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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.

Introduction C-expanders are tissue- and bone-borne maxillary expanders that are anchored by 6 orthodontic miniscrews, 3 on each side of the palate. The purpose of the study was to investigate the effect of C-expanders on the circummaxillary sutures and bucco-palatal axis of teeth in 3-dimensional finite element analyses when anchor screw vectors are different. Methods Five expansion models were studied on the basis of the vertical positions of anchor screws on the palate. Anchor screws for models A, B, and C were placed symmetrically at 4 mm, 7 mm, and 15 mm below the cementoenamel junction (CEJ), respectively. Anchor screws for models D and E were placed asymmetrically at 4 mm and 15 mm below CEJ and 7 mm and 15 mm below CEJ, respectively. Stress, displacement, and angular changes of the bone and teeth were measured in elastoplastic behavior models using a static-nonlinear simulation in an implicit method. Results Symmetrical and asymmetrical anchor screw placement with different vertical vectors were compared using finite element analyses on 5 models. Conclusions Using different vectors of anchor screws for C-expanders does change the pattern of palatal expansion (null hypothesis was rejected). The current investigation presents a promising future of controlled asymmetric skeletal maxillary expansion when asymmetric maxillary architecture needs to be corrected for successful orthodontic outcomes without involving orthognathic surgeries.

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.