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Background: Traditional surgical treatment for symptomatic cervical degenerative disc disease is anterior cervical discectomy and fusion (ACDF), yet the increased risk of adjacent segment degeneration (ASD) requiring additional surgery exists and may result in limiting long-term surgical success when it occurs. Disc arthroplasty can preserve or restore physiologic range of motion (ROM), decreasing adjacent level stress and subsequent surgery. For patients with multilevel pathology requiring at least a 1-level fusion, interest is growing in anterior cervical hybrid (ACH) surgery as a partial motion-preserving procedure to decrease the adjacent level burden. This radiographic study compares postoperative superior adjacent segment motion between ACH and ACDF. Secondarily, total global motion, construct motion, inferior adjacent segment motion, and sagittal alignment parameters were compared., Methods: This is a single-center, multi-surgeon, retrospective cohort study of 2- and 3-level ACH and ACDF cases between 2013 and 2021. Degrees of motion were analyzed on flexion/extension views using Cobb angles to measure global (C2-C7) construct and adjacent segment lordosis. Neutral lateral X-rays were analyzed for alignment parameters, including global lordosis, cervical sagittal vertical axis (cSVA), and T1 slope (T1S). Differences were determined by independent t-test and Fisher's exact test., Results: Of 100 patients, 38% were 2-level cases (47% ACH, 53% ACDF) and 62% were 3-level cases: (52% ACH, 48% ACDF). Postoperatively, superior adjacent segment motion increased with ACDF and decreased with ACH (-1.3°±5.3° ACH, 1.6°±4.6° ACDF, P=0.005). Postoperatively, the ACH group had greater ROM across the construct (16.3°±8.7° ACH, 4.7°±3.3° ACDF, P<0.001) and total global ROM (38.0°±12.8° ACH, 28.0°±11.1° ACDF, P<0.001). ACH resulted in a significant reduction of motion loss across the construct (-10.0°±11.7° ACH, -18.1°±10.8° ACDF, P<0.001). Postoperative alignment restoration was similar between both cohorts (-2.61°±8.36° ACH, 0.04°±12.24° ACDF, P=0.21)., Conclusions: Compared to ACDF, hybrid constructs partially preserved motion across operative levels and had greater postoperative global ROM without increasing superior adjacent segment mobility or sacrificing alignment restoration. This supports the consideration of ACH in patients with multilevel degenerative cervical pathology requiring at least a 1-level fusion and suggests a propensity for long-term success by reducing the superior adjacent segment burden., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-23-135/coif). L.D.O. and R.T.R. received institutional research support from Medtronic and Innovasis. C.R.G. serves on an advisory board for Stryker/K2M, Medtronic, and Augmedics. C.R.G. reports royalties and consulting fees from Stryker/K2M and Medtronic; institutional educational research support from Medtronic; owns stock in Audmedics and NSite. E.J. reports consulting fees from Stryker, Medtronic, and Innovasis. C.M.H. reports personal fees from Medtronic, Globus Medical, Spineart, and Innovasis. The other authors have no conflicts of interest to declare., (2024 Journal of Spine Surgery. All rights reserved.)

Study Design: Prospective cohort study., Objectives: In spine surgery, accurate screw guidance is critical to achieving satisfactory fixation. Augmented reality (AR) is a novel technology to assist in screw placement and has shown promising results in early studies. This study aims to provide our early experience evaluating safety and efficacy with an Food and Drug Administration-approved head-mounted (head-mounted device augmented reality (HMD-AR)) device., Methods: Consecutive adult patients undergoing AR-assisted thoracolumbar fusion between October 2020 and August 2021 with 2 -week follow-up were included. Preoperative, intraoperative, and postoperative data were collected to include demographics, complications, revision surgeries, and AR performance. Intraoperative 3D imaging was used to assess screw accuracy using the Gertzbein-Robbins (G-R) grading scale., Results: Thirty-two patients (40.6% male) were included with a total of 222 screws executed using HMD-AR. Intraoperatively, 4 (1.8%) were deemed misplaced and revised using AR or freehand. The remaining 218 (98.2%) screws were placed accurately. There were no intraoperative adverse events or complications, and AR was not abandoned in any case. Of the 208 AR-placed screws with 3D imaging confirmation, 97.1% were considered clinically accurate (91.8% Grade A, 5.3% Grade B). There were no early postoperative surgical complications or revision surgeries during the 2 -week follow-up., Conclusions: This early experience study reports an overall G-R accuracy of 97.1% across 218 AR-guided screws with no intra or early postoperative complications. This shows that HMD-AR-assisted spine surgery is a safe and accurate tool for pedicle, cortical, and pelvic fixation. Larger studies are needed to continue to support this compelling evolution in spine surgery.

Study Design: Retrospective observational cohort., Objectives: We sought to evaluate the impact of ESR on in-hospital and 90-day postoperative opioid consumption, length of stay, urinary catheter removal and postoperative ambulation after lumbar fusion for degenerative conditions., Methods: We evaluated patients undergoing lumbar fusion surgery at a single, multi-surgeon center in the transition period prior to (N = 174) and after (N = 116) adoption of ESR, comparing in-hospital and 90-day postoperative opioid consumption. Regression analysis was used to control for confounders. Secondary analysis was preformed to evaluate the association between ESR and length of stay, urinary catheter removal and ambulation after surgery., Results: Mean age study participants was 52.6 years with 62 (47%) females. Demographic characteristics were similar between the Pre-ESR and ESR groups. ESR patients had better 3-month pain scores, ambulated earlier, had urinary catheters removed earlier and decreased in-hospital opioid consumption compared to Pre-ESR patients. There was no difference in 90-day opioid consumption between the 2 groups. Regression analysis showed that ESR was strongly associated with in-hospital opioid consumption, accounting for 30% of the variability in Morphine Milligram Equivalents (MME). In-hospital opioid consumption was also associated with preoperative pain scores, number of surgical levels, and insurance type (private vs government). Pre-op pain sores were associated with 90-day opioid consumption. Secondary analysis showed that ESR was associated with a shorter length of stay and earlier ambulation., Conclusions: This study showed ESR has the potential to improve recovery after lumbar fusion for degenerative conditions with reduced in-hospital opioid consumption and improved postoperative pain scores.

Introduction: Degenerative disc disease is a common cause of chronic low back pain. Surgical intervention is an invasive treatment associated with high costs. There is growing interest in regenerative medicine as a less invasive but direct disc treatment for chronic discogenic low back pain., Objective: To evaluate clinical improvement of primary discogenic low back pain with intradiscal injection of autologous bone marrow aspirate concentrate (BMAC). Study Design . Prospective cohort study. Setting . Single, multiphysician center. Patients . 32 adult patients undergoing intradiscal injection of autologous BMAC for the treatment of primary discogenic low back pain. Interventions . Intradiscal injection of autologous BMAC. Main Outcome Measures . Primary outcome measure is visual analog back pain scale (VAS back pain). Secondary outcome measures include ODI, VAS leg pain, and EQ-5D-5L scores. Outcomes were compared from baseline to 1 year., Results: Thirty-two patients (56.3% male) with a mean age of 45.9 years were enrolled, giving 92 treated levels. Mean VAS back and leg pain scores improved from 5.4 to 3.0 ( p < 0.001) and 2.8 to 1.3 ( p = 0.005), respectively. Mean ODI scores decreased from 33.5 to 21.1 ( p < 0.001), and EQ-5D-5L scores improved from 0.69 to 0.78 ( p = 0.001). Using established MCID values, 59.4% had clinically significant improvement in VAS back pain, 43.8% in VAS leg pain, and 56.3% in ODI scores., Conclusion: Intradiscal injection of autologous BMAC significantly improved low back pain, disability, and quality of life at one year. This study suggests that intradiscal BMAC has the potential to be an effective nonsurgical treatment for chronic discogenic low back pain., Competing Interests: Dr. Haines reports personal fees from Medtronic, personal fees from Globus Medical, personal fees from Spineart, and personal fees from Innovasis, outside the submitted work. Dr. Good reports personal fees from Stryker/K2M, personal fees from Medtronic, personal fees from Augmedics, and personal fees from NSite, outside the submitted work. Dr. Jazini is a consultant with Stryker, Medtronic, and Innovasis, outside the submitted the work. There are no other conflicts of interest to declare for the remaining authors., (Copyright © 2022 Colin M. Haines et al.)

Background: The opioid epidemic in the US has led prescribers to reevaluate postoperative pain control particularly in the field of spine surgery, where postoperative analgesia requirements and consumption have historically been high. There is a need to mitigate the quantity of unused pills after surgery by adjusting prescribing practices. Achieving the balance of pain control after surgery without overprescribing opioids may be accomplished by developing a modified approach to prescribing practices; however, there is a need to first understand the opioid requirements of the modern spine surgery patient with respect to their elective spine surgery. Therefore, the primary aim of this study was to determine the percentage of opioids not utilized at 90-days after elective spine surgery. Secondary aims were to identify differences in the percentage of unused opioids between surgical subgroups and preoperative opioid status, to determine factors associated with opioid utilization, and to estimate the distribution of opioids consumed to control pain up to the 90th percentile in each surgical subgroup., Methods: In this prospective, observational cohort study, adults undergoing elective spine surgery at a multi-surgeon, single center were prospectively enrolled and divided into subgroups: anterior cervical, lumbar decompression, and short-segment lumbar fusion. Prescribed MMEs were identified from prescriptions, consumed MMEs were obtained from pill counts, and the percent leftover was calculated. Distributions of MMEs consumed were analyzed to compare utilization between preoperative opioid users or non-users within each surgical subgroup., Results: Of 117 patients, 41.9% were preoperative opioid users. The percentage of unused opioids by surgical subgroup was: 45.4% cervical, 57.3% lumbar decompression, and 37.4% lumbar fusion ( p =0.066). The percentage of unused opioids by preoperative opioid exposure was greater in the opioid non-users (58.0%) than users (28.4%, p <0.001)). Regression analysis showed that surgical subgroup and preoperative opioid exposure were associated with leftover opioids., Conclusions: At 90-days, the percentage of unused opioids was over 45% in this cohort of elective spine surgery patients and was nearly double in the group without preoperative opioid exposure. These results suggest the modern elective spine surgery patient is using less opioids than prescribed, supporting the conclusion that the number of MMEs prescribed can be reduced to minimize quantities of leftover pills available for diversion, without sacrificing the priority of appropriate postoperative pain control., Competing Interests: None, (© 2022 The Author(s).)

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., (© 2021. The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.)

Objective: The analysis of sagittal alignment by measuring spinopelvic parameters has been widely adopted among spine surgeons globally, and sagittal imbalance is a well-documented cause of poor quality of life. These measurements are time-consuming but necessary to make, which creates a growing need for an automated analysis tool that measures spinopelvic parameters with speed, precision, and reproducibility without relying on user input. This study introduces and evaluates an algorithm based on artificial intelligence (AI) that fully automatically measures spinopelvic parameters., Methods: Two hundred lateral lumbar radiographs (pre- and postoperative images from 100 patients undergoing lumbar fusion) were retrospectively analyzed by board-certified spine surgeons who digitally measured lumbar lordosis, pelvic incidence, pelvic tilt, and sacral slope. The novel AI algorithm was also used to measure the same parameters. To evaluate the agreement between human and AI-automated measurements, the mean error (95% CI, SD) was calculated and interrater reliability was assessed using the 2-way random single-measure intraclass correlation coefficient (ICC). ICC values larger than 0.75 were considered excellent., Results: The AI algorithm determined all parameters in 98% of preoperative and in 95% of postoperative images with excellent ICC values (preoperative range 0.85-0.92, postoperative range 0.81-0.87). The mean errors were smallest for pelvic incidence both pre- and postoperatively (preoperatively -0.5° [95% CI -1.5° to 0.6°] and postoperatively 0.0° [95% CI -1.1° to 1.2°]) and largest preoperatively for sacral slope (-2.2° [95% CI -3.0° to -1.5°]) and postoperatively for lumbar lordosis (3.8° [95% CI 2.5° to 5.0°])., Conclusions: Advancements in AI translate to the arena of medical imaging analysis. This method of measuring spinopelvic parameters on spine radiographs has excellent reliability comparable to expert human raters. This application allows users to accurately obtain critical spinopelvic measurements automatically, which can be applied to clinical practice. This solution can assist physicians by saving time in routine work and by avoiding error-prone manual measurements.

Background: Although a growing amount of literature that suggests robots are safe and can achieve comparable outcomes to conventional techniques, much of this literature is limited by small sample sizes and single-surgeon or single center series. Furthermore, it is unclear what the impact of robotic technology has made on operative and clinical outcomes over time. This is the first and largest multicenter study to examine the trends in outcomes and complications after robot-assisted spine surgery over a 5-year period., Methods: Adult (≥18 years old) patients who underwent spine surgery with robot-assistance between 2015 and 2019 at four unique spine centers. The robotic systems used included the Mazor Renaissance, Mazor X, and Mazor Stealth Edition. Patients with incomplete data were excluded from this study. The minimum follow-up was 90 days., Results: A total of 722 adult patients were included (117 Renaissance, 477 X, 128 Stealth). Most patient and operative factors (e.g., sex, tobacco status, total instrumented levels, and pelvic fixation,) were similar across the years. Mean ± standard deviation Charlson comorbidity index (CCI) was 1.5±1.5. The most commonly reported diagnoses included high grade spondylolisthesis (40.6%), degenerative disc disease (18.4%), and degenerative scoliosis (17.6%). Mean (standard deviation) number of instrumented levels was 3.8±3.4. From 2015 to 2019, average robot time per screw improved from 7.2 to 5.5 minutes (P=0.004, R 2 =0.649). Average fluoroscopy time per screw improved from 15.2 to 9.4 seconds (P=0.002). Rates of both intraoperative screw exchange for misplaced screw (2015-2016: 2.7%, 2019: 0.8%, P=0.0115, R 2 =0.1316) and robot abandonment (2015-2016: 7.1%, 2019: 1.1%, P=0.011, R 2 =0.215) improved significantly over time. The incidence of other intraoperative complications (e.g., dural tear, loss of motor/sensory function, blood transfusion) remained consistently low, but similar throughout the years. The length of stay (LOS) decreased by nearly 1 day from 2015 to 2019 (P=0.007, R 2 =0.779). 90-day reoperation rates did not change significantly., Conclusions: At four institutions among seven surgeons, we demonstrate robot screw accuracy, reliability, operative efficiency, and radiation exposure improved significantly from 2015 to 2019. 90-day complication rates remained low and LOS decreased significantly with time. These findings further validate continued usage of robot-assisted spine surgery and the path toward improved value-based care., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-21-102/coif). SZ serves as an unpaid editorial board member of Journal of Spine Surgery. EJ reports consulting fees from Stryker, Medtronic, and Innovasis outside the submitted work. CH reports personal fees from Medtronic, Globus Medical, Spineart, and Innovasis outside the submitted work. CRG reports royalties from Stryker/K2M and Medtronic; consulting fees from Stryker/K2M, Medtronic; educational grant support from Medtronic, is on an advisory board for Stryker/K2M, Medtronic, and Augmedics, and owns stock in Augmedics and NSite. The other authors have no conflicts of interest to declare., (2022 Journal of Spine Surgery. All rights reserved.)

Purpose: Retrospective observational cohort study of primary adult spinal deformity (ASD) surgery during the transitional period prior to and after the implementation of Enhanced Surgical Recovery (ESR) at a single center. We sought to determine if ESR reduces in-hospital and 90-day post-operative opioid consumption for ASD surgery., Methods: We evaluated patients undergoing primary ASD surgery in the transition period prior to (N = 29) and after (N = 56) adoption of ESR, comparing in-hospital and 90-day post-operative opioid consumption. Regression analysis was used to control for confounders including age, number of surgical levels, surgical approach, staged vs same-day surgery, insurance type and pre-op opioid use., Results: Mean age of the cohort was 53 years with 57 (60%) females. Regression analysis showed that pre-operative opioid use and number of levels fused were associated with higher in-hospital and 90-day post-operative opioid consumption, while use of ESR was associated with lower in-hospital and 90-day post-operative opioid consumption. Secondary analysis showed that patients on ESR ambulated earlier (0.6 days vs 1.1, p = 0.028) and had their urinary catheter removed earlier (2.7 days vs 3.9, p = 0.006) compared to non-ESR patients., Conclusions: ESR was associated with a significantly decreased in-hospital and 90-day post-operative opioid consumption and earlier mobilization with earlier urinary catheter removal in patients undergoing primary ASD surgery. These results demonstrate ESR's potential to improve outcomes in ASD perioperative care., Level of Evidence: 3., (© 2021. The Author(s), under exclusive licence to Scoliosis Research Society.)

Study Design: Multicenter cohort., Objective: To compare the robot time/screw, radiation exposure, robot abandonment, screw accuracy, and 90-day outcomes between robot-assisted percutaneous and robot-assisted open approach for short lumbar fusion (1- and 2-level)., Summary of Background Data: There is conflicting literature on the superiority of robot-assisted minimally invasive spine surgery to open techniques. A large, multicenter study is needed to further elucidate the outcomes and complications between these two approaches., Methods: We included adult patients (≥18 yrs old) who underwent robot-assisted short lumbar fusion surgery from 2015 to 2019 at four independent institutions. A propensity score matching algorithm was employed to control for the potential selection bias between percutaneous and open surgery. The minimum follow-up was 90 days after the index surgery., Results: After propensity score matching, 310 patients remained. The mean (standard deviation) Charlson comorbidity index was 1.6 (1.5) and 53% of patients were female. The most common diagnoses included high-grade spondylolisthesis (grade >2) (48%), degenerative disc disease (22%), and spinal stenosis (25%), and the mean number of instrumented levels was 1.5(0.5). The operative time was longer in the open (198 min) versus the percutaneous group (167 min, P value = 0.007). However, the robot time/screw was similar between cohorts (P value > 0.05). The fluoroscopy time/ screw for percutaneous (14.4 s) was longer than the open group (10.1 s, P value = 0.021). The rates for screw exchange and robot abandonment were similar between groups (P value > 0.05). The estimated blood loss (open: 146 mL vs. percutaneous: 61.3 mL, P value < 0.001) and transfusion rate (open: 3.9% vs. percutaneous: 0%, P value = 0.013) were greater for the open group. The 90-day complication rate and mean length of stay were not different between cohorts (P value > 0.05)., Conclusion: Percutaneous robot-assisted spine surgery may increase radiation exposure, but can achieve a shorter operative time and lower risk for intraoperative blood loss for short-lumbar fusion. Percutaneous approaches do not appear to have an advantage for other short-term postoperative outcomes. Future multicenter studies on longer fusion surgeries and the inclusion of patient-reported outcomes are needed.Level of Evidence: 3., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Objective: Robotics is a major area for research and development in spine surgery. The high accuracy of robot-assisted placement of thoracolumbar pedicle screws is documented in the literature. The authors present the largest case series to date evaluating 90-day complication, revision, and readmission rates for robot-assisted spine surgery using the current generation of robotic guidance systems., Methods: An analysis of a retrospective, multicenter database of open and minimally invasive thoracolumbar instrumented fusion surgeries using the Mazor X or Mazor X Stealth Edition robotic guidance systems was performed. Patients 18 years of age or older and undergoing primary or revision surgery for degenerative spinal conditions were included. Descriptive statistics were used to calculate rates of malpositioned screws requiring revision, as well as overall complication, revision, and readmission rates within 90 days., Results: In total, 799 surgical cases (Mazor X: 48.81%; Mazor X Stealth Edition: 51.19%) were evaluated, involving robot-assisted placement of 4838 pedicle screws. The overall intraoperative complication rate was 3.13%. No intraoperative implant-related complications were encountered. Postoperatively, 129 patients suffered a total of 146 complications by 90 days, representing an incidence of 16.1%. The rate of an unrecognized malpositioned screw resulting in a new postoperative radiculopathy requiring revision surgery was 0.63% (5 cases). Medical and pain-related complications unrelated to hardware placement accounted for the bulk of postoperative complications within 90 days. The overall surgical revision rate at 90 days was 6.63% with 7 implant-related revisions, representing an implant-related revision rate of 0.88%. The 90-day readmission rate was 7.13% with 2 implant-related readmissions, representing an implant-related readmission rate of 0.25% of cases., Conclusions: The results of this multicenter case series and literature review suggest current-generation robotic guidance systems are associated with low rates of intraoperative and postoperative implant-related complications, revisions, and readmissions at 90 days. Future outcomes-based studies are necessary to evaluate complication, revision, and readmission rates compared to conventional surgery.

Background Context: Robot-assisted spine surgery continues to rapidly develop as evidenced by the growing literature in recent years. In addition to demonstrating excellent pedicle screw accuracy, early studies have explored the impact of robot-assisted spine surgery on reducing radiation time, length of hospital stay, operative time, and perioperative complications in comparison to conventional freehand technique. Recently, the Mazor X Stealth Edition was introduced in 2018. This robotic system integrates Medtronic's Stealth navigation technology into the Mazor X platform, which was introduced in 2016. It is unclear what the impact of these advancements have made on clinical outcomes., Purpose: To compare the outcomes and complications between the most recent iterations of the Mazor Robot systems: Mazor X and Mazor X Stealth Edition., Study Design: Multicenter cohort PATIENT SAMPLE: Among four different institutions, we included adult (≥18 years old) patients who underwent robot-assisted spine surgery with either the Mazor X (non-navigated robot) or Stealth (navigated robot) platforms., Outcome Measures: Primary outcomes included robot time per screw, fluoroscopic radiation time, screw accuracy, robot abandonment, and clinical outcomes with a minimum 90 day follow up., Methods: A one-to-one propensity-score matching algorithm based on perioperative factors (e.g. demographics, comorbidities, primary diagnosis, open vs. percutaneous instrumentation, prior spine surgery, instrumented levels, pelvic fixation, interbody fusion, number of planned robot screws) was employed to control for the potential selection bias between the two robotic systems. Chi-square/fisher exact test and t-test/ANOVA were used for categorical and continuous variables, respectively., Results: From a total of 646 patients, a total of 372 adult patients were included in this study (X: 186, Stealth: 186) after propensity score matching. The mean number of instrumented levels was 4.3. The mean number of planned robot screws was 7.8. Similar total operative time and robot time per screw occurred between cohorts (p>0.05). However, Stealth achieved significantly shorter fluoroscopic radiation time per screw (Stealth: 7.2 seconds vs. X: 10.4 seconds, p<.001) than X. The screw accuracy for both robots was excellent (Stealth: 99.6% vs. X: 99.1%, p=0.120). In addition, Stealth achieved a significantly lower robot abandonment rate (Stealth: 0% vs. X: 2.2%, p=0.044). Furthermore, a lower blood transfusion rate was observed for Stealth than X (Stealth: 4.3% vs. X: 10.8%, p=0.018). Non-robot related complications such as dura tear, motor/sensory deficits, return to the operating room during same admission, and length of stay was similar between robots (p>0.05). The 90-day complication rates were low and similar between robot cohorts (Stealth: 5.4% vs. X: 3.8%, p=0.456)., Conclusion: In this multicenter study, both robot systems achieved excellent screw accuracy and low robot time per screw. However, using Stealth led to significantly less fluoroscopic radiation time, lower robot abandonment rates, and reduced blood transfusion rates than Mazor X. Other factors including length of stay, and 90-day complications were similar., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Robot-assisted platforms in spine surgery have rapidly developed into an attractive technology for both the surgeon and patient. Although current literature is promising, more clinical data is needed. The purpose of this paper is to determine the effect of robot-related complications on clinical outcomes METHODS: This multicenter study included adult (≥18 years old) patients who underwent robot-assisted lumbar fusion surgery from 2012-2019. The minimum follow-up was 1 year after surgery. Both bivariate and multivariate analyses were performed to determine if robot-related factors were associated with reoperation within 1 year after primary surgery., Results: A total of 320 patients were included in this study. The mean (standard deviation) Charlson Comorbidity Index was 1.2 (1.2) and 52.5% of patients were female. Intraoperative robot complications occurred in 3.4% of patients and included intraoperative exchange of screw (0.9%), robot abandonment (2.5%), and return to the operating room for screw exchange (1.3%). The 1-year reoperation rate was 4.4%. Robot factors, including robot time per screw, open vs. percutaneous, and robot system, were not statistically different between those who required revision surgery and those who did not (P>0.05). Patients with robot complications were more likely to have prolonged length of hospital stay and blood transfusion, but were not at higher risk for 1-year reoperations. The most common reasons for reoperation were wound complications (2.2%) and persistent symptoms due to inadequate decompression (1.5%). In the multivariate analysis, robot related factors and complications were not independent risk factors for 1-year reoperations., Conclusion: This is the largest multicenter study to focus on robot-assisted lumbar fusion outcomes. Our findings demonstrate that 1-year reoperation rates are low and do not appear to be influenced by robot-related factors and complications; however, robot-related complications may increase the risk for greater blood loss requiring a blood transfusion and longer length of stay.

Lumbar spinal stenosis (LSS) is the leading cause of morbidity and mortality worldwide. LSS pathology is associated with secondary injury caused by inflammation, oxidative damage and cell death. Apart from laminectomy, pharmacological therapy targeting secondary injury is limited. Statins are FDA-approved cholesterol-lowering drug. They also show pleiotropic anti-inflammatory, antioxidant and neuroprotective effects. To investigate the therapeutic efficacy of simvastatin in restoring normal locomotor function after cauda equina compression (CEC) in a rat model of LSS, CEC injury was induced in rats by implanting silicone gels into the epidural spaces of L4 and L6. Experimental group was treated with simvastatin (5 mg/kg body weight), while the injured (vehicle) and sham operated (sham) groups received vehicle solution. Locomotor function in terms of latency on rotarod was measured for 49 days and the threshold of pain was determined for 14 days. Rats were sacrificed on day 3 and 14 and the spinal cord and cauda equina fibers were extracted and studied by histology, immunofluorescence, electron microscopy (EM) and TUNEL assay. Simvastatin aided locomotor functional recovery and enhanced the threshold of pain after the CEC. Cellular Infiltration and demyelination decreased in the spinal cord from the simvastatin group. EM revealed enhanced myelination of cauda equina in the simvastatin group. TUNEL assay showed significantly decreased number of apoptotic neurons in spinal cord from the simvastatin group compared to the vehicle group. Simvastatin hastens the locomotor functional recovery and reduces pain after CEC. These outcomes are mediated through the neuroprotective and anti-inflammatory properties of simvastatin. The data indicate that simvastatin may be a promising drug candidate for LSS treatment in humans.

Background Context: Percutaneous intradiscal therapies are gaining popularity as a regenerative treatment option for spinal disc degeneration. The risks, benefits, and possible complications associated with such procedures have been poorly defined. As these procedures are performed with increasing frequency, the likelihood that clinicians will be faced with significant complications also increases., Purpose: The purpose of this study is to describe a significant complication of a percutaneous intradiscal bone marrow and adipose tissue transplantation for symptomatic lumbar disc degeneration., Study Design: The study design is a case report., Methods: Two weeks after an injection of adipose cells, bone marrow aspirate and plasma into his L3-L4 and L5-S1 lumbar discs, a 64-year-old patient presented to the emergency room with cauda equina syndrome, fever, and back pain. Magnetic resonance imaging diagnosed L3-L4 disc extrusion, discitis with osteomyelitis, and epidural abscess, resulting in emergency decompressive surgery. An epidural abscess was drained, extruded disc material was removed, and cultures obtained. Five days later, once afebrile on antibiotics, he underwent a definitive interbody arthrodesis and stabilization., Results: Cauda equina syndrome resolved, osteomyelitis (methicillin-resistant Staphylococcus epidermidis) was treated, and instrumented arthrodesis stabilized the involved segment., Conclusions: Complications associated with the intradiscal injection of agents, such as stem cells, fibrin glue, adipose tissue, or bone marrow, have been poorly defined. Given the nature of the degenerating disc, serious adverse events, including discitis, osteomyelitis, and extrusion of disc contents, may occur., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Lumbar spinal stenosis (LSS) causes ischemia, inflammation, demyelination and results in dysfunction of the cauda equina (CE), leading to pain and locomotor functional deficits. We investigated whether exogenous administration of S-nitrosoglutathione (GSNO), an endogenous redox modulating anti-neuroinflammatory agent, hastens functional recovery in a CE compression (CEC) rat model. CEC was induced in adult female rats by the surgical implantation of two silicone blocks within the epidural spaces of L4-L6 vertebrae. GSNO (50 μg/kg body weight) was administered by gavage 1 h after the injury, and the treatment was continued daily thereafter. GSNO induced change in the pain threshold was evaluated for four days after the compression. Tissue analyses and locomotor function evaluation were carried out at two weeks and four weeks after the CEC respectively. GSNO significantly improved motor function in CEC rats as evidenced by an increased latency on rotarod compared with vehicle-treated CEC rats. CEC induced hyperalgesia was decreased by GSNO. GSNO also increased the expression of VEGF, reduced cellular infiltration (H&E staining) and apoptotic cell death (TUNEL assay), and hampered demyelination (LFB staining and g-ratio). These data demonstrate that administration of GSNO after CEC decreased inflammation, hyperalgesia and cell death leading to improved locomotor function of CEC rats. The therapeutic potential of GSNO observed in the present study with CEC rats suggests that GSNO is a candidate drug to test in LSS patients.

Adult spinal deformity may occur as the result of a number of conditions and patients may present with a heterogeneous group of symptoms. Multiple etiologies may cause spinal deformity; however, symptoms are associated with progressive and asymmetric degeneration of the spinal elements potentially leading to neural element compression. Symptoms and clinical presentation vary and may be related to progressive deformity, axial back pain, and/or neurologic symptoms. Spinal deformity is becoming more common as adults 55-64 years of age are the fastest growing proportion of the U.S. population. As the percentage of elderly in the United States accelerates, more patients are expected to present with painful spinal conditions, potentially requiring spinal surgery. The decision between operative and nonoperative treatment for adult spinal deformity is based on the severity and type of the patient's symptoms as well as the magnitude and risk of potential interventions.

Object. The implantation of interbody fusion cages allows for the restoration of disc height and the enlargement of the neuroforaminal space. The purpose of this study was to compare the extent of subsidence occurring after conventional cage placement compared to a novel wider cage placement technique. Methods. This study is a retrospective evaluation of radiographs of patients who underwent stand-alone single level anterior lumbar interbody fusion with lordotic titanium cages and rhBMP-2. Fifty-three patients were evaluated: 39 patients had wide cage placement (6 mm interdevice distance) and 14 had narrow cage placement (2 mm interdevice distance). Anterior and posterior intervertebral disc space heights were measured post-operatively and at follow-up imaging. Results. The decrease in anterior intervertebral disc space height was 2.05 mm versus 3.92 mm (P < .005) and 1.08 mm versus 3.06 mm in posterior disc space height for the wide cage placement and the narrow cage placement respectively. The proportion of patients with subsidence greater than 2 mm was 41.0% in the wide cage patients and 85.7% for the narrow cage patients (P < .005). Conclusions. The wider cage placement significantly reduced the amount of subsidence while allowing for a greater exposed surface area for interbody fusion.

Background: Urinary bladder and renal dysfunction are secondary events associated with spinal cord injury (SCI) in humans. These secondary events not only compromise quality of life but also delay overall recovery from SCI pathophysiology. Furthermore, in experimental models the effects of SCI therapy on bladder and renal functions are generally not evaluated. In this study, we tested whether simvastatin improves bladder and renal functions in a rat model of experimental SCI., Methods: SCI was induced by controlled contusion of T9-T10 in adult female rats. Simvastatin (5 mg/Kg body weight) was administered at two hours after SCI and repeated every 24 hours until the end point. Simvastatin-treated SCI animals (simvastatin group) were compared with vehicle-treated SCI animals (vehicle group) in terms of the Basso Beattie Bresnahan score, tissue morphology, cell death, and bladder/renal functions., Results: The urinary bladder of vehicle animals showed a 4.3-fold increase in size and a 9-fold increase in wet weight compared to sham animals. Following SCI, the urine to plasma osmolality ratio increased initially but decreased 1 week after SCI. Hematoxylin and eosin staining of bladder tissue showed transitional epithelial hyperplasia, degeneration of lamina propria, and enlargement of tunica adventia in addition to detrusor muscle hypertrophy. Rats treated with simvastatin for 14 days displayed remarkable recovery by showing decreased bladder size and maintenance of a normal urine/plasma osmolality ratio, in addition to improved locomotion. The muscularis layer of the bladder also regained its compact nature in simvastatin animals. Moreover, SCI-induced renal caspase-3 activity was significantly decreased in the simvastatin group indicating the ability of simvastatin to reduce the renal tubular apoptosis., Conclusion: Post-injury administration of simvastatin ameliorates bladder and renal dysfunction associated with SCI in rats.

Background Context: Outcomes of spinal treatments are evaluated by clinical relevance: the proportion of patients who reach a minimum clinically important outcome change. Outcomes are evaluated through multiple measurements, and the inconsistency of outcome change across measurements is not known., Purpose: The primary purpose of this study was to illustrate outcome inconsistencies after spinal surgery. Secondary goals of this study were to develop an index of overall change that incorporates outcome inconsistencies, to relate the index of overall change to patients' global assessment and satisfaction with treatment, to relate the index of global change to an intuitively understandable outcome: the level of tolerable pain., Study Design: This study is a review of prospectively collected patient-reported outcomes data., Patient Sample: Four hundred sixty patients from a large multicenter database were chosen. Those patients were included in the sample because they had undergone lumbar surgery and had baseline and 1-year follow-up scores. Baseline and 1-year follow-up scores for Oswestry Disability Index (ODI), physical component summary (PCS) of the Medical Outcome Study Short Form-36 (SF-36), numerical back and leg pain scales, and 1-year scores for satisfaction with results were included in the study., Outcome Measures: The outcome measures of the study were preoperative and 1-year postoperative scores for ODI, PCS, back pain scale, leg pain scale, health transition item of the SF-36, and satisfaction with results scales., Methods: Oswestry Disability Index, SF-36, and pain scales were administered before and 1 year after spinal surgery. Satisfaction with results questionnaires were administered 1 year after surgery. The following threshold values were previously established and were used to evaluate outcome changes: minimum clinically important difference (MCID), substantial clinical benefit (SCB), and standard error of the mean. The following proportions of patients were determined according to outcome changes: "deteriorated," "no change," "below MCID," "above MCID," and "above SCB." The consistency of outcome change was determined amongst the four outcome measures. An index of overall change was developed and related to patients' answers to the health transition item of the SF-36 and to the satisfaction with results scale. The overall change index was also compared with the tolerable pain level., Results: Only 40.5% of patients report consistent outcome changes on all four measures. The overall change index was significantly correlated to the global change and satisfaction scale (rho=.67, p less than .001). The overall change index was clearly associated with the tolerable pain level., Conclusions: Efforts should be made to take into account the inconsistency of outcomes and to make clinical relevance more readily understandable by patients and clinicians.

Background Context: Chondromyxoid fibroma (CMF) and aneurysmal bone cysts (ABCs) are rare bone tumors and even rarer in the spine. To date, no report has been made of CMF with secondary ABC in the cervical spine., Purpose: The purpose of this study was to describe the diagnosis and surgical treatment of a case of CMF with secondary ABC of C6, a rare occurrence in an uncommon location., Study Design: The study design is a case report., Methods: A 27-year-old woman presented with numbness with paresthesias of the right upper extremity. Diagnostic imaging revealed diffuse enlargement of the right C6 lamina extending into the pedicle and medial facet joint. Surgical treatment consisted of complete C6 laminectomy, total resection of the extradural cervical mass, posterior lateral fusion at C5-C7, and posterior segmental instrumentation from C5 to C7. Histopathology was consistent with CMF with secondary ABC., Results: Laminectomy and instrumented segmental fusion provided an excellent clinical outcome. The instrumented fusion maintained the sagittal balance of the spine and stabilized across a complete facetectomy. The excision will likely avoid recurrence of the lesion., Conclusions: Treatment of CMF and ABC is challenging in the spine because of the proximity to neural structures. Aggressive surgical treatment makes recurrence less likely but creates the risk of spinal instability. Adequate surgical treatment needs to provide spinal stability., (Copyright 2010 Elsevier Inc. All rights reserved.)

Background: Twenty-four-month outcomes have been reported for patients with degenerative lumbar disc disease who were treated with stand-alone anterior lumbar interbody arthrodesis with use of dual tapered interbody fusion cages and recombinant human bone morphogenetic protein-2. This report represents an update of the clinical and radiographic results of this treatment at six years., Methods: Two hundred and seventy-seven patients with single-level degenerative disc disease with up to grade-I spondylolisthesis were enrolled in two prospective, multicenter, U.S. Food and Drug Administration-approved investigational device exemption studies and were treated with an open or a laparoscopic surgical procedure. The patients received recombinant human bone morphogenetic protein-2 on an absorbable collagen sponge with lumbar fusion cage implants. One hundred and forty-six patients completed the six-year clinical follow-up evaluations, and 130 patients had complete radiographic follow-up at six years. Outcomes were determined with use of well-established clinical outcome measurements (Oswestry Disability Index, Short Form-36, and back and leg pain scores) and radiographic assessments., Results: At six years, 128 (98%) of the 130 patients treated with recombinant human bone morphogenetic protein-2 and stand-alone fusion cages had a fusion. The second surgery rate was 6.7% (eighteen patients) prior to two years and 3.7% (seven patients) from two to six years. A worst-case scenario analysis, which includes all second surgical procedures due to pseudarthrosis, resulted in a fusion rate at seventy-two months of 91% (128 of 141). Significant improvements in the Oswestry Disability Index scores, Short Form-36 health survey physical component summary scores, and back and leg pain scores were achieved by six weeks in both the open and laparoscopic groups and were sustained at six years (p < 0.001). The percentage of patients who were working at six months (63%) was higher than the percentage who had been working preoperatively (52%), and this improvement was sustained at six years (68%)., Conclusions: The use of dual tapered threaded fusion cages and recombinant human bone morphogenetic protein-2 on an absorbable collagen sponge obtained and maintained intervertebral spinal fusion, improved clinical outcomes, and reduced pain after anterior lumbar interbody arthrodesis in patients with degenerative lumbar disc disease.

Background Context: The impact of lumbar spinal surgery is commonly evaluated with three patient-reported outcome measures: Oswestry Disability Index (ODI), the physical component summary (PCS) of the Short Form of the Medical Outcomes Study (SF-36), and pain scales. A minimum clinically important difference (MCID) is a threshold used to measure the effect of clinical treatments. Variable threshold values have been proposed as MCID for those instruments despite a lack of agreement on the optimal MCID calculation method., Purpose: This study has three purposes. First, to illustrate the range of values obtained by common anchor-based and distribution-based methods to calculate MCID. Second, to determine a statistically sound and clinically meaningful MCID for ODI, PCS, back pain scale, and leg pain scale in lumbar spine surgery patients. Third, to compare the discriminative ability of two anchors: a global health assessment and a rating of satisfaction with the results of the surgery., Study Design: This study is a review of prospectively collected patient-reported outcomes data., Patient Sample: A total of 454 patients from a large database of surgeries performed by the Lumbar Spine Study Group with a 1-year follow-up on either ODI or PCS were included in the study., Outcome Measures: Preoperative and 1-year postoperative scores for ODI, PCS, back pain scale, leg pain scale, health transition item (HTI) of the SF-36, and Satisfaction with Results scales., Methods: ODI, SF-36, and pain scales were administered before and 1 year after spinal surgery. Several candidate MCID calculation methods were applied to the data and the resulting values were compared. The HTI of the SF-36 was used as the anchor and compared with a second anchor (Satisfaction with Results scale)., Results: Potential MCID calculations yielded a range of values: fivefold for ODI, PCS, and leg pain, 10-fold for back pain. Threshold values obtained with the two anchors were very similar., Conclusions: The minimum detectable change (MDC) appears as a statistically and clinically appropriate MCID value. MCID values in this sample were 12.8 points for ODI, 4.9 points for PCS, 1.2 points for back pain, and 1.6 points for leg pain.

Background Context: The effectiveness of spinal surgery as a treatment option is currently evaluated through the assessment of patient-reported outcomes (PROs). The minimum clinically important difference (MCID) represents the smallest improvement considered worthwhile by a patient. The concept of an MCID is offered as the new standard for determining effectiveness of a given treatment and describing patient satisfaction in reference to that treatment., Purpose: Our goal is to review the various definitions of MCID and the methods available to determine MCID., Study Design: The primary means of determining the MCID for a specific treatment are divided into anchor-based and distribution-based methods. Each method is further subdivided and examined in detail., Methods: The overall limitations of the MCID concept are first identified. The basic assumptions, statistical biases, and shortcomings of each method are examined in detail., Results: Each method of determining the MCID has specific shortcomings. Three general limitations in the accurate determination of an MCID have been identified: the multiplicity of MCID determinations, the loss of the patient's perspective, and the relationship between pretreatment baseline and posttreatment change scores., Conclusions: An ideal means of determining the MCID for a given intervention is yet to be determined. It is possible to develop a useful method provided that the assumptions and methodology are initially declared. Our efforts toward the establishment of a MCID will rely on the establishment of specific external criteria based on the symptoms of the patient and treatment intervention being evaluated.

Objective: To determine whether preoperative disc space height (DSH) influences the clinical outcomes of patients diagnosed with single-level symptomatic discogenic disease and treated with a stand-alone anterior lumbar interbody fusion with two tapered threaded fusion cages, we performed a retrospective analysis of 392 patients., Methods: Preoperative radiographs were used to establish four study groups based on the patients' DSH: the tall disc group: DSH >15 mm; the intermediate tall group: DSH ranging from 10 to 15 mm; the intermediate collapsed group: DSH ranging from 5 to 10 mm; and the collapsed disc group: DSH <5 mm., Results: All of the patient groups exhibited improvement in their clinical outcomes. However, patients in the collapsed disc group (DSH of <5 mm) tended to have earlier and greater improvement in Oswestry Disability Index scores, Physical Component Summary scores of the Short Form-36, and Visual Analog Scale scores for low back pain., Conclusion: Symptomatic disc degeneration can be readily identified with plain radiographic findings, and patients' symptoms can often be relieved predictably with a stand-alone interbody fusion procedure.

Objectives: Obliteration of end-plate landmarks by interbody fusion has made the traditional measurement of segmental lumbar lordosis nearly impossible. Because the L4-L5 and L5-S1 levels are most likely to be subjected to fusion procedures or arthroplasty and contribute to more than half of normal lumbar lordosis, it is crucial to identify a reproducible and accurate means of measuring segmental lordosis at these levels., Methods: Twelve spinal surgeons measured lordosis at L4-L5 and L5-S1 on 10 separate radiographs using three techniques for L4-L5 and four techniques for L5-S1. With use of identical radiographs, measurements first were made using a manual method and then were repeated with a computer-assisted method. Measurements were analyzed for both intraobserver and interobserver error., Results: The individual data demonstrated an intraobserver variance of 9.56 and a standard deviation of 3.092 for computerized measurements compared with 7.742 and 2.782 for manual measurements. The interobserver variance was 4.107 with a standard deviation of 2.027 for the computerized group compared with 4.221 and 2.055 for manual measurements. When analyzed as a group to evaluate interobserver error, the pooled data yielded variance of 19.235 for the computerized group and 19.117 for the manual measurements., Conclusions: Variance calculations identified the Cobb technique and the posterior vertebral body technique as the least variable measurement techniques for the L4-L5 and L5-S1 levels, respectively; however, there was no statistical significance. In direct comparison, the manual and computer-assisted techniques were found to be statistically equivalent with similar degrees of variance. We believe that the anterior vertebral technique, which did not demonstrate a significant difference from other techniques, will prove to be the most reliable method of assessing segmental lumbar lordosis in patients before surgery, after interbody fusion, and after motion-sparing disc arthroplasty.

In a retrospective analysis of two large multicenter clinical studies, 321 patients with degenerative lumbar disc disease were divided into two groups who underwent anterior lumbar interbody fusion using two threaded titanium fusion cages. To determine whether differences in surgical procedures and cage design affect anterior and posterior annular distraction and clinical outcomes, the authors evaluated the clinical and radiographic outcomes of patients treated with a stand-alone ALIF procedure. End-plate preservation techniques were associated with improved anterior and posterior disc space distraction compared with standard end-plate preparation techniques. Similarly, the use of the LT-CAGE device led to greater improvements in restoration of segmental lordosis than did the use of standard cylindric cages. Furthermore, these surgical benefits resulted in improved clinical outcomes as early as 3 months and were maintained over a 2-year follow-up period in patients with improved postoperative disc space distraction and lordosis. Placing cylindric cages in a lordotic or trapezoidal disc space can be accomplished only through asymmetric reaming of the vertebral end plates. In a lordotic disc space, the posterior portion of the disc must be reamed more than the anterior portion. This over-reaming inhibits distraction of the posterior disc space and limits restoration of neuroforaminal height. Reduced reaming and symmetric reaming of the vertebral end plates enable the surgeon to restore anatomic segmental lordosis across the disc space. The tapered cage configuration aids in maintaining segmental lordosis. Anatomic restoration of disc space contours has an impact on a patient's outcome after stand-alone anterior interbody fusion surgery.

A multiple-site, nonlethal rabbit surgical model of spinal implant infection was used to assess the efficacy of a spinal wound lavage to reduce post-operative infection from methicillinresistant Staphylococcus aureus (MRSA). Multiple aqueous lavages of isotonic saline were compared to the same procedure using 1wt% pooled human immunoglobulin G (IgG) applied directly to the surgical implant sites. Visually observed clinically relevant signs of infection (e.g. , swelling, erythema, pus) were supported by bacterial enumeration from multiple biopsied tissue and bone sites post-mortem at 7 and 28 days post-challenge. Clinical signs of infection were significantly reduced in IgG-lavaged infected spinal sites. Bacterial enumeration also exhibited statistically significant reductions in soft tissues, bone and on K-wire spinal implants using IgG lavage compared with saline. Complete healing of all surgical wounds was seen after 28 days, although isolated fibrosed abscesses were observed in autopsied sites treated with both IgG and saline lavages. Local use of IgG wound lavage is proposed as supplementary infection prophylaxis against antibiotic resistant implant-centered or surgical wound infection.

Study Design: A new spinal implant model was designed to study device-centered infection with methicillin-resistant Staphylococcus aureus in multiple noncontiguous surgical sites in the lumbar spine region of a rabbit., Objective: To develop a multiple-site spinal implant device-centered infection model in rabbits., Summary of Background Data: Results in many recent studies show that postoperative wound infection after spinal implant surgery and the increase in antibiotic-resistant bacteria are a concern. Anti-infection strategies must be tested in relevant animal models that will lead to appropriate clinical studies., Methods: Eight anesthetized New Zealand White rabbits underwent completely isolated partial laminectomy and subsequent stainless steel Kirschner wire implantation directly into the transverse processes of vertebrae T13, L3, and L6. The middle sites (L3) were used as sterile control sites, and the outer sites (T13, L6) were challenged with different amounts of methicillin-resistant Staphylococcus aureus. Rabbits were killed after 7 days, and biopsies were performed to provide evidence for device-centered infection. Bacterial growth on the implant surfaces and in surrounding tissues and bone was assayed., Results: Overall device-centered infection was established after 7 days in 100% of the sites challenged with 10(3) colony-forming units methicillin-resistant Staphylococcus aureus or higher. No infection was seen in any of the control sites located between infected vertebrae. Multiple blood and liver samples showed that the separate localized infections did not become systemic after 7 days., Conclusions: This new animal model demonstrates that multiple biomaterial implants can be evaluated in the same animal and provides a technique for investigating postoperative device-centered infection of the spine. Infection was demonstrated in noncontiguous lumbar sites of the spine, whereas adjacent control sites remained sterile. Because there was no cross contamination or systemic spread of the infection, multiple anti-infection strategies or implant materials can now be tested for efficacy in a single animal to combat dramatic and costly postoperative implant infections.

Os odontoideum has recently been considered an acquired lesion of the second cervical vertebrae. This case documents the natural progression of the formation of os odontoideum and correlates it with a traumatic event. This is the first case reported in the literature.