Are computer numerical control (CNC)-manufactured patient-specific metal templates available for posterior thoracic pedicle screw insertion? Feasibility and accuracy evaluation.

PubMed

Kong, Xiangxue; Tang, Lei; Ye, Qiang; Huang, Wenhua; Li, Jianyi

2017-11-01

Accurate and safe posterior thoracic pedicle insertion (PTPI) remains a challenge. Patient-specific drill templates (PDTs) created by rapid prototyping (RP) can assist in posterior thoracic pedicle insertion, but pose biocompatibility risks. The aims of this study were to develop alternative PDTs with computer numerical control (CNC) and assess their feasibility and accuracy in assisting PTPI. Preoperative CT images of 31 cadaveric thoracic vertebras were obtained and then the optimal pedicle screw trajectories were planned. The PDTs with optimal screw trajectories were randomly assigned to be designed and manufactured by CNC or RP in each vertebra. With the guide of the CNC- or RP-manufactured PDTs, the appropriate screws were inserted into the pedicles. Postoperative CT scans were performed to analyze any deviations at entry point and midpoint of the pedicles. The CNC group was found to be significant manufacture-time-shortening, and cost-decreasing, when compared with the RP group (P < 0.01). The PDTs fitted the vertebral laminates well while all screws were being inserted into the pedicles. There were no significant differences in absolute deviations at entry point and midpoint of the pedicle on either axial or sagittal planes (P > 0.05). The screw positions were grade 0 in 90.3% and grade 1 in 9.7% of the cases in the CNC group and grade 0 in 93.5% and grade 1 in 6.5% of the cases in the RP group (P = 0.641). CNC-manufactured PDTs are viable for assisting in PTPI with good feasibility and accuracy.

Application of multislice spiral CT for guidance of insertion of thoracic spine pedicle screws: an in vitro study.

PubMed

Wang, Juan; Zhou, Yicheng; Hu, Ning; Wang, Renfa

2006-01-01

To investigate the value of the guidance of three dimensional (3-D) reconstruction of multi-slice spiral CT (MSCT) for the placement of pedicle screws, the 3-D anatomical data of the thoracic pedicles were measured by MSCT in two embalmed human cadaveric thoracic pedicles spines (T1-T10) to guide the insertion of pedicle screws. After pulling the screws out, the pathways were filled with contrast media. The PW, PH, TSA and SSA of developed pathways were measured on the CT images and they were also measured on the real objects by caliper and goniometer. Analysis of variance demonstrated that the difference between the CT scans and real objects had no statistical significance (P > 0.05). Moreover, the difference between pedicle axis and developed pathway also had no statistical significance (P > 0.05). The data obtained from 3-D reconstruction of MSCT demonstrated that individualized standards, are not only accurate but also helpful for the successful placement of pedicle screws.

Teriparatide increases the insertional torque of pedicle screws during fusion surgery in patients with postmenopausal osteoporosis.

PubMed

Inoue, Gen; Ueno, Masaki; Nakazawa, Toshiyuki; Imura, Takayuki; Saito, Wataru; Uchida, Kentaro; Ohtori, Seiji; Toyone, Tomoaki; Takahira, Naonobu; Takaso, Masashi

2014-09-01

The object of this study was to examine the efficacy of preoperative teriparatide treatment for increasing the insertional torque of pedicle screws during fusion surgery in postmenopausal women with osteoporosis. Fusion surgery for the thoracic and/or lumbar spine was performed in 29 postmenopausal women with osteoporosis aged 65-82 years (mean 72.2 years). The patients were divided into 2 groups based on whether they were treated with teriparatide (n = 13) or not (n = 16) before the surgery. In the teriparatide-treated group, patients received preoperative teriparatide therapy as either a daily (20 μg/day, n = 7) or a weekly (56.5 μg/week, n = 6) injection for a mean of 61.4 days and a minimum of 31 days. During surgery, the insertional torque was measured in 212 screws inserted from T-7 to L-5 and compared between the 2 groups. The correlation between the insertional torque and the duration of preoperative teriparatide treatment was also investigated. The mean insertional torque value in the teriparatide group was 1.28 ± 0.42 Nm, which was significantly higher than in the control group (1.08 ± 0.52 Nm, p < 0.01). There was no significant difference between the daily and the weekly teriparatide groups with respect to mean insertional torque value (1.34 ± 0.50 Nm and 1.18 ± 0.43 Nm, respectively, p = 0.07). There was negligible correlation between insertional torque and duration of preoperative teriparatide treatment (r(2) = 0.05, p < 0.01). Teriparatide injections beginning at least 1 month prior to surgery were effective in increasing the insertional torque of pedicle screws during surgery in patients with postmenopausal osteoporosis. Preoperative teriparatide treatment might be an option for maximizing the purchase of the pedicle screws to the bone at the time of fusion surgery.

The accuracy and the safety of individualized 3D printing screws insertion templates for cervical screw insertion.

PubMed

Deng, Ting; Jiang, Minghui; Lei, Qing; Cai, Lihong; Chen, Li

2016-12-01

Clinical trial for cervical screw insertion by using individualized 3-dimensional (3D) printing screw insertion templates device. The objective of this study is to evaluate the safety and accuracy of the individualized 3D printing screw insertion template in the cervical spine. Ten patients who underwent posterior cervical fusion surgery with cervical pedicle screws, laminar screws or lateral mass screws between December 2014 and December 2015 were involved in this study. The patients were examined by CT scan before operation. The individualized 3D printing templates were made with photosensitive resin by a 3D printing system to ensure the screw shafts entered the vertebral body without breaking the pedicle or lamina cortex. The templates were sterilized by a plasma sterilizer and used during the operation. The accuracy and the safety of the templates were evaluated by CT scans at the screw insertion levels after operation. The accuracy of this patient-specific template technique was demonstrated. Only one screw axis greatly deviated from the planned track and breached the cortex of the pedicle because the template was split by rough handling and then we inserted the screws under the fluoroscopy. The remaining screws were inserted in the track as preoperative design and the screw axis deviated by less than 2 mm. Vascular or neurologic complications or injuries did not happen. And no infection, broken nails, fracture of bone structure, or screw pullout occurred. This study verified the safety and the accuracy of the individualized 3D printing screw insertion templates in the cervical spine as a kind of intraoperative screw navigation. This individualized 3D printing screw insertion template was user-friendly, moderate cost, and enabled a radiation-free cervical screw insertion.

Influence of Hydroxyapatite Stick on Pedicle Screw Fixation in Degenerative Lumbar Spine: Biomechanical and Radiologic Study.

PubMed

Shin, Sung Joon; Lee, Ji-Ho; Lee, Jae Hyup

2017-07-01

A prospective, within-patient, left-right comparative study. To evaluate the efficacy of hydroxyapatite (HA) stick augmentation method by comparing the insertional torque of the pedicle screw in osteoporotic and nonosteoporotic patients. Unsatisfactory clinical outcomes after spine surgery in osteoporotic patients are related to pedicle screw loosening or pull-outs. HA, as a bone graft extender, has a possibility to enhance the fixation strength at the bone-screw interface. From November 2009 to December 2010, among patients who required bilateral pedicle screw fixation for lumbar spine surgery, 22 patients were enrolled, who recieved unilateral HA stick augmentation and completed intraoperative insertional torque measurement of each pedicle screws. On the basis of preoperative evaluation of bone mineral density, patients with osteoporosis had 2 HA sticks inserted unilaterally, and 1 stick for patients without osteoporosis. Pedicle screw loosening and pull-outs were assessed using 12-month postoperative CT scans and follow-up radiographs. Clinical evaluation was done preoperatively and at 1 year postoperatively, based on Visual Analog Scale score, Oswestry Disability Index, and Short Form-36 Health Survey. Regardless of bone mineral density, the average torque value of all pedicle screws with HA stick insertion (HA stick inserted group) was significantly higher than that of all pedicle screws without HA insertion (control group) (P<0.0001). Same results were seen in the HA stick inserted subgroups and the control subgroups within both of the osteoporosis group (P=0.009) and the nonosteoporosis group (P=0.0004). There was no statistically significant difference of the rate of pedicle screw loosening in between the HA stick inserted group and the control group. Clinical evaluation also showed no statistically significant difference in between patients with loosening and those without. The enhancement of initial pedicle screw fixation strength in osteoporotic patients

Comparison of Expansive Pedicle Screw and Polymethylmethacrylate-Augmented Pedicle Screw in Osteoporotic Sheep Lumbar Vertebrae: Biomechanical and Interfacial Evaluations

PubMed Central

Zhang, Bo; Xie, Qing-yun; Wang, Cai-ru; Liu, Jin-biao; Liao, Dong-fa; Jiang, Kai; Lei, Wei; Pan, Xian-ming

2013-01-01

Background It was reported that expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) could be used to increase screw stability in osteoporosis. However, there are no studies comparing the two kinds of screws in vivo. Thus, we aimed to compare biomechanical and interfacial performances of EPS and PMMA-PS in osteoporotic sheep spine. Methodology/Principal Findings After successful induction of osteoporotic sheep, lumbar vertebrae in each sheep were randomly divided into three groups. The conventional pedicle screw (CPS) was inserted directly into vertebrae in CPS group; PMMA was injected prior to insertion of CPS in PMMA-PS group; and the EPS was inserted in EPS group. Sheep were killed and biomechanical tests, micro-CT analysis and histological observation were performed at both 6 and 12 weeks post-operation. At 6-week and 12-week, screw stabilities in EPS and PMMA-PS groups were significantly higher than that in CPS group, but there were no significant differences between EPS and PMMA-PS groups at two study periods. The screw stability in EPS group at 12-week was significantly higher than that at 6-week. The bone trabeculae around the expanding anterior part of EPS were more and denser than that in CPS group at 6-week and 12-week. PMMA was found without any degradation and absorption forming non-biological “screw-PMMA-bone” interface in PMMA-PS group, however, more and more bone trabeculae surrounded anterior part of EPS improving local bone quality and formed biological “screw-bone” interface. Conclusions/Significance EPS can markedly enhance screw stability with a similar effect to the traditional method of screw augmentation with PMMA in initial surgery in osteoporosis. EPS can form better biological interface between screw and bone than PMMA-PS. In addition, EPS have no risk of thermal injury, leakage and compression caused by PMMA. We propose EPS has a great application potential in augmentation of screw stability

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.

Perforations and angulations of 324 cervical medial cortical pedicle screws: a possible guide to avoid lateral perforations with use of pedicle screws in lower cervical spine.

PubMed

Mahesh, Bijjawara; Upendra, Bidre; Vijay, Sekharappa; Arun, Kumar; Srinivasa, Reddy

2017-03-01

More than half of the perforations reported with usage of cervical pedicle screws (CPS) are lateral perforations, endangering the vertebral artery. The medial cortical pedicle screw (MCPS) technique with partial drilling of the medial cortex shifts the trajectory of pedicle screws medially, decreasing the lateral perforations. To evaluate the decrease in lateral perforations of CPS with use of MCPS technique, in relation to medial angulation. Retrospective analysis and technical report of the MCPS technique and its safety. A total of 58 patients operated on between December 2011 and May 2015 with insertion of pedicle screws from C3 to C7 were included in the study. Axial reconstructed computed tomography (CT) scan images of the inserted screws were evaluated for placement, perforations, and transverse plane angulations using the Surgimap software (Surgimap Spine 1.1.2.271 Intl. 2009 Nemaris LLC). The angulations of screws were analyzed by the type and level of placement through unpaired t test and analysis of variance test. A total of 58 patients operated on between December 2011 and May 2015 with insertion of pedicle screws from C3 to C7 were included in the study. There were 49 males and 9 females. Thirty-seven patients had cervical trauma, 17 had cervical spondylotic myelopathy, two had tumors, and two had ankylosing spondylitis. The average age was 49 years (range 18 to 80 years). The screws were inserted using the MCPS technique. All patients underwent postoperative CT scans with GE Optima CT540 16 slice CT scanner (GE Healthcare Chalfont St. Giles, Buckinghamshire, UK). Axial reconstructed images along the axis of the inserted screws were evaluated for placement and perforations. Further, all the screws were evaluated for transverse plane angulations using the Surgimap software. The angulations of screw were analyzed by the type and level of placement through unpaired t test and analysis of variance test. No funds were received by any of the authors for the

Pull out strength calculator for pedicle screws using a surrogate ensemble approach.

PubMed

Varghese, Vicky; Ramu, Palaniappan; Krishnan, Venkatesh; Saravana Kumar, Gurunathan

2016-12-01

Pedicle screw instrumentation is widely used in the treatment of spinal disorders and deformities. Currently, the surgeon decides the holding power of instrumentation based on the perioperative feeling which is subjective in nature. The objective of the paper is to develop a surrogate model which will predict the pullout strength of pedicle screw based on density, insertion angle, insertion depth and reinsertion. A Taguchi's orthogonal array was used to design an experiment to find the factors effecting pullout strength of pedicle screw. The pullout studies were carried using polyaxial pedicle screw on rigid polyurethane foam block according to American society for testing of materials (ASTM F543). Analysis of variance (ANOVA) and Tukey's honestly significant difference multiple comparison tests were done to find factor effect. Based on the experimental results, surrogate models based on Krigging, polynomial response surface and radial basis function were developed for predicting the pullout strength for different combination of factors. An ensemble of these surrogates based on weighted average surrogate model was also evaluated for prediction. Density, insertion depth, insertion angle and reinsertion have a significant effect (p <0.05) on pullout strength of pedicle screw. Weighted average surrogate performed the best in predicting the pull out strength amongst the surrogate models considered in this study and acted as insurance against bad prediction. A predictive model for pullout strength of pedicle screw was developed using experimental values and surrogate models. This can be used in pre-surgical planning and decision support system for spine surgeon. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Minimally invasive guidewireless, navigated pedicle screw placement: a technical report and case series.

PubMed

Smith, Brandon W; Joseph, Jacob R; Kirsch, Michael; Strasser, Mary Oakley; Smith, Jacob; Park, Paul

2017-08-01

OBJECTIVE Percutaneous pedicle screw insertion (PPSI) is a mainstay of minimally invasive spinal surgery. Traditionally, PPSI is a fluoroscopy-guided, multistep process involving traversing the pedicle with a Jamshidi needle, placement of a Kirschner wire (K-wire), placement of a soft-tissue dilator, pedicle tract tapping, and screw insertion over the K-wire. This study evaluates the accuracy and safety of PPSI with a simplified 2-step process using a navigated awl-tap followed by navigated screw insertion without use of a K-wire or fluoroscopy. METHODS Patients undergoing PPSI utilizing the K-wire-less technique were identified. Data were extracted from the electronic medical record. Complications associated with screw placement were recorded. Postoperative radiographs as well as CT were evaluated for accuracy of pedicle screw placement. RESULTS Thirty-six patients (18 male and 18 female) were included. The patients' mean age was 60.4 years (range 23.8-78.4 years), and their mean body mass index was 28.5 kg/m 2 (range 20.8-40.1 kg/m 2 ). A total of 238 pedicle screws were placed. A mean of 6.6 pedicle screws (range 4-14) were placed over a mean of 2.61 levels (range 1-7). No pedicle breaches were identified on review of postoperative radiographs. In a subgroup analysis of the 25 cases (69%) in which CT scans were performed, 173 screws were assessed; 170 (98.3%) were found to be completely within the pedicle, and 3 (1.7%) demonstrated medial breaches of less than 2 mm (Grade B). There were no complications related to PPSI in this cohort. CONCLUSIONS This streamlined 2-step K-wire-less, navigated PPSI appears safe and accurate and avoids the need for radiation exposure to surgeon and staff.

Effect of screw position on load transfer in lumbar pedicle screws: A non-idealized finite element analysis

PubMed Central

Newcomb, Anna G. U. S.; Baek, Seungwon; Kelly, Brian P.; Crawford, Neil R.

2016-01-01

Angled screw insertion has been advocated to enhance fixation strength during posterior spine fixation. Stresses on a pedicle screw and surrounding vertebral bone with different screw angles were studied by finite element analysis during simulated multidirectional loading. Correlations between screw-specific vertebral geometric parameters and stresses were studied. Angulations in both the sagittal and axial planes affected stresses on the cortical and cancellous bones and the screw. Pedicle screws pointing laterally (vs. straight or medially) in the axial plane during superior screw angulation may be advantageous in terms of reducing the risk of both screw loosening and screw breakage. PMID:27454197

Surgical simulation software for insertion of pedicle screws.

PubMed

Eftekhar, Behzad; Ghodsi, Mohammad; Ketabchi, Ebrahim; Rasaee, Saman

2002-01-01

As the first step toward finding noninvasive alternatives to the traditional methods of surgical training, we have developed a small, stand-alone computer program that simulates insertion of pedicle screws in different spinal vertebrae (T10-L5). We used Delphi 5.0 and DirectX 7.0 extension for Microsoft Windows. This is a stand-alone and portable program. The program can run on most personal computers. It provides the trainee with visual feedback during practice of the technique. At present, it uses predefined three-dimensional images of the vertebrae, but we are attempting to adapt the program to three-dimensional objects based on real computed tomographic scans of the patients. The program can be downloaded at no cost from the web site: www.tums.ac.ir/downloads As a preliminary work, it requires further development, particularly toward better visual, auditory, and even proprioceptive feedback and use of the individual patient's data.

Basic Study for Ultrasound-Based Navigation for Pedicle Screw Insertion Using Transmission and Backscattered Methods

PubMed Central

Chen, Ziqiang; Wu, Bing; Zhai, Xiao; Bai, Yushu; Zhu, Xiaodong; Luo, Beier; Chen, Xiao; Li, Chao; Yang, Mingyuan; Xu, Kailiang; Liu, Chengcheng; Wang, Chuanfeng; Zhao, Yingchuan; Wei, Xianzhao; Chen, Kai; Yang, Wu; Ta, Dean; Li, Ming

2015-01-01

The purpose of this study was to understand the acoustic properties of human vertebral cancellous bone and to study the feasibility of ultrasound-based navigation for posterior pedicle screw fixation in spinal fusion surgery. Fourteen human vertebral specimens were disarticulated from seven un-embalmed cadavers (four males, three females, 73.14 ± 9.87 years, two specimens from each cadaver). Seven specimens were used to measure the transmission, including tests of attenuation and phase velocity, while the other seven specimens were used for backscattered measurements to inspect the depth of penetration and A-Mode signals. Five pairs of unfocused broadband ultrasonic transducers were used for the detection, with center frequencies of 0.5 MHz, 1 MHz, 1.5 MHz, 2.25 MHz, and 3.5 MHz. As a result, good and stable results were documented. With increased frequency, the attenuation increased (P<0.05), stability of the speed of sound improved (P<0.05), and penetration distance decreased (P>0.05). At about 0.6 cm away from the cortical bone, warning signals were easily observed from the backscattered measurements. In conclusion, the ultrasonic system proved to be an effective, moveable, and real-time imaging navigation system. However, how ultrasonic navigation will benefit pedicle screw insertion in spinal surgery needs to be determined. Therefore, ultrasound-guided pedicle screw implantation is theoretically effective and promising. PMID:25861053

Pedicle screw anchorage of carbon fiber-reinforced PEEK screws under cyclic loading.

PubMed

Lindtner, Richard A; Schmid, Rene; Nydegger, Thomas; Konschake, Marko; Schmoelz, Werner

2018-03-01

Pedicle screw loosening is a common and significant complication after posterior spinal instrumentation, particularly in osteoporosis. Radiolucent carbon fiber-reinforced polyetheretherketone (CF/PEEK) pedicle screws have been developed recently to overcome drawbacks of conventional metallic screws, such as metal-induced imaging artifacts and interference with postoperative radiotherapy. Beyond radiolucency, CF/PEEK may also be advantageous over standard titanium in terms of pedicle screw loosening due to its unique material properties. However, screw anchorage and loosening of CF/PEEK pedicle screws have not been evaluated yet. The aim of this biomechanical study therefore was to evaluate whether the use of this alternative nonmetallic pedicle screw material affects screw loosening. The hypotheses tested were that (1) nonmetallic CF/PEEK pedicle screws resist an equal or higher number of load cycles until loosening than standard titanium screws and that (2) PMMA cement augmentation further increases the number of load cycles until loosening of CF/PEEK screws. In the first part of the study, left and right pedicles of ten cadaveric lumbar vertebrae (BMD 70.8 mg/cm 3  ± 14.5) were randomly instrumented with either CF/PEEK or standard titanium pedicle screws. In the second part, left and right pedicles of ten vertebrae (BMD 56.3 mg/cm 3  ± 15.8) were randomly instrumented with either PMMA-augmented or nonaugmented CF/PEEK pedicle screws. Each pedicle screw was subjected to cyclic cranio-caudal loading (initial load ranging from - 50 N to + 50 N) with stepwise increasing compressive loads (5 N every 100 cycles) until loosening or a maximum of 10,000 cycles. Angular screw motion ("screw toggling") within the vertebra was measured with a 3D motion analysis system every 100 cycles and by stress fluoroscopy every 500 cycles. The nonmetallic CF/PEEK pedicle screws resisted a similar number of load cycles until loosening as the contralateral standard

Pedicle screw placement in patients with variant atlas pedicle.

PubMed

Zhang, Qiang-Hua; Li, Hai-Dong; Min, Ji-Kang

2016-08-01

To investigate how the anatomy of variant atlas vertebra impacts on the strategy used to place pedicle screws used to treat atlantoaxial instability. The study enrolled patients with cervical instability who had a posterior arch pedicle height <3.5 mm at the anchor point, a vertebral artery groove height <3.5 mm, or both. Pedicle screws were fitted according to the anatomy of the variant atlas vertebra. Patients were followed-up to evaluate accuracy of the screw placement and maintenance of cervical stability. A total of 28 patients were enrolled. The mean height of the atlas pedicle proximal section was >5.0 mm. For the vertebral artery groove, the height of the lateral region was significantly greater than that of the medial region. Approximately 60% of atlas vertebrae had lateral heights >3.5 mm (34 of 56). The majority of the posterior arch heights were <3.0 mm. There were no perioperative or postoperative complications observed. Pedicle screw placement in the lateral pedicle region is the safest and most reliable strategy to treat variant atlas pedicles. © The Author(s) 2016.

Thoracic, Lumbar, and Sacral Pedicle Screw Placement Using Stryker-Ziehm Virtual Screw Technology and Navigated Stryker Cordless Driver 3: Technical Note.

PubMed

Satarasinghe, Praveen; Hamilton, Kojo D; Tarver, Michael J; Buchanan, Robert J; Koltz, Michael T

2018-04-17

Utilization of pedicle screws (PS) for spine stabilization is common in spinal surgery. With reliance on visual inspection of anatomical landmarks prior to screw placement, the free-hand technique requires a high level of surgeon skill and precision. Three-dimensional (3D), computer-assisted virtual neuronavigation improves the precision of PS placement and minimization steps. Twenty-three patients with degenerative, traumatic, or neoplastic pathologies received treatment via a novel three-step PS technique that utilizes a navigated power driver in combination with virtual screw technology. (1) Following visualization of neuroanatomy using intraoperative CT, a navigated 3-mm match stick drill bit was inserted at an anatomical entry point with a screen projection showing a virtual screw. (2) A Navigated Stryker Cordless Driver with an appropriate tap was used to access the vertebral body through a pedicle with a screen projection again showing a virtual screw. (3) A Navigated Stryker Cordless Driver with an actual screw was used with a screen projection showing the same virtual screw. One hundred and forty-four consecutive screws were inserted using this three-step, navigated driver, virtual screw technique. Only 1 screw needed intraoperative revision after insertion using the three-step, navigated driver, virtual PS technique. This amounts to a 0.69% revision rate. One hundred percent of patients had intraoperative CT reconstructed images taken to confirm hardware placement. Pedicle screw placement utilizing the Stryker-Ziehm neuronavigation virtual screw technology with a three step, navigated power drill technique is safe and effective.

Accuracy analysis of pedicle screw placement in posterior scoliosis surgery: comparison between conventional fluoroscopic and computer-assisted technique.

PubMed

Kotani, Yoshihisa; Abumi, Kuniyoshi; Ito, Manabu; Takahata, Masahiko; Sudo, Hideki; Ohshima, Shigeki; Minami, Akio

2007-06-15

The accuracy of pedicle screw placement was evaluated in posterior scoliosis surgeries with or without the use of computer-assisted surgical techniques. In this retrospective cohort study, the pedicle screw placement accuracy in posterior scoliosis surgery was compared between conventional fluoroscopic and computer-assisted surgical techniques. There has been no study systemically analyzing the perforation pattern and comparative accuracy of pedicle screw placement in posterior scoliosis surgery. The 45 patients who received posterior correction surgeries were divided into 2 groups: Group C, manual control (25 patients); and Group N, navigation surgery (20 patients). The average Cobb angles were 73.7 degrees and 73.1 degrees before surgery in Group C and Group N, respectively. Using CT images, vertebral rotation, pedicle axes as measured to anteroposterior sacral axis and vertebral axis, and insertion angle error were measured. In perforation cases, the angular tendency, insertion point, and length abnormality were evaluated. The perforation was observed in 11% of Group C and 1.8% in Group N. In Group C, medial perforations of left screws were demonstrated in 8 of 9 perforated screws and 55% were distributed either in L1 or T12. The perforation consistently occurred in pedicles in which those axes approached anteroposterior sacral axis within 5 degrees . The average insertion errors were 8.4 degrees and 5.0 degrees in Group C and Group N, respectively, which were significantly different (P < 0.02). The medial perforation in Group C occurred around L1, especially when pedicle axis approached anteroposterior sacral axis. This consistent tendency was considered as the limitation of fluoroscopic screw insertion in which horizontal vertebral image was not visible. The use of surgical navigation system successfully reduced the perforation rate and insertion angle errors, demonstrating the clear advantage in safe and accurate pedicle screw placement of scoliosis surgery.

Mechanical stability of a novel screw design after repeated insertion: can the double-thread screw serve as a back up?

PubMed

Wiendieck, Kurt; Müller, Helge; Buchfelder, Michael; Sommer, Björn

2018-06-01

We investigated mechanical pull-out behavior and tightening torque of a novel dual-core pedicle "6T screw" (6T). The aim of this study was to test if these changes in screw geometry are increasing the strength of the pedicle screw fixation after repeated insertion. Three different types of pedicle screws were inserted in rigid foam blocks. Tightening torque and pull-out strength were measured during two repetitive insertions of a standard 6.5×45-mm conical screw. The third insertion into the pilot hole was performed using either standard 6.5×45-mm or 7.2×45-mm conical screws or the novel 6.5×45-mm (6T) screw. Additionally, we performed a surface analysis to investigate the bone/screw interface. The maximal tightening torque at the third insertion of the novel 6T screw was 194% higher compared to the standard 6.5×45-mm conical screw and 135% higher compared to the standard 7.2×45-mm conical screw. The pull-out strength of the 6T screw showed no significant changes, and surface analysis revealed a compression of the screw-foam interface due to the different internal diameters. The modified geometrical design of the 6T screw seems to have no statistically significant effect on the pull-out strength, although it achieved a higher tightening torque. This might be due to the different pitch angle cutting a new thread into the material and also to the enlarged inner diameter.

The biomechanical consequences of rod reduction on pedicle screws: should it be avoided?

PubMed

Paik, Haines; Kang, Daniel G; Lehman, Ronald A; Gaume, Rachel E; Ambati, Divya V; Dmitriev, Anton E

2013-11-01

POS was observed in both normal (p<.05) and osteoporotic (p<.05) bone. Back out and reinsertion of the screw resulted in no significant difference in mean POS, stiffness, and work energy to failure (p>.05). In circumstances where a rod is not fully seated within the pedicle screw, the use of a rod persuasion device decreases the overall POS and work energy to failure of the screw or results in outright failure. Further rod contouring or correction of pedicle screw depth of insertion may be warranted to allow for appropriate alignment of the longitudinal rods. Published by Elsevier Inc.

Early experience of placing image-guided minimally invasive pedicle screws without K-wires or bone-anchored trackers.

PubMed

Malham, Gregory M; Parker, Rhiannon M

2018-04-01

OBJECTIVE Image guidance for spine surgery has been reported to improve the accuracy of pedicle screw placement and reduce revision rates and radiation exposure. Current navigation and robot-assisted techniques for percutaneous screws rely on bone-anchored trackers and Kirchner wires (K-wires). There is a paucity of published data regarding the placement of image-guided percutaneous screws without K-wires. A new skin-adhesive stereotactic patient tracker (SpineMask) eliminates both an invasive bone-anchored tracker and K-wires for pedicle screw placement. This study reports the authors' early experience with the use of SpineMask for "K-wireless" placement of minimally invasive pedicle screws and makes recommendations for its potential applications in lumbar fusion. METHODS Forty-five consecutive patients (involving 204 screws inserted) underwent K-wireless lumbar pedicle screw fixation with SpineMask and intraoperative neuromonitoring. Screws were inserted by percutaneous stab or Wiltse incisions. If required, decompression with or without interbody fusion was performed using mini-open midline incisions. Multimodality intraoperative neuromonitoring assessing motor and sensory responses with triggered electromyography (tEMG) was performed. Computed tomography scans were obtained 2 days postoperatively to assess screw placement and any cortical breaches. A breach was defined as any violation of a pedicle screw involving the cortical bone of the pedicle. RESULTS Fourteen screws (7%) required intraoperative revision. Screws were removed and repositioned due to a tEMG response < 13 mA, tactile feedback, and 3D fluoroscopic assessment. All screws were revised using the SpineMask with the same screw placement technique. The highest proportion of revisions occurred with Wiltse incisions (4/12, 33%) as this caused the greatest degree of SpineMask deformation, followed by a mini midline incision (3/26, 12%). Percutaneous screws via a single stab incision resulted in the

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

Biomechanical Comparisons of Pull Out Strengths After Pedicle Screw Augmentation with Hydroxyapatite, Calcium Phosphate, or Polymethylmethacrylate in the Cadaveric Spine.

PubMed

Yi, Seong; Rim, Dae-Cheol; Park, Seoung Woo; Murovic, Judith A; Lim, Jesse; Park, Jon

2015-06-01

In vertebrae with low bone mineral densities pull out strength is often poor, thus various substances have been used to fill screw holes before screw placement for corrective spine surgery. We performed biomechanical cadaveric studies to compare nonaugmented pedicle screws versus hydroxyapatite, calcium phosphate, or polymethylmethacrylate augmented pedicle screws for screw tightening torques and pull out strengths in spine procedures requiring bone screw insertion. Seven human cadaveric T10-L1 spines with 28 vertebral bodies were examined by x-ray to exclude bony abnormalities. Dual-energy x-ray absorptiometry scans evaluated bone mineral densities. Twenty of 28 vertebrae underwent ipsilateral fluoroscopic placement of 6-mm holes augmented with hydroxyapatite, calcium phosphate, or polymethylmethacrylate, followed by transpedicular screw placements. Controls were pedicle screw placements in the contralateral hemivertebrae without augmentation. All groups were evaluated for axial pull out strength using a biomechanical loading frame. Mean pedicle screw axial pull out strength compared with controls increased by 12.5% in hydroxyapatite augmented hemivertebrae (P = 0.600) and by 14.9% in calcium phosphate augmented hemivertebrae (P = 0.234), but the increase was not significant for either method. Pull out strength of polymethylmethacrylate versus hydroxyapatite augmented pedicle screws was 60.8% higher (P = 0.028). Hydroxyapatite and calcium phosphate augmentation in osteoporotic vertebrae showed a trend toward increased pedicle screw pull out strength versus controls. Pedicle screw pull out force of polymethylmethacrylate in the insertion stage was higher than that of hydroxyapatite. However, hydroxyapatite is likely a better clinical alternative to polymethylmethacrylate, as hydroxyapatite augmentation, unlike polymethylmethacrylate augmentation, stimulates bone growth and can be revised. Copyright © 2015 Elsevier Inc. All rights reserved.

Proposed alternative revision strategy for broken S1 pedicle screw: radiological study, review of the literature, and case reports.

PubMed

Elgafy, Hossein; Miller, Jacob D; Benedict, Gregory M; Seal, Ryan J; Liu, Jiayong

2013-07-01

There have been many reports outlining differing methods for managing a broken S1 screw. To the authors' best knowledge, the technique used in the present study has not been described previously. It involves insertion of a second pedicle screw without removing the broken screw shaft. Radiological study, literature review, and two case reports of the surgical technique. To report a proposed new surgical technique for management of broken S1 pedicle screws. Computed tomography (CT) scans of 50 patients with a total of 100 S1 pedicles were analyzed. There were 25 male and 25 female patients with an average age of 51 years ranging from 36 to 68 years. The cephalad-caudal length, medial-lateral width, and cross-sectional area of the S1 pedicle were measured and compared with the diameter of a pedicle screw to illustrate the possibility of inserting a second screw in S1 pedicle without removal of the broken screw shaft. Two case reports of the proposed technique are presented. The left and right S1 pedicle cross-sectional area in female measured 456.00 ± 4.00 and 457.00 ± 3.00 mm(2), respectively. The left and right S1 pedicle cross-section area in male measured 638.00 ± 2.00 and 639.00 ± 1.00 mm(2), respectively. There were statistically significant differences when comparing male and female S1 pedicle length, width, and cross-sectional area (p<.05). At 2-year follow-up, the two case reports of the proposed technique showed resolution of low back pain and radicular pain. Plain radiograph and CT scan showed posterolateral fusion mass and hardware in good position with no evidence of screw loosening. The S1 pedicle dimensions measured on CT scan reviewed in the present study showed that it may be anatomically feasible to place a second screw through the S1 pedicle without the removal of the broken screw shaft. This treatment method will reduce the complications associated with other described revision strategies for broken S1 screws. Published by Elsevier Inc.

Insufficient stability of pedicle screws in osteoporotic vertebrae: biomechanical correlation of bone mineral density and pedicle screw fixation strength.

PubMed

Weiser, Lukas; Huber, Gerd; Sellenschloh, Kay; Viezens, Lennart; Püschel, Klaus; Morlock, Michael M; Lehmann, Wolfgang

2017-11-01

Loosening of pedicle screws is one major complication of posterior spinal stabilisation, especially in the patients with osteoporosis. Augmentation of pedicle screws with cement or lengthening of the instrumentation is widely used to improve implant stability in these patients. However, it is still unclear from which value of bone mineral density (BMD) the stability of pedicle screws is insufficient and an additional stabilisation should be performed. The aim of this study was to investigate the correlation of bone mineral density and pedicle screw fatigue strength as well as to define a threshold value for BMD below which an additional stabilisation is recommended. Twenty-one human T12 vertebral bodies were collected from donors between 19 and 96 years of age and the BMD was measured using quantitative computed tomography. Each vertebral body was instrumented with one pedicle screw and mounted in a servo-hydraulic testing machine. Fatigue testing was performed by implementing a cranio-caudal sinusoidal, cyclic (0.5 Hz) load with stepwise increasing peak force. A significant correlation between BMD and cycles to failure (r = 0.862, r 2  = 0.743, p < 0.001) as well as for the linearly related fatigue load was found. Specimens with BMD below 80 mg/cm 3 only reached 45% of the cycles to failure and only 60% of the fatigue load compared to the specimens with adequate bone quality (BMD > 120 mg/cm 3 ). There is a close correlation between BMD and pedicle screw stability. If the BMD of the thoracolumbar spine is less than 80 mg/cm 3 , stability of pedicle screws might be insufficient and an additional stabilisation should be considered.

CLINICAL APPLICATION OF A DRILL GUIDE TEMPLATE FOR PEDICLE SCREW PLACEMENT IN SEVERE SCOLIOSIS.

PubMed

Li, Xin; Zhang, Yaoshen; Zhang, Qiang; Zhao, Changsong; Liu, Kun

2017-01-01

To evaluate the accuracy and the effect of drill guide template for pedicle screw placement in severe scoliosis. Eight patients with rigid scoliosis were enrolled, five males and three females, ranging from nine to 23 years old. A three-dimensional CT scan of the spine was performed and saved as a DICOM file type. The multi-level template was designed by Mimics software and manufactured according to the part of the most severe deformity. The drill template was placed on the corresponding vertebral surface. Pedicle screws were carefully inserted across the trajectory of the template. Postoperatively, the positions of the pedicle screws were evaluated by CT scan and graded for validation. No spinal cord injury or nerve damage occurred. All patients had satisfactory outcomes. The abnormalities and the measures observed during operation were the same as those found in the preoperative period. The position of the pedicle screws was accurate, according to the postoperative X-ray and CT scan. The rate of scoliosis correction was 60%. Compared with controls, surgery time, blood loss and radiation were significantly lower. With the application of multi-level template, the placement of pedicle screws shows high accuracy in scoliosis with shorter surgical time, less blood loss and less radiation exposure. Level of Evidence III, Retrospective Comparative Study.

The accuracy and safety of fluoroscopically guided percutaneous pedicle screws in the lumbosacral junction and the lumbar spine: a review of 880 screws.

PubMed

Chiu, C K; Kwan, M K; Chan, C Y W; Schaefer, C; Hansen-Algenstaedt, N

2015-08-01

We undertook a retrospective study investigating the accuracy and safety of percutaneous pedicle screws placed under fluoroscopic guidance in the lumbosacral junction and lumbar spine. The CT scans of patients were chosen from two centres: European patients from University Medical Center Hamburg-Eppendorf, Germany, and Asian patients from the University of Malaya, Malaysia. Screw perforations were classified into grades 0, 1, 2 and 3. A total of 880 percutaneous pedicle screws from 203 patients were analysed: 614 screws from 144 European patients and 266 screws from 59 Asian patients. The mean age of the patients was 58.8 years (16 to 91) and there were 103 men and 100 women. The total rate of perforation was 9.9% (87 screws) with 7.4% grade 1, 2.0% grade 2 and 0.5% grade 3 perforations. The rate of perforation in Europeans was 10.4% and in Asians was 8.6%, with no significant difference between the two (p = 0.42). The rate of perforation was the highest in S1 (19.4%) followed by L5 (14.9%). The accuracy and safety of percutaneous pedicle screw placement are comparable to those cited in the literature for the open method of pedicle screw placement. Greater caution must be taken during the insertion of L5 and S1 percutaneous pedicle screws owing to their more angulated pedicles, the anatomical variations in their vertebral bodies and the morphology of the spinal canal at this location. ©2015 The British Editorial Society of Bone & Joint Surgery.

Failure analysis of broken pedicle screws on spinal instrumentation.

PubMed

Chen, Chen-Sheng; Chen, Wen-Jer; Cheng, Cheng-Kung; Jao, Shyh-Hua Eric; Chueh, Shan-Chang; Wang, Chang-Chih

2005-07-01

Revised spinal surgery is needed when there is a broken pedicle screw in the patient. This study investigated the pedicle screw breakage by conducting retrieval analyses of broken pedicle screws from 16 patients clinically and by performing stress analyses in the posterolateral fusion computationally using finite element (FE) models. Fracture surface of screws was studied by scanning electron microscope (SEM). The FE model of the posterolateral fusion with the screw showed that screws on the caudal side had larger axial stress than those on the cephalic side, supporting the clinical findings that 75% of the patients had the screw breakage on the caudal side. SEM fractography showed that all broken screws exhibited beach marks or striations on the fractured surface, indicating fatigue failure. Screws of patients with spinal fracture showed fatigue striations and final ductile fracture around the edge. Among the 16 patients who had broken pedicle screws 69% of them achieved bone union in the bone graft, showing that bone union in the bone graft did not warrant the prevention of screw breakage.

Does Navigation Improve Accuracy of Placement of Pedicle Screws in Single-level Lumbar Degenerative Spondylolisthesis?: A Comparison Between Free-hand and Three-dimensional O-Arm Navigation Techniques.

PubMed

Boon Tow, Benjamin Phak; Yue, Wai Mun; Srivastava, Abhishek; Lai, Jenn Ming; Guo, Chang Ming; Wearn Peng, Benedict Chan; Chen, John L T; Yew, Andy K S; Seng, Chusheng; Tan, Seang Beng

2015-10-01

This was a prospective, nonrandomized study. To assess the accuracy of O-arm navigation-based pedicle screw insertion in lumbar degenerative spondylolisthesis and to compare it with free-hand pedicle screw insertion technique in matched population. O-arm navigation is latest in navigation technology that can provide real-time intraoperative images in 3 dimensions while placing the pedicle screws to improve intraoperative pedicle screw accuracy. Degenerative lumbar spondylolisthesis is a locally unstable pathology and placement of pedicle screws can cause increased rotation and translation of the vertebral body. However, is this motion detected by the tracker placed across the unstable segment, is a matter of debate. Inability to detect these positional changes can lead to pedicle perforation while inserting screws using navigation. No study has evaluated the role of O-arm navigation in this patient population. The study population was divided into 2 groups with 19 patients each, one comprising patients who underwent O-arm navigation-based pedicle screw insertion (group 1) and the other comprising patients who underwent free-hand pedicle screw insertion technique (group 2). A total of 152 pedicle screws were implanted in 38 patients for 1-level instrumented fusion for degenerative lumbar spondylolisthesis. Intraoperative 3-dimensional computed tomography scans using the O-arm were obtained for all patients after insertion of pedicle screws. The images were reviewed intraoperatively and postoperatively for the analysis of pedicle breaches. Assessments in either of the group included (i) accuracy of placement of screws; (ii) the rate and direction of perforation; and (iii) the number of segments the perforated screw was away from the navigation tracker. Mean age of patients in group 1 (O-arm navigation-assisted) was 60 years (SD 11.25; range, 37-73 y), whereas in group 2 (free-hand pedicle screw) was 62 years (SD 18.07; range, 36-90 y). Overall anatomic perforation

Biomechanical and histological evaluation of an expandable pedicle screw in osteoporotic spine in sheep

PubMed Central

Wan, Shiyong; Wu, Zixiang; Liu, Da; Gao, Mingxuan; Fu, Suochao

2010-01-01

Transpedicular fixation can be challenging in the osteoporotic spine as reduced bone mineral density compromises the mechanical stability of the pedicle screw. Here, we sought to investigate the biomechanical and histological properties of stabilization of expandable pedicle screw (EPS) in the osteoporotic spine in sheep. EPSs and standard pedicle screws, SINO screws, were inserted on the vertebral bodies in four female ovariectomized sheep. Pull-out and cyclic bending resistance test were performed to compare the holding strength of these pedicle screws. High-resolution micro-computed tomography (CT) was performed for three-dimensional image reconstruction. We found that the EPSs provided a 59.6% increase in the pull-out strength over the SINO screws. Moreover, the EPSs withstood a greater number of cycles or load with less displacement before loosening. Micro-CT image reconstruction showed that the tissue mineral density, bone volume fraction, bone surface/bone volume ratio, trabecular thickness, and trabecular separation were significantly better in the expandable portion of the EPSs than those in the anterior portion of the SINO screws (P < 0.05). Furthermore, the trabecular architecture in the screw–bone interface was denser in the expandable portion of the EPS than that in the anterior portion of the SINO screw. Histologically, newly formed bone tissues grew into the center of EPS and were in close contact with the EPS. Our results show that the EPS demonstrates improved biomechanical and histological properties over the standard screw in the osteoporotic spine. The EPS may be of value in treating patients with osteoporosis and warrants further clinical studies. PMID:20577766

Adjacent-segment disease after thoracic pedicle screw fixation.

PubMed

Agarwal, Nitin; Heary, Robert F; Agarwal, Prateek

2018-03-01

OBJECTIVE Pedicle screw fixation is a technique widely used to treat conditions ranging from spine deformity to fracture stabilization. Pedicle screws have been used traditionally in the lumbar spine; however, they are now being used with increasing frequency in the thoracic spine as a more favorable alternative to hooks, wires, or cables. Although safety concerns, such as the incidence of adjacent-segment disease (ASD) after cervical and lumbar fusions, have been reported, such issues in the thoracic spine have yet to be addressed thoroughly. Here, the authors review the literature on ASD after thoracic pedicle screw fixation and report their own experience specifically involving the use of pedicle screws in the thoracic spine. METHODS Select references from online databases, such as PubMed (provided by the US National Library of Medicine at the National Institutes of Health), were used to survey the literature concerning ASD after thoracic pedicle screw fixation. To include the authors' experience at Rutgers New Jersey Medical School, a retrospective review of a prospectively maintained database was performed to determine the incidence of complications over a 13-year period in 123 consecutive adult patients who underwent thoracic pedicle screw fixation. Children, pregnant or lactating women, and prisoners were excluded from the review. By comparing preoperative and postoperative radiographic images, the occurrence of thoracic ASD and disease within the surgical construct was determined. RESULTS Definitive radiographic fusion was detected in 115 (93.5%) patients. Seven incidences of instrumentation failure and 8 lucencies surrounding the screws were observed. One patient was observed to have ASD of the thoracic spine. The mean follow-up duration was 50 months. CONCLUSIONS This long-term radiographic evaluation revealed the use of pedicle screws for thoracic fixation to be an effective stabilization modality. In particular, ASD seems to be less of a problem in the

Effect of augmentation techniques on the failure of pedicle screws under cranio-caudal cyclic loading.

PubMed

Bostelmann, Richard; Keiler, Alexander; Steiger, Hans Jakob; Scholz, Armin; Cornelius, Jan Frederick; Schmoelz, Werner

2017-01-01

Augmentation of pedicle screws is recommended in selected indications (for instance: osteoporosis). Generally, there are two techniques for pedicle screw augmentation: inserting the screw in the non cured cement and in situ-augmentation with cannulated fenestrated screws, which can be applied percutaneously. Most of the published studies used an axial pull out test for evaluation of the pedicle screw anchorage. However, the loading and the failure mode of pullout tests do not simulate the cranio-caudal in vivo loading and failure mechanism of pedicle screws. The purpose of the present study was to assess the fixation effects of different augmentation techniques (including percutaneous cement application) and to investigate pedicle screw loosening under physiological cyclic cranio-caudal loading. Each of the two test groups consisted of 15 vertebral bodies (L1-L5, three of each level per group). Mean age was 84.3 years (SD 7.8) for group 1 and 77.0 years (SD 7.00) for group 2. Mean bone mineral density was 53.3 mg/cm 3 (SD 14.1) for group 1 and 53.2 mg/cm 3 (SD 4.3) for group 2. 1.5 ml high viscosity PMMA bone cement was used for all augmentation techniques. For test group 1, pedicles on the right side of the vertebrae were instrumented with solid pedicle screws in standard fashion without augmentation and served as control group. Left pedicles were instrumented with cannulated screws (Viper cannulated, DePuy Spine) and augmented. For test group 2 pedicles on the left side of the vertebrae were instrumented with cannulated fenestrated screws and in situ augmented. On the right side solid pedicle screws were augmented with cement first technique. Each screw was subjected to a cranio-caudal cyclic load starting at 20-50 N with increasing upper load magnitude of 0.1 N per cycle (1 Hz) for a maximum of 5000 cycles or until total failure. Stress X-rays were taken after cyclic loading to evaluate screw loosening. Test group 1 showed a significant higher number of

Effect of various factors on pull out strength of pedicle screw in normal and osteoporotic cancellous bone models.

PubMed

Varghese, Vicky; Saravana Kumar, Gurunathan; Krishnan, Venkatesh

2017-02-01

Pedicle screws are widely used for the treatment of spinal instability by spine fusion. Screw loosening is a major problem of spine fusion, contributing to delayed patient recovery. The present study aimed to understand the factor and interaction effects of density, insertion depth and insertion angle on pedicle screw pull out strength and insertion torque. A pull out study was carried out on rigid polyurethane foam blocks representing osteoporotic to normal bone densities according to the ASTM-1839 standard. It was found that density contributes most to pullout strength and insertion torque. The interaction effect is significant (p < 0.05) and contributes 8% to pull out strength. Axial pullout strength was 34% lower than angled pull out strength in the osteoporotic bone model. Insertion angle had no significant effect (p > 0.05) on insertion torque. Pullout strength and insertion torque had no significant correlation (p > 0.05) in the case of the extremely osteoporotic bone model. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Evaluation of Titanium-Coated Pedicle Screws: In Vivo Porcine Lumbar Spine Model.

PubMed

Kim, Do-Yeon; Kim, Jung-Ryul; Jang, Kyu Yun; Kim, Min Gu; Lee, Kwang-Bok

2016-07-01

Many studies have addressed the problem of loosening pedicle screws in spinal surgery, which is a serious concern. Titanium coating of medical implants (arthroplasty) is common, but few studies involving in vivo spine models have been reported. We evaluated the radiological, mechanical, and histological characteristics of titanium-coated pedicle screws compared with uncoated or hydroxyapatite-coated pedicle screws. Three different types of pedicle screws, i.e., uncoated, hydroxyapatite-coated, and titanium-coated, were implanted into the lumbar 3-4-5 levels of 9 mature miniature pigs. Radiological evaluation of loosening of pedicle screws was performed. Peak torsional extraction torque was tested in the 42 screws from 7 miniature pigs at 12 weeks postoperatively. The implant-bone interface of the remaining 12 pedicle screws from 2 miniature pigs in each group was assessed by micro-computed tomography and histologic studies. The incidence of loosening at 12 weeks postoperatively was not significantly different between the titanium-coated pedicle screw group and the other groups. The titanium-coated pedicle screw group exhibited the greatest mean extraction torsional peak torque at 12 weeks postoperatively (P < 0.05). Quantitative micro-computed tomography data were greatest in the titanium-coated pedicle screw group (P < 0.05). Histologic findings showed osteointegration with densely packed new bone formation at the screw coating-bone interface in the titanium-coated pedicle screw group. Fixation strength was greatest in the titanium-coated pedicle screw group. Osteointegration at the interface between the titanium-coated implant and bone produced prominent and firm bonding. The titanium-coated pedicle screw is a promising device for application in spinal surgery. Copyright © 2016 Elsevier Inc. All rights reserved.

Comparison of the Pullout Strength of Different Pedicle Screw Designs and Augmentation Techniques in an Osteoporotic Bone Model.

PubMed

Kiyak, Gorkem; Balikci, Tevfik; Heydar, Ahmed Majid; Bezer, Murat

2018-02-01

Mechanical study. To compare the pullout strength of different screw designs and augmentation techniques in an osteoporotic bone model. Adequate bone screw pullout strength is a common problem among osteoporotic patients. Various screw designs and augmentation techniques have been developed to improve the biomechanical characteristics of the bone-screw interface. Polyurethane blocks were used to mimic human osteoporotic cancellous bone, and six different screw designs were tested. Five standard and expandable screws without augmentation, eight expandable screws with polymethylmethacrylate (PMMA) or calcium phosphate augmentation, and distal cannulated screws with PMMA and calcium phosphate augmentation were tested. Mechanical tests were performed on 10 unused new screws of each group. Screws with or without augmentation were inserted in a block that was held in a fixture frame, and a longitudinal extraction force was applied to the screw head at a loading rate of 5 mm/min. Maximum load was recorded in a load displacement curve. The peak pullout force of all tested screws with or without augmentation was significantly greater than that of the standard pedicle screw. The greatest pullout force was observed with 40-mm expandable pedicle screws with four fins and PMMA augmentation. Augmented distal cannulated screws did not have a greater peak pullout force than nonaugmented expandable screws. PMMA augmentation provided a greater peak pullout force than calcium phosphate augmentation. Expandable pedicle screws had greater peak pullout forces than standard pedicle screws and had the advantage of augmentation with either PMMA or calcium phosphate cement. Although calcium phosphate cement is biodegradable, osteoconductive, and nonexothermic, PMMA provided a significantly greater peak pullout force. PMMA-augmented expandable 40-mm four-fin pedicle screws had the greatest peak pullout force.

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.

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.

The accuracy and safety of fluoroscopic-guided percutaneous pedicle screws in the thoracic and lumbosacral spine in the Asian population: A CT scan analysis of 1002 screws.

PubMed

Chiu, Chee Kidd; Chan, Chris Yin Wei; Kwan, Mun Keong

2017-01-01

This study investigates the safety and accuracy of percutaneous pedicle screws placed using fluoroscopic guidance in the thoracolumbosacral spine among Asian patients. Computerized tomography scans of 128 patients who had surgery using fluoroscopic-guided percutaneous pedicle screws were selected. Medial, lateral, superior, and inferior screw perforations were classified into grade 0 (no violation), grade 1 (<2 mm perforation), grade 2 (2-4 mm perforation), and grade 3(>4 mm perforation). Anterior perforations were classified into grade 0 (no violation), grade 1 (<4 mm perforation), grade 2 (4-6 mm perforation), and grade 3(>6 mm perforation). Grade 2 and grade 3 perforation were considered as "critical" perforation. In total, 1002 percutaneous pedicle screws from 128 patients were analyzed. The mean age was 52.7 ± 16.6. There were 70 male patients and 58 female patients. The total perforation rate was 11.3% (113) with 8.4% (84) grade 1, 2.6% (26) grade 2, and 0.3% (3) grade 3 perforations. The overall "critical" perforation rate was 2.9% (29 screws) and no complications were noted. The highest perforation rates were at T4 (21.6%), T2 (19.4%), and T6 (19.2%). The total perforation rate of 11.3% with the total "critical" perforation rate of 2.9% (2.6% grade 2 and 0.3% grade 3 perforations). The highest perforation rates were found over the upper to mid-thoracic region. Fluoroscopic-guided percutaneous pedicle screws insertion among Asians has the safety and accuracy comparable to the current reported percutaneous pedicle screws and open pedicle screws techniques.

A novel cost-effective computer-assisted imaging technology for accurate placement of thoracic pedicle screws.

PubMed

Abe, Yuichiro; Ito, Manabu; Abumi, Kuniyoshi; Kotani, Yoshihisa; Sudo, Hideki; Minami, Akio

2011-11-01

Use of computer-assisted spine surgery (CASS) technologies, such as navigation systems, to improve the accuracy of pedicle screw (PS) placement is increasingly popular. Despite of their benefits, previous CASS systems are too expensive to be ubiquitously employed, and more affordable and portable systems are desirable. The aim of this study was to introduce a novel and affordable computer-assisted technique that 3-dimensionally visualizes anatomical features of the pedicles and assists in PS insertion. The authors have termed this the 3D-visual guidance technique for inserting pedicle screws (3D-VG TIPS). The 3D-VG technique for placing PSs requires only a consumer-class computer with an inexpensive 3D DICOM viewer; other special equipment is unnecessary. Preoperative CT data of the spine were collected for each patient using the 3D-VG TIPS. In this technique, the anatomical axis of each pedicle can be analyzed by volume-rendered 3D models, as with existing navigation systems, and both the ideal entry point and the trajectory of each PS can be visualized on the surface of 3D-rendered images. Intraoperative guidance slides are made from these images and displayed on a TV monitor in the operating room. The surgeon can insert PSs according to these guidance slides. The authors enrolled 30 patients with adolescent idiopathic scoliosis (AIS) who underwent posterior fusion with segmental screw fixation for validation of this technique. The novel technique allowed surgeons, from office or home, to evaluate the precise anatomy of each pedicle and the risks of screw misplacement, and to perform 3D preoperative planning for screw placement on their own computer. Looking at both 3D guidance images on a TV monitor and the bony structures of the posterior elements in each patient in the operating theater, surgeons were able to determine the best entry point for each PS with ease and confidence. Using the current technique, the screw malposition rate was 4.5% in the thoracic

Use of a life-size three-dimensional-printed spine model for pedicle screw instrumentation training.

PubMed

Park, Hyun Jin; Wang, Chenyu; Choi, Kyung Ho; Kim, Hyong Nyun

2018-04-16

Training beginners of the pedicle screw instrumentation technique in the operating room is limited because of issues related to patient safety and surgical efficiency. Three-dimensional (3D) printing enables training or simulation surgery on a real-size replica of deformed spine, which is difficult to perform in the usual cadaver or surrogate plastic models. The purpose of this study was to evaluate the educational effect of using a real-size 3D-printed spine model for training beginners of the free-hand pedicle screw instrumentation technique. We asked whether the use of a 3D spine model can improve (1) screw instrumentation accuracy and (2) length of procedure. Twenty life-size 3D-printed lumbar spine models were made from 10 volunteers (two models for each volunteer). Two novice surgeons who had no experience of free-hand pedicle screw instrumentation technique were instructed by an experienced surgeon, and each surgeon inserted 10 pedicle screws for each lumbar spine model. Computed tomography scans of the spine models were obtained to evaluate screw instrumentation accuracy. The length of time in completing the procedure was recorded. The results of the latter 10 spine models were compared with those of the former 10 models to evaluate learning effect. A total of 37/200 screws (18.5%) perforated the pedicle cortex with a mean of 1.7 mm (range, 1.2-3.3 mm). However, the latter half of the models had significantly less violation than the former half (10/100 vs. 27/100, p < 0.001). The mean length of time to complete 10 pedicle screw instrumentations in a spine model was 42.8 ± 5.3 min for the former 10 spine models and 35.6 ± 2.9 min for the latter 10 spine models. The latter 10 spine models had significantly less time than the former 10 models (p < 0.001). A life-size 3D-printed spine model can be an excellent tool for training beginners of the free-hand pedicle screw instrumentation.

Accuracy of a dynamic surgical guidance probe for screw insertion in the cervical spine: a cadaveric study.

PubMed

Dixon, Daniel; Darden, Bruce; Casamitjana, Jose; Weissmann, Karen A; Cristobal, San; Powell, David; Baluch, Daniel

2017-04-01

A fresh frozen cadaver study was conducted. To report the cortical breach rate using the dynamic surgical guidance (DSG) probe versus traditional freehand technique for cervical lateral mass, cervical pedicle and cervical laminar screws. Nine male fresh frozen cadaveric torsos were utilized for this study. Each investigator was assigned three specimens that were randomized by fixation point, side and order of technique for establishing a screw pilot hole. The technique for screw hole preparation utilized was either a DSG probe in the "on" mode or in the "off" mode using a freehand technique popularized by Lenke et al. Levels instrumented included C1 lateral mass, C2 pedicle screws and lamina screws, and C6-T1 pedicle screws. Fluoroscopy and other navigational assistance were not used for screw hole preparation or screw insertion. All specimens were CT imaged following insertion of all screws. A senior radiologist evaluated all scans and determined that a misplaced screw was a breach of ≥2 mm. A total of 104 drillings were performed, 52 with DSG and 52 without DSG There were 68 total pedicle drillings, 34 in each group. There were 18 drillings in the lamina and lateral mass. There was no significant difference between surgeons or between the left and right side. All breaches were in the pedicle, and none in the lamina or lateral mass. The breach rate for PG "on" was 6/68 = 8.96% (95% CI 3.69, 19.12%). The breach rate for PG "off" was 20/68 = 29.41% (95% CI 19.30, 41.87%). Of the 20 pedicle breaches in the non-DSG group, 7 were lateral and superior, 8 were lateral, 4 medial and 1 inferior. Of the six pedicle breaches in the DSG group, two were lateral/superior, two were lateral and two were medial in the pedicle. The dynamic surgical guidance probe is a safe tool to assist the surgeon with screw placement in the cervical spine. Additionally, the DSG potentially avoids the cumulative risks associated with fluoroscopy and provides real-time feedback to the

Comparison of 2 kinds of pedicle screws in primary spinal instrumentation: biomechanical and interfacial evaluations in sheep vertebrae in vitro.

PubMed

Liu, Da; Zhang, Yi; Lei, Wei; Wang, Cai-ru; Xie, Qing-yun; Liao, Dong-fa; Jiang, Kai; Zhou, Jin-song; Zhang, Bo; Pan, Xian-ming

2014-04-01

Expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) were inserted in sheep vertebrae in vitro and were evaluated by performing biomechanical tests, radiographic examinations and histological observations. The objective of the study was to compare the biomechanical and interfacial performances of EPS and PMMA-PS in sheep lumbar vertebrae in vitro. It is a great challenge for orthopedic surgeons performing transpedicular fixation in the osteoporotic spine. It was reported that either the EPS or PMMA-PS could increase the screw stability. However, there are no studies comparing the 2 kinds of screws especially in primary spinal instrumentation. A total of 60 sheep lumbar vertebrae were randomly divided into 3 groups. A pilot hole was made in advance in all samples using the same method. Thereafter, the conventional pedicle screw (CPS) was inserted directly into the pilot hole in the CPS group; the hole in PMMA-PS group was first filled with polymethylmethacrylate (PMMA; 1.0 mL) and then inserted with CPS; and the EPS was inserted directly into the vertebrae in EPS group. After a period of 24 hours, biomechanical tests were performed to evaluate screw stability, and x-ray examination, micro-computerized tomography analysis, and histologic observation were performed to evaluate the interface between screw and bone. Compared with the stability of CPS, those of EPS and PMMA-PS were significantly enhanced. However, no significant differences were detected between the stabilities of EPS and PMMA-PS. The PMMA surrounding the screw blocked direct contact between bone and screw and formed a "screw-PMMA-bone" interface in the PMMA-PS group. There was a "screw-bone" interface in both CPS and EPS groups. Nevertheless, the expanded anterior part of EPS formed a claw-like structure pressing the surrounding bone trabeculae, which made the local bone tissue more compacted and denser than that in the CPS group. EPS can enhance the screw stability

Computed tomography assessment of lateral pedicle wall perforation by free-hand subaxial cervical pedicle screw placement.

PubMed

Wang, Yingsong; Xie, Jingming; Yang, Zhendong; Zhao, Zhi; Zhang, Ying; Li, Tao; Liu, Luping

2013-07-01

To present the technique of free-hand subaxial cervical pedicle screw (CPS) placement without using intra-operative navigating devices, and to investigate the crucial factors for safe placement and avoidance of lateral pedicle wall perforation, by measuring and classifying perforations with postoperative computed tomography (CT) scan. The placement of CPS has generally been considered as technically demanding and associated with considerable lateral wall perforation rate. For surgeons without access to navigation systems, experience of safe free-hand technique for subaxial CPS placement is especially valuable. A total of 214 consecutive traumatic or degenerative patients with 1,024 CPS placement using the free-hand technique were enrolled. In the operative process, the lateral mass surface was decorticated. Then a small curette was used to identify the pedicle entrance by touching the cortical bone of the medial pedicle wall. It was crucial to keep the transverse angle and make appropriate adjustment with guidance of the resistance of the thick medial cortical bone. The hand drill should be redirected once soft tissue breach was palpated by a slim ball-tip prober. With proper trajectory, tapping, repeated palpation, the 26-30 mm screw could be placed. After the procedure, the transverse angle of CPS trajectory was measured, and perforation of the lateral wall was classified by CT scan: grade 1, perforation of pedicle wall by screw placement, with the external edge of screw deviating out of the lateral pedicle wall equal to or less than 2 mm and grade 2, critical perforation of pedicle wall by screw placement, large than 2 mm. A total of 129 screws (12.64 %) were demonstrated as lateral pedicle wall perforation, of which 101 screws (9.86 %) were classified as grade 1, whereas 28 screws (2.73 %) as grade 2. Among the segments involved, C3 showed an obviously higher perforating rate than other (P < 0.05). The difference between the anatomical pedicle transverse angle

Prevention of Proximal Junctional Kyphosis: Are Polyaxial Pedicle Screws Superior to Monoaxial Pedicle Screws at the Upper Instrumented Vertebrae?

PubMed

Wang, Hui; Ding, Wenyuan; Ma, Lei; Zhang, Lijun; Yang, Dalong

2017-05-01

Evidence regarding whether the polyaxial pedicle screws at the upper instrumented vertebrae (UIV) are superior to monoaxial pedicle screws in prevention of proximal junctional kyphosis (PJK) is not clear. The aim of this study was therefore to explore the influence of different types of pedicle screws at UIV on the incidence of PJK. We reviewed retrospectively 242 patients surgically treated with instrumented segmental posterior spinal fusion at a minimum of 4 motion segments. Polyaxial pedicle screws were used at UIV in 125 patients (polyaxial group), and monoaxial pedicle screws were used at UIV in 117 patients (monoaxial group). According to the occurrence of PJK at final follow-up, patients in both the polyaxial and monoaxial groups were then divided into 2 subgroups: PJK and no proximal junctional kyphosis (NPJK). To investigate the risk factors of PJK, 2 categorized variables were analyzed statistically: 1) patient characteristics: age, sex, body mass index (BMI), bone mineral density (BMD), sagittal vertical axis (SVA), thoracic kyphosis, thoracolumbar junctional angle, lumbar lordosis (LL), pelvic incidence, pelvic tilt, and sacral slope. 2) Surgical variables: Changes of radiographic parameters include the SVA, thoracic kyphosis, thoracolumbar junctional, LL, pelvic incidence, pelvic tilt, sacral slope, pedicle-upper end plate angle, the number of instrumented levels, and the most proximal and distal levels of the instrumentation. PJK was developed in 26 of 117 patients (22.2%) in the monoaxial group and 30 of 125 patients (24.0%) in the polyaxial group. Until the final follow-up, there was no significant difference in the incidence of PJK (χ2 = 0.107, P = 0.734) between the monoaxial and polyaxial groups. There was no significant difference in patient characteristics and surgical variables between the 2 groups, except the proximal junctional angle change (P = 0.031). In the monoaxial group, there were no significant differences in patient

Accuracy of pedicle screw placement in patients with Marfan syndrome.

PubMed

Qiao, Jun; Zhu, Feng; Xu, Leilei; Liu, Zhen; Sun, Xu; Qian, Bangping; Jiang, Qing; Zhu, Zezhang; Qiu, Yong

2017-03-21

There is no study concerning safety and accuracy of pedicle screw placement in Marfan syndrome. The objective of this study is to investigate accuracy and safety of pedicle screw placement in scoliosis associated with Marfan syndrome. CT scanning was performed to analyze accuracy of pedicle screw placement. Pedicle perforations were classified as medial, lateral or anterior and categorized to four grades: ≤ 2 mm as Grade 1, 2.1-4.0 mm as Grade 2, 4.1-6.0 mm as Grade 3, ≥6.1 mm as Grade 4. Fully contained screws or with medial wall perforation ≤ 2 mm or with lateral wall perforation ≤ 6 mm and without injury of visceral organs were considered acceptable, otherwise were unacceptable. 976 pedicle screws were placed, 713 screws (73.1%) were fully contained within the cortical boundaries of the pedicle. 924 (94.7%) screws were considered as acceptable, and 52 (5.3%) as unacceptable. The perforation rate was higher using free-hand technique than O-arm navigation technique (30.8% VS. 11.4%, P < 0.05), higher in lumbar region than in thoracic region (34.1% VS. 22.3%, P < 0.05) and higher in concave side than in convex side (33.5% VS. 21.9%, P < 0.05). No injury of visceral organs especially aorta erosion was noted in the series. 7 cases of dural tear caused by misplaced screws occurred, and 4 cases developed cerebro-spinal fluid leak. Drainage and pressure dressings were applied for these patients, and no infection was observed. Leg pain was observed in 7 cases, and 2 cases simultaneously complained of leg weakness. Revision surgery was conducted to remove the misplaced screws for these 2 patients. Conservative treatment was applied for the 5 patients without leg weakness. Symptoms of leg weakness and pain resolved in all patients. Placement of pedicle screw in Marfan syndrome is accuracy and safe. O-arm navigation was an effective modality to ensure the safety and accuracy of screw placement. Special attention should be paid when screws

Are We Underestimating the Significance of Pedicle Screw Misplacement?

PubMed

Sarwahi, Vishal; Wendolowski, Stephen F; Gecelter, Rachel C; Amaral, Terry; Lo, Yungtai; Wollowick, Adam L; Thornhill, Beverly

2016-05-01

A retrospective review of charts, x-rays (XRs) and computed tomography (CT) scans was performed. To evaluate the accuracy of pedicle screw placement using a novel classification system to determine potentially significant screw misplacement. The accuracy rate of pedicle screw (PS) placement varies from 85% to 95% in the literature. This demonstrates technical ability but does not represent the impact of screw misplacement on individual patients. This study quantifies the rate of screw misplacement on a per-patient basis to highlight its effect on potential morbidity. A retrospective review of charts, XRs and low-dose CT scans of 127 patients who underwent spinal fusion with pedicle screws for spinal deformity was performed. Screws were divided into four categories: screws at risk (SAR), indeterminate misplacements (IMP), benign misplacements (BMP), accurately placed (AP). A total of 2724 screws were placed in 127 patients. A total of 2396 screws were placed accurately (87.96%). A total of 247 screws (9.07%) were BMP, 52 (1.91%) were IMP, and 29 (1.06%) were considered SAR. Per-patient analysis showed 23 (18.11%) of patients had all screws AP. Thirty-five (27.56%) had IMP and 18 (14.17%) had SAR. Risk factor analysis showed smaller Cobb angles increased likelihood of all screws being AP. Sub-analysis of adolescent idiopathic scoliotic patients showed no curve or patient characteristic that correlated with IMP or SAR. Over 40% of patients had screws with either some/major concern. Overall reported screw misplacement is low, but it does not reflect the potential impact on patient morbidity. Per-patient analysis reveals more concerning numbers toward screw misplacement. With increasing pedicle screw usage, the number of patients with misplaced screws will likely increase proportionally. Better strategies need to be devised for evaluation of screw placement, including establishment of a national database of deformity surgery, use of intra-operative image guidance, and

Does intraoperative navigation improve the accuracy of pedicle screw placement in the apical region of dystrophic scoliosis secondary to neurofibromatosis type I: comparison between O-arm navigation and free-hand technique.

PubMed

Jin, Mengran; Liu, Zhen; Liu, Xingyong; Yan, Huang; Han, Xiao; Qiu, Yong; Zhu, Zezhang

2016-06-01

To assess the accuracy of O-arm-navigation-based pedicle screw insertion in dystrophic scoliosis secondary to NF-1 and compare it with free-hand pedicle screw insertion technique. 32 patients with dystrophic NF-1-associated scoliosis were divided into two groups. A total of 92 pedicle screws were implanted in apical region (two vertebrae above and below the apex each) in 13 patients using O-arm-based navigation (O-arm group), and 121 screws were implanted in 19 patients using free-hand technique (free-hand group). The postoperative CT images were reviewed and analyzed for pedicle violation. The screw penetration was divided into four grades: grade 0 (ideal placement), grade 1 (penetration <2 mm), grade 2 (penetration between 2 and 4 mm), and grade 3 (penetration >4 mm). The accuracy rate of pedicle screw placement (grade 0, 1) was significantly higher in the O-arm group (79 %, 73/92) compared to 67 % (81/121) of the free-hand group (P = 0.045). Meanwhile, a significantly lower prevalence of grade 2-3 perforation was observed in the O-arm group (21 vs. 33 %, P < 0.05), and the incidence of medial perforation was significantly minimized by using O-arm navigation compared to free-hand technique (2 vs. 15 %, P < 0.01). Moreover, the implant density in apical region was significantly elevated by using O-arm navigation (58 vs. 42 %, P < 0.001). We reported 79 % accuracy of O-arm-based pedicle screw placement in dystrophic NF-1-associated scoliosis. O-arm navigation system does facilitate pedicle screw insertion in dystrophic NF-1-associated scoliosis, demonstrating superiorities in the safety and accuracy of pedicle screw placement in comparison with free-hand technique.

Monoaxial Pedicle Screws Are Superior to Polyaxial Pedicle Screws and the Two Pin External Fixator for Subcutaneous Anterior Pelvic Fixation in a Biomechanical Analysis

PubMed Central

Vaidya, Rahul; Onwudiwe, Ndidi; Roth, Matthew; Sethi, Anil

2013-01-01

Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 ± 0.113 Nmm monoaxial, 3.638 ± 0.108 Nmm Click-x; 3.634 ± 0.147 Nmm Pangea) than the exfix system (2.882 ± 0.054 Nmm) in distraction. In failure testing, monoaxial pedicle screw system was stronger (360 N) than exfixes (160 N) and polyaxial devices which failed if distracted greater than 4 cm (157 N Click-x or 138 N Pangea). The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360 N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems. PMID:24368943

Monoaxial pedicle screws are superior to polyaxial pedicle screws and the two pin external fixator for subcutaneous anterior pelvic fixation in a biomechanical analysis.

PubMed

Vaidya, Rahul; Onwudiwe, Ndidi; Roth, Matthew; Sethi, Anil

2013-01-01

Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 ± 0.113 Nmm monoaxial, 3.638 ± 0.108 Nmm Click-x; 3.634 ± 0.147 Nmm Pangea) than the exfix system (2.882 ± 0.054 Nmm) in distraction. In failure testing, monoaxial pedicle screw system was stronger (360 N) than exfixes (160 N) and polyaxial devices which failed if distracted greater than 4 cm (157 N Click-x or 138 N Pangea). The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360 N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems.

Biomechanical comparative study of the stability of injectable pedicle screws with different lateral holes augmented with different volumes of polymethylmethacrylate in osteoporotic lumbar vertebrae.

PubMed

Liu, Da; Sheng, Jun; Luo, Yang; Huang, Chen; Wu, Hong-Hua; Zhou, Jiang-Jun; Zhang, Xiao-Jun; Zheng, Wei

2018-03-19

Polymethylmethacrylate (PMMA) is widely used for pedicle screw augmentation in osteoporosis. Until now, there had been no studies of the relationship between screw stability and the distribution and volume of PMMA. The objective of this study was to analyze the relationship between screw stability and the distribution pattern and injected volume of PMMA. This is a biomechanical comparison of injectable pedicle screws with different lateral holes augmented with different volumes of PMMA in cadaveric osteoporotic lumbar vertebrae. Forty-eight osteoporotic lumbar vertebrae were randomly divided into Groups A, B, and C with different pedicle screws (16 vertebrae in each group), and then each group was randomly divided into Subgroups 0, 1, 2, and 3 with different volumes of PMMA (four vertebra with eight pedicles in each subgroup). A pilot hole was prepared in advance using the same method in all samples. Type A and type B pedicle screws were directly inserted into vertebrae in Groups A and B, respectively, and then different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL) were injected through the screws and into vertebrae in Subgroups 0, 1, 2, and 3. The pilot holes were filled with different volumes of PMMA (0, 1.0, 1.5, and 2.0 mL), and then the screws were inserted in Groups C0, C1, C2, and C3. Screw position and distribution of PMMA were evaluated radiographically, and axial pullout tests were performed to measure maximum axial pullout strength (F max ). Polymethylmethacrylate surrounded the anterior one-third of screws in the vertebral body in Groups A1, A2, and A3; the middle one-third of screws in the junction area of the vertebral body and the pedicle in Groups B1, B2, and B3; and the full length of screws evenly in both the vertebral body and the pedicle in Groups C1, C2, and C3. There was no malpositioning of screws or leakage of PMMA in any sample. Two-way analysis of variance revealed that two factors-distribution and volume of PMMA-significantly influenced

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

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

PubMed

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

2017-01-01

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. 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. 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. The individualized 3D printing navigation template for

Reliability of roentgenogram evaluation of pedicle screw position.

PubMed

Ferrick, M R; Kowalski, J M; Simmons, E D

1997-06-01

This was a human cadaver study of the accuracy of biplanar roentgenography in determining pedicle screw position. To determine the independent accuracy of radiologic evaluation of screw placement and to determine if there are any particular screw malpositions that are more likely to produce a false sense of acceptable screw position. Other investigators have reported the correlation between radiologic evaluation and anatomic dissection. However, in those studies the radiologic evaluation was not independent of the surgeons placing the screws. There has been no comment in the literature regarding particular screw malpositions that would lead the surgeon into a false sense of successful screw placement. Pedicle screws were placed in cadaver spines, and biplanar roentgenograms of the specimens were evaluated by independent observers. The results of the roantgenogram evaluation then were compared to those of the anatomic dissection. The accuracy of roentgenogram evaluation varied from 73% to 83%, depending on the experience of the surgeon grading the roentgenograms. Screws misplaced medially into the spinal canal are more likely to give the surgeon a false sense of successful screw placement. The surgeon must not rely solely on the roentgenograms, but instead continue to use tactile sensory skills, anatomic knowledge, and additional modalities such as electromyography monitoring.

Posterior Surgery for Adolescent Idiopathic Scoliosis With Pedicle Screws and Ultrahigh-Molecular Weight Polyethylene Tape: Achieving the Ideal Thoracic Kyphosis.

PubMed

Imagama, Shiro; Ito, Zenya; Wakao, Norimitsu; Ando, Kei; Hirano, Kenichi; Tauchi, Ryoji; Muramoto, Akio; Matsui, Hiroki; Matsumoto, Tomohiro; Sakai, Yoshihito; Katayama, Yoshito; Matsuyama, Yukihiro; Ishiguro, Naoki

2016-10-01

Prospective clinical case series. To describe our surgical procedure and results for posterior correction and fusion with a hybrid approach using pedicle screws, hooks, and ultrahigh-molecular weight polyethylene tape with direct vertebral rotation (DVR) (the PSTH-DVR procedure) for treatment of adolescent idiopathic scoliosis (AIS) with satisfactory correction in the coronal and sagittal planes. Introduction of segmental pedicle screws in posterior surgery for AIS has facilitated good correction and fusion. However, procedures using only pedicle screws have risks during screw insertion, higher costs, and decreased postoperative thoracic kyphosis. We have obtained good outcomes compared with segmental pedicle screw fixation in surgery for AIS using a relatively simple operative procedure (PSTH-DVR) that uses fewer pedicle screws. The subjects were 30 consecutive patients with AIS who underwent the PSTH-DVR procedure and were followed for a minimum of 2 years. Preoperative flexibility, preoperative and postoperative Cobb angles, correction rates, loss of correction, thoracic kyphotic angles (T5-T12), coronal balance, sagittal balance, and shoulder balance were measured on plain radiographs. Rib hump, operation time, estimated blood loss, spinal cord monitoring findings, complications, and scoliosis research society (SRS)-22 scores were also examined. The mean preoperative curve of 58.0 degrees (range, 40-96 degrees) was corrected to a mean of 9.9 degrees postoperatively, and the correction rate was 83.6%. Fusion was obtained in all patients without loss of correction. In 10 cases with preoperative kyphosis angles (T5-T12) <10 degrees, the preoperative mean of 5.8 degrees improved to 20.2 degrees at the final follow-up. Rib hump and coronal, sagittal and shoulder balances were also improved, and good SRS-22 scores were achieved at final follow-up. The correction of deformity with PSTH-DVR is equivalent to that of all-pedicle screw constructs. The procedure gives

A new method to precisely control the depth of percutaneous screws into the pedicle by counting the rotation number of the screw with low radiation exposure: technical note.

PubMed

Li, Xu; Zhang, Feng; Zhang, Wenzhi; Shang, Xifu; Han, Jintao; Liu, Pengfei

2017-03-01

Technique note. To report a new method for precisely controlling the depth of percutaneous pedicle screws (PPS)-without radiation exposure to surgeons and less fluoroscopy exposure to patients than with conventional methods. PPS is widely used in minimal invasive spine surgery; the advantages include reduced muscle damage, pain, and hospital stays. However, placement of PPS demands repeated checking with fluoroscopy. Thus, radiation exposure is considerable for both surgeons and patients. The PPS depth was determined by counting rotations of the screws. The distance between screw threads can be measured for particular screws; thus, full rotations of the PPS results in the screw advancing in the pedicle the distance between screw threads. To fully insert screws into the pedicle, the number of full rotations is equal to the number of threads in the PPS. We applied this technique in 58 patients with thoracolumbar fracture. The position and depth of the screws was checked during the operation with the C-arm and after operation by anteroposterior X-ray film or computed tomography. No additional procedures were required to correct the screws; we observed no neurological deficits or malpositioning of the screws. In the screw placement procedure, the radiation exposure for surgeons is zero, and the patient is well protected from extensive radiation exposure. This method of counting rotation of screws is a safe way to precisely determine the depth of PPS in the placement procedure. IV.

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

A comparison of CT-based navigation techniques for minimally invasive lumbar pedicle screw placement.

PubMed

Wood, Martin; Mannion, Richard

2011-02-01

A comparison of 2 surgical techniques. To determine the relative accuracy of minimally invasive lumbar pedicle screw placement using 2 different CT-based image-guided techniques. Three-dimensional intraoperative fluoroscopy systems have recently become available that provide the ability to use CT-quality images for navigation during image-guided minimally invasive spinal surgery. However, the cost of this equipment may negate any potential benefit in navigational accuracy. We therefore assess the accuracy of pedicle screw placement using an intraoperative 3-dimensional fluoroscope for guidance compared with a technique using preoperative CT images merged to intraoperative 2-dimensional fluoroscopy. Sixty-seven patients undergoing minimally invasive placement of lumbar pedicle screws (296 screws) using a navigated, image-guided technique were studied and the accuracy of pedicle screw placement assessed. Electromyography (EMG) monitoring of lumbar nerve roots was used in all. Group 1: 24 patients in whom a preoperative CT scan was merged with intraoperative 2-dimensional fluoroscopy images on the image-guidance system. Group 2: 43 patients using intraoperative 3-dimensional fluoroscopy images as the source for the image guidance system. The frequencies of pedicle breach and EMG warnings (indicating potentially unsafe screw placement) in each group were recorded. The rate of pedicle screw misplacement was 6.4% in group 1 vs 1.6% in group 2 (P=0.03). There were no cases of neurologic injury from suboptimal placement of screws. Additionally, the incidence of EMG warnings was significantly lower in group 2 (3.7% vs. 10% (P=0.03). The use of an intraoperative 3-dimensional fluoroscopy system with an image-guidance system results in greater accuracy of pedicle screw placement than the use of preoperative CT scans, although potentially dangerous placement of pedicle screws can be prevented by the use of EMG monitoring of lumbar nerve roots.

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�

Does addition of crosslink to pedicle-screw-based instrumentation impact the development of the spinal canal in children younger than 5 years of age?

PubMed

Chen, Zhong-hui; Chen, Xi; Zhu, Ze-zhang; Wang, Bin; Qian, Bang-ping; Zhu, Feng; Sun, Xu; Qiu, Yong

2015-07-01

Use of pedicle screws has been popularized in the treatment of pediatric spinal deformity. Despite many studies regarding the effect of pedicle screws on the immature spine, there is no study concerning the impact of addition of crosslink to pedicle-screw-based instrumentation on the development of the spinal canal in young children. This study aims to determine the influence of the screw-rod-crosslink complex on the development of the spinal canal. This study reviewed 34 patients with congenital scoliosis (14 boys and 20 girls) who were treated with posterior-only hemivertebrectomy and pedicle-screw-based short-segment instrumentation before the age of 5 years. The mean age at surgery in this cohort was 37 ± 11 months (range 21-57 months). They were followed up for at least 24 months. Of these patients, 10 underwent only pedicle screw instrumentation without crosslink, and 24 with additional crosslink placement. The vertebrae were divided into three regions as follows: (1) S-CL (screw-crosslink) region, in which the vertebrae were inserted with bilateral pedicle screws and two rods connected with the crosslink; (2) S (screw) region, in which the vertebrae were inserted with bilateral pedicle screws but without crosslink; (3) NS (no screws) region, which comprised vertebrae cephalad or caudal to the instrumented region. The area, anteroposterior and transverse diameters of the spinal canal were measured at all vertebrae on the postoperative and last follow-up computed tomography axial images. The instrumentation-related parameters were also measured, including the distance between the bilateral screws and the screw base angles. The changes in the above measurements were compared between each region to evaluate the instrumentation's effect on the spinal canal growth. The mean follow-up was 37 ± 13 months (range 24-68 months) and the mean age at the last follow-up was 74 ± 20 months (range 46-119 months). In each region, the spinal canal dimensions significantly

Pedicle screw versus hybrid posterior instrumentation for dystrophic neurofibromatosis scoliosis.

PubMed

Wang, Jr-Yi; Lai, Po-Liang; Chen, Wen-Jer; Niu, Chi-Chien; Tsai, Tsung-Ting; Chen, Lih-Huei

2017-06-01

Surgical management of severe rigid dystrophic neurofibromatosis (NF) scoliosis is technically demanding and produces varying results. In the current study, we reviewed 9 patients who were treated with combined anterior and posterior fusion using different types of instrumentation (i.e., pedicle screw, hybrid, and all-hook constructs) at our institute.Between September 2001 and July 2010 at our institute, 9 patients received anterior release/fusion and posterior fusion with different types of instrumentation, including a pedicle screw construct (n = 5), a hybrid construct (n = 3), and an all-hook construct (n = 1). We compared the pedicle screw group with the hybrid group to analyze differences in preoperative curve angle, immediate postoperative curve reduction, and latest follow-up curve angle.The mean follow-up period was 9.5 ± 2.9 years. The average age at surgery was 10.3 ± 3.9 years. The average preoperative scoliosis curve was 61.3 ± 13.8°, and the average preoperative kyphosis curve was 39.8 ± 19.7°. The average postoperative scoliosis and kyphosis curves were 29.7 ± 10.7° and 21.0 ± 13.5°, respectively. The most recent follow-up scoliosis and kyphosis curves were 43.4 ± 17.3° and 29.4 ± 18.9°, respectively. There was no significant difference in the correction angle (either coronal or sagittal), and there was no significant difference in the loss of sagittal correction between the pedicle screw construct group and the hybrid construct group. However, the patients who received pedicle screw constructs had significantly less loss of coronal correction (P < .05). Two patients with posterior instrumentation, one with an all-hook construct and the other with a hybrid construct, required surgical revision because of progression of deformity.It is difficult to intraoperatively correct dystrophic deformity and to maintain this correction after surgery. Combined anterior release/fusion and posterior

Pedicle screw versus hybrid posterior instrumentation for dystrophic neurofibromatosis scoliosis

PubMed Central

Wang, Jr-Yi; Lai, Po-Liang; Chen, Wen-Jer; Niu, Chi-Chien; Tsai, Tsung-Ting; Chen, Lih-Huei

2017-01-01

Abstract Surgical management of severe rigid dystrophic neurofibromatosis (NF) scoliosis is technically demanding and produces varying results. In the current study, we reviewed 9 patients who were treated with combined anterior and posterior fusion using different types of instrumentation (i.e., pedicle screw, hybrid, and all-hook constructs) at our institute. Between September 2001 and July 2010 at our institute, 9 patients received anterior release/fusion and posterior fusion with different types of instrumentation, including a pedicle screw construct (n = 5), a hybrid construct (n = 3), and an all-hook construct (n = 1). We compared the pedicle screw group with the hybrid group to analyze differences in preoperative curve angle, immediate postoperative curve reduction, and latest follow-up curve angle. The mean follow-up period was 9.5 ± 2.9 years. The average age at surgery was 10.3 ± 3.9 years. The average preoperative scoliosis curve was 61.3 ± 13.8°, and the average preoperative kyphosis curve was 39.8 ± 19.7°. The average postoperative scoliosis and kyphosis curves were 29.7 ± 10.7° and 21.0 ± 13.5°, respectively. The most recent follow-up scoliosis and kyphosis curves were 43.4 ± 17.3° and 29.4 ± 18.9°, respectively. There was no significant difference in the correction angle (either coronal or sagittal), and there was no significant difference in the loss of sagittal correction between the pedicle screw construct group and the hybrid construct group. However, the patients who received pedicle screw constructs had significantly less loss of coronal correction (P < .05). Two patients with posterior instrumentation, one with an all-hook construct and the other with a hybrid construct, required surgical revision because of progression of deformity. It is difficult to intraoperatively correct dystrophic deformity and to maintain this correction after surgery. Combined anterior release/fusion and

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu Hongtao; Shin, Ji Hoon, E-mail: jhshin@amc.seoul.kr; Hwang, Jae-Yeon

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.

Joint kinematics of surgeons during lumbar pedicle screw placement.

PubMed

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

2016-12-01

A surgical robot for spine surgery has recently been developed. The objective is to assess the joint kinematics of the surgeon during spine surgery. We enrolled 18 spine surgeons, who each performed pedicle screw placement, and used an optoelectronic motion analysis system. Using three-dimensional (3D) motion images, distance changes in five joints and angle changes in six joints were calculated during surgery. Distance fluctuations increased gradually from the proximal to the distal joint. Angle fluctuations were largest at the distal point but did not gradually increase, and the elbow showed the second largest fluctuation. Changes along the X axis were larger than those of the Y and Z axes. The distances gradually increased from proximal portions of the body to the hand. In angle changes, the elbow was most dynamic during pedicle screw placement. The surgeons' whole joints carry out a harmonic role during lumbar pedicle screw placement. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Percutaneous pedicle screw placement under single dimensional fluoroscopy with a designed pedicle finder-a technical note and case series.

PubMed

Tsuang, Fon-Yih; Chen, Chia-Hsien; Kuo, Yi-Jie; Tseng, Wei-Lung; Chen, Yuan-Shen; Lin, Chin-Jung; Liao, Chun-Jen; Lin, Feng-Huei; Chiang, Chang-Jung

2017-09-01

Minimally invasive spine surgery has become increasingly popular in clinical practice, and it offers patients the potential benefits of reduced blood loss, wound pain, and infection risk, and it also diminishes the loss of working time and length of hospital stay. However, surgeons require more intraoperative fluoroscopy and ionizing radiation exposure during minimally invasive spine surgery for localization, especially for guidance in instrumentation placement. In addition, computer navigation is not accessible in some facility-limited institutions. This study aimed to demonstrate a method for percutaneous screws placement using only the anterior-posterior (AP) trajectory of intraoperative fluoroscopy. A technical report (a retrospective and prospective case series) was carried out. Patients who received posterior fixation with percutaneous pedicle screws for thoracolumbar degenerative disease or trauma comprised the patient sample. We retrospectively reviewed the charts of consecutive 670 patients who received 4,072 pedicle screws between December 2010 and August 2015. Another case series study was conducted prospectively in three additional hospitals, and 88 consecutive patients with 413 pedicle screws were enrolled from February 2014 to July 2016. The fluoroscopy shot number and radiation dose were recorded. In the prospective study, 78 patients with 371 screws received computed tomography at 3 months postoperatively to evaluate the fusion condition and screw positions. In the retrospective series, the placement of a percutaneous screw required 5.1 shots (2-14, standard deviation [SD]=2.366) of AP fluoroscopy. One screw was revised because of a medialwall breach of the pedicle. In the prospective series, 5.8 shots (2-16, SD=2.669) were required forone percutaneous pedicle screw placement. There were two screws with a Grade 1 breach (8.6%), both at the lateral wall of the pedicle, out of 23 screws placed at the thoracic spine at T9-T12. Forthe lumbar and sacral

Preliminary application of a multi-level 3D printing drill guide template for pedicle screw placement in severe and rigid scoliosis.

PubMed

Liu, Kun; Zhang, Qiang; Li, Xin; Zhao, Changsong; Quan, Xuemin; Zhao, Rugang; Chen, Zongfeng; Li, Yansheng

2017-06-01

Accurate implantation of pedicle screw in spinal deformity correction surgeries is always challenging. We have developed a method of pedicle screw placement in severe and rigid scoliosis with a multi-level 3D printing drill guide template. From November 2011 to March 2015, ten patients (4 males and 6 females) with severe and rigid scoliosis (Cobb angle >70° and flexibility <30%)were included. Multi-level template was designed and manufactured according to the part (two or three levels) of the most severe deformity. The drill template was then placed on the corresponding vertebral surface. Then, pedicle screws were carefully inserted along the trajectories. The other screws were placed in free hand. After surgery, the positions of the pedicle screws were evaluated by CT scan and graded for validation. 48 screws were implanted using templates, other 104 screws in free hand, and the accuracies were 93.8 and 78.8%, respectively, with significant difference. The deformity correction ratio was 67.1 and 41.2% in coronal and sagittal plane post-operatively, respectively. The average operation time was 234.0 ± 34.1 min, and average blood loss was 557 ± 67.4 ml. With the application of multi-level template, the incidence of cortex perforation in severe and rigid scoliosis decreased and this technology is, therefore, potentially applicable in clinical practice.

Pedicle screw cement augmentation. A mechanical pullout study on different cement augmentation techniques.

PubMed

Costa, Francesco; Ortolina, Alessandro; Galbusera, Fabio; Cardia, Andrea; Sala, Giuseppe; Ronchi, Franco; Uccelli, Carlo; Grosso, Rossella; Fornari, Maurizio

2016-02-01

Pedicle screws with polymethyl methacrylate (PMMA) cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques remains unknown. This study aimed to determine the difference in pullout strength between different cement augmentation techniques. Uniform synthetic bones simulating severe osteoporosis were used to provide a platform for each augmentation technique. In all cases a polyaxial screw and acrylic cement (PMMA) at medium viscosity were used. Five groups were analyzed: I) only screw without PMMA (control group); II) retrograde cement pre-filling of the tapped area; III) cannulated and fenestrate screw with cement injection through perforation; IV) injection using a standard trocar of PMMA (vertebroplasty) and retrograde pre-filling of the tapped area; V) injection through a fenestrated trocar and retrograde pre-filling of the tapped area. Standard X-rays were taken in order to visualize cement distribution in each group. Pedicle screws at full insertion were then tested for axial pullout failure using a mechanical testing machine. A total of 30 screws were tested. The results of pullout analysis revealed better results of all groups with respect to the control group. In particular the statistical analysis showed a difference of Group V (p = 0.001) with respect to all other groups. These results confirm that the cement augmentation grants better results in pullout axial forces. Moreover they suggest better load resistance to axial forces when the distribution of the PMMA is along all the screw combining fenestration and pre-filling augmentation technique. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Pedicle screw fixation in spinal disorders: a European view.

PubMed

Boos, N; Webb, J K

1997-01-01

Continuing controversy over the use of pedicular fixation in the United States is promoted by the lack of governmental approval for the marketing of these devices due to safety and efficacy concerns. These implants have meanwhile become an invaluable part of spinal instrumentation in Europe. With regard to the North American view, there is a lack of comprehensive reviews that consider the historical evolution of pedicle screw systems, the rationales for their application, and the clinical outcome from a European perspective. This literature review suggests that pedicular fixation is a relatively safe procedure and is not associated with a significantly higher complication risk than non-pedicular instrumentation. Pedicle screw fixation provides short, rigid segmental stabilization that allows preservation of motion segments and stabilization of the spine in the absence of intact posterior elements, which is not possible with non-pedicular instrumentation. Fusion rates and clinical outcome in the treatment of thoracolumbar fractures appear to be superior to that achieved using other forms of treatment. For the correction of spinal deformity (i.e., scoliosis, kyphosis, spondylolisthesis, tumor), pedicular fixation provides the theoretical benefit of rigid segmental fixation and of facilitated deformity correction by a posterior approach, but the clinical relevance so far remains unknown. In low-back pain disorders, a literature analysis of 5,600 cases of lumbar fusion with different techniques reveals a trend that pedicle screw fixation enhances the fusion rate but not clinical outcome. The most striking finding in the literature is the large range in the radiological and clinical results. For every single fusion technique poor and excellent results have been described. This review argues that European spine surgeons should begin to back up the evident benefits of pedicle screw systems for specific spinal disorders by controlled prospective clinical trials. This may

Inter- and intra-observer reliability of measurement of pedicle screw breach assessed by postoperative CT scans.

PubMed

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

2014-01-01

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. 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. 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. 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.

Radiographic and Clinical Outcomes of Robot-Assisted Posterior Pedicle Screw Fixation: Two-Year Results from a Randomized Controlled Trial.

PubMed

Park, Sang Min; Kim, Ho Joong; Lee, Se Yeon; Chang, Bong Soon; Lee, Choon Ki; Yeom, Jin S

2018-05-01

We prospectively assessed the early radiographic and clinical outcomes (minimum follow-up of 2 years) of robot-assisted pedicle screw fixation (Robot-PSF) and conventional freehand pedicle screw fixation (Conv-PSF). Patients were randomly assigned to Robot-PSF (37 patients) or Conv-PSF (41 patients) for posterior interbody fusion surgery. The Robot-PSF group underwent minimally invasive pedicle screw fixation using a pre-planned robot-guided screw trajectory. The Conv-PSF underwent screw fixation using the freehand technique. Radiographic adjacent segment degeneration (ASD) was measured on plain radiographs, and clinical outcomes were measured using visual analogue scale (VAS) and Oswestry disability index (ODI) scores regularly after surgery. The two groups had similar values for radiographic ASD, including University California at Los Angeles grade, vertebral translation, angular motion, and loss of disc height (p=0.320). At final follow-up, both groups had experienced significant improvements in back VAS, leg VAS, and ODI scores after surgery (p<0.001), although inter-group differences were not significant for back VAS (p=0.876), leg VAS (p=0.429), and ODI scores (p=0.952). In the Conv-PSF group, revision surgery was required for two of the 25 patients (8%), compared to no patients in the Robot-PSF group. There were no significant differences in radiographic ASD and clinical outcomes between Robot-PSF and Conv-PSF. Thus, the advantages of robot-assisted surgery (accurate pedicle screw insertion and minimal facet joint violation) do not appear to be clinically significant. © Copyright: Yonsei University College of Medicine 2018.

Accurate and Simple Screw Insertion Procedure With Patient-Specific Screw Guide Templates for Posterior C1-C2 Fixation.

PubMed

Sugawara, Taku; Higashiyama, Naoki; Kaneyama, Shuichi; Sumi, Masatoshi

2017-03-15

Prospective clinical trial of the screw insertion method for posterior C1-C2 fixation utilizing the patient-specific screw guide template technique. To evaluate the efficacy of this method for insertion of C1 lateral mass screws (LMS), C2 pedicle screws (PS), and C2 laminar screws (LS). Posterior C1LMS and C2PS fixation, also known as the Goel-Harms method, can achieve immediate rigid fixation and high fusion rate, but the screw insertion carries the risk of injury to neuronal and vascular structures. Dissection of venous plexus and C2 nerve root to confirm the insertion point of the C1LMS may also cause problems. We have developed an intraoperative screw guiding method using patient-specific laminar templates. Preoperative bone images of computed tomography (CT) were analyzed using three-dimensional (3D)/multiplanar imaging software to plan the trajectories of the screws. Plastic templates with screw guiding structures were created for each lamina using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Surgery was performed using this patient-specific screw guide template system, and placement of the screws was postoperatively evaluated using CT. Twelve patients with C1-C2 instability were treated with a total of 48 screws (24 C1LMS, 20 C2PS, 4 C2LS). Intraoperatively, each template was found to exactly fit and lock on the lamina and screw insertion was completed successfully without dissection of the venous plexus and C2 nerve root. Postoperative CT showed no cortical violation by the screws, and mean deviation of the screws from the planned trajectories was 0.70 ± 0.42 mm. The multistep, patient-specific screw guide template system is useful for intraoperative screw navigation in posterior C1-C2 fixation. This simple and economical method can improve the accuracy of screw insertion, and reduce operation time and

Mechanical and histological analysis of bone-pedicle screw interface in vivo: titanium versus stainless steel.

PubMed

Sun, C; Huang, G; Christensen, F B; Dalstra, M; Overgaard, S; Bünger, C

1999-05-01

To investigate the differences in bone interface between titanium and stainless steel pedicle screws in the lumbar spine. Eighteen adult mini-pigs that underwent total laminectomy, posterolateral spinal fusion (L4-L5) were randomly selected to receive stainless steel (9) or titanium pedicle screw devices (9). In both groups, the devices were CCD (Sofamore Danek) type with the same size and shape. The postoperative observation time was 3 months. Screws from L4 were harvested along their long axis of pedicle for histomorphometric study. Bone-screw interface and bone volume from thread were examined using linear intercept techniques. Mechanical testing (torsional test and pull-out test) was performed on the screws from L5. The titanium screw group had a significantly higher maximum torque (P < 0.05) and angle related stiffness (P < 0.05) measured by torsional test. In the pull-out tests, no differences were found between the two groups in relation to the maximum load, stiffness and energy to failure. Direct bone contact with the screw in percentage was 29.4% for stainless steel and 43.8% for titanium (P < 0.05). No differences in the bone purchase between the vertebral body part and pedicle part were found. Pedicle screws made of titanium have a better bone-screw interface binding than screws made of stainless steel. Torsional tests are more informative for bone-screw interface study. Pull-out tests seem less valuable when comparing bone purchase of screws made from different materials.

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

Perfusion pressure of a new cannulating fenestrated pedicle screw during cement augmentation.

PubMed

Wang, Zhirong; Zhang, Wen; Xu, Hao; Lu, Aiqing; Yang, Huilin; Luo, Zong-Ping

2018-06-18

Cannulating fenestrated pedicle screws are effective for fixating osteoporotic vertebrae. However, a major limitation is the excessive pressure required to inject a sufficient amount of cement into the vertebral body through the narrow hole of a pedicle screw. We have recently proposed a new cannulating fenestrated pedicle screw with a large hole diameter and a matched inner pin for screw-strength maintenance. Our purpose was to determine whether the new screw can significantly reduce bone-cement perfusion pressure during cement augmentation, METHODS: Two different methods were used to examine perfusion pressure. Hagen-Poisseuille's flow model in a tube was used to calculate pressure drop in the bone-cement channel. Experimentally, both Newtonian silicone oil and bone-cement (polymethyl methacrylate) were tested using a cement pusher through the cannulating screw at a constant rate of 2 ml/min. The internal hollow portion of the screw was the bottleneck of the perfusion, and the new design significantly reduced the perfusion pressure. Specifically, perfusion pressure dropped by 59% (P < 0.05) when diameter size was doubled. The new design effectively improved the application of bone-cement augmentation with the ease of bone-cement perfusion, thereby enhancing operational safety. Copyright © 2018. Published by Elsevier Ltd.

The effect of screw tunnels on the biomechanical stability of vertebral body after pedicle screws removal: a finite element analysis.

PubMed

Liu, Jia-Ming; Zhang, Yu; Zhou, Yang; Chen, Xuan-Yin; Huang, Shan-Hu; Hua, Zi-Kai; Liu, Zhi-Li

2017-06-01

Posterior reduction and pedicle screw fixation is a widely used procedure for thoracic and lumbar vertebrae fractures. Usually, the pedicle screws would be removed after the fracture healing and screw tunnels would be left. The aim of this study is to evaluate the effect of screw tunnels on the biomechanical stability of the lumbar vertebral body after pedicle screws removal by finite element analysis (FEA). First, the CT values of the screw tunnels wall in the fractured vertebral bodies were measured in patients whose pedicle screws were removed, and they were then compared with the values of vertebral cortical bone. Second, an adult patient was included and the CT images of the lumbar spine were harvested. Three dimensional finite element models of the L1 vertebra with unilateral or bilateral screw tunnels were created based on the CT images. Different compressive loads were vertically acted on the models. The maximum loads which the models sustained and the distribution of the force in the different parts of the models were recorded and compared with each other. The CT values of the tunnels wall and vertebral cortical bone were 387.126±62.342 and 399.204±53.612, which were not statistically different (P=0.149). The models of three dimensional tetrahedral mesh finite element of normal lumbar 1 vertebra were established with good geometric similarity and realistic appearance. After given the compressive loads, the cortical bone was the first one to reach its ultimate stress. The maximum loads which the bilateral screw tunnels model, unilateral screw tunnel model, and normal vertebral model can sustain were 3.97 Mpa, 3.83 Mpa, and 3.78 Mpa, respectively. For the diameter of the screw tunnels, the model with a diameter of 6.5 mm could sustain the largest load. In addition, the stress distributing on the outside of the cortical bone gradually decreased as the thickness of the tunnel wall increased. Based on the FEA, pedicle screw tunnels would not decrease the

Thoracic pedicle classification determined by inner cortical width of pedicles on computed tomography images: its clinical significance for posterior vertebral column resection to treat rigid and severe spinal deformities-a retrospective review of cases.

PubMed

Zhang, Ying; Xie, Jingming; Wang, Yingsong; Bi, Ni; Zhao, Zhi; Li, Tao

2014-08-13

Posterior vertebral column resection (PVCR) is an effective alternative for treating rigid and severe spinal deformities. Accurate placement of pedicle screws, especially apically, is crucial. As morphologic evaluations of thoracic pedicles have not provided objective criteria, we propose a thoracic pedicle classification for treating rigid and severe spinal deformities. A consecutive series of 56 patients with severe and rigid spinal deformities who underwent PVCR at a single institution were reviewed retrospectively. Altogether, 1098 screws were inserted into thoracic pedicles at T2-T12. Based on the inner cortical width of the thoracic pedicles, the patients were divided into four groups: group 1 (0-1.0 mm), group 2 (1.1-2.0 mm), group 3 (2.1-3.0 mm), group 4 (≥3.1 mm). The proportion of screws accurately inserted in thoracic pedicles for each group was calculated. Statistical analysis was also performed regarding types of thoracic pedicles classified by Lenke et al. (SPINE 35:1836-1842, 2010) using a morphological method. There were statistically significant differences in the rates of screws inserted in thoracic pedicles between the groups (P < 0.008) except groups 3 and 4 (P > 0.008), which were then combined. The accuracies for the three new groups were 35.05%, 65.34%, and 88.32%, respectively, with statistically significant differences between the groups (P < 0.017). Rates of screws inserted in thoracic pedicles classified by Lenke et al. (SPINE 35:1836-1842, 2010) were 82.31%, 83.40%, 80.00%, and 30.28% for types A, B, C, and D, respectively. There was no statistically significant difference (P > 0.008) between these types except between type D and the other three types (P < 0.008). The inner cortical width of thoracic pedicles is the sole factor crucial for accurate placement of thoracic pedicle screws. We propose a computed tomography-based classification of the pedicle's inner cortical width: type I thoracic pedicle: absent channel, inner cortical

Comparison of clinical results between novel percutaneous pedicle screw and traditional open pedicle screw fixation for thoracolumbar fractures without neurological deficit.

PubMed

Yang, Ming; Zhao, Qinpeng; Hao, Dingjun; Chang, Zhen; Liu, Shichang; Yin, Xinhua

2018-06-16

To compare the efficacy and safety of novel percutaneous minimally invasive pedicle screw fixation and traditional open surgery for thoracolumbar fractures without neurological deficit. Sixty adult patients with single thoracolumbar fracture between June 2014 and June 2016 were recruited in this study, randomly divided into open fixation group (group A) or minimally invasive percutaneous fixation group (group B). Clinical and surgical evaluation including surgery time, blood losses, radiation times, hospital stay, and complication were performed. The two groups of patients with pre-operative and last follow-up anterior height ratio of fracture vertebral, Cobb angle of fracture vertebral, and VAS score of back pain were compared. All patients completed valid follow-ups, with an average time period of 15.4 months (12-26 months). Group B achieved much better results in time of operation, intra-operative blood loss, and length of stay than group A (P < 0.05). Group A was significantly better than group B in the times of radiation (P < 0.05). The VAS score was significantly lower in group B than in group A at three days after the operation (P < 0.05). There were no significant differences between the two groups in the anterior height ratio of fracture vertebral, Cobb angle, and VAS score in the last follow-up (P > 0.05). No injured nerve or other severe complications occurred in both groups; one of the patients from group A had back and loin pain lasting for about one month, which resolved after analgesia and functional training. There was no significant difference between the two groups in incidence of complications. Novel percutaneous pedicle screws with angle reset function can achieve the same effect as traditional open pedicle screw fixation in the treatment of thoracolumbar fractures without nerve injuries. Percutaneous minimally invasive pedicle screw fixation has the characteristics of shorter operative time, less bleeding, and less pain, but

Systematic review of cortical bone trajectory versus pedicle screw techniques for lumbosacral spine fusion.

PubMed

Phan, Kevin; Ramachandran, Vignesh; Tran, Tommy M; Shah, Kevin P; Fadhil, Matthew; Lackey, Alan; Chang, Nicholas; Wu, Ai-Min; Mobbs, Ralph J

2017-12-01

Fusion of the lumbosacral spine is a common surgical procedure to address a range of spinal pathologies. Fixation in lumbar fusion has traditionally been performed using pedicle screw (PS) augmentation. However, an alternative method of screw insertion via cortical bone trajectory (CBT) has been advocated as a less invasive approach which improves initial fixation and reduces neurovascular injury. There is a paucity of robust clinical evidence to support these claims, particularly in comparison to traditional pedicle screws. This study aims to review the available evidence to assess the merits of the CBT approach. Six electronic databases were searched for original published studies which compared CBT with traditional PS and their findings reviewed. Nine comparative studies were identified through a comprehensive literature search. Studies were classified as retrospective cohort, prospective cohort or case control studies with medium quality as assessed by the GRADE criteria. The available literature is not cohesive regarding outcomes and complications of CBT versus PT procedures. Most studies found no difference in operative time, but reported less blood loss during CBT. Radiological outcomes show no difference in slippage at one year although CBT is associated with greater bone-density compared to PT. Results for post-operative pain are inconclusive.

Accuracy of percutaneous pedicle screws for thoracic and lumbar spine fractures compared with open technique.

PubMed

Paredes, Igor; Panero, Irene; Cepeda, Santiago; Castaño-Leon, Ana M; Jimenez-Roldan, Luis; Perez-Nuñez, Ángel; Alén, Jose A; Lagares, Alfonso

2018-06-14

This study aimed to compare the accuracy of screw placement between open pedicle screw fixation and percutaneous pedicle screw fixation (MIS) for the treatment of thoracolumbar spine fractures (TSF). Forty-nine patients with acute TSF who were treated with transpedicular screw fixation from January 2013 to December 2016 were retrospectively reviewed. The patients were divided into Open and MIS groups. Laminectomy was performed in either group if needed. The accuracy of the screw placement, the evolution of the Cobb sagital angle postoperatively and at 12-month follow up and the neurological status were recorded. AO type of fracture and TLICS score were also recorded. Mean age was 42 years old. Mean TLICS score was 6,29 and 5,96 for open and MIS groups respectively. Twenty five MIS and 24 open surgeries were performed, and 350 (175 in each group) screws were inserted (7,14 per patient). Twenty-four and 13 screws were considered ̈out ̈ in the open and MIS groups respectively (Odds ratio 1,98. 0,97-4,03 p=0,056). The Cobb sagittal angle went from 13,3o to 4,5o and from 14,9o to 8,2o in the Open and MIS groups respectively (both p<0,0001). Loss of correction at 12-month follow up was 3,2o and 4,2o for the open and MIS groups respectively. No neurological worsening was observed. For the treatment of acute thoracolumbar fractures, the MIS technique seems to achieve similar results to the open technique in relation to neurological improvement and deformity correction, while placing the screws more accurately.

In vitro biomechanical comparison of pedicle screws, sublaminar hooks, and sublaminar cables.

PubMed

Hitchon, Patrick W; Brenton, Matthew D; Black, Andrew G; From, Aaron; Harrod, Jeremy S; Barry, Christopher; Serhan, Hassan; Torner, James C

2003-07-01

Three types of posterior thoracolumbar implants are in use today: pedicle screws, sublaminar titaniumcables, and sublaminar hooks. The authors conducted a biomechanical comparison of these three implants in human cadaveric spines. Spine specimens (T5-12) were harvested, radiographically assessed for fractures or metastases, and their bone mineral density (BMD) was measured. Individual vertebrae were disarticulated and fitted with either pedicle screws, sublaminar cables, or bilateral claw hooks. The longitudinal component of each construct consisted of bilateral 10-cm rods connected with two cross-connectors. The vertebral body was embedded in cement, and the rods were affixed to a ball-and-socket apparatus for the application of a distraction force. The authors analyzed 1) 20 vertebrae implanted with screws; 2) 20 with hooks, and 3) 20 with cables. The maximum pullout (MPO) forces prior to failure (mean +/- standard deviation) for the screw, hook, and cable implants were 972 +/- 330, 802 +/- 356, and 654 +/- 248 N, respectively (p = 0.0375). Cables allowed significantly greater displacement (6.80 +/- 3.95 mm) prior to reaching the MPO force than hooks (3.73 +/- 1.42 mm) and screws (4.42 +/- 2.15 mm [p = 0.0108]). Eleven screw-implanted vertebrae failed because of screw pullout. All hook-and-cable-implanted vertebrae failed because of pedicle, middle column, or laminar fracture. These findings suggest that screws possess the greatest pullout strength of the three fixation systems. Sublaminar cables are the least rigid of the three. When screw failure occurred, the mechanism was generally screw back-out, without vertebral fractures.

Correction Capability in the 3 Anatomic Planes of Different Pedicle Screw Designs in Scoliosis Instrumentation.

PubMed

Wang, Xiaoyu; Aubin, Carl-Eric; Coleman, John; Rawlinson, Jeremy

2017-05-01

Computer simulations to compare the correction capabilities of different pedicle screws in adolescent idiopathic scoliosis (AIS) instrumentations. To compare the correction and resulting bone-screw forces associated with different pedicle screws in scoliosis instrumentations. Pedicle screw fixation is widely used in surgical instrumentation for spinal deformity treatment. Screw design, correction philosophies, and surgical techniques are constantly evolving to achieve better control of the vertebrae and correction of the spinal deformity. Yet, there remains a lack of biomechanical studies that quantify the effects and advantages of different screw designs in terms of correction kinematics. The correction capabilities of fixed-angle, multiaxial, uniaxial, and saddle axial screws were kinematically analyzed, simulated, and compared. These simulations were based on the screw patterns and correction techniques proposed by 2 experienced surgeons for 2 AIS cases. Additional instrumentations were assessed to compare the correction and resulting bone-screw forces associated with each type of screw. The fixed-angle, uniaxial and saddle axial screws had similar kinematic behavior and performed better than multiaxial screws in the coronal and transverse planes (8% and 30% greater simulated corrections, respectively). Uniaxial and multiaxial screws were less effective than fixed-angle and saddle axial screws in transmitting compression/distraction to the anterior spine because of their sagittal plane mobility between the screw head and shank. Only the saddle axial screws allow vertebra angle in the sagittal plane to be independently adjusted. Pedicle screws of different designs performed differently for deformity corrections or for compensating screw placement variations in different anatomic planes. For a given AIS case, screw types should be determined based on the particular instrumentation objectives, the deformity's stiffness and characteristics so as to make the best of

The Biomechanical Properties of Pedicle Screw Fixation Combined With Trajectory Bone Cement Augmentation in Osteoporotic Vertebrae.

PubMed

Fan, Haitao T; Zhang, Renjie J; Shen, Cailiang L; Dong, Fulong L; Li, Yong; Song, Peiwen W; Gong, Chen; Wang, Yijin J

2016-03-01

The biomechanics of pedicle screw fixation combined with trajectory cement augmentation with various filling volumes were measured by pull-out, periodic antibending, and compression fatigue tests. To investigate the biomechanical properties of the pedicle screw fixation combined with trajectory bone cement (polymethylmethacrylate) augmentation in osteoporotic vertebrae and to explore the optimum filling volume of the bone cement. Pedicle screw fixation is considered to be the most effective posterior fixation method. The decrease of the bone mineral density apparently increases the fixation failure risk caused by screw loosening and displacement. Trajectory bone cement augmentation has been confirmed to be an effective method to increase the bone intensity and could markedly increase the stability of the fixation interface. Sixteen elderly cadaveric 1-5 lumbar vertebral specimens were diagnosed with osteoporosis. The left and right vertebral pedicles were alternatively randomized for treatment in all groups, with the contralateral pedicles as control. The study groups included: group A (pedicle screw fixation with full trajectory bone cement augmentation), group B (75% filling), group C (50% filling), and group D (25% filling). Finally, the bone cement leakage and dispersion were assessed and the mechanical testing was conducted. The bone cement was well dispersed around the pedicle screw. The augmented bone intensity, pull-out strength, periodic loading times, and compression fatigue performance were markedly higher than those of the control groups. With the increase in trajectory bone cement, the leakage was also increased (P<0.05). The pull-out strength of the pedicle screw was increased with an increase in bone mineral density and trajectory bone cement. It peaked at 75% filling, with the largest power consumption. The optimal filling volume of the bone cement was 75% of the trajectory volume (about 1.03 mL). The use of excessive bone cement did not increase

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

[Atlanto-axial pedicle screw fixation through posterior approach for treatment of atlanto-axial joint instability].

PubMed

Zuo, Chun-Guang; Liu, Xia-Jun; Wang, Xin-Hu; Wang, Jian-shun

2013-01-01

To discuss the therapeutic effects of the atlantoaxial pedicle screw system fixation in treatment of atlantoaxial instability. From June 2003 to March 2010, 32 patients with atlantoaxial instability were treated by atlantoaxial pedicle screw system fixation, included 21 males and 11 females wiht an average age of 42.5 years old ranging from 28 to 66 years. Among them, 18 cases were odontoid process fractures, 7 were congenital dissociate odontoid process, 4 were Jefferson fracture combined with odontoid fracture, 3 were rheumatic arthritis causing atlantoaxial instability. All patients suffered from the atlantoaxial subluxation and atlantoaxial instability. The JOA score ranged from 4 to 14 (means 9.1 +/- 0.3) before operation. The patients had some image examination including the X-ray of cervical vertebrae (include of dynamic position film), spiral CT 3D reconstruction and/or MRI. The position of pedicle screw system implantation,the angle of pedicle screw system implantation and screw length were measured. Operating skull traction. Operation undewent general anesthesia, implanted the pedicle screw, reduction and bone fusion under direct vision. The bone was fixated between posterior arch of atlas and lamina of axis by the lateral combination bended to posterior. One hundred and twenty-eight atlantoaxial pedicle screws were implanted in 32 patients. No patient had the injure of spinal cord, nerve root and vertebral artery. All patients were followed-up from 6 to 48 months (averaged 16 months). After operation, the JOA score ranged from 11 to 17 (averaged 15.9 +/- 0.2), improvement rate was 86.1%. The fracture of odontoid process were healing completely. All fusion bone were combinated. The internal fixation wasn't loosening and breaking. The atlantoaxial pedicle screw system fixation was effective method to treat atlantoaxial instability. The method had many advantages, such as provide rigid and short segment fixation, safe and simple, high fusion rate. The

Descending aortic injury by a thoracic pedicle screw during posterior reconstructive surgery: a case report.

PubMed

Watanabe, Kei; Yamazaki, Akiyoshi; Hirano, Toru; Izumi, Tomohiro; Sano, Atsuki; Morita, Osamu; Kikuchi, Ren; Ito, Takui

2010-09-15

Case report. To describe an iatrogenic aortic injury by pedicle screw instrumentation during posterior reconstructive surgery of spinal deformity. Iatrogenic major vascular injuries during anterior instrumentation procedures have been reported by several authors, but there have been few reports regarding iatrogenic major vascular injuries during posterior instrumentation procedures. A 57-year-old woman with thoracolumbar kyphosis due to osteoporotic T12 vertebral fracture underwent posterior correction and fusion (T10-L2), using segmental pedicle screw construct concomitant with T12 pedicle subtraction osteotomy. Postoperative routine plain radiographs and computed tomography myelography demonstrated a misplaced left T10 pedicle screw, which was in contact with the posteromedial aspect of the thoracic aorta, and suspected penetration of the aortic wall. The patient underwent removal of the pedicle screw, and repair of the penetrated aortic wall through a simultaneous anterior-posterior approach. The patient tolerated the procedure well without neurologic sequelae, and was discharged several days after removal of a left tube thoracostomy. Plain radiographs demonstrated solid fusion at the osteotomy site and no loosening of hardware. Preoperative neurologic symptoms improved completely at 18-months follow-up. Use of pedicle screw instrumentation has the potential to cause major vascular injury during posterior spinal surgery, and measures to prevent this complication must be taken. Timely diagnosis and treatment are essential to prevent both early and delayed complications and death.

Safety of lumbar spine radiofrequency procedures in the presence of posterior pedicle screws: technical report of a cadaver study.

PubMed

Gazelka, Halena M; Welch, Tasha L; Nassr, Ahmad; Lamer, Tim J

2015-05-01

To determine whether the thermal energy associated with lumbar spine radiofrequency neurotomy (RFN) performed near titanium and stainless steel pedicle screws is conducted to the pedicle screws or adjacent tissues, or both, thus introducing potential for thermal damage to those tissues. Cadaver study. Cadaver laboratory equipped with fluoroscopy, surgical spine implements, and radiofrequency generator. No live human subject; a fresh frozen (and thawed) cadaver torso was used for the study. Titanium and stainless steel pedicle screws were placed in the lumbar spine of a fresh frozen cadaver torso with real-time fluoroscopic guidance. Conventional RFN cannula placement was performed at the level of pedicle screws and a control (nonsurgically altered) lumbar level. Neurotomy was performed with conventional radiofrequency lesioning parameters. Temperatures were recorded at multiple sites through thermistor probes. Direct contact of the radiofrequency cannula with the pedicle screws during conventional RFN produced a substantial increase in temperature in the surrounding soft tissues. A small increase in temperature occurred at the same sites at the control level. Titanium and stainless steel pedicle screws are capable of sustaining large increases in temperature when the radiofrequency probe comes in contact with the screw. These results are suggestive that pedicle screws could serve as a possible source of tissue heating and thermal injury during RFN. Wiley Periodicals, Inc.

What is the learning curve for robotic-assisted pedicle screw placement in spine surgery?

PubMed

Hu, Xiaobang; Lieberman, Isador H

2014-06-01

Some early studies with robotic-assisted pedicle screw implantation have suggested these systems increase accuracy of screw placement. However, the relationship between the success rate of screw placement and the learning curve of this new technique has not been evaluated. We determined whether, as a function of surgeon experience, (1) the success rate of robotic-assisted pedicle screw placement improved, (2) the frequency of conversion from robotic to manual screw placement decreased, and (3) the frequency of malpositioned screws decreased. Between June 2010 and August 2012, the senior surgeon (IHL) performed 174 posterior spinal procedures using pedicle screws, 162 of which were attempted with robotic assistance. The use of the robotic system was aborted in 12 of the 162 procedures due to technical issues (registration failure, software crash, etc). The robotic system was successfully used in the remaining 150 procedures. These were the first procedures performed with the robot by the senior surgeon, and in this study, we divided the early learning curve into five groups: Group 1 (Patients 1-30), Group 2 (Patients 31-60), Group 3 (Patients 61-90), Group 4 (Patients 91-120), and Group 5 (Patients 121-150). One hundred twelve patients (75%) had spinal deformity and 80 patients (53%) had previous spine surgery. The accuracy of screw placement in the groups was assessed based on intraoperative biplanar fluoroscopy and postoperative radiographs. The results from these five groups were compared to determine the effect on the learning curve. The numbers of attempted pedicle screw placements were 359, 312, 349, 359, and 320 in Groups 1 to 5, respectively. The rates of successfully placed screws using robotic guidance were 82%, 93%, 91%, 95%, and 93% in Groups 1 to 5. The rates of screws converted to manual placement were 17%, 7%, 8%, 4%, and 7%. Of the robotically placed screws, the screw malposition rates were 0.8%, 0.3%, 1.4%, 0.8%, and 0%. The rate of successfully

Alternative radiation-free registration technique for image-guided pedicle screw placement in deformed cervico-thoracic segments.

PubMed

Kantelhardt, Sven R; Neulen, Axel; Keric, Naureen; Gutenberg, Angelika; Conrad, Jens; Giese, Alf

2017-10-01

Image-guided pedicle screw placement in the cervico-thoracic region is a commonly applied technique. In some patients with deformed cervico-thoracic segments, conventional or 3D fluoroscopy based registration of image-guidance might be difficult or impossible because of the anatomic/pathological conditions. Landmark based registration has been used as an alternative, mostly using separate registration of each vertebra. We here investigated a routine for landmark based registration of rigid spinal segments as single objects, using cranial image-guidance software. Landmark based registration of image-guidance was performed using cranial navigation software. After surgical exposure of the spinous processes, lamina and facet joints and fixation of a reference marker array, up to 26 predefined landmarks were acquired using a pointer. All pedicle screws were implanted using image guidance alone. Following image-guided screw placement all patients underwent postoperative CT scanning. Screw positions as well as intraoperative and clinical parameters were retrospectively analyzed. Thirteen patients received 73 pedicle screws at levels C6 to Th8. Registration of spinal segments, using the cranial image-guidance succeeded in all cases. Pedicle perforations were observed in 11.0%, severe perforations of >2 mm occurred in 5.4%. One patient developed a transient C8 syndrome and had to be revised for deviation of the C7 pedicle screw. No other pedicle screw-related complications were observed. In selected patients suffering from pathologies of the cervico-thoracic region, which impair intraoperative fluoroscopy or 3D C-arm imaging, landmark based registration of image-guidance using cranial software is a feasible, radiation-saving and a safe alternative.

Pedicle screw-rod fixation: a feasible treatment for dogs with severe degenerative lumbosacral stenosis.

PubMed

Tellegen, Anna R; Willems, Nicole; Tryfonidou, Marianna A; Meij, Björn P

2015-12-07

Degenerative lumbosacral stenosis is a common problem in large breed dogs. For severe degenerative lumbosacral stenosis, conservative treatment is often not effective and surgical intervention remains as the last treatment option. The objective of this retrospective study was to assess the middle to long term outcome of treatment of severe degenerative lumbosacral stenosis with pedicle screw-rod fixation with or without evidence of radiological discospondylitis. Twelve client-owned dogs with severe degenerative lumbosacral stenosis underwent pedicle screw-rod fixation of the lumbosacral junction. During long term follow-up, dogs were monitored by clinical evaluation, diagnostic imaging, force plate analysis, and by using questionnaires to owners. Clinical evaluation, force plate data, and responses to questionnaires completed by the owners showed resolution (n = 8) or improvement (n = 4) of clinical signs after pedicle screw-rod fixation in 12 dogs. There were no implant failures, however, no interbody vertebral bone fusion of the lumbosacral junction was observed in the follow-up period. Four dogs developed mild recurrent low back pain that could easily be controlled by pain medication and an altered exercise regime. Pedicle screw-rod fixation offers a surgical treatment option for large breed dogs with severe degenerative lumbosacral stenosis with or without evidence of radiological discospondylitis in which no other treatment is available. Pedicle screw-rod fixation alone does not result in interbody vertebral bone fusion between L7 and S1.

Effectiveness of the Thoracic Pedicle Screw Placement Using the Virtual Surgical Training System: A Cadaver Study.

PubMed

Hou, Yang; Lin, Yanping; Shi, Jiangang; Chen, Huajiang; Yuan, Wen

2018-03-14

The virtual simulation surgery has initially exhibited its promising potentials in neurosurgery training. To evaluate effectiveness of the Virtual Surgical Training System (VSTS) on novice residents placing thoracic pedicle screws in a cadaver study. A total of 10 inexperienced residents participated in this study and were randomly assigned to 2 groups. The group using VSTS to learn thoracic pedicle screw fixation was the simulation training (ST) group and the group receiving an introductory teaching session was the control group. Ten fresh adult spine specimens including 6 males and 4 females with a mean age of 58.5 yr (range: 33-72) were collected and randomly allocated to the 2 groups. After exposing anatomic structures of thoracic spine, the bilateral pedicle screw placement of T6-T12 was performed on each cadaver specimen. The postoperative computed tomography scan was performed on each spine specimen, and experienced observers independently reviewed the placement of the pedicle screws to assess the incidence of pedicle breach. The screw penetration rates of the ST group (7.14%) was significantly lower in comparison to the control group (30%, P < .05). Statistically significant difference in acceptable rates of screws also occurred between the ST (100%) and control (92.86%) group (P < .05). In addition, the average screw penetration distance in control group (2.37 mm ± 0.23 mm) was significantly greater than ST group (1.23 mm ± 0.56 mm, P < .05). The virtual reality surgical training of thoracic pedicle screw instrumentation effectively improves surgical performance of novice residents compared to those with traditional teaching method, and can help new beginners to master the surgical technique within shortest period of time.

3D printing-assisted preoperative plan of pedicle screw placement for middle-upper thoracic trauma: a cohort study.

PubMed

Xu, Wei; Zhang, Xuming; Ke, Tie; Cai, Hongru; Gao, Xiang

2017-08-11

This study aimed to evaluate the application of 3D printing in assisting preoperative plan of pedicle screw placement for treating middle-upper thoracic trauma. A preoperative plan was implemented in seven patients suffering from middle-upper thoracic (T3-T7) trauma between March 2013 and February 2016. In the 3D printing models, entry points of 56 pedicle screws (Magerl method) and 4 important parameters of the pedicle screws were measured, including optimal diameter (ϕ, mm), length (L, mm), inclined angle (α), head-tilting angle (+β), and tail-tilting angle (-β). In the surgery, bare-hands fixation of pedicle screws was performed using 3D printing models and the measured parameters as guidance. A total of seven patients were enrolled, including five men and two women, with the age of 21-62 years (mean age of 37.7 years). The position of the pedicle screw was evaluated postoperatively using a computerized tomography scan. Totally, 56 pedicle screws were placed, including 33 pieces of level 0, 18 pieces of level 1, 4 pieces of level 2 (pierced lateral wall), and 1 piece of level 3 (pierced lateral wall, no adverse consequences), with a fine rate of 91.0%. 3D printing technique is an intuitive and effective assistive technology to pedicle screw fixation for treating middle-upper thoracic vertebrae, which improve the accuracy of bare-hands screw placement and reduce empirical errors. The trial was approved by the Ethics Committee of the Fujian Provincial Hospital. It was registered on March 1st, 2013, and the registration number was K2013-03-001.

Virtual surgery simulation versus traditional approaches in training of residents in cervical pedicle screw placement.

PubMed

Hou, Yang; Shi, Jiangang; Lin, Yanping; Chen, Huajiang; Yuan, Wen

2018-06-01

The cervical screw placement is one of the most difficult procedures in spine surgery, which often needs a long period of repeated practices and could cause screw placement-related complications. We performed this cadaver study to investigate the effectiveness of virtual surgical training system (VSTS) on cervical pedicle screw instrumentation for residents. A total of ten novice residents were randomly assigned to two groups: the simulation training (ST) group (n = 5) and control group (n = 5). The ST group received a surgical training of cervical pedicle screw placement on VSTS and the control group was given an introductory teaching session before cadaver test. Ten fresh adult spine specimens including 6 males and 4 females were collected, and were randomly allocated to the two groups. The bilateral C3-C6 pedicle screw instrumentation was performed in the specimens of the two groups, respectively. After instrumentation, screw positions of the two groups were evaluated by image examinations. There was significantly statistical difference in screw penetration rates between the ST (10%) and control group (62.5%, P < 0.05). The acceptable rates of screws were 100 and 50% in the ST and control groups with significant difference between each other (P < 0.05). In addition, the average screw penetration distance in the ST group (1.12 ± 0.47 mm) was significantly lower than the control group (2.08 ± 0.39 mm, P < 0.05). This study demonstrated that the VSTS as an advanced training tool exhibited promising effects on improving performance of novice residents in cervical pedicle screw placement compared with the traditional teaching methods.

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

MIS Single-position Lateral and Oblique Lateral Lumbar Interbody Fusion and Bilateral Pedicle Screw Fixation: Feasibility and Perioperative Results.

PubMed

Blizzard, Daniel J; Thomas, J Alex

2018-03-15

Retrospective review of prospectively collected data of the first 72 consecutive patients treated with single-position one- or two-level lateral (LLIF) or oblique lateral interbody fusion (OLLIF) with bilateral percutaneous pedicle screw and rod fixation by a single spine surgeon. To evaluate the clinical feasibility, accuracy, and efficiency of a single-position technique for LLIF and OLLIF with bilateral pedicle screw and rod fixation. Minimally-invasive lateral interbody approaches are performed in the lateral decubitus position. Subsequent repositioning prone for bilateral pedicle screw and rod fixation requires significant time and resources and does not facilitate increased lumbar lordosis. The first 72 consecutive patients (300 screws) treated with single-position LLIF or OLLIF and bilateral pedicle screws by a single surgeon between December 2013 and August 2016 were included in the study. Screw accuracy and fusion were graded using computed tomography and several timing parameters were recorded including retractor, fluoroscopy, and screw placement time. Complications including reoperation, infection, and postoperative radicular pain and weakness were recorded. Average screw placement time was 5.9 min/screw (standard deviation, SD: 1.5 min; range: 3-9.5 min). Average total operative time (interbody cage and pedicle screw placement) was 87.9 minutes (SD: 25.1 min; range: 49-195 min). Average fluoroscopy time was 15.0 s/screw (SD: 4.7 s; range: 6-25 s). The pedicle screw breach rate was 5.1% with 10/13 breaches measured as < 2 mm in magnitude. Fusion rate at 6-months postoperative was 87.5%. Two (2.8%) patients underwent reoperation for malpositioned pedicle screws with subsequent resolution of symptoms. The single-position, all-lateral technique was found to be feasible with accuracy, fluoroscopy usage, and complication rates comparable with the published literature. This technique eliminates the time and staffing associated with

Incidence and risk factors for the misplacement of pedicle screws in scoliosis surgery assisted by O-arm navigation-analysis of a large series of one thousand, one hundred and forty five screws.

PubMed

Jin, Mengran; Liu, Zhen; Qiu, Yong; Yan, Huang; Han, Xiao; Zhu, Zezhang

2017-04-01

To assess the accuracy of O-arm-navigation-based pedicle screw placement in scoliosis surgery and identify the potential risk factors for the misplacement of pedicle screws. One hundred forty four scoliosis patients treated with O-arm-navigation-based pedicle screw instrumentation were enrolled, and 1145 pedicle screws implanted in the apical region of the curves were retrospectively reviewed for accuracy according to post-operative CT images. The potential risk factors and independent predictive factor(s) for the misplaced screws were identified statistically. The overall malpositioning rate of pedicle screw was 9.8%; 54.5% of which were misplaced laterally. Univariate and multivariate logistic regression analysis of clinical and surgical treatment variables indicated that patients with congenital scoliosis (CS) [OR: 1.489 (95% CI: 1.002-2.213; P = 0.035)] and neurofibromatosis type I (NF-1) [OR: 1.785 (95% CI: 1267-2.045; P = 0.026)], middle-thoracic spine [OR: 1.661 (95% CI: 1.107-2.481; P = 0.021)], the concave pedicles [OR: 1.527 (95% CI: 1.020-2.285; P = 0.019)], and the segments three levels away from the tracker [OR: 3.522 (95% CI: 2.357-5.263; P = 0.001)] were independently associated with pedicle screw misplacement. O-arm-assisted navigation does improve the accuracy and safety of pedicle screw placement in scoliosis surgery. However, unavoidable screw malpositioning remained, which occurred significantly more often in patients with CS and NF-1, in middle-thoracic spine, in the concave pedicles, and in the segments three levels away from the tracker.

Lumbar segmental artery pseudoaneurysm after L5 pedicle screw placement. A rare vascular complication.

PubMed

Álvarez Postigo, M; Pizones Arce, J; Izquierdo Núñez, E

Posterior lumbar screw fixation is a common surgical procedure nowadays. However, it can sometimes produce complications that can be devastating. One of the less common causes of major complication is the misplacement of a pedicle screw. This highlights the importance of being methodical when placing pedicle screws, and checking that the pathway has been created correctly and their placement. We present a case of a massive bleed after a pedicular screw placement during lumbar canal stenosis surgery. Screw malposition led to intraoperative haemodynamic instability after failed attempts to control bleeding in the surgical site. Contrast enhanced CT imaging revealed a lumbar intersegmentary artery injury that was eventually controlled by means of a coil embolisation. Copyright © 2017 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

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

Wood, Martin James; McMillen, Jason

2014-01-01

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. 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. 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. The use of CT-based computer-assisted navigation in combination with continuous EMG monitoring during

Accuracy of pedicle screw placement based on preoperative computed tomography versus intraoperative data set acquisition for spinal navigation system.

PubMed

Liu, Hao; Chen, Weikai; Liu, Tao; Meng, Bin; Yang, Huilin

2017-01-01

To investigate the accuracy of pedicle screw placement based on preoperative computed tomography in comparison with intraoperative data set acquisition for spinal navigation system. The PubMed (MEDLINE), EMBASE, and Web of Science were systematically searched for the literature published up to September 2015. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Statistical analysis was performed using the Review Manager 5.3. The dichotomous data for the pedicle violation rate was summarized using relative risk (RR) and 95% confidence intervals (CIs) with the fixed-effects model. The level of significance was set at p < 0.05. For this meta-analysis, seven studies used a total of 579 patients and 2981 screws. The results revealed that the accuracy of intraoperative data set acquisition method is significantly higher than preoperative one using 2 mm grading criteria (RR: 1.82, 95% CI: 1.09, 3.04, I 2 = 0%, p = 0.02). However, there was no significant difference between two kinds of methods at the 0 mm grading criteria (RR: 1.13, 95% CI: 0.88, 1.46, I 2 = 17%, p = 0.34). Using the 2-mm grading criteria, there was a higher accuracy of pedicle screw insertion in O-arm-assisted navigation than CT-based navigation method (RR: 1.96, 95% CI: 1.05, 3.64, I 2 = 0%, p = 0.03). The accuracy between CT-based navigation and two-dimensional-based navigation showed no significant difference (RR: 1.02, 95% CI: 0.35-3.03, I 2 = 0%, p = 0.97). The intraoperative data set acquisition method may decrease the incidence of perforated screws over 2 mm but not increase the number of screws fully contained within the pedicle compared to preoperative CT-based navigation system. A significantly higher accuracy of intraoperative (O-arm) than preoperative CT-based navigation was revealed using 2 mm grading criteria.

Inertial Measurement Unit-Assisted Implantation of Pedicle Screws in Combination With an Intraoperative 3-Dimensional/2-Dimensional Visualization of the Spine.

PubMed

Jost, Gregory F; Walti, Jonas; Mariani, Luigi; Schaeren, Stefan; Cattin, Philippe

2018-05-30

Inertial measurement units (IMUs) are microelectromechanical systems used to track orientation and motion. To use instruments mounted with IMUs in combination with a 3- and 2-dimensional (3D/2D) rendering of the computed-tomography scan (CT) to guide implantation of pedicle screws. Pedicle screws were implanted from T1 to S1 in 2 human cadavers. A software application enabled the surgeon to select the starting points and trajectories on a 3D/2D image of the spine, then locate these starting points on the exposed spine and apply the IMU-mounted instruments to reproduce the trajectories. The position of the screws was evaluated on the postoperative CT scan. A total of 72 pedicle screws were implanted. Thirty-seven (77%) of the thoracic screws were within the pedicle (Heary I), 7 (15%) showed a lateral breach of the pedicle, and 4 (8%) violated the anterior or lateral vertebral body (Heary III). In the lumbar spine and S1, 21 screws (88%) were within the pedicle (Gertzbein 0), 2 (8%) screws had a pedicle wall breach < 2 mm (Gertzbein 1), and 1 > 2 to < 4 mm (Gertzbein 2). In the second cadaver, the position was compared to the intraoperatively shown virtual position. The median offset was 3°(mean 3° ± 2°, variance 5, range 0°-9°) in the sagittal plane and 3° (mean 4° ± 3°, variance 9, range 0°-12°) in the axial plane. IMU-assisted implantation of pedicle screws combined with an intraoperative 3D/2D visualization of the spine enabled the surgeon to precisely implant pedicle screws on the exposed spine.

Validation of an improved method to calculate the orientation and magnitude of pedicle screw bending moments.

PubMed

Freeman, Andrew L; Fahim, Mina S; Bechtold, Joan E

2012-10-01

Previous methods of pedicle screw strain measurement have utilized complex, time consuming methods of strain gauge application, experience high failure rates, do not effectively measure resultant bending moments, and cannot predict moment orientation. The purpose of this biomechanical study was to validate an improved method of quantifying pedicle screw bending moment orientation and magnitude. Pedicle screws were instrumented to measure biplanar screw bending moments by positioning four strain gauges on flat, machined surfaces below the screw head. Screws were calibrated to measure bending moments by hanging certified weights a known distance from the strain gauges. Loads were applied in 30 deg increments at 12 different angles while recording data from two independent strain channels. The data were then analyzed to calculate the predicted orientation and magnitude of the resultant bending moment. Finally, flexibility tests were performed on a cadaveric motion segment implanted with the instrumented screws to demonstrate the implementation of this technique. The difference between the applied and calculated orientation of the bending moments averaged (±standard error of the mean (SEM)) 0.3 ± 0.1 deg across the four screws for all rotations and loading conditions. The calculated resultant bending moments deviated from the actual magnitudes by an average of 0.00 ± 0.00 Nm for all loading conditions. During cadaveric testing, the bending moment orientations were medial/lateral in flexion-extension, variable in lateral bending, and diagonal in axial torsion. The technique developed in this study provides an accurate method of calculating the orientation and magnitude of screw bending moments and can be utilized with any pedicle screw fixation system.

Stress analysis in a pedicle screw fixation system with flexible rods in the lumbar spine.

PubMed

Kim, Kyungsoo; Park, Won Man; Kim, Yoon Hyuk; Lee, SuKyoung

2010-01-01

Breakage of screws has been one of the most common complications in spinal fixation systems. However, no studies have examined the breakage risk of pedicle screw fixation systems that use flexible rods, even though flexible rods are currently being used for dynamic stabilization. In this study, the risk of breakage of screws for the rods with various flexibilities in pedicle screw fixation systems is investigated by calculating the von Mises stress as a breakage risk factor using finite element analysis. Three-dimensional finite element models of the lumbar spine with posterior one-level spinal fixations at L4-L5 using four types of rod (a straight rod, a 4 mm spring rod, a 3 mm spring rod, and a 2 mm spring rod) were developed. The von Mises stresses in both the pedicle screws and the rods were analysed under flexion, extension, lateral bending, and torsion moments of 10 Nm with a follower load of 400 N. The maximum von Mises stress, which was concentrated on the neck region of the pedicle screw, decreased as the flexibility of the rod increased. However, the ratio of the maximum stress in the rod to the yield stress increased substantially when a highly flexible rod was used. Thus, the level of rod flexibility should be considered carefully when using flexible rods for dynamic stabilization because the intersegmental motion facilitated by the flexible rod results in rod breakage.

Undertapping of Lumbar Pedicle Screws Can Result in Tapping With a Pitch That Differs From That of the Screw, Which Decreases Screw Pullout Force.

PubMed

Bohl, Daniel D; Basques, Bryce A; Golinvaux, Nicholas S; Toy, Jason O; Matheis, Erika A; Bucklen, Brandon S; Grauer, Jonathan N

2015-06-15

Survey of spine surgeons and biomechanical comparison of screw pullout forces. To investigate what may be a suboptimal practice regularly occurring in spine surgery. In order for a tap to function in its intended manner, the pitch of the tap should be the same as the pitch of the screw. Undertapping has been shown to increase the pullout force of pedicle screws compared with line-to-line tapping. However, given the way current commercial lumbar pedicle screw systems are designed, undertapping may result in a tap being used that has a different pitch from that of the screw (incongruent pitch). A survey asked participants questions to estimate the proportion of cases each participant performed in the prior year using various hole preparation techniques. Participant responses were interpreted in the context of manufacturing specifications of specific instrumentation systems. Screw pullout forces were compared between undertapping with incongruent pitch and undertapping with congruent pitch using 0.16 g/cm polyurethane foam block and 6.5-mm screws. Of the 3679 cases in which participants reported tapping, participants reported line-to-line tapping in 209 cases (5%), undertapping with incongruent pitch in 1156 cases (32%), and undertapping with congruent pitch in 2314 cases (63%). The mean pullout force for undertapping with incongruent pitch was 56 N (8%) less than the mean pullout force for undertapping with congruent pitch. This is equivalent to 13 lb. This study estimates that for about 1 out of every 3 surgical cases with tapping of lumbar pedicle screws in the United States, hole preparation is being performed by undertapping with incongruent pitch. This study also shows that undertapping with incongruent pitch results in a decrease in pullout force by 8% compared with undertapping with congruent pitch. Steps should be taken to correct this suboptimal practice. 3.

Posterior spinal fusion for adolescent idiopathic scoliosis using a convex pedicle screw technique: a novel concept of deformity correction.

PubMed

Tsirikos, A I; Mataliotakis, G; Bounakis, N

2017-08-01

We present the results of correcting a double or triple curve adolescent idiopathic scoliosis using a convex segmental pedicle screw technique. We reviewed 191 patients with a mean age at surgery of 15 years (11 to 23.3). Pedicle screws were placed at the convexity of each curve. Concave screws were inserted at one or two cephalad levels and two caudal levels. The mean operating time was 183 minutes (132 to 276) and the mean blood loss 0.22% of the total blood volume (0.08% to 0.4%). Multimodal monitoring remained stable throughout the operation. The mean hospital stay was 6.8 days (5 to 15). The mean post-operative follow-up was 5.8 years (2.5 to 9.5). There were no neurological complications, deep wound infection, obvious nonunion or need for revision surgery. Upper thoracic scoliosis was corrected by a mean 68.2% (38% to 48%, p < 0.001). Main thoracic scoliosis was corrected by a mean 71% (43.5% to 8.9%, p < 0.001). Lumbar scoliosis was corrected by a mean 72.3% (41% to 90%, p < 0.001). No patient lost more than 3° of correction at follow-up. The thoracic kyphosis improved by 13.1° (-21° to 49°, p < 0.001); the lumbar lordosis remained unchanged (p = 0.58). Coronal imbalance was corrected by a mean 98% (0% to 100%, p < 0.001). Sagittal imbalance was corrected by a mean 96% (20% to 100%, p < 0.001). The Scoliosis Research Society Outcomes Questionnaire score improved from a mean 3.6 to 4.6 (2.4 to 4, p < 0.001); patient satisfaction was a mean 4.9 (4.8 to 5). This technique carries low neurological and vascular risks because the screws are placed in the pedicles of the convex side of the curve, away from the spinal cord, cauda equina and the aorta. A low implant density (pedicle screw density 1.2, when a density of 2 represents placement of pedicle screws bilaterally at every instrumented segment) achieved satisfactory correction of the scoliosis, an improved thoracic kyphosis and normal global sagittal balance. Both patient satisfaction and functional

Analysis of lumbar pedicle morphology in degenerative spines using multiplanar reconstruction computed tomography: what can be the reliable index for optimal pedicle screw diameter?

PubMed

Makino, Takahiro; Kaito, Takashi; Fujiwara, Hiroyasu; Yonenobu, Kazuo

2012-08-01

The measurement of transverse pedicle width is still recommended for selecting a screw diameter despite being weakly correlated with the minimum pedicle diameter, except in the upper lumbar spine. The purpose of this study was to reveal the difference between the minimum pedicle diameter and conventional transverse or sagittal pedicle width in degenerative lumbar spines. A total of 50 patients with degenerative lumbar disorders without spondylolysis or lumbar scoliosis of >10° who preoperatively underwent helical CT scans were included. The DICOM data of the scans were reconstructed by imaging software, and the transverse pedicle width (TPW), sagittal pedicle width (SPW), minimum pedicle diameter (MPD), and the cephalocaudal inclination of the pedicles were measured. The mean TPW/SPW/MPD values were 5.46/11.89/5.09 mm at L1, 5.76/10.44/5.39 mm at L2, 7.25/10.23/6.52 mm at L3, 9.01/9.36/6.83 mm at L4, and 12.86/8.95/7.36 mm at L5. There were significant differences between the TPW and MPD at L3, L4, and L5 (p < 0.01) and between the SPW and MPD at all levels (p < 0.01). The MPD was significantly smaller than the TPW and SPW at L3, L4, and L5. The actual measurements of the TPW were not appropriate for use as a direct index for the optimal pedicle screw diameter at these levels. Surgeons should be careful in determining pedicle screw diameter based on plain CT scans especially in the lower lumbar spine.

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

In vitro validation of a novel mechanical model for testing the anchorage capacity of pedicle screws using physiological load application.

PubMed

Liebsch, Christian; Zimmermann, Julia; Graf, Nicolas; Schilling, Christoph; Wilke, Hans-Joachim; Kienle, Annette

2018-01-01

Biomechanical in vitro tests analysing screw loosening often include high standard deviations caused by high variabilities in bone mineral density and pedicle geometry, whereas standardized mechanical models made of PU foam often do not integrate anatomical or physiological boundary conditions. The purpose of this study was to develop a most realistic mechanical model for the standardized and reproducible testing of pedicle screws regarding the resistance against screw loosening and the holding force as well as to validate this model by in vitro experiments. The novel mechanical testing model represents all anatomical structures of a human vertebra and is consisting of PU foam to simulate cancellous bone, as well as a novel pedicle model made of short carbon fibre filled epoxy. Six monoaxial cannulated pedicle screws (Ø6.5 × 45mm) were tested using the mechanical testing model as well as human vertebra specimens by applying complex physiological cyclic loading (shear, tension, and bending; 5Hz testing frequency; sinusoidal pulsating forces) in a dynamic materials testing machine with stepwise increasing load after each 50.000 cycles (100.0N shear force + 20.0N per step, 51.0N tension force + 10.2N per step, 4.2Nm bending moment + 0.8Nm per step) until screw loosening was detected. The pedicle screw head was fixed on a firmly clamped rod while the load was applied in the vertebral body. For the in vitro experiments, six human lumbar vertebrae (L1-3, BMD 75.4 ± 4.0mg/cc HA, pedicle width 9.8 ± 0.6mm) were tested after implanting pedicle screws under X-ray control. Relative motions of pedicle screw, specimen fixture, and rod fixture were detected using an optical motion tracking system. Translational motions of the mechanical testing model experiments in the point of load introduction (0.9-2.2mm at 240N shear force) were reproducible within the variation range of the in vitro experiments (0.6-3.5mm at 240N shear force). Screw loosening occurred continuously in

Head-mounted display augmented reality to guide pedicle screw placement utilizing computed tomography.

PubMed

Gibby, Jacob T; Swenson, Samuel A; Cvetko, Steve; Rao, Raj; Javan, Ramin

2018-06-22

Augmented reality has potential to enhance surgical navigation and visualization. We determined whether head-mounted display augmented reality (HMD-AR) with superimposed computed tomography (CT) data could allow the wearer to percutaneously guide pedicle screw placement in an opaque lumbar model with no real-time fluoroscopic guidance. CT imaging was obtained of a phantom composed of L1-L3 Sawbones vertebrae in opaque silicone. Preprocedural planning was performed by creating virtual trajectories of appropriate angle and depth for ideal approach into the pedicle, and these data were integrated into the Microsoft HoloLens using the Novarad OpenSight application allowing the user to view the virtual trajectory guides and CT images superimposed on the phantom in two and three dimensions. Spinal needles were inserted following the virtual trajectories to the point of contact with bone. Repeat CT revealed actual needle trajectory, allowing comparison with the ideal preprocedural paths. Registration of AR to phantom showed a roughly circular deviation with maximum average radius of 2.5 mm. Users took an average of 200 s to place a needle. Extrapolation of needle trajectory into the pedicle showed that of 36 needles placed, 35 (97%) would have remained within the pedicles. Needles placed approximated a mean distance of 4.69 mm in the mediolateral direction and 4.48 mm in the craniocaudal direction from pedicle bone edge. To our knowledge, this is the first peer-reviewed report and evaluation of HMD-AR with superimposed 3D guidance utilizing CT for spinal pedicle guide placement for the purpose of cannulation without the use of fluoroscopy.

Robot-assisted and conventional freehand pedicle screw placement: a systematic review and meta-analysis of randomized controlled trials.

PubMed

Gao, Shutao; Lv, Zhengtao; Fang, Huang

2018-04-01

Several studies have revealed that robot-assisted technique might improve the pedicle screw insertion accuracy, but owing to the limited sample sizes in the individual study reported up to now, whether or not robot-assisted technique is superior to conventional freehand technique is indefinite. Thus, we performed this systematic review and meta-analysis based on randomized controlled trials to assess which approach is better. Electronic databases including PubMed, EMBASE, CENTRAL, ISI Web of Science, CNKI and WanFang were systematically searched to identify potentially eligible articles. Main endpoints containing the accuracy of pedicle screw implantation and proximal facet joint violation were evaluated as risk ratio (RR) and the associated 95% confidence intervals (95% CIs), while radiation exposure and surgical duration were presented as mean difference (MD) or standard mean difference (SMD). Meta-analyses were performed using RevMan 5.3 software. Six studies involving 158 patients (688 pedicle screws) in robot-assisted group and 148 patients (672 pedicle screws) in freehand group were identified matching our study. The Grade A accuracy rate in robot-assisted group was superior to freehand group (RR 1.03, 95% CI 1.00, 1.06; P = 0.04), but the Grade A + B accuracy rate did not differ between the two groups (RR 1.01, 95% CI 0.99, 1.02; P = 0.29). With regard to proximal facet joint violation, the combined results suggested that robot-assisted group was associated with significantly fewer proximal facet joint violation than freehand group (RR 0.07, 95% CI 0.01, 0.55; P = 0.01). As was the radiation exposure, our findings suggested that robot-assisted technique could significantly reduce the intraoperative radiation time (MD - 12.38, 95% CI - 17.95, - 6.80; P < 0.0001) and radiation dosage (SMD - 0.64, 95% CI - 0.85, - 0.43; P < 0.00001). But the overall surgical duration was longer in robot-assisted group than conventional freehand group (MD 20

Comparative analysis of hook, hybrid, and pedicle screw instrumentation in the posterior treatment of adolescent idiopathic scoliosis.

PubMed

Yilmaz, Guney; Borkhuu, Battugs; Dhawale, Arjun A; Oto, Murat; Littleton, Aaron G; Mason, Dan E; Gabos, Peter G; Shah, Suken A

2012-01-01

Spinal instrumentation in adolescent idiopathic scoliosis (AIS) aims to correct spinal deformity and maintain long-term spinal stability until bony healing is ensured. The purpose of this study was to compare the minimum 2-year postoperative radiographic and clinical results of posterior spine correction and fusion with all-hook instrumentation versus hybrid segmental instrumentation versus pedicle screw instrumentation for AIS from a single institution. A total of 105 patients with AIS who underwent a posterior spinal fusion with segmental pedicle screw (35), hook (35), or hybrid (35) instrumentation were sorted and matched according to the following criteria: similar age at surgery, identical Lenke curve types, curve magnitude, and Risser grade. Patients were evaluated before, immediately after, and at 2 years after surgery for radiographic parameters, complications, and outcome, as well as on the basis of the Scoliosis Research Society (SRS) questionnaire. The age and Risser grade, major curve Cobb angle, apical vertebral rotation (AVR), apical vertebral translation (AVT), lowest instrumented vertebral tilt, global coronal and sagittal balance, lumbar lordosis, and thoracic kyphosis were determined as part of preoperative evaluation. All 3 groups showed significant differences between the preoperative and postoperative major curve Cobb angle, lowest instrumented vertebral tilt, AVT, and AVR. At the latest follow-up, lumbar lordosis, thoracic kyphosis, and global coronal and sagittal balance remained similar among the 3 groups. Major curve Cobb angle, AVT, and AVR were significantly different--the hook group's measurements were significantly higher than the other groups, but there was no difference between the pedicle screw and hybrid groups. Major curve correction rate was significantly different among all groups (screw=71.9%±13.8%, hybrid=61.4%±16.6%, hook=48.1%±19.7%) (P<0.001). The pedicle screw group had the least amount of correction loss but there was

Image Guidance to Aid Pedicle Screw Fixation of a Lumbar Fracture-Dislocation Injury in a Toddler.

PubMed

Houten, John K; Nahkla, Jonathan; Ghandi, Shashank

2017-09-01

Pedicle screw fixation of the lumbar spine in children age <2 years is particularly challenging, as successful cannulation of the small pedicle dimensions requires a high level of precision and there are no implants specifically designed for the infant spine. Image-guided navigation is commonly used in adult spinal surgery and may be particularly helpful for the placement of spinal screws in areas where the bony anatomy is small and/or anatomically complex, as in the upper cervical area. A 19-month-old female presented with a fracture-dislocation injury of L1-2. Intraoperative imaging using the O-arm multidimensional imaging system was networked to a workstation, and neuronavigation was used to place pedicle instrumentation with 3.5-mm-diameter polyaxial screws designed for posterior cervical fixation. At a 48-month follow-up, the patient was neurologically intact, demonstrated normal physical development, and was engaging in normal physical activity for her age. Radiographs obtained approximately 4 years postsurgery showed no evidence of loss for fixation. Image-guided placement of pedicle screws may be a useful aid in achieving accurate and safe fixation in the small dimensions of the infant spine. Copyright © 2017 Elsevier Inc. All rights reserved.

A novel injectable calcium phosphate-based nanocomposite for the augmentation of cannulated pedicle-screw fixation

PubMed Central

Sun, Haolin; Liu, Chun; Liu, Huiling; Bai, Yanjie; Zhang, Zheng; Li, Xuwen; Li, Chunde; Yang, Huilin; Yang, Lei

2017-01-01

Polymethyl methacrylate (PMMA)-augmented cannulated pedicle-screw fixation has been routinely performed for the surgical treatment of lumbar degenerative diseases. Despite its satisfactory clinical outcomes and prevalence, problems and complications associated with high-strength, stiff, and nondegradable PMMA have largely hindered the long-term efficacy and safety of pedicle-screw fixation in osteoporotic patients. To meet the unmet need for better bone cement for cannulated pedicle-screw fixation, a new injectable and biodegradable nanocomposite that was the first of its kind was designed and developed in the present study. The calcium phosphate-based nanocomposite (CPN) exhibited better anti-pullout ability and similar fluidity and dispersing ability compared to clinically used PMMA, and outperformed conventional calcium phosphate cement (CPC) in all types of mechanical properties, injectability, and biodegradability. In term of axial pullout strength, the CPN-augmented cannulated screw reached the highest force of ~120 N, which was higher than that of PMMA (~100 N) and CPC (~95 N). The compressive strength of the CPN (50 MPa) was three times that of CPC, and the injectability of the CPN reached 95%. In vivo tests on rat femur revealed explicit biodegradation of the CPN and subsequent bone ingrowth after 8 weeks. The promising results for the CPN clearly suggest its potential for replacing PMMA in the application of cannulated pedicle-screw fixation and its worth of further study and development for clinical uses. PMID:28490878

Anterior cervical pedicle screw and plate fixation using fluoroscope-assisted pedicle axis view imaging: a preliminary report of a new cervical reconstruction technique

PubMed Central

Kato, Fumihiko; Ito, Keigo; Nakashima, Hiroaki; Machino, Masaaki

2009-01-01

Anterior procedures in the cervical spine are feasible in cases having anterior aetiologies such as anterior neural compression and/or severe kyphosis. Halo vests or anterior plates are used concurrently for cases with long segmental fixation. Halo vests are bothersome and anterior plate fixation is not adequately durable. We developed a new anterior pedicle screw (APS) and plate fixation procedure that can be used with fluoroscope-assisted pedicle axis view imaging. Six patients (3 men and 3 women; mean age, 54 years) with anterior multisegmental aetiology were included in this study. Their original diagnoses comprised cervical myelopathy and/or radiculopathy (n = 4), posterior longitudinal ligament ossification (n = 1) and post-traumatic kyphosis (n = 1). All patients underwent anterior decompression and strut grafting with APS and plate fixation. Mean operative time was 192 min and average blood loss was 73 ml. Patients were permitted to ambulate the next day with a cervical collar. Local sagittal alignment was characterised by 3.5° of kyphosis preoperatively, which improved to 6.8° of lordosis postoperatively and 5.2° of lordosis at final follow-up. Postoperative improvement and early bony union were observed in all cases. There was no serious complication except for two cases of dysphagia. Postoperative imaging demonstrated screw exposure in one screw, but no pedicle perforation. APS and plate fixation is useful in selected cases of multisegmental anterior reconstruction of cervical spine. However, the adequate familiarity and experience with both cervical pedicle screw fixation and the imaging technique used for visualising the pedicle during surgery are crucial for this procedure. PMID:19343377

[Clinical application of atlantoaxial pedicle screw internal fixation for treatment of atlantoaxial dislocation].

PubMed

Yang, Yong-Jun; Zhang, En-Zhong; Tan, Yuan-Chao; Zhou, Ji-Ping; Yao, Shu-Qiang; Jiang, Chuan-Jie; Cong, Pei-Yan

2009-11-01

To investigate the clinical effect of atlantoaxial pedicle screw internal fixation for treatment of atlantoaxial dislocation. Sixteen patients with atlantoaxial dislocation were treated from Dec. 2005 to June 2007, included 10 males and 6 females, aged from 38 to 45 years old (means 40.5 years). Among them 12 patients combined with nerve injury, according to ASIA grade: there were 3 cases in grade B, 5 cases in grade C, 4 cases in grade D. All patients received preoperative CT, radiograph and skull traction. Intraoperative posterior approach general spine pedicle screw-rod orthopaedics fixation system used and iliac bone block were implanted in space of posterior atlantal arch and axial vertebral plate. The outcome and complications were observed in the near future. There was no vascular or neural injury found. The patients were followed up for 12 to 24 months (means 18 months). All head pain, acid storm symptoms were improved after operation. According to the Odom's clinical efficacy evaluation standard, 12 cases were excellent, 4 were good. Eleven cases of 12 with nerve injury recovered significantly. By ASIA classification: 1 cases was in grade B, 2 cases were in grade C, 5 cases were in grade D, 4 cases were in grade E. No looseness or breakage of screw occurred. Bony fusion was achieved in all cases. Posterior approach atlantoaxial pedicle screw internal fixation have the advantages of direct screw placement, short-segment fusion, intraoperative reduction, fixation reliable, high fusion rate, and it can restablish the upper cervical vertebrae stability and help to recover the spinal cord and nerve function.

The Utility of a Digital Virtual Template for Junior Surgeons in Pedicle Screw Placement in the Lumbar Spine.

PubMed

Zhao, Xin; Zhao, Jie; Xie, Youzhuan; Mi, Jie

2016-01-01

This study assessed the utility of three-dimensional preoperative image reconstruction as digital virtual templating for junior surgeons in placing a pedicle screw (PS) in the lumbar spine. Twenty-three patients of lumbar disease were operated on with bilateral PS fixation in our hospital. The two sides of lumbar pedicles were randomly divided into "hand-free group" (HFG) and "digital virtual template group" (DVTG) in each patient. Two junior surgeons preoperatively randomly divided into these two groups finished the placement of PSs. The accuracy of PS and the procedure time of PS insertion were recorded. The accuracy of PS in DVTG was 91.8% and that in HFG was 87.7%. The PS insertion procedure time of DVTG was 74.5 ± 8.1 s and that of HFG was 90.9 ± 9.9 s. Although no significant difference was reported in the accurate rate of PS between the two groups, the PS insertion procedure time was significantly shorter in DVTG than in HFG (P < 0.05). Digital virtual template is simple and can reduce the procedure time of PS placement.

Severe fixed cervical kyphosis treated with circumferential osteotomy and pedicle screw fixation using an anterior-posterior-anterior surgical sequence.

PubMed

Yoshihara, Hiroyuki; Abumi, Kuniyoshi; Ito, Manabu; Kotani, Yoshihisa; Sudo, Hideki; Takahata, Masahiko

2013-11-01

Surgical treatment for severe circumferentially fixed cervical kyphosis has been challenging. Both anterior and posterior releases are necessary to provide the cervical mobility necessary for fusion in a corrected position. In two case reports, we describe the circumferential osteotomy of anterior-posterior-anterior surgical sequence, and the efficacy of this technique when cervical pedicle screw fixation for severe fixed cervical kyphosis is used. Etiology of fixed cervical kyphosis was unknown in one patient and neurofibromatosis in one patient. Both patients had severe fixed cervical kyphosis as determined by cervical radiographs and underwent circumferential osteotomy and fixation via an anterior-posterior-anterior surgical sequence and correction of kyphosis by pedicle screw fixation. Severe fixed cervical kyphosis was treated successfully by the use of circumferential osteotomy and pedicle screw fixation. The surgical sequence described in this report is a reasonable approach for severe circumferentially fixed cervical kyphosis and short segment fixation can be achieved using pedicle screws. Copyright © 2013 Elsevier Inc. All rights reserved.

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

PubMed

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

2016-03-01

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 higher than

Radiofrequency-activated PMMA-augmentation through cannulated pedicle screws: A cadaver study to determine the biomechanical benefits in the osteoporotic spine.

PubMed

Karius, T; Deborre, C; Wirtz, D C; Burger, C; Prescher, A; Fölsch, A; Kabir, K; Pflugmacher, R; Goost, H

2017-01-01

PMMA-augmentation of pedicle screws strengthens the bone-screw-interface reducing cut-out risk. Injection of fluid cement bears a higher risk of extravasation, with difficulty of application because of inconsistent viscosity and limited injection time. To test a new method of cement augmentation of pedicle screws using radiofrequency-activated PMMA, which is suspected to be easier to apply and have less extravasations. Twenty-seven fresh-frozen human cadaver lumbar spines were divided into 18 osteoporotic (BMD ≤ 0.8 g/cm2) and 9 non-osteoporotic (BMD > 0.8 g/cm2) vertebral bodies. Bipedicular cannulated pedicle screws were implanted into the vertebral bodies; right screws were augmented with ultra-high viscosity PMMA, whereas un-cemented left pedicle screws served as negative controls. Cement distribution was controlled with fluoroscopy and CT scans. Axial pullout forces of the screws were measured with a material testing machine, and results were analyzed statistically. Fluoroscopy and CT scans showed that in all cases an adequately big cement depot with homogenous form and no signs of extravasation was injected. Pullout forces showed significant differences (p < 0.001) between the augmented and non-augmented pedicle screws for bone densities below 0.8 g/cm2 (661.9 N ± 439) and over 0.8 g/cm2 (744.9 N ± 415). Pullout-forces were significantly increased in osteoporotic as well as in non-osteoporotic vertebral bodies without a significant difference between these groups using this standardized, simple procedure with increased control and less complications like extravasation.

Reciprocal Changes in Sagittal Alignment in Adolescent Idiopathic Scoliosis Patients Following Strategic Pedicle Screw Fixation.

PubMed

Dumpa, Srikanth Reddy; Shetty, Ajoy Prasad; Aiyer, Siddharth N; Kanna, Rishi Mugesh; Rajasekaran, S

2018-04-01

Retrospective observational study. To analyze the effect of low-density (LD) strategic pedicle screw fixation on the correction of coronal and sagittal parameters in adolescent idiopathic scoliosis (AIS) patients. LD screw fixation achieves favorable coronal correction, but its effect on sagittal parameters is not well established. AIS is often associated with decreased thoracic kyphosis (TK), and the use of multi-level pedicle screws may result in further flattening of the sagittal profile. A retrospective analysis was performed on 92 patients with AIS to compare coronal and sagittal parameters preoperatively and at 2-year follow-up. All patients underwent posterior correction via LD strategic pedicle screw fixation. Radiographs were analyzed for primary Cobb angle (PCA), coronal imbalance, cervical sagittal angle (CSA), TK, lumbar lordosis (LL), pelvic incidence, pelvic tilt (PT), sacral slope (SS), C7 plumb line, spino-sacral angle, curve flexibility, and screw density. PCA changed significantly from 57.6°±13.9° to 19°±8.4° ( p <0.0001) with 67% correction, where the mean curve flexibility was 41% and screw density was 68%. Regional sagittal parameters did not change significantly, including CSA (from 10.76° to 10.56°, p =0.893), TK (from 24.4° to 22.8°, p =0.145), and LL (from 50.3° to 51.1°, p =0.415). However, subgroup analysis of the hypokyphosis group (<10°) and the hyperkyphosis group (>40°) showed significant correction of TK ( p <0.0001 in both). Sacro-pelvic parameters showed a significant decrease of PT and increase of SS, suggesting a reduction in pelvic retroversion SS (from 37° to 40°, p =0.0001) and PT (from 15° to 14°, p =0.025). LD strategic pedicle screw fixation provides favorable coronal correction and improves overall sagittal sacro-pelvic parameters. This technique does not cause significant flattening of TK and results in a favorable restoration of TK in patients with hypokyphosis or hyperkyphosis.

Reciprocal Changes in Sagittal Alignment in Adolescent Idiopathic Scoliosis Patients Following Strategic Pedicle Screw Fixation

PubMed Central

Dumpa, Srikanth Reddy; Aiyer, Siddharth N.; Kanna, Rishi Mugesh; Rajasekaran, S

2018-01-01

Study Design Retrospective observational study. Purpose To analyze the effect of low-density (LD) strategic pedicle screw fixation on the correction of coronal and sagittal parameters in adolescent idiopathic scoliosis (AIS) patients. Overview of Literature LD screw fixation achieves favorable coronal correction, but its effect on sagittal parameters is not well established. AIS is often associated with decreased thoracic kyphosis (TK), and the use of multi-level pedicle screws may result in further flattening of the sagittal profile. Methods A retrospective analysis was performed on 92 patients with AIS to compare coronal and sagittal parameters preoperatively and at 2-year follow-up. All patients underwent posterior correction via LD strategic pedicle screw fixation. Radiographs were analyzed for primary Cobb angle (PCA), coronal imbalance, cervical sagittal angle (CSA), TK, lumbar lordosis (LL), pelvic incidence, pelvic tilt (PT), sacral slope (SS), C7 plumb line, spino-sacral angle, curve flexibility, and screw density. Results PCA changed significantly from 57.6°±13.9° to 19°±8.4° (p <0.0001) with 67% correction, where the mean curve flexibility was 41% and screw density was 68%. Regional sagittal parameters did not change significantly, including CSA (from 10.76° to 10.56°, p =0.893), TK (from 24.4° to 22.8°, p =0.145), and LL (from 50.3° to 51.1°, p =0.415). However, subgroup analysis of the hypokyphosis group (<10°) and the hyperkyphosis group (>40°) showed significant correction of TK (p <0.0001 in both). Sacro-pelvic parameters showed a significant decrease of PT and increase of SS, suggesting a reduction in pelvic retroversion SS (from 37° to 40°, p =0.0001) and PT (from 15° to 14°, p =0.025). Conclusions LD strategic pedicle screw fixation provides favorable coronal correction and improves overall sagittal sacro-pelvic parameters. This technique does not cause significant flattening of TK and results in a favorable restoration of TK in

Comparative Cohort Study of Percutaneous Pedicle Screw Implantation without Versus with Navigation in Patients Undergoing Surgery for Degenerative Lumbar Disc Disease.

PubMed

Fomekong, Edward; Pierrard, Julien; Raftopoulos, Christian

2018-03-01

The major limitation of computer-based three-dimensional fluoroscopy is increased radiation exposure of patients and operating room staff. Combining spine navigation with intraoperative three-dimensional fluoroscopy (io3DF) can likely overcome this shortcoming, while increasing pedicle screw accuracy rate. We compared data from a cohort of patients undergoing lumbar percutaneous pedicle screw placement using io3DF alone or in combination with spine navigation. This study consisted of 168 patients who underwent percutaneous pedicle screw implantation between 2009 and 2016. The primary endpoint was to compare pedicle screw accuracy between the 2 groups. Secondary endpoints were to compare radiation exposure of patients and operating room staff, duration of surgery, and postoperative complications. In group 1, 438 screws were placed without navigation guidance; in group 2, 276 screws were placed with spine navigation. Mean patient age in both groups was 58.6 ± 14.1 years. The final pedicle accuracy rate was 97.9% in group 1 and 99.6% in group 2. Average radiation dose per patient was significantly larger in group 1 (571.9 mGym 2 ) than in group 2 (365.6 mGym 2 ) (P = 0.000088). Surgery duration and complication rate were not significantly different between the 2 groups (P > 0.05). io3DF with spine navigation minimized radiation exposure of patients and operating room staff and provided an excellent percutaneous pedicle screw accuracy rate with no permanent complications compared with io3DF alone. This setup is recommended, especially for patients with a complex degenerative spine condition. Copyright © 2017 Elsevier Inc. All rights reserved.

Metal artifacts reduction using monochromatic images from spectral CT: evaluation of pedicle screws in patients with scoliosis.

PubMed

Wang, Yang; Qian, Bangping; Li, Baoxin; Qin, Guochu; Zhou, Zhengyang; Qiu, Yong; Sun, Xizhao; Zhu, Bin

2013-08-01

To evaluate the effectiveness of spectral CT in reducing metal artifacts caused by pedicle screws in patients with scoliosis. Institutional review committee approval and written informed consents from patients were obtained. 18 scoliotic patients with a total of 228 pedicle screws who underwent spectral CT imaging were included in this study. Monochromatic image sets with and without the additional metal artifacts reduction software (MARS) correction were generated with photon energy at 65keV and from 70 to 140keV with 10keV interval using the 80kVp and 140kVp projection sets. Polychromatic images corresponded to the conventional 140kVp imaging were also generated from the same scan data as a control group. Both objective evaluation (screw width and quantitative artifacts index measurements) and subjective evaluation (depiction of pedicle screws, surrounding structures and their relationship) were performed. Image quality of monochromatic images in the range from 110 to 140keV (0.97±0.28) was rated superior to the conventional polychromatic images (2.53±0.54) and also better than monochromatic images with lower energy. Images of energy above 100keV also give accurate measurement of the width of screws and relatively low artifacts index. The form of screws was slightly distorted in MARS reconstruction. Compared to conventional polychromatic images, monochromatic images acquired from dual-energy CT provided superior image quality with much reduced metal artifacts of pedicle screws in patients with scoliosis. Optimal energy range was found between 110 and 140keV. Crown Copyright © 2013. Published by Elsevier Ireland Ltd. All rights reserved.

Comparison of low density and high density pedicle screw instrumentation in Lenke 1 adolescent idiopathic scoliosis.

PubMed

Shen, Mingkui; Jiang, Honghui; Luo, Ming; Wang, Wengang; Li, Ning; Wang, Lulu; Xia, Lei

2017-08-02

The correlation between implant density and deformity correction has not yet led to a precise conclusion in adolescent idiopathic scoliosis (AIS). The aim of this study was to evaluate the effects of low density (LD) and high density (HD) pedicle screw instrumentation in terms of the clinical, radiological and Scoliosis Research Society (SRS)-22 outcomes in Lenke 1 AIS. We retrospectively reviewed 62 consecutive Lenke 1 AIS patients who underwent posterior spinal arthrodesis using all-pedicle screw instrumentation with a minimum follow-up of 24 months. The implant density was defined as the number of screws per spinal level fused. Patients were then divided into two groups according to the average implant density for the entire study. The LD group (n = 28) had fewer than 1.61 screws per level, while the HD group (n = 34) had more than 1.61 screws per level. The radiographs were analysed preoperatively, postoperatively and at final follow-up. The perioperative and SRS-22 outcomes were also assessed. Independent sample t tests were used between the two groups. Comparisons between the two groups showed no significant differences in the correction of the main thoracic curve and thoracic kyphosis, blood transfusion, hospital stay, and SRS-22 scores. Compared with the HD group, there was a decreased operating time (278.4 vs. 331.0 min, p = 0.004) and decreased blood loss (823.6 vs. 1010.9 ml, p = 0.048), pedicle screws needed (15.1 vs. 19.6, p < 0.001), and implant costs ($10,191.0 vs. $13,577.3, p = 0.003) in the LD group. Both low density and high density pedicle screw instrumentation achieved satisfactory deformity correction in Lenke 1 AIS patients. However, the operating time and blood loss were reduced, and the implant costs were decreased with the use of low screw density constructs.

Predicting cancellous bone failure during screw insertion.

PubMed

Reynolds, Karen J; Cleek, Tammy M; Mohtar, Aaron A; Hearn, Trevor C

2013-04-05

Internal fixation of fractures often requires the tightening of bone screws to stabilise fragments. Inadequate application of torque can leave the fracture unstable, while over-tightening results in the stripping of the thread and loss of fixation. The optimal amount of screw torque is specific to each application and in practice is difficult to attain due to the wide variability in bone properties including bone density. The aim of the research presented in this paper is to investigate the relationships between motor torque and screw compression during powered screw insertion, and to evaluate whether the torque during insertion can be used to predict the ultimate failure torque of the bone. A custom test rig was designed and built for bone screw experiments. By inserting cancellous bone screws into synthetic, ovine and human bone specimens, it was established that variations related to bone density could be automatically detected through the effects of the bone on the rotational characteristics of the screw. The torque measured during screw insertion was found to be directly related to bone density and can be used, on its own, as a good predictor of ultimate failure torque of the bone. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Micro-CT evaluation and histological analysis of screw-bone interface of expansive pedicle screw in osteoporotic sheep.

PubMed

Wan, Shi-yong; Lei, Wei; Wu, Zi-xiang; Lv, Rong; Wang, Jun; Fu, Suo-chao; Li, Bo; Zhan, Ce

2008-04-01

To investigate the properties of screw-bone interface of expansive pedicle screw (EPS) in osteoporotic sheep by micro-CT and histological observation. Six female sheep with bilateral ovariectomy-induced osteoporosis were employed in this experiment. After EPS insertion in each femoral condyle, the sheep were randomly divided into two groups: 3 sheep were bred for 3 months (Group A), while the other 3 were bred for 6 months (Group B). After the animals being killed, the femoral condyles with EPS were obtained, which were three-dimensionally-imaged and reconstructed by micro-CT. Histological evaluation was made thereafter. The trabecular microstructure was denser at the screw-bone interface than in the distant parts in expansive section, especially within the spiral marking. In the non-expansive section, however, there was no significant difference between the interface and the distant parts. The regions of interest (ROI) adjacent to EPS were reconstructed and analyzed by micro-CT with the same thresholds. The three-dimensional (3-D) parameters, including tissue mineral density (TMD), bone volume fraction (BVF, BV/TV), bone surface/bone volume (BS/BV) ratio, trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp), were significantly better in expansive sections than non-expansive sections (P less than 0.05). Histologically, newly-formed bony trabeculae crawled along the expansive fissures and into the center of EPS. The newly-formed bones, as well as the bones at the bone-screw interface, closely contacted with the EPS and constructed four compartments. The findings of the current study, based on micro-CT and histological evaluation, suggest that EPS can significantly provide stabilization in osteoporotic cancellous bones.

Spinal pedicle screw planning using deformable atlas registration.

PubMed

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

2017-04-07

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 of

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

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

Testing Pullout Strength of Pedicle Screw Using Synthetic Bone Models: Is a Bilayer Foam Model a Better Representation of Vertebra?

PubMed

Varghese, Vicky; Krishnan, Venkatesh; Saravana Kumar, Gurunathan

2018-06-01

A biomechanical study. A new biomechanical model of the vertebra has been developed that accounts for the inhomogeneity of bone and the contribution of the pedicle toward the holding strength of a pedicle screw. Pullout strength studies are typically carried out on rigid polyurethane foams that represent the homogeneous vertebral framework of the spine. However, the contribution of the pedicle region, which contributes to the inhomogeneity in this framework, has not been considered in previous investigations. Therefore, we propose a new biomechanical model that can account for the vertebral inhomogeneity, especially the contribution of the pedicles toward the pullout strength of the pedicle screw. A bilayer foam model was developed by joining two foams representing the pedicle and the vertebra. The results of the pullout strength tests performed on the foam models were compared with those from the tests performed on the cadaver lumbar vertebra. Significant differences ( p <0.05) were observed between the pullout strength of the pedicle screw in extremely osteoporotic (0.18±0.11 kN), osteoporotic (0.37±0.14 kN), and normal (0.97±0.4 kN) cadaver vertebra. In the monolayer model, significant differences ( p <0.05) were observed in pullout strength between extremely osteoporotic (0.3±0.02 kN), osteoporotic (0.65±0.12 kN), and normal (0.99±0.04 kN) bone model. However, the bilayer foam model exhibited no significant differences ( p >0.05) in the pullout strength of pedicle screws between osteoporotic (0.85±0.08 kN) and extremely osteoporotic bone models (0.94±0.08 kN), but there was a significant difference ( p <0.05) between osteoporotic (0.94±0.08 kN) and normal bone models (1.19±0.05 kN). There were no significant differences ( p >0.05) in pullout strength between cadaver and bilayer foam model in normal bones. The new synthetic bone model that reflects the contribution of the pedicles to the pullout strength of the pedicle screws could provide a more

A medium invasiveness multi-level patient's specific template for pedicle screw placement in the scoliosis surgery.

PubMed

Azimifar, Farhad; Hassani, Kamran; Saveh, Amir Hossein; Ghomsheh, Farhad Tabatabai

2017-11-14

Several methods including free-hand technique, fluoroscopic guidance, image-guided navigation, computer-assisted surgery system, robotic platform and patient's specific templates are being used for pedicle screw placement. These methods have screw misplacements and are not always easy to be applied. Furthermore, it is necessary to expose completely a large portions of the spine in order to access fit entirely around the vertebrae. In this study, a multi-level patient's specific template with medium invasiveness was proposed for pedicle screw placement in the scoliosis surgery. It helps to solve the problems related to the soft tissues removal. After a computer tomography (CT) scan of the spine, the templates were designed based on surgical considerations. Each template was manufactured using three-dimensional printing technology under a semi-flexible post processing. The templates were placed on vertebras at four points-at the base of the superior-inferior articular processes on both left-right sides. This helps to obtain less invasive and more accurate procedure as well as true-stable and easy placement in a unique position. The accuracy of screw positions was confirmed by CT scan after screw placement. The result showed the correct alignment in pedicle screw placement. In addition, the template has been initially tested on a metal wire series Moulage (height 70 cm and material is PVC). The results demonstrated that it could be possible to implement it on a real patient. The proposed template significantly reduced screw misplacements, increased stability, and decreased the sliding & the intervention invasiveness.

Effect of insertion torque on bone screw pullout strength.

PubMed

Lawson, K J; Brems, J

2001-05-01

The effect of insertion torque on the holding strength of 4.5-mm ASIF/AO cortical bone screws was studied in vitro. Screw holding strength was determined using an Instron materials testing machine (Bristol, United Kingdom) on 55 lamb femora and 30 human tibiocortical bone sections. Holding strength was defined as tensile stress at pullout with rapid loading to construct failure. Different insertion torques were tested, normalizing to the thickness of cortical bone specimen engaged. These represented low, intermediate, high, and thread-damaging insertion torque. All screws inserted with thread-damaging torque and single cortex engaging screws inserted to high torque tightening moments showed diminished holding strength. This loss of strength amounted to 40%-50% less than screws inserted with less torque.

Time-elapsed screw insertion with microCT imaging.

PubMed

Ryan, M K; Mohtar, A A; Cleek, T M; Reynolds, K J

2016-01-25

Time-elapsed analysis of bone is an innovative technique that uses sequential image data to analyze bone mechanics under a given loading regime. This paper presents the development of a novel device capable of performing step-wise screw insertion into excised bone specimens, within the microCT environment, whilst simultaneously recording insertion torque, compression under the screw head and rotation angle. The system is computer controlled and screw insertion is performed in incremental steps of insertion torque. A series of screw insertion tests to failure were performed (n=21) to establish a relationship between the torque at head contact and stripping torque (R(2)=0.89). The test-device was then used to perform step-wise screw insertion, stopping at intervals of 20%, 40%, 60% and 80% between screw head contact and screw stripping. Image data-sets were acquired at each of these time-points as well as at head contact and post-failure. Examination of the image data revealed the trabecular deformation as a result of increased insertion torque was restricted to within 1mm of the outer diameter of the screw thread. Minimal deformation occurred prior to the step between the 80% time-point and post-failure. The device presented has allowed, for the first time, visualization of the micro-mechanical response in the peri-implant bone with increased tightening torque. Further testing on more samples is expected to increase our understanding of the effects of increased tightening torque at the micro-structural level, and the failure mechanisms of trabeculae. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cost-Utility Analysis of Pedicle Screw Removal After Successful Posterior Instrumented Fusion in Thoracolumbar Burst Fractures.

PubMed

Lee, Han-Dong; Jeon, Chang-Hoon; Chung, Nam-Su; Seo, Young-Wook

2017-08-01

A cost-utility analysis (CUA). The aim of this study was to determine the cost-effectiveness of pedicle screw removal after posterior fusion in thoracolumbar burst fractures. Pedicle screw instrumentation is a standard fixation method for unstable thoracolumbar burst fracture. However, removal of the pedicle screw after successful fusion remains controversial because the clinical benefits remain unclear. CUA can help clinicians make appropriate decisions about optimal health care for pedicle screw removal after successful fusion in thoracolumbar burst fractures. We conducted a single-center, retrospective, longitudinal matched-cohort study of prospectively collected outcomes. In total, 88 consecutive patients who had undergone pedicle screw instrumentation for thoracolumbar burst fracture with successful fusion confirmed by computed tomography (CT) were used in this study. In total, 45 patients wanted to undergo implant removal surgery (R group), and 43 decided not to remove the implant (NR group). A CUA was conducted from the health care perspective. The direct costs of health care were obtained from the medical bill of each patient. Changes in health-related quality of life (HRQoL) scores, validated by Short Form 6D, were used to calculate quality-adjusted life-years (QALYs). Total costs and gained QALY were calculated at 1 year (1 year) and 2 years (2 years) compared with baseline. Results are expressed as an incremental cost-effectiveness ratio (ICER). Different discount rates (0%, 3%, and 5%) were applied to both cost and QALY for sensitivity analysis. Baseline patient variables were similar between the two groups (all P > 0.05). The additional benefits of implant removal (0.201 QALY at 2 years) were achieved with additional costs ($2541 at 2 years), equating to an ICER of $12,641/QALY. On the basis of the different discount rates, the robustness of our study's results was also determined. Implant removal after successful fusion in a thoracolumbar burst

Traumatic dislocation of the S1 polyaxial pedicle screw head: a case report

PubMed Central

Du Plessis, Pieter N. B.; Lau, Bernard P. H.

2017-01-01

Polyaxial screw head dislocation in the absence of a manufacture defect is extremely rare and represents a biomechanical overload of the screw, leading to early failure. A 58-year-old gentleman underwent instrumented fusion using polyaxial pedicle screws-titanium rod construct with interbody cage for spondylolytic spondylolisthesis at the L5/S1 level. He attempted to bend forward ten days after the surgery which resulted in a dislocation of the right S1 polyaxial screw head from the screw shank with recurrence of symptoms. He underwent revision surgery uneventfully. This case highlights the need to pay particular attention to the strength of fixation and the amount of release to avoid such a complication. PMID:28435927

Traumatic dislocation of the S1 polyaxial pedicle screw head: a case report.

PubMed

Du Plessis, Pieter N B; Lau, Bernard P H; Hey, Hwee Weng Dennis

2017-03-01

Polyaxial screw head dislocation in the absence of a manufacture defect is extremely rare and represents a biomechanical overload of the screw, leading to early failure. A 58-year-old gentleman underwent instrumented fusion using polyaxial pedicle screws-titanium rod construct with interbody cage for spondylolytic spondylolisthesis at the L5/S1 level. He attempted to bend forward ten days after the surgery which resulted in a dislocation of the right S1 polyaxial screw head from the screw shank with recurrence of symptoms. He underwent revision surgery uneventfully. This case highlights the need to pay particular attention to the strength of fixation and the amount of release to avoid such a complication.

Comparison between two pedicle screw augmentation instrumentations in adult degenerative scoliosis with osteoporosis.

PubMed

Xie, Yang; Fu, Qiang; Chen, Zi-qiang; Shi, Zhi-cai; Zhu, Xiao-dong; Wang, Chuan-feng; Li, Ming

2011-12-21

The operative treatment of adult degenerative scoliosis combined with osteoporosis increase following the epidemiological development. Studies have confirmed that screws in osteoporotic spines have significant lower-screw strength with more frequent screw movements within the vertebra than normal spines. Screws augmented with polymethylmethacrylate (PMMA) or with autogenous bone can offer more powerful corrective force and significant advantages. A retrospective analysis was conducted on 31 consecutive patients with degenerative lumbar scoliosis combined with osteoporosis who had surgery from December 2000. All had a minimum of 2-year follow-up. All patients had posterior approach surgery. 14 of them were fixed with pedicle screw by augmentation with polymethylmethacrylate (PMMA) and the other 17 patients with autogenous bone. Age, sex and whether smoking were similar between the two groups. Surgical time, blood loss, blood transfusion, medical cost, post surgery ICU time, hospital day, length of oral pain medicines taken, Pre-and postoperative Oswestry disability index questionnaire and surgical revision were documented and compared. Preoperative, postoperative and final follow up Cobb angle, sagittal lumbar curve, correction rate, and Follow up Cobb loss were also compared. No significant differences were found between the autogenous bone group and polymethylmethacrylate group with regards to all the targets above except for length of oral pain medicines taken and surgery cost. 2 patients were seen leakage during operation, but there is neither damage of nerve nor symptom after operation. No revision was needed. Both augmentation pedicle screw with polymethylmethacrylate (PMMA) and autogenous bone treating degenerative lumbar scoliosis combined with osteoporosis can achieve a good surgical result. Less oral pain medicines taken are the potential benefits of polymethylmethacrylate augmentation, but that is at the cost of more medical spending.

A comparison of screw insertion torque and pullout strength.

PubMed

Ricci, William M; Tornetta, Paul; Petteys, Timothy; Gerlach, Darin; Cartner, Jacob; Walker, Zakiyyah; Russell, Thomas A

2010-06-01

Pullout strength of screws is a parameter used to evaluate plate screw fixation strength. However, screw fixation strength may be more closely related to its ability to generate sufficient insertion because stable nonlocked plate-screw fracture fixation requires sufficient compression between plate and bone such that no motion occurs between the plate and bone under physiological loads. Compression is generated by tightening of screws. In osteoporotic cancellous bone, sufficient screw insertion torque may not be generated before screw stripping. The effect of screw thread pitch on generation of maximum insertion torque (MIT) and pullout strength (POS) was investigated in an osteoporotic cancellous bone model and the relationship between MIT and POS was analyzed. Stainless steel screws with constant major (5.0 mm) and minor (2.7 mm) diameters but with varying thread pitches (1, 1.2, 1.5, 1.6, and 1.75 mm) were tested for MIT and POS in a validated osteoporotic surrogate for cancellous bone (density of 160 kg/m(3) [10 lbs/ft(3)]). MIT was measured with a torque-measuring hex driver for screws inserted through a one-third tubular plate. POS was measured after insertion of screws to a depth of 20 mm based on the Standard Specification and Test Methods for Metallic Medical Bone Screws (ASTM F 543-07). Five screws were tested for each failure mode and screw design. The relationship between MIT and compressive force between the plate and bone surrogate was evaluated using pressure-sensitive film. There was a significant difference in mean MIT based on screw pitch (P < 0.0001), whereas POS did not show statistically significant differences among the different screw pitches (P = 0.052). Small screw pitches (1.0 mm and 1.2 mm) had lower MIT and were distinguished from large pitches (1.5 mm, 1.6 mm, and the 1.75 mm) with higher MIT. For POS, only the 1-mm and 1.6-mm pitch screws were found to be different from each other. Linear regression analysis of MIT revealed a moderate

Sagittal plane analysis of selective posterior thoracic spinal fusion in adolescent idiopathic scoliosis: a comparison study of all pedicle screw and hybrid instrumentation.

PubMed

Liu, Tie; Hai, Yong

2014-07-01

To compare sagittal profiles of selective posterior thoracic instrumentation with segmental pedicle screws instrumentation and hybrid (hook and pedicle screw). Nowadays, thoracic screws are considered more effective than other constructs in spinal deformity correction and have become the treatment in adolescent idiopathic scoliosis surgery. However, recent research found that this enhanced correction ability may sacrifice sagittal balance. As lumbar lordosis is dependent upon thoracic kyphosis (TK), it has been important to maintain TK magnitude in selective thoracic fusions to keep balance. There is no sagittal measurement analysis between the hybrid and all-screw constructs type in cases of selective thoracic fusion. All adolescent idiopathic scoliosis (Lenke1) patients surgically treated in our department between 2003 and 2008 were reviewed. Radiographs of these patients, whose preoperative, immediately postoperative, and minimum 2-year follow-up after selective thoracic fusion (lower instrumented vertebrae not lower than L1, hybrid group the pedicle screw instrumentation not higher than T10) were evaluated, 21 patients underwent posterior hybrid instrumentation and 21 underwent pedicle screw instrumentation. No significant difference in sagittal profiles was observed between the 2 groups. At final follow-up, the proximal junctional measurement has a minor increase in both the groups. TK (T5-T12) also increased (+2.0 degrees of increase in hybrid group vs. +3.9 degrees of increase in the pedicle screw group). The effect of different instrumentation in changing TK at various time points between 2 groups was statistic different (P=0.004). Lumbar lordosis (L1-L5) was increased in both the groups. No significant changes in distal junctional measurement and thoracolumbar junction were noted. The C7 sagittal plumbline remained negative in both the groups at the final follow-up. There was no statistically significant difference comparing the sagittal alignment

Surgical strategies to improve fixation in the osteoporotic spine: the effects of tapping, cement augmentation, and screw trajectory.

PubMed

Kuhns, Craig A; Reiter, Michael; Pfeiffer, Ferris; Choma, Theodore J

2014-02-01

Study Design Biomechanical study of pedicle screw fixation in osteoporotic bone. Objective To investigate whether it is better to tap or not tap osteoporotic bone prior to placing a cement-augmented pedicle screw. Methods Initially, we evaluated load to failure of screws placed in cancellous bone blocks with or without prior tapping as well as after varying the depths of tapping prior to screw insertion. Then we evaluated load to failure of screws placed in bone block models with a straight-ahead screw trajectory as well as with screws having a 23-degree cephalad trajectory (toward the end plate). These techniques were tested with nonaugmented (NA) screws as well as with bioactive cement (BioC) augmentation prior to screw insertion. Results In the NA group, pretapping decreased fixation strength in a dose-dependent fashion. In the BioC group, the tapped screws had significantly greater loads to failure (p < 0.01). Comparing only the screw orientation, the screws oriented at 23 degrees cephalad had a significantly higher failure force than their respective counterparts at 0 degrees (p < 0.01). Conclusions Standard pedicle screw fixation is often inadequate in the osteoporotic spine, but this study suggests tapping prior to cement augmentation will substantially improve fixation when compared with not tapping. Angulating screws more cephalad also seems to enhance aging spine fixation.

A multi-level rapid prototyping drill guide template reduces the perforation risk of pedicle screw placement in the lumbar and sacral spine.

PubMed

Merc, Matjaz; Drstvensek, Igor; Vogrin, Matjaz; Brajlih, Tomaz; Recnik, Gregor

2013-07-01

The method of free-hand pedicle screw placement is generally safe although it carries potential risks. For this reason, several highly accurate computer-assisted systems were developed and are currently on the market. However, these devices have certain disadvantages. We have developed a method of pedicle screw placement in the lumbar and sacral region using a multi-level drill guide template, created with the rapid prototyping technology and have validated it in a clinical study. The aim of the study was to manufacture and evaluate the accuracy of a multi-level drill guide template for lumbar and first sacral pedicle screw placement and to compare it with the free-hand technique under fluoroscopy supervision. In 2011 and 2012, a randomized clinical trial was performed on 20 patients. 54 screws were implanted in the trial group using templates and 54 in the control group using the fluoroscopy-supervised free-hand technique. Furthermore, applicability for the first sacral level was tested. Preoperative CT-scans were taken and templates were designed using the selective laser sintering method. Postoperative evaluation and statistical analysis of pedicle violation, displacement, screw length and deviation were performed for both groups. The incidence of cortex perforation was significantly reduced in the template group; likewise, the deviation and displacement level of screws in the sagittal plane. In both groups there was no significantly important difference in deviation and displacement level in the transversal plane as not in pedicle screw length. The results for the first sacral level resembled the main investigated group. The method significantly lowers the incidence of cortex perforation and is therefore potentially applicable in clinical practice, especially in some selected cases. The applied method, however, carries a potential for errors during manufacturing and practical usage and therefore still requires further improvements.

Grading apical vertebral rotation without a computed tomography scan: a clinically relevant system based on the radiographic appearance of bilateral pedicle screws.

PubMed

Upasani, Vidyadhar V; Chambers, Reid C; Dalal, Ali H; Shah, Suken A; Lehman, Ronald A; Newton, Peter O

2009-08-01

Bench-top and retrospective analysis to assess vertebral rotation based on the appearance of bilateral pedicle screws in patients with adolescent idiopathic scoliosis (AIS). To develop a clinically relevant radiographic grading system for evaluating postoperative thoracic apical vertebral rotation that would correlate with computed tomography (CT) measures of rotation. The 3-column vertebral body control provided by bilateral pedicle screws has enabled scoliosis surgeons to develop advanced techniques of direct vertebral derotation. Our ability to accurately quantify spinal deformity in the axial plane, however, continues to be limited. Trigonometry was used to define the relationship between the position of bilateral pedicle screws and vertebral rotation. This relationship was validated using digital photographs of a bench-top model. The mathematical relationships were then used to calculate vertebral rotation from standing postoperative, posteroanterior radiographs in AIS patients and correlated with postoperative CT measures of rotation. Fourteen digital photographs of the bench-top model were independently analyzed twice by 3 coauthors. The mathematically calculated degree of rotation was found to correlate significantly with the actual degree of rotation (r = 0.99; P < 0.001) and the intra- and interobserver reliability for these measurements were both excellent (kappa = 0.98 and kappa = 0.97, respectively). In the retrospective analysis of 17 AIS patients, the average absolute difference between the radiographic measurement of rotation and the CT measure was only 1.9 degrees +/- 2.0 degrees (r = 0.92; P < 0.001). Based on these correlations a simple radiographic grading system for postoperative apical vertebral rotation was developed. An accurate assessment of vertebral rotation can be performed radiographically, using screw lengths and screw tip-to-rod distances of bilateral segmental pedicle screws and a trigonometric calculation. These data support the use

State Recognition of Bone Drilling Based on Acoustic Emission in Pedicle Screw Operation.

PubMed

Guan, Fengqing; Sun, Yu; Qi, Xiaozhi; Hu, Ying; Yu, Gang; Zhang, Jianwei

2018-05-09

Pedicle drilling is an important step in pedicle screw fixation and the most significant challenge in this operation is how to determine a key point in the transition region between cancellous and inner cortical bone. The purpose of this paper is to find a method to achieve the recognition for the key point. After acquiring acoustic emission (AE) signals during the drilling process, this paper proposed a novel frequency distribution-based algorithm (FDB) to analyze the AE signals in the frequency domain after certain processes. Then we select a specific frequency domain of the signal for standard operations and choose a fitting function to fit the obtained sequence. Characters of the fitting function are extracted as outputs for identification of different bone layers. The results, which are obtained by detecting force signal and direct measurement, are given in the paper. Compared with the results above, the results obtained by AE signals are distinguishable for different bone layers and are more accurate and precise. The results of the algorithm are trained and identified by a neural network and the recognition rate reaches 84.2%. The proposed method is proved to be efficient and can be used for bone layer identification in pedicle screw fixation.

Comparison between two pedicle screw augmentation instrumentations in adult degenerative scoliosis with osteoporosis

PubMed Central

2011-01-01

Background The operative treatment of adult degenerative scoliosis combined with osteoporosis increase following the epidemiological development. Studies have confirmed that screws in osteoporotic spines have significant lower-screw strength with more frequent screw movements within the vertebra than normal spines. Screws augmented with Polymethylmethacrylate (PMMA) or with autogenous bone can offer more powerful corrective force and significant advantages. Methods A retrospective analysis was conducted on 31 consecutive patients with degenerative lumbar scoliosis combined with osteoporosis who had surgery from December 2000. All had a minimum of 2-year follow-up. All patients had posterior approach surgery. 14 of them were fixed with pedicle screw by augmentation with Polymethylmethacrylate (PMMA) and the other 17 patients with autogenous bone. Age, sex and whether smoking were similar between the two groups. Surgical time, blood loss, blood transfusion, medical cost, post surgery ICU time, hospital day, length of oral pain medicines taken, Pre-and postoperative Oswestry disability index questionnaire and surgical revision were documented and compared. Preoperative, postoperative and final follow up Cobb angle, sagittal lumbar curve, correction rate, and Follow up Cobb loss were also compared. Results No significant differences were found between the autogenous bone group and Polymethylmethacrylate group with regards to all the targets above except for length of oral pain medicines taken and surgery cost. 2 patients were seen leakage during operation, but there is neither damage of nerve nor symptom after operation. No revision was needed. Conclusion Both augmentation pedicle screw with Polymethylmethacrylate (PMMA) and autogenous bone treating degenerative lumbar scoliosis combined with osteoporosis can achieve a good surgical result. Less oral pain medicines taken are the potential benefits of Polymethylmethacrylate augmentation, but that is at the cost of more

The use of intraoperative triggered electromyography to detect misplaced pedicle screws: a systematic review and meta-analysis.

PubMed

Mikula, Anthony L; Williams, Seth K; Anderson, Paul A

2016-04-01

Insertion of instruments or implants into the spine carries a risk for injury to neural tissue. Triggered electromyography (tEMG) is an intraoperative neuromonitoring technique that involves electrical stimulation of a tool or screw and subsequent measurement of muscle action potentials from myotomes innervated by nerve roots near the stimulated instrument. The authors of this study sought to determine the ability of tEMG to detect misplaced pedicle screws (PSs). The authors searched the U.S. National Library of Medicine, the Web of Science Core Collection database, and the Cochrane Central Register of Controlled Trials for PS studies. A meta-analysis of these studies was performed on a per-screw basis to determine the ability of tEMG to detect misplaced PSs. Sensitivity, specificity, and receiver operating characteristic (ROC) area under the curve (AUC) were calculated overall and in subgroups. Twenty-six studies were included in the systematic review. The authors analyzed 18 studies in which tEMG was used during PS placement in the meta-analysis, representing data from 2932 patients and 15,065 screws. The overall sensitivity of tEMG for detecting misplaced PSs was 0.78, and the specificity was 0.94. The overall ROC AUC was 0.96. A tEMG current threshold of 10-12 mA (ROC AUC 0.99) and a pulse duration of 300 µsec (ROC AUC 0.97) provided the most accurate testing parameters for detecting misplaced screws. Screws most accurately conducted EMG signals (ROC AUC 0.98). Triggered electromyography has very high specificity but only fair sensitivity for detecting malpositioned PSs.

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. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Comparing Uniplanar and Multiaxial Pedicle Screws in the Derotation of Apical Vertebrae for Lenke V Adolescent Idiopathic Scoliosis: A Case-Controlled Study.

PubMed

Lin, Tao; Li, Tangbo; Jiang, Heng; Ma, Jun; Zhou, Xuhui

2018-03-01

To compare effects of uniplanar and multiaxial pedicle screws on apical vertebral derotation efficiency in patients with Lenke V adolescent idiopathic scoliosis. For this retrospective study, patients with Lenke V adolescent idiopathic scoliosis with uniplanar pedicle screws (group I) and multiaxial pedicle screws (group II) were collected from January 2013 to December 2015. Grade of apical vertebral rotation was evaluated before and after surgery using the Nash-Moe and Upasani methods, respectively. The Scoliosis Research Society-22 scale was also used to evaluate patient satisfaction. There were no significant differences in terms of age, duration of follow-up, correction ratio, and preoperative level of apical rotation between groups (P < 0.05). Group I showed better apical vertebral derotation than group II (level 0, 10.5% vs. 2.3%; level I, 71.1% vs. 38.6%; level II, 18.4% vs. 59.1%; P = 0.001). The progression group showed lower bone maturity (odds ratio 52.0; 95% confidence interval, 6.3-430.7; P < 0.0001) in group I, and similar results were observed in group II (OR 12.3; 95% confidence interval, 1.3-121.3; P = 0.057). Patients in group I showed better satisfaction than patients in group II based on Scoliosis Research Society-22 scores (P < 0.05). Both types of pedicle screws could provide effective correction, but the uniplanar pedicle screw was better for derotation of vertebrae and provided patients with better satisfaction. Skeleton immaturity was positively correlated with progression of vertebral rotation after surgery. Copyright © 2017 Elsevier Inc. All rights reserved.

Timing of PMMA cement application for pedicle screw augmentation affects screw anchorage.

PubMed

Schmoelz, Werner; Heinrichs, Christian Heinz; Schmidt, Sven; Piñera, Angel R; Tome-Bermejo, Felix; Duart, Javier M; Bauer, Marlies; Galovich, Luis Álvarez

2017-11-01

Cement augmentation is an established method to increase the pedicle screw (PS) anchorage in osteoporotic vertebral bodies. The ideal timing for augmentation when a reposition maneuver is necessary is controversial. While augmentation of the PS before reposition maneuver may increase the force applied it on the vertebrae, it bears the risk to impair PS anchorage, whereas augmenting the PS after the maneuver may restore this anchorage and prevent early screw loosening. The purpose of the present study was to evaluate the effect of cement application timing on PS anchorage in the osteoporotic vertebral body. Ten lumbar vertebrae (L1-L5) were used for testing. The left and right pedicles of each vertebra were instrumented with the same PS size and used for pairwise comparison of the two timing points for augmentation. For the reposition maneuver, the left PS was loaded axially under displacement control (2 × ±2 mm, 3 × ±6 mm, 3 × ±10 mm) to simulate a reposition maneuver. Subsequently, both PS were augmented with 2 ml PMMA cement. The same force as measured during the left PS maneuver was applied to the previously augmented right hand side PS [2 × F (±2 mm), 3 × F (±6 mm), 3 × F (±10 mm)]. Both PS were cyclically loaded with initial forces of +50 and -50 N, while the lower force was increased by 5 N every 100 cycles until total failure of the PS. The PS motion was measured with a 3D motion analysis system. After cyclic loading stress, X-rays were taken to identify the PS loosening mechanism. In comparison with PS augmented prior to the reposition maneuver, PS augmented after the reposition maneuver showed a significant higher number of load cycles until failure (5930 ± 1899 vs 3830 ± 1706, p = 0.015). The predominant loosening mechanism for PS augmented after the reposition maneuver was PS toggling with the attached cement cloud within the trabecular bone. While PS augmented prior to the reposition, maneuver showed a motion of

Neurovascular risks of sacral screws with bicortical purchase: an anatomical study.

PubMed

Ergur, Ipek; Akcali, Omer; Kiray, Amac; Kosay, Can; Tayefi, Hamid

2007-09-01

The aim of this cadaver study is to define the anatomic structures on anterior sacrum, which are under the risk of injury during bicortical screw application to the S1 and S2 pedicles. Thirty formaldehyde-preserved human male cadavers were studied. Posterior midline incision was performed, and soft tissues and muscles were dissected from the posterior part of the lumbosacral region. A 6 mm pedicle screw was inserted between the superior facet of S1 and the S1 foramen. The entry point of the S2 pedicle screw was located between S1 and S2 foramina. S1 and S2 screws were placed on both right and the left sides of all cadavers. Then, all cadavers were turned into supine position. All abdominal and pelvic organs were moved away and carefully observed for any injury. The tips of the sacral screws were marked and the relations with the anatomic structures were defined. The position of the sacral screws relative to the middle and lateral sacral arteries and veins, and the sacral sympathetic trunk were measured. There was no injury to the visceral organs. In four cases, S1 screw tip was in direct contact with middle sacral artery. In two cases, S1 screw tip was in direct contact with middle sacral vein. It was observed that the S1 screw tips were in close proximity to sacral sympathetic trunk on both right and the left sides. The tip of the S2 screw was in contact with middle sacral artery on the left side only in one case. It is found that the tip of the S2 screw was closely located with the middle sacral vein in two cases. The tip of the S2 pedicle screw was in contact with the sacral sympathetic trunk in eight cases on the right side and seven cases on the left side. Lateral sacral vein was also observed to be disturbed by the S1 and S2 screws. As a conclusion, anterior cortical penetration during sacral screw insertion carries a risk of neurovascular injury. The risk of sacral sympathetic trunk and minor vascular structures together with the major neurovascular

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

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

Comparison of success rates of orthodontic mini-screws by the insertion method.

PubMed

Kim, Jung Suk; Choi, Seong Hwan; Cha, Sang Kwon; Kim, Jang Han; Lee, Hwa Jin; Yeom, Sang Seon; Hwang, Chung Ju

2012-10-01

The aim of this study was to compare the success rates of the manual and motor-driven mini-screw insertion methods according to age, gender, length of mini-screws, and insertion sites. We retrospectively reviewed 429 orthodontic mini-screw placements in 286 patients (102 in men and 327 in women) between 2005 and 2010 at private practice. Age, gender, mini-screw length, and insertion site were cross-tabulated against the insertion methods. The Cochran-Mantel-Haenszel test was performed to compare the success rates of the 2 insertion methods. The motor-driven method was used for 228 mini-screws and the manual method for the remaining 201 mini-screws. The success rates were similar in both men and women irrespective of the insertion method used. With respect to mini-screw length, no difference in success rates was found between motor and hand drivers for the 6-mm-long mini-screws (68.1% and 69.5% with the engine driver and hand driver, respectively). However, the 8-mm-long mini-screws exhibited significantly higher success rates (90.4%, p < 0.01) than did the 6-mm-long mini-screws when placed with the engine driver. The overall success rate was also significantly higher in the maxilla (p < 0.05) when the engine driver was used. Success rates were similar among all age groups regardless of the insertion method used. Taken together, the motor-driven insertion method can be helpful to get a higher success rate of orthodontic mini-screw placement.

[Evaluation of the risk of mediastinal or retroperitoneal injuries caused by dorso-lumbar pedicle screws].

PubMed

Hernigou, P; Germany, W

1998-09-01

Within an anatomical and a clinical study, the authors employed computerized tomographic scans to evaluate the risks of anterior surrounding tissues injuries during screw insertion. CT scans of 20 patients suffering from cardiac disease were reviewed retrospectively. Scans through the thoracic and lumbar spine were obtained using 6 mm slice thickness. These examinations were performed with intravenous contrast medium. Measurements of vessel diameters and distance of the soft tissues situated directly anterior to the spine were done. A retrospective study of 61 pedicle screws implanted for spine fractures evaluated the penetration of the anterior vertebral cordex with X rays and CT scans. Computerized tomographic scans of the thoracic and lumbar spine of the 20 patients in the control group confirmed proximity of the posterior mediastinal structures to the anterior vertebral cortex. Many structures of the posterior mediastinum were within five millimeters of the anterior vertebral cortex and thus were at risk: aorta, azygos vein, vena cava, parietal pleura and lungs. The theoretical risk of unrecognized screw penetrations evaluated on geometric shape of the anterior vertebral body is as high as 21 per cent when screw position is only seen with an antero posterior and a lateral X Ray. In the other group, computerized tomographic scans showed that 30 per cent of the implanted screws were outside the boundaries of the anterior thoracic spine. Two orthogonal incidences do not enable determination of whether the extremity of the screw is slightly outside the anterior cortex of the vertebral body. However the geometric shape of the anterior vertebral body enables peroperative definition of a safety zone on two orthogonal incidences. Even if a breach of a few millimeters of the anterior cortical boundaries of the vertebral body may not initially damage the adjacent soft-tissue structures, chronic irritation may result in late damages of these structures. The use of

Temporary Percutaneous Pedicle Screw Stabilization Without Fusion of Adolescent Thoracolumbar Spine Fractures.

PubMed

Cui, Shari; Busel, Gennadiy A; Puryear, Aki S

2016-01-01

Pediatric spine trauma often results from high-energy mechanisms. Despite differences in healing potential, comorbidities, and length of remaining life, treatment is frequently based on adult criteria; ligamentous injuries are fused and bony injuries are treated accordingly. In this study, we present short-term results of a select group of adolescent patients treated using percutaneous pedicle screw instrumentation without fusion. An IRB-approved retrospective review was performed at a level 1 pediatric trauma center for thoracolumbar spine fractures treated by percutaneous pedicle screw instrumentation. Patients were excluded if arthrodesis was performed or if instrumentation was not removed. Demographics, injury mechanism, associated injuries, fracture classification, surgical data, radiographic measures, and complications were collected. Radiographs were analyzed for sagittal and coronal wedge angles and vertebral body height ratio and statistical comparisons performed on preoperative and postoperative values. Between 2005 and 2013, 46 patients were treated surgically. Fourteen patients (5 male, 9 female) met inclusion criteria. Injury mechanisms included 8 motor vehicle collisions, 4 falls, and 2 all-terrain vehicle/motorcycle collisions. There were 8 Magerl type A injuries, 4 type B injuries, and 2 type C injuries. There was 1 incomplete spinal cord injury. Implants were removed between 5 and 12 months in 12 patients and after 12 months in 2 patients. Statistical analysis revealed significant postoperative improvement in all radiographic measures (P<0.05). There were no neurological complications, 1 superficial wound dehiscence, and 2 instrumentation failures (treated with standard removal). At last follow-up, 11 patients returned to unrestricted activities including sports. Average follow-up was 9 months after implant removal and 19.3 months after index procedure. Adolescent thoracolumbar fractures present unique challenges and treatment opportunities

Management of major vascular injury during pedicle screw instrumentation of thoracolumbar spine.

PubMed

Mirza, Aleem K; Alvi, Mohammed Ali; Naylor, Ryan M; Kerezoudis, Panagiotis; Krauss, William E; Clarke, Michelle J; Shepherd, Daniel L; Nassr, Ahmad; DeMartino, Randall R; Bydon, Mohamad

2017-12-01

Vascular injury is a rare complication of spinal instrumentation. Presentation can vary from immediate hemorrhage to pseudoaneurysm formation. In the literature, surgical approach to repair has varied based on anatomy, acuity of diagnosis, infection, and available technology. In this manuscript, we aim to describe our institutional experience with vascular injuries in thoraco-lumbar spine surgery. We report our institutional experience of three cases of vascular injury secondary to pedicle screw misplacement and their management, as well as a review of the literature. The first case had a history of previous instrumentation and presented with back pain and fever. The patient was taken for instrumentation exploration via a posterior approach. Aortic violation was discovered at T6 intraoperatively during instrumentation removal and the patient underwent emergent endovascular repair. The second case presented with chronic back pain after multiple prior posterior fusions and CT angiogram showing screw perforation on the aorta at T10. The patient underwent elective endovascular repair with synchronous removal of the instrumentation. The third case presented with radicular leg pain 6 months after L4-S1 posterior lumbar interbody fusion, with CT scan demonstrating the left S1 screw abutting the L5 nerve root and common iliac vein. The patient underwent elective instrumentation revision with intraoperative venography. Major vascular injury is a known complication of spinal surgery, especially if it involves instrumentation with pedicle screws. Treatment approach has evolved with the advancement of endovascular technology; however, open surgery remains an option when anatomy or infection is prohibitive. In the elective setting, preoperative planning with attention to surgical approach, positioning, and contingencies, should occur in a multidisciplinary fashion. Repair with an aortic stent-graft cuff may minimize unnecessary coverage of the descending thoracic aorta and

Accuracy of pedicle screw placement comparing robot-assisted technology and the free-hand with fluoroscopy-guided method in spine surgery: An updated meta-analysis.

PubMed

Fan, Yong; Du, Jin Peng; Liu, Ji Jun; Zhang, Jia Nan; Qiao, Huan Huan; Liu, Shi Chang; Hao, Ding Jun

2018-06-01

A miniature spine-mounted robot has recently been introduced to further improve the accuracy of pedicle screw placement in spine surgery. However, the differences in accuracy between the robotic-assisted (RA) technique and the free-hand with fluoroscopy-guided (FH) method for pedicle screw placement are controversial. A meta-analysis was conducted to focus on this problem. Several randomized controlled trials (RCTs) and cohort studies involving RA and FH and published before January 2017 were searched for using the Cochrane Library, Ovid, Web of Science, PubMed, and EMBASE databases. A total of 55 papers were selected. After the full-text assessment, 45 clinical trials were excluded. The final meta-analysis included 10 articles. The accuracy of pedicle screw placement within the RA group was significantly greater than the accuracy within the FH group (odds ratio 95%, "perfect accuracy" confidence interval: 1.38-2.07, P < .01; odds ratio 95% "clinically acceptable" Confidence Interval: 1.17-2.08, P < .01). There are significant differences in accuracy between RA surgery and FH surgery. It was demonstrated that the RA technique is superior to the conventional method in terms of the accuracy of pedicle screw placement.

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.

Radiographic Analysis of One-level Minimally Invasive Transforaminal Lumbar Interbody Fusion (MI-TLIF) With Unilateral Pedicle Screw Fixation for Lumbar Degenerative Diseases.

PubMed

Shen, Xiaolong; Wang, Lei; Zhang, Hailong; Gu, Xin; Gu, Guangfei; He, Shisheng

2016-02-01

A prospective randomized study was conducted. The purpose of this study was to assess the radiographic outcomes of one-level minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) with unilateral pedicle screw instrumentation for degenerative lumbar spine disease. MI-TLIF has become an increasingly popular method of lumbar arthrodesis. Recent technological advances in spinal instrumentation have culminated in the development of MI-TLIF with unilateral pedicle screw fixation. However, there are few published studies on radiographic outcomes of the MI-TLIF with unilateral pedicle screw fixation. A total of 65 patients with one-level degenerative lumbar spine disease were enrolled in this study. Patients were randomized into the unilateral or bilateral fixation group based on a computer-generated number list. Thirty-one patients (17 men and 14 women; average age, 57.3 y) were randomized to the unilateral group (group A) and 34 patients (16 men and 18 women; average age, 58.9 y) to the bilateral group (group B). All patients underwent minimally invasive decompression, interbody fusion, and pedicle screw fixation with the assistance of microscopic tubular retractor system (METRx-MD) and Sextant system. All patients were asked to follow-up at 3, 6, and thereafter once every 6 months after surgery. The visual analog scale (VAS), Oswestry disability index (ODI), and modified Prolo (mProlo) scores were obtained for all patients 24 hours before the operation and at each follow-up visit. The whole lumbar lordosis (WL), the segmental lordosis (SL), fusion level disk space angle, lumbar scoliosis angle, and segmental scoliosis angle were determined before and after surgery on standard x-rays. The disk height index (DI) and the lumber curvature index (LI) were also evaluated. The mean follow-up was 26.6 months, with a range of 18-36 months. All patients showed evidence of fusion at 12 months postoperatively. Statistically, there was no significant difference between

Hounsfield unit of screw trajectory as a predictor of pedicle screw loosening after single level lumber interbody fusion.

PubMed

Sakai, Yusuke; Takenaka, Shota; Matsuo, Yohei; Fujiwara, Hiroyasu; Honda, Hirotsugu; Makino, Takahiro; Kaito, Takashi

2018-06-01

This study aims to clarify the clinical potential of Hounsfield unit (HU), measured on computed tomography (CT) images, as a predictor of pedicle screw (PS) loosening, compared to bone mineral density (BMD). A total of 206 screws in 52 patients (21 men and 31 women; mean age 68.2 years) were analyzed retrospectively. The screws were classified into two groups depending on their screw loosening status on 3-month follow-up CT (loosening screw group vs. non-loosening screw group). Preoperative HU of the trajectory was evaluated by superimposing preoperative and postoperative CT images using three-dimensional image analysis software. Age, sex, body mass index, screw size, BMD of lumbar, and HU of screw trajectory were analyzed in association with screw loosening. Multivariate logistic regression analysis was performed, and the thresholds for PS loosening risk factors were evaluated using a continuous numerical variable and receiver operating characteristic (ROC) curve analyses. The area under the curve (AUC) was used to determine the diagnostic performance, and values > 0.75 were considered to represent good performance. The loosening screw group contained 24 screws (12%). Multivariate analysis revealed that the significant independent risk factors were not BMD but male sex [P = 0.028; odds ratio (OR) 2.852, 95% confidence interval (CI) 1.120-7.258] and HU of screw trajectory (P = 0.006; OR 0.989, 95% CI 0.980-0.997). ROC curve analysis demonstrated that the AUC for HU of screw trajectory for women was 0.880 (95% CI 0.798-0.961). The cutoff value was 153.5. AUC for men was 0.635 (95% CI 0.449-0.821), which was not considered to be a good performance. Low HU of screw trajectories was identified as a risk factor of PS loosening for women. For female patients with low HU, additional augmentation is recommended to prevent PS loosening. Copyright © 2018 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

Sagittal imbalance treated with L5 pedicle subtraction osteotomy with short lumbar fusion from L4 to sacrum using four screws into L4 for enhanced fixation two additional vertebral screws: a technical note.

PubMed

Wangdi, Kuenzang; Otsuki, Bungo; Fujibayashi, Shunsuke; Tanida, Shimei; Masamoto, Kazutaka; Matsuda, Shuichi

2018-02-07

To report on suggested technique with four screws in a single vertebra (two pedicle screws and two direct vertebral body screws) for enhanced fixation with just one level cranially to a pedicle subtraction osteotomy (PSO). A 60-year-old woman underwent L4/5 fusion surgery for degenerative spondylolisthesis. Two years later, she was unable to stand upright even for a short time because of lumbar kyphosis caused by subsidence of the fusion cage and of Baastrup syndrome in the upper lumbar spine [sagittal vertical axis (SVA) of 114 mm, pelvic incidence of 75°, and lumbar lordosis (LL) of 41°]. She underwent short-segment fusion from L4 to the sacrum with L5 pedicle subtraction osteotomy. We reinforced the construct with two vertebral screws at L4 in addition to the conventional L4 pedicle screws. After the surgery, her sagittal parameters were improved (SVA, 36 mm; LL, 54°). Two years after the corrective surgery, she maintained a low sagittal vertical axis though high residual pelvic tilt indicated that the patient was still compensating for residual sagittal misalignment. PSO surgery for sagittal imbalance usually requires a long fusion at least two levels above and below the osteotomy site to achieve adequate stability and better global alignment. However, longer fixation may decrease the patients' quality of life and cause a proximal junctional failure. Our novel technique may shorten the fixation area after osteotomy surgery. These slides can be retrieved under Electronic Supplementary Material.

Screw-Thread Inserts As Temporary Flow Restrictors

NASA Technical Reports Server (NTRS)

Trimarchi, Paul

1992-01-01

Coil-spring screw-thread inserts found useful as temporary flow restrictors. Inserts placed in holes through which flow restricted, effectively reducing cross sections available for flow. Friction alone holds inserts against moderate upstream pressures. Use of coil-spring thread inserts as flow restrictors conceived as inexpensive solution to problem of adjusting flow of oxygen through orifices in faceplate into hydrogen/oxygen combustion chamber. Installation and removal of threaded inserts gentle enough not to deform orifice tubes.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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)more » 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.« less

[The Effect of Intraoperative Screw Monitoring (Root Monitoring) with the INS-1 System (NUVASIVE) on the Radiological Outcome of Dorsal Instrumentation of the Lumbar Spine].

PubMed

Bernhardt, G; Awiszus, F; Meister, U; Heyde, C E; Böhm, H

2016-06-01

Transpedicular screw fixation of spinal segments has been described for a variety of surgical indications and is a key element in spinal surgery. The aim of transpedicular screw fixation is to achieve maximal stability. Screw malposition should be obviated to avoid neurological complications. There are published methods of applying evoked EMG to control screw position in relation to neural structures. These studies demonstrated that an intact bony pedicle wall acts as an electrical isolator between the screw and spinal nerve root. The aim of our study was to evaluate the impact of intraoperative pedicle screw monitoring on screw positioning. We enrolled 22 patients in this prospective randomised study, who underwent spinal instrumentation after being split into two equal groups. In the first group, dorsal instrumentation was supplemented with intraoperative nerve root monitoring using the INS-1-System (NuVasive, San Diego USA). In the second group, screws were inserted without additional pedicle monitoring. All patients underwent monosegmental instrumentation with "free hand implanted" pedicle screws. 44 screws were inserted in each group. The screw position was evaluated postoperatively using CT scans. The position of the screws in relation to the pedicle was measured in three different planes: sagittal, axial and coronal. The accuracy of the screw position was described using the Berlemann classification system. Screw position is classified in three groups: type 1 correct screw position, type 2 encroachment on the inner cortical wall, type 3 pedicle cortical perforation. Screw angulation and secondary operative criteria were also evaluated. The use of neuromonitoring did not influence the distance between the centre of the screws and the pedicle wall. Distances only depended on the implantation side (right and left) and the height of implantation (caudal or cranial screw). Because of the low number of cases, no conclusion could be reached about the influence of

Pullout characteristics of percutaneous pedicle screws with different cement augmentation methods in elderly spines: An in vitro biomechanical study.

PubMed

Charles, Y P; Pelletier, H; Hydier, P; Schuller, S; Garnon, J; Sauleau, E A; Steib, J-P; Clavert, P

2015-05-01

Vertebroplasty prefilling or fenestrated pedicle screw augmentation can be used to enhance pullout resistance in elderly patients. It is not clear which method offers the most reliable fixation strength if axial pullout and a bending moment is applied. The purpose of this study is to validate a new in vitro model aimed to reproduce a cut out mechanism of lumbar pedicle screws, to compare fixation strength in elderly spines with different cement augmentation techniques and to analyze factors that might influence the failure pattern. Six human specimens (82-100 years) were instrumented percutaneously at L2, L3 and L4 by non-augmented screws, vertebroplasty augmentation and fenestrated screws. Cement distribution (2 ml PMMA) was analyzed on CT. Vertebral endplates and the rod were oriented at 45° to the horizontal plane. The vertebral body was held by resin in a cylinder, linked to an unconstrained pivot, on which traction (10 N/s) was applied until rupture. Load-displacement curves were compared to simultaneous video recordings. Median pullout forces were 488.5 N (195-500) for non-augmented screws, 643.5 N (270-1050) for vertebroplasty augmentation and 943.5 N (750-1084) for fenestrated screws. Cement augmentation through fenestrated screws led to significantly higher rupture forces compared to non-augmented screws (P=0.0039). The pullout force after vertebroplasty was variable and linked to cement distribution. A cement bolus around the distal screw tip led to pullout forces similar to non-augmented screws. A proximal cement bolus, as it was observed in fenestrated screws, led to higher pullout resistance. This cement distribution led to vertebral body fractures prior to screw pullout. The experimental setup tended to reproduce a pullout mechanism observed on radiographs, combining axial pullout and a bending moment. Cement augmentation with fenestrated screws increased pullout resistance significantly, whereas the fixation strength with the vertebroplasty

A 3D navigation template for guiding a unilateral lumbar pedicle screw with contralateral translaminar facet screw fixation: a study protocol for multicentre randomised controlled trials.

PubMed

Shao, Zhen-Xuan; He, Wei; He, Shao-Qi; Lin, Sheng-Lei; Huang, Zhe-Yu; Tang, Hong-Chao; Ni, Wen-Fei; Wang, Xiang-Yang; Wu, Ai-Min

2017-07-21

The incidence of lumbar disc degeneration disease has increased in recent years. Lumbar interbody fusion using two unilateral pedicle screws and a translaminar facet screw fixation has advantages of minimal invasiveness and lower costs compared with the traditional methods. Moreover, a method guided by a three-dimensional (3D) navigation template may help us improve the surgical accuracy and the success rate. This is the first randomised study using a 3D navigation template to guide a unilateral lumbar pedicle screw with contralateral translaminar facet screw fixation. Patients who meet the criteria of the surgery will be randomly divided into experimental groups and control groups by a computer-generated randomisation schedule. We will preoperatively design an individual 3D navigation template using CATIA software and MeditoolCreate. The following primary outcomes will be collected: screw angles compared with the optimal screw trajectories in 3D digital images, length of the wound incision, operative time, intraoperative blood loss and complications. The following secondary outcomes will be collected: visual analogue scale (VAS) for back pain, VAS for leg pain and the Oswestry Disability Index. These parameters will be evaluated on day 1 and then 3, 6, 12 and 24 months postoperatively. The study has been reviewed and approved by the institutional ethics review board of the Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University. The results will be presented at scientific communities and peer-reviewed journals. ChiCTR-IDR-17010466. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Predictive validity of preoperative CT scans and the risk of pedicle screw loosening in spinal surgery.

PubMed

Bredow, Jan; Boese, C K; Werner, C M L; Siewe, J; Löhrer, L; Zarghooni, K; Eysel, P; Scheyerer, M J

2016-08-01

Pedicle screw fixation is the standard technique for the stabilization of the spine, a clinically relevant complication of which is screw loosening. This retrospective study investigates whether preoperative CT scanning can offer a predictor of screw loosening. CT-scan attenuation in 365 patients was evaluated to determine the mean bone density of each vertebral body. Screw loosening or dislocation was determined in CT scans postoperatively using the standard radiological criteria. Forty-five of 365 patients (12.3 %; 24 male, 21 female) suffered postoperative screw loosening (62 of 2038 screws) over a mean follow-up time of 50.8 months. Revision surgeries were necessary in 23 patients (6.3 %). The correlation between decreasing mean CT attenuation in Hounsfield Units (HU) and increasing patient age was significant (p < 0.001). Mean bone density was 116.3 (SD 53.5) HU in cases with screw loosening and 132.7 (SD 41.3) HU in cases in which screws remained fixed. The difference was statistically significant (p = 0.003). The determination of bone density with preoperative CT scanning can predict the risk of screw loosening and inform the decision to use cement augmentation to reduce the incidence of screw loosening.

Segmental Pedicle Screw Instrumentation and Fusion Only to L5 in the Surgical Treatment of Flaccid Neuromuscular Scoliosis.

PubMed

Takaso, Masashi; Nakazawa, Toshiyuki; Imura, Takayuki; Fukuda, Michinari; Takahashi, Kazuhisa; Ohtori, Seiji

2018-03-01

A retrospective cohort study was performed. The purpose of this study was to determine the efficacy and safety of stopping segmental pedicle screw instrumentation constructs at L5 in the treatment of neuromuscular scoliosis. Duchenne muscular dystrophy and spinal muscular atrophy are flaccid neuromuscular disorders in which gradual deterioration is the hallmark and have a lot of characteristics in common despite differences in etiology. Instrumentation and fusion to the sacrum/pelvis has been a mainstay in the surgical treatment of flaccid neuromuscular scoliosis and recommended to correct pelvic obliquity. However, the caudal extent of instrumentation and fusion in the surgical treatment of flaccid neuromuscular scoliosis has remained a matter of considerable debate and there have been few studies on the use of segmental pedicle screw instrumentation for flaccid neuromuscular scoliosis. From 2005 to 2007, a total of 27 consecutive patients with neuromuscular disorders (20 Duchenne muscular dystrophy and 7 spinal muscular atrophy), aged 11 to 17 years, underwent segmental pedicle screw instrumentation and fusion only to L5. Assessment was performed clinically and with radiologic measurements. Minimum 2-year follow-up was required for inclusion in this study. Twenty patients were enrolled in this study. No patient was lost to follow-up. All patients had L5 tilt of less than 15° and a coronal curve with apex L2 or higher preoperatively. Preoperative coronal curve averaged 70° (range: 51°-88°), with a postoperative mean of 15° (range: 5°-25°) and 17° (range: 6°-27°) at the last follow-up. The pelvic obliquity improved from 15° (range: 9°-25°) preoperatively to 5° (range: 3°-8°) postoperatively and 6° (range: 3°-8°) at the last follow-up. The L5 tilt improved from 9° (range: 2°-14°) preoperatively to 2° (range: 0°-4°) postoperatively and 2° (range: 0°-5°) at the last follow-up. Physiologic sagittal plane alignment was recreated after surgery

[Therapeutic observation of subcutaneous pedicle screw-rod system with modified placement for Tile B pelvic fractures].

PubMed

Wu, Xiao-Tian; Chen, Nong; Pan, Fu-Gen; Liu, Zuo-Qing; He, Xiao-Jian

2017-03-25

To investigate the feasibility and therapeutic effect of subcutaneous pedicle screw-rod system with modified placement in treatment of Tile B pelvic fractures. From June 2014 to August 2015, 14 patients with Tile B pelvic fractures were treated by subcutaneous pedicle screw-rod system with modified placement in the anterior inferior iliac spine and pubic tubercle. There were 8 males and 6 females, aged from 23 to 65 years with an average of 42 years. Operative time, intraoperative blood loss, fracture healing and postoperative complication were observed and clinical effects were evaluated by Matta reduction standard and Majeed score. All patients were followed up from 8 to 15 months with an average of 10.5 months. Operative time was 25 to 45 min with an average of 32 min;intraoperative blood loss was 10 to 35 ml with an average of 18 ml. All fractures got primary healing and healed time was 9 to 14 weeks with an average of 12.5 weeks. No postoperative incision infection, internal fixation failure and ectopic ossification were found, 4 cases occurred unilateral lateral femoral cutaneous nerve injury and 1 case occurred unilateral femoral nerve paralysis, but all restored finally. According to Matta criteria, reduction was excellent in 7 cases, good in 5 cases, fair in 2 case. According to Majeed score system, the functional evaluation at last follow-up was excellent in 5 cases, good in 7 cases, fair in 2 cases with the average score of 81.50±8.05. Subcutaneous pedicle screw-rod system with modified placement in the anterior inferior iliac spine and pubic tubercle have advantages of strong reduction, less trauma and complications, and is a promising surgical method in the treatment of Tile B pelvic fractures.

[Direct repair of adolescent lumbar spondylolysis using a pedicle screw-laminar hook system by paramedian approach].

PubMed

Wang, Bin; Tang, Yong-hua; Tang, Hong-chao; Jin, Cai-yi

2011-08-01

To discuss the indication and clinical effect of direct repair of adolescent lumbar spondylolysis by screw-laminar hook system. From August 2003 to December 2008, 28 patients (13 males and 15 females,ranging in age from 15 and 26 years, averaged 21.6 years) with lumbar spondylolysis were treated with isthmic bone grafting and internal fixation with a pedicle screw-laminar hook system. Three patients had spondylolysis at L3, L4; 5 patients had spondylolysis at L4, L5; 8 patients had spondylolysis at L4; and 12 patients had spondylolysis at L5. All the patients had low back pain and lasted over 6 months. According to preoperative and postoperative plain radiograph, CT scan and Macnab criteria, the fusion rate and clinical effect of this technique were evaluated. All the patients were followed up with a mean period of 14.9 months, ranging from 9 to 24 months. All the patients had bony union according to the X-rays and CT scan. According to the calculation results of Macnab criteria, 22 patients got an excellent result, 5 good and 1 fair. The direct repair of adolescent lumbar spondylolysis with pedicle screw-laminar hook system can shorten length of operation,decrease blood loss, preserve more posterior structures of spine and avoid iatrogenic instability of spine. The postoperative immediate stability of vertebral segment is acquired and the mobility of adjacent intervertebral discs is reserved. The screw-laminar hook system for the treatment of adolescent spondylolisthesis can get satisfactory clinical results.

[Clinical application of accurate placement of lumbar pedicle screws using three-dimensional printing navigational templates under Quadrant system].

PubMed

Chen, Xuanhuang; Yu, Zhengxi; Wu, Changfu; Li, Xing; Chen, Xu; Zhang, Guodong; Zheng, Zugao; Lin, Haibin

2017-02-01

To explore the feasibility and the effectiveness of the accurate placement of lumbar pedicle screws using three-dimensional (3D) printing navigational templates in Quadrant minimally invasive system. The L 1-5 spines of 12 adult cadavers were scanned using CT. The 3D models of the lumbar spines were established. The screw trajectory was designed to pass through the central axis of the pedicle by using Mimics software. The navigational template was designed and 3D-printed according to the bony surface where the soft tissues could be removed. The placed screws were scanned using CT to create the 3D model again after operation. The 3D models of the designed trajectory and the placed screws were registered to evaluate the placed screws coincidence rate. Between November 2014 and November 2015, 31 patients with lumbar instability accepted surgery assisted with 3D-printing navigation module under Quadrant minimally invasive system. There were 14 males and 17 females, aged from 42 to 60 years, with an average of 45.2 years. The disease duration was 6-13 months (mean, 8.8 months). Single segment was involved in 15 cases, two segments in 13 cases, and three segments in 3 cases. Preoperative visual analogue scale (VAS) was 7.59±1.04; Oswestry disability index (ODI) was 76.21±5.82; and the Japanese Orthopaedic Association (JOA) score was 9.21±1.64. A total of 120 screws were placed in 12 cadavers specimens. The coincidence rate of placed screw was 100%. A total of 162 screws were implanted in 31 patients. The operation time was 65-147 minutes (mean, 102.23 minutes); the intraoperative blood loss was 50-116 mL (mean, 78.20 mL); and the intraoperative radiation exposure time was 8-54 seconds (mean, 42 seconds). At 3-7 days after operation, CT showed that the coincidence rate of the placed screws was 98.15% (159/162). At 4 weeks after operation, VAS, ODI, and JOA score were 2.24±0.80, 29.17±2.50, and 23.43±1.14 respectively, showing significant differences when compared

Short segment pedicle screw instrumentation and augmentation vertebroplasty in lumbar burst fractures: an experience

PubMed Central

Akbar, Saleem; Dhar, Shabir A.

2008-01-01

To assess the efficacy and feasibility of vertebroplasty and posterior short-segment pedicle screw fixation for the treatment of traumatic lumbar burst fractures. Short-segment pedicle screw instrumentation is a well described technique to reduce and stabilize thoracic and lumbar spine fractures. It is relatively a easy procedure but can only indirectly reduce a fractured vertebral body, and the means of augmenting the anterior column are limited. Hardware failure and a loss of reduction are recognized complications caused by insufficient anterior column support. Patients with traumatic lumbar burst fractures without neurologic deficits were included. After a short segment posterior reduction and fixation, bilateral transpedicular reduction of the endplate was performed using a balloon, and polymethyl methacrylate cement was injected. Pre-operative and post-operative central and anterior heights were assessed with radiographs and MRI. Sixteen patients underwent this procedure, and a substantial reduction of the endplates could be achieved with the technique. All patients recovered uneventfully, and the neurologic examination revealed no deficits. The post-operative radiographs and magnetic resonance images demonstrated a good fracture reduction and filling of the bone defect without unwarranted bone displacement. The central and anterior height of the vertebral body could be restored to 72 and 82% of the estimated intact height, respectively. Complications were cement leakage in three cases without clinical implications and one superficial wound infection. Posterior short-segment pedicle fixation in conjunction with balloon vertebroplasty seems to be a feasible option in the management of lumbar burst fractures, thereby addressing all the three columns through a single approach. Although cement leakage occurred but had no clinical consequences or neurological deficit. PMID:18193300

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

PubMed

Di Silvestre, Mario; Bakaloudis, Georgios; Lolli, Francesco; Vommaro, Francesco; Martikos, Konstantinos; Parisini, Patrizio

2008-10-01

The treatment of thoracic adolescent idiopathic scoliosis (AIS) of more than 80 degrees 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 degrees) 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 degrees (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 degrees vs. PSF-S: 88 degrees), 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

Application of dual-energy CT to suppression of metal artefact caused by pedicle screw fixation in radiotherapy: a feasibility study using original phantom

NASA Astrophysics Data System (ADS)

Wang, Tianyuan; Ishihara, Takeaki; Kono, Atsushi; Yoshida, Naoki; Akasaka, Hiroaki; Mukumoto, Naritoshi; Yada, Ryuichi; Ejima, Yasuo; Yoshida, Kenji; Miyawaki, Daisuke; Kakutani, Kenichiro; Nishida, Kotaro; Negi, Noriyuki; Minami, Toshiaki; Aoyama, Yuuichi; Takahashi, Satoru; Sasaki, Ryohei

2017-08-01

The objective of the present study was the determination of the potential dosimetric benefits of using metal-artefact-suppressed dual-energy computed tomography (DECT) images for cases involving pedicle screw implants in spinal sites. A heterogeneous spinal phantom was designed for the investigation of the dosimetric effect of the pedicle-screw-related artefacts. The dosimetric comparisons were first performed using a conventional two-directional opposed (AP-PA) plan, and then a volumetric modulated arc therapy (VMAT) plan, which are both used for the treatment of spinal metastases in our institution. The results of Acuros® XB dose-to-medium (Dm) and dose-to-water (Dw) calculations using different imaging options were compared with experimental measurements including the chamber and film dosimetries in the spinal phantom. A dual-energy composition image with a weight factor of  -0.2 and a dual-energy monochromatic image (DEMI) with an energy level of 180 keV were found to have superior abilities for artefact suppression. The Dm calculations revealed greater dosimetric effects of the pedicle screw-related artefacts compared to the Dw calculations. The results of conventional single-energy computed tomography showed that, although the pedicle screws were made from low-Z titanium alloy, the metal artefacts still have dosimetric effects, namely, an average (maximum) Dm error of 4.4% (5.6%) inside the spinal cord for a complex VMAT treatment plan. Our findings indicate that metal-artefact suppression using the proposed DECT (DEMI) approach is promising for improving the dosimetric accuracy near the implants and inside the spinal cord (average (maximum) Dm error of 1.1% (2.0%)).

[Analysis of reason and strategy for the failure of posterior pedicle screw short-segment internal fixation on thoracolumbar fractures].

PubMed

Xing, Jin-Ming; Peng, Wen-Ming; Shi, Chu-Yun; Xu, Lei; Pan, Qi-Huao

2013-03-01

To analyze the reason and strategy for failure of posterior pedicle screw short-segment internal fixation on thoracolumbar fractures. From March 2008 to December 2010,the clinical data of 18 patients with thoracolumbar fracture failed in posterior pedicle screw short-segment internal fixation were retrospectively analyzed. There were 11 males and 7 females with an average age of 37.2 years (ranged, 19 to 63). The time from the first operation to complication occurrence was from 6 to 44 months with an average of 14.3 months. Of them,fusion failure was in 7 cases (combined with screw breakage in 4 cases), the progressive neuro-dysfunction was in 5 cases,the progressive lumbodorsal pain was in 6 cases. All 18 patients with kyphosis were treated with anterior internal fixation remaining posterior fixation (9 cases) and anterior internal fixation after posterior fixation removal (9 cases). All the patients were followed up from 18 to 50 months with an average of 30.5 months. No intetnal fixation loosening and breakage were found, moreover, X-ray and lamellar CT showed bone healing well. Preoperative, postoperative at 3 months and at final follow-up, ODI score was respectively 31.6+/-5.1, 8.6+/-5.7, 8.3+/-3.2; VAS score was respectively 7.2+/-2.3, 2.3+/-0.7, 2.1+/-1.1; kyphosis angle was respectively (-21.2/-+7.8 degreeso, (-5.3+/-6.8 degrees ), (-5.8+/-7.8 )degrees. Compared with preoperative data ,above-listed items had obviously ameliorated(P<0.05). Treatment of thoracolumbar fracture with posterior pedicle screw short-segment internal fixation may result in the complications such as bone nonunion ,internal fixation breakage and progressive kyphosis. Anterior reconstruction may be a good strategy for the failure of posterior operation.

Biomechanical analysis of a novel hook-screw technique for C1-2 stabilization.

PubMed

Reis, Marco Túlio; Nottmeier, Eric W; Reyes, Phillip M; Baek, Seungwon; Crawford, Neil R

2012-09-01

The Food and Drug Administration has not cleared the following medical devices for the use described in this study. The following medical devices are being discussed for an off-label use: cervical lateral mass screws. As an alternative for cases in which the anatomy and spatial relationship between C-2 and a vertebral artery precludes insertion of C-2 pedicle/pars or C1-2 transarticular screws, a technique that includes opposing laminar hooks (claw) at C-2 combined with C-1 lateral mass screws may be used. The biomechanical stability of this alternate technique was compared with that of a standard screw-rod technique in vitro. Flexibility tests were performed in 7 specimens (occiput to C-3) in the following 6 different conditions: 1) intact; 2) after creating instability and attaching a posterior cable/graft at C1-2; 3) after removing the graft and attaching a construct comprising C-1 lateral mass screws and C-2 laminar claws; 4) after reattaching the posterior cable-graft at C1-2 (posterior hardware still in place); 5) after removing the posterior cable-graft and laminar hooks and placing C-2 pedicle screws interconnected to C-1 lateral mass screws via rod; and 6) after reattaching the posterior cable-graft at C1-2 (screw-rod construct still in place). All types of stabilization significantly reduced the range of motion, lax zone, and stiff zone compared with the intact condition. There was no significant biomechanical difference in terms of range of motion or lax zone between the screw-rod construct and the screw-claw-rod construct in any direction of loading. The screw-claw-rod technique restricts motion much like the standard Harms technique, making it an acceptable alternative technique when aberrant arterial anatomy precludes the placement of C-2 pars/pedicle screws or C1-2 transarticular screws.

Percutaneous pedicle screw fixation through the pedicle of fractured vertebra in the treatment of type A thoracolumbar fractures using Sextant system: an analysis of 38 cases.

PubMed

Wang, Hong-wei; Li, Chang-qing; Zhou, Yue; Zhang, Zheng-feng; Wang, Jian; Chu, Tong-wei

2010-06-01

To prospectively evaluate the feasibility, safety and efficacy of the percutaneous pedicle screw fixation through the pedicle of fractured vertebra in the treatment of type A thoracolumbar fractures using Sextant system in the retrospective non-randomized case-control study. A total of 38 consecutive non-randomized patients with type A thoracolumbar fractures, which had been stabilized posteriorly from December 2006 to March 2009, were examined retrospectively more than 9 months after surgery. Twenty-one patients had been treated conventionally with open pedicle screw fixation (OPSF) and 17 patients received minimally invasive treatment with Sextant percutaneous pedicle screw fixation (SPPSF). As a method of evaluation, the incision size, the intraoperation and postoperative volume of blood loss, operation time, postoperative hospital stay, blood transfusion, the radiological assessment of the sagittal Cobb;s angle, vertebral body angle and vertebral body height were recorded and compared. All patients were followed up for 8-24 months (average 11.6 months). There were significant differences in the incision size, surgical blood loss, surgical draining loss, operation time, hospital stay after operation, blood transfusion, the proportion of antalgic supplement and postoperative incisional VAS between the two groups (P less than 0.05). Mean preoperative kyphotic deformity was 16.0 degree and improved by 9.3 degree after surgery in OPSF group, but 15.2 degree and 10.3 degree respectively in SPPSF group. Mean preoperative angle of the fractured vertebral body was 15.9 degree and improved by 7.9 degree after surgery in OPSF group, but 14.9 degree and 6.6 degree respectively in SPPSF group. Mean anterior vertebral body height (% of normal) was 67.3% before surgery and 95.8% after surgery, but 69.1% and 90.1% respectively in SPPSF group. Mean posterior vertebral body height (% of normal) was 93.3% before surgery and 99.5% after surgery, but 88.9% and 93.3% respectively in

Outcome and safety analysis of 3D printed patient specific pedicle screw jigs for complex spinal deformities: A comparative study.

PubMed

Garg, Bhavuk; Gupta, Manish; Singh, Menaka; Kalyanasundaram, Dinesh

2018-05-03

Spinal deformities are very challenging to treat and have a great risk of neurological complications due to hardware placement during corrective surgery. Various techniques have been introduced to ensure safe and accurate placement of pedicle screws. Patient-specific screw guides with pre-drawn and pre-validated trajectory seems to be an attractive option. We have focused on developing 3D printing technique for complex spinal deformities in India. This study also aimed to compare the placement of pedicle screw with 3D printing and free hand technique. This is a retrospective comparative clinical study at an academic institutional setting. A total of 20 patients were enrolled during the study, 10 were operated with the help of 3D printing (group 1) and 10 were operated with freehand technique (group 2). Group 1 included 6 congenital, 3 adolescent idiopathic scoliosis (AIS), one post tubercular kyphosis and Group 2 included 5 congenital, 4 AIS and one post tubercular kyphosis patient. Primary outcomes were measured in terms of screw violation and secondary outcome were measured in terms of Surgical time, Blood loss, Radiation exposure (no. of shoots required) and complications. MIMICS v18.0 Software was used for 3D reconstruction from CT scan images of all the patients. 3-Matic software was used to create drill guide. 3-D printer from Stratasys Mojo ABS P 430 model material cartilage (a thermoplastic material) was used for printing of vertebrae model and jigs. Two sample test of proportion was used to compare correctly and wrongly pedicle screw placement with 3D printing and freehand technique. T-test with equal variance was used for operating surgical time and blood loss. This work was carried out by collaboration of Orthopaedics Department, All India Institute of Medical Sciences (AIIMS), New Delhi and Biomedical Engineering Department, Indian Institute of Technology (IIT) Delhi. This project received the grant of USD 60000 from Department of Biotechnology (DBT

Use of C2 spinous process screw for posterior cervical fixation as substitute for laminar screw in a patient with thin laminae

PubMed Central

Nagata, Kosei; Baba, Satoshi; Chikuda, Hirotaka; Takeshita, Katsushi

2013-01-01

Rigid screw fixation of C2 including transarticular screw and pedicle screw contain the risk of vertebral artery (VA) injury. On the other hand, translaminar screws are considered to be safer for patients with anomalous VA. But C2 translaminar screw placement was limited in patients who have thin laminas and there is marked variation in C2 laminar thickness. Appropriate C2 fixation method for a patient who has thin laminas and high-riding VA together was controversial. Here, we present a case of an elderly Asian woman who had thin laminas and high-riding VA together with progressive myelopathy to report a first case of C2 spinous process screw insertion. Although the stability and safety of C2 spinous process screw was reported in cadaver series, there was no clinical report to our knowledge. Spinous process screw can be an option of C2 fixation for patients with high-riding VA and severe degenerated cervical spines including thin C2 laminas. PMID:23814004

A study on a pedicle-screw-based reduction method for artificially reduced artifacts

NASA Astrophysics Data System (ADS)

Kim, Hyun-Ju; Lee, Hae-Kag; Cho, Jae-Hwan

2017-09-01

The purpose of this study is a quantitative analysis of the degree of the reduction of the artifacts that are induced by pedicle screws through the application of the recently developed iterative metallic artifact reduction (I MAR) software. Screw-type implants that are composed of 4.5 g/cm3 titanium (Ti) with an approximate average computed tomography (CT) value of 6500 Hounsfield units (HUs) that are used for the treatment of spinal diseases were placed in paraffin, a tissueequivalent material, and then dried. After the insertion, the scanning conditions were fixed as 120 kVp and 250 mA using multidetector computed tomography (MDCT) (Enlarge, Siemens, Germany). The slice thickness and the increment were set at the fields of view (FOVs) of 3 mm and 120 mm, respectively; the pitch is 0.8; the rotation time is 1 s; and the I MAR software was applied to the raw data of the acquired images to compare the CT-value changes of the posterior images. When the I MAR software was applied to animal vertebrae, it was possible to reduce the 65.7% image loss of the black-hole-effect image through the application of the I MAR software. When the I MAR image loss (%) was compared with the white-streak-effect image, the high-intensity image type with the white-streak effect could be reduced by 91.34% through the application of the I MAR software. In conclusion, a metal artifact that is due to a high-density material can be reduced more effectively when the I MAR algorithm is applied compared with that from the application of the conventional MAR algorithm. The I MAR can provide information on the various tissues that form around the artifact and the reduced metal structures, which can be helpful for radiologists and clinicians in their determination of an accurate diagnosis.

[Finite element analysis of stress changes of posterior spinal pedicle screw infixation].

PubMed

Yan, Jia-Zhi; Wu, Zhi-Hong; Xu, Ri-Xin; Wang, Xue-Song; Xing, Ze-Jun; Zhao, Yu; Zhang, Jian-Guo; Shen, Jian-Xiong; Wang, Yi-Peng; Qiu, Gui-Xing

2009-01-06

To evaluate the mechanical response of L3-L4 segment after posterior interfixation with a transpedicle screw system. Spiral CT machine was used to conduct continuous parallel scan on the L3-L4 section of a 40-year-old healthy male Chinese. The image data thus obtained were introduced into MIMICS software to reconstruct the 2-D data into volume data and obtain 3-D models of every element.. Pro/3-D model construction software system was used to simulate the 3-D entity of L3-L4 fixed by screw robs through spinal pedicle via posterior approach that was introduced into the finite element software ABAQUS to construct a 3-D finite element model. The stress changes on the vertebrae and screw under the axial pressure of 0.5 mPa was analyzed. Under the evenly distributed pressure the displacement of the L4 model was 0.00125815 mm, with an error of only 0.8167% from the datum displacement. The convergence of the model was good. The stress of the fixed vertebral body, intervertebral disc, and internal fixators changed significantly. The stress concentration zone of the intervertebral disc turned from the posterolateral side to anterolateral side. The stress produced by the fixed vertebral bodies decreased significantly. Obvious stress concentration existed in the upper and lower sides of the base of screw and the fixed screw at the upper vertebral body bore greater stress than the lower vertebral body. Integration of computer aided device and finite element analysis can successfully stimulate the internal fixation of L3-IA visa posterior approach and observe the mechanic changes in the vertebral column more directly.

Biomechanical comparison of four C1 to C2 rigid fixative techniques: anterior transarticular, posterior transarticular, C1 to C2 pedicle, and C1 to C2 intralaminar screws.

PubMed

Lapsiwala, Samir B; Anderson, Paul A; Oza, Ashish; Resnick, Daniel K

2006-03-01

We performed a biomechanical comparison of several C1 to C2 fixation techniques including crossed laminar (intralaminar) screw fixation, anterior C1 to C2 transarticular screw fixation, C1 to 2 pedicle screw fixation, and posterior C1 to C2 transarticular screw fixation. Eight cadaveric cervical spines were tested intact and after dens fracture. Four different C1 to C2 screw fixation techniques were tested. Posterior transarticular and pedicle screw constructs were tested twice, once with supplemental sublaminar cables and once without cables. The specimens were tested in three modes of loading: flexion-extension, lateral bending, and axial rotation. All tests were performed in load and torque control. Pure bending moments of 2 nm were applied in flexion-extension and lateral bending, whereas a 1 nm moment was applied in axial rotation. Linear displacements were recorded from extensometers rigidly affixed to the C1 and C2 vertebrae. Linear displacements were reduced to angular displacements using trigonometry. Adding cable fixation results in a stiffer construct for posterior transarticular screws. The addition of cables did not affect the stiffness of C1 to C2 pedicle screw constructs. There were no significant differences in stiffness between anterior and posterior transarticular screw techniques, unless cable fixation was added to the posterior construct. All three posterior screw constructs with supplemental cable fixation provide equal stiffness with regard to flexion-extension and axial rotation. C1 lateral mass-C2 intralaminar screw fixation restored resistance to lateral bending but not to the same degree as the other screw fixation techniques. All four screw fixation techniques limit motion at the C1 to 2 articulation. The addition of cable fixation improves resistance to flexion and extension for posterior transarticular screw fixation.

Achievable accuracy of hip screw holding power estimation by insertion torque measurement.

PubMed

Erani, Paolo; Baleani, Massimiliano

2018-02-01

To ensure stability of proximal femoral fractures, the hip screw must firmly engage into the femoral head. Some studies suggested that screw holding power into trabecular bone could be evaluated, intraoperatively, through measurement of screw insertion torque. However, those studies used synthetic bone, instead of trabecular bone, as host material or they did not evaluate accuracy of predictions. We determined prediction accuracy, also assessing the impact of screw design and host material. We measured, under highly-repeatable experimental conditions, disregarding clinical procedure complexities, insertion torque and pullout strength of four screw designs, both in 120 synthetic and 80 trabecular bone specimens of variable density. For both host materials, we calculated the root-mean-square error and the mean-absolute-percentage error of predictions based on the best fitting model of torque-pullout data, in both single-screw and merged dataset. Predictions based on screw-specific regression models were the most accurate. Host material impacts on prediction accuracy: the replacement of synthetic with trabecular bone decreased both root-mean-square errors, from 0.54 ÷ 0.76 kN to 0.21 ÷ 0.40 kN, and mean-absolute-percentage errors, from 14 ÷ 21% to 10 ÷ 12%. However, holding power predicted on low insertion torque remained inaccurate, with errors up to 40% for torques below 1 Nm. In poor-quality trabecular bone, tissue inhomogeneities likely affect pullout strength and insertion torque to different extents, limiting the predictive power of the latter. This bias decreases when the screw engages good-quality bone. Under this condition, predictions become more accurate although this result must be confirmed by close in-vitro simulation of the clinical procedure. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effectiveness of the surgical torque limiter: a model comparing drill- and hand-based screw insertion into locking plates.

PubMed

Ioannou, Christopher; Knight, Matthew; Daniele, Luca; Flueckiger, Lee; Tan, Ezekiel S L

2016-10-17

The objective of this study is to analyse the effectiveness of the surgical torque limiter during operative use. The study also investigates the potential differences in torque between hand and drill-based screw insertion into locking plates using a standardised torque limiter. Torque for both hand and power screw insertion was measured through a load cell, registering 6.66 points per second. This was performed in a controlled environment using synthetic bone, a locking plate and locking screws to simulate plate fixation. Screws were inserted by hand and by drill with torque values measured. The surgical torque limiter (1.5 Nm) was effective as the highest recorded reading in the study was 1.409 Nm. Comparatively, there is a statistically significant difference between screw insertion methods. Torque produced for manually driven screw insertion into locking plates was 1.289 Nm (95 % CI 1.269-1.308) with drill-powered screw insertion at 0.740 Nm (95 % CI 0.723-0.757). The surgical torque limiter proved to be effective as per product specifications. Screws inserted under power produce significantly less torque when compared to manual insertion by hand. This is likely related to the mechanism of the torque limiter when being used at higher speeds for which it was designed. We conclude that screws may be inserted using power to the plate with the addition of a torque limiter. It is recommended that all screws inserted by drill be hand tightened to achieve adequate torque values.

[Biomechanical study on effects of bone mineral density on fixation strength of expansive pedicle screw].

PubMed

Gao, Mingxuan; Li, Xusheng; Zhen, Ping; Wu, Zhigang; Zhou, Shenghu; Tian, Qi; Lei, Wei

2013-08-01

To evaluate the fixation strength of expansive pedicle screw (EPS) at different bone mineral density (BMD) levels, further to provide theoretical evidence for the clinical application of the EPS in patients with osteoporosis. Fresh human cadaver spines (T12-L5 spines) were divided into 4 levels: normal BMD, osteopenia, osteoporosis, and severe osteoporosis according to the value of BMD, 12 vertebra in each level. Conventional pedicle screw (CPS) or EPS was implanted into the bilateral vertebra in CPS group and EPS group, respectively, 12 screws in each group per BMD level. Screw pullout tests were conducted. The maximum pullout strength, stiffness, and energy absorption were determined by an AG-IS material testing machine with constant rate of loading in a speed of 5 mm/min. With the decline of BMD from normal to severe osteoporosis level, the maximum pullout strength and the stiffness correspondingly declined (P < 0.05). In CPS group, the energy absorption gradually decreased (P < 0.05); in EPS group, significant difference was found between other different BMD levels (P < 0.05) except between normal BMD and osteopenia and between osteoporosis and severe osteoporosis (P > 0.05). At the same BMD level, the maximum pullout strength of EPS group was significantly larger than that of CPS group (P < 0.05); the stiffness of EPS group was significantly higher than that of CPS group (P < 0.05) except one at normal BMD level; and no significant difference was found in the energy absorption between 2 groups (P > 0.05) except one at osteopenia level. No significant difference was found in maximum pullout strength, stiffness, and energy absorption between EPS group at osteoporosis level and CPS group at osteopenia level (P > 0.05); however, the maximum pullout strength, stiffness, and energy absorption of EPS group at severe osteoporosis level were significantly lower than those of CPS group at osteopenia level (P < 0.05). Compared with CPS, the EPS can significantly improve

Morphology study of thoracic transverse processes and its significance in pedicle-rib unit screw fixation.

PubMed

Cui, Xin-gang; Cai, Jin-fang; Sun, Jian-min; Jiang, Zhen-song

2015-03-01

Thoracic transverse process is an important anatomic structure of the spine. Several anatomic studies have investigated the adjacent structures of the thoracic transverse process. But there is still a blank on the morphology of the thoracic transverse processes. The purpose of the cadaveric study is to investigate the morphology of thoracic transverse processes and to provide morphology basis for the pedicle-rib unit (extrapedicular) screw fixation method. Forty-five adult dehydrated skeletons (T1-T10) were included in this study. The length, width, thickness, and the tilt angle (upward and backward) of the thoracic transverse process were measured. The data were then analyzed statistically. On the basis of the morphometric study, 5 fresh cadavers were used to place screws from transverse processes to the vertebral body in the thoracic spine, and then observed by the naked eye and on computed tomography scans. The lengths of thoracic transverse processes were between 16.63±1.59 and 18.10±1.95 mm; the longest was at T7, and the shortest was at T10. The widths of thoracic transverse processes were between 11.68±0.80 and 12.87±1.48 mm; the widest was at T3, and the narrowest was at T7. The thicknesses of thoracic transverse processes were between 7.86±1.24 and 10.78±1.35 mm; the thickest was at T1, and the thinnest was at T7. The upward tilt angles of thoracic transverse processes were between 24.9±3.1 and 3.0±1.56 degrees; the maximal upward tilt angle was at T1, and the minimal upward tilt angle was at T7. The upward tilt angles of T1 and T2 were obviously different from the other thoracic transverse processes (P<0.01). The backward tilt angles of thoracic transverse processes gradually increased from 24.5±2.91 degrees at T1 to 64.5±5.12 degrees at T10. The backward tilt angles were significantly different between each other, except between T5 and T6. In the validation study, screws were all placed successfully from transverse processes to the vertebrae of

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

PubMed

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

2015-11-25

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 AND 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.

How Does Patient Radiation Exposure Compare With Low-dose O-arm Versus Fluoroscopy for Pedicle Screw Placement in Idiopathic Scoliosis?

PubMed

Su, Alvin W; McIntosh, Amy L; Schueler, Beth A; Milbrandt, Todd A; Winkler, Jennifer A; Stans, Anthony A; Larson, A Noelle

Intraoperative C-arm fluoroscopy and low-dose O-arm are both reasonable means to assist in screw placement for idiopathic scoliosis surgery. Both using pediatric low-dose O-arm settings and minimizing the number of radiographs during C-arm fluoroscopy guidance decrease patient radiation exposure and its deleterious biological effect that may be associated with cancer risk. We hypothesized that the radiation dose for C-arm-guided fluoroscopy is no less than low-dose O-arm scanning for placement of pedicle screws. A multicenter matched-control cohort study of 28 patients in total was conducted. Fourteen patients who underwent O-arm-guided pedicle screw insertion for spinal fusion surgery in 1 institution were matched to another 14 patients who underwent C-arm fluoroscopy guidance in the other institution in terms of the age of surgery, body weight, and number of imaged spine levels. The total effective dose was compared. A low-dose pediatric protocol was used for all O-arm scans with an effective dose of 0.65 mSv per scan. The effective dose of C-arm fluoroscopy was determined using anthropomorphic phantoms that represented the thoracic and lumbar spine in anteroposterior and lateral views, respectively. The clinical outcome and complications of all patients were documented. The mean total effective dose for the O-arm group was approximately 4 times higher than that of the C-arm group (P<0.0001). The effective dose for the C-arm patients had high variability based on fluoroscopy time and did not correlate with the number of imaged spine levels or body weight. The effective dose of 1 low-dose pediatric O-arm scan approximated 85 seconds of the C-arm fluoroscopy time. All patients had satisfactory clinical outcomes without major complications that required returning to the operating room. Radiation exposure required for O-arm scans can be higher than that required for C-arm fluoroscopy, but it depends on fluoroscopy time. Inclusion of more medical centers and surgeons

Cortical bone trajectory screw fixation versus traditional pedicle screw fixation for 2-level posterior lumbar interbody fusion: comparison of surgical outcomes for 2-level degenerative lumbar spondylolisthesis.

PubMed

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

2018-01-01

OBJECTIVE The cortical bone trajectory (CBT) screw technique is a new nontraditional pedicle screw (PS) insertion method. However, the biomechanical behavior of multilevel CBT screw/rod fixation remains unclear, and surgical outcomes in patients after 2-level posterior lumbar interbody fusion (PLIF) using CBT screw fixation have not been reported. Thus, the purposes of this study were to examine the clinical and radiological outcomes after 2-level PLIF using CBT screw fixation for 2-level degenerative lumbar spondylolisthesis (DS) and to compare these outcomes with those after 2-level PLIF using traditional PS fixation. METHODS The study included 22 consecutively treated patients who underwent 2-level PLIF with CBT screw fixation for 2-level DS (CBT group, mean follow-up 39 months) and a historical control group of 20 consecutively treated patients who underwent 2-level PLIF using traditional PS fixation for 2-level DS (PS group, mean follow-up 35 months). Clinical symptoms were evaluated using the Japanese Orthopaedic Association (JOA) scoring system. Bony union was assessed by dynamic plain radiographs and CT images. Surgery-related complications, including symptomatic adjacent-segment disease (ASD), were examined. RESULTS The mean operative duration and intraoperative blood loss were 192 minutes and 495 ml in the CBT group and 218 minutes and 612 ml in the PS group, respectively (p < 0.05 and p > 0.05, respectively). The mean JOA score improved significantly from 12.3 points before surgery to 21.1 points (mean recovery rate 54.4%) at the latest follow-up in the CBT group and from 12.8 points before surgery to 20.4 points (mean recovery rate 51.8%) at the latest follow-up in the PS group (p > 0.05). Solid bony union was achieved at 90.9% of segments in the CBT group and 95.0% of segments in the PS group (p > 0.05). Symptomatic ASD developed in 2 patients in the CBT group (9.1%) and 4 patients in the PS group (20.0%, p > 0.05). CONCLUSIONS Two-level PLIF with CBT

Correlation of pull-out strength of cement-augmented pedicle screws with CT-volumetric measurement of cement.

PubMed

Fölsch, Christian; Goost, Hans; Figiel, Jens; Paletta, Jürgen R J; Schultz, Wolfgang; Lakemeier, Stefan

2012-12-01

Cement augmentation of pedicle screws increases fixation strength in an osteoporotic spine. This study was designed to determine the cement distribution and the correlation between the pull-out strength of the augmented screw and the cement volume within polyurethane (PU) foam. Twenty-eight cannulated pedicle screws (6×45 mm) (Peter Brehm, Erlangen, Germany) with four holes at the distal end of the screw were augmented with the acrylic Stabilit ER Bone Cement Vertebral Augmentation System (DFine Inc., San Jose, CA, USA) and implanted into open-cell rigid PU foam (Pacific Research Laboratories, Vashon Island, WA, USA) with a density of 0.12 g/cm3, resembling severe osteoporosis. Volumetric measurement of the cement with consideration of the distribution around the screws was done with multislice computed tomography scan (Somatom Definition, Siemens, Erlangen, Germany). Pull-out strength was tested with a servohydraulic system (MTS System Corporation, Eden Prairie, MN, USA), and nonaugmented screws served as control. Pearson's correlation coefficient with significance level α=0.05 and one-way analysis of variance test were used. We found a high (r=0.88) and significant (p<0.01) correlation between the cement volume and the pull-out strength, which increased by more than 5-fold with a volume of 3 ml. The correlation appeared linear at least up to 4 ml cement volume and failure always occurred at the cement-bone interface. The cement distribution was symmetric and circular around the most proximal hole, with a distance of 14 mm from the tip, and nearly 90% of the cement was found 6 mm distal and cranial to it. The 95% confidence interval for the relative amount of cement was 37%-41% within 2 mm of the most proximal hole. Compared with the control, a cement volume between 2.0 and 3.0 ml increased the pull-out strength significantly and is relevant for clinical purposes, whereas a volume of 0.5 ml did not. A cement volume beyond 3.0 ml should further increase the pull

Segmental vs non-segmental thoracic pedicle screws constructs in adolescent idiopathic scoliosis: is there any implant alloy effect?

PubMed

Di Silvestre, Mario; Bakaloudis, Georgeous; Ruosi, Carlo; Pipola, Valerio; Colella, Gianluca; Greggi, Tiziana; Ruffilli, Alberto; Vommaro, Francesco

2017-10-01

The aim of this study is to understand how many anchor sites are necessary to obtain maximum posterior correction of idiopathic scoliotic curve and if the alloy of instrumentation, stainless steel or titanium, may have a role in the percent of scoliosis correction. We reviewed 143 consecutive patients, affected by AIS (Lenke 1-2), who underwent a posterior spinal fusion with pedicle screw-only instrumentation between 2002 and 2005. According to the implant density and alloy used we divided the cohort in four groups. All 143 patients were reviewed at an average follow-up of 7, 2 years, the overall final main thoracic curve correction averaged 61.4%, whereas the implant density within the major curve averaged 71%. A significant correlation was observed between final% MT correction and preoperative MT flexibility and implant density. When stainless steel instrumentation is used non-segmental pedicle screw constructs seem to be equally effective as segmental instrumentations in obtaining satisfactory results in patients with main thoracic AIS. When the implant alloy used is titanium one, an implant density of ≥60% should be guaranteed to achieve similar results.

Economic evaluation comparing intraoperative cone beam CT-based navigation and conventional fluoroscopy for the placement of spinal pedicle screws: a patient-level data cost-effectiveness analysis.

PubMed

Dea, Nicolas; Fisher, Charles G; Batke, Juliet; Strelzow, Jason; Mendelsohn, Daniel; Paquette, Scott J; Kwon, Brian K; Boyd, Michael D; Dvorak, Marcel F S; Street, John T

2016-01-01

. Annual maintenance costs were also added. Finally, reoperation costs using a micro-costing approach were calculated for both groups. An incremental cost-effectiveness ratio was calculated and reported as cost per reoperation avoided. Based on reoperation costs in Canada and in the United States, a minimal caseload was calculated for the more expensive alternative to be cost saving. Sensitivity analyses were also conducted. A total of 5,132 pedicle screws were inserted in 502 patients during the study period: 2,682 screws in 253 patients in the treatment group and 2,450 screws in 249 patients in the control group. Overall accuracy rates were 95.2% for the treatment group and 86.9% for the control group. Within 1 year post treatment, two patients (0.8%) required a revision surgery in the treatment group compared with 15 patients (6%) in the control group. An incremental cost-effectiveness ratio of $15,961 per reoperation avoided was calculated for the CAS group. Based on a reoperation cost of $12,618, this new technology becomes cost saving for centers performing more than 254 instrumented spinal procedures per year. Computer-assisted spinal surgery has the potential to reduce reoperation rates and thus to have serious cost-effectiveness and policy implications. High acquisition and maintenance costs of this technology can be offset by equally high reoperation costs. Our cost-effectiveness analysis showed that for high-volume centers with a similar case complexity to the studied population, this technology is economically justified. Copyright © 2015 Elsevier Inc. All rights reserved.

Convex Hemiepiphysiodesis: Posterior/anterior in-situ Versus Posterior-only With Pedicle Screw Instrumentation: An Experimental Simulation in Immature Pigs.

PubMed

Bekmez, Senol; Demirkiran, Halil G; Yilmaz, Guney; Akel, Ibrahim; Atilla, Pergin; Muftuoglu, Sevda Fatma; Yazici, Muharrem; Alanay, Ahmet

2016-12-01

Experimental study. Convex growth arrest (CGA) has been commonly used in the treatment of long-sweeping congenital deformities of the immature spine. As there are major drawbacks about the anterior procedure in the conventional CGA method, a new modification has been documented that using only posterior spinal approach with pedicle screw instrumentation. The aim of the study was to compare posterior-only CGA using pedicle screws with combined anterior/posterior in-situ CGA for the findings in histologic, radiologic, and manual palpation examinations in an immature pig model. Twelve 10-weeks old pigs were grouped into 2. In group 1, posterior-only, pedicle screw instrumented CGA was performed on the left side of L1-L4 vertebrae. In group 2, conventional combined posterior and anterior CGA was performed to the left side of L1-L4 vertebrae without instrumentation. All animals were killed twelve weeks after surgery. T11-L5 segments were en-bloc resected and radiologic, histologic, and manual palpation examinations were done. Marked scoliotic (12.2±2.5 and 9.2±1.3 in group 1 and 2, respectively) and kyphotic (11.2±1.0 degrees for the group 1 and 12±5.2 degrees for the group 2, respectively) deformities were noted in both groups, which were caused by hemiepiphysiodesis effect. Anterior and posterior parts of group 2 and posterior part of group 1 demonstrated fusion in histologic and radiologic analyzes. In anterior part of the group 1, marked narrowing on the disk spaces and thinning of growth plates were noted in radiologicg examination, chondrocyte degeneration, and newly-formed bone trabeculae in disk-space were noted in histological examination. In manual palpation, no motion was detected in group 1 and motion was detected in only one segment of one animal in group 2. Anterior growth of the vertebrae can be controlled by application of posterior transpedicular screws and rod. Such an effect can eliminate the need for anterior surgical intervention in convex

A prospective, randomized, controlled trial of robot-assisted vs freehand pedicle screw fixation in spine surgery.

PubMed

Kim, Ho-Joong; Jung, Whan-Ik; Chang, Bong-Soon; Lee, Choon-Ki; Kang, Kyoung-Tak; Yeom, Jin S

2017-09-01

The purpose of this study was to compare the accuracy and safety of an instrumented posterior lumbar interbody fusion (PLIF) using a robot-assisted minimally invasive (Robot-PLIF) or a conventional open approach (Freehand-PLIF). Patients undergoing an instrumented PLIF were randomly assigned to be treated using a Robot-PLIF (37 patients) and a Freehand-PLIF (41 patients). For intrapedicular accuracy, there was no significant difference between the groups (P = 0.534). For proximal facet joint accuracy, none of the 74 screws in the Robot-PLIF group violated the proximal facet joint, while 13 of 82 in the Freehand-PLIF group violated the proximal facet joint (P < 0.001). The average distance of the screws from the facets was 5.2 ± 2.1 mm and 2.7 ± 1.6 mm in the Robot-PLIF and Freehand-PLIF groups, respectively (P < 0.001). Robotic-assisted pedicle screw placement was associated with fewer proximal facet joint violations and better convergence orientations. Copyright © 2016 John Wiley & Sons, Ltd.

Exploring the role of 3-dimensional simulation in surgical training: feedback from a pilot study.

PubMed

Podolsky, Dale J; Martin, Allan R; Whyne, Cari M; Massicotte, Eric M; Hardisty, Michael R; Ginsberg, Howard J

2010-12-01

Randomized control study assessing the efficacy of a pedicle screw insertion simulator. To evaluate the efficacy of an in-house developed 3-dimensional software simulation tool for teaching pedicle screw insertion, to gather feedback about the utility of the simulator, and to help identify the context and role such simulation has in surgical education. Traditional instruction for pedicle screw insertion technique consists of didactic teaching and limited hands-on training on artificial or cadaveric models before guided supervision within the operating room. Three-dimensional computer simulation can provide a valuable tool for practicing challenging surgical procedures; however, its potential lies in its effective integration into student learning. Surgical residents were recruited from 2 sequential years of a spine surgery course. Patient and control groups both received standard training on pedicle screw insertion. The patient group received an additional 1-hour session of training on the simulator using a CT-based 3-dimensional model of their assigned cadaver's spine. Qualitative feedback about the simulator was gathered from the trainees, fellows, and staff surgeons, and all pedicles screws physically inserted into the cadavers during the courses were evaluated through CT. A total of 185 thoracic and lumbar pedicle screws were inserted by 37 trainees. Eighty-two percent of the 28 trainees who responded to the questionnaire and all fellows and staff surgeons felt the simulator to be a beneficial educational tool. However, the 1-hour training session did not yield improved performance in screw placement. A 3-dimensional computer-based simulation for pedicle screw insertion was integrated into a cadaveric spine surgery instructional course. Overall, the tool was positively regarded by the trainees, fellows, and staff surgeons. However, the limited training with the simulator did not translate into widespread comfort with its operation or into improvement in

Safe Zone of Posterior Screw Insertion for Talar Neck Fractures on 3-Dimensional Reconstruction Model.

PubMed

Wu, Jian-Qun; Ma, Sheng-Hui; Liu, Song; Qin, Cheng-He; Jin, Dan; Yu, Bin

2017-02-01

To investigate the optimal posterior screw placement and the geometry of safe zones for screw insertion in the talar neck. Computed tomography data for 15 normal feet were imported into Mimics 10.01 software for 3-dimensional reconstruction; 4.0-mm-diameter screws were simulated from the lateral tubercle of the posterior process of the talus to the talar head. The range of screw paths trajectories and screw lengths at nine locations that did not breach the cortex of the talus were evaluated. In addition, the farthest (point a) and nearest point (point b) of the safe zone to the subtalar joint at each location, the anteversion angle (angle A), which is parallel to the sagittal plane, and the horizontal angle (angle B), which is perpendicular to the sagittal plane, were measured. The safe zone was mainly between the 30% location and the 60% location; the width of each safe zone was 13.6° ± 1.4°; the maximum height of each safe zone was 7.8° ± 1.2°. The height of the safe zone was lowest at the 30% location (4.5°) and highest at the 50% location (7.3°). The mixed safe zone of all tali was between the 50% location and the 60% location. When a screw was inserted at point a, the safe entry distance (screw length) ranged from 48.8 to 49.5 mm, and when inserted to point b, the distance ranged from 48.2 to 48.9 mm. And inserting a 48.7 mm screw, 5.6° laterally and 7.4° superiorly, from the lateral tubercle of the posterior process of the talus towards the talar head is safest. The safe zone of posterior screw fixation have been defined applying to most talus, assuming the fractures are well reduced, this may strengthen the stability, shorten the operation time and reduce the incidence of surgical complications. © 2017 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

Precision insertion of percutaneous sacroiliac screws using a novel augmented reality-based navigation system: a pilot study.

PubMed

Wang, Huixiang; Wang, Fang; Leong, Anthony Peng Yew; Xu, Lu; Chen, Xiaojun; Wang, Qiugen

2016-09-01

Augmented reality (AR) enables superimposition of virtual images onto the real world. The aim of this study is to present a novel AR-based navigation system for sacroiliac screw insertion and to evaluate its feasibility and accuracy in cadaveric experiments. Six cadavers with intact pelvises were employed in our study. They were CT scanned and the pelvis and vessels were segmented into 3D models. The ideal trajectory of the sacroiliac screw was planned and represented visually as a cylinder. For the intervention, the head mounted display created a real-time AR environment by superimposing the virtual 3D models onto the surgeon's field of view. The screws were drilled into the pelvis as guided by the trajectory represented by the cylinder. Following the intervention, a repeat CT scan was performed to evaluate the accuracy of the system, by assessing the screw positions and the deviations between the planned trajectories and inserted screws. Post-operative CT images showed that all 12 screws were correctly placed with no perforation. The mean deviation between the planned trajectories and the inserted screws was 2.7 ± 1.2 mm at the bony entry point, 3.7 ± 1.1 mm at the screw tip, and the mean angular deviation between the two trajectories was 2.9° ± 1.1°. The mean deviation at the nerve root tunnels region on the sagittal plane was 3.6 ± 1.0 mm. This study suggests an intuitive approach for guiding screw placement by way of AR-based navigation. This approach was feasible and accurate. It may serve as a valuable tool for assisting percutaneous sacroiliac screw insertion in live surgery.

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. Copyright © 2012 Elsevier Ltd. All rights reserved.

Metallic fragments on the surface of miniplates and screws before insertion.

PubMed

Ray, M S; Matthew, I R; Frame, J W

1999-02-01

Particulate metal fragments have been identified histologically within the tissues adjacent to miniplates and screws after they have been removed. These were thought to have been caused by corrosion and degradation of the metal. However, the particles may have originated from rough edges or from protuberances left on the metal surface after cutting and machining during manufacture, and subsequently become detached. This study was undertaken to analyse the incidence and distribution of metal fragments on the surface of miniplates and screws before use. Fifteen miniplates and 60 screws were examined by stereomicroscopy and scanning electron microscopy. Rough metal edges or protuberances were identified on over half the samples, mostly in the countersink area of screw holes on the mini-plates. Fragments were detected within some of the cruciform screw heads and on some screw threads. We conclude that metal protuberances are present on the surface of mini-plate components when they are received from the manufacturer. There is a risk that the fragments might be detached and deposited into the tissues during insertion.

Pedicle screw loosening is correlated to chronic subclinical deep implant infection: a retrospective database analysis.

PubMed

Leitner, Lukas; Malaj, Isabella; Sadoghi, Patrick; Amerstorfer, Florian; Glehr, Mathias; Vander, Klaus; Leithner, Andreas; Radl, Roman

2018-04-13

Spinal fusion is used for treatment of spinal deformities, degeneration, infection, malignancy, and trauma. Reduction of motion enables osseous fusion and permanent stabilization of segments, compromised by loosening of the pedicle screws (PS). Deep implant infection, biomechanical, and chemical mechanisms are suspected reasons for loosening of PS. Study objective was to investigate the frequency and impact of deep implant infection on PS loosening. Intraoperative infection screening from wound and explanted material sonication was performed during revision surgeries following dorsal stabilization. Case history events and factors, which might promote implant infections, were included in this retrospective survey. 110 cases of spinal metal explantation were included. In 29.1% of revision cases, infection screening identified a germ, most commonly Staphylococcus (53.1%) and Propionibacterium (40.6%) genus. Patients screened positive had a significant higher number of previous spinal operations and radiologic loosening of screws. Patients revised for adjacent segment failure had a significantly lower rate of positive infection screening than patients revised for directly implant associated reasons. Removal of implants that revealed positive screening effected significant pain relief. Chronic implant infection seems to play a role in PS loosening and ongoing pain, causing revision surgery after spinal fusion. Screw loosening and multiple prior spinal operations should be suspicious for implant infection after spinal fusion when it comes to revision surgery. These slides can be retrieved under Electronic Supplementary Material.

[Clinical application of atlas translaminar screws fixation in treatment of atlatoaxial instability].

PubMed

Wang, Guoyou; Fu, Shijie; Shen, Huarui; Guan, Taiyuan; Xu, Ping

2013-10-01

To explore the effectiveness of fixation of atlas translaminar screws in the treatment of atlatoaxial instability. A retrospective analysis was made on the clinical data of 32 patients with atlatoaxial instability treated with atlantoaxial trans-pedicle screws between March 2007 and August 2009. Of them, 7 patients underwent atlas translaminar screws combined with axis transpedicle screws fixation because of fracture types, anatomic variation, and intraoperative reason, including 5 males and 2 females with an average age of 48.2 years (range, 35-69 years). A total of 9 translaminar screws were inserted. Injury was caused by traffic accident in 4 cases, falling from height in 2 cases, and crushing in 1 case. Two cases had simple odontoid fracture (Anderson type II), and 5 cases had odontoid fracture combined with other injuries (massa lateralis atlantis fracture in 2, atlantoaxial dislocation in 1, and Hangman fracture in 2). The interval between injury and operation was 4-9 days (mean, 6 days). The preoperative Japanese Orthopaedic Association (JOA) score was 8.29 +/- 1.60. The X-ray films showed good position of the screws. Healing of incision by first intention was obtained, and no patient had injuries of the spinal cord injury, nerve root, and vertebral artery. Seven cases were followed up 9-26 months (mean, 14 months). Good bone fusion was observed at 8 months on average (range, 6-11 months). No loosening, displacement, and breakage of internal fixation, re-dislocation and instability of atlantoaxial joint, or penetrating of pedicle screw into the spinal canal and the spinal cord occurred. The JOA score was significantly improved to 15.29 +/- 1.38 at 6 months after operation (t = 32.078, P = 0.000). Atlas translaminar screws fixation has the advantages of firm fixation, simple operating techniques, and relative safety, so it may be a remedial measure of atlatoaxial instability.

A novel technique to prevent guide wire related complications while inserting the 4.0 mm cannulated screws.

PubMed

Qi, Bao-Chang; Ju, Wei-Na; Wang, Tie-Jun; Yu, Tie-Cheng; Zhao, Yi; Sun, Da-Hui

2015-01-01

Cannulated screws (4.0 mm) provide inter-fragmentary compression and stability to fractures. A guide wire is used to define the screw trajectory and hold the fracture fragment while the screw is being inserted. The cannulated shaft typically accommodates a 1.25 mm guide pin. Since the guide pin is very slender and undergoes elastic deformation during insertion, there is a high probability of pin breakage. The authors have devised a new way to place the 4.0 mm cannulated screws in a manner that prevents the intraoperative complication of guide wire breakage. For this technique, predrilling was achieved using a 2.0 mm K-wire which was subsequently replaced with a 1.25 mm guide pin under the protection of sleeve. 4.0 mm cannulated screws were then inserted into a defined trajectory over the guide pin. Using the technique, over 20 patients were managed in our department over a period of two years without any complications. We have observed that patients treated with this method experience short operation time, combined with good clinical outcome and we recommend its use in cases where cannulated screw use is warranted.

Paravertebral foramen screw fixation for posterior cervical spine fusion: biomechanical study and description of a novel technique.

PubMed

Maki, Satoshi; Aramomi, Masaaki; Matsuura, Yusuke; Furuya, Takeo; Ota, Mitsutoshi; Iijima, Yasushi; Saito, Junya; Suzuki, Takane; Mannoji, Chikato; Takahashi, Kazuhisa; Yamazaki, Masashi; Koda, Masao

2017-10-01

OBJECTIVE Fusion surgery with instrumentation is a widely accepted treatment for cervical spine pathologies. The authors propose a novel technique for subaxial cervical fusion surgery using paravertebral foramen screws (PVFS). The authors consider that PVFS have equal or greater biomechanical strength than lateral mass screws (LMS). The authors' goals of this study were to conduct a biomechanical study of PVFS, to investigate the suitability of PVFS as salvage fixation for failed LMS, and to describe this novel technique. METHODS The authors harvested 24 human cervical spine vertebrae (C3-6) from 6 fresh-frozen cadaver specimens from donors whose mean age was 84.3 ± 10.4 years at death. For each vertebra, one side was chosen randomly for PVFS and the other for LMS. For PVFS, a 3.2-mm drill with a stopper was advanced under lateral fluoroscopic imaging. The drill stopper was set to 12 mm, which was considered sufficiently short not to breach the transverse foramen. The drill was directed from 20° to 25° medially so that the screw could purchase the relatively hard cancellous bone around the entry zone of the pedicle. The hole was tapped and a 4.5-mm-diameter × 12-mm screw was inserted. For LMS, 3.5-mm-diameter × 14-mm screws were inserted into the lateral mass of C3-6. The pullout strength of each screw was measured. After pullout testing of LMS, a drill was inserted into the screw hole and the superior cortex of the lateral mass was pried to cause a fracture through the screw hole, simulating intraoperative fracture of the lateral mass. After the procedure, PVFS for salvage (sPVFS) were inserted on the same side and pullout strength was measured. RESULTS The CT scans obtained after screw insertion revealed no sign of pedicle breaching, violation of the transverse foramen, or fracture of the lateral mass. A total of 69 screws were tested (23 PVFS, 23 LMS, and 23 sPVFS). One vertebra was not used because of a fracture that occurred while the specimen was

Rates of Upper Facet Joint Violation in Minimally Invasive Percutaneous and Open Instrumentation: A Comparative Cohort Study of Different Insertion Techniques.

PubMed

Archavlis, Eleftherios; Amr, Nimer; Kantelhardt, Sven Rainer; Giese, Alf

2018-01-01

 Minimally invasive pedicle screw placement may have a higher incidence of violation of the superior cephalad unfused facet joint.  We investigated the incidence and risk factors of upper facet joint violation in percutaneous robot-assisted instrumentation versus percutaneous fluoroscopy-guided and open transpedicular instrumentation.  A retrospective study including all consecutive patients who underwent lumbar instrumentation, fusion, and decompression for spondylolisthetic stenosis and degenerative disk disease was conducted between January 2012 and January 2016. All operations were performed by the same surgeon; the patients were divided into three groups according to the method of instrumentation. Group 1 involved the robot-assisted instrumentation in 58 patients, group 2 consisted of 64 patients treated with a percutaneous transpedicular instrumentation using fluoroscopic guidance, and 72 patients in group 3 received an open midline approach for pedicle screw insertion.  Superior segment facet joint violation occurred in 2 patients in the robot-assisted group 1 (7%), in 22 of the percutaneous fluoroscopy-guided group 2 (34%), and in 6 cases of the open group (8%). The incidence of facet joint violation was present in 5% (3) of the screws in group 1, 22% (28) of the screws in group 2, and 3% (4) of the screws in group 3.  Meticulous surgical planning of the appropriate entry site (Weinstein's method), trajectory planning, and proper robot-assisted instrumentation of pedicle screws reduced the risk of superior segment facet joint violation. Georg Thieme Verlag KG Stuttgart · New York.

[Case-control study on accuracy and safety of patient-specific drill-guide templates used in scoliosis cases].

PubMed

Zhang, Yu-peng; Shi, Ya-min; Wang, Hua-dong; Hou, Shu-xun

2015-10-01

To evaluate the accuracy and safety of pedicle screw insertion with the aid of novel patient-specific drill-guide templates in scoliosis cases. Ten patients with scoliosis were selected to participate in the research (the observation group) from December 2013 to December 2014. The data was obtained from CT scanning, and put into the computer to perform reconstruction of spine, simulation of pedicle screw insertion, and design of patient-specific drill-guide templates with software. The templates were made with rapid prototyping technique. After sterilization, the templates were used to aid the pedicle screw insertion intraoperatively. The blood loss, operation duration, change of creatinine level pre- and post-operation, and complications related to pedicle screw insertion were recorded. The location of pedicle screws were graded so as to evaluate the accuracy. A comparative study was then performed with the data of ten scoliosis cases operated with free-hand method during the same period (control group). There were 5 cases of idiopathic scoliosis and 5 cases of congenital scoliosis in the observation group, including 3 males and 7 females. Their average age was 11.9 years old (ranged, 4 to 18 years old), and the average Cobb angle of main curve was 54.9° (ranged, 42.1° to 78.4°). There were also 5 cases of idiopathic scoliosis and 5 cases of congenital scoliosis in the control group,including 2 males and 8 females. Their average age was 12.6 years old (ranged, 6 to 17 years old), and the average Cobb angle of main curve was 56.6° (ranged, 38.2° to 93.4°). A total of 167 pedicle screws were inserted intraoperatively, with 138 screws (82.6%) in grade I, 26 screws (15.0%) in grade II, 4 screws in grade III (2.4%), but no screws in grade IV according to the CT image. There were 29 (17.4%) screws perforated, and 163 (97.6%) screws could be accepted. In the control group, a total of 165 pedicle screws were inserted intraoperatively, with 98 screws (59.4%) in grade

Analysis of plastic deformation in cortical bone after insertion of coated and non-coated self-tapping orthopaedic screws.

PubMed

Koistinen, A P; Korhonen, H; Kiviranta, I; Kröger, H; Lappalainen, R

2011-07-01

Insertion of internal fracture fixation devices, such as screws, mechanically weakens the bone. Diamond-like carbon has outstanding tribology properties which may decrease the amount of damage in tissue. The purpose of this study was to investigate methods for quantification of cortical bone damage after orthopaedic bone screw insertion and to evaluate the effect of surface modification on tissue damage. In total, 48 stainless steel screws were inserted into cadaver bones. Half of the screws were coated with a smooth amorphous diamond coating. Geometrical data of the bones was determined by peripheral quantitative computed tomography. Thin sections of the bone samples were prepared after screw insertion, and histomorphometric evaluation of damage was performed on images obtained using light microscopy. Micro-computed tomography and scanning electron microscopy were also used to examine tissue damage. A positive correlation was found between tissue damage and the geometric properties of the bone. The age of the cadaver significantly affected the bone mineral density, as well as the damage perimeter and diameter of the screw hole. However, the expected positive effect of surface modification was probably obscured by large variations in the results and, thus, statistically significant differences were not found in this study. This can be explained by natural variability in bone tissue, which also made automated image analysis difficult.

PLIF with a titanium cage and excised facet joint bone for degenerative spondylolisthesis--in augmentation with a pedicle screw.

PubMed

Okuyama, Koichiro; Kido, Tadato; Unoki, Eiki; Chiba, Mitsuho

2007-02-01

To determine the validity of posterior lumbar interbody fusion (PLIF) using a titanium cage filled with excised facet joint bone and a pedicle screw for degenerative spondylolisthesis. PLIF using a titanium cage filled with excised facet joint bone and a pedicle screw was performed in 28 consecutive patients (men 10, women 18). The mean age of the patients was 60 years (range, 52 to 75 y) at the time of surgery. The mean follow-up period was 2.3 years (range, 2.0 to 4.5 y). The operation was done at L3/4 in 5, L4/5 in 20, and L3/4/5 in 3 patients. The mean operative bleeding was 318+/-151 g (mean+/-standard deviation), and the mean operative time was 3.34+/-0.57 hours per fixed segment. Clinical outcome was assessed by Denis' Pain and Work scale. Radiologic assessment was done using Boxell's method. Fusion outcome was assessed using an established criteria. On Pain scale, 20 and 8 patients were rated P4 and P5 before surgery, and 11, 12, 2, 2, and 1 patients were rated P1, P2, P3, P4, and P5 at final follow-up, respectively. On Work scale (for only physical labors), 12 and 9 patients were rated W4 and W5, before surgery, and 12, 5, 1, and 3 patients were rated W1, W2, W3 and W5 at final follow-up, respectively. There was significant difference in clinical outcome (P<0.01, Wilcoxon singled-rank test) The mean %Slip and Slip Angle was 17.9+/-8.1% and 3.9+/-5.8 degrees before surgery. The mean % Slip and Slip Angle was 5.4+/-4.4% and -2.0+/-4.8 degrees at final follow-up. There was a significant difference between the values (P<0.01, paired t test). "Union" and "probable union" was determined in 29 (93.5%) and 2 (6.5%) of 31 operated segments at 2.3 years (range, 2.0 to 4.5 y), postoperatively. PLIF using a titanium cage filled with excised facet joint bone and a pedicle screw provided a satisfactory clinical outcome and an excellent union rate without harvesting and grafting the autologous iliac bone.

Biomechanical analysis comparing three C1-C2 transarticular screw salvaging fixation techniques.

PubMed

Elgafy, Hossein; Potluri, Tejaswy; Goel, Vijay K; Foster, Scott; Faizan, Ahmad; Kulkarni, Nikhil

2010-02-15

This is an in vitro biomechanical study. To compare the biomechanical stability of the 3 C1-C2 transarticular screw salvaging fixation techniques. Stabilization of the atlantoaxial complex is a challenging procedure because of its complicated anatomy. Many posterior stabilization techniques of the atlantoaxial complex have been developed with C1-C2 transarticular screw fixation been the current gold standard. The drawback of using the transarticular screws is that it has a potential risk of vertebral artery injury due to a high riding transverse foramen of C2 vertebra, and screw malposition. In such cases, it is not recommended to proceed with inserting the contralateral transarticular screw and the surgeon should find an alternative to fix the contralateral side. Many studies are available comparing different atlantoaxial stabilization techniques, but none of them compared the techniques to fix the contralateral side while using the transarticular screw on one side. The current options are C1 lateral mass screw and short C2 pedicle screw or C1 lateral mass screw and C2 intralaminar screw, or C1-C2 sublaminar wire. Nine fresh human cervical spines with intact ligaments (C0-C4) were subjected to pure moments in the 6 loading directions. The resulting spatial orientations of the vertebrae were recorded using an Optotrak 3-dimensional Motion Measurement System. Measurements were made sequentially for the intact spine after creating type II odontoid fracture and after stabilization with unilateral transarticular screw placement across C1-C2 (TS) supplemented with 1 of the 3 transarticular salvaging techniques on the contralateral side; C1 lateral mass screw and C2 pedicle screw (TS+C1LMS+C2PS), C1 lateral mass and C2 intralaminar screw (TS+C1LMS+C2ILS), or sublaminar wire (TS + wire). The data indicated that all the 3 stabilization techniques significantly decreased motion when compared to intact in all the loading cases (left/right lateral bending, left/right axial

Immediate percutaneous sacroiliac screw insertion for unstable pelvic fractures: is it safe enough?

PubMed

Acker, A; Perry, Z H; Blum, S; Shaked, G; Korngreen, A

2018-04-01

The purpose of this study was to compare the results of immediate and delayed percutaneous sacroiliac screws surgery for unstable pelvic fractures, regarding technical results and complication rate. Retrospective study. The study was conducted at the Soroka University Medical center, Beer Sheva, Israel, which is a level 1 trauma Center. 108 patients with unstable pelvic injuries were operated by the orthopedic department at the Soroka University Medical Center between the years 1999-2010. A retrospective analysis found 50 patients with immediate surgery and 58 patients with delayed surgery. Preoperative and postoperative imaging were analyzed and data was collected regarding complications. All patients were operated on by using the same technique-percutaneous fixation of sacroiliac joint with cannulated screws. The study's primary outcome measure was the safety and quality of the early operation in comparison with the late operation. A total of 156 sacroiliac screws were inserted. No differences were found between the immediate and delayed treatment groups regarding technical outcome measures (P value = 0.44) and complication rate (P value = 0.42). The current study demonstrated that immediate percutaneous sacroiliac screw insertion for unstable pelvic fractures produced equally good technical results, in comparison with the conventional delayed operation, without additional complications.

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

PubMed

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

2016-10-01

Retrospective study. 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. There has been only one prior in vivo study on CBT insertional torque. 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. 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). 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.

Post-operative bracing after pedicle screw fixation for thoracolumbar burst fractures: A cost-effectiveness study.

PubMed

Piazza, Matthew; Sinha, Saurabh; Agarwal, Prateek; Mallela, Arka; Nayak, Nikhil; Schuster, James; Stein, Sherman

2017-11-01

While frequently prescribed to patients following fixation for spine trauma, the utility of spinal orthoses during the post-operative period is poorly described in the literature. In this study, we calculated rates of reoperation and performed a decision analysis to determine the utility of bracing following pedicle screw fixation for thoracic and lumbar burst fractures. Pubmed was searched for articles published between 2005 and 2015 for terms related to pedicle screw fixation of thoracolumbar fractures. Additionally, a database of neurosurgical patients operated on within the authors institution was also used in the analysis. Incidences of significant adverse events (wound revision for either dehiscence or infection or re-operation for non-union or instability due to hardware failure) were determined. Pooled means and variances of reported parameters were obtained using a random-effects, inverse variance meta-analytic model for observational data. Utilities for surgical outcome and complications were assigned using previously published values. Of the 225 abstracts reviewed, 48 articles were included in the study, yielding a total of 1957 patients. After including patients from the institutional registry, together a total of 2081 patients were included in the final analysis, 1328 of whom were braced. Non-braced patients were older then braced patients, although this only approached significance (p=0.051). Braced patients had significantly lower rates of re-operation for non-union or clinically significant hardware failure (1.3% vs. 1.8%, p<0.001) although the groups had comparable rates of operative wound dehiscence and infection (p=1.000). These two approaches yielded comparable utility scores (p=0.120). Costs between braced and non-braced patients were comparable excluding the cost of the brace (p=0.256); hence, the added cost of the brace suggests that bracing post-operatively is not a cost effective measure. Bracing following operative stabilization of

An in vitro biomechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: an axial positioned dynamic compression plate and two abaxial transarticular cortical screws inserted in lag fashion versus three parallel transarticular cortical screws inserted in lag fashion.

PubMed

Sod, Gary A; Riggs, Laura M; Mitchell, Colin F; Hubert, Jeremy D; Martin, George S

2010-01-01

To compare in vitro monotonic biomechanical properties of an axial 3-hole, 4.5 mm narrow dynamic compression plate (DCP) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion (DCP-TLS) with 3 parallel transarticular 5.5 mm cortical screws inserted in lag fashion (3-TLS) for the equine proximal interphalangeal (PIP) joint arthrodesis. Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. Cadaveric adult equine forelimbs (n=15 pairs). For each forelimb pair, 1 PIP joint was stabilized with an axial 3-hole narrow DCP (4.5 mm) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion and 1 with 3 parallel transarticular 5.5 mm cortical screws inserted in lag fashion. Five matching pairs of constructs were tested in single cycle to failure under axial compression, 5 construct pairs were tested for cyclic fatigue under axial compression, and 5 construct pairs were tested in single cycle to failure under torsional loading. Mean values for each fixation method were compared using a paired t-test within each group with statistical significance set at P<.05. Mean yield load, yield stiffness, and failure load under axial compression and torsion, single cycle to failure, of the DCP-TLS fixation were significantly greater than those of the 3-TLS fixation. Mean cycles to failure in axial compression of the DCP-TLS fixation was significantly greater than that of the 3-TLS fixation. The DCP-TLS was superior to the 3-TLS in resisting the static overload forces and in resisting cyclic fatigue. The results of this in vitro study may provide information to aid in the selection of a treatment modality for arthrodesis of the equine PIP joint.

Less invasive reduction and fusion of fresh A2 and A 3 traumatic L 1-L 4 fractures with a novel vertebral body augmentation implant and short pedicle screw fixation and fusion.

PubMed

Korovessis, Panagiotis; Vardakastanis, Konstantinos; Repantis, Thomas; Vitsas, Vasilios

2014-04-01

The aim of this clinical study was to report on the efficacy in reduction and safety in PMMA leakage of a novel vertebral augmentation technique with PEEK and PMMA, together with pedicle screws in the treatment of fresh vertebral fractures in young adults. Twenty consecutive young adults aged 45 ± 11 years with fresh burst A3/AO or severely compressed A2/AO fractures underwent via a less invasive posterior approach one-staged reduction with a novel augmentation implant and PMMA plus 3-vertebrae pedicle screw fixation and fusion. Radiologic parameters as segmental kyphosis (SKA), anterior (AVBHr) and posterior vertebral body height ratio (PVBHr), spinal canal encroachment (SCE), cement leakage and functional parameters as VAS, SF-36 were measured pre- and post-operatively. Hybrid construct restored AVBHr (P < 0.000), PVBHr (P = 0.02), SKA (P = 0.015), SCE (P = 0.002) without loss of correction at an average follow-up of 17 months. PMMA leakage occurred in 3 patients (3 vertebrae) either anteriorly to the fractured vertebral body or to the adjacent disc, but in no case to the spinal canal. Two pedicle screws were malpositioned (one medially, one laterally to the pedicle at the fracture level) without neurologic sequelae. Solid posterolateral spinal fusion occurred 8-10 months post-operatively. Pre-operative VAS and SF-36 scores improved post-operatively significantly. This study showed that this novel vertebral augmentation technique using PEEK implant and PMMA reduces and stabilizes via less invasive technique A2 and A3 vertebral fractures without loss of correction and leakage to the spinal canal.

Prospective comparison of virtual fluoroscopy to fluoroscopy and plain radiographs for placement of lumbar pedicle screws.

PubMed

Resnick, Daniel K

2003-06-01

Fluoroscopy-based frameless stereotactic systems provide feedback to the surgeon using virtual fluoroscopic images. The real-life accuracy of these virtual images has not been compared with traditional fluoroscopy in a clinical setting. We prospectively studied 23 consecutive cases. In two cases, registration errors precluded the use of virtual fluoroscopy. Pedicle probes placed with virtual fluoroscopic imaging were imaged with traditional fluoroscopy in the remaining 21 cases. Position of the probes was judged to be ideal, acceptable but not ideal, or not acceptable based on the traditional fluoroscopic images. Virtual fluoroscopy was used to place probes in for 97 pedicles from L1 to the sacrum. Eighty-eight probes were judged to be in ideal position, eight were judged to be acceptable but not ideal, and one probe was judged to be in an unacceptable position. This probe was angled toward an adjacent disc space. Therefore, 96 of 97 probes placed using virtual fluoroscopy were found to be in an acceptable position. The positive predictive value for acceptable screw placement with virtual fluoroscopy compared with traditional fluoroscopy was 99%. A probe placed with virtual fluoroscopic guidance will be judged to be in an acceptable position when imaged with traditional fluoroscopy 99% of the time.

Anterior transarticular C1-C2 fixation with contralateral screw insertion: a report of two cases and technical note.

PubMed

Lvov, Ivan; Grin, Andrey; Kaykov, Aleksandr; Smirnov, Vladimir; Krylov, Vladimir

2017-08-08

Anterior transarticular fixation of the C1-C2 vertebrae is a well-known technique that involves screw insertion through the body of the C2 vertebra into the lateral masses of the atlas through an anterior transcervical approach. Meanwhile, contralateral screw insertion has been previously described only in anatomical studies. We describe two case reports of the clinical application of this new technique. In Case 1, the patient was diagnosed with an unstable C1 fracture. The clinical features of the case did not allow for any type of posterior atlantoaxial fusion, Halo immobilization, or routine anterior fixation using the Reindl and Koller techniques. The possible manner of screw insertion into the anterior third of the right lateral mass was via a contralateral trajectory, which was performed in this case. Case 2 involved a patient with neglected posteriorly dislocated dens fracture who could not lie in the prone position due to concomitant cardiac pathology. Reduction of atlantoaxial dislocation was insufficient, even after scar tissue resection at the fracture, while transdental fusion was not possible. Considering the success of the previous case, atlantoaxial fixation was performed through the small approach, using the Reindl technique and contralateral screw insertion. These two cases demonstrate the potential of anterior transarticular fixation of C1-C2 vertebrae in cases where posterior atlantoaxial fusion is not achievable. This type of fixation can be performed through a single approach if one screw is inserted using the Reindl technique and another is inserted via a contralateral trajectory.

A biomechanical analysis of the self-retaining pedicle hook device in posterior spinal fixation

PubMed Central

van Laar, Wilbert; Meester, Rinse J.; Smit, Theo H.

2007-01-01

Regular hooks lack initial fixation to the spine during spinal deformity surgery. This runs the risk of posterior hook dislodgement during manipulation and correction of the spinal deformity, that may lead to loss of correction, hook migration, and post-operative junctional kyphosis. To prevent hook dislodgement during surgery, a self-retaining pedicle hook device (SPHD) is available that is made up of two counter-positioned hooks forming a monoblock posterior claw device. The initial segmental posterior fixation strength of a SPHD, however, is unknown. A biomechanical pull-out study of posterior segmental spinal fixation in a cadaver vertebral model was designed to investigate the axial pull-out strength for a SPHD, and compared to the pull-out strength of a pedicle screw. Ten porcine lumbar vertebral bodies were instrumented in pairs with two different instrumentation constructs after measuring the bone mineral density of each individual vertebra. The instrumentation constructs were extracted employing a material testing system using axial forces. The maximum pull-out forces were recorded at the time of the construct failure. Failure of the SPHD appeared in rotation and lateral displacement, without fracturing of the posterior structures. The average pull-out strength of the SPHD was 236 N versus 1,047 N in the pedicle screws (P < 0.001). The pull-out strength of the pedicle screws showed greater correlation with the BMC compared to the SPHD (P < 0.005). The SPHD showed to provide a significant inferior segmental fixation to the posterior spine in comparison to pedicle screw fixation. Despite the beneficial characteristics of the monoblock claw construct in a SPHD, that decreases the risk of posterior hook dislodgement during surgery compared to regular hooks, the SPHD does not improve the pull-out strength in such a way that it may provide a biomechanically solid alternative to pedicle screw fixation in the posterior spine. PMID:17203270

Removal torque of nail interlocking screws is related to screw proximity to the fracture and screw breakage.

PubMed

White, Alexander A; Kubacki, Meghan R; Samona, Jason; Telehowski, Paul; Atkinson, Patrick J

2016-06-01

Studies have shown that titanium implants can be challenging to explant due to the material's excellent biocompatibility and resulting osseointegration. Clinically, titanium alloy nail interlocking screws may require removal to dynamize a construct or revise the nail due to nonunion, infection, pain, or periprosthetic fracture. This study was designed to determine what variables influence the removal torque for titanium alloy interlocking screws. An intramedullary nail with four interlocking screws was used to stabilize a 1-cm segmental femoral defect in a canine model for 16 weeks. The animals were observed to be active following a several-day recovery after surgery. In six animals, the femora and implanted nail/screws were first tested to failure in torsion to simulate periprosthetic fracture of an implant after which the screws were then removed. In four additional animals, the screws were removed without mechanical testing. Both intraoperative insertional and extraction torques were recorded for all screws. Mechanical testing to failure broke 10/24 screws. On average, the intact screws required 70% of the insertional torque during removal while broken screws only required 16% of the insertional torque (p < 0.001). In addition, intact screws closer to the fracture required 2.8 times more removal torque than the outboard distal screw (p < 0.005). On average, the angle of rotation to peak torque was ∼80°. The peak axial load did not significantly correlate with the torque required to remove the screws. On average, the removal torque was lower than at the time of insertion, and less torque was required to remove broken screws and screws remote to the fracture. However, broken screws will require additional time to retrieve the remaining screw fragment. This study suggests that broken screws and screws in prematurely active patients will require less torque to remove. © IMechE 2016.

Selection of Fusion Levels Using the Fulcrum Bending Radiograph for the Management of Adolescent Idiopathic Scoliosis Patients with Alternate Level Pedicle Screw Strategy: Clinical Decision-making and Outcomes.

PubMed

Samartzis, Dino; Leung, Yee; Shigematsu, Hideki; Natarajan, Deepa; Stokes, Oliver; Mak, Kin-Cheung; Yao, Guanfeng; Luk, Keith D K; Cheung, Kenneth M C

2015-01-01

Selecting fusion levels based on the Luk et al criteria for operative management of thoracic adolescent idiopathic scoliosis (AIS) with hook and hybrid systems yields acceptable curve correction and balance parameters; however, it is unknown whether utilizing a purely pedicle screw strategy is effective. Utilizing the fulcrum bending radiographic (FBR) to assess curve flexibility to select fusion levels, the following study assessed the efficacy of pedicle screw fixation with alternate level screw strategy (ALSS) for thoracic AIS. A retrospective study with prospective radiographic data collection/analyses (preoperative, postoperative 1-week and minimum 2-year follow-up) of 28 operative thoracic AIS patients undergoing ALSS was performed. Standing coronal/sagittal and FBR Cobb angles, FBR flexibility, fulcrum bending correction index (FBCI), trunkal shift, radiographic shoulder height (RSH), and list were assessed on x-rays. Fusion level selection was based on the Luk et al criteria and compared to conventional techniques. In the primary curve, the mean preoperative and postoperative 1 week and last follow-up standing coronal Cobb angles were 59.9, 17.2 and 20.0 degrees, respectively. Eighteen patients (64.3%) had distal levels saved (mean: 1.6 levels) in comparison to conventional techniques. Mean immediate and last follow-up FBCIs were 122.6% and 115.0%, respectively. Sagittal alignment did not statistically differ between any assessment intervals (p>0.05). A decrease in trunkal shift was noted from preoperative to last follow-up (p = 0.003). No statistically significant difference from preoperative to last follow-up was noted in RSH and list (p>0.05). No "add-on" of other vertebra or decompensation was noted and all patients achieved fusion. This is the first report to note that using the FBR for decision-making in selecting fusion levels in thoracic AIS patients undergoing management with pedicle screw constructs (e.g. ALSS) is a cost-effective strategy that

CT Morphometric Analysis to Determine the Anatomical Basis for the Use of Transpedicular Screws during Reconstruction and Fixations of Anterior Cervical Vertebrae

PubMed Central

Chen, Chun; Ruan, Dike; Wu, Changfu; Wu, Weidong; Sun, Peidong; Zhang, Yuanzhi; Wu, Jigong; Lu, Sheng; Ouyang, Jun

2013-01-01

Background Accurate placement of pedicle screw during Anterior Transpedicular Screw fixation (ATPS) in cervical spine depends on accurate anatomical knowledge of the vertebrae. However, little is known of the morphometric characteristics of cervical vertebrae in Chinese population. Methods Three-dimensional reconstructions of CT images were performed for 80 cases. The anatomic data and screw fixation parameters for ATPS fixation were measured using the Mimics software. Findings The overall mean OPW, OPH and PAL ranged from 5.81 to 7.49 mm, 7.77 to 8.69 mm, and 33.40 to 31.13 mm separately, and SPA was 93.54 to 109.36 degrees from C3 to C6, 104.99 degrees at C7, whereas, 49.00 to 32.26 degrees from C4 to C7, 46.79 degrees at C3 (TPA). Dl/rSIP had an increasing trend away from upper endplate with mean value from 1.87 to 5.83 mm. Dl/rTIP was located at the lateral portion of the anterior cortex of vertebrae for C3 to C5 and ipsilateral for C6 to C7 with mean value from −2.70 to −3.00 mm, and 0.17 to 3.18 mm. The entrance points for pedicular screw insertion for C3 to C5 and C6 to C7 were recommended −2∼−3 mm and 0–4 mm from the median sagittal plane, respectively, 1–4 mm and 5–6 mm from the upper endplate, with TPA being 46.79–49.00 degrees and 40.89–32.26 degrees, respectively, and SPA being 93.54–106.69 degrees and 109.36–104.99 degrees, respectively. The pedicle screw insertion diameter was recommended 3.5 mm (C3 and C4), 4.0 mm (C5 to C7), and the pedicle axial length was 21–24 mm for C3 to C7 for both genders. However, the ATPS insertion in C3 should be individualized given its relatively small anatomical dimensions. Conclusions The data provided a morphometric basis for the ATPS fixation technique in lower cervical fixation. It will help in preoperative planning and execution of this surgery. PMID:24349038

Comparative Prospective Study Reporting Intraoperative Parameters, Pedicle Screw Perforation, and Radiation Exposure in Navigation-Guided versus Non-navigated Fluoroscopy-Assisted Minimal Invasive Transforaminal Lumbar Interbody Fusion

PubMed Central

Kundnani, Vishal; Dutta, Shumayou; Patel, Ankit; Mehta, Gaurav; Singh, Mahendra

2018-01-01

Study Design Prospective cohort study. Purpose To compare intraoperative parameters, radiation exposure, and pedicle screw perforation rate in navigation-guided versus non-navigated fluoroscopy-assisted minimal invasive transforaminal lumbar interbody fusion (MIS TLIF). Overview of Literature The poor reliability of fluoroscopy-guided instrumentation and growing concerns about radiation exposure have led to the development of navigation-guided instrumentation techniques in MIS TLIF. The literature evaluating the efficacy of navigation-guided MIS TLIF is scant. Methods Eighty-seven patients underwent navigation- or fluoroscopy-guided MIS TLIF for symptomatic lumbar/lumbosacral spondylolisthesis. Demographics, intraoperative parameters (surgical time, blood loss), and radiation exposure (sec/mGy/Gy.cm2 noted from C-arm for comparison only) were recorded. Computed tomography was performed in patients in the navigation and non-navigation groups at postoperative 12 months and reviewed by an independent observer to assess the accuracy of screw placement, perforation incidence, location, grade (Mirza), and critical versus non-critical neurological implications. Results Twenty-seven patients (male/female, 11/16; L4–L5/L5–S1, 9/18) were operated with navigation-guided MIS TLIF, whereas 60 (male/female, 25/35; L4–L5/L5–S1, 26/34) with conventional fluoroscopy-guided MIS TILF. The use of navigation resulted in reduced fluoroscopy usage (dose area product, 0.47 Gy.cm2 versus 2.93 Gy.cm2), radiation exposure (1.68 mGy versus 10.97 mGy), and fluoroscopy time (46.5 seconds versus 119.08 seconds), with p-values of <0.001. Furthermore, 96.29% (104/108) of pedicle screws in the navigation group were accurately placed (grade 0) (4 breaches, all grade I) compared with 91.67% (220/240) in the non-navigation group (20 breaches, 16 grade I+4 grade II; p=0.114). None of the breaches resulted in a corresponding neurological deficit or required revision. Conclusions Navigation

Subjective evaluation of treatment outcomes of instrumentation with pedicle screws or hybrid constructs in Lenke Type 1 and 2 adolescent idiopathic scoliosis: what happens when judges are blinded to the instrumentation?

PubMed Central

Ouellet, Jean Albert; Shilt, Jeffrey; Shen, Francis H.; Wood, Kirkham; Chan, Donald; Hicks, John; Bersusky, Ernesto; Reddi, Vasantha

2009-01-01

Superiority of pedicle screws over hybrid/hook instrumentation or vice versa in the treatment of Lenke Type 1 and 2 adolescent idiopathic scoliosis (AIS) remains unresolved for moderate curves. Our objective was therefore to compare the assessment of pedicle screw and hybrid/hooks instrumentation with special attention to cosmesis and uninstrumented spine using novel assessment methods. We carried out a retrospective study of radiographs and clinical photos of 40 cases of thoracic AIS between 40° and 70° of Cobb angle Lenke Type 1 and 2, treated with either pedicle screws or hybrid/hooks. The cases were subjectively assessed by four spine surgeons (SRS Travelling Fellows) for radiographic and operative cosmetic result, shoulder balance, trunk shift, rib hump, and waist asymmetry. Instrumentation in the radiographs was obscured with only the non-instrumented part visible, and the surgeons were asked to guess the instrumentation being used. Eighty photographs of patients before and after surgery were assessed for cosmesis by ten non-medical judges for overall cosmetic score, shoulder balance, waist asymmetry, and shoulder blade prominence. Objective assessment of radiographs and clinical photos was performed for Cobb angle of instrumented and non-instrumented spine, global coronal and sagittal balance, number of unfused vertebrae, disc angulation, tilt of last instrumented vertebra, shoulder balance, waist asymmetry, rib prominence, and percent correction. SRS-24 questionnaire was used to measure health-related quality of life in patients. Subjective assessments by surgeons and non-medical judges showed no significant difference by instrumentation (P ≥ 0.05) for all variables. Out of the 160 guesses by surgeons of the cases with instrumentation blocked in the radiographs, they were unable to guess the instrumentation in 92% of the cases. Objective assessment of all variables and SRS-24 scores of all five domains showed no significant difference by

Anterior debridement and fusion followed by posterior pedicle screw fixation in pyogenic spondylodiscitis: autologous iliac bone strut versus cage.

PubMed

Pee, Yong Hun; Park, Jong Dae; Choi, Young-Geun; Lee, Sang-Ho

2008-05-01

An anterior approach for debridement and fusion with autologous bone graft has been recommended as the gold standard for surgical treatment of pyogenic spondylodiscitis. The use of anterior foreign body implants at the site of active infection is still a challenging procedure for spine surgeons. Several authors have recently introduced anterior grafting with titanium mesh cages instead of autologous bone strut in the treatment of spondylodiscitis. The authors present their experience of anterior fusion with 3 types of cages followed by posterior pedicle screw fixation. They also compare their results with the use of autologous iliac bone strut. The authors retrospectively reviewed the cases of 60 patients with pyogenic spondylodiscitis treated by anterior debridement between January 2003 and April 2005. Fusion using either cages or iliac bone struts was performed during the same course of anesthesia followed by posterior fixation. Twenty-three patients underwent fusion with autologous iliac bone strut, and 37 patients underwent fusion with 1 of the 3 types of cages. The infections resolved in all patients, as noted by normalization of their erythrocyte sedimentation rates and C-reactive protein levels. Patients in both groups were evaluated in terms of their preoperative and postoperative clinical and imaging findings. Single-stage anterior debridement and cage fusion followed by posterior pedicle screw fixation can be effective in the treatment of pyogenic spondylodiscitis. There was no difference in clinical and imaging outcomes between the strut group and cage group except for the subsidence rate. The subsidence rate was higher in the strut group than in the cage group. The duration until subsidence was also shorter in the strut group than in the cage group.

Absent pedicles in campomelic dysplasia.

PubMed

McDowell, Michael M; Dede, Ozgur; Bosch, Patrick; Tyler-Kabara, Elizabeth C

2017-06-01

The objective of the present study is to report a case of campomelic dysplasia illustrating the absence of cervical and thoracic pedicles. This report reiterates the importance of this clinical peculiarity in the setting of spine instrumentation. A 10-year-old female patient with campomelic dysplasia presented with progressive kyphoscoliosis and signs of neural compromise. Imaging studies confirmed thoracic level stenosis and demonstrated absence of multiple pedicles in cervical and thoracic spine. The patient underwent decompression and instrumentation/fusion for her spinal deformity. The patient was instrumented between C2 and L4 with pedicle screws and sublaminar cables. However, pedicle fixation was not possible for the lower cervical and upper-mid thoracic spine. Also, floating posterior elements precluded the use of laminar fixation in the lower cervical spine. Cervicothoracic lumbosacral orthosis (CTLSO) was used for external immobilization to supplement the tenuous fixation in the cervicothoracic area. The patient improved neurologically with no signs of implant failure at the 2-year follow-up. Absence of pedicles and floating posterior elements present a challenge during spine surgery in campomelic dysplasia. Surgeons should prepare for alternative fixation methods and external immobilization when planning on spinal instrumentation in affected patients. Level IV Case Report.

Pullout strength of cancellous screws in human femoral heads depends on applied insertion torque, trabecular bone microarchitecture and areal bone mineral density.

PubMed

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

2014-12-01

For cancellous bone screws, the respective roles of the applied insertion torque (TInsert) and of the quality of the host bone (microarchitecture, areal bone mineral density (aBMD)), in contributing to the mechanical holding strength of the bone-screw construct (FPullout), are still unclear. During orthopaedic surgery screws are tightened, typically manually, until adequate compression is attained, depending on surgeons' manual feel. This corresponds to a subjective insertion torque control, and can lead to variable levels of tightening, including screw stripping. The aim of this study, performed on cancellous screws inserted in human femoral heads, was to investigate which, among the measurements of aBMD, bone microarchitecture, and the applied TInsert, has the strongest correlation with FPullout. Forty six femoral heads were obtained, over which microarchitecture and aBMD were evaluated using micro-computed tomography and dual X-ray absorptiometry. Using an automated micro-mechanical test device, a cancellous screw was inserted in the femoral heads at TInsert set to 55% to 99% of the predicted stripping torque beyond screw head contact, after which FPullout was measured. FPullout exhibited strongest correlations with TInsert (R=0.88, p<0.001), followed by structure model index (SMI, R=-0.81, p<0.001), bone volume fraction (BV/TV, R=0.73, p<0.001) and aBMD (R=0.66, p<0.01). Combinations of TInsert with microarchitectural parameters and/or aBMD did not improve the prediction of FPullout. These results indicate that, for cancellous screws, FPullout depends most strongly on the applied TInsert, followed by microarchitecture and aBMD of the host bone. In trabecular bone, screw tightening increases the holding strength of the screw-bone construct. Copyright © 2014 Elsevier Ltd. All rights reserved.

Clinical Outcomes of Posterior C1 and C2 Screw-Rod Fixation for Atlantoaxial Instability.

PubMed

Işik, Hasan Serdar; Sandal, Evren; Çağli, Sedat

2017-06-14

In this study, we aimed at sharing our experiences and contributing to the literature by making a retrospective analysis of the patients we operated with screw-rod system for atlantoaxial instability in our clinic. Archive files of adult patients, who were operated for posterior C1-C2 stabilization with screw and rod in our clinic between January 2006 and January 2016, were analyzed. 28 patients, who had pre and post-operative images, follow-up forms and who were followed for at least one year, were analyzed. Preoperative clinical and radiological records, preoperative observations, postoperative complications, and clinical responses were evaluated. The average age of 28 patients (F:13 M:19) was 44.7 (21-73). Fixation was performed with C1-C2 screw-rod system on the basis of the following diagnoses; type 2 odontoid fracture (16), basilar invagination (5), C1-C2 instability (5), and atlantoaxial subluxation secondary to rheumatoid arthritis (2). Lateral mass screws were inserted at C1 segment. C2 screws inserted were bilateral pedicle in 12 cases, bilateral pars in 4, bilateral laminar in 8 and one side pars, one side laminar in 4 cases. There was no screw malposition. Neither implant failure nor recurrent instability was observed during follow-up. Significant clinical improvement was reported according to the assessments done with JOA and VAS scores. C1-C2 screw fixation is regarded as a more successful and safe method than other fixation methods in surgical treatment of atlantoaxial instability considering complications, success in reduction, fusion and fixation strength. C2 laminar screw technique is as successful as the other alternatives in fixation and fusion.

Safe insertion of S-2 alar iliac screws: radiological comparison between 2 insertion points using computed tomography and 3D analysis software.

PubMed

Yamada, Kentaro; Abe, Yuichiro; Satoh, Shigenobu

2018-05-01

OBJECTIVE S-2 alar iliac (S2AI) screws are commonly used as anchors for lumbosacral fixation. A serious potential complication of screw insertion is major vascular injury due to anterior or caudal screw deviation. To avoid screw deviation, the pelvic inlet view on intraoperative fluoroscopy images is recommended. However, there has been no detailed investigation of optimal fluoroscopic incline with the pelvic inlet view. The purpose of this study was to investigate the safety margins and to optimize fluoroscopic settings to avoid screw deviation with 2 reported insertion techniques using 3D analysis software and CT. METHODS The study included 50 patients (25 men and 25 women) who underwent abdominal-pelvic CT. With the use of software, the ideal S2AI screws were set from 2 entry points: A) the midpoint between the S-1 dorsal foramen and the S-2 dorsal foramen where they meet the lateral sacral crest, and B) 1 mm inferior and 1 mm lateral to the S-1 dorsal foramen. Anteriorly or caudally deviated screws were defined as deviation of a half thread of the ideal screw by rotation anteriorly or caudally from the entry point. The angular safety margins were compared between the 2 entry points, and patients with small safety margins were investigated. Subsequently, fluoroscopic images were virtualized on ray sum-rendered images. Conditions that provided proper recognition of screw deviation were investigated via lateral and anteroposterior views with the beam tilted caudally. RESULTS The safety margins of S2AI screws were smaller in the anterior direction than in the caudal direction and by entry point A than by entry point B (A: 9.1° ± 1.6° and B: 9.7° ± 1.5° in the anterior direction; A: 10.9° ± 3.8° and B: 13.9° ± 4.1° in the caudal direction). In contrast, patients with a deep-seated L-5 vertebral body tended to have smaller safety margins in the caudal direction. All anteriorly deviated screws were recognized with a 60°-70° inlet view from the S-1 slope

Revisions for screw malposition and clinical outcomes after robot-guided lumbar fusion for spondylolisthesis.

PubMed

Schröder, Marc L; Staartjes, Victor E

2017-05-01

24.3 ± 28.3) and ODI (from 43.4 ± 18.3 to 16.2 ± 16.7; all p < 0.001). Undergoing PLIF, a high body mass index, smoking status, and a preoperative ability to work were identified as predictors of a reduction in back pain. Length of hospital stay was 2.4 ± 1.1 days and operating time was 161 ± 50 minutes. Ability to work increased from 38.9% to 78.2% of patients (p < 0.001) at the final follow-up, and 89.1% of patients indicated they would choose to undergo the same treatment again. CONCLUSIONS In adults with low-grade spondylolisthesis, the data demonstrated a benefit in using robotic guidance to reduce the rate of revision surgery for screw malposition as compared with other techniques of pedicle screw insertion described in peer-reviewed publications. Larger comparative studies are required to assess differences in PROs following a minimally invasive approach in spinal fusion surgeries compared with other techniques.

Temporary short-segment pedicle screw fixation for thoracolumbar burst fractures: comparative study with or without vertebroplasty.

PubMed

Aono, Hiroyuki; Ishii, Keisuke; Tobimatsu, Hidekazu; Nagamoto, Yukitaka; Takenaka, Shota; Furuya, Masayuki; Chiaki, Horii; Iwasaki, Motoki

2017-08-01

Short-segment posterior spinal instrumentation for thoracolumbar burst fracture provides superior correction of kyphosis by an indirect reduction technique, but it has a high failure rate. The purpose of the study we report here was to compare outcomes for temporary short-segment pedicle screw fixation with vertebroplasty and for such fixation without vertebroplasty. This is a prospective multicenter comparative study. We studied 62 consecutive patients with thoracolumbar burst fracture who underwent short-segment posterior instrumentation using ligamentotaxis with Schanz screws with or without vertebroplasty. Radiological parameters (Cobb angle on standing lateral radiographs) were used. Implants were removed approximately 1 year after surgery. Neurologic function, kyphotic deformity, canal compromise, and fracture severity were evaluated prospectively. After surgery, all patients with neurologic deficit had improvement equivalent to at least one grade on the American Spinal Injury Association impairment scale and had fracture union. Kyphotic deformity was reduced significantly, and reduction of the vertebrae was maintained with and without vertebroplasty, regardless of load-sharing classification. Although no patient required additional anterior reconstruction, kyphotic change was observed at disc level mainly after implant removal with or without vertebroplasty. Temporary short-segment fixation yielded satisfactory results in the reduction and maintenance of fractured vertebrae with or without vertebroplasty. Kyphosis recurrence may be inevitable because adjacent discs can be injured during the original trauma. Copyright © 2017 Elsevier Inc. All rights reserved.

Ultrasound melted polymer sleeve for improved screw anchorage in trabecular bone--A novel screw augmentation technique.

PubMed

Schmoelz, W; Mayr, R; Schlottig, F; Ivanovic, N; Hörmann, R; Goldhahn, J

2016-03-01

Screw anchorage in osteoporotic bone is still limited and makes treatment of osteoporotic fractures challenging for surgeons. Conventional screws fail in poor bone quality due to loosening at the screw-bone interface. A new technology should help to improve this interface. In a novel constant amelioration process technique, a polymer sleeve is melted by ultrasound in the predrilled screw hole prior to screw insertion. The purpose of this study was to investigate in vitro the effect of the constant amelioration process platform technology on primary screw anchorage. Fresh frozen femoral heads (n=6) and vertebrae (n=6) were used to measure the maximum screw insertion torque of reference and constant amelioration process augmented screws. Specimens were cut in cranio-caudal direction, and the screws (reference and constant amelioration process) were implanted in predrilled holes in the trabecular structure on both sides of the cross section. This allowed the pairwise comparison of insertion torque for constant amelioration process and reference screws (femoral heads n=18, vertebrae n=12). Prior to screw insertion, a micro-CT scan was made to ensure comparable bone quality at the screw placement location. The mean insertion torque for the constant amelioration process augmented screws in both, the femoral heads (44.2 Ncm, SD 14.7) and the vertebral bodies (13.5 Ncm, SD 6.3) was significantly higher than for the reference screws of the femoral heads (31.7 Ncm, SD 9.6, p<0.001) and the vertebral bodies (7.1 Ncm, SD 4.5, p<0.001). The interconnection of the melted polymer sleeve with the surrounding trabecular bone in the constant amelioration process technique resulted in a higher screw insertion torque and can improve screw anchorage in osteoporotic trabecular bone. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biomechanical advantages of robot-assisted pedicle screw fixation in posterior lumbar interbody fusion compared with freehand technique in a prospective randomized controlled trial-perspective for patient-specific finite element analysis.

PubMed

Kim, Ho-Joong; Kang, Kyoung-Tak; Park, Sung-Cheol; Kwon, Oh-Hyo; Son, Juhyun; Chang, Bong-Soon; Lee, Choon-Ki; Yeom, Jin S; Lenke, Lawrence G

2017-05-01

There have been conflicting results on the surgical outcome of lumbar fusion surgery using two different techniques: robot-assisted pedicle screw fixation and conventional freehand technique. In addition, there have been no studies about the biomechanical issues between both techniques. This study aimed to investigate the biomechanical properties in terms of stress at adjacent segments using robot-assisted pedicle screw insertion technique (robot-assisted, minimally invasive posterior lumbar interbody fusion, Rom-PLIF) and freehand technique (conventional, freehand, open approach, posterior lumbar interbody fusion, Cop-PLIF) for instrumented lumbar fusion surgery. This is an additional post-hoc analysis for patient-specific finite element (FE) model. The sample is composed of patients with degenerative lumbar disease. Intradiscal pressure and facet contact force are the outcome measures. Patients were randomly assigned to undergo an instrumented PLIF procedure using a Rom-PLIF (37 patients) or a Cop-PLIF (41), respectively. Five patients in each group were selected using a simple random sampling method after operation, and 10 preoperative and postoperative lumbar spines were modeled from preoperative high-resolution computed tomography of 10 patients using the same method for a validated lumbar spine model. Under four pure moments of 7.5 Nm, the changes in intradiscal pressure and facet joint contact force at the proximal adjacent segment following fusion surgery were analyzed and compared with preoperative states. The representativeness of random samples was verified. Both groups showed significant increases in postoperative intradiscal pressure at the proximal adjacent segment under four moments, compared with the preoperative state. The Cop-PLIF models demonstrated significantly higher percent increments of intradiscal pressure at proximal adjacent segments under extension, lateral bending, and torsion moments than the Rom-PLIF models (p=.032, p=.008, and p

Pedicle distraction increases intervertebral and spinal canal area in a cadaver and bone model

PubMed Central

Hughes, Matthew; Papadakos, Nikolaos; Bishop, Tim; Bernard, Jason

2018-01-01

Introduction: Lumbar spinal stenosis is degenerative narrowing of the spinal canal and/or intervertebral foramen causing compression of the spinal cord and nerve roots. Traditional decompression techniques can often cause significant trauma and vertebral instability. This paper evaluates a method of increasing pedicle length to decompress the spinal and intervertebral foramen, which could be done minimally invasive. Methods: Three Sawbone (Sawbones Europe, Sweden) and 1 cadaveric lumbar spine underwent bilateral pedicle distraction at L4. A pedicle channel was drilled between the superior articular process and transverse process into the vertebral body. The pedicles underwent osteotomy at the midpoint. Screws were inserted bilaterally and fixated distraction of 0 mm, 2 mm, 4 mm and 6 mm. CT images were taken at each level of distraction. Foramen area was measured in the sagittal plane at L3/4. Spinal canal area was measured at L4 in the axial images. The cadaver was used to evaluate safety of osteotomy and soft tissue interactions preventing distraction. Statistical analysis was by student paired t-test and Pearson rank test. Results: Increasing distraction led to greater Spinal canal area. From 4.27 cm2 to 5.72 cm2 (p = 0.002) with 6 mm distraction. A Maximal increase of 34.1%. Vertebral foramen area also increased with increasing pedicle distraction. From 2.43 cm2 to 3.22 cm2 (p = 0.022) with 6 mm distraction. A maximal increase of 32.3%. The cadaver spinal canal increased in area by 21.7%. The vertebral foramen increased in area by 36.2% (left) and 22.6% (right). Discussion: For each increase in pedicle distraction the area of the spinal and vertebral foramen increases. Pedicle distraction could potentially be used to alleviate spinal stenosis and root impingement. A potential osteotomy plane could be at the midpoint of the pedicle with minimal risk to nerve roots and soft tissue restrictions to prevent distraction. PMID:29727270

Pedicle distraction increases intervertebral and spinal canal area in a cadaver and bone model.

PubMed

Hughes, Matthew; Papadakos, Nikolaos; Bishop, Tim; Bernard, Jason

2018-01-01

Lumbar spinal stenosis is degenerative narrowing of the spinal canal and/or intervertebral foramen causing compression of the spinal cord and nerve roots. Traditional decompression techniques can often cause significant trauma and vertebral instability. This paper evaluates a method of increasing pedicle length to decompress the spinal and intervertebral foramen, which could be done minimally invasive. Three Sawbone (Sawbones Europe, Sweden) and 1 cadaveric lumbar spine underwent bilateral pedicle distraction at L4. A pedicle channel was drilled between the superior articular process and transverse process into the vertebral body. The pedicles underwent osteotomy at the midpoint. Screws were inserted bilaterally and fixated distraction of 0 mm, 2 mm, 4 mm and 6 mm. CT images were taken at each level of distraction. Foramen area was measured in the sagittal plane at L3/4. Spinal canal area was measured at L4 in the axial images. The cadaver was used to evaluate safety of osteotomy and soft tissue interactions preventing distraction. Statistical analysis was by student paired t-test and Pearson rank test. Increasing distraction led to greater Spinal canal area. From 4.27 cm 2 to 5.72 cm 2 (p = 0.002) with 6 mm distraction. A Maximal increase of 34.1%. Vertebral foramen area also increased with increasing pedicle distraction. From 2.43 cm 2 to 3.22 cm 2 (p = 0.022) with 6 mm distraction. A maximal increase of 32.3%. The cadaver spinal canal increased in area by 21.7%. The vertebral foramen increased in area by 36.2% (left) and 22.6% (right). For each increase in pedicle distraction the area of the spinal and vertebral foramen increases. Pedicle distraction could potentially be used to alleviate spinal stenosis and root impingement. A potential osteotomy plane could be at the midpoint of the pedicle with minimal risk to nerve roots and soft tissue restrictions to prevent distraction. © The Authors, published by EDP Sciences, 2018.

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

Insertion torque in different bone models with different screw pitch: an in vitro study.

PubMed

Orlando, Bruno; Barone, Antonio; Giorno, Thierry M; Giacomelli, Luca; Tonelli, Paolo; Covani, Ugo

2010-01-01

Orthopedic surgeons use different types of screws for bone fixation. Whereas hard cortical bone requires a screw with a fine pitch, in softer cancellous bone a wider pitch might help prevent micromotion and eventually lead to greater implant stability. The aim of this study was to validate the assumption that fine-pitch implants are appropriate for cortical bone and wide-pitch implants are appropriate for cancellous bone. Wide-pitch and fine-pitch implants were inserted in both hard (D1 and D2) bone and soft (D3 and D4) bone, which was simulated by separate experimental blocks of cellular rigid polyurethane foam. A series of insertion sites in D1-D2 and D3-D4 experimental blocks were prepared using 1.5-mm and 2.5-mm drills. The final torque required to insert each implant was recorded. Wide-pitch implants displayed greater insertion torque (20% more than the fine-pitch implants) in cancellous bone and were therefore more suitable than fine-pitch implants. It is more appropriate to use a fine pitch design for implants, in conjunction with a 2.5-mm osteotomy site, in dense cortical bone (D1 or D2), whereas it is recommended to choose a wide-pitch design for implants, in conjunction with a 1.5-mm osteotomy site, in softer bone (D3 or D4).

Development and validation of a quantitative method to assess pedicle screw loosening in posterior spine instrumentation on plain radiographs.

PubMed

Aghayev, Emin; Zullig, Nicolas; Diel, Peter; Dietrich, Daniel; Benneker, Lorin M

2014-03-01

Currently, the diagnosis of pedicle screw (PS) loosening is based on a subjectively assessed halo sign, that is, a radiolucent line around the implant wider than 1 mm in plain radiographs. We aimed at development and validation of a quantitative method to diagnose PS loosening on radiographs. Between 11/2004 and 1/2010 36 consecutive patients treated with thoraco-lumbar spine fusion with PS instrumentation without PS loosening were compared with 37 other patients who developed a clinically manifesting PS loosening. Three different angles were measured and compared regarding their capability to discriminate the loosened PS over the postoperative course. The inter-observer invariance was tested and a receiver operating characteristics curve analysis was performed. The angle measured between the PS axis and the cranial endplate was significantly different between the early and all later postoperative images. The Spearman correlation coefficient for the measurements of two observers at each postoperative time point ranged between 0.89 at 2 weeks to 0.94 at 2 months and 1 year postoperative. The angle change of 1.9° between immediate postoperative and 6-month postoperative was 75% sensitive and 89% specific for the identification of loosened screws (AUC = 0.82). The angle between the PS axis and the cranial endplate showed good ability to change in PS loosening. A change of this angle of at least 2° had a relatively high sensitivity and specificity to diagnose screw loosening.

Biomechanical measurements of stopping and stripping torques during screw insertion in five types of human and artificial humeri.

PubMed

Aziz, Mina Sr; Tsuji, Matthew Rs; Nicayenzi, Bruce; Crookshank, Meghan C; Bougherara, Habiba; Schemitsch, Emil H; Zdero, Radovan

2014-05-01

During orthopedic surgery, screws are inserted by "subjective feel" in humeri for fracture fixation, that is, stopping torque, while trying to prevent accidental over-tightening that causes screw-bone interface failure, that is, stripping torque. However, no studies exist on stopping torque, stripping torque, or stopping/stripping torque ratio in human or artificial humeri. This study evaluated five types of humeri, namely, human fresh-frozen (n = 19), human embalmed (n = 18), human dried (n = 15), artificial "normal" (n = 13), and artificial "osteoporotic" (n = 13). An orthopedic surgeon used a torque screwdriver to insert 3.5-mm-diameter cortical screws into humeral shafts and 6.5-mm-diameter cancellous screws into humeral heads by "subjective feel" to obtain stopping and stripping torques. The five outcome measures were raw and normalized stopping torque, raw and normalized stripping torque, and stopping/stripping torque ratio. Normalization was done as raw torque/screw-bone interface area. For "gold standard" fresh-frozen humeri, cortical screw tests yielded averages of 1312 N mm (raw stopping torque), 30.4 N/mm (normalized stopping torque), 1721 N mm (raw stripping torque), 39.0 N/mm (normalized stripping torque), and 82% (stopping/stripping torque ratio). Similarly, fresh-frozen humeri gave cancellous screw average results of 307 N mm (raw stopping torque), 0.9 N/mm (normalized stopping torque), 392 N mm (raw stripping torque), 1.2 N/mm (normalized stripping torque), and 79% (stopping/stripping torque ratio). Of the five cortical screw parameters for fresh-frozen humeri versus other groups, statistical equivalence (p ≥ 0.05) occurred in four cases (embalmed), three cases (dried), four cases (artificial "normal"), and four cases (artificial "osteoporotic"). Of the five cancellous screw parameters for fresh-frozen humeri versus other groups, statistical equivalence (p ≥ 0.05) occurred in five cases (embalmed), one case (dried), one case (artificial "normal

Is There Asymmetry Between the Concave and Convex Pedicles in Adolescent Idiopathic Scoliosis? A CT Investigation.

PubMed

Davis, Colin M; Grant, Caroline A; Pearcy, Mark J; Askin, Geoffrey N; Labrom, Robert D; Izatt, Maree T; Adam, Clayton J; Little, J Paige

2017-03-01

.72 mm ± 1.02 mm; p < 0.001; mean difference, 1.27 mm; 95% CI, 0.92 mm-1.62 mm), 32% (3.66 mm ± 1.00 mm vs 4.82 mm ± 1.10 mm; p < 0.001; mean difference, 1.16 mm; 95% CI, 0.84 mm-1.49 mm), and 25% (4.10 mm ± 1.57 mm vs 5.12 mm ± 1.17 mm; p < 0.001; mean difference, 1.02 mm; 95% CI, 0.66 mm-1.39 mm), respectively. The concave pedicle heights were smaller than the convex at T5 (9.43 mm ± 0.98 vs 10.63 mm ± 1.10 mm; p = 0.002; mean difference, 1.02 mm; 95% CI, 0.59 mm-1.45 mm), T6 (8.87 mm ± 1.37 mm vs 10.88 mm ± 0.81 mm; p < 0.001; mean difference, 2.02 mm; 95% CI, 1.40 mm-2.63 mm), T7 (9.09 mm ± 1.24 mm vs 11.35 mm ± 0.84 mm; p < 0.001; mean difference, 2.26 mm; 95% CI, 1.81 mm-2.72 mm), and T8 (10.11 mm ± 1.05 mm vs 11.86 mm ± 0.88 mm; p < 0.001; mean difference, 1.75 mm; 95% CI, 1.30 mm-2.19 mm). Conversely, the concave transverse pedicle angle was larger than the convex at levels T6 (11.37° ± 4.48° vs 8.82° ± 4.31°; p = 0.004; mean difference, 2.54°; 95% CI, 1.10°-3.99°), T7 (12.69° ± 5.93° vs 8.65° ± 3.79°; p = 0.002; mean difference, 4.04°; 95% CI, 1.90°-6.17°), T8 (13.24° ± 5.28° vs 7.66° ± 4.87°; p < 0.001; mean difference, 5.58°; 95% CI, 2.99°-8.17°), and T9 (19.95° ± 5.69° vs 8.21° ± 4.02°; p < 0.001; mean difference, 4.74°; 95% CI, 2.68°-6.80°), indicating a more posterolateral to anteromedial pedicle orientation. There is clinically important asymmetry in the morphologic features of pedicles in individuals with adolescent idiopathic scoliosis. The concave side of the curve compared with the convex side is smaller in height and width periapically. Furthermore, the trajectory of the pedicle is more acute on the convex side of the curve compared with the concave side around the apex of the curve. Knowledge of these anatomic variations is essential when performing scoliosis correction surgery to assist with selecting the correct pedicle screw size and trajectory of insertion to reduce the risk of pedicle wall

The fates of pedicle screws and functional outcomes in a geriatric population following polymethylmethacrylate augmentation fixation for the osteoporotic thoracolumbar and lumbar burst fractures with mean ninety five month follow-up.

PubMed

Lin, Hsi-Hsien; Chang, Ming-Chau; Wang, Shih-Tien; Liu, Chien-Lin; Chou, Po-Hsin

2018-06-01

Polymethylmethacrylate (PMMA) augmentation is a common method to increase pullout strength fixed for osteoporotic spines. However, few papers evaluated whether these pedicle screws migrated with time and functional outcome in these geriatrics following PMMA-augmented pedicle screw fixation. From March 2006 to September 2008, consecutive 64 patients were retrospectively enrolled. VAS and ODI were used to evaluate functional outcomes. Kyphotic angle at instrumented levels and horizontal and vertical distances (HD and VD) between screw tip and anterior and upper cortexes were evaluated. To avoid bias, we used horizontal and vertical migration index (HMI and VMI) to re-evaluate screw positions with normalization by the mean of superior and inferior endplates or anterior and posterior vertebral body height, respectively. Forty-six patients with 282 PMMA-augmented screws were analyzed with mean follow-up of 95 months. Nine patients were further excluded due to bed-ridden at latest follow-up. Twenty-six females and 11 males with mean T score of - 2.7 (range, - 2.6 to - 4.1) and mean age for operation of 77.6 ± 4.3 years (range, 65 to 86). The serial HD and kyphotic angle statistically progressed with time. The serial VD did not statistically change with time (p = 0.23), and neither HMI nor VMI (p = 0.772 and 0.631). Pre-operative DEXA results did not correlate with kyphotic angle. Most patients (80.4%) maintained similar functional outcomes at latest follow-up. The incidence of screws loosening was 2.7% of patients and 1.4% of screws, respectively. The overall incidences of systemic post-operative co-morbidities were 24.3% with overall 20.2 days for hospitalization. Most patients (80%) remained similar functional outcomes at latest follow-up in spite of kyphosis progression. The incidence of implant failure was not high, but the post-operative systemic co-morbidities were higher, which has to be informed before index surgery.

Bi-Pedicle Fixation of Affected Vertebra in Thoracolumbar Burst Fracture.

PubMed

Padalkar, Pravin; Mehta, Varshil

2017-04-01

Burst fractures of the spine account for 14% of all spinal injuries and more than 50% of all thoracolumbar trauma. However, there is ambiguity while choosing the right treatment plan. Short Segment Pedicle screw Fixation (SSPF) has become an increasingly popular method of treatment of thoracolumbar burst fractures, providing the advantage of incorporating fewer motion segments in the fixation. Various biomechanical studies showed that the use of pedicle screws could achieve stable construct within short-segment fixation. To evaluate the efficacy of SSPF using longest possible screws in both pedicles of fractured vertebra. A retrospective chart review of 25 single burst thoracolumbar fracture patients, operated between May 2009 to 2015 in a tertiary care trauma center, was conducted. Preoperative and post-operative plain radiographs were evaluated for kyphotic angulations using the traditional Cobb method. Anterior Vertebral Height (AVH), Posteriors Vertebral Height (PVH) were measured preoperatively and immediate postoperatively. Average percentage loss of AVH and mid-sagittal height were calculated on preoperative and postoperative X-rays on follow up. Fourteen men and 11 women with an average age of 42.92 years comprised the study population. Mean age at the time of operation was 34.5±14.2 years. Mean operation time was 168±72 (minutes). Average hospitalization time was 9±7 (days). Mean blood loss was 515±485 (ml). There were two cases of postoperative infection and implant failure each. A mean of 15.2° of kyphosis correction was attained from pre-operation to post-operation (p<0.0001). Although, there was a 15° average improvement of kyphosis post-fixation, loss of correction over time was nearly 8°, resulting in a 7° mean correction of kyphosis. A mean loss of AVH on postoperative radiograph was 6.12% and maintained 12.4% at the time of review (p<0.001). Similarly, there was 32.8% mid-sagittal height loss at time of injury, which was improved to only 12

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

2017-06-01

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

BIOMECHANICAL EVALUATION OF THE INFLUENCE OF CERVICAL SCREWS TAPPING AND DESIGN.

PubMed

Silva, Patricia; Rosa, Rodrigo César; Shimano, Antonio Carlos; Albuquerque de Paula, Francisco José; Volpon, José Batista; Aparecido Defino, Helton Luiz

2009-01-01

To assess if the screw design (self-drilling/self-tapping) and the pilot hole tapping could affect the insertion torque and screw pullout strength of the screw used in anterior fixation of the cervical spine. Forty self-tapping screws and 20 self-drilling screws were inserted into 10 models of artificial bone and 10 cervical vertebrae of sheep. The studied parameters were the insertion torque and pullout strength. The following groups were created: Group I-self-tapping screw insertion after pilot hole drilling and tapping; Group II-self-tapping screw insertion after pilot hole drilling without tapping; Group III-self-drilling screw insertion without drilling and tapping. In Groups I and II, the pilot hole had 14.0 mm in depth and was made with a 3mmn drill, while tapping was made with a 4mm tap. The insertion torque was measured and the pullout test was performed. The comparison between groups was made considering the mean insertion torque and the maximum mean pullout strength with the variance analysis (ANOVA; p≤ 0.05). Previous drilling and tapping of pilot hole significantly decreased the insertion torque and the pullout strength. The insertion torque and pullout strength of self-drilling screws were significantly higher when compared to self-tapping screws inserted after pilot hole tapping.

Desktop-based computer-assisted orthopedic training system for spinal surgery.

PubMed

Rambani, Rohit; Ward, James; Viant, Warren

2014-01-01

Simulation and surgical training has moved on since its inception during the end of the last century. The trainees are getting more exposed to computers and laboratory training in different subspecialties. More needs to be done in orthopedic simulation in spinal surgery. To develop a training system for pedicle screw fixation and validate its effectiveness in a cohort of junior orthopedic trainees. Fully simulated computer-navigated training system is used to train junior orthopedic trainees perform pedicle screw insertion in the lumbar spine. Real patient computed tomography scans are used to produce the real-time fluoroscopic images of the lumbar spine. The training system was developed to simulate pedicle screw insertion in the lumbar spine. A total of 12 orthopedic senior house officers performed pedicle screw insertion in the lumbar spine before and after the training on training system. The results were assessed based on the scoring system, which included the amount of time taken, accuracy of pedicle screw insertion, and the number of exposures requested to complete the procedure. The result shows a significant improvement in amount of time taken, accuracy of fixation, and the number of exposures after the training on simulator system. This was statistically significant using paired Student t test (p < 0.05). Fully simulated computer-navigated training system is an efficient training tool for young orthopedic trainees. This system can be used to augment training in the operating room, and trainees acquire their skills in the comfort of their study room or in the training room in the hospital. The system has the potential to be used in various other orthopedic procedures for learning of technical skills in a manner aimed at ensuring a smooth escalation in task complexity leading to the better performance of procedures in the operating theater. Copyright © 2014 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

iPod touch-assisted instrumentation of the spine: a technical report.

PubMed

Jost, Gregory F; Bisson, Erica F; Schmidt, Meic H

2013-12-01

Instrumentation of the spine depends on choosing the correct insertion angles to implant screws. Although modern image guidance facilitates precise instrumentation of the spine, the equipment is costly and availability is limited. Although most surgeons use lateral fluoroscopy to guide instrumentation in the sagittal plane, the lateromedial angulation is often chosen by estimation. To overcome the associated uncertainty, iPod touch-based applications for measuring angles can be used to assist with screw implantation. To evaluate the use of the iPod touch to adjust instruments to the optimal axial insertion angle for placement of pedicle screws in the lumbar spine. Twenty lumbar pedicle screws in 5 consecutive patients were implanted using the iPod touch. The lateromedial angulation was measured on preoperative images and reproduced in the operative field with the iPod touch. The instruments to implant the screws were aligned with the side of the iPod for screw insertion. Actual screw angles were remeasured on postoperative imaging. We collected demographic, clinical, and operative data for each patient. In 16 of 20 screws, the accuracy of implantation was within 3 degrees of the ideal trajectory. The 4 screws with an angle mismatch of 7 to 13 degrees were all implanted at the caudal end of the exposure, where maintaining the planned angulation was impeded by strong muscles pushing medially. iPod touch-assisted instrumentation of the spine is a very simple technique, which, in combination with a lateral fluoroscopy, may guide placement of pedicle screws in the lumbar spine.

Biomechanics of lateral lumbar interbody fusion constructs with lateral and posterior plate fixation: laboratory investigation.

PubMed

Fogel, Guy R; Parikh, Rachit D; Ryu, Stephen I; Turner, Alexander W L

2014-03-01

Lumbar interbody fusion is indicated in the treatment of degenerative conditions. Laterally inserted interbody cages significantly decrease range of motion (ROM) compared with other cages. Supplemental fixation options such as lateral plates or spinous process plates have been shown to provide stability and to reduce morbidity. The authors of the current study investigate the in vitro stability of the interbody cage with a combination of lateral and spinous process plate fixation and compare this method to the established bilateral pedicle screw fixation technique. Ten L1-5 specimens were evaluated using multidirectional nondestructive moments (± 7.5 N · m), with a custom 6 degrees-of-freedom spine simulator. Intervertebral motions (ROM) were measured optoelectronically. Each spine was evaluated under the following conditions at the L3-4 level: intact; interbody cage alone (stand-alone); cage supplemented with lateral plate; cage supplemented with ipsilateral pedicle screws; cage supplemented with bilateral pedicle screws; cage supplemented with spinous process plate; and cage supplemented with a combination of lateral plate and spinous process plate. Intervertebral rotations were calculated, and ROM data were normalized to the intact ROM data. The stand-alone laterally inserted interbody cage significantly reduced ROM with respect to the intact state in flexion-extension (31.6% intact ROM, p < 0.001), lateral bending (32.5%, p < 0.001), and axial rotation (69.4%, p = 0.002). Compared with the stand-alone condition, addition of a lateral plate to the interbody cage did not significantly alter the ROM in flexion-extension (p = 0.904); however, it was significantly decreased in lateral bending and axial rotation (p < 0.001). The cage supplemented with a lateral plate was not statistically different from bilateral pedicle screws in lateral bending (p = 0.579). Supplemental fixation using a spinous process plate was not significantly different from bilateral pedicle

Clinical acceptance and accuracy assessment of spinal implants guided with SpineAssist surgical robot: retrospective study.

PubMed

Devito, Dennis P; Kaplan, Leon; Dietl, Rupert; Pfeiffer, Michael; Horne, Dale; Silberstein, Boris; Hardenbrook, Mitchell; Kiriyanthan, George; Barzilay, Yair; Bruskin, Alexander; Sackerer, Dieter; Alexandrovsky, Vitali; Stüer, Carsten; Burger, Ralf; Maeurer, Johannes; Donald, Gordon D; Gordon, Donald G; Schoenmayr, Robert; Friedlander, Alon; Knoller, Nachshon; Schmieder, Kirsten; Pechlivanis, Ioannis; Kim, In-Se; Meyer, Bernhard; Shoham, Moshe

2010-11-15

Retrospective, multicenter study of robotically-guided spinal implant insertions. Clinical acceptance of the implants was assessed by intraoperative radiograph, and when available, postoperative computed tomography (CT) scans were used to determine placement accuracy. To verify the clinical acceptance and accuracy of robotically-guided spinal implants and compare to those of unguided free-hand procedures. SpineAssist surgical robot has been used to guide implants and guide-wires to predefined locations in the spine. SpineAssist which, to the best of the authors' knowledge, is currently the sole robot providing surgical assistance in positioning tools in the spine, guided over 840 cases in 14 hospitals, between June 2005 and June 2009. Clinical acceptance of 3271 pedicle screws and guide-wires inserted in 635 reported cases was assessed by intraoperative fluoroscopy, where placement accuracy of 646 pedicle screws inserted in 139 patients was measured using postoperative CT scans. Screw placements were found to be clinically acceptable in 98% of the cases when intraoperatively assessed by fluoroscopic images. Measurements derived from postoperative CT scans demonstrated that 98.3% of the screws fell within the safe zone, where 89.3% were completely within the pedicle and 9% breached the pedicle by up to 2 mm. The remaining 1.4% of the screws breached between 2 and 4 mm, while only 2 screws (0.3%) deviated by more than 4 mm from the pedicle wall. Neurologic deficits were observed in 4 cases yet, following revisions, no permanent nerve damage was encountered, in contrast to the 0.6% to 5% of neurologic damage reported in the literature. SpineAssist offers enhanced performance in spinal surgery when compared to free-hand surgeries, by increasing placement accuracy and reducing neurologic risks. In addition, 49% of the cases reported herein used a percutaneous approach, highlighting the contribution of SpineAssist in procedures without anatomic landmarks.

Experiments on robot-assisted navigated drilling and milling of bones for pedicle screw placement.

PubMed

Ortmaier, T; Weiss, H; Döbele, S; Schreiber, U

2006-12-01

This article presents experimental results for robot-assisted navigated drilling and milling for pedicle screw placement. The preliminary study was carried out in order to gain first insights into positioning accuracies and machining forces during hands-on robotic spine surgery. Additionally, the results formed the basis for the development of a new robot for surgery. A simplified anatomical model is used to derive the accuracy requirements. The experimental set-up consists of a navigation system and an impedance-controlled light-weight robot holding the surgical instrument. The navigation system is used to position the surgical instrument and to compensate for pose errors during machining. Holes are drilled in artificial bone and bovine spine. A quantitative comparison of the drill-hole diameters was achieved using a computer. The interaction forces and pose errors are discussed with respect to the chosen machining technology and control parameters. Within the technological boundaries of the experimental set-up, it is shown that the accuracy requirements can be met and that milling is superior to drilling. It is expected that robot assisted navigated surgery helps to improve the reliability of surgical procedures. Further experiments are necessary to take the whole workflow into account. Copyright 2006 John Wiley & Sons, Ltd.

[Comparison of screw' inserting angle through the 11th and 12th rib anterior approaches for L1 burst fracture].

PubMed

Ma, Li-Tai; Liu, Hao; Li, Tao; Song, Yue-Ming; Pei, Fu-Xing; Liu, Li-Min; Gong, Quan; Zeng, Jian-Cheng; Feng, Gan-Jun; Zhou, Zhong-Jie

2012-12-01

To compare screw's inserting angle through the 11th and 12th rib in treating L1 burst fracture, explore effects on inserting screw and postoperative angle. From October 2007 to October 2010, 108 patients with L1 brust fracture treated through anterior approach were analyzed,including 68 males and 40 females, aged from 21 to 64 years (mean 38.22 years). All patients were divided into the 11th (A, 51 cases) and 12th (B, 57 cases) approach. The data of operation time,blood loss, duration of incision pain, JOA score, Oswestry score, VAS score, quality of life (SF-36), recovery of nervous function, coronal Cobb angle, included angle between screw and plate were observed. All patients were followed up for 9 to 37 months, mean 23 months. The operation time, blood loss, duration of incision pain, in group A were lower than group B (P<0.05), JOA score, Oswestry score, VAS score, SF-36, recovery of nervous function had no significant differences (P>0.05). There were no differences in Cobb angle before operation, but had significance after operation (P=0.000). There were statistically significance between two group in angle between screw and plate (P=0.000, P=0.003). The 11th rib approach for the treatment of L1 burst fracture has less effects on screw, less trauma and less angle between screw and plate.

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

Biomechanical stability of transverse connectors in the setting of a thoracic pedicle subtraction osteotomy.

PubMed

Lehman, Ronald A; Kang, Daniel G; Wagner, Scott C; Paik, Haines; Cardoso, Mario J; Bernstock, Joshua D; Dmitriev, Anton E

2015-07-01

Transverse connectors (TCs) are often used to improve the rigidity of posterior spinal instrumentation as previous investigations have suggested that TCs enhance torsional rigidity in long-segment thoracic constructs. Posterior osteotomies, such as pedicle subtraction osteotomy (PSO), are used in severe thoracic deformities and provide a significant amount of correction; as a consequence, however, PSOs also induce three-column spinal instability. In theory, augmentation of longitudinal constructs with TC after a thoracic PSO may provide additional rigidity, but the concept has not been previously evaluated. To evaluate the biomechanical contribution of TC to the rigidity of a long-segment pedicle screw-rod construct after a thoracic PSO. An in vitro fresh-frozen human cadaveric biomechanical analysis. Seven human cadaveric thoracic spines were prepared and instrumented from T4-T10 with bilateral pedicle screws/rods and a PSO was performed at T7. Intact range of motion (ROM) testing was performed with nondestructive loading and analyzed by loading modality (axial rotation [AR], flexion/extension [FE], and lateral bending [LB]). Range of motion analysis was performed in the unaugmented construct, the construct augmented with one TC, and the construct augmented with two TCs. After PSO and an unaugmented longitudinal pedicle screw-rod construct, T4-T10 (overall construct) and T6-T8 (PSO site) ROMs were significantly reduced in all planes of motion compared with intact condition (AR: 11.8° vs. 31.7°; FE: 2.4° vs. 12.3°; 3.4° vs. 17.9°, respectively, p<.05). Augmentation of longitudinal construct with either one or two TCs did not significantly increase construct rigidity in FE or LB compared with the unaugmented construct (p>.05). In contrast, during AR, global ROM was significantly reduced by 43% and 48% at T6-T8 (1.7° and 1.2° vs. 2.38°, respectively) after addition of one and two TCs (p<.05), respectively. One TC did not significantly reduce torsional ROM

The pedicled masseter muscle transfer for smile reconstruction in facial paralysis: repositioning the origin and insertion.

PubMed

Matic, Damir B; Yoo, John

2012-08-01

The pedicled masseter muscle transfer (PMMT) is introduced as a new reconstructive option for dynamic smile restoration in patients with facial paralysis. The masseter muscle is detached from both its origin and insertion and transferred to a new position to imitate the function of the native zygomaticus major muscle. Part one of this study consisted of cadaveric dissections of 4 heads (eight sides) in order to determine whether the masseter muscle could be (a) pedicled solely by its dominant neurovascular bundle and (b) repositioned directly over the native zygomaticus major. The second part of the study consisted of clinical assessments in three patients in order to confirm the applicability of this muscle transfer. Commissure excursion and vector of contraction following PMMT were compared to the non-paralyzed side. In all eight sides, the masseter muscles were successfully isolated on their pedicle and transposed on top of and in-line with the ipsilateral zygomaticus major. The mean length of the masseter and its angle from Frankfurt's horizontal line after transposition compared favorably to the native zygomaticus major muscle. In the clinical cases, the mean commissure movements of the paralyzed and normal sides were 7 mm and 12 mm respectively. The mean angles of commissural movement for the paralyzed and normal sides were 62° and 59° respectively. The PMMT can be used as a dynamic reconstruction for patients with permanent facial paralysis. As we gain experience with the PMMT, it may be possible to use it as a first-line option for patients not eligible for free micro-neurovascular reconstruction. Copyright © 2012 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Temporary Iliac Fixation to Salvage an Acute L4 Chance Fracture: Following Pedicle Screw Fixation for Adolescent Idiopathic Scoliosis.

PubMed

Kato, So; Lewis, Stephen J

2017-03-01

A case report. The aim of this study was to describe a technique of temporary distal fixation to the ilium to salvage an acute L4 fracture following a T3-L4 kyphoscoliosis correction. Pedicle fracture is a possible complication in pedicle screw fixation for scoliosis, which may lead to postoperative instability, resulting in loss of fixation and pseudoarthrosis. This report highlights the salvage treatment of a chance fracture that occurred in the lower instrumented vertebra following deformity correction for adolescent idiopathic scoliosis (AIS) without sacrificing further distal motion segments. A retrospective chart and radiograph review of a 13-year-old female who underwent surgical treatment for correction of AIS was performed. Following a T3-L4 correction with apical posterior column releases, an L4 Chance fracture with loss of distal fixation occurred on post-op day 3. Following an unsuccessful salvage with an infralaminar hook, a second revision was performed replacing the hook and adding bilateral temporary fixation to the ilium connected to the distal ends of the main rods through side-to-side connectors. The temporary fixation was removed 6 months later with successful healing of the fracture maintenance of the scoliosis correction at 2-year follow-up. Temporary extension of the construct to the ilium was successfully utilized in this case to salvage an acute L4 Chance fracture that occurred following a T3 to L4 construct for kyphoscoliosis. With this technique, successful reduction and healing of the fracture occurred with maintenance of the deformity correction without the need to fuse further distal segments. 4.

Locking design affects the jamming of screws in locking plates.

PubMed

Sandriesser, Sabrina; Rupp, Markus; Greinwald, Markus; Heiss, Christian; Augat, Peter; Alt, Volker

2018-06-01

The seizing of locking screws is a frequently encountered clinical problem during implant removal of locking compression plates (LCP) after completion of fracture healing. The aim of this study was to investigate the effect of two different locking mechanisms on the seizing of locking screws. Specifically, the removal torques before and after cyclic dynamic loading were assessed for screws inserted at the manufacturer-recommended torque or at an increased insertion torque. The seizing of 3.5-mm angular stable screws was assessed as a function of insertion torque for two different locking mechanisms (Thread & Conus and Thread Only). Locking screws (n=10 for each configuration) were inserted either according to the manufacturer-recommended torque or at an increased torque of 150% to simulate an over-insertion of the screw. Half of the screws were removed directly after insertion and the remaining half was removed after a dynamic load protocol of 100,000 cycles. The removal torques of locking screws exceeded the insertion torques for all tested conditions confirming the adequacy of the test setup in mimicking screw seizing in locked plating. Screw seizing was more pronounced for Thread Only design (+37%) compared to Thread & Conus design (+14%; P<0.0001). Cyclic loading of the locking construct consistently resulted in an increased seizing of the locking screws (P<0.0001). Clinical observations from patients treated with the Thread & Conus locking design confirm the biomechanical findings of reduction in seizing effect by using a Thread & Conus design. In conclusion, both over-tightening and cyclic loading are potential causes for screw seizing in locking plate implants. Both effects were found to be less pronounced in the Thread & Conus design as compared to the traditional Thread Only design. © 2018 Elsevier Ltd. All rights reserved.

[Exploratory study of 3D printing technique in the treatment of basilar invagination and atlantoaxial dislocation].

PubMed

Yin, Yiheng; Yu, Xinguang; Tong, Huaiyu; Xu, Tao; Wang, Peng; Qiao, Guangyu

2015-10-06

To investigate the clinical application value of the 3D printing technique in the treatment of basilar invagination and atlantoaxial dislocation. From January 2013 to September 2013, 10 patients with basilar invagination and atlantoaxial dislocation needing posterior fixation undertook 3D printing modes at the Department of Neurosurgery in PLA General Hospital. The 1:1 size models were established from skull base to C4 level with different colors between bone structures and vertebral arteries. The simulation of screw insertion was made to investigate the fixation plan and ideal entry point to avoid vertebral artery injury. After obtaining the individual screw insertion data in 3D printing modes, the according surgical operations were performed. The actual clinical results and virtual screw data in 3D printing mode were compared with each other. The 3D printing modes revealed that all the 10 patients had the dysplasia or occipitalized C1 posterior arch indicating C1 posterior arch screw implantation was not suitable. C1 lateral masses were chosen as the screws entry points. C2 screws were designed individually based on the 3D printing modes as follows: 3 patients with aberrant vertebral artery or narrow C2 pedicle less than 3.5 mm were not suitable for pedicle screw implantation. Among the 3 patients, 1 was fixed with C2 laminar screw, and 1 with C2-3 transarticular screw and 1 with C3 pedicle screw (also combined with congenital C2-3 vertebral fusion). Two patients with narrow C2 pedicle between 3.5 and 4mm were designed to choose pedicle screw fixation after 3D printing mode evaluation. One patient with C1 lateral mass vertically dislocated axis was planned with C1-2 transarticular screw fixation. All the other patients were planned with C2 pedicle screws. All the 10 patients had operation designed as the 3D printing modes schemes. The follow-up ranged from 12 to 18 months and all the patients recovered from the clinical symptoms and the bony fusion attained to

Time Demand and Radiation Dose in 3D-Fluoroscopy-based Navigation-assisted 3D-Fluoroscopy-controlled Pedicle Screw Instrumentations.

PubMed

Balling, Horst

2018-05-01

Prospective single-center cohort study to record additional time requirements and radiation dose in navigation-assisted O-arm-controlled pedicle screw (PS) instrumentations. The aim of this study was to evaluate amount of extra-time and radiation dose for navigation-assisted PS instrumentations of the thoracolumbosacral spine using O-arm 3D-real-time-navigation (O3DN) compared to non-navigated spinal procedures (NNSPs) with a single C-arm and postoperative computed tomography (CT) scan for controlling PS positions. 3D-navigation is reported to enhance PS insertion accuracy. But time-consuming navigational steps and considerable additional radiation doses seem to limit this modern technique's attraction. A detailed analysis of additional time demand and extra-radiation dose in 3D-navigated spine surgery is not provided in literature, yet. From February 2011 through July 2015, 306 consecutive posterior instrumentations were performed in vertebral levels T10-S1 using O3DN for PS insertion. The duration of procedure-specific navigational steps of the overall collective (I) and the last cohort of 50 consecutive O3DN-surgeries (II) was compared to the average duration of analogous surgical steps in 100 consecutive NNSP using a single C-arm. 3D-radiation dose (dose-length-product, DLP) of navigational and postinstrumentation O-arm scans in group I and II was compared to the average DLP of 100 diagnostic lumbar CT scans. The average presurgical time from patient positioning on the operating table to skin incision was 46.2 ± 10.1 minutes (O3DN, I) and 40.6 ± 9.8 minutes (O3DN, II) versus 30.6 ± 8.3 minutes (NNSP) (P < 0.001, each). Intraoperative interruptions for scanning and data processing took 3.0 ± 0.6 minutes. DLPs averaged 865.1 ± 360.8 mGycm (O3DN, I) and 562.1 ± 352.6 mGycm (O3DN, II) compared to 575.5 ± 316.5 mGycm in diagnostic lumbar CT scans (P < 0.001 (I), P ≈ 0.81 [II]). After procedural experience

Intramedullary nails with two lag screws.

PubMed

Brown, C J; Wang, C J; Yettram, A L; Procter, P

2004-06-01

To investigate the structural integrity of intramedullary nails with two lag screws, and to give guidance to orthopaedic surgeons in the choice of appropriate devices. Alternative designs of the construct are considered, and the use of a slotted upper lag screw insertion hole is analysed. Intramedullary fixation devices with a single lag screw have been known to fail at the lag screw insertion hole. Using two lag screws is considered. It has also been proposed to use a slot in the nail for the upper lag screw to prevent the upper lag screw from sticking. Bending and torsion load cases are analysed using finite element method. Consideration of both load conditions is essential. The results present the overall stiffness of the assembly, the load sharing between lag screws, and the possibility for cut-out to occur. While the slot for the upper lag screw might be advantageous with regard to the stresses in the lag screws, it could be detrimental for cut-out occurring adjacent to the lag screws. Comparative analyses demonstrate that two lag screws may be advantageous in patients whose cancellous bone quality is good and who impose large loads on the lag screw/nail interface. However, the use of two screws might pre-dispose to failure by cut-out of the lag screws. The addition of a slotted hole for the upper lag screw appears to do nothing significant to reduce the risk of such a failure. Copyright 2004 Elsevier Ltd.

The effect of different screw-rod design on the anti-rotational torque: a biomechanical comparison of three conventional screw-rod constructs.

PubMed

Huang, Zifang; Wang, Chongwen; Fan, Hengwei; Sui, Wenyuan; Li, Xueshi; Wang, Qifei; Yang, Junlin

2017-07-28

Screw-rod constructs have been widely used to correct spinal deformities, but the effects of different screw-rod systems on anti-rotational torque have not been determined. This study aimed to analyze the biomechanical effect of different rod-screw constructs on anti-rotational torque. Three conventional spinal screw-rod systems (Legacy, RF-F-10 and USSII) were used to test the anti-rotational torque in the material test machine. ANOVA was performed to evaluate the anti-rotational capacity of different pedicle screws-rod constructs. The anti-rotational torque of Legacy group, RF-F-10 group and USSII group were 12.3 ± 1.9 Nm, 6.8 ± 0.4 Nm, and 3.9 ± 0.8 Nm, with a P value lower than 0.05. This results indicated that the Legacy screws-rod construct could provide a highest anti-rotation capacity, which is 68% and 210% greater than RF-F-10 screw-rod construct and USSII screw-rod respectively. The anti-rotational torque may be mainly affected by screw cap and groove design. Our result showed the anti-rotational torque are: Legacy system > RF-F-10 system > USSII system, suggesting that appropriate rod-screw constructs selection in surgery may be vital for anti-rotational torque improvement and preventing derotation correction loss.

[Clinical application of three-dimensional O-arm navigation system in treating patients with dystrophic scoliosis secondary to neurofibromatosis type Ⅰ].

PubMed

Liu, Z; Qiu, Y; Li, Y; Zhao, Z H; Wang, B; Zhu, F; Yu, Y; Sun, X; Zhu, Z Z

2017-03-01

Objective: To investigate the clinical outcomes and the accuracy of O-arm-navigation system assisted pedicle screw insertion in dystrophic scoliosis secondary to neurofibromatosis type Ⅰ(NF-1). Methods: A retrospective study was conducted in 41 patients with dystrophic NF-1-associated thoracic scoliosis who were surgically treated at Department of Orthopaedics, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School between June 2012 and October 2014 with more than 18 months follow-up. The patients were then divided into two groups: 18 patients were under the assistance of O-arm-navigation-based pedicle screw insertion (O-arm group) and the remaining 23 patients' pedicle screws insertion were conducted by free-hand (free-hand group). The X-ray and CT were analyzed to investigate the correction rate and safety of pedicle insertion. t -test was used to analyze measurement data and χ(2) test was used to analyze accuracy of screw insertion between the two groups. Results: The mean coronal Cobb angle was 63.2°±8.7° in the O-arm group and 66.9°±7.4° in the free-hand group ( P >0.05), which was then corrected into 23.1°±6.8° and 30.2°±7.6°( t =2.231, P =0.031) after surgery respectively.Operation time was (265.0±70.3)minutes and estimated blood loss was (1 024±465)ml in the O-arm group. Operation time and estimated blood loss was (243.0±49.6)minutes and (1 228±521)ml respectively in the free-hand group, which had no significant difference between the two groups. However, the implant density was higher in the O-arm group than that in the free-hand group ((64.1±10.8)% vs .(44.3±15.3)%)( t =4.652, P =0.000). The O-arm group comprised 122 screws, of which 72.9% were excellent, 22.1% were good and 4.9% were bad. The free-hand group comprised 136 screws and 48.5% of them were excellent, 33.8% were good and 17.6% were bad.Accuracy of pedicle screw insertion was higher in the O-arm group than that in the free-hand group(χ(2

Radiographic predictors of symptomatic screw removal after retrograde femoral nail insertion.

PubMed

Hamaker, Max; O'Hara, Nathan N; Eglseder, W Andrew; Sciadini, Marcus F; Nascone, Jason W; O'Toole, Robert V

2017-03-01

Removal of symptomatic implants is a common procedure performed by orthopaedic trauma surgeons. No guidance is available regarding which factors contribute to the likelihood of an implant becoming symptomatic. Our objective was to determine whether radiographic parameters associated with distal interlocks in retrograde femoral nails are associated with the rate of symptomatic screw removal. We conducted a retrospective review at a Level I trauma center. Study patients (n=442) had femoral fractures treated with retrograde intramedullary nails from 2007 to 2014 and at least 1year of follow-up. The main outcome measurement was symptomatic distal screw removal as predicted by radiographic parameters. Symptomatic screw removal occurred in 12% of the patients. Increased distance between the most distal screw and the articular surface of the femur significantly reduced likelihood of symptomatic screw removal. A cutoff of 40mm from the articular block was predictive of removal (≥40mm, 0% removal; <40mm, 18% removal, p<0.0001). In patients with distal screws placed within 40mm of the articular surface of the femur, a ratio of screw length to distance between medial and lateral femoral cortices that was ≥1 was a strong predictor of symptomatic screw removal (area under Receiver Operating Characteristic curve, 0.75; p<0.0001). More distal screws and screws that radiographically extend to or beyond the medial cortex are more likely to cause pain and require removal in femoral fractures treated with retrograde intramedullary nails. We identified a specific distance from the joint (<40mm) and a ratio of screw length to bone width (≥1) that significantly increased the likelihood of symptomatic screw removal. Clinicians can use these data to inform patients of the likely risk of implant removal and perhaps to better guide placement and length of screws when the clinical scenario allows some flexibility in location and length of screws. Copyright © 2017 Elsevier Ltd. All

Evaluation of surgical strategy of conventional vs. percutaneous robot-assisted spinal trans-pedicular instrumentation in spondylodiscitis.

PubMed

Keric, Naureen; Eum, David J; Afghanyar, Feroz; Rachwal-Czyzewicz, Izabela; Renovanz, Mirjam; Conrad, Jens; Wesp, Dominik M A; Kantelhardt, Sven R; Giese, Alf

2017-03-01

Robot-assisted percutaneous insertion of pedicle screws is a recent technique demonstrating high accuracy. The optimal treatment for spondylodiscitis is still a matter of debate. We performed a retrospective cohort study on surgical patients treated with pedicle screw/rod placement alone without the application of intervertebral cages. In this collective, we compare conventional open to a further minimalized percutaneous robot-assisted spinal instrumentation, avoiding a direct contact of implants and infectious focus. 90 records and CT scans of patients treated by dorsal transpedicular instrumentation of the infected segments with and without decompression and antibiotic therapy were analysed for clinical and radiological outcome parameters. 24 patients were treated by free-hand fluoroscopy-guided surgery (121 screws), and 66 patients were treated by percutaneous robot-assisted spinal instrumentation (341 screws). Accurate screw placement was confirmed in 90 % of robot-assisted and 73.5 % of free-hand placed screws. Implant revision due to misplacement was necessary in 4.95 % of the free-hand group compared to 0.58 % in the robot-assisted group. The average intraoperative X-ray exposure per case was 0.94 ± 1.04 min in the free-hand group vs. 0.4 ± 0.16 min in the percutaneous group (p = 0.000). Intraoperative adverse events were observed in 12.5 % of free-hand placed pedicle screws and 6.1 % of robot robot-assisted screws. The mean postoperative hospital stay in the free-hand group was 18.1 ± 12.9 days, and in percutaneous group, 13.8 ± 5.6 days (p = 0.012). This study demonstrates that the robot-guided insertion of pedicle screws is a safe and effective procedure in lumbar and thoracic spondylodiscitis with higher accuracy of implant placement, lower radiation dose, and decreased complication rates. Percutaneous spinal dorsal instrumentation seems to be sufficient to treat lumbar and thoracic spondylodiscitis.

Does maximum torque mean optimal pullout strength of screws?

PubMed

Tankard, Sara E; Mears, Simon C; Marsland, Daniel; Langdale, Evan R; Belkoff, Stephen M

2013-04-01

To determine the relationship between insertion torque and pullout strength of 3.5-mm-diameter cortical screws in cadaveric humeri with different bone mineral densities (BMDs). Five pairs of human humeri from each of 3 BMD groups (normal, osteopenic, and osteoporotic) were used. Holes were drilled in each humerus, and maximum insertion torque (T(max)) was measured by tightening a screw until stripping occurred. In the remaining holes, screws were tightened to 50%, 70%, or 90% of the T(max). A servohydraulic testing machine pulled each screw out at 1 mm/s while resulting force and axial displacement were recorded at 10 Hz. The authors checked for an effect of insertion torque (percent T(max)) on pullout strength using a general linearized and latent mixed model (Stata10), controlling for cortical thickness and BMD (T-score). Pullout strength for normal and osteoporotic bone was greatest for screws inserted to 50% T(max) and was significantly greater than that at T(max) but not significantly different from that at 70% or 90% T(max). For osteopenic bone, pullout strength was greatest at 70% peak torque, but it was not significantly different from the pullout strength at the 50% or 90% T(max) levels. Tightening screws beyond 50% T(max) does not increase pullout strength of the screw and may place bone at risk for damage that might result in loss of fixation. Even after adjusting for bone thickness and density, there is no clear relationship between pullout strength and screw torque.

The risks of aorta impingement from pedicle screw may increase due to aorta movement during posterior instrumentation in Lenke 5C curve: a computed tomography study.

PubMed

Chen, Ling; Xu, Leilei; Qiu, Yong; Qiao, Jun; Wang, Fei; Liu, Zhen; Shi, Benglong; Qian, Bang-ping; Zhu, Zezhang

2015-07-01

To investigate the aorta movement following correction surgery for patients with thoracolumbar/lumbar scoliosis and to determine the subsequent risk of the aorta impingement for pedicle screw (PS) misplacement. Thirty-six AIS patients with a main thoracolumbar or lumbar curve were included in this study. According to the direction of the main curve, the patients were divided into Group R and Group L, with Group R comprising 16 patients with a right-sided curve and Group L comprising 20 patients with a left-sided curve. All patients underwent CT scans of the lower thoracic and lumbar spine before and after surgery. To identify the relative positions of the aorta to vertebral body, several parameters were measured from the CT images of the middle transverse planes of vertebrae from T11 to L4, including aorta-vertebra angle (α), vertebral rotation angle (β), left safety distance (LSD) and right safety distance (RSD). The risk of the aorta impingement from T11 to L4 was calculated. An intragroup comparison regarding the position of the aorta relative to the vertebral body before and after correction surgery was performed accordingly. After surgery, the aorta moved toward the vertebral body among all levels in both groups. Compared with that in Group L, the aorta in Group R was significantly closer to the entry point at all levels, especially at T11. Before surgery, the aorta in Group R was at a high risk of impingement from left PS placement regardless of the diameters of the simulated screws. While in Group L, the risk of aorta impingement was mainly caused by the right placement of 45 mm PS. After surgery, both groups had an increased risk of aorta impingement from PS insertion, especially at T11. The risk of aorta impingement from PS placement was significantly higher in Group R than in Group L. The risk of aorta impingement increased as the aorta shifted leftward after correction surgery, especially in right-sided Lenke 5C curve. Thus, preoperative risk

What is the Difference in Morphologic Features of the Thoracic Pedicle Between Patients With Adolescent Idiopathic Scoliosis and Healthy Subjects? A CT-based Case-control Study.

PubMed

Gao, Bo; Gao, Wenjie; Chen, Chong; Wang, Qinghua; Lin, Shaochun; Xu, Caixia; Huang, Dongsheng; Su, Peiqiang

2017-11-01

Describing the morphologic features of the thoracic pedicle in patients with adolescent idiopathic scoliosis is necessary for placement of pedicle screws. Previous studies showed inadequate reliability owing to small sample size and heterogeneity of the patients surveyed. To use CT scans (1) to describe the morphologic features of 2718 thoracic pedicles from 60 female patients with Lenke Type 1 adolescent idiopathic scoliosis and 60 age-, sex-, and height-matched controls; and (2) to classify the pedicles in three types based on pedicle width and analyze the distribution of each type. A total of 2718 pedicles from 60 female patients with Lenke Type 1 adolescent idiopathic scoliosis and 60 matched female controls were analyzed via CT. All patients surveyed were diagnosed with adolescent idiopathic scoliosis, Lenke Type 1, at the First Affiliated Hospital of Sun Yat-sen University, and all underwent pedicle screw fixation between January 2008 and December 2013 with preoperative radiographs and CT images on file. We routinely obtained CT scans before these procedures; all patients who underwent surgery during that period had CT scans, and all were available for analysis here. Control subjects had CT scans for other clinical indications and had no abnormal findings of the spine. The control subjects were chosen to match patients in terms of age (15 ± 2.6 years versus 15 ± 2.6 years) and sex. Height of the two groups also was matched (154 ± 9 cm versus 155 ± 10 cm; mean difference, -1.06 cm; 95% CI, -1.24 to -0.81 cm; p < 0.001). Pedicle width and length were measured from T1 to T12. The thoracic spine was classified in four regions: apical vertebra in the structural curve (AV-SC), nonapical vertebra in the structural curve (NAV-SC), apical vertebra in the nonstructural curve (AV-NSC), and nonapical vertebra in the nonstructural curve (NAV-NSC). Pedicles were classified in three types: pedicle width less than 2 mm as Type I, 2 mm to 4 mm as Type II, and greater than

Pedicle screw fixation for isthmic spondylolisthesis: does posterior lumbar interbody fusion improve outcome over posterolateral fusion?

PubMed

La Rosa, Giovanni; Conti, Alfredo; Cacciola, Fabio; Cardali, Salvatore; La Torre, Domenico; Gambadauro, Nicola Maria; Tomasello, Francesco

2003-09-01

Posterolateral fusion involving instrumentation-assisted segmental fixation represents a valid procedure in the treatment of lumbar instability. In cases of anterior column failure, such as in isthmic spondylolisthesis, supplemental posterior lumbar interbody fusion (PLIF) may improve the fusion rate and endurance of the construct. Posterior lumbar interbody fusion is, however, a more demanding procedure and increases costs and risks of the intervention. The advantages of this technique must, therefore, be weighed against those of a simple posterior lumbar fusion. Thirty-five consecutive patients underwent pedicle screw fixation for isthmic spondylolisthesis. In 18 patients posterior lumbar fusion was performed, and in 17 patients PLIF was added. Clinical, economic, functional, and radiographic data were assessed to determine differences in clinical and functional results and biomechanical properties. At 2-year follow-up examination, the correction of subluxation, disc height, and foraminal area were maintained in the group in which a PLIF procedure was performed, but not in the posterolateral fusion-only group (p < 0.05). Nevertheless, no statistical intergroup differences were demonstrated in terms of neurological improvement (p = 1), economic (p = 0.43), or functional (p = 0.95) outcome, nor in terms of fusion rate (p = 0.49). The authors' findings support the view that an interbody fusion confers superior mechanical strength to the spinal construct; when posterolateral fusion is the sole intervention, progressive loss of the extreme correction can be expected. Such mechanical insufficiency, however, did not influence clinical outcome.

Effect of Real-Time Feedback on Screw Placement Into Synthetic Cancellous Bone.

PubMed

Gustafson, Peter A; Geeslin, Andrew G; Prior, David M; Chess, Joseph L

2016-08-01

The objective of this study is to evaluate whether real-time torque feedback may reduce the occurrence of stripping when inserting nonlocking screws through fracture plates into synthetic cancellous bone. Five attending orthopaedic surgeons and 5 senior level orthopaedic residents inserted 8 screws in each phase. In phase I, screws were inserted without feedback simulating conventional techniques. In phase II, screws were driven with visual torque feedback. In phase III, screws were again inserted with conventional techniques. Comparison of these 3 phases with respect to screw insertion torque, surgeon rank, and perception of stripping was used to establish the effects of feedback. Seventy-three of 239 screws resulted in stripping. During the first phase, no feedback was provided and the overall strip rate was 41.8%; this decreased to 15% with visual feedback (P < 0.001) and returned to 35% when repeated without feedback. With feedback, a lower average torque was applied over a narrower torque distribution. Residents stripped 40.8% of screws compared with 20.2% for attending surgeons. Surgeons were poor at perceiving whether they stripped. Prevention and identification of stripping is influenced by surgeon perception of tactile sensation. This is significantly improved with utilization of real-time visual feedback of a torque versus roll curve. This concept of real-time feedback seems beneficial toward performance in synthetic cancellous bone and may lead to improved fixation in cancellous bone in a surgical setting.

Biomechanical Evaluation of the CD HORIZON Spire Z Spinal System With Pedicle and Facet Fixation.

PubMed

Godzik, Jakub; Kalb, Samuel; Martinez-Del-Campo, Eduardo; Newcomb, Anna G U S; Singh, Vaneet; Walker, Corey T; Chang, Steve W; Kelly, Brian P; Crawford, Neil R

2016-08-01

Human cadaveric biomechanical study. The aim of this study was to evaluate the biomechanics of lumbar motion segments instrumented with the CD HORIZON Spire Z plate system (Spire Z), a posterior supplemental fixation spinous process plate, alone and with additional fixation systems. Plates and pedicle screw/rod and facet screw implants are adjuncts to fusion. The plate limits motion, improving segmental stability and the fusion microenvironment. However, the degree to which the plate contributes to overall stability when used alone or in conjunction with additional instrumentation has not been described. Standard nondestructive flexibility tests were performed in 7 L2-L5 human cadaveric spines. Spinal stability was determined as mean range of motion (ROM) in flexion/extension, lateral bending, and axial rotation. Paired comparisons were made between five conditions: (1) intact/control; (2) Spire Z; (3) Spire Z with unilateral pedicle screw/rod system (Spire Z+UPS); (4) Spire Z with unilateral facet screw system (Spire Z+UFS); and (5) Spire Z with bilateral facet screw system (Spire Z+BFS). Stiffness and ROM data were compared using one-way analysis of variance, followed by repeated-measures Holm-Šidák tests. Spire Z was most effective in limiting flexion (20% of normal) and extension (24% of normal), but less effective in reducing lateral bending and axial rotation. In lateral bending, Spire Z+BFS and Spire Z+UPS constructs were not significantly different and demonstrated greater ROM reduction compared with Spire Z+UFS and Spire Z (P < 0.001). Spire Z+BFS demonstrated greatest stiffness in axial rotation compared with Spire Z+UPS (P = 0.025), Spire Z+UFS (P = 0.001), and Spire Z (P < 0.001). Spire Z+UPS was not significantly different from Spire Z+UFS (P = 0.21), and superior to Spire Z (P = 0.013). The Spire Z spinous process plate provides excellent immediate fixation, particularly for flexion and extension. While the hybrid Spire Z

Influence of screw density on thoracic kyphosis restoration in hypokyphotic adolescent idiopathic scoliosis.

PubMed

Luo, Ming; Jiang, Honghui; Wang, Wengang; Li, Ning; Shen, Mingkui; Li, Peng; Xu, Genzhong; Xia, Lei

2017-12-13

Previous studies have reported that rod composition and diameter, as well as the correction technique are key factors associated with thoracic kyphosis (TK) restoration. However, few study has analyzed the correlation between screw density and TK restoration in hypokyphotic adolescent idiopathic scoliosis (AIS). Fifty-seven thoracic AIS patients with preoperative TK < 10° treated with all pedicle screw fixation with a minimum 2-year follow-up were recruited. Preoperative and postoperative radiographic measurements, and information of posterior instrumentation were reviewed. Pearson and Spearman correlation coefficient analysis were used to assess relationships between change in TK and number of variables. Then, the included patients were classified into two groups (Group 1: postoperative TK ≥ 20°; Group 2: postoperative TK < 20°) to evaluate the influence factors of TK restoration. The average preoperative TK was 4.75°, which was significantly restored to 17.30° (P < 0.001). Significant correlations were found between change in TK and flexibility of major thoracic curve (r = 0.357, P = 0.006), preoperative TK (r = -0.408, P = 0.002), and screw density of concave side (r = 0.306, P = 0.021), respectively. In the subgroup comparison, 17 patients (29.8%) maintain the postoperative TK ≥ 20°, increased flexibility of major thoracic curve (P < 0.001), screw number of concave side (P = 0. 029), and cobalt chromium rods (P = 0.041) were found in the group of postoperative TK ≥ 20°. TK restoration remains a challenge for AIS patients with hypokyphosis, especially for the poor flexibility ones. Except for thicker and cobalt chromium rods, screw density of concave side might be another positive predictor of restoring normal kyphosis, which provides a stronger corrective force on the sagittal plane with more pedicle screws.

Biomechanical Comparison of Inter-fragmentary Compression Pressures: Lag Screw versus Herbert Screw for Anterior Odontoid Screw Fixation.

PubMed

Park, Jin-Woo; Kim, Kyoung-Tae; Sung, Joo-Kyung; Park, Seong-Hyun; Seong, Ki-Woong; Cho, Dae-Chul

2017-09-01

The purpose of the present study was to compare inter-fragmentary compression pressures after fixation of a simulated type II odontoid fracture with the headless compression Herbert screw and a half threaded cannulated lag screw. We compared inter-fragmentary compression pressures between 40- and 45-mm long 4.5-mm Herbert screws (n=8 and n=9, respectively) and 40- and 45-mm long 4.0-mm cannulated lag screws (n=7 and n=10, respectively) after insertion into rigid polyurethane foam test blocks (Sawbones, Vashon, WA, USA). A washer load cell was placed between the two segments of test blocks to measure the compression force. Because the total length of each foam block was 42 mm, the 40-mm screws were embedded in the cancellous foam, while the 45-mm screws penetrated the denser cortical foam at the bottom. This enabled us to compare inter-fragmentary compression pressures as they are affected by the penetration of the apical dens tip by the screws. The mean compression pressures of the 40- and 45-mm long cannulated lag screws were 50.48±1.20 N and 53.88±1.02 N, respectively, which was not statistically significant (p=0.0551). The mean compression pressures of the 40-mm long Herbert screw was 52.82±2.17 N, and was not statistically significant compared with the 40-mm long cannulated lag screw (p=0.3679). However, 45-mm Herbert screw had significantly higher mean compression pressure (60.68±2.03 N) than both the 45-mm cannulated lag screw and the 40-mm Herbert screw (p=0.0049 and p=0.0246, respectively). Our results showed that inter-fragmentary compression pressures of the Herbert screw were significantly increased when the screw tip penetrated the opposite dens cortical foam. This can support the generally recommended surgical technique that, in order to facilitate maximal reduction of the fracture gap using anterior odontoid screws, it is essential to penetrate the apical dens tip with the screw.

Polyaxial Screws in Locked Plating of Tibial Pilon Fractures.

PubMed

Yenna, Zachary C; Bhadra, Arup K; Ojike, Nwakile I; Burden, Robert L; Voor, Michael J; Roberts, Craig S

2015-08-01

This study examined the axial and torsional stiffness of polyaxial locked plating techniques compared with fixed-angle locked plating techniques in a distal tibia pilon fracture model. The effect of using a polyaxial screw to cross the fracture site was examined to determine its ability to control relative fracture site motion. A laboratory experiment was performed to investigate the biomechanical stiffness of distal tibia fracture models repaired with 3.5-mm anterior polyaxial distal tibial plates and locking screws. Sawbones Fourth Generation Composite Tibia models (Pacific Research Laboratories, Inc, Vashon, Washington) were used to model an Orthopaedic Trauma Association 43-A1.3 distal tibia pilon fracture. The polyaxial plates were inserted with 2 central locking screws at a position perpendicular to the cortical surface of the tibia and tested for load as a function of axial displacement and torque as a function of angular displacement. The 2 screws were withdrawn and inserted at an angle 15° from perpendicular, allowing them to span the fracture and insert into the opposing fracture surface. Each tibia was tested again for axial and torsional stiffness. In medial and posterior loading, no statistically significant difference was found between tibiae plated with the polyaxial plate and the central screws placed in the neutral position compared with the central screws placed at a 15° position. In torsional loading, a statistically significant difference was noted, showing greater stiffness in tibiae plated with the polyaxial plate and the central screws placed at a 15° position compared with tibiae plated with the central screws placed at a 0° (or perpendicular) position. This study showed that variable angle constructs show similar stiffness properties between perpendicular and 15° angle insertions in axial loading. The 15° angle construct shows greater stiffness in torsional loading. Copyright 2015, SLACK Incorporated.

Peak insertion torque values of five mini-implant systems under different insertion loads.

PubMed

Quraishi, Erma; Sherriff, Martyn; Bister, Dirk

2014-06-01

To assess the effect of 1 and 3 kg insertion load on five makes of self-drilling mini-implants on peak insertion torque values to establish risk factors involved in the fracture of mini-implants. Two different loads were applied during insertion of 40 mini-implants from five different manufacturers (Dual Top(™) (1·6×8 mm), Infinitas(™) (1·5×9 mm), Ortho Easy(™) (1·7×8 mm), Spider Screw(™) (1·5×8 mm) and Vector TAS(™) (1·4×8 mm)) into acrylic blocks at 8 rev/min utilizing a Motorized Torque Measurement Stand. Peak insertion torque values for both loads were highest for Vector TAS followed by Ortho Easy and Dual Top and were nearly three times higher than Infinitas (original version) and Spider Screws(TM). The log-rank test showed statistically significant differences for both loads for Vector TAS, Ortho Easy and Spider Screws. Unlike other designs tested, both tapered mini-implant designs (Spider Screw and Infinitas) showed a tendency to buckle in the middle of the body but fractured at the tip. Non-tapered mini-implants fractured at significantly higher torque values compared to tapered designs under both loads. Increased pressure resulted in slightly higher maximum torque values at fracture for some of the mini-implant designs, although this is unlikely to be of clinical relevance. Tripling insertion pressure from 1 to 3 kg increased the risk of bending tapered mini-implants before fracture. © 2014 British Orthodontic Society.

C1 lateral mass screw-induced occipital neuralgia: a report of two cases.

PubMed

Conroy, Eimear; Laing, Alan; Kenneally, Rory; Poynton, A R

2010-03-01

C1-2 polyaxial screw-rod fixation is a relatively new technique. While recognizing the potential for inadvertent vertebral artery injury, there have been few reports in the literature outlining all the possible complications. Aim of this study is to review all cases of C1 lateral mass screws insertion with emphasis on the evaluation of potential structures at risk during the procedure. We retrospectively reviewed all patients in our unit who had C1 lateral mass screw insertion over a 2-year period. The C1 lateral mass screw was inserted as part of an atlantoaxial stabilization or incorporated into a modular occiput/subaxial construct. Outcome measures included clinical and radiological parameters. Clinical indicators included age, gender, neurologic status, surgical indication and the number of levels stabilized. Intraoperative complications including blood loss, vertebral artery injury or dural tears were recorded. Postoperative pain distribution and neurological deficit were recorded. Radiological indicators included postoperative plain radiographs to assess sagittal alignment and to check for screw malposition or construct failure. A total of 18 lateral mass screws were implanted in 9 patients. There were three male and six female patients who had C1 lateral mass screw insertion in this unit. Two patients had atlantoaxial stabilization for C2 fracture. There were four patients with rheumatoid arthritis whose C1 lateral mass screws were inserted as part of an occipitocervical or subaxial cervical stabilization. There was no vertebral artery injury, no cerebrospinal fluid leak and minimal blood loss in all patients. Three patients developed postoperative occipital neuralgia. This neuralgia was transient, in one of the patients having settled at 6-week follow-up. In the other two patients the neuralgia was unresolved at time of latest follow-up but was adequately controlled with appropriate pain management. Postoperatively no patient had radiographic evidence of

C1 lateral mass screw-induced occipital neuralgia: a report of two cases

PubMed Central

Laing, Alan; Kenneally, Rory; Poynton, A. R.

2009-01-01

C1–2 polyaxial screw-rod fixation is a relatively new technique. While recognizing the potential for inadvertent vertebral artery injury, there have been few reports in the literature outlining all the possible complications. Aim of this study is to review all cases of C1 lateral mass screws insertion with emphasis on the evaluation of potential structures at risk during the procedure. We retrospectively reviewed all patients in our unit who had C1 lateral mass screw insertion over a 2-year period. The C1 lateral mass screw was inserted as part of an atlantoaxial stabilization or incorporated into a modular occiput/subaxial construct. Outcome measures included clinical and radiological parameters. Clinical indicators included age, gender, neurologic status, surgical indication and the number of levels stabilized. Intraoperative complications including blood loss, vertebral artery injury or dural tears were recorded. Postoperative pain distribution and neurological deficit were recorded. Radiological indicators included postoperative plain radiographs to assess sagittal alignment and to check for screw malposition or construct failure. A total of 18 lateral mass screws were implanted in 9 patients. There were three male and six female patients who had C1 lateral mass screw insertion in this unit. Two patients had atlantoaxial stabilization for C2 fracture. There were four patients with rheumatoid arthritis whose C1 lateral mass screws were inserted as part of an occipitocervical or subaxial cervical stabilization. There was no vertebral artery injury, no cerebrospinal fluid leak and minimal blood loss in all patients. Three patients developed postoperative occipital neuralgia. This neuralgia was transient, in one of the patients having settled at 6-week follow-up. In the other two patients the neuralgia was unresolved at time of latest follow-up but was adequately controlled with appropriate pain management. Postoperatively no patient had radiographic evidence of

Transpedicular Curettage and Drainage of Infective Lumbar Spondylodiscitis: Technique and Clinical Results

PubMed Central

Lee, Byung Ho; Lee, Hwan-Mo; Kim, Tae-Hwan; Kim, Hak-Sun; Moon, Eun-Soo; Park, Jin-Oh; Chong, Hyun-Soo

2012-01-01

Background Infective spondylodiscitis usually occurs in patients of older age, immunocompromisation, co-morbidity, and individuals suffering from an overall poor general condition unable to undergo reconstructive anterior and posterior surgeries. Therefore, an alternative, less aggressive surgical method is needed for these select cases of infective spondylodiscitis. This retrospective clinical case series reports our novel surgical technique for the treatment of infective spondylodiscitis. Methods Between January 2005 and July 2011, among 48 patients who were diagnosed with pyogenic lumbar spondylodiscitis or tuberculosis lumbar spondylodiscitis, 10 patients (7 males and 3 females; 68 years and 48 to 78 years, respectively) underwent transpedicular curettage and drainage. The mean postoperative follow-up period was 29 months (range, 7 to 61 months). The pedicle screws were inserted to the adjacent healthy vertebrae in the usual manner. After insertion of pedicle screws, the drainage pedicle holes were made through pedicles of infected vertebra(e) in order to prevent possible seeding of infective emboli to the healthy vertebra, as the same instruments and utensils are used for both pedicle screws and the drainage holes. A minimum of 15,000 mL of sterilized normal saline was used for continuous irrigation through the pedicular pathways until the drained fluid looked clear. Results All patients' symptoms and inflammatory markers significantly improved clinically between postoperative 2 weeks and postoperative 3 months, and they were satisfied with their clinical results. Radiologically, all patients reached the spontaneous fusion between infected vertebrae and 3 patients had the screw pulled-out but they were clinically tolerable. Conclusions We suggest that our method of transpedicular curettage and drainage is a useful technique in regards to the treatment of infectious spondylodiscitic patients, who could not tolerate conventional combined anterior and posterior

Screw Placement Accuracy for Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery: A Study on 3-D Neuronavigation-Guided Surgery

PubMed Central

Torres, Jorge; James, Andrew R.; Alimi, Marjan; Tsiouris, Apostolos John; Geannette, Christian; Härtl, Roger

2012-01-01

Purpose The aim of this study was to assess the impact of 3-D navigation for pedicle screw placement accuracy in minimally invasive transverse lumbar interbody fusion (MIS-TLIF). Methods A retrospective review of 52 patients who had MIS-TLIF assisted with 3D navigation is presented. Clinical outcomes were assessed with the Oswestry Disability Index (ODI), Visual Analog Scales (VAS), and MacNab scores. Radiographic outcomes were assessed using X-rays and thin-slice computed tomography. Result The mean age was 56.5 years, and 172 screws were implanted with 16 pedicle breaches (91.0% accuracy rate). Radiographic fusion rate at a mean follow-up of 15.6 months was 87.23%. No revision surgeries were required. The mean improvement in the VAS back pain, VAS leg pain, and ODI at 11.3 months follow-up was 4.3, 4.5, and 26.8 points, respectively. At last follow-up the mean postoperative disc height gain was 4.92 mm and the mean postoperative disc angle gain was 2.79 degrees. At L5–S1 level, there was a significant correlation between a greater disc space height gain and a lower VAS leg score. Conclusion Our data support that application of 3-D navigation in MIS-TLIF is associated with a high level of accuracy in the pedicle screw placement. PMID:24353961

Effect of screw fixation on acetabular component alignment change in total hip arthroplasty.

PubMed

Fujishiro, Takaaki; Hayashi, Shinya; Kanzaki, Noriyuki; Hashimoto, Shingo; Shibanuma, Nao; Kurosaka, Masahiro

2014-06-01

The use of screws can enhance immediate cup fixation, but the influence of screw insertion on cup position has not previously been measured. The purpose of this study was to quantitatively evaluate the effect of intra-operative screw fixation on acetabular component alignment that has been inserted with the use of a navigation system. We used a navigation system to measure cup alignment at the time of press-fit and after screw fixation in 144 hips undergoing total hip arthroplasty. We also compared those findings with factors measured from postoperative radiographs. The mean intra-operative change of cup position was 1.78° for inclination and 1.81° for anteversion. The intra-operative change of anteversion correlated with the number of screws. The intra-operative change of inclination also correlated with medial hip centre. The insertion of screws can induce changes in cup alignment, especially when multiple screws are used or if a more medial hip centre is required for rigid acetabular fixation.

Power-Tool Adapter For T-Handle Screws

NASA Technical Reports Server (NTRS)

Deloach, Stephen R.

1992-01-01

Proposed adapter enables use of pneumatic drill, electric drill, electric screwdriver, or similar power tool to tighten or loosen T-handled screws. Notched tube with perpendicular rod welded to it inserted in chuck of tool. Notched end of tube slipped over screw handle.

Advantages of Direct Insertion of a Straight Probe Without a Guide Tube During Anterior Odontoid Screw Fixation of Odontoid Fractures.

PubMed

Park, Jin Hoon; Kang, Dong-Ho; Lee, Moon Kyu; Yoo, Byoungwoo; Jung, Sang Ku; Hwang, Soo-Hyun; Kim, Jeoung Hee; Oh, Sunkyu; Lee, Eun Jung; Jeon, Sang Ryong; Roh, Sung Woo; Rhim, Seung Chul

2016-05-01

A retrospective cohort study. The aim of this study was to compare the anterior odontoid screw fixation (AOSF) with a guide tube or with a straight probe. AOSF associates with several complications, including malpositioning, fixation loss, and screw breakage. Screw pull-out from the C2 body is the most common complication. All consecutive patients with type II or rostral shallow type III odontoid fractures who underwent AOSFs during the study period were enrolled retrospectively. The guide-tube AOSF method followed the standard published method except C3 body and C2-3 disc annulus rimming was omitted to prevent disc injury; instead, the guide tube was anchored at the anterior inferior C2 vertebra corner. After 2 screw pull-outs, the guide-tube cohort was analyzed to identify the cause of instrument failure. Thereafter, the straight-probe method was developed. A guide tube was not used. A small pilot hole was made on the most anterior side of the inferior endplate, followed by insertion of a 2.5 mm straight probe through the C2 body. Non-union and instrument failure rates and screw-direction angles of the guide-tube and straight-probe groups were recorded. The guide-tube group (n = 13) had 2 screw pull-outs and 1 non-union. The straight-probe group (n = 8) had no complications and significantly larger screw-direction angles than the guide-tube group (60.5 ± 4.63 vs. 54.8 ± 3.82 degrees; P = 0.047). Straight-probe AOSF yielded larger direction angles without injuring bone and disc. Complications were absent. The procedure was easier than guide-tube AOSF and assured sufficient engagement, even in horizontal fracture orientation cases. 3.

Preloads generated with repeated tightening in three types of screws used in dental implant assemblies.

PubMed

Byrne, Declan; Jacobs, Stuart; O'Connell, Brian; Houston, Frank; Claffey, Noel

2006-01-01

Abutment screw loosening, especially in the case of cemented single tooth restorations, is a cause of implant restoration failure. This study compared three screws (titanium alloy, gold alloy, and gold-coated) with similar geometry by recording the preload induced when torques of 10, 20, and 35 Ncm were used for fixation. Two abutment types were used-prefabricated preparable abutments and cast-on abutments. A custom-designed rig was used to measure preload in the abutment-screw-implant assembly with a strain gauge. Ten screws of each type were sequentially tightened to 10, 20, and 35 Ncm on ten of the two abutment types. The same screws were then loosened and re-tightened. This procedure was repeated. Thus, each screw was tightened on three occasions to the three insertion torques. A linear regression model was used to analyze the effects on preload values of screw type and abutment type for each of the three insertion torques. The results indicated that the gold-coated screw generated the highest preloads for all insertion torques and for each tightening episode. Further analysis focused on the effects of screw type and abutment type for each episode of tightening and for each fixation torque. The gold-coated screw, fixed to the prefabricated abutment, displayed higher preloads for the first tightening at 10, 20, and 35 Ncm. Conversely, the same screw fixed to the cast-on abutment showed higher values for the second and third tightening for all fixation torques. All screws showed decay in preload with the number of times tightened. Given the higher preloads generated using the gold-coated screw with both abutment types, it is more likely that this type of screw will maintain a secure joint when tightened for the second and third time. All screw types displayed some decay in preload with repeated tightening, irrespective of abutment type and insertion torque. The gold-coated screw showed markedly higher preloads for all insertion torques and for all instances of

Evaluation of torque maintenance of abutment and cylinder screws with Morse taper implants.

PubMed

Ferreira, Mayara Barbosa; Delben, Juliana Aparecida; Barão, Valentim Adelino Ricardo; Faverani, Leonardo Perez; Dos Santos, Paulo Henrique; Assunção, Wirley Gonçalves

2012-11-01

The screw loosening of implant-supported prostheses is a common mechanical failure and is related to several factors as insertion torque and preload. The aim of this study was to evaluate the torque maintenance of retention screws of tapered abutments and cylinders of Morse taper implants submitted to retightening and detorque measurements. Two groups were obtained (n = 12): group I-tapered abutment connected to the implant with titanium retention screw and group II-cylinder with metallic base connected to tapered abutment with titanium retention screw. The detorque values were measured by an analogic torque gauge after 3 minutes of torque insertion. The detorque was measured 10 times for each retention screw of groups I and II, totalizing 120 detorque measurements in each group. Data were submitted to ANOVA and Fisher exact test (P < 0.05). Both groups presented reduced detorque value (P < 0.05) in comparison to the insertion torque in all measurement periods. There was a statistically significant difference (P < 0.05) between the detorque values of the first measurement and the other measurement periods for the abutment screw. However, there was no statistically significant difference (P > 0.05) for the detorque values of all measurement periods for the cylinder screw. In conclusion, the abutment and cylinder screws exhibited torque loss after insertion, which indicates the need for retightening during function of the implant-supported prostheses.

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 inserted...

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 inserted...

Asymmetry of the Vertebral Body and Pedicles in the True Transverse Plane in Adolescent Idiopathic Scoliosis: A CT-Based Study.

PubMed

Brink, Rob C; Schlösser, Tom P C; Colo, Dino; Vincken, Koen L; van Stralen, Marijn; Hui, Steve C N; Chu, Winnie C W; Cheng, Jack C Y; Castelein, René M

2017-01-01

Cross-sectional. To quantify the asymmetry of the vertebral bodies and pedicles in the true transverse plane in adolescent idiopathic scoliosis (AIS) and to compare this with normal anatomy. There is an ongoing debate about the existence and magnitude of the vertebral body and pedicle asymmetry in AIS and whether this is an expression of a primary growth disturbance, or secondary to asymmetrical loading. Vertebral body asymmetry, defined as left-right overlap of the vertebral endplates (ie, 100%: perfect symmetry, 0%: complete asymmetry) was evaluated in the true transverse plane on CT scans of 77 AIS patients and 32 non-scoliotic controls. Additionally, the pedicle width, length, and angle and the length of the ideal screw trajectory were calculated. Scoliotic vertebrae were on average more asymmetric than controls (thoracic: AIS 96.0% vs. controls 96.4%; p = .005, lumbar: 95.8% vs. 97.2%; p < .001) and more pronounced around the thoracic apex (95.8%) than at the end vertebrae (96.3%; p = .031). In the thoracic apex; the concave pedicle was thinner (4.5 vs. 5.4 mm; p < .001) and longer (20.9 vs. 17.9 mm; p < .001), the length of the ideal screw trajectory was longer (43.0 vs. 37.3 mm; p < .001), and the transverse pedicle angle was greater (12.3° vs. 5.7°; p < .001) than the convex one. The axial rotation showed no clear correlation with the asymmetry. Even in non-scoliotic controls is a degree of vertebral body and pedicle asymmetry, but scoliotic vertebrae showed slightly more asymmetry, mostly around the thoracic apex. In contrast to the existing literature, there is no major asymmetry in the true transverse plane in AIS and no uniform relation between the axial rotation and vertebral asymmetry could be observed in these moderate to severe patients, suggesting that asymmetrical vertebral growth does not initiate rotation, but rather follows it as a secondary phenomenon. Level 4. Copyright © 2016 Scoliosis Research Society. Published by Elsevier Inc. All

Fracture Gap Reduction With Variable-Pitch Headless Screws.

PubMed

Roebke, Austin J; Roebke, Logan J; Goyal, Kanu S

2018-04-01

Fully threaded, variable-pitch, headless screws are used in many settings in surgery and have been extensively studied in this context, especially in regard to scaphoid fractures. However, it is not well understood how screw parameters such as diameter, length, and pitch variation, as well as technique parameters such as depth of drilling, affect gap closure. Acutrak 2 fully threaded variable-pitch headless screws of various diameters (Standard, Mini, and Micro) and lengths (16-28 mm) were inserted into polyurethane blocks of "normal" and "osteoporotic" bone model densities using a custom jig. Three drilling techniques (drill only through first block, 4 mm into second block, or completely through both blocks) were used. During screw insertion, fluoroscopic images were taken and later analyzed to measure gap reduction. The effect of backing the screw out after compression was evaluated. Drilling at least 4 mm past the fracture site reduces distal fragment push-off compared with drilling only through the proximal fragment. There were no significant differences in gap closure in the normal versus the osteoporotic model. The Micro screw had a smaller gap closure than both the Standard and the Mini screws. After block contact and compression with 2 subsequent full forward turns, backing the screw out by only 1 full turn resulted in gapping between the blocks. Intuitively, fully threaded headless variable-pitch screws can obtain compression between bone fragments only if the initial gap is less than the gap closed. Gap closure may be affected by drilling technique, screw size, and screw length. Fragment compression may be immediately lost if the screw is reversed. We describe characteristics of variable-pitch headless screws that may assist the surgeon in screw choice and method of use. Copyright © 2018 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

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.

[Three-dimensional computed tomography analysis and clinical application of sacroiliac screw placement].

PubMed

Yin, Y C; Zhang, R P; Li, S L; Hou, Z Y; Chen, W; Zhang, Y Z

2018-03-01

Objective: To evaluate the possibility of transverse sacroiliac screw placement in different segments of the sacrum. Methods: Data of 80 pelvic CT scans (slice thickness ≤1.0 mm) archived in CT department of the Third Hospital of Hebei Medical University from September 2016 to October 2017 were retrospectively collected. Mimics software was used to rebuild the pelvis three-dimensional model. According to whether the sacral 1(S(1)) segment could place the transverse sacroiliac screws or not, all the sacrums were divided into normal group ( n =55) and dysmorphic group ( n =25). Simulation the S(1), sacral 2(S(2)) transverse sacroiliac screw placement in 3-Matic software. Analysis whether there was any difference in maximum diameter and length of S(2) transverse sacroiliac screw between the normal group and the dysmorphic group. The pelvic CT data of the dysmorphic group were measured, and the optimal tilt angle and length of the oblique S(1) screw were obtained. The feasibility of transverse sacroiliac screw insertion in sacral 3(S(3)) segment was evaluated. t -test, rank sum test, and χ(2) test was used to analyze data, respectively. Results: In the dysmorphic group, the largest diameter of the S(1) transverse screw was (4.9±1.6)mm, and the normal group was (13.6±3.6)mm ( t =-15.07, P =0.00). In the dysmorphic group, the largest diameter of S(2) transverse screw was (13.8±3.0)mm, and was (12.4±2.2)mm in the normal group( t =2.11, P =0.04). There was no significant difference in the length of S(2) transverse sacroiliac screw between the two groups ( t =0.47, P =0.64). In the dysmorphic group, the anterior vertebral height of S(1) was (23.1±4.0)mm, which was significantly higher than that of the normal group ((14.1±4.2)mm)( t =9.01, P =0.00). The angle of S(1)S(2) in the dysmorphic group was 10.9°(3.8°, 17.6°), which was significantly larger than that of the normal group (2.0°(1.0°, 2.0°) ( Z =-4.03, P =0.00). In the dysmorphic group, the incline angle

Additive-manufactured patient-specific titanium templates for thoracic pedicle screw placement: novel design with reduced contact area.

PubMed

Takemoto, Mitsuru; Fujibayashi, Shunsuke; Ota, Eigo; Otsuki, Bungo; Kimura, Hiroaki; Sakamoto, Takeshi; Kawai, Toshiyuki; Futami, Tohru; Sasaki, Kiyoyuki; Matsushita, Tomiharu; Nakamura, Takashi; Neo, Masashi; Matsuda, Shuich

2016-06-01

Image-based navigational patient-specific templates (PSTs) for pedicle screw (PS) placement have been described. With recent advances in three-dimensional computer-aided designs and additive manufacturing technology, various PST designs have been reported, although the template designs were not optimized. We have developed a novel PST design that reduces the contact area without sacrificing stability. It avoids susceptibility to intervening soft tissue, template geometric inaccuracy, and difficulty during template fitting. Fourteen candidate locations on the posterior aspect of the vertebra were evaluated. Among them, locations that had high reproducibility on computed tomography (CT) images and facilitated accurate PS placement were selected for the final PST design. An additive manufacturing machine (EOSINT M270) fabricated the PSTs using commercially pure titanium powder. For the clinical study, 36 scoliosis patients and 4 patients with ossification of the posterior longitudinal ligament (OPLL) were treated with thoracic PSs using our newly developed PSTs. We intraoperatively and postoperatively evaluated the accuracy of the PS hole created by the PST. Based on the segmentation reproducibility and stability analyses, we selected seven small, round contact points for our PST: bilateral superior and inferior points on the transverse process base, bilateral inferior points on the laminar, and a superior point on the spinous process. Clinically, the success rates of PS placement using this PST design were 98.6 % (414/420) for scoliosis patients and 100 % (46/46) for OPLL patients. This study provides a useful design concept for the development and introduction of patient-specific navigational templates for placing PSs.

Influence of Screw Length and Bone Thickness on the Stability of Temporary Implants

PubMed Central

Fernandes, Daniel Jogaib; Elias, Carlos Nelson; Ruellas, Antônio Carlos de Oliveira

2015-01-01

The purpose of this work was to study the influence of screw length and bone thickness on the stability of temporary implants. A total of 96 self-drilling temporary screws with two different lengths were inserted into polyurethane blocks (n = 66), bovine femurs (n = 18) and rabbit tibia (n = 12) with different cortical thicknesses (1 to 8 mm). Screws insertion in polyurethane blocks was assisted by a universal testing machine, torque peaks were collected by a digital torquemeter and bone thickness was monitored by micro-CT. The results showed that the insertion torque was significantly increased with the thickness of cortical bone from polyurethane (p < 0.0001), bovine (p = 0.0035) and rabbit (p < 0.05) sources. Cancellous bone improved significantly the mechanical implant stability. Insertion torque and insertion strength was successfully moduled by equations, based on the cortical/cancellous bone behavior. Based on the results, insertion torque and bone strength can be estimate in order to prevent failure of the cortical layer during temporary screw placement. The stability provided by a cortical thickness of 2 or 1 mm coupled to cancellous bone was deemed sufficient for temporary implants stability. PMID:28793582

Tibial Lengthening: Extraarticular Calcaneotibial Screw to Prevent Ankle Equinus

PubMed Central

Belthur, Mohan V.; Paley, Dror; Jindal, Gaurav; Burghardt, Rolf D.; Specht, Stacy C.

2008-01-01

Between 2003 and 2006, we used an extraarticular, cannulated, fully threaded posterior calcaneotibial screw to prevent equinus contracture in 10 patients (four male and six female patients, 14 limbs) undergoing tibial lengthening with the intramedullary skeletal kinetic distractor. Diagnoses were fibular hemimelia (two), mesomelic dwarfism (two), posteromedial bow (one), hemihypertrophy (one), poliomyelitis (one), achondroplasia (one), posttraumatic limb-length discrepancy (one), and hypochondroplasia (one). Average age was 24.5 years (range, 15–54 years). The screw (length, typically 125 mm; diameter, 7 mm) was inserted with the ankle in 10° dorsiflexion. Gastrocnemius soleus recession was performed in two patients to achieve 10° dorsiflexion. Average lengthening was 4.9 cm (range, 3–7 cm). Screws were removed after a mean 3.3 months (range, 2–6 months). Preoperative ankle range of motion was regained within 6 months of screw removal. No neurovascular complications were encountered, and no patients experienced equinus contracture. We also conducted a cadaveric study in which one surgeon inserted screws in eight cadaveric legs under image intensifier control. The flexor hallucis longus muscle belly was the closest anatomic structure noted during dissection. The screw should be inserted obliquely from upper lateral edge of the calcaneus and aimed lateral in the tibia to avoid the flexor hallucis longus muscle. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18800215

Comparison of CD HORIZON SPIRE spinous process plate stabilization and pedicle screw fixation after anterior lumbar interbody fusion. Invited submission from the Joint Section Meeting On Disorders of the Spine and Peripheral Nerves, March 2005.

PubMed

Wang, Jeremy C; Haid, Regis W; Miller, Jay S; Robinson, James C

2006-02-01

The authors present the early clinical results obtained in patients who underwent SPIRE spinous process plate fixation following anterior lumbar interbody fusion (ALIF). Between May 2003 and January 2005, 32 patients underwent titanium cage and bone morphogenetic protein-augmented ALIF and subsequent SPIRE (21 cases) or bilateral pedicle screw (BPS; 11 cases) fixation. Pedicle screws were implanted using either the open approach (three cases) or using a tubular retractor (eight cases). Patients' charts were reviewed for operative time, estimated blood loss (EBL), hospital length of stay (LOS), and evidence of pseudarthrosis or hardware failure. In SPIRE plate-treated patients, the median EBL (75 ml) was lower than in BPS-treated patients (open BPS [150 ml]; tubular BPS [125 ml]). The median operative time in SPIRE plate-treated patients was also shorter (164 minutes compared with 239 and 250 minutes in the open and tubular BPS, respectively). The median LOS was 3 days for both the SPIRE and tubular BPS groups, but 4 days in the open BPS group. There were no instances of major surgery-induced complication, pseudarthrosis, or hardware failure during mean follow-up periods of 5.5, 7.2, and 4.9 months in the SPIRE, open PS, and tubular BPS groups, respectively. The SPIRE plate is easy to implant and is associated with minimal operative risk. Compared with BPS/rod constructs, SPIRE plate fixation leads to less EBL and shorter operative time, without an increase in the rate of pseudarthrosis. Hospital LOS was also shorter in SPIRE plate-treated patients, which is consistent with the goals of minimal access spinal technologies.

Accuracy of image-guided surgical navigation using near infrared (NIR) optical tracking

NASA Astrophysics Data System (ADS)

Jakubovic, Raphael; Farooq, Hamza; Alarcon, Joseph; Yang, Victor X. D.

2015-03-01

Spinal surgery is particularly challenging for surgeons, requiring a high level of expertise and precision without being able to see beyond the surface of the bone. Accurate insertion of pedicle screws is critical considering perforation of the pedicle can result in profound clinical consequences including spinal cord, nerve root, arterial injury, neurological deficits, chronic pain, and/or failed back syndrome. Various navigation systems have been designed to guide pedicle screw fixation. Computed tomography (CT)-based image guided navigation systems increase the accuracy of screw placement allowing for 3- dimensional visualization of the spinal anatomy. Current localization techniques require extensive preparation and introduce spatial deviations. Use of near infrared (NIR) optical tracking allows for realtime navigation of the surgery by utilizing spectral domain multiplexing of light, greatly enhancing the surgeon's situation awareness in the operating room. While the incidence of pedicle screw perforation and complications have been significantly reduced with the introduction of modern navigational technologies, some error exists. Several parameters have been suggested including fiducial localization and registration error, target registration error, and angular deviation. However, many of these techniques quantify error using the pre-operative CT and an intra-operative screenshot without assessing the true screw trajectory. In this study we quantified in-vivo error by comparing the true screw trajectory to the intra-operative trajectory. Pre- and post- operative CT as well as intra-operative screenshots were obtained for a cohort of patients undergoing spinal surgery. We quantified entry point error and angular deviation in the axial and sagittal planes.

Bioactive ceramic coating of cancellous screws improves the osseointegration in the cancellous bone.

PubMed

Lee, Jae Hyup; Nam, Hwa; Ryu, Hyun-Seung; Seo, Jun-Hyuk; Chang, Bong-Soon; Lee, Choon-Ki

2011-05-01

A number of methods for coating implants with bioactive ceramics have been reported to improve osseointegration in bone, but the effects of bioactive ceramic coatings on the osseointegration of cancellous screws are not known. Accordingly, biomechanical and histomorphometric analyses of the bone-screw interface of uncoated cancellous screws and cancellous screws coated with four different bioactive ceramics were performed. After coating titanium alloy cancellous screws with calcium pyrophosphate (CPP), CaO-SiO(2)-B(2)O(3) glass-ceramics (CSG), apatite-wollastonite 1:3 glass-ceramics (W3G), and CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass-ceramics (BGS-7) using an enameling method, the coated and the uncoated screws were inserted into the proximal tibia and distal femur metaphysis of seven male mongrel dogs. The torque values of the screws were measured at the time of insertion and at removal after 8 weeks. The bone-screw contact ratio was analyzed by histomorphometry. There was no significant difference in the insertion torque between the uncoated and coated screws. The torque values of the CPP and BGS-7 groups measured at removal after 8 weeks were significantly higher than those of the uncoated group. Moreover, the values of the CPP and BGS-7 groups were significantly higher than the insertion torques. The fraction of bone-screw interface measured from the undecalcified histological slide showed that the CPP, W3G, and BGS-7 groups had significantly higher torque values in the cortical bone area than the uncoated group, and the CPP and BGS-7 groups had significantly higher torque values in the cancellous bone area than the uncoated group. In conclusion, a cancellous screw coated with CPP and BGS-7 ceramic bonds directly to cancellous bone to improve the bone-implant osseointegration. This may broaden the indications for cancellous screws by clarifying their contribution to improving osseointegration, even in the cancellous bone area.

Computation and visualization of uncertainty in surgical navigation.

PubMed

Simpson, Amber L; Ma, Burton; Vasarhelyi, Edward M; Borschneck, Dan P; Ellis, Randy E; James Stewart, A

2014-09-01

Surgical displays do not show uncertainty information with respect to the position and orientation of instruments. Data is presented as though it were perfect; surgeons unaware of this uncertainty could make critical navigational mistakes. The propagation of uncertainty to the tip of a surgical instrument is described and a novel uncertainty visualization method is proposed. An extensive study with surgeons has examined the effect of uncertainty visualization on surgical performance with pedicle screw insertion, a procedure highly sensitive to uncertain data. It is shown that surgical performance (time to insert screw, degree of breach of pedicle, and rotation error) is not impeded by the additional cognitive burden imposed by uncertainty visualization. Uncertainty can be computed in real time and visualized without adversely affecting surgical performance, and the best method of uncertainty visualization may depend upon the type of navigation display. Copyright © 2013 John Wiley & Sons, Ltd.

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.

Automated Bone Screw Tightening to Adaptive Levels of Stripping Torque.

PubMed

Reynolds, Karen J; Mohtar, Aaron A; Cleek, Tammy M; Ryan, Melissa K; Hearn, Trevor C

2017-06-01

To use relationships between tightening parameters, related to bone quality, to develop an automated system that determines and controls the level of screw tightening. An algorithm relating current at head contact (IHC) to current at construct failure (Imax) was developed. The algorithm was used to trigger cessation of screw insertion at a predefined tightening level, in real time, between head contact and maximum current. The ability of the device to stop at the predefined level was assessed. The mean (±SD) current at which screw insertion ceased was calculated to be [51.47 ± 9.75% × (Imax - IHC)] + IHC, with no premature bone failures. A smart screwdriver was developed that uses the current from the motor driving the screw to predict the current at which the screw will strip the bone threads. The device was implemented and was able to achieve motor shut-off and cease tightening at a predefined threshold, with no premature bone failures.

Esthetic abutment design for angulated screw channels: A technical report.

PubMed

Sakamoto, Satoshi; Ro, Munehiko; Al Ardah, Aladdin; Goodacre, Charles

2017-11-15

Angulated screw channel system abutments (ASCs) have recently been introduced to address the problem with visible screw access that may compromise esthetics. ASCs allow the screw access to be modified up to 25 degrees relative to the implant axis. However, a widened channel, which may cause thinning of the facial ceramic, is needed at the implant screw head to allow for proper engagement of the screwdriver. This technical report introduces a custom titanium insert design, the Satoshi Sakamoto (SS) abutment. The SS abutment consists of a custom titanium metal insert and zirconia coping in which the access hole is located in an esthetic position with an ASC system. The SS abutment results in a crown with more normal crown dimensions that also provides more space for the soft tissues. This SS abutment design allows clinicians to obtain screw-retained restorations with optimal esthetics and mechanical strength. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.