Transpedicular Screw Insertion Research Articles

Can Axis C be a navigation route – CT comparison study between actual and virtual C1 transpedicular screw insertion

BackgroundPrevious studies mainly reported perpendicular and medial inclination insertion methods for C1 transpedicular screw insertion (TSI). Our recent study showed the ideal C1 transpedicular screw trajectory (TST) can be achieved by medial inclination, perpendicular or even lateral inclination insertion, and Axis C can be a reliable trajectory. The purpose of this study is to confirm Axis C is an ideal C1 TST by comparing the cortical perforation differences between actual C1 TSI and virtual C1 transpedicular screw insertion along Axis C (Virtual C1 Axis C TSI). MethodsFirstly, the cortical perforations of the transverse foramen and vertebral canal caused by C1 TSIs in twelve randomly selected patients were evaluated based on their postoperative CT data. Secondly, Virtual C1 Axis C TSIs were performed based on same patients’ preoperative CT data. Thirdly, the cortical perforation differences between actual and virtual screws were compared. ResultsIn actual C1 TSI group, there were thirteen locations of cortical perforation in the axial plane, with five sides in transverse foramen and eight sides in vertebral canal, the cortical perforation rate was 54.2%; the degree of perforation was mild in twelve locations and medium in one location. In contrast, there was no cortical perforation in Virtual C1 Axis C TSI group. ConclusionsAxis C is an ideal trajectory for C1 TSI, it can be utilized as a navigation route for computer assisted surgery system.

Accuracy and Safety of Fluoroscopy-Assisted Transpedicular Screw Insertion in Thoracolumbar Spine Surgery: Evaluation of 122 Screws.

The objective of this study is to determine the accuracy and safety of trans-pedicular screws' insertion in the thoracolumbar spine using a fluoroscopy-assisted surgical technique. We retrospectively evaluated all patients who underwent a postoperative computed tomography scan to assess the location of the pedicular screws following thoracolumbar spinal surgery, at the Mohammed Vth Military Training Hospital-Rabat, from January 2020 to April 2022. We used Gertzbein's classification to grade pedicular cortex breaches. A screw penetration greater than 4 mm (grades D-E) was considered critical and one less than 4 mm was classified as noncritical (grades A-C). A total of 122 screws inserted in the T1 to L5 vertebrae were included from 25 patients. The average age was 46 years old. Pathologies included degenerative disorders (5 patients), tumors (8 patients), and trauma (12 patients). All screws were inserted using lateral and anteroposterior fluoroscopic guidance. A total of 11 transpedicular screws breaches were identified. The breaches incidence was significantly higher in thoracic pedicles (8 screws) than in lumbar pedicles (3 screws). Of these, three critical cases occurred in two patients and one of them required reintervention. The remaining eight exceedances were not critical and were closely monitored and followed up. Transpedicular screws fluoroscopy-assisted surgical fixation can be performed for the stabilization of the thoracolumbar spine with satisfactory safety and precision.

Efficacy and Safety of Goel-Harms Technique in Upper Cervical Spine Surgery: A Systematic Review and Meta-Analysis

The main purpose of this systematic review and meta-analysis was to estimate the incidence of implant-associated complications and fusion rates for the Goel-Harms technique (GHT) and to show potential factors affecting the complications and nonunion development. A systematic search of the PubMed database according to PRISMA guidance was performed. The main inclusion criteria comprised description of fusion rate and/or implant-associated complications rate. This systematic review included 86 articles focused on the results of surgery in 4208 patients. The rate of screw-related complications was as follows: 1) vertebral artery (VA) injury, 2.8%; 2) screw malposition in the direction of the VA, 5.8%; and 3) C2 nerve root irritation, 6.1%. The nonunion rate was 4.2%. Transpedicular screw insertion to the C1 and C2 vertebrae were the safest regarding VA injury and correlated with lower blood loss. For C1-C2 fusion, there was no statistical difference for the different bone graft localization. C2 nerve root irritation rate did not depend on screw insertion technique. The use of a freehand technique did not correlate with a high rate of screw-related complications. The Goel-Harms technique is a promising method of C1-C2 fusion, with a relatively low nonunion and VA injury rate. It can be performed safely without C-arm or navigation system assistance. Transpedicular screw insertion trajectories to the C1 and C2 vertebrae were safest regarding VA injury and blood loss volume. Further comparative studies of various C1-C2 stabilization methods with a high level of significance should be carried out to identify the optimal approach.

Morphometric analysis of Lumbar Pedicle in our population based on computed tomography

Background: The use of pedicle screw fixation for management of various spinal disorders has become popular worldwide in recent years. Pedicle screw fixations has implications in spinal fusion by transpedicular screw insertion to achieve stability in various spinal disorders such as, fractures, scoliosis, spondylosis thesis, tumours and iatrogenic or degenerative spinal instability. It is essential for the spine surgeon to have a comprehensive knowledge of the spinal morphometric dimensions since misplacement of the pedicle screw carries significant risk for the patient. It is challenging to perform pedicle screw fixation technically due to complex anatomy. Objective: To assess the lumbar pedicle morphometry in south Indian population based on CT scans. Materials and Methods: The present prospective observational study was carried out by the department of Orthopedics at JSS Medical College, Mysore from November 2018 to September 2020. A total of 100 patients who underwent Computed tomography of lumbar spine and Computed tomography abdomen and pelvis in JSS Hospital, Mysuru during the study period were included in the study. Results: The mean transverse pedicle Isthmus width was the least at L1 level (6.64mm) and highest at L s level (15.66mm). There was significant difference between male and female Vertebral Diameters.

Confirmation of accuracy/inaccuracy of lumbar pedicle screw placement using postoperative computed tomography.

Background: Transpedicular screws are extensively utilized in lumbar spine surgery. The placement of these screws is typically guided by anatomical landmarks and intraoperative fluoroscopy. Here, we utilized 2-week postoperative computed tomography (CT) studies to confirm the accuracy/inaccuracy of lumbar pedicle screw placement in 145 patients and correlated these findings with clinical outcomes.Methods: Over 6 months, we prospectively evaluated the location of 612 pedicle screws placed in 145 patients undergoing instrumented lumbar fusions addressing diverse pathology with instability. Routine anteroposterior and lateral plain radiographs were obtained 48 h after the surgery, while CT scans were obtained at 2 postoperative weeks (i.e., ideally these should have been performed intraoperatively or within 24–48 h of surgery).Results: Of the 612 screws, minor misplacement of screws (≤2 mm) was seen in 104 patients, moderate misplacement in 34 patients (2–4 mm), and severe misplacement in 7 patients (>4 mm). Notably, all the latter 7 (4.8% of the 145) patients required repeated operative intervention.Conclusion: Transpedicular screw insertion in the lumbar spine carries the risks of pedicle medial/lateral violation that is best confirmed on CT rather than X-rays/fluoroscopy alone. Here, we additional found 7 patients (4.8%) who with severe medial/lateral pedicle breach who warranting repeated operative intervention. In the future, CT studies should be performed intraoperatively or within 24–48 h of surgery to confirm the location of pedicle screws and rule in our out medial or lateral pedicle breaches.

Transpedicular fixation of the spine with two-level navigation templates for narrow pedicles

Objective. To assess the correctness of transpedicular screw insertion in thoracic and lumbar vertebrae using two-level navigation templates for narrow pedicles.Material and Methods. Two-level navigation templates were used in surgical treatment of four patients aged 14–17 years with scoliotic deformity and multiple pedicles of small width (less than 4.35 mm). In each patient, the least favorable zones were selected for implantation using navigation templates. The rest of planned pedicle screws were inserted using free-hand technique. All patients underwent CT scanning postoperatively. Screws inserted to pedicles less than 4.35 mm in width were classified as correctly placed if they did not extend beyond the medial cortical layer by more than 2 mm.Results. Out of 68 pedicles planned for screw placement, 42 were narrower than 4.35 mm. In the pedicles difficult for implantation, 29 screws were inserted using navigation templates and 13 by free-hand technique. Screws classified as correctly placed were 28 from those inserted with navigation templates and 9 from those implanted by free-hand technique. Difference in results of screw placement in narrow pedicles with navigation templates and by free-hand technique was statistically significant (exact Fisher test, p < 0.05).Conclusion. Transpedicular screw placement with two-level navigation templates in narrow pedicles is more correct than insertion by free hand technique.

Computed tomography comparison study of two Axis-based C1 transpedicular screw trajectory designs

BACKGROUND CONTEXTTo our knowledge, there is no comparison study of two different Axis-based C1 transpedicular screw trajectory (TST) designs. PURPOSETo compare two different Axis-based C1 TST designs. STUDY DESIGNThe computed tomography (CT) morphologic analysis of the two different C1 Axis-based TST designs. METHODSFirstly, the design of Axis C/M and related measurements were made on a work station by using neck computed tomography angiography (CTA) data of 62 patients. The central axes (Axis M and Axis C) of C1 TST were designed by multiplanar reconstruction (MPR) technique. Based on Axis M and Axis C, the following parameters were measured: (A, A’), distance between the insertion point (IP) and the midline. (B, B’), distance between IP and the inferior aspect of C1 posterior arch. (C, C’), distance between IP and the C1 anterior cortex of the lateral mass along Axis M/C. (D, D’), insertion angle (IA) based on Axis M/C. (E, E’), the narrowest width of the inner medullary cavity (IMC) along Axis M/C. RESULTThe C1 TST can be designed by MPR technique based on CT volume scan. The design of Axis C trajectory was easier to Axis M trajectory. A, A’ were 20.7±1.6mm and 20.6±1.9mm. Both B, B’ were 2.0±0.6mm. C, C’ were 27.2±2.1mm and 27.5±2.1mm. D, D’ were 9.9±5.0°and 10.4±7.7°. E, E’ were 5.0±1.3mm and 5.4±1.4mm. Among 62 patients (124 sides), Axis C can be achieved by medial inclination, perpendicular, lateral inclination method in 81.5%, 13.7%, 4.8% sides, respectively; Axis M can be achieved by medial inclination, perpendicular, lateral inclination method in 90.3%, 8.9%, 0.8% sides, respectively. CONCLUSIONAxis C can be a reliable trajectory for C1 transpedicular screw insertion as long as there is no displaced fracture in the C1 pedicle and lateral mass. Because of the individual differences, the ideal C1 TST can be achieved by medial inclination, perpendicular or even lateral inclination method, although its inclination direction is medial in the majority of patients.

The Accuracy and Safety for C2 Transpedicular Screw Placement by Freehand Using the Anatomical Visualization Technique Under Fluoroscopy

Background: The C2 transpedicular screw trajectory does not have an exact guideline for the screw placement because the anatomical variation in this region could results in injury to the vertebral artery during surgery. Objective: To assess the accuracy and safety for C2 transpedicular screw placement by freehand under lateral fluoroscopy with an anatomical landmark using the direct visualization technique. Materials and Methods: The present study was a retrospective data that reviewed 19 consecutive patients who underwent C2 transpedicular screw fixation by freehand placement with lateral fluoroscopic-guided and an anatomical landmark by direct visualization technique between March 2017 and February 2019 in Pathum Thani Hospital. The preoperative CT cervical spine was evaluated before the operation and postoperative CT angiogram images of the neck were taken in all patients after they were clinically stable to evaluate the vertebral artery and accuracy in the transpedicular screw placement. Results: An anatomical landmark by direct visualization technique is accurate and safe for C2 transpedicular screw placement. Conclusion: The C2 transpedicular screw insertion should be positioned using clear anatomical landmarks and determined by direct visualization to avoid vertebral artery injury during surgery. Keywords: C2 transpedicular screw, Vertebral artery injury, Anatomical landmark, The anatomical visualized technique

Optimization of Spondylosynthesis for Certain Thoracolumbar Burst Fractures.

Intermediate transpedicular fixation, i.e. additional insertion of transpedicular screws into the injured vertebrae, is an improvement to the most popular surgical intervention for spinal injuries, currently gaining widespread use in clinical practice. Unilateral insertion of transpedicular screws into the injured vertebrae allows combining the advantages of intermediate transpedicular fixation with the possibility to perform anterior column support without remounting the transpedicular system.The aim of the study was to use biomechanical computer modeling for evaluating the stability of intermediate transpedicular fixation components, which allow performing anterior column support if necessary.Materials and Methods.DICOM files obtained during CT scan of a patient with intermediate thoracolumbar spine injury and the ANSYS software were used. Stability of the transpedicular system and supportability of the complementary Mesh implant installed with unilateral intermediate transpedicular screws were evaluated using computer modeling based on the finite element method.Results.The values of stress and displacement fields for spine–hardware systems with various arrangements have been obtained. The maximum loads exceeding bone tissue strength (153–161 MPa) were registered for standard 4-screw system (190 MPa) when modeling the load equivalent for walking and falling from a standing position. The use of the proposed fixation system arrangement supplemented with intermediate screws allows obtaining loads in the spine–hardware system not exceeding these thresholds. Complementary eccentric Mesh implant enhances fixation stability of the transpedicular system with intermediate screws.Conclusion.The results show the high degree of mechanical stability of the proposed hardware arrangement and its potential efficacy for thoracolumbar transitional vertebra stabilization.

Prevalence of High-Riding Vertebral Artery: A Meta-Analysis of the Anatomical Variant Affecting Choice of Craniocervical Fusion Method and Its Outcome

A high-riding vertebral artery (HRVA) has been defined as a C2 isthmus height of ≤5 mm and/or internal height of ≤2 mm measured 3 mm lateral to the border of the spinal canal. Its reported prevalence has varied widely. If overlooked during the approach for craniocervical fusion, injury to the vertebral arteries can occur, affecting the outcome. The present meta-analysis aimed to provide the pooled prevalence of HRVAs. A comprehensive database search was conducted by 3 of us. Peer-reviewed studies that had followed the strict definition for HRVAs and had reported its prevalence were included. The risk of bias was assessed using the anatomical quality assessment tool. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed. The pooled prevalence was calculated using a random effects model. The data from 20 studies with 3126 subjects (7496 sides) were analyzed. The overall pooled prevalence of ≥1 HRVA was 25.3% (95% confidence interval [CI], 19.6%-31.5%). The prevalence in those without the most important confounding factor, rheumatoid arthritis (RA), was 20.9% (95% CI, 16.5%-25.8%). Patients with RA had a prevalence of 42.9% (95% CI, 23.8%-63.1%). The difference between the non-RA and RA groups was statistically significant (P < 0.001, test of homogeneity, χ2). No geographical differences were noted (P= 0.20, test of homogeneity, χ2). Among those with HRVA, unilateral HRVA was present in 70.3% (95% CI, 65.2%-75.2%) and bilateral in 29.7% (95% CI, 24.8%-34.8%). No left or right side predilection was found (left, 50.8%; 95% CI, 33.8%-67.6%; right, 49.2%; 95% CI, 32.4%-66.2%). Craniocervical fusion should be preceded by examination of the vertebral arteries at the level of C2 because the presence of HRVAs is common and might preclude the safe insertion of transarticular or transpedicular screws.

Currently Adopted Criteria for Pedicle Screw Diameter Selection.

Transpedicular screw insertion has become widely accepted for the correction of spinal deformity as well as degenerative and traumatic injury, but adoption of this technique has remained less widespread in the thoracic compared to the lumbar spine. This is thought to be associated with the relative technical difficulty of screw insertion into the narrower widths of the thoracic pedicles and the neurologic and mechanical risks associated with breach of the pedicle wall. The surgical decision making involves determining the appropriate sized screw for maximum fixation strength while simultaneously respecting the structural integrity of the vertebral pedicles to prevent a breach and provide better fixation. This paper presents a systematic review of criteria for thoracic pedicle screw diameter (SD) selection in order to orient inexperienced surgeons on the impact of this selection on pedicle breaching and fixation strength. We performed a systematic literature review focused on studies reporting SD selection in relation to pedicle dimensions, measures of fixation strength, and breach rate. Twenty-nine articles that measured fixation strength, breach rate, and/or provided SD in relation to pedicle width were selected for inclusion. A commonly accepted criteria for pedicle SD selection has not yet been proposed. Screw diameters approximately 80% of the pedicle width have been adopted, but this proportion is rarely reported in the midthoracic vertebrae for which smaller pedicles and inadequate hardware specificity result in higher breach rates. Depending upon the insertion technique adopted, greater specificity in diameter selection by vertebral level should be pursued in order to maximally target cortical bone purchase. Based on this review of the literature, we believe that proper selection of the SD for individual vertebral level directly affects the insertion technique and the potential breach.

Posterior Transpedicular Screw Fixation of Subaxial Vertebrae: Accuracy Rates and Safety of Mini-laminotomy Technique.

Background and Aim:Posterior cervical transpedicular screw fixation has the strongest resistance to pullout forces compared with other posterior fixation systems. Here, we present a case on the use of this technique combined with a mini-laminotomy technique, which serves as a guide for accurate insertion of posterior cervical transpedicular screws.Materials and Methods:We retrospectively analyzed data from 40 patients who underwent this procedure in our clinic between January 2014 and March 2017.Results:The study population comprised 27 males (67.5%) and 13 females (32.5%) aged 15–80 years (median, 51.5 years). Surgical indications included trauma (n = 18, 45%), degenerative disease (n = 19, 47.5%), spinal infection (n = 2, 5%), and basilar invagination due to systemic rheumatoid disease (n = 1, 2.5%). In the 18 trauma patients, 14 short-segment (1–2 levels) and 4 long-segment (≥3 levels) posterior cervical instrumentation and fusion procedures were performed. The mini-laminotomy technique was used in all patients to insert, direct, and achieve exact screw fixation in the pedicles. Pedicle perforations were classified as medial or lateral and were also graded. Among the 227 cervical pedicle fixations performed, 48 were at the C3 level, 49 at C4, 60 at C5, 50 at C6, and 20 at C7. Axial computed tomography scan measurements showed that 205 of 227 (90.3%, Grade 0 and 1) screws were accurately placed, whereas 22 (9.69%, Grade 2 and 3) were misplaced. However, no additional neurological injury due to misplacement was observed.Conclusion:As negligible complications were observed when performed by experienced surgeons, the mini-laminotomy technique can be safely used for posterior transpedicular screw fixation in the subaxial vertebrae for single-staged fusion.

Wednesday, September 26, 2018 1:00 PM – 2:00 PM Navigation and Intraoperative Monitoring: 48. Computer-assisted navigation in posterior lumbar fusion increases operative time and length of stay

BACKGROUND CONTEXT Computer-assisted navigation in lumbar spine surgery has been commercially available since 2000 and has been reported to reduce patient radiation exposure, transpedicular screw insertion errors, and decrease operative time. Adoption rates for navigation in posterior lumbar fusion are unknown, and it is important to determine the impact of navigation on patient outcomes and quality metrics in the thirty-day postoperative period. PURPOSE To determine the adoption rate of computer-assisted navigation and determine short-term complications associated with computer-assisted navigation in posterior lumbar fusion. STUDY DESIGN/SETTING Retrospective database study using the American College of Surgeons National Quality Improvement Program (ACS NSQIP) database from 2011 to 2015. PATIENT SAMPLE Patients undergoing elective posterior lumbar spinal fusion were identified in the ACS NSQIP database patients using CPT code 22612, 22633, or 22630. Cases with clean-contaminated, contaminated or dirty/infected wound class were excluded from analysis. OUTCOME MEASURES We identified cases using intraoperative computer-assisted navigation using secondary CPT code 61783. We compared operative time and length of hospital stay, as well as complications occurring within 30 days of posterior lumbar fusion. Complications were identified from available variables in ACS NSQIP database including superficial infection, deep infection, organ-space infection, wound dehiscence, sepsis, septic shock, pneumonia, urinary tract infection, pulmonary embolism, deep venous thrombosis, unplanned reintubation, renal insufficiency, acute renal failure, stroke, coma, peripheral nerve injury, cardiac arrest, myocardial infarction, reoperation within 30 days, unplanned readmission, and mortality. METHODS Patients were stratified based on documentation of intraoperative computer-assisted navigation (CAN) (CPT code 61783). Patient demographics and comorbidities were compared between CAN and non-navigated groups using chi-square and Student t test for categorical and continuous variables, respectively. Operative variables including resident involvement and number of vertebral segments fused were also assessed. Propensity score matching was used to reduce patient selection bias for comparison of thirty-day complication rates between the navigated and traditional lumbar spine fusion groups. A P value of RESULTS There were a total of 25,010 patients in the cohort, with 1,812 (7.2%) cases involving computer-assisted navigation. Navigation adoption rates increased from 3.4% in 2011 to a peak of 9.6% in 2014. Utilization in the most recent study year, 2015, was 7.2%. Short-term complications occurred in 1,973 cases (8.6%). After propensity score matching, operative time was increased 14 minutes in the navigated group (222.0 vs. 205.7 minutes, p CONCLUSIONS Computer-assisted navigation rates of adoption increased from 2011 to 2014, but appeared to plateau in 2015. Computer-assisted navigation is associated with increased operative time and longer hospital stay, but there are no differences in all-cause complications between navigated and non-navigated elective posterior spinal fusion. Thus, while computer assisted navigation is safe to use in lumbar spine surgery, it is unclear if the increased cost and time associated with this technology provide benefits warranting its use in routine lumbar spine surgery. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Preparation and Assessment of an Individualized Navigation Template for Lower Cervical Anterior Transpedicular Screw Insertion Using a Three-Dimensional Printing Technique.

Prospective trial. To establish an individualized navigation template for safe and accurate insertion of lower cervical anterior transpedicular screw (ATPS) based on a three-dimensional (3D) printing technique. Conventional screw insertion manually under fluoroscopy easily leading to deviation of ATPS screw channel, cervical instrumentation procedures demand the need for a precise technique for screw placement. Twenty adult cervical spine specimens (10 men and 10 women, with a mean age of 50.29 ± 6.98) were selected for computed tomography pre- and postoperatively. A 3D lower cervical spine model was reconstructed using Mimics software to measure the screw-related parameters and generate a reverse template with optimal screw channel as well as a prototype using 3D printing. Assisted by the navigation template, bilateral ATPS were inserted into the cadavers. The mean outer width and height of pedicle were 5.31 ± 1.23 and 6.78 ± 1.10 mm, respectively. The average length, sagittal, and axial angles of the optimal screw channel obtained through the optimal entry point were 36.34 ± 4.39 mm, 40.67° ± 5.10°, and 93.7° ± 7.96°, respectively. The adjustable safe ranges of sagittal and axial angles were 3.89° ± 1.13° and 5.64° ± 0.97°, respectively. The axial and sagittal accuracies of the 200 screws were 99.5% and 97%, respectively. The average deviations of the actual entry point and the preset opening in the X, Y, and Z axes were 0.39 ± 0.43, 0.21 ± 0.41, and 0.29 ± 0.14 mm, respectively (P > 0.05). An individualized ATPS navigation template was developed using Mimics software and 3D printing prototyping, based on computed tomography, for highly accurate screw insertion. 4.

Straight-Forward versus Bicortical Fixation Penetrating Endplate in Lumbosacral Fixation-A Biomechanical Study.

ObjectiveMany lumbosacral fixation techniques have been described to offer a more screw-bone purchase. The forward anatomical fixation parallel to the endplate is still the most preferred method. Literature revealed little knowledge regarding the mechanical stability of lumbosacral trans-endplate fixation compared to the traditional trans-pedicular screw fixation method. The aim of this study is to assess the pull-out strength of lumbosacral screws penetrating the end plate and comparing it to the conventional trans-pedicular screw insertion method.MethodsEight lumbar and eight sacral vertebrae, with average age 69.4 years, Left pedicles of the 5th lumbar vertebrae were used for trans-endplate screw fixation, group 1A, right pedicles were used for anatomical trans-pedicular screw fixation, group 1B. In the sacral vertebrae, the right side S1 pedicles were used for trans-endplate fixation, group 2A, left side pedicles were used for anatomical trans-pedicular screw fixation, group 2B. The biomechanical tests were performed using the axial compression testing machine. All tests were applied using 2 mm/min traction speed.ResultsThe average pull-out strength values of groups 1A and 1B were 403.78±11.71 N and 306.26±17.55 N, respectively. A statistical significance was detected with p=0.012. The average pull-out strength values of groups 2A and 2B were 388.73±17.03 N and 299.84±17.52 N, respectively. A statistical significance was detected with p=0.012.ConclusionThe trans-endplate lumbosacral fixation method is a trustable fixation method with a stronger screw-bone purchase and offer a good alternative for surgeons specially in patients with osteoporosis.

Does Navigation Improve Pedicle Screw Placement Accuracy? Comparison Between Navigated and Non-navigated Percutaneous and Open Fixations.

The aim of our study was to assess how a preoperative computed tomography (CT)-based navigation system affected the correctness and safety of transpedicular screw insertion, compared with standard techniques. Between January 2012 and February 2014, 203 patients underwent thoracic and lumbar fixation, with open and percutaneous techniques; 218 screws were implanted through an open navigated technique (1.0 Spine & Trauma 3d ver. 2.0 BrainLab, Feldkirchen Germany) in 43 patients; 220 screws were inserted with an open free-hand technique in 45 patients; 230 screws were implanted in 56 patients using percutaneous CT-based navigation; and 236 screws were inserted in 59 patients using a percutaneous fluoroscopy-guided technique. To our knowledge, this is the first work comparing these four different techniques. The position of each screw was evaluated on CT scan reconstruction and classified according to a four-point grading scale (grade 0: no breach, grade 1: breach < 2 mm, grade 2: breach between 2 and 4 mm; grade 3: breach >4 mm). Statistical analysis was assessed by two-way analysis of variance (ANOVA) t test, while the Fisher least significant difference (LSD) method was employed to determine statistical significance. Statistical analysis showed a significant difference in accuracy between the open CT-based navigation and the percutaneous CT-based navigation techniques (P= 0.0263) and between the open CT-based navigation and the percutaneous fluoroscopy-guided techniques (P=0.0258): a particular difference was observed in anterior misplacement between open CT-based navigation and the percutaneous fluoroscopy-guided technique (P= 0.0153). Our results confirm the advantages of the navigation technique, which ensures greater accuracy, in open as well as percutaneous procedures.

Accuracy of 3D fluoroscopy-navigated anterior transpedicular screw insertion in the cervical spine: an experimental study

The technique of pedicle screw stabilization is finding increasing popularity for use in the cervical spine. Implementing anterior transpedicular screws (ATPS) in cervical spine offers theoretical advantages compared to posterior stabilization. The goal of the current study was the development of a new setting for navigated insertion of ATPS, combining the advantage of reduced invasiveness of an anterior approach with the technical advantages of navigation. 20 screws were implanted in levels C3 to C6 of four cervical spine models (SAWBONES(®) Cervical Vertebrae with Anterior Ligament) with the use of 3D fluoroscopy navigation system [Arcadis Orbic 3D, Siemens and VectorVision fluoro 3D trauma software (BrainLAB)]. The accuracy of inserted screws was analyzed according to postoperative CT scans and following the modified Gertzbein and Robbins classification. 20 anterior pedicle screws were placed in four human cervical spine models. Of these, eight screws were placed in C3, two screws in C4, six screws in C5, and four screws in C6. 16 of 20 screws (80%) reached a grade 1 level of accuracy according to the modified Gertzbein and Robbins Classification. Three screws (15%) were grade 2, and one screw (5%) was grade 3. Grade 4 and 5 positions were not evident. Summing grades 1 and 2 together as "good" positions, 95% of the screws achieved this level. Only a single screw did not fulfill these criteria. The setting introduced in this study for navigated insertion of ATPS into cervical spine bone models is well implemented and shows excellent results, with an accuracy of 95% (Gertzbein and Robbins grade 2 or better). Thus, this preliminary study represents a prelude to larger studies with larger case numbers on human specimens.

Biomechanical Evaluation of the Pedicle Screw Insertion Depth Effect on Screw Stability Under Cyclic Loading and Subsequent Pullout

A biomechanical ex vivo study of the human lumbar spine. To evaluate the effects of transpedicular screw insertion depth on overall screw stability and pullout strength following cyclic loading in the osteoporotic lumbar spine. Although much is known about the clinical outcomes of spinal fusion, questions remain in our understanding of the biomechanical strength of lumbar pedicle screw fixation as it relates to screw sizing and placement. Biomechanical analyses examining ideal pedicle screw depth with current pedicle screw technology are limited. In the osteoporotic spine, optimized pedicle screw insertion depth may improve construct strength, decreasing the risk of loosening or pullout. A total of 100 pedicles from 10 osteoporotic lumbar spines were randomly instrumented with pedicle screws in mid-body, pericortical, and bicortical depths. Instrumented specimens underwent cyclic loading (5000 cycles of ±2 N m pure flexion moment) and subsequent pullout. Screw loosening, failure loads, and energy absorption were calculated. Cyclic loading significantly (P<0.001) reduced screw-bone angular stiffness between prefatigue and postfatigue conditions by 25.6%±17.9% (mid-body), 20.8%±14.4% (pericortical), and 14.0%±13.0% (bicortical). Increased insertion depth resulted in lower levels of reduction in angular stiffness, which was only significant between mid-body and bicortical screws (P=0.009). Pullout force and energy of 583±306 N and 1.75±1.98 N m (mid-body), 713±321 N and 2.40±1.79 N m (pericortical), and 797±285 N and 2.97±2.33 N m (bicortical) were observed, respectively. Increased insertion depth resulted in higher magnitudes of both pullout force and energy, which was significant only for pullout force between mid-body and bicortical screws (P=0.005). Although increased screw depth led to increased fixation and decreased loosening, additional purchase of the stiff anterior cortex is essential to reach superior screw-bone construct stability and stiffness.

Local Tissue Electrical Resistances in Transpedicular Screw Application in the Thoracolumbar Region.

To determine local tissue electrical resistance differences generated during a screw pass from the pedicle to another tissue rather than determining all individual electrical tissue resistance values. We attempted to measure electrical resistance values of regional tissues in addition to fluoroscopic imaging during application of fixation via a transpedicular screw. We also attempted to detect local tissue electrical resistance alterations in case of malposition of the screw inside the pedicle. For this purpose, local tissue electrical resistances of 10 transpedicular tracks opened with standard track openers bilaterally in 5 vertebrae, and of spinal cord accessed by puncturing the medial walls of three vertebrae in a cadaver were measured. These resistance differences were not only measured in human cadaveric tissue but also in 36 pedicles belonging to a total of 18 vertebrae between Th 1-S1 vertebrae of a sheep cadaver. Both medial and lateral walls were drilled to measure local tissue resistance differences in a sheep cadaver. Our results indicated that local tissue electrical resistance changes were statistically significant in both human and sheep cadaver. It is possible to prevent screw malposition using a simple and cheap electrical resistance measurement. Local tissue electrical resistance measurement during transpedicular screw insertion is a safe, simple, cheap, and practical method.

Computed Tomographic Measurement of Cervical Pedicle Morphology in Filipino Patients

Introduction: Studies have shown that Asian cervical pedicles are significantly smaller, thus increasing the technical difficulty of screw insertion when using standard 3.5 mm pedicle screws. Cervical pedicle morphology of a sample of Filipino patients was assessed using computed tomographic measurements. Objective: The study was carried out to measure the cervical pedicles and assess the feasibility of transpedicular screw fixation in the local setting. Methods: CT scans of bilateral C2 to C7 pedicles of 94 Filipinos with a mean age 52.9 years old (range: 18 to 82) composed of 37 females and 57 males were evaluated for inner diameter, lateral wall, and medial wall thickness. Results: The inner diameter of male pedicles was significantly wider compared to females. The medial wall and lateral wall thickness of males was also significantly greater except for C2-C5 and C2 &amp; C6 respectively. C3 to C5 of male pedicles had a mean inner diameter of &lt; 3.1 mm compared to C2 to C6 in females. For mean lateral wall thickness, only the right C4 and C5 lateral wall thickness in females was&lt; 1.0 mm. All cervical spine levels in both males and females had a mean medial wall thickness of &gt; 1.0 mm (range 1.47 to 1.89mm). Conclusion: The cervical pedicles of Filipinos are smaller than those reported in Euro-American populations and may be too small to adequately accommodate transpedicular screw fixation using 3.5 mm screws. It is recommended that pre-operative imaging for all levels should be performed when transpedicular screw insertion is indicated. Key words: cervical spine, morphometry, transpedicular fixation, computed tomography