwed into the skull can more effectively conduct current to the brain compared to subdermal cork-screw electrodes screwed into the skin. The aim of this study was to investigate the influence of electrode design on transcranial motor evoked potential monitoring. We estimated differences in effectiveness between the cork-screw electrode, peg-screw electrode, and cortical electrode to produce electric fields in the brain. Methods: We used the finite element method to visualize electric fields in the brain generated by transcranial electric stimulation using realistic three-dimensional head models developed from T1-weighted images. Surfaces from five layers of the head were separated as accurately as possible. We created the “cork-screws model,” “1 peg-screw model,” “peg-screws model,” and “cortical electrode model”. Results: Electric fields in the brain radially diffused from the brain surface at a maximum just below the electrodes in coronal sections. The coronal sections and surface views of the brain showed higher electric field distributions under the peg-screw compared to the cork-screw. An extremely high electric field was observed under cortical electrodes. Conclusion: Our main finding was that the intensity of electric fields in the brain are higher in the peg-screw model than the cork-screw model. PMID:27920938

  16. Quench Module Insert (QMI) and the Diffusion Module Insert (DMI) Furnace Development

    NASA Technical Reports Server (NTRS)

    Crouch, Myscha; Carswell, William; Farmer, Jeff; Rose, Fred; Tidwell, Paul

    2000-01-01

    This paper presents, in viewgraph form, QMI (Quench Module Insert) and DMI (Diffusion Module Insert) furnace development. The topics include: 1) Furnace Module in Rack; 2) Quench Module Insert; 3) QMI in MSL Core; 4) Diffusion Module Insert; 5) QMI; and 6) QMI Development and Testing.

  17. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Piping joints: Welded and screwed couplings. 154.524... Equipment Cargo and Process Piping Systems § 154.524 Piping joints: Welded and screwed couplings. Pipe... warmer. (d) Screwed couplings are allowed for instrumentation and control piping that meets §...

  18. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Piping joints: Welded and screwed couplings. 154.524... Equipment Cargo and Process Piping Systems § 154.524 Piping joints: Welded and screwed couplings. Pipe... warmer. (d) Screwed couplings are allowed for instrumentation and control piping that meets §...

  19. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Piping joints: Welded and screwed couplings. 154.524... Equipment Cargo and Process Piping Systems § 154.524 Piping joints: Welded and screwed couplings. Pipe... warmer. (d) Screwed couplings are allowed for instrumentation and control piping that meets §...

  20. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Piping joints: Welded and screwed couplings. 154.524... Equipment Cargo and Process Piping Systems § 154.524 Piping joints: Welded and screwed couplings. Pipe... warmer. (d) Screwed couplings are allowed for instrumentation and control piping that meets §...

  1. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Piping joints: Welded and screwed couplings. 154.524... Equipment Cargo and Process Piping Systems § 154.524 Piping joints: Welded and screwed couplings. Pipe... warmer. (d) Screwed couplings are allowed for instrumentation and control piping that meets §...

  2. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone.

    PubMed

    Neumann, Eduardo Aloisio Fleck; Villar, Cristina Cunha; França, Fabiana Mantovani Gomes

    2014-01-01

    Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p < 0.05). In contrast, no statistically significant difference was observed between the fracture resistance of the PEEK and the 30% carbon fiber-reinforced PEEK screws (p> 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.

  3. Real-Time Estimation of Ball-Screw Thermal Elongation Based upon Temperature Distribution of Ball-Screw

    NASA Astrophysics Data System (ADS)

    Kodera, Takehiko; Yokoyama, Kazuhiro; Miyaguchi, Kazuo; Nagai, Yutaka; Suzuki, Takamasa; Masuda, Masami; Yazawa, Takanori

    The optical telemeter system has been developed, which converts the temperature of rotating spindle to the digital data and carries the digital data from LED on the rotating side toward PD on the stationary side by the optical data transmission. Based upon the temperature distribution of hollow ball-screw obtained by the telemeter system, the thermal elongation of the ball-screw is estimated as the one-dimensional thermal elongation. Estimation accuracy, which is the difference between the estimated thermal elongation and the measured thermal elongation, is -3.1∼+3.2µ m for the thermal elongation of 50-60µ m over the length of 935.5mm of the ball-screw.

  4. Systematic extrahepatic Glissonean pedicle isolation for anatomical liver resection based on Laennec's capsule: proposal of a novel comprehensive surgical anatomy of the liver

    PubMed Central

    Sugioka, Atsushi; Kato, Yutaro; Tanahashi, Yoshinao

    2017-01-01

    Abstract Anatomical liver resection with the Glissonean pedicle isolation is widely approved as an essential procedure for safety and curability. Especially, the extrahepatic Glissonean pedicle isolation without parenchymal destruction should be an ideal procedure. However, the surgical technique has not been standardized due to a lack of anatomical understanding. Herein, we proposed a novel comprehensive surgical anatomy of the liver based on Laennec's capsule that would give a theoretical background to the extrahepatic Glissonean pedicle isolation. Laennec's capsule is the proper membrane that covers not only the entire surface of the liver including the bare area but also the intrahepatic parenchyma surrounding the Glissonean pedicles. Consequently, there exists a gap between the Glissonean pedicle and Laennec's capsule that could be reached extrahepatically and allows us to isolate the extrahepatic Glissonean pedicle without parenchymal destruction systematically. For standardization, it is essential to approach the “six gates” indicated by the “four anatomical landmarks”: the Arantius plate, the umbilical plate, the cystic plate and the Glissonean pedicle of the caudate process (G1c). This novel anatomy would contribute to standardize the surgical techniques of the systematic extrahepatic Glissonean pedicle isolation for anatomical liver resection including laparoscopic or robotic liver resection and to bring innovative changes in hepatobiliary surgery for spreading safe and curable liver resection. PMID:28156078

  5. The structure of pedicle and hard antler bone in the European roe deer (Capreolus capreolus): a light microscope and backscattered electron imaging study

    PubMed Central

    Kierdorf, Uwe; Flohr, Stefan; Gomez, Santiago; Landete-Castillejos, Tomas; Kierdorf, Horst

    2013-01-01

    Deer antlers are deciduous bony structures that develop from permanent frontal outgrowths, the pedicles. While growth and bone architecture of antlers have been studied in greater detail, information on pedicle formation and structure is scarce. The present study provides information on the structure of pedicle and hard antler bone in the European roe deer. A pronounced seasonal variation in pedicle architecture was observed, with high porosity around antler casting and a very compact bone structure during the hard antler stage. These observations suggest a corresponding marked variation also in the biomechanical properties of the pedicles. The seasonally alternating extensive resorption and formation processes make the pedicles of older deer heavily remodeled structures. Pedicles increase in thickness by apposition of primary bone that subsequently becomes replaced by secondary osteons. The antler cortex of roe deer is largely composed of a tubular framework of woven bone trabeculae with some remnants of mineralized cartilage, and primary osteons that have filled in the intertrabecular spaces. Secondary osteons are scarce, denoting little remodeling in antlers, which can be related to their short lifespan. The occurrence of cement lines around primary osteons indicates resorption on the trabecular scaffold prior to infilling of the intertrabecular spaces. The outer cortex showed a higher autofluorescence and a more immature structure than the main cortex, suggesting that it was secondarily formed by periosteal activity. Pedicles and antlers constitute a functional entity, and future histological and/or biomechanical studies should therefore consider both components of the cranial appendages. PMID:23961846

  6. Mars Observer Orbit Insertion Briefing

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Steve Wall is the host of this video entitled, "Return to the Red Planet". Live animation of the Mars Observer orbiting Mars is presented. Steve Wall explains the spacecraft insertion maneuver and also explains the purpose for the Mars Observer launch. Live coverage of the Cape Canaveral launch of the Mars Observer is also presented. Suzanne Dodd, Chief of the Mission Planning team describes the burn start and how the spacecraft will be captured by Mars' gravity. Glenn Cunningham, Mars Observer Project Manager, gives background information on the Mars Observer and describes the organizations behind the Mars Observer Spacecraft, such as the Deep Space Network, the Mission Operation Support Office, Science Investigators, the Flight Engineering Office, Operations Office, and the Ground Data System Office. Dr. William Piotrowski, Acting Director, Solar System Exploration Division, NASA, talks about the purpose of the Mars Pathfinder which is to develop the technology and systems for landing small science packages on Mars. Mr. Roger Gibbs, Former Mars Observer Spacecraft Systems Engineer, tells us how the Mars Observer was built and describes the structural elements on the Mars Observer. The 11-month cruise period for the spacecraft is given by Joseph Beerer, Manager of the Engineering office. The thrust for the Mars Orbit Insertion is described by Ronald Klemetson, Technical Manager, Propulsion Subsystem Jet Propulsion Laboratory (JPL). George Chen, Lead Engineer Attitude and Articulation Subsystem Spacecraft Team, explains the importance of the attitude control engines on the Spacecraft. Marvin Traxler, Manager of Tracking and Data Acquisition, describes how searching for a signal from the Mars Observer works. See NONP-NASA-VT-2000081555 for a continuation of this discussion with Marvin Traxler.

  7. Rotational Stability of Scaphoid Osteosyntheses: An In Vitro Comparison of Small Fragment Cannulated Screws to Novel Bone Screw Sets

    PubMed Central

    Erhart, Jochen; Unger, Ewald; Schefzig, Philip; Varga, Peter; Trulson, Inga; Gormasz, Anna; Trulson, Alexander; Reschl, Martin; Hagmann, Michael; Vecsei, Vilmos; Mayr, Winfried

    2016-01-01

    Background The current standard of care for operative repair of scaphoid fractures involves reduction and internal fixation with a single headless compression screw. However, a compression screw in isolation does not necessarily control rotational stability at a fracture or nonunion site. The single screw provides rotational control through friction and bone interdigitation from compression at the fracture site. We hypothesize that osteosyntheses with novel bone screw sets (BSS) equipped with anti-rotational elements provide improved rotational stability. Methods Stability of osteosynthesis under increasing cyclic torsional loading was investigated on osteotomized cadaveric scaphoids. Two novel prototype BSS, oblique type (BSS-obl.) and longitudinal type (BSS-long.) were compared to three conventional screws: Acutrak2®mini, HCS®3.0 and Twinfix®. Biomechanical tests were performed on scaphoids from single donors in paired comparison and analyzed by balanced incomplete random block design. Loading was increased by 50 mNm increments with 1,000 cycles per torque level and repeated until a rotational clearance of 10°. Primary outcome measure was the number of cycles to 10° clearance, secondary outcome measure was the maximum rotational clearance for each torque level. Findings BSS-obl. performed significantly better than Acutrak2®mini and HCS® (p = 0.015, p<0.0001). BSS-long. performed significantly better than HCS® (p = 0.010). No significant difference in performance between BSS-obl. and BSS-long. (p = 0.361), between BSS obl. and Twinfix® (p = 0.50) and BSS long. and Twinfix® (p = 0.667) was detected. Within the torque range up to 200 mNm, four of 21 (19%) BSS-long. and four of 21 (19%) BSS-obl. preparations showed early failure. The same loading led to early failure in four (29%) Twinfix®, seven (50%) Acutrak2®mini and 10 (71%) HCS® of 14 screw samples, respectively. Conclusions For both BSS and to a lesser extent for Twinfix® (as dual-component screw

  8. Preventing postoperative congestion in reverse pedicle digital island flaps when reconstructing composite tissue defects in the fingertip: a patient series.

    PubMed

    Matsuzaki, Hironori; Kouda, Hisao; Yamashita, Haruyoshi

    2012-01-01

    For reconstructing an injured fingertip, a reverse pedicle digital island flap can restore excellent function and appearance. However, postoperative flap congestion may lead to flap necrosis. We tested a method for dissecting the vascular pedicle to prevent congestion and to provide more reliable results. Between August 2002 and December 2010, we reconstructed 14 fingertips in 13 patients (average age, 43 years; range, 24 to 68 years; 9 men). Through a small zigzag incision, the digital artery and a 4-mm-wide subcutaneous venous network were elevated in retrograde fashion to facilitate venous drainage. All flaps healed completely without severe congestion or necrosis. Slight flexion contractures remained in the PIP (mean, 12°) and DIP (mean, 14°) joints. Our procedure is simpler and more reliable than other techniques, such as adding a narrow skin bridge to the pedicle or a venous anastomosis to prevent venous congestion, and it assures the survival of the flap.

  9. Benchtop comparison of a novel dynamic compression screw to a standard cortical screw: compression integrity and gap size over time during simulated resorption.

    PubMed

    Kinmon, Kyle; Garzon, Desiree; Tacktill, Jordan; Vassello, Wayne

    2013-06-01

    Literature reports the incidence of failed isolated foot and ankle fusions as up to 23%. A contributing factor is the natural bone resorption, which occurs resulting in loss of compression and gapping at the fusion site when standard static compression plates and screws are used. However, an innovative dynamic compression screw may provide lasting compression despite resorption. This benchtop study shows that the FxDEVICES spring-loaded dynamic POGO screw maintains more compression and more consistent compression rate during simulated resorption, as compared with a standard compression screw. The novel screw maintained much greater compression strength within the first millimeter of simulated resorption (13.57 vs 4.38 lb) and maintained greater compression strength at the test completion (1.14 vs 0 lb). The novel screw revealed a more consistent resorption rate over the duration of the simulation. Clinically, this may result in more stability and improved fusion rates.

  10. Effect of pedicle fixation combined with 125I seed implantation for metastatic thoracolumbar tumors

    PubMed Central

    Qian, Jiale; Bao, Zhaohua; Zou, Jun; Yang, Huilin

    2016-01-01

    Purpose The aim of this study was to investigate the clinical efficacy of pedicle fixation combined with 125I brachytherapy in treating metastatic thoracolumbar tumors. Patients and methods A retrospective analysis of the clinical data of seven metastatic thoracolumbar tumor patients who received pedicle fixation combined with radioactive 125I seed implantation brachytherapy in our department between January 2009 and December 2013 was performed. The visual analog scale (VAS) for pain and the Karnofsky performance status (KPS) score before the operation and 1, 6, and 12 months after the operation were observed and recorded. The changes in the scores at each time point were compared. Results All the patients underwent a successful operation, without any complications during their hospitalization. All the patients received postoperative follow-up, and the duration of follow-up was 15–50 months, with an average of 32.2 months. One pancreatic cancer patient died of liver failure and hypoproteinemia 28 months post surgery. The VAS scores of patients before the operation and 1, 6, and 12 months after the operation were 7.43±0.98, 2.71±0.49, 3.00±0.82, and 4.29±0.98, respectively; the KPS scores were 52.9±9.5, 84.3±5.3, 75.7±5.3, and 72.9±4.9, respectively. These results suggest that the VAS score at each time point was significantly decreased compared with that before the operation, while the KPS score was significantly increased compared with that before the operation. Both differences had statistical significance (P<0.05). Conclusion As a therapy for advanced malignant tumors with thoracolumbar metastasis, pedicle fixation combined with 125I brachytherapy can effectively relieve short-term pain and improve patient’s quality of life. PMID:27274307

  11. Reconstruction of the Foot and Ankle Using Pedicled or Free Flaps: Perioperative Flap Survival Analysis

    PubMed Central

    Li, Xiucun; Cui, Jianli; Maharjan, Suraj; Lu, Laijin; Gong, Xu

    2016-01-01

    Objective The purpose of this study is to determine the correlation between non-technical risk factors and the perioperative flap survival rate and to evaluate the choice of skin flap for the reconstruction of foot and ankle. Methods This was a clinical retrospective study. Nine variables were identified. The Kaplan-Meier method coupled with a log-rank test and a Cox regression model was used to predict the risk factors that influence the perioperative flap survival rate. The relationship between postoperative wound infection and risk factors was also analyzed using a logistic regression model. Results The overall flap survival rate was 85.42%. The necrosis rates of free flaps and pedicled flaps were 5.26% and 20.69%, respectively. According to the Cox regression model, flap type (hazard ratio [HR] = 2.592; 95% confidence interval [CI] (1.606, 4.184); P < 0.001) and postoperative wound infection (HR = 0.266; 95% CI (0.134, 0.529); P < 0.001) were found to be statistically significant risk factors associated with flap necrosis. Based on the logistic regression model, preoperative wound bed inflammation (odds ratio [OR] = 11.371,95% CI (3.117, 41.478), P < 0.001) was a statistically significant risk factor for postoperative wound infection. Conclusion Flap type and postoperative wound infection were both independent risk factors influencing the flap survival rate in the foot and ankle. However, postoperative wound infection was a risk factor for the pedicled flap but not for the free flap. Microvascular anastomosis is a major cause of free flap necrosis. To reconstruct complex or wide soft tissue defects of the foot or ankle, free flaps are safer and more reliable than pedicled flaps and should thus be the primary choice. PMID:27930679

  12. Bilateral Pedicled Superficial Inferior Epigastric Artery Flap in the Treatment of Hidradenitis Suppurativa

    PubMed Central

    Hoang, Don; Saber, Sepideh; Patel, Ketan; Carey, Joseph

    2016-01-01

    Summary: The authors present a new technique in surgically treating hidradenitis suppurativa (HS), a debilitating skin condition. In HS, surgical treatment is often the best option because of the high recurrence rates despite extensive medical treatment. A commonly successful surgical method is using skin flaps after excision of the affected area. A superficial inferior epigastric artery flap is demonstrated here as a new alternative approach to treating a case of extensive HS of the groin. By using the pedicled superficial inferior epigastric artery flap for groin reconstruction, inguinal HS can be widely excised and reconstructed with minimal donor-site morbidity and a good aesthetic outcome. PMID:27622101

  13. Role of adipose-derived stromal cells in pedicle skin flap survival in experimental animal models.

    PubMed

    Foroglou, Pericles; Karathanasis, Vasileios; Demiri, Efterpi; Koliakos, George; Papadakis, Marios

    2016-03-26

    The use of skin flaps in reconstructive surgery is the first-line surgical treatment for the reconstruction of skin defects and is essentially considered the starting point of plastic surgery. Despite their excellent usability, their application includes general surgical risks or possible complications, the primary and most common is necrosis of the flap. To improve flap survival, researchers have used different methods, including the use of adipose-derived stem cells, with significant positive results. In our research we will report the use of adipose-derived stem cells in pedicle skin flap survival based on current literature on various experimental models in animals.

  14. Role of adipose-derived stromal cells in pedicle skin flap survival in experimental animal models

    PubMed Central

    Foroglou, Pericles; Karathanasis, Vasileios; Demiri, Efterpi; Koliakos, George; Papadakis, Marios

    2016-01-01

    The use of skin flaps in reconstructive surgery is the first-line surgical treatment for the reconstruction of skin defects and is essentially considered the starting point of plastic surgery. Despite their excellent usability, their application includes general surgical risks or possible complications, the primary and most common is necrosis of the flap. To improve flap survival, researchers have used different methods, including the use of adipose-derived stem cells, with significant positive results. In our research we will report the use of adipose-derived stem cells in pedicle skin flap survival based on current literature on various experimental models in animals. PMID:27022440

  15. Free Microsurgical and Pedicled Flaps for Oncological Mandibular Reconstruction: Technical Aspects and Evaluation of Patient Comorbidities

    PubMed Central

    Hassid, Victor J.; Maqusi, Suhair; Culligan, Emmett; Cohen, Mimis N.; Antony, Anuja K.

    2012-01-01

    Oncologic mandibular reconstruction has changed significantly over the years and continues to evolve with the introduction of newer technologies and techniques. Patient demographic, reconstructive, and complication data were obtained from a prospectively maintained clinical database of patients who underwent head and neck reconstruction at our institution. The free fibular flap is now considered the gold standard for mandibular reconstruction. However, in patients with multiple comorbidities, lengthy procedures may be less optimal and pedicled flaps, with specific modifications, can yield reasonable outcomes. Technical aspects and comorbidity profiles are examined in the oncological mandibular reconstruction cohort. PMID:22550602

  16. A Case of Implant Failure in Partial Wrist Fusion Applying Magnesium-Based Headless Bone Screws

    PubMed Central

    Emmerich, Judith

    2016-01-01

    This article presents a case of implant failure resulting in mechanical instability of a scaphotrapezotrapezoideal arthrodesis using magnesium-based headless bone screws. During revision surgery osteolysis surrounding the screws was observed as well as degraded screw threads already in existence at 6 weeks after implantation. The supposed osseous integration attributed to magnesium-based screws could not be reproduced in this particular case. Thus, it can be reasoned that the use of magnesium-based screws for partial wrist arthrodesis cannot be encouraged, at least not in dual use. PMID:27800201

  17. Covering the Screw-Access Holes of Implant Restorations in the Esthetic Zone: A Clinical Report

    PubMed Central

    Saboury, Abolfazl; Gooya, Ali

    2014-01-01

    Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics. PMID:25628703

  18. Use of computational fluid dynamics simulations for design of a pretreatment screw conveyor reactor.

    PubMed

    Berson, R Eric; Hanley, Thomas R

    2005-01-01

    Computational fluid dynamics simulations were employed to compare performance of various designs of a pretreatment screw conveyor reactor. The reactor consisted of a vertical screw used to create cross flow between the upward conveying solids and the downward flow of acid. Simulations were performed with the original screw design and a modified design in which the upper flights of the screw were removed. Results of the simulations show visually that the modified design provided favorable plug flow behavior within the reactor. Pressure drop across the length of the reactor without the upper screws in place was predicted by the simulations to be 5 vs 40 kPa for the original design.

  19. Cellulose and the twofold screw axis: Modeling and experimental arguments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crystallography indicates that molecules in crystalline cellulose either have 2-fold screw-axis (21) symmetry or closely approximate it, leading to short distances between H4 and H1' across the glycosidic linkage. Therefore, modeling studies of cellobiose often show elevated energies for 21 structur...

  20. Stability of two-fold screw axis structures for cellulose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffraction crystallography indicates that most forms of crystalline cellulose have two-fold screw axis symmetry. Even if exact symmetry is absent, the degree of pseudo symmetry is very high. On the other hand, this symmetry leads to short contacts between H4 and H1' across the glycosidic linkage....

  1. Reprint of: Dynamics of discrete screw dislocations on glide directions

    NASA Astrophysics Data System (ADS)

    Alicandro, R.; De Luca, L.; Garroni, A.; Ponsiglione, M.

    2016-12-01

    We consider a simple discrete model for screw dislocations in crystals. Using a variational discrete scheme we study the motion of a configuration of dislocations toward low energy configurations. We deduce an effective fully overdamped dynamics that follows the maximal dissipation criterion introduced in Cermelli and Gurtin (1999) and predicts motion along the glide directions of the crystal.

  2. Some refinements of the theory of the viscous screw pump.

    NASA Technical Reports Server (NTRS)

    Elrod, H. G.

    1972-01-01

    Recently performed analysis for herringbone thrust bearings has been incorporated into the theory of the viscous screw pump for Newtonian fluids. In addition, certain earlier corrections for sidewall and channel curvature effects have been simplified. The result is a single, refined formula for the prediction of the pressure-flow relation for these pumps.

  3. [The effect of polylactide screws on fracture healing].

    PubMed

    Duan, H; Song, Y; Peng, Z; Liu, L; Xiong, C; Zhang, X; Luo, F; Zhu, X; Lin, D

    2000-12-01

    This experiment aimed at investigating the effect of a kind of home-bred poly-DL-lactide screws on fracture healing. An operation was performed so as to make bilateral lateral condylar fractures of the femur in 8 dogs. The left sides were fixed with 2 home-bred PDLLA(Mv = 43 x 10(4)) screws, and the contralateral sides were fixed with 2 metalic screws to be used as controls. The animals were sacrificed at 2, 4, 8, and 12 weeks after surgery. Optic microscopy and SEM photography were done. The results of optic microscopy showed that fibrous callus formed already in both groups by 2 weeks after surgery, and bilateral fractures united uneventfully by 12 weeks. Although the course of fracture healing in experimental group was slower than that in control group, the osteogenesis in experimental group appeared to be normal. The SEM examination demonstrated that collagenous fibers arranged regularly and calcified normally in both groups at 12 weeks. And many square and rhomboid granules produced from the degradation of PDLLA material were found in experimental group at 12 weeks. Therefore, it is suggested that this kind of home-bred PDLLA screws should be applicable to fractures where the tissues are rich in blood supply.

  4. Dynamics of discrete screw dislocations on glide directions

    NASA Astrophysics Data System (ADS)

    Alicandro, R.; De Luca, L.; Garroni, A.; Ponsiglione, M.

    2016-07-01

    We consider a simple discrete model for screw dislocations in crystals. Using a variational discrete scheme we study the motion of a configuration of dislocations toward low energy configurations. We deduce an effective fully overdamped dynamics that follows the maximal dissipation criterion introduced in Cermelli and Gurtin (1999) and predicts motion along the glide directions of the crystal.

  5. INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR VIEW OF JAMES HARRIS CUTTING SCREW THREADS INTO THE INTERIOR OF FITTINGS ON ONE IN A BANK OF TAPPING MACHINES, EACH OPERATED BY THE SAME WORKER SIMULTANEOUSLY BUT TIMED TO REQUIRE WORKER ACTION AT INTERVALS THAT DO NOT INTERFERE WITH THE OTHER MACHINES. - Stockham Pipe & Fittings Company, Tapping Room, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  6. Granulation of increasingly hydrophobic formulations using a twin screw granulator.

    PubMed

    Yu, Shen; Reynolds, Gavin K; Huang, Zhenyu; de Matas, Marcel; Salman, Agba D

    2014-11-20

    The application of twin screw granulation in the pharmaceutical industry has generated increasing interest due to its suitability for continuous processing. However, an understanding of the impact of formulation properties such as hydrophobicity on intermediate and finished product quality has not yet been established. Hence, the current work investigated the granulation behaviour of three formulations containing increasing amounts of hydrophobic components using a Consigma™-1 twin screw granulator. Process conditions including powder feed rate, liquid to solid ratio, granulation liquid composition and screw configuration were also evaluated. The size of the wet granules was measured in order to enable exploration of granulation behaviour in isolation without confounding effects from downstream processes such as drying. The experimental observations indicated that the granulation process was not sensitive to the powder feed rate. The hydrophobicity led to heterogeneous liquid distribution and hence a relatively large proportion of un-wetted particles. Increasing numbers of kneading elements led to high shear and prolonged residence time, which acted to enhance the distribution of liquid and feeding materials. The bimodal size distributions considered to be characteristic of twin screw granulation were primarily ascribed to the breakage of relatively large granules by the kneading elements.

  7. The general theory of blade screws including propellers, fans, helicopter screws, helicoidal pumps, turbo-motors, and different kinds of helicoidal blades

    NASA Technical Reports Server (NTRS)

    De Bothezat, George

    1920-01-01

    Report presents a theory which gives a complete picture and an exact quantitative analysis of the whole phenomenon of the working of blade screws, but also unites in a continuous whole the entire scale of states of work conceivable for a blade screw. Chapter 1 is devoted to the establishment of the system of fundamental equations relating to the blade screw. Chapter 2 contains the general discussion of the 16 states of work which may establish themselves for a blade screw. The existence of the vortex ring state and the whirling phenomenon are established. All the fundamental functions which enter the blade-screw theory are submitted to a general analytical discussion. The general outline of the curve of the specific function is examined. Two limited cases of the work of the screw, the screw with a zero constructive pitch and the screw with an infinite constructive pitch, are pointed out. Chapter 3 is devoted to the study of the propulsive screw or propeller. (author)

  8. Bone Height Changes of the Mandibular Edentulous Ridge in Screw Retained Versus Telescopic Restorations for Completely Edentulous Patients

    PubMed Central

    Helal, Eman; El-Zawahry, Mohamed; Gouda, Ayman; Elkhadem, Amr Hosny; Ibrahim, Samira Ibrahim

    2017-01-01

    AIM: This study was established to evaluate the amount of bone height changes in the posterior mandibular area of edentulous patients receiving screw-retained prostheses versus removable telescopic implant overdentures. MATERIAL AND METHODS: Every patient received four inter-foraminal implants regarding the mandibular arch and four anterior implants for the maxillary arch, computer guided surgical guides were planned for the insertion of the implants accurately with a flapless technique. Panoramic radiographs were made immediately, six months and twelve months after the prostheses` use proportional area and vertical measurements were applied to determine changes in the bone height of the posterior mandibular edentulous area. RESULTS: After twelve months, a statistically non-significant amount of bone resorption was reported for both groups. CONCLUSION: Up to the limitations of this study both treatment options the screw retained and telescopic overdenture can be used for rehabilitation of completely edentulous patients. These cases must be followed for a longer period to have a definite answer regarding their efficiency in the long run. PMID:28293321

  9. Insertion devices at the advanced photon source

    SciTech Connect

    Moog, E.R.

    1996-07-01

    The insertion devices being installed at the Advanced Photon Source cause the stored particle beam to wiggle, emitting x-rays with each wiggle. These x-rays combine to make an intense beam of radiation. Both wiggler and undulator types of insertion devices are being installed; the characteristics of the radiation produced by these two types of insertion devices are discussed, along with the reasons for those characteristics.

  10. Nozzle insert for mixed mode fuel injector

    DOEpatents

    Lawrence, Keith E.

    2006-11-21

    A fuel injector includes a homogenous charge nozzle outlet set and a conventional nozzle outlet set controlled respectively, by first and second needle valve members. The homogeneous charged nozzle outlet set is defined by a nozzle insert that is attached to an injector body, which defines the conventional nozzle outlet set. The nozzle insert is a one piece metallic component with a large diameter segment separated from a small diameter segment by an annular engagement surface. One of the needle valve members is guided on an outer surface of the nozzle insert, and the nozzle insert has an interference fit attachment to the injector body.

  11. Properties of a symmetric RHIC insertion

    SciTech Connect

    Lee, S.Y.

    1991-07-01

    This report evaluates the lattice functions of the symmetric insertion proposed by A.G. Ruggiero for the RHIC insertion. The crossing geometry, Inner and Outer matching sections, and chromatic properties are studied in detail. Some properties of the missing dipole dispersion correction scheme are also discussed. We found that the chromatic properties of the symmetric insertion is not better than the antisymmetric insertion. The problem is that the four family sextupole correction scheme seems not able to improve the chromatic distortion. Analytic understanding of the failure of the four family sextupole correction scheme will be very useful. 9 figs., 1 tab.

  12. Percutaneous Transpedicular Fixation: Technical tips and Pitfalls of Sextant and Pathfinder Systems

    PubMed Central

    Hassan, Ahmed Salah Aldin

    2016-01-01

    Study Design The efficacy of the operative techniques, possible benefits as well as pitfalls and limitations of the techniques are discussed. Potential drawbacks are also detected. Purpose This study aims to report indications, techniques, and our experience with the use of the Sextant and PathFinder percutaneous transpedicular screw fixation systems. Overview of Literature Percutaneous pedicle screw insertion is a novel technique. Successful percutaneous placement of pedicle screws requires surgical skill and experience because of lack of anatomic surface landmarks. Fluoroscopy-guided percutaneous placement of pedicle screws is effective. Many systems are now available. Methods We conducted a prospective operative and postoperative analysis of 40 patients with absolute indication for thoracic or lumbar instability between January 2009 and June 2013. All procedures were performed with the Sextant (group A) and PathFinder (group B) systems under fluoroscopic guidance. Operative techniques are discussed and the results compared. Results Percutaneous transpedicular screw fixation minimizes the morbidity associated with open techniques without compromising the quality of fixation. A total of 190 screws were inserted. There was no additional morbidity. Postoperative computed tomography images and plain X-rays were analyzed. Reduction of visual analog scale scores of back pain was evident. Conclusions Fluoroscopy-guided percutaneous pedicular screws are feasible and can be safely done. Current systems allow multi-segmental fixation with significantly less difficulties. The described techniques have acceptable intra- and postoperative complication rates, and overall sufficient pain control with early mobilization of patients. PMID:26949466

  13. A locked hip screw-intramedullary nail (cephalomedullary nail) for the treatment of fractures of the proximal part of the femur combined with fractures of the femoral shaft.

    PubMed

    Alho, A; Ekeland, A; Grøgaard, B; Dokke, J R

    1996-01-01

    Twenty-seven patients with complex femoral fractures (combined shaft and proximal femoral fractures) were treated with a modified Grosse-Kempf slotted locking nail (cephalomedullary nail), wherein two screws were inserted in the hip. Four types of complex, multifocal femoral fractures were represented in the series. Eleven of the femoral shaft fractures were secondary to a previous, internally fixed, not yet united hip fracture (type I). Ten comminuted peritrochanteric fractures occurred in normal bone (type II). Three similar fractures were pathologic because of metastasis. Two patients had an ipsilateral fracture of the femoral shaft and the trochanteric area (type III), and one of the shaft and the femoral neck (type IV). Locking was made static in 24 cases. Additional cerclage wiring was used in three type II fractures. Five complications were as follows: one cutting out of a screw in the femoral head, two fractures of the nail, one deep venous thrombosis, and one wound hematoma. Reoperations were two salvage operations using a new nail and one evacuation of hematoma. One patient with multiple injuries and four elderly patients died within 2 months. Eighteen patients with fractures in normal bone were followed for a median of 20 (6 to 37) months. All fractures united. Two nails were removed. The end result was excellent in ten patients, good in seven, and fair in one (2-cm shortening and 20-degree external rotation). We conclude that a locked intramedullary construct with locking screws in femoral neck and distal femur controls a complex fracture situation well.

  14. Biomechanical analysis of forces sustained by iliac screws in spinal instrumentation for deformity treatment: preliminary results.

    PubMed

    Perrault, Frederique D; Aubin, Carl-Eric; Wang, Xiaoyu; Schwend, Richard M

    2012-01-01

    Iliac screws used in long instrumentation for deformity treatment are subject to large forces, which may sometimes lead to fixation failures (intra- and postoperatively). The objective of this study was to analyze the biomechanics of iliac screw fixations. The study was based on a patient-specific simulation of a neuromuscular scoliosis case with a long instrumentation to the pelvis. A multi body flexible model was created using a preoperative 3D reconstructed spine and pelvis. The side bending radiographs were used to personalize the mechanical properties. The instrumentation construct was modeled as rigid bodies and flexible beams connected by kinematic joints. Three instrumentation parameters were studied: the connector length, the inter rod connectors and the use of sacral screws. The simulations showed that the forces and torques at the iliac screws were lowered by 9% and 25% respectively by reducing the lateral connector length (from 20 to 10 mm). An inter rod connector did not significantly reduce the iliac screw loads. Sacral screws reduced the functional loads on the iliac screws, but hardware related problems may be shifted onto the sacral screws. Sacral screws in conjunction with inter rod connectors reduced the loads at iliac screws without overloading the sacral screws. The preliminary results showed that the forces at the iliac screws could be lowered through different instrumentation parameters. In the next step of the study, the model validation will be further completed and used to evaluate other instrumentation factors by means of an experimental design framework. The knowledge of loading biomechanics at the iliac screw fixation is important for finding solutions to reduce the risk of failure, such as improving preoperative planning, instrumentation techniques and iliac screw construct design.

  15. Pullout strength of anterior spinal instrumentation: a product comparison of seven screws in calf vertebral bodies

    PubMed Central

    Wahl, Dieter; Wild, Alexander; Krauspe, Rüdiger; Schneider, Erich; Linke, Berend

    2007-01-01

    A lot of new implant devices for spine surgery are coming onto the market, in which vertebral screws play a fundamental role. The new screws developed for surgery of spine deformities have to be compared to established systems. A biomechanical in vitro study was designed to assess the bone–screw interface fixation strength of seven different screws used for correction of scoliosis in spine surgery. The objectives of the current study were twofold: (1) to evaluate the initial strength at the bone–screw interface of newly developed vertebral screws (Universal Spine System II) compared to established systems (product comparison) and (2) to evaluate the influence of screw design, screw diameter, screw length and bone mineral density on pullout strength. Fifty-six calf vertebral bodies were instrumented with seven different screws (USS II anterior 8.0 mm, USS II posterior 6.2 mm, KASS 6.25 mm, USS II anterior 6.2 mm, USS II posterior 5.2 mm, USS 6.0 mm, USS 5.0 mm). Bone mineral density (BMD) was determined by quantitative computed tomography (QCT). Failure in axial pullout was tested using a displacement-controlled universal test machine. USS II anterior 8.0 mm showed higher pullout strength than all other screws. The difference constituted a tendency (P = 0.108) when compared to USS II posterior 6.2 mm (+19%) and was significant in comparison to the other screws (+30 to +55%, P < 0.002). USS II posterior 6.2 mm showed significantly higher pullout strength than USS 5.0 mm (+30%, P = 0.014). The other screws did not differ significantly in pullout strength. Pullout strength correlated significantly with BMD (P = 0.0015) and vertebral body width/screw length (P < 0.001). The newly developed screws for spine surgery (USS II) show higher pullout strength when compared to established systems. Screw design had no significant influence on pullout force in vertebral body screws, but outer diameter of the screw, screw length and BMD are good predictors

  16. Treatment of a Femur Nonunion with Microsurgical Corticoperiosteal Pedicled Flap from the Medial Femoral Condyle

    PubMed Central

    Guzzini, Matteo; Guidi, Marco; Civitenga, Carolina; Ferri, Germano; Ferretti, Andrea

    2016-01-01

    Introduction. The vascularized corticoperiosteal flap is harvested from the medial femoral condyle and it is nourished by the articular branch of the descending genicular artery and the superomedial genicular artery. This flap is usually harvested as a free flap for the reconstruction of bone defects at forearm, distal radius, carpus, hand, and recently at lower limb too. Case Report. A 50-year-old Caucasian man referred to our department for hypertrophic nonunion of the distal femur, refractory to the conservative treatments. The first surgical choice was the revision of the nail and the bone reconstruction with a corticoperiosteal pedicled flap from the medial femoral condyle. We considered union to have occurred 3.5 months after surgery when radiographs showed bridging of at least three of the four bony cortices and clinically the patient was able to walk with full weight bearing without any pain. At the last follow-up (25 months), the patient was completely satisfied with the procedure. Discussion. The corticoperiosteal flap allows a faster healing of fractures with a minimal morbidity at the donor site. We suggest that the corticoperiosteal pedicled flap graft is a reliable and effective treatment for distal femur nonunion. PMID:27064589

  17. Secondary Cleft Lip Reconstruction and the Use of Pedicled, Deepithelialized Scar Tissue

    PubMed Central

    Nadjmi, Nasser; Amadori, Sara; Van de Casteele, Elke

    2016-01-01

    Background: The optimal time to create symmetry in a cleft lip is during primary repair; a secondary effort later is more difficult due to potential scarring and possible tissue deficiency of the repaired cleft lip. A plethora of methods for secondary correction have been described that have the goal of constructing the philtral column, ameliorating bad scar results, and augmenting lip volume, for example. Nevertheless, there is no single procedure that yields completely satisfactory results. In addition, the appropriate timing for secondary surgical corrections of the cleft lip is still under debate. Methods: We present a new technique for secondary lip reconstruction of unilateral and bilateral cleft patients using pedicled, de-epithelialized cleft scar tissue as an autologous graft to obtain sustainable lip volume. Our results were evaluated by physicians and patient-parent satisfaction surveys. Results: The esthetic outcomes of 29 patients were assessed using a patient satisfaction questionnaire and a physician survey based on the preoperative and postoperative clinical images. The success of the procedure was evaluated using a 5-point scale. The total scores of both the physician and patient assessments were high, although no correlation was found between the scores. Conclusions: Cleft lip reconstruction using pedicled, deepithelialized scar tissue leads to excellent physician and patient satisfaction scores; this technique can be executed at any patient age and as a secondary repair for any given primary type of cleft disorder. PMID:27826467

  18. Active Pedicle Epithelial Flap Transposition Combined with Amniotic Membrane Transplantation for Treatment of Nonhealing Corneal Ulcers

    PubMed Central

    Zhang, Ting; Wang, Yuexin; Jia, Yanni; Liu, Dongle; Li, Suxia; Shi, Weiyun

    2016-01-01

    Introduction. The objective was to evaluate the efficacy of active pedicle epithelial flap transposition combined with amniotic membrane transplantation (AMT) in treating nonhealing corneal ulcers. Material and Methods. Eleven patients (11 eyes) with nonhealing corneal ulcer who underwent the combined surgery were included. Postoperatively, ulcer healing time was detected by corneal fluorescein staining. Visual acuity, intraocular pressure, surgical complications, and recurrence were recorded. Corneal status was inspected by the laser scanning confocal microscopy and anterior segment optical coherence tomography (AS-OCT). Results. The primary diseases were herpes simplex keratitis (8 eyes), corneal graft ulcer (2 eyes), and Stevens-Johnson syndrome (1 eye). All epithelial flaps were intact following surgery, without shedding or displacement. Mean ulcer healing time was 10.8 ± 3.1 days, with a healing rate of 91%. Vision significantly improved from 1.70 to 0.82 log MAR (P = 0.001). A significant decrease in inflammatory cell infiltration and corneal stromal edema was revealed 2 months postoperatively by confocal microscopy and AS-OCT. Corneal ulcer recurred in 1 eye. None of the patients developed major complications. Conclusion. Active pedicle epithelial flap transposition combined with AMT is a simple and effective treatment for nonhealing corneal ulcers. PMID:27830086

  19. Free medial thigh perforator-based flaps: new definition of the pedicle vessels and versatile application.

    PubMed

    Koshima, I; Hosoda, M; Inagawa, K; Moriguchi, T; Orita, Y

    1996-11-01

    The medial thigh flap is a perforator-based flap nourished with septocutaneous or muscle perforators originating from the femoral vessels. To date, 8 patients have been repaired with this flap and extended or connected flaps including this flap: 4 patients with lower leg defects and 4 patients with intraoral and neck defects. The advantages of this flap are (1) several pedicle perforators exist for this flap, which makes possible duplicated vascular anastomoses to establish reliable circulation of the transferred flap; (2) the flap can be extended or connected to other neighboring flaps in the anterior thigh, so that extensively wide defects can be closed in one stage; (3) the great saphenous vein can be simultaneously used as a vein graft or for venous drainage for the flap; (4) the anterior branch of the femoral nerve can be used for sensory potential; and (5) there is minimum morbidity of the donor defect and a large dominant vessel for the leg can be preserved. The suitable indications for this flap are defects after removal of skin cancer in the foot or lower leg and wide defects after resection of head and neck cancer, which can be reconstructed with the flap connected to neighboring skin flaps. The disadvantages of this flap are that it has a small, short vascular pedicle and the bulkiness of the flap's fatty tissue often requires thinning.

  20. Multipurpose Transposon-Insertion Libraries in Yeast.

    PubMed

    Kumar, Anuj

    2016-06-01

    Libraries of transposon-insertion alleles constitute powerful and versatile tools for large-scale analysis of yeast gene function. Transposon-insertion libraries are constructed most simply through mutagenesis of a plasmid-based genomic DNA library; modification of the mutagenizing transposon by incorporation of yeast selectable markers, recombination sites, and an epitope tag enables the application of insertion alleles for phenotypic screening and protein localization. In particular, yeast genomic DNA libraries have been mutagenized with modified bacterial transposons carrying the URA3 marker, lox recombination sites, and sequence encoding multiple copies of the hemagglutinin (HA) epitope. Mutagenesis with these transposons has yielded a large resource of insertion alleles affecting nearly 4000 yeast genes in total. Through well-established protocols, these insertion libraries can be introduced into the desired strain backgrounds and the resulting insertional mutants can be screened or systematically analyzed. Relative to alternative methods of UV irradiation or chemical mutagenesis, transposon-insertion alleles can be easily identified by PCR-based approaches or high-throughput sequencing. Transposon-insertion libraries also provide