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OBJECTIVE To evaluate S1 transsacral (TS) corridors on reformatted and non-reformatted computed tomography (CT) images to determine which most reliably identifies narrow corridors. DESIGN Retrospective cohort. SETTING Level 1 trauma center. PATIENTS 245 patients with operative pelvic ring injuries. INTERVENTION CT scan review. MAIN OUTCOME MEASUREMENTS Preoperative CT scans were evaluated to determine the width of the S1 TS corridor on standard axial non-reformatted (ANR), axial reformatted (AR), and coronal reformatted (CR) images. Sensitivity and specificity of each format to detect a narrow corridor (

Background The introduction of intraoperative computed tomography (iCT) could improve the surgical results of C1-C2 stabilization by Goel-Harms, especially in patients with complex deformities. This study aims to investigate the impact of iCT on the accuracy of C1-C2 screw positioning and to develop a score based on multiparametric analysis of imaging data (Cervical Screw Placement Accuracy score [CSPAs]). Methods Twenty-one patients were retrospectively evaluated. The data obtained with the use of an iCT were compared with the incidence of cases of malpositioning in the literature. Multiparametric imaging criteria were developed: the 82 screw positions were evaluated using the CSPA criteria and 2 additional variables. The CSPAs was obtained from the aggregation of the CSPAs criteria: optimal (CSPAs ≥8), suboptimal (CSPAs = 6–7), malpositioned (CSPAs ≤5). Results The average incidence of malpositioning in C1-C2 arthrodesis decreased from 13% without iCT to 1.2% with the aid of iCT, considering a monoparametric value. The CSPAs analysis shows a greater discretion and higher number of well-defined categories of the accuracy of C1-C2 screw position: optimal, 80.3%; suboptimal, 17.1%; and malposition, 2.6%. A correlation was observed between the accuracy of the positioning of both right and left screws in C2. Furthermore, the anatomic site of C2 screws was found to be a predictor of cortical invasion. Conclusions The results suggest that the introduction of the iCT is associated with a consistent improvement of the accuracy in the positioning of the screws. A multiparametric score (CSPAs) could improve the assessment of screw placement.

The study design is retrospective, multi-surgeon, single-center review. The objective is to evaluate complication rates, revision rates, and accuracy grading for robotic-guided S2 alar-iliac (S2AI) screws. Sixty-five consecutive patients underwent S2AI fixation (118 screws) as part of a posterior spine fusion using robotic-guidance. Screws were placed percutaneously in 14 cases and 51 were placed in an open fashion by three board-certified spine surgeons using the Mazor core technology robotic systems (Mazor X, n = 42; Mazor XSE, n = 23). Medical charts were retrospectively reviewed for revisions and complications. All patients were followed for 90 days or greater. Postoperative CT scans were obtained in 22 of the 51 patients, allowing for 46 screws to be reviewed by an independent neuroradiologist who graded the screws for accuracy. There were no intraoperative or postoperative complications associated with S2AI screw placement. There were no revisions found to be related to the S2AI screw placement. All 46 screws evaluated with postoperative CT scans were reported as being at the highest level of accuracy, grade A, with a breach distance of 0 mm (no breach). The robotic-guided technique for S2AI screw placement is a reliable method to achieving pelvic fixation with low complication and revision rates. In addition, a high degree of accuracy can be achieved without relying on visible and tactile landmarks needed for the freehand technique or the additional radiation associated with fluoroscopic-guidance.

Objectives The aim of this study was to report the use of computed tomography (CT) for postoperative evaluation of the accuracy of sacroiliac reduction and minimally invasive screw fixation in a series of five cats. Methods Medical records between January 2016 and March 2017 of cats presenting to the author's institution were reviewed. Included were cats that had undergone minimally invasive sacroiliac screw fixation with a complete medical record and pre- and postoperative radiographs. Screw size was obtained from the medical records. CT images were acquired prospectively and evaluated to assess joint reduction, relative screw size and screw positioning. Results Six sacroiliac luxations and 6 screws were available. Fixation was achieved with either a 2.4 (n = 1) or 2.7 mm (n = 5), 316L stainless steel, cortical bone screw. Mean screw size as a proportion of sacral diameter was 47.7%. Sacroiliac reduction >90% in the craniocaudal plane and sacral screw purchase >60% of the sacral width were achieved in 3/5 cases. Mean dorsoventral screw angulation was 1.6 degrees (range: −9.7 to 11.7 degrees) and craniocaudal angulation was −4.5 degrees (range: −16.6 to 6.6 degrees). Complications included screw loosening in the one case of bilateral repair and penetration of the neural canal in one case which was not detected with postoperative radiographic evaluation. Clinical Significance CT evaluation provides a useful method for the assessment of sacroiliac reduction and the accuracy of screw placement.

CASE DESCRIPTION A 2.5-month-old 17.5-kg female alpaca cria was presented for evaluation and treatment of severe bilateral carpal varus deformities. CLINICAL FINDINGS No lameness was evident at a walk, and neither carpal varus deformity could be corrected by means of manipulation. Radiography revealed severe varus of the left (27°) and right (21°) carpal regions. No additional conformational abnormalities were detected. TREATMENT AND OUTCOME A single 2.7-mm transphyseal cortical screw was placed in the distolateral aspect of the radius in each limb. On reexamination 8 weeks after screw placement, the left carpal varus deformity had corrected from 27° to 2.6°, and the left transphyseal screw was removed. The right carpal varus deformity had improved but was still present (18°), and hemicircumferential periosteal transection and elevation was performed on the mediodistal aspect of the right radius. Five weeks after the second surgery, the right carpal varus deformity had corrected to 2.4°, and the right transphyseal screw was removed. Six months after the second screw removal, both thoracic limbs remained straight, the cria had a normal gait, and the owner was happy with the cosmetic result. CLINICAL RELEVANCE Placement of a single transphyseal cortical screw with or without the addition of hemicircumferential periosteal transection and elevation can provide a favorable outcome in skeletally immature alpacas with severe carpal varus deformities.

Little information exists regarding the benefit of computer navigation in shoulder arthroplasty in the clinical setting. This study aimed to quantify how computer navigation affects the number and length of screws used during in vivo reverse total shoulder arthroplasty (RSA) placement.We performed a retrospective review of a research database to identify patients who underwent primary RSA before and after the use of computer navigation between January 1, 2015, and December 31, 2019. One hundred consecutive RSAs were selected from the computer navigation implantation date; then, 100 consecutive sex-matched RSAs were chosen prior to navigation implantation in reverse chronologic order. Baseplate augmentations were chosen based on surgeon discretion, with the goal of restoring version to within 10° of neutral and inclination to neutral or slightly inferior with removal of the smallest amount of subchondral bone possible. Screws were placed with the goal of ≥3 screws with good purchase and were added as needed, with up to 5 screws used. We compared demographic factors, comorbidities, preoperative diagnosis, number of screws, screw length, number of wasted screws, and number of cases with bone graft used behind the baseplate between the 2 groups. We used the χA total of 200 RSAs were included, with 100 primary RSAs (mean age, 69.3 years) performed prior to computer navigation compared with 100 primary RSAs (mean age, 69.7 years) performed using computer navigation. The total number of screws used in RSAs without computer navigation was 414; the total used in the computer navigation cases was 344. RSAs placed with computer navigation used significantly fewer screws per case (3.4 screws vs. 4.1 screws, P.001) and had a significantly greater average screw length (35.0 mm vs. 32.6 mm, P.001). Three screws were implanted in 61% of computer navigation cases vs. 1% of cases without computer navigation (P.001). Screws ≥ 30 mm in length were more commonly used in patients undergoing RSA using computer navigation (84.6% vs. 73.7%, P.001).This study shows that computer navigation in RSA leads to longer and fewer glenoid baseplate screws being implanted. Computer navigation appears to assist with better screw placement, which may have similar clinical benefits of better glenoid fixation. Additionally, using fewer screws can save glenoid bone stock, avoid added glenoid stress risers, and decrease operative time.

Introduction Percutaneous screw fixation of the posterior pelvic ring is a popular technique to treat unstable pelvic ring lesions. This technique is practicable in both, the high-energy pelvic ring fractures, mostly in the young population as well as the osteoporotic fractures in the elderly. Risk of the transiliac-transsacral screw positioning is that the critical area of nerve root exit has to be passed twice. For secure screw placement, without causing iatrogenic neurovascular injuries, the knowledge of distances to the narrowest areas is essential. Purpose of this anatomical study was to examine the optimal intraosseous screw placement for the first two sacral segments. Material/methods Images of uninjured pelves from 50 patients (64-line CT scanner) were evaluated. Then virtual transiliac-transsacral srews were positioned into the first two sacral segments. The distance from the screws’ entrance points at the ilium's alar bone to the narrowest portion of the whole pedicle as well as the height and width in this area were measured. Descriptive statistics were used and gender related differences were evaluated using student T-test. Results For the first sacral segment the distance to the narrowest zone amounted in mean 62.75 mm, respectively 63.31 mm, depending on the selected way of measurement. For the second segment the mean distance to the neuroforamina was on average 50.61 mm, respectively 51.54 mm. The average height in S1 measured 25.88 mm and the average width 25.49 mm. The average height for S2 was 17.54 mm and the average width 17.61 mm. We could not find any statistically significant gender correlation for the measured distances. Conclusion Results of this anatomical study may help in performing a safe surgical procedure.

OBJECTIVE This is a retrospective study of a series of occipitocervical fusion procedures with condylar screw fixation in which the authors investigated the utility of electromyography (EMG, free-running and triggered) as a reliable tool in assessing the positioning of condylar screws. This series consisted of 197 patients between 15 and 60 years of age who presented with craniocervical instability, and who were treated between October 2014 and December 2017. METHODS Intraoperative free-running EMG was observed at the placement of condylar screws, as well as at realigning of the spine. After placement the condylar screws were stimulated electrically, and the thresholds were recorded. CT scans were obtained intraoperatively soon after screw stimulation, and the results were analyzed by the surgeon in real time. Free-running EMG results and triggered EMG thresholds were tabulated, and the minimum acceptable threshold was established. RESULTS Intraoperative free-running EMG and triggered EMG were able to correlate alerts with condylar screw placement accurately. A triggered EMG threshold of 2.7 mA was found to be a minimum acceptable threshold. A combination criterion of free-running EMG and triggered EMG alerts was found to enable accurate assessment of condylar screw positioning and placement. CONCLUSIONS Intraoperative free-running EMG and triggered EMG were both found to be invaluable utilities in assessing the placement and positioning of condylar screws. Stimulation thresholds below 2.7 mA correlated with a superior or anterior condylar breach. Thresholds in the 2.7-mA to 9.0-mA range were generally acceptable but warranted additional inspection by the surgeon. Threshold values above 9.0 mA corresponded with solid condylar screw placement.

Outcomes for adult spinal deformity continue to improve as new technologies become integrated into clinical practice. Machine learning, robot-guided spinal surgery, and patientspecific rods are tools that are being used to improve preoperative planning and patient satisfaction. Machine learning can be used to predict complications, readmissions, and generate postoperative radiographs which can be shown to patients to guide discussions about surgery. Robot-guided spinal surgery is a rapidly growing field showing signs of greater accuracy in screw placement during surgery. Patient-specific rods offer improved outcomes through higher correction rates and decreased rates of rod breakage while decreasing operative time. The objective of this review is to evaluate trends in the literature about machine learning, robot-guided spinal surgery, and patient-specific rods in the treatment of adult spinal deformity.

BACKGROUND To show a novel modified technique to perform minimally invasive anterior odontoid screw fixation. METHODS Twenty-nine patients with a mean age of 45 years were treated with a modified percutaneous anterior odontoid screw fixation. All patients were affected by Type II or rostral shallow Type III odontoid fractures. A modified guide tube was used in all these patients, with reduction of soft tissue dissection for percutaneous approach. RESULTS There were no complications related to the modified technique. Good results and optimal screw placement were achieved in 28 out of 29 patients. Only in 1 patient we observed, after mobilization, screw displacement, probably due to severe osteoporosis. CONCLUSIONS In our opinion, this modified percutaneous minimally invasive technique for anterior odontoid screw fixation, along with the use of a soft tissue dilator not fixed to the spine, has not yet been reported in literature and is strongly recommended to reduce invasiveness of odontoid screw placement.

Percutaneous screw fixation combined with pelvic reduction is a surgical technique used to stabilize fractures of the posterior pelvic ring. This is the standard surgical treatment of unstable posterior pelvic ring injuries. The primary goal of this treatment is an anatomic reduction and stable fixation. This has been shown to reduce pain and improve the patients' long-term well-being. The aim of this analysis was to determine the possible screw lengths and the positioning of the screws in the S1 and S2 sacral segments. A population of 697 pelvises from the Stryker Orthopaedic Modeling and Analytics database were analyzed. The dimensions of the S1 and S2 screw corridors were determined and after assessing for sacral dysmorphism, the correct screw placement was chosen to determine the necessary screw length for surgical treatment. The measurements of the screw lengths show a Gaussian distribution for the analyzed population. The percentage of dysmorphic pelvises for the S1 screw corridor was 31.3% and for the S2 corridor 8%. Average screw length for S1 was 163.8 ± 16.2 mm and for the S2 137.3 ± 9.5 mm. The results show that the S1/S2 axis cannot be used for a trans-sacral screw placement in every patient. The study shows that intraosseous screw corridors are present in 68.7% of the patients in the S1 position and in 92% at the S2 level where an intended implant can be placed fully intraosseous.

To report our experience using the scan-and-plan workflow and review current literature on surgical efficiency, safety, and accuracy of next-generation robot-assisted (RA) spine surgery.The records of patients who underwent RA pedicle screw fixation were reviewed. The accuracy of pedicle screw placement was determined based on the Ravi classification system. To evaluate workflow efficiency, 3 demographically matched cohorts were created to analyze differences in time per screw placement (defined as operating room [OR] time divided by number of screws placed). Group A had4 screws placed, Group B had 4 screws placed, and Group C had4 screws placed. Intraoperative errors and postoperative complications were collected to elucidate safety.Eighty-four RA cases (306 pedicle screws) were included for analysis. The mean number of screws placed was 2.1 ± 0.3 in Group A and 6.4 ± 1.2 in Group C; 4 screws were placed in Group B patients. The accuracy rate (Ravi grade I) was 98.4%. Screw placement time was significantly longer in Group A (101 ± 37.7 minutes) than Group B (50.5 ± 25.4 minutes) or C (43.6 ± 14.7 minutes). There were no intraoperative complications, robot failures, or in-hospital complications requiring a return to the OR.The scan-and-plan workflow allowed for a high degree of accuracy. It was a safe method that provided a smooth and efficient OR workflow without registration errors or robotic failures. After the placement of 4 pedicle screws, the per-screw time remained constant. Further studies regarding efficiency and utility in multilevel procedures are necessary.

Study Design: Retrospective matched-pair analysis. Objectives: Lumbosacral transitional vertebrae (LSTV) have a reported prevalence of 4-36% in the population. The safe zones for screw placement for spinopelvic fusion in adult spinal deformity surgery for patients with LSTV have not been described in the literature. Our study aimed to assess the safety of S1-pedicle screw (S1PS), S2-alar screw (S2AS), S2-alar-iliac screw (S2AIS), and iliac screw (IS) placement in patients with LSTV. Methods: Out of the 819 examined patients, 49 patients with LSTV were included in our retrospective analysis with a matched pair control group. We used the 3-dimensional planning tool mediCAD for screw placement of S1PS, S2AS, S2AIS, IS with different angles, length and diameters. Results: We evaluated a total of 10 192 screw trajectories. No serious complications occurred due to the trajectories used for S1PS. LSTV increased the risk of vessel injury for S2AS trajectories ( P = .001) but not for S2AIS ( P = .526). Besides the presence of an LSTV, the screw trajectory had a major influence on the frequency of serious complications. Conclusions: Sacral anchoring of long spinal constructions using S1PS, S2AS, S2AIS and IS is also possible in the presence of LSTV. For S2AS the trajectory with 30° lateral and caudal angulation of 10° showed the least vascular injuries and the least sacro-iliac-joint violations in patients with LSTV. S2AIS trajectories with 40° lateral and 0° sagittal angulation reduced the risk of serious complications in our patients collective with LSTV.

Background The preoperative assessment of C2 morphology is important for safe instrumentation. Sclerotic changes are often seen in C2 pedicles. Evaluating the diameter measurements solely might not accurately assess the safety of screw insertion. We have proposed a novel grading system of the C2 pedicle that includes sclerosis and evaluated the predictive value of this grading system with the surgeon's safety evaluation. Methods We reviewed and measured the dimensional values in 220 cervical computed tomography angiograms. Additionally, we used a grading system that divides the findings into 5 grades according to the width measurement and degree of sclerosis in the C2 pedicle. Two spine surgeons independently classified the pedicles as follows: safe (minimal risk of pedicle violation), caution needed (caution to minimize pedicle violation), or dangerous (a high risk of pedicle violation). Finally, we compared the measurements and the surgeons' safety assessments. Results A total of 411 pedicles of 203 patients (mean age, 69.5 years; 49.5% women) were included. Of the 411 C2 pedicles, 170 were classified as high risk by ≥1 surgeon. Between the dimensional measurements and grading system, the sclerotic grade showed the best predictive value. Conclusions We have introduced a novel tool to evaluate the safety of C2 pedicle screw placement. Our results suggest that our pedicle width–sclerosis grading system is reproducible and predicts the surgeon's assessment of safe screw placement better than C2 pedicle diametrical measurements alone.

The objectives of this in vivo experimental study were to evaluate the feasibility of cortical screw insertion into the intact distal phalanx in standing sedated horses and to document potential postoperative complications. One cortical screw was randomly inserted in lag fashion into each distal phalanx in 9 horses. The second surgery on the contralateral limbs was performed 2–3 weeks after the first operation, when a 4.5-mm cortical screw was inserted in lag fashion into the distal phalanx of sedated horses following perineural analgesia. Following surgery, the drill hole was filled with an antibiotic-soaked swab, which was changed every 48 h. The horses were euthanised 8 weeks after the second surgery. The hooves were disarticulated and evaluated macroscopically and by computed tomography. The surgery time was 13.9 ± 4.8 min (mean ± SD). Pain scores and lameness gradually decreased after 7 days. Solar canal penetration (SCP) was detected in 10 out of the 18 distal phalanges (55.5%). In 7 out of the 10 penetrations intraoperative bleeding was obvious. No postoperative infection was observed. Screw insertion into the distal phalanx was easily and quickly accomplished in standing horses, but its advantages in horses with sagittal fractures should be investigated further. SCP had no impact on postoperative lameness.

BACKGROUND: This study evaluates the accuracy, biomechanical profile, and learning curve of the transverse process trajectory technique (TPT) compared to the straightforward (SF) and in-out-in (IOI) techniques. SF and IOI have been used for fixation in the thoracic spine. Although widely used, there are associated learning curves and symptomatic pedicular breaches. We have found the transverse process to be a reproducible pathway into the pedicle. METHODS: Three surgeons with varying experience (experienced [E] with 20 years in practice, surgeon [S] with less than 10 years in practice, and senior resident trainee [T] with no experience with TPT) operated on 8 cadavers. In phase 1, each surgeon instrumented 2 cadavers, alternating between TPT and SF from T1 to T12 (n = 48 total levels). In phase 2, the E and T surgeons instrumented 1 cadaver each, alternating between TPT and IOI. Computed tomography scans were analyzed for accuracy of screw placement, defined as the percentage of placements without critical breaches. Axial pullout and derotational force testing were performed. Statistical analyses include paired t test and analysis of variance with Tukey correction. RESULTS: Overall accuracy of screw placement was comparable between techniques (TPT: 92.7%; SF: 97.2%; IOI: 95.8%; P = .4151). Accuracy by technique did not differ for each individual surgeon (E: P = .7733; S: P = .3475; T: P = .4191) or by experience level by technique (TPT: P = .1127; FH: P = .5979; IOI: P = .5935). Pullout strength was comparable between TPT and SF (571 vs 442 N, P = .3164) but was greater for TPT versus IOI (454 vs 215 N, P = .0156). There was a trend toward improved derotational force for TPT versus SF (1.06 vs 0.93 Nm/degrees, P = .0728) but not for TPT versus IOI (1.36 vs 1.16 Nm/degrees, P = .74). Screw placement time was shortest for E and longest for T for TPT and SF and not different for IOI (TPT: P = .0349; SF: P < .0001; IOI: P = .1787) but did not vary by technique. CONCLUSIONS: We describe the TPT, which uses the transverse process as a corridor through the pedicle. TPT is an accurate method of thoracic pedicle screw placement with potential biomechanical advantages and with acceptable learning curve characteristics. CLINICAL RELEVANCE: This study provides the surgeon with a new trajectory for pedicle screw placement that can be used in clinical practice.

Introduction The purpose of this investigation was to determine the impact of simulator practice on task completion time, radiation use, success rate, and overall quality in a simulation of placing a distal locking screw. Methods This was a prospective, randomized control trial with one-to-one randomization and parallel group design. Twenty-eight volunteer novice trainees (medical and premedical students) participated. Using the TraumaVision Virtual Reality Simulator (Swemac, Sweden), subjects performed locking screw placement using the "perfect circle" technique. All subjects underwent a pretest and posttest on the simulator. The simulator group completed three additional simulator training sessions. The primary outcome variables were simulator-collected task completion time, success rate, radiation exposure time, and overall score. Results No notable difference existed between groups for pretest completion time, radiation use, success rate, or overall score. No notable difference in posttest radiation use or overall procedure score was found between groups. A significant difference existed in posttest total completion time (trained = 251.2 ± 103.4; control = 497.3 ± 223.1; P = 0.001) and success rate (64.3% versus 100%; P = 0.041) between groups. In addition, a significant difference existed in variance between groups for completion time (P = 0.029). Conclusions These findings suggest that independent simulator practice leads to improved speed and success rates; however, radiation use and overall score do not improve in the same manner. The design of simulator-based curriculum must be tailored to specific educational objectives and ultimately validated in the clinical setting.

OBJECTIVE To determine the influence of a custom 3D-printed guide for placement of cortical bone screws in the equine navicular bone. STUDY DESIGN Ex vivo study. SAMPLE POPULATION Eight pairs of normal adult equine forelimbs. METHODS A 3.5 × 55 mm cortical screw was placed in the longitudinal axis of each intact navicular bone. Screws were placed with a 3D-printed guide (3D) in one bone and with a traditional aiming device (AD) in the contralateral bone within each pair. Duration of surgery and the number of fluoroscopy images were compared between techniques. Screw placement was subjectively evaluated by gross examination and scored by three boarded veterinary surgeons. RESULTS The use of a 3D-printed guide reduced the duration of surgery by 6.6 min (±1.5 min) compared to traditional screw placement (20.7 min ± 4.8 min, p

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.

The purpose of this study was to determine the angular tolerance of the S1 and S2 segments to accommodate a transiliosacral screw across both sacroiliac joints. We hypothesized that the angular tolerance for transiliosacral screw placement would be more constrained than the angular tolerance for iliosacral fixation in pelves where a safe osseous corridor was measured. The cortical boundaries of the S1 and S2 sacral segments in 433 pelvic CTs were digitally mapped. A straight-line path was placed within each osseous corridor and extended across both SI joints past the outer iliac cortices. The diameter of the path was increased until it breached the cortex, geometrically determining maximum diameter (Dmax). Angular tolerance for screw placement was calculated with trigonometric analysis of the Dmax value of the corridor, and the average distance from the termination of the osseous corridor to the site of percutaneous insertion. Gender, age, and BMI were evaluated as independent predictors using binomial logistic regression. The transiliosacral angular tolerance for the S1 and S2 osseous corridors was 1.53 ± 0.57 degrees and 1.02 ± 0.33 degrees, respectively. 68.9% of S1 corridors and 81.1% of S2 corridors had a safe zone (corridor diameter ≥ 10 mm) for transiliosacral placement, 48.3% of the pelves had a safe zone for both corridors, while 5.1% had no safe zones. Females had a less frequent Dmax ≥ 10 mm at S1, 52% vs 67% (p = 0.001), and at S2, 64% vs 86% (p

Objectives The purpose of this study is to design a radiographic map of the femoral neck showing proportion-based locations of the safe zones for screw placement with widest bony extents in anteroposterior and lateral radiographs using normal computed tomography-based data. Methods We analyzed computed tomography-based studies of 50 intact normal proximal femora equally from male and female subjects. Using software-developed radiographs, the proportionate locations of the maximal anteroposterior and cephalocaudal extents in both constricted zones were measured. The width of the femoral neck in the measurement zone was taken as the reference for calculation of proportions. Results For anteroposterior radiographs, the anteroposterior safe zones in the femoral neck are located at the gradients of 34.21% and 34.33% from the superior border in midcervical and basicervical regions, respectively. In lateral radiographs, they correlate with the visible anterior extent of femoral neck and lie at a gradient of 7.16% and 11.79% from the visible posterior border in midcervical and basicervical regions, respectively. In lateral radiographs, the calcar-based cephalocaudal safe zone was located at the gradients of 43.49% and 39.53% from the visible posterior border in midcervical and basicervical regions, respectively. In anteroposterior radiographs, cephalic limit of the calcar-based safe zone is located at the gradients of 9.63% and 17.82% from the superior border in midcervical and basicervical regions, respectively. Conclusions Radiographic margins cannot be reliably trusted for screw fixation of femoral neck fractures. The proportionate locations of the anteroposterior and calcar-based cephalocaudal safe zones with widest bone stock in anteroposterior and lateral fluoroscopic projections can help in the safe placement of screws for fixation of femoral neck fractures.

Study Design: This is an observational study of computed tomography (CT) data.Purpose: The C1 and C2 laminas in the Malaysian Malay population were analyzed for the feasibility of fitting 3.5-mm laminar screws in a cross configuration.Overview of Literature: Morphometric analysis of the C1 and C2 laminas has been performed for various populations but not for the Malaysian Malay population.Methods: A total of 330 CT cervical images were measured to establish the bicortical diameter of the C1 and C2 laminas as well as their height and length. The C1 posterior tubercle bicortical diameter and height were also determined from these images. All parameters were measured up to 0.1 mm, and statistical analysis was performed using IBM SPSS Statistics ver. 24.0 (IBM Corp., Armonk, NY, USA). An independent t -test and the Pearson chi-square test were used to determine the mean difference and screw acceptance.Results: The means of the C1 lamina measurements were 5.79±1.19 mm in diameter, 9.76±1.51 mm in height, and 20.70±1.86 mm in length. The means of the measurements of the posterior tubercle were 7.20±1.88 mm in diameter and 10.51±1.68 mm in height. The means of the C2 lamina measurements were 5.74±1.31 mm in diameter, 11.76±1.69 mm in height, and 24.96±2.56 mm in length. Overall 65.5% of C1 and 80.3% of C2 laminas are able to accept 3.5-mm screws in a cross configuration. Screw acceptability is similar between the right and left sides (p >0.05). However, males have a higher screw acceptability compared with females (p

Background Although the pelvic vascular injury caused by a transacetabular screw is rare, it is a major local complication of total hip arthroplasty. We aimed to obtain anthropometric data about the safe zone for the placement of transacetabular screws by analyzing the three-dimensional (3D) reconstruction model and determine the safe length of transacetabular screws by performing the 3D simulated surgery. Methods We reviewed 50 hips of 25 patients who underwent lower extremity angiographic computed tomography scans retrospectively. We reconstructed the 3D models of 50 hips with normal pelvic bone and vascular status using the customized computer software. We measured the central angle and safe depth of the safe zone of the transacetabular screws on the 3D models. We also performed the 3D simulated surgery to confirm the safe length of screws in each hole of the customized cup implant. Results The measured central angle of the posterior-superior area was 79.5°. And we determined a mean safe depth of 49.8 mm in the safe zone, with a central angle of 47.7°. During the 3D simulated surgery, we determined a mean safe length of the transacetabular screw of 43.3 mm when applied to a lateral hole on a line bisecting the posterior-superior area. Conclusion Although our study was limited by the use of a virtual computer program, the quantitative measurements obtained can help reduce the incidence of pelvic vascular injury during transacetabular screw fixation in total hip arthroplasty.

BackgroundHigh-riding vertebral artery (HRVA) and narrow C2 pedicles (C2P) pose a great risk of injuring the vessel during C2 pedicle or transarticular screw placement. Recent meta-analysis revealed a paucity of European studies regarding measurements and prevalence of these anatomical variants.Methods383 consecutive cervical spine CT scans with 766 potential screw insertion sites were analyzed independently by two trained observers. C2 internal height (C2InH), C2 isthmus height (C2IsH), and C2P width were measured. Kappa statistics for inter- and intraobserver reliability as well as for inter-software agreement were calculated. HRVA was defined as C2IsH of ≤ 5 mm and/or C2InH of ≤ 2 mm. Narrow C2P was defined as C2P width ≤ 4 mm. STROBE checklist was followed.ResultsAt least 1 HRVA was found in 25,3% (95% CI 21,1-29,8) of patients (16,7% of potential sites). At least 1 narrow C2P was seen in 36,8% (95% CI 32,1-41,7) of patients (23,8% of potential sites). Among those with HRVA, unilateral HRVA was present in 68,0% (95% CI 58,4-77,0), whereas bilateral HRVA in 32,0% (95% CI 23,0-41,6). No difference in terms of laterality (right or left) was seen neither for HRVA nor narrow C2P. Significant differences were found between females and males for all measurements. Each parameter showed either good or excellent inter- or intraobserver, and inter-software agreement coefficients. Conclusions HRVA and narrow C2P are common findings in Central-European population and should be appreciated at the planning stage before craniocervical instrumentation. Measurements can be consistently reproduced by various observers at varying intervals using different software.

Objective To evaluate the safety and accuracy of S2 alar-iliac (S2AI) screw placement guided by a three-dimensional (3D)-printed surgical guide template. Methods The data of 27 patients treated with S2AI screws were analyzed. S2AI surgical guide templates were designed and printed, and S2AI screw placement was completed intraoperatively with the guide templates. Postoperative computed tomography (CT) was performed to measure screw path parameters, namely, the sagittal angle (SA), the transverse angle (TA), the horizontal distance (HD) between the entry point of the screw and the median sacral crest, and the vertical distance (VD) between the entry point of the screw and the lower edge of the first posterior sacral foramen. Screw placement was graded according to the Oh grading criteria. Results A total of 54 S2AI screws were placed. The screw grades were as follows: 52 screws were considered grade 0, two were grade 1, none were grade 2, and none were grade 3. Thus, grade 0 accounted for 96.3% of the screws. When the preoperatively planned SA (32.3° ± 2.0°), TA (42.1° ± 3.9°), HD (5.1 ± 1.1) mm, and VD (19.0 ± 2.4) mm were compared with the corresponding postoperative SA (31.9° ± 3.8°), TA (42.5° ± 4.0°), HD (4.9 ± 1.1) mm, and VD (19.1 ± 2.3) mm, no significant differences were identified (P > 0.05). Conclusions S2AI screw placement assisted by a 3D-printed surgical guide is safe and accurate.

The occipital condyle (OC) screw is an alternative technique for occipitocervical fixation that is especially suitable for revision surgery in patients with Chiari malformation type I (CMI). This study aimed to investigate the feasibility and safety of this technique in patients with CMI. The CT data of 73 CMI patients and 73 healthy controls were retrospectively analyzed. The dimensions of OCs, including length, width, height, sagittal angle, and screw length, were measured in the axial, sagittal, and coronal planes using CT images. The OC available height was measured in the reconstructed oblique parasagittal plane of the trajectory. The mean length, width, and height of OCs in CMI patients were 17.79 ± 2.31 mm, 11.20 ± 1.28 mm, and 5.87 ± 1.29 mm, respectively. All OC dimensions were significantly smaller in CMI patients compared with healthy controls. The mean screw length and sagittal angle were 19.13 ± 1.97 mm and 33.94° ± 5.43°, respectively. The mean OC available height was 6.36 ± 1.59 mm. According to criteria based on OC available height and width, 52.1% (76/146) of OCs in CMI patients could safely accommodate a 3.5-mm-diameter screw. The OC screw is feasible in approximately half of OCs in CMI patients. Careful morphometric analyses and personalized surgical plans are necessary for the success of this operation in CMI patients.

Purpose Instrumentation in spinal revision surgery is considered challenging. Altered or missing anatomical landmarks hinder the surgeons' intraoperative orientation. In recent history, the importance of navigated approaches to spinal screw placement is constantly increasing. A growing number of medical centers have introduced intraoperative CT (iCT) navigation as a new clinical standard. In this study, we compare the accuracy of dorsal iCT-navigated instrumentation in revision surgery versus primary interventions. Methods Between September 2017 and January 2019, we prospectively analyzed a consecutive series of dorsal instrumentation using iCT. Patients with previous operative interventions in the relevant spinal segments were included in the revision group and compared with a previously assessed group of primary interventions (nonrevision group). Each screw was assessed individually by an independent observer, making use of a modified Gertzbein and Robbins classification. Results In this period, 39 patients were treated in the revision group with a total amount of 269 implanted screws. We achieved an overall accuracy of 95.91% compared with 95.12% in the nonrevision group (46 patients, 287 screws). We found no significant difference in accuracy between the two groups or any anatomical region of the spine. Conclusion In summary, iCT-navigated screw placement yields a good accuracy in spinal revision surgery, without significant difference to primary interventions.

Aim Guide wire displacement in spinal pedicle screw implantation was analyzed in order to reduce or avoid the occurrence of this phenomenon and to reduce the complications associated with robot-assisted pedicle screw implantation surgery. Material and methods From April 2017 to December 2019, a retrospective study was conducted with 398 patients who underwent robot-assisted spinal pedicle screw implantation. The causes of guide wire displacement in 60 punctures were analyzed. Results There were 2,408 robot-assisted wire punctures of the pedicle, of which 2,348 wire punctures were located well within the pedicle, and 60 wire displacements occurred during robot-assisted wire puncture, with a displacement rate of 2.49%. There was 1 case of thoracic segmental artery injury and 1 case of spinal cord incomplete injury. Conclusions As it is a rare phenomenon in robot-assisted spinal pedicle screw implantation, guide wire displacement should be avoided as much as possible to improve the accuracy of screw placement and reduce surgical complications during the operation.

Background and Objective Learning a new technique in neurosurgery is a big challenge especially for trainees. In recent years, simulations and simulators got into the focus as a teaching tool. Our objective is to propose a simulator for placement of cortical bone trajectory (CBT) screws to improve results and reduce complications.Methods We have created a platform consisting of a sawbone navigated with a 3D fluoroscope to familiarize our trainees and consultants with CBT technique and later implement it in our department. Objective Structured Assessment of Technical Skills (OSATS) and Physician Performance Diagnostic Inventory Scale (PPDI) were obtained before and after the use of the simulator by the five participants in the study. Patients who were operated on after the implementation of the technique were retrospectively reviewed.Results During the simulation, there were 4 cases of pedicle breach out of 24 screws inserted (16.6%). After having completed simulation, participants demonstrated an improvement in OSATS and PPDI (p = 0.039 and 0.042, respectively). Analyzing the answers to the different items of the tests, participants mainly improved in the knowledge (p = 0.038), the performance (p = 0.041), and understanding of the procedure (p = 0.034). In our retrospective series, eight patients with L4–L5 instability were operated on using CBT, improving their Oswestry Disability Index (ODI) score (preoperative ODI 58.5 [SD 16.7] vs. postoperative ODI 31 [SD 13.4]; p = 0.028). One intraoperative complication due to a dural tear was observed. In the follow-up, we found a case of pseudoarthrosis and a facet joint violation, but no other complications related to misplacement, pedicle fracture, or hardware failure.Conclusion The simulation we have created is useful for the implementation of CBT. In our study, consultants and trainees have valued very positively the learning obtained using the system. Moreover, simulation facilitated the learning of the technique and the understanding of surgical anatomy. We hope that simulation helps reducing complications in the future.

Objectives: This study aims to determine the secure location and angle of the most distal screw during posterior malleolar (PM) fracture fixation. Materials and methods: This prospective study was performed on September 15, 2019. Distal tibial concave articular depth and PM inclination angle were measured on 100 (50 male and 50 female) dry tibia bones using a digital caliper. A comparative analysis between male and female tibias was performed. Results: Anteroposterior width of male tibia (38.3±3.1 mm) was wider than female tibia (35.3±3.2 mm) (p

The objective of this study was to evaluate the ex vivo effect of cyclic loading on the stability of screws placed in locking plates used to bridge segmental bone defects. The primary interface stability was assessed using peak reverse torque. Eighteen, 8‐hole stainless‐steel 4.5 mm locking plates and 4.0‐mm self‐tapping locking‐head screws were used to stabilize 40‐mm segmental defects in goat tibiae. Treatment groups included control constructs without cyclic loading (n = 6) and constructs tested to 5000 (n = 6) and 10,000 cycles (n = 6) of 600 N compressive axial loading. The insertion of all screws was standardized to 400 N‐cm insertion torque. Peak reverse torque was measured immediately after screw placement (control), or after the completion of the respective loading cycles. The difference between treatment groups was compared using univariate analysis of variance. The analysis revealed a significant difference in peak reverse torque of the screws among the treatment groups (p = .000). The mean reverse torque values equaled 343.5 ± 18.3 N‐cm for non‐cycled controls, 303.3 ± 25.9 and 296.0 ± 42.9 N‐cm after 5000 and 10,000 cycles, respectively. Among all treatment groups, screws placed in the distal bone segment tended to have lesser peak reverse torque reduction than those placed in the proximal segment and the difference was proportional to the number of cycles (p = .562; p = .255; p = .013 in control, and after 5000 and 10,000 cycles, respectively). Cyclic loading may have a negative effect on the primary stability of screws placed in locking plate constructs used to bridge segmental bone defects and could contribute to the risk of screw loosening.

INTRODUCTION: Morphometric evaluation of the pedicle and isthmus of second cervical vertebra (C2) (Axis) is extremely vital before contemplating any surgical stabilization involving the Craniovertebral region, in view of its proximity to the vertebral artery and the cervical nerve root. The dimensions of pedicles and isthmuses in C2 vary between individuals and there is paucity of data in the Indian population. This study strives to measure the average pedicle and isthmus dimensions in a sample of population, which would enable selection of screws with safest diameters to be used in C2; thereby avoiding injury to adjacent neurovascular structures. MATERIALS AND METHODS: One Hundred patients in the age group between 18 and 70 years who underwent CT scan of head and neck region were included in the study. The aim of this study was to assess the anatomic suitability of transarticular and pedicle screw placement in Axis vertebrae of Indian population and determine the maximum safe diameter for screw placement. The following parameters were measured in millimeters: Pedicle width, Pedicle angle, Internal height and Isthmic height. RESULTS: The Mean maximum diameter of potential pedicle screw was 4.99 ± 1.1 mm for the right side with the left side being slightly wider at 5.20 ± 1.16 mm. Twenty eight (28%; 56 out of 200 pedicles) had a measurement

OBJECTIVE To determine the influence of a purpose-built frame on the accuracy of screw placement during computer-assisted orthopedic surgery (CAOS) of the equine extremity. STUDY DESIGN Experimental cadaveric study. SAMPLE POPULATION Twenty-four paired equine cadaveric limbs obtained from seven horses. METHODS Three 4.5-mm cortex screws were inserted in lag technique in three different planes of orientation in the proximal phalanx (P1) by means of CAOS. In the study group (n = 12 limbs), the tracker was anchored on a purpose-built frame designed to stabilize the extremity. In the control group (n = 12 limbs), a conventional tracker array was used that was anchored directly on P1. The stability of both tracker arrays was assessed during the procedure by using fiducial markers. After screw placement, preoperative and postoperative computed tomographic images were assessed to measure surgical accuracy aberrations (SAA) between the planned and achieved screw position. Descriptive statistics and repeated-measures analysis of variance were performed to compare SAA measurements between the study and control group. RESULTS Both tracker arrays remained consistently stable in all specimens. Mean overall SAA of screw insertion were lower in the study group (0.7 mm; median, 0.5; range 0-3.4) than in the control group (1.2 mm; median, 0.9; range, 0-4.2 mm). CONCLUSION The mean SAA achieved in cortex screw placement using CAOS lies within the range of approximately 1 mm. The use of a purpose-built frame avoided additional drilling of the target bone and improved surgical accuracy compared with the conventional tracker array. CLINICAL SIGNIFICANCE The purpose-built frame described in this report can be used to facilitate CAOS in equine orthopedics without compromising surgical accuracy.

Pelvic fractures are often caused by high-energy injuries and accompanied by hemodynamic instability. Traditional open surgery has a large amount of bleeding, which is not suitable for patients with acute pelvic fracture. Navigation-guided, percutaneous puncture-screw implantation has gradually become a preferred procedure due to its advantages, which include less trauma, faster recovery times, and less bleeding. However, due to the complexity of pelvic anatomy, doctors often encounter some problems when using navigation to treat pelvic fractures. This article reviews the indications, contraindications, surgical procedures, and related complications of this procedure for the treatment of sacral fractures, sacroiliac joint injuries, pelvic ring injuries, and acetabular fractures. We also analyze the causes of inaccurate screw placement. Percutaneous screw placement under navigational guidance has the advantages of high accuracy, low incidence of complications and small soft-tissue damage, minimal blood loss, short hospital stays, and quick recovery. There is no difference in the incidence of complications between surgeries performed by new doctors and experienced ones. However, computer navigation technology requires extensive training, and attention should be given to avoid complications such as screw misplacement, intestinal injury, and serious blood vessel and nerve injuries caused by navigational drift.

Background/Objective Atlantoaxial fusion procedures may be difficult in situations such as high-riding vertebral artery, a narrow C2 pedicle, and the presence of ponticulus posticus–arcuate foramen. With respect to vertebral artery (VA) anomalies, persistent first intersegmental artery, extracranial origin of the posterior inferior cerebellar artery at the C1–C2 level, and fenestration of the VA are all major risk factors for VA injury in C1–C2 fusion surgeries. Methods To safeguard the VA, we designed the unilateral fusion procedure (all screws lie in the ipsilateral side, either the right side or left side): a unilateral transarticular screw combined with an ipsilateral-side C1 posterior arch screw and a C2 laminar screw (LS), with both C1–C2 screws inserted from opposite side, although the trajectory will be on the same side. In addition to atlantoaxial stabilization with screws and rod, autograft bony fusion was performed on the same side as modified Brook's procedure and augmented with sublaminar tapping. Results We present a series of 3 cases operated for odontoid fracture with associated high risk for fusion on one side alone. The fact that the chance of VA injury is high in transarticular screw, in lateral mass screw, less in pars screw, and pedicle screw is well known. Alternate screw placement to avoid VA injury would be a posterior arch screw for C1 and laminar screw for C2, which was adopted in our technique. Conclusions We combined a unilateral transarticular screw and modified Brook's procedure with sublaminar tapping for additional augmentation of fusion. We would like to highlight this C1 posterior arch screw as an alternative procedure for atlantoaxial fusion.

Many patients receive magnetic resonance (MR) and computed tomography (CT) scans post-operatively to review screw placement. Traditionally, CT is diagnostic but as metal artefact reduction sequences are advancing in MR, the necessity for both MR and CT scans is questionable. The objective is to establish the statistical agreeability of MR and CT for evaluation of adequate screw placement in posterior lumbar interbody fusion. This opportunistic retrospective study of 58 patients investigated 297 images of 296 implanted screws. Post-operative MR and CT images were scrutinised for depiction of lumbar pedicle screw position using a 5-point scale. Kappa value for statistical agreeability tested MR against CT. The 297 images of screws resulted in strong to near-perfect agreement between MR and CT (n = 297 k = 0.8042 p

Objective The clinical outcomes, radiological parameters, complication rate and the cost of implants in two-level ACDF with and without screws in the intervening segment were compared. Methods A retrospective study of 68 patients who underwent 2-level ACDF from January 2014 to June 2016 was performed. The patients were divided into two groups: ACDF with screws in the intervening vertebra and those without screws in the intervening vertebra. Perioperative factors, clinical outcomes, postoperative complications, radiological parameters, and cost of the implants were evaluated in both groups. Results No statistical differences in clinical outcomes, operative blood loss, hospital stay, restoration of cervical lordosis or segment height, postoperative complications, and fusion rate were found between the ACDF (middle vertebra with screw) and ACDF (middle vertebra without screw) groups (P > 0.05). But the operative time of added screw placement and cost of implants in the ACDF (middle vertebra without screw) group were significantly less than the ACDF (middle vertebra with screw) group (P Conclusion Two kinds of screw placement with ACDF were found to be similar in terms of clinical outcomes. However, ACDF (middle vertebra without screw) was found to be superior to ACDF (middle vertebra with screw) in terms of the screw placement time and cost of implants.

Objective Patients who undergo decompression surgery for Chiari malformation frequently require occipitocervical fixation. This is typically performed with occipital plates, which may cause intracranial injuries due to multiple fixation points. We undertook this study to assess the feasibility of occipital condyle (OC) screw placement as an alternative method of occipitocervical fixation in this patient population. Methods Using a cadaveric model with navigational assistance, we performed the complete surgical procedure for occipitocervical fixation with OC screws. We then performed a morphometric analysis using measurements from computed tomography scans of 49 patients (32 adult, 17 pediatric) who had undergone occipitocervical fusion with instrumentation following decompression surgery for Chiari malformation. Bilateral morphometric data were analyzed for the adult and pediatric subgroups separately, as well as for the overall group. Results The surgical procedure was successfully performed in the cadaveric model, demonstrating the feasibility of the proposed method. Ninety-eight OCs were studied in the morphometric analysis, and 80 (81.6%) met our eligibility criteria for OC screw placement. However, in 14.1% of adult OCs and 26.5% of pediatric OCs studied, placement of condylar screws would have been challenging or unsafe, according to our criteria. Conclusions Our findings suggest that OC screws provide a useful option for occipitocervical fixation in a substantial proportion of patients with Chiari malformation. However, rigorous preoperative analysis would be essential to identify appropriate candidates for this technique and exclude those in whom it should not be attempted. Additional study is warranted.

Femoroacetabular impingement syndrome caused by slipped capital femoral epiphysis (SCFE) can be successfully treated arthroscopically and with the minimally invasive, outside-in surgical technique. The advantages of the technique are that the residual cam-type deformity caused by the slippage can be corrected and reconstructed reliably and reproducibly before distracting the hip joint; and radiation with fluoroscopy is used for only definitive reduction and reconstruction, which is obtained with cannulated screws. In addition, this safe technique allows distraction of the hip after screw placement, without affecting the reconstruction, to address labral tears and chondrolabral delaminations caused by the impingement.

Background The subcutaneous screw rod system, commonly known as the internal pelvic fixator (INFIX), is useful in managing unstable pelvic ring fractures. Conventional INFIX and transiliac–transsacral (TITS) screw techniques are performed using C-arm fluoroscopy. There have been problems with medical exposure and screw insertion accuracy with these techniques. This work describes new INFIX and TITS techniques using intraoperative computed tomography (CT) navigation and C-arm fluoroscopy for pelvic ring fracture. Methods A typical case is presented in this study. An 86-year-old woman suffered from an unstable pelvic ring fracture due to a fall from a height. INFIX and TITS screw fixation with intraoperative CT navigation were selected to optimize surgical invasiveness and proper implant placement. Results The patient was placed in a supine position on a Jackson table. An intraoperative CT navigation was imaged, and screws were inserted under the navigation. Postoperative X-rays and CT confirmed that the screw was inserted correctly. This technique was less invasive to the patient and had little radiation exposure to the surgeon. Rehabilitation of walking practice was started early after the surgery, and she was able to walk with the assistance of a walker by the time of transfer. Conclusions The technique employed in our case study has the cumulative advantages of safety, accuracy, and reduced radiation exposure, together with the inherent advantages of functional outcomes of previously reported INFIX and TITS screw techniques. Further experience with this approach will refine this technique to overcome its limitations and facilitate its wider use.

Since pseudoarthrosis or screw loosening is frequently seen in lumbosacral stabilizations ending in S1, S2 screws are used more frequently to support S1 screws. This study aims to describe a new screw placement technique and location from S2. Revision surgery was applied to the patient who had previously undergone surgery with the rigid instrumentation system and encountered pseudoarthrosis during the follow-up period. Instrumentation was performed from S2 to the promontorium. The patient’s chronic low back pain arising due to pseudoarthrosis was reduced and a strong lumbosacral dynamic instrumentation was performed to the patient. Dual screw placement from S2 and/or screw placement in the S2-promontorium direction is a new alternative to provide a powerful instrumentation.

This study aimed at quantifying trabecular volumetric bone mineral density (vBMD) at the external occipital protuberance (EOP) and the upper cervical spine. A retrospective review of patients who underwent non-contrast enhanced computed tomography of the cervical spine that included the occipital bone up to the EOP between 2007 and 2020 was conducted. Measurements of trabecular vBMD were performed in the occipital midline area, with the region of interest extending 4.5 mm above and below the center of the EOP, as well as the C1 lateral masses and the C2 vertebral body using asynchronous quantitative computed tomography. Eighty-six patients (female, 37.2%) were included for analysis. The patient population was 81.4% Caucasian with a mean ± SD age of 62.3 ± 13.1 years. Total bone thickness at the EOP was 16.7 ± 3.4 mm, with a ratio of trabecular to total bone thickness of 0.44. Trabecular vBMD (mean ± SD) was significantly higher at the EOP than at C1 and C2 (EOP = 612.3 ± 145.8 mg/cm3 , C1 average = 290.3 ± 66.5 mg/cm3 , C2 = 305.8 ± 78.8 mg/cm3 ; p 65 years of age, cervical vBMD was significantly lower, but remained high at the EOP. Clinical significance: Trabecular vBMD at the EOP is significantly higher than at the upper cervical vertebrae and remains high in older populations. Together with morphological information about the occipital bone, these results might be helpful for occipitocervical fixation when deciding about uni- or bicortical screw placement at the EOP.

Background Infra-acetabular screws enhance the fixation strength in acetabular fractures with separation of both columns. Placement without iatrogenic femoral head violation is challenging. Purpose To assess the impact of the acetabular configuration, the patients’ age and gender on safe infra-acetabulum screw insertion. Methods In 112 patients (69 females; mean age: 34 years, range 17–88; n = 200 hips), the lateral center–edge angle (LCE) was measured on radiographs. Using corresponding axial CT scans the residual distance from (the lateral border) of the screw to (the medial border of) the femoral head (“Screw-to-Femoral Head distance”; “RD_SFH”) was determined. Statistical analysis was carried out using linear regression, multiple linear regression and normal distribution estimation. Results The mean (range) LCE angle was 30° (7°–51°) and the mean (range) “RD_SFH” was 5 mm (1–14 mm). The linear regression model shows a significant linear relation between LCE and “RD_SFH” with a slope parameter of − 0.15 (p value p value 0.85). Compared to male patients, in females, the intercept is 4.62 mm (p value 0.0005) less, the slope parameter is 0.09 (p value 0.029) larger. Conclusion The virtual possibility to place an infra-acetabular screw was given in all patients. An increasing depth of the acetabulum correlated with a decrease in residual distances. As hip joint cartilage thickness was not considered in measurements, intraoperative rule-out of screw mispositioning especially in deep acetabular sockets and females is still of utmost importance.

Development of stereotactic neurosurgery occurred due to the special area of interest within the neurosurgery, the necessity for precise targeting within the skull, and the specificity of the technique demanding superior precision. Number of technological developments and improvements, especially in pre and intraoperative imaging and guidance, as well as microscopy brought neurosurgeons to their skill limits. Thus, robotic-assisted surgery provided better posture, visualization, precision, localization and accuracy. In recent decades, robotic neurosurgery and robot-assisted neurosurgery have been developed and strengthened within it, which, in addition to the advantages of an experienced clinician, benefits from significant advantages of robots such as better preoperative planning, non-fatigue, steady motion with limitless reproducibility, superior precision, localization, and accuracy, etc. The growing area expands to spinal neurosurgery where it is mostly used for precise screw placement reducing length of the procedure, complications, and radiation exposure. Hereby, we present a review of robotic systems used nowadays in stereotactic and spinal neurosurgery.

Shao-Jie Zhang,1,2,&ast; Kun Li,2,3,&ast; Zhi-Jun Li,2,3 Xing Wang,2,3 Jia-Hui Dong,4 Jian Wang,2 Jie Chen,2 Xing-Yue Qu,2 Zi-Yu Li,2 Yu-Hang Liu2 1School of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, People’s Republic of China; 2Department of Human Anatomy, Inner Mongolia Medical University, Hohhot, People’s Republic of China; 3Digital Medical Center, Inner Mongolia Medical University, Hohhot, People’s Republic of China; 4The First Clinical Medical College, Inner Mongolia Medical University, Hohhot, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Zhi-Jun LiDepartment of Human Anatomy, Inner Mongolia Medical University, Hohhot, People’s Republic of ChinaTel +86 471-6636945Email zjl06_master@126.comObjective: This study aimed to investigate the safety of clival screw placement in children aged 1– 6 years.Methods: The cranial computed tomography data of 92 children aged 1– 6 years were divided into three groups, according to age, for three-dimensional reconstruction. Three clival screw placement points were defined: (1) median point A at the middle and upper third of the tripartite distance from the spheno-occipital synchondrosis to the base of the skull; (2, 3) critical points B and C on the horizontal line with point A, where the screw placement passage was parallel to the sagittal plane. Parameters such as the passage length and angle were measured for horizontal, vertical facial, and extreme screw placement.Results: The length parameters of the clival screw placement increased with age, and the screw passage length was the shortest for the vertical facial type in each age group. There were significant differences in all three groups between the length of screw placement in the vertical bone surface, the length of screw placement in the horizontal direction, and the length of screw placement on the limit at points A, B, and C (P < 0.05); the length of screw placement on the vertical bone surface was the shortest. There was no significant difference between the horizontal screw length at point A and the extreme screw length (P > 0.05). The difference between the horizontal screw length and the extreme screw length in the groups aged 1– 2 years and 5– 6 years was statistically significant (P < 0.05), and the horizontal screw length was longer.Conclusion: The cranial slope of children aged 1– 6 years has the morphological basis for the placement of 3.5 mm screws, and each placement point has a safe angle range for screw placement.Keywords: children, craniocervical junction region, clivus, internal screw fixation, spiral computed tomography scan

Introduction: Current high-accuracy image-guided systems for otologic surgery use fiducial screws for patient-to-image registration. Thus far, these systems have only been used in adults, and the safety and efficacy of the fiducial screw placement has not yet been investigated in the pediatric population.Materials and Methods: In a retrospective study, CT image data of the temporal region from 11 subjects meeting inclusion criteria (8–48 months at the time of surgery) were selected, resulting in n = 20 sides. These datasets were investigated with respect to screw stability efficacy in terms of the cortical layer thickness, and safety in terms of the distance of potential fiducial screws to the dura mater or venous sinuses. All of these results are presented as distributions, thickness color maps, and with descriptive statistics. Seven regions within the temporal bone were analyzed individually. In addition, four fiducial screws per case with 4 mm thread-length were placed in an additively manufactured model according to the guidelines for robotic cochlear implantation surgery. For all these screws, the minimal distance to the dura mater or venous sinuses was measured, or if applicable how much they penetrated these structures.Results: The cortical layer has been found to be mostly between 0.7–3.3 mm thick (from the 5th to the 95th percentile), while even thinner areas exist. The distance from the surface of the temporal bone to the dura mater or the venous sinuses varied considerably between the subjects and ranged mostly from 1.1–9.3 mm (from the 5th to the 95th percentile). From all 80 placed fiducial screws of 4 mm thread length in the pediatric subject younger than two years old, 22 touched or penetrated either the dura or the sigmoid sinus. The best regions for fiducial placement would be the mastoid area and along the petrous pyramid in terms of safety. In terms of efficacy, the parietal followed by the petrous pyramid, and retrosigmoid regions are most suited.Conclusion: The current fiducial screws and the screw placement guidelines for adults are insufficiently safe or effective for pediatric patients.