Search

There are several animal models routinely used for study of the spinal fusion process and animal selection largely depends on the scientific question to be answered. This review outlines the advantages and disadvantages of various animal models used to study spinal fusion and describes the New Zealand White (NSW) rabbit which is the most popular preclinical model to study spinal fusion. We outline critical steps required in planning and performing spinal fusion surgery in this model. This includes determination of the required animal number to obtain statistical significance, an outline of appropriate technique for posterolateral fusion and other components of completing a study. As advances in drug delivery move forward and our understanding of the cascade of gene expression occurring during the fusion process grows, performing and interpreting preclinical animal models will be vital to validating new therapies to enhance spinal fusion. [ABSTRACT FROM AUTHOR]

Abstract: Evaluation of new technology in sports medicine is supposed to promote improvements in the care of patients. It is also supposed to prohibit technology that can harm patients. This evaluation process is not perfect and at times can promote technology that not only does not help patients but may harm them. Two examples of new sports medicine technology that were widely adopted but eventually abandoned are thermal capsulorrhaphy for treatment of shoulder instability and the Gore-Tex prosthetic ligament (W. L. Gore & Associates, Flagstaff, AZ) for patients with anterior cruciate ligament deficiency. On analysis of the quick adoption of these 2 failed procedures, certain recommendations are apparent for improvement of the evaluation process. There must be a sound rationale behind any new technology, basic science research into the theory of the medical technology, and demonstrated improvements in animal models and clinical studies that are prospective cohort studies or randomized controlled trials, and finally, there must be careful follow-up and postmarket surveillance. [ABSTRACT FROM AUTHOR]

Study Design: Biomechanical analysis., Objective: To evaluate the depth of subsidence resulting from an expandable interbody cage at varying bone foam densities., Summary of Background Data: Expandable interbody cages have been shown to be associated with increased rates of subsidence. It is critical to evaluate all variables which may influence a patient's risk of subsidence following the placement of an expandable interbody cage., Methods: In the first stage of the study, subsidence depth was measured with 1 Nm of input expansion torque. In the second stage, the depth of subsidence was measured following 150 N output force exerted by an expandable interbody cage. Within each stage, different bone foam densities were analyzed, including 5, 10, 15, and 20 pounds per cubic foot (PCF). Five experimental trials were performed for each PCF material, and the mean subsidence depths were calculated. Trials which failed to reach 150 N output force were considered outliers and were excluded from the analysis., Results: There was an overall decrease in subsidence depth with increasing bone foam density. The mean subsidence depths at 150 N output force were 2.0±0.3 mm for 5 PCF, 1.8±0.2 mm for 10 PCF, 1.1±0.2 mm for 15 PCF, and 1.1±0.2 mm for 20 PCF bone foam. The mean subsidence depths at 1 Nm of input torque were 2.3±0.5 mm for 5 PCF, 2.3±0.5 mm for 10 PCF, 1.2±0.2 mm for 15 PCF, and 1.1±0.1 mm for 20 PCF bone foam., Conclusions: Depth of subsidence was negatively correlated with bone foam density at both constant input torque and constant endplate force. Because tactile feedback of cage expansion into the subsiding bone cannot be reliably distinguished from true expansion of disc space height, surgeons should take bone quality into account when deploying expandable cages., Competing Interests: D.N., V.C., and J.R. are employed by Stryker Spine, who helped to conduct this study. The other authors declare no conflict of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Cadaveric study., Objective: Compare discectomy performance between transforaminal lumbar interbody fusion (TLIF) done via an endoscopic versus a tubular technique., Summary of Background Data: Performance of an adequate discectomy is essential to lumbar fusion when performing a TLIF. Previous cadaveric studies comparing open and minimally invasive techniques have reported 36.6%-80% discectomy. There is controversy whether an endoscopic TLIF (E-TLIF) can allow for an adequate discectomy., Materials/methods: An E-TLIF was performed on 14 discs (T12-L5) and a minimally invasive tubular TLIF (T-TLIF) was performed on 15 discs (T12-L4, L5-S1). Fellowship trained surgeons performed the TLIFs. Each disc was transected after discectomy and a digital image was analyzed using an imaging processing software to determine the percent of discectomy. Each quadrant of the discectomy was compared. Quadrant one was defined as the left posterior-ipsilateral quadrant of the disc, with each quadrant numbered 2-4 clockwise around the disc. The time to perform the discectomy was compared. Pedicle screws were placed contralaterally to the TLIF and the change in interpedicular distance was compared between techniques after expandable cage implantation as a marker for indirect decompression. A student's t-test was used to determine statistical significance., Results: There was no difference in discectomy performance between techniques (48.86%+/-6.98% T-TLIF vs. 50.26%+/-7.38% E-TLIF, P=0.61). There was no statistical difference between T-TLIF vs E-TLIF at quadrants 1, 3 and 4. There was a difference in discectomy performance at quadrant 2 (39.02%+/-10.18% T-TLIF vs 50.13%+/-14.00% E-TLIF, P=0.02). There was no statistical difference between interpedicular distance created (2.20 mm+/-1.97 mm T-TLIF vs 1.36 mm+/-1.82 mm E-TLIF, P=0.24). E-TLIF took less time than MIS-TLIF (20.00 min+/-7.12 min vs 15.22 min+/-4.42 min, P=0.048)., Conclusion: Our cadaveric study demonstrates that an adequately performed E-TLIF discectomy may be comparable to a T-TLIF discectomy. Further research is required to maximize the efficiency and instrumentation of this technique., Competing Interests: Conflict of Interest: Sohrab Virk is a consultant for LifeSpine., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Lumbar microdiscectomy is a surgical procedure that is frequently used in the treatment of symptomatic lumbar herniation. Differences in outcomes following primary and revision lumbar microdiscectomy have been previously studied, with reports of comparably satisfactory results from the Spine Patient Outcomes Research Trial. In this study, we further investigate these outcomes, including length of stay, bleeding events, and durotomy. We hypothesized that length of stay, incidence of bleeding events, and dural tear would be greater in the revision cohort., Methods: The ACS-National Surgical Quality Improvement Program database was queried for patients undergoing single-level primary and revision lumbar microdiscectomy between 2019 and 2022. Eligibility for inclusion was determined by age >18 years and current procedural terminology codes 63030 and 63042. Patients with preoperative sepsis or cancer were excluded. Length of stay, wound infection, bleeding events requiring transfusion, cerebrospinal fluid leak, dural tear, and neurological injury were compared between the cohorts. Multivariable Poisson regression adjusted for demographics and comorbidities, including age, sex, race, body mass index, diabetes, smoking, and hypertension, was used to determine if revision was predictive of complications., Results: A total of 37,669 patients were included, of whom 3,635 (9.6%) required revision surgery. Patients in the revision cohort were older (54.25 ± 15.7 vs. 50.85 ± 16.0 years, P < 0.001) and had higher proportions of male (59.0% vs. 55.7%, P < 0.001) and non-Hispanic White patients (82.0% vs. 77.4%, P < 0.001). Length of stay (1.11 ± 2.5 vs. 1.58 ± 2.7, P < 0.001) and rates of wound infection (2.1% vs. 1.4%, P = 0.002) and bleeding events requiring transfusion (1.3% vs. 0.7%, P < 0.001) were greater in the revision cohort compared to primary patients. Differences in cerebrospinal fluid leak (0.2% vs. 0.1%, P = 0.116), dural tear complication (0.01% vs. 0.01%, P = 0.092), and neurological injury (0.008% vs. 0.006%, P = 0.691) between the revision and primary cohorts were nonsignificant. Poisson log-linear regression adjusted for demographics and comorbidities demonstrated revision as a significant predictor for length of stay ( χ 2 = 462.95, P < 0.001), wound infection ( χ 2 = 9.22, P = 0.002), and bleeding events ( χ 2 = 9.74, P = 0.002), while it was a nonsignificant predictor of cerebrospinal fluid leak ( χ 2 = 2.61, P = 0.106), dural tear ( χ 2 = 2.37, P = 0.123), and neurological injury ( χ 2 = 0.229, P = 0.632)., Conclusion: Revision surgery was a significant predictor of increased length of stay, wound infection, and bleeding events requiring transfusion. Surgeons and patients alike should be aware of increased risk for complications following revision lumbar microdiscectomy compared to primary discectomy., Competing Interests: There are no conflicts of interest., (Copyright: © 2024 Journal of Craniovertebral Junction and Spine.)

Introduction: While there is anecdotal evidence that the coronavirus disease 2019 (COVID-19) pandemic altered perioperative decision-making in patients requiring posterior cervical fusion (PCF), a national-level analysis to examine the significance of this hypothesis has not yet been conducted. This study aimed to determine the potential differences in perioperative variables and surgical outcomes of PCF performed before vs. during the COVID-19 pandemic., Methods: Adults who underwent PCF were identified in the 2019 (prepandemic) and 2020 (intrapandemic) NSQIP datasets. Differences in 30-day readmission, reoperation, and morbidity were evaluated using multivariate logistic regression. On the other hand, differences in operative time and relative value units (RVUs) were estimated using quantile regression. Furthermore, the odds ratios (OR) for length of stay (LOS) were estimated using negative binomial regression. Secondary outcomes included rates of nonhome discharge and outpatient surgery., Results: A total of 3,444 patients were included in this study (50.7% from 2020). Readmission, reoperation, morbidity, operative time, and RVUs per minute were similar between cohorts ( p >0.05). The LOS (OR 1.086, p <0.001) and RVUs-per-case (coefficient +0.360, p =0.037) were significantly greater in 2020 compared to 2019. Operation year 2020 was also associated with lower rates of nonhome discharge (22.3% vs. 25.8%, p =0.017) and higher rates of outpatient surgery (4.8% vs. 3.0%, p =0.006)., Conclusions: During the COVID-19 pandemic, a 28% decreased odds of nonhome discharge following PCF and a 72% increased odds of PCF being performed in an outpatient setting were observed. The readmission, reoperation, and morbidity rates remained unchanged during this period. This is notable given that patients in the 2020 group were more frail. This suggests that patients were shifted to outpatient centers possibly to make up for potentially reduced case volume, highlighting the potential to evaluate rehabilitation-discharge criteria. Further research should evaluate these findings in more detail and on a regional basis., Competing Interests: Conflicts of Interest: The authors declare that there are no relevant conflicts of interest., (Copyright © 2024 The Japanese Society for Spine Surgery and Related Research.)

Context: Literature on treating pediatric spinal deformity with navigation is limited, particularly using large nationally represented cohorts. Further, the comparison of single-institution data to national-level database outcomes is also lacking., Aim: (1) To compare navigated versus conventional posterior pediatric deformity surgery based on 30-day outcomes and perioperative factors using the National Surgical Quality Improvement Program (NSQIP) database and (2) to compare the outcomes of the NSQIP navigated group to those of fluoroscopy-only and navigated cases from a single-institution., Settings and Design: Retrospective cohort study., Subjects and Methods: Pediatric patients who underwent posterior deformity surgery with and without navigation were included. Primary outcomes were 30-day readmission, reoperation, morbidity, and complications. The second part of this study included AIS patients < 18 years old at a single institution between 2015 and 2019. Operative time, length of stay, transfusion rate, and complication rate were compared between single-institution and NSQIP groups., Statistical Analysis Used: Univariate analyses with independent t -test and Chi-square or Fisher's exact test was used. Multivariate analyses through the application of binary logistic regression models., Results: Part I of the study included 16,950 patients, with navigation utilized in 356 patients (2.1%). In multivariate analysis, navigation predicted reoperation, deep wound infection, and sepsis. After controlling for operative year, navigation no longer predicted reoperation. In Part II of the study, 288 single institution AIS patients were matched to 326 navigation patients from the NSQIP database. Operative time and transfusion rate were significantly higher for the NSQIP group., Conclusions: On a national scale, navigation predicted increased odds of reoperation and infectious-related events and yielded greater median relative value units (RVUs) per case but had longer operating room (OR) time and fewer RVUs-per-minute. After controlling for operative year, RVUs-per-minute and reoperation rates were similar between groups. The NSQIP navigated surgery group was associated with significantly higher operative time and transfusion rates compared to the single-institution groups., Competing Interests: There are no conflicts of interest., (Copyright: © 2023 Journal of Craniovertebral Junction and Spine.)

Study Design: A retrospective cohort study., Purpose: To compare 30-day readmission, reoperation, and morbidity for patients undergoing posterior cervical decompression and fusion (PCDF) in inpatient vs. outpatient settings., Overview of Literature: PCDF has recently been increasingly performed in outpatient settings, often utilizing minimally invasive techniques. However, literature evaluating short-term outcomes for PCDF is scarce. Moreover, no currently large-scale database studies have compared short-term outcomes between PCDF performed in the inpatient and outpatient settings., Methods: Patients who underwent PCDF from 2005 to 2018 were identified using the National Surgical Quality Improvement Program database. Regression analysis was utilized to compare primary outcomes between surgical settings and evaluate for predictors thereof., Results: We identified 8,912 patients. Unadjusted analysis revealed that outpatients had lower readmission (4.7% vs. 8.8%, p =0.020), reoperation (1.7% vs. 3.8%, p =0.038), and morbidity (4.5% vs. 11.2%, p <0.001) rates. After adjusting for baseline differences, readmission, reoperation, and morbidity no longer statistically differed between surgical settings. Outpatients had lower operative time (126 minutes vs. 179 minutes) and levels fused (1.8 vs. 2.2) (p <0.001). Multivariate analysis revealed that age (p =0.008; odds ratio [OR], 1.012), weight loss (p =0.045; OR, 2.444), and increased creatinine (p <0.001; OR, 2.233) independently predicted readmission. The American Society of Anesthesiologists (ASA) classification of ≥3 predicted reoperation (p =0.028; OR, 1.406). Rehabilitation discharge (p <0.001; OR, 1.412), ASA-class of ≥3 (p =0.008; OR, 1.296), decreased hematocrit (p <0.001; OR, 1.700), and operative time (p <0.001; OR, 1.005) predicted morbidity., Conclusions: The 30-day outcomes were statistically similar between surgical settings, indicating that PCDF can be safely performed as an outpatient procedure. Surrogates for poor health predicted negative outcomes. These results are particularly important as we continue to shift spinal surgery to outpatient centers. This importance has been highlighted by the need to unburden inpatient sites, particularly during public health emergencies, such as the coronavirus disease 2019 pandemic.

Introduction: The management of spinal neoplasia consists of surgical, radiation, and systemic options. Little data exist to guide management based on overall health status, which is particularly challenging when patients who could benefit from surgery may be too frail for it. This study's objective was to evaluate the 5-Item Modified Frailty Index (mFI-5) as a predictor of 30-day morbidity in patients undergoing instrumented resection for metastatic extradural spinal tumors., Methods: Adults undergoing extradural tumor resection from the 2011 to 2019 National Surgical Quality Improvement Program datasets were identified by Current Procedural Terminology codes 63275-63278 with an adjunct instrumentation code (22840-22843). Patients were classified into frailty levels 0, 1, or 2+ based on mFI-5 scores of 0, 1, or 2-5, respectively. The primary outcome was morbidity. Secondary outcomes were readmission and reoperation. Multivariate modeling was utilized to analyze mFI-5 as a predictor of outcomes. The Akaike information criterion (AIC) was used to compare relative-model-fit based on frailty versus individual comorbidity variables to determine the optimal model. Chi-squared and Fisher's exact tests were used to establish significance between individual complications and frailty., Results: There were 874 patients. Readmission, reoperation, and morbidity rates were 19.5%, 5.0%, 52.3%, respectively. In multivariate analyses, mFI-5=1 (OR: 1.45, SE: 0.31, p=0.036), mFI-5=2+ (OR: 1.41, SE: 0.40, p=0.036), operative time (OR: 1.18, SE: 0.03, p≤0.001), and chronic steroid use (OR: 1.56, SE: 0.42, p=0.037) independently predicted morbidity. Elective surgery (OR: 0.61) was protective. Frailty did not predict readmission or reoperation. Frailty was found to be significantly associated with respiratory complications, urinary tract infections, cardiac events, and sepsis/septic shock specifically., Conclusions: mFI-5=1 independently predicted 45% increased odds of morbidity. mFI-5=2+ independently predicted 41% increased odds of morbidity. Further, every 30 additional minutes of operative time predicted 18% increased odds of morbidity, suggesting an increased risk of site-related complication events. Taken together, the mFI-5 serves as a valid predictor of morbidity in patients with extradural tumor undergoing instrumented excision., Competing Interests: Conflicts of Interest: Dr. Jeff Silber receives teaching fees for Stryker., (Copyright © 2023 The Japanese Society for Spine Surgery and Related Research.)

Background: The decision upper-most instrumented vertebrae (UIV) in a multi-level fusion procedure can dramatically influence outcomes of corrective spine surgery. We aimed to create an algorithm for selection of UIV based on surgeon selection/reasoning of sample cases., Methods: The clinical/imaging data for 11 adult spinal deformity (ASD) patients were presented to 14 spine deformity surgeons who selected the UIV and provided reasons for avoidance of adjacent levels. The UIV chosen was grouped into either upper thoracic (UT, T1-T6), lower thoracic (LT, T7-T12), lumbar or cervical. Disagreement between surgeons was defined as ≥3 not agreeing. We performed a descriptive analysis of responses and created an algorithm for choosing UIV then applied this to a large database of ASD patients., Results: Surgeons agreed in 8/11 cases on regional choice of UIV. T10 was the most common UIV in the LT region (58%) and T3 was the most common UIV in the UT region (44%). The most common determinant of UIV in the UT region was proximal thoracic kyphosis and presence of coronal deformity. The most common determinant of UIV in the LT region was small proximal thoracic kyphosis. Within the ASD database (236 patients), when the algorithm called for UT fusion, patients fused to TL region were more likely to develop proximal junctional kyphosis (PJK) at 1 year post-operatively (76.9% vs . 38.9%, P=0.025)., Conclusions: Our algorithm for selection of UIV emphasizes the role of proximal and regional thoracic kyphosis. Failure to follow this consensus for UT fusion was associated with twice the rate of PJK., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/jss-20-598). Dr. SB reports personal fees from K2M, from Medtronic, personal fees from Nuvasive, from Orthofix, personal fees from Stryker, outside the submitted work; Dr. DB reports grants from Bioventus, grants from Depuy, grants from Pfizer, grants from Progenerative Medical, outside the submitted work; Dr. PP reports other from Allosource, personal fees from Globus Medical, personal fees from Medicrea, personal fees from Royal Biologics, personal fees from SpineWave, personal fees from Terumo, personal fees from Zimmer, outside the submitted work; Dr. MG reports grants from Depuy, personal fees from Globus, grants from Innomed, personal fees from Johnson and Johnson, personal fees from Medtronic, other from Proctor and Gamble, personal fees from Wolters Kluwer Health, outside the submitted work; Dr. TP reports other from Altus, personal fees from Globus Medical, personal fees from Medicrea, personal fees from Nuvasive, other from Spine Align, personal fees from Stryker, other from Torus Medical, outside the submitted work; Dr. HJK reports personal fees from Alphatec, other from K2M, other from Zimmer, outside the submitted work; Dr. JSS reports other from Alphatec, personal fees from Carlsmed, personal fees from Cerapedics, grants from Depuy, other from Nuvasive, personal fees from Styker, other from Zimmer, outside the submitted work; Dr. RE reports personal fees from Aesculap, other from Alphatec, personal fees from Baxter, personal fees from Biederman-Motech, personal fees from Carevature, other from Globus, other from Invuity, personal fees from Medtronic, other from Nocimed, personal fees and other from Nuvasive, personal fees from Radius, other from Seaspine, personal fees and other from SI Bone, other from Spine Innovations, outside the submitted work; Dr. KK reports personal fees and other from Depuy, personal fees and other from Orthofix, other from Strykler, outside the submitted work; Dr. GM reports personal fees from Carlsmed, other from K2M, other from Nuvasive, personal fees from Seaspine, personal fees from Stryker, personal fees from Viseon, outside the submitted work; Dr. CS reports grants from Depuy, grants from Globus, grants and other from Medtronic, other from Nuvasive, other from SI Bone, outside the submitted work; Dr. JG reports grants and other from Accuity, other from Cingulate, personal fees from Depuy, grants from Integra, personal fees from Intellirod, personal fees from K2M, personal fees from Mazor, personal fees from Medtronic, grants from Norton Healthcare, other from Nuvasive, personal fees from Pfizer, personal fees from Stryker, outside the submitted work; Dr. VL reports personal fees from Depuy, personal fees from Globus, other from Nuvasive, personal fees from Permanante Medical Group, outside the submitted work; Dr. FS reports grants from Depuy, personal fees from Globus, from K2M, personal fees from Medicrea, grants, personal fees and other from Medtronic, grants from Nuvasive, grants from Styker, grants, personal fees and other from Zimmer, outside the submitted work. The other authors have no conflicts of interest to declare., (2021 Journal of Spine Surgery. All rights reserved.)

Background Context: Narcotic use amongst patients suffering from lumbar radiculopathy is common, but the clinical benefit of narcotics for lumbar radiculopathy is likely minimal. It is unknown what the impact of preoperative use of narcotics has on outcomes related to lumbar microdiscectomy., Purpose: Determine the impact that preoperative opioid use has on postoperative outcomes after lumbar microdisectomy., Study Design: Retrospective analysis of a prospectively collected database., Patient Sample: One hundred and twenty-six patients undergoing a microdiscectomy for a lumbar disc herniation., Outcome Measures: Patient-reported outcomes measurement information system mental health scores (PROMIS MHS), patient-reported outcomes measurement information system physical health scores (PROMIS PHS) and oswestry disability index (ODI)., Methods: We analyzed a prospectively collected database of patients undergoing a lumbar microdiscectomy for preoperative opioid use. We measured the severity of lumbar pathology on MRI based on degree of facet/disc degeneration and cross-sectional area of the dural tube at the disc herniation. We tracked PROMIS MHS, PROMIS PHS and ODI for patients both preoperatively and postoperatively. A Mann-Whitney test was used to compare HRQOL scores and time to MCID for the opioid using cohort (OC) and the nonopioid using cohort (non-OC). We performed a linear regression analysis to determine correlation between preoperative opioid use and postoperative HRQOLs., Results: There were 44 of 126 microdiscectomy patients in the OC (32.5%). There was no difference in the dural cross-sectional area (p=.91), degree of facet degeneration (p=.38), or disc degeneration (p=.5) between OC and non-OC. There were no differences in PROMIS PHS, PROMIS MHS or ODI between the OC and non-OC at the preoperative visit and all postoperative time points. There were no differences in time to reach MCID between the OC and non-OC for ODI (p=.9), PROMIS PHS (p=.64) or PROMIS MHS (p=.90). At three months out from surgery there was a statistically significant correlation between pre-op opioid use and ODI (p=.02), PROMIS MHS (p=.02) and PROMIS PHS (p=.049)., Conclusions: Our results demonstrate that patients that use opioids prior to lumbar microdiscectomy have equivalent postoperative outcomes as those that do not use opioids. Use of higher doses of opioids is associated with worse short-term outcomes., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background Context: Patients with severe cervical deformity (CD) often have profound deficits in numerous activities of daily living. The association between health status and postoperative radiographic goals is difficult to quantify., Purpose: We aimed to investigate the radiographic characteristics of patients who achieved optimal health related quality of life scores following surgery for CD., Study Design: We performed a retrospective review of a prospectively collected database of patients with spinal deformity., Patient Sample: One hundred and fifty-three patients with cervical deformity OUTCOME MEASURES: Common health-related quality of life scores (HRQOLs) measurements were taken for patients treated operatively for cervical deformity including neck disability index (NDI), modified Japanese Orthopaedic Association scale (mJOA) for myelopathy and numeric rating scale for neck pain (NRS-neck), METHODS: Surgical patients with severe CD were isolated based upon a previously presented discriminant analysis which outlined a combination of preoperative cervical sagittal vertical axis (cSVA), T1 slope, maximum focal kyphosis in extension, C2 slope in extension, and number of kyphotic levels in extension. Those with available preoperative and 1-year postoperative HRQL data were included. Based on a previous study, patients were grouped into three distinct sagittal morphotypes of CD: focal deformity (FD), flat neck (FN = large TS-CL and lack of compensation), or cervicothoracic (CT). Postoperative outcomes were defined as "good" if a patient had ≥2 of the three following criteria (1) NDI <20 or meeting MCID, (2) mild myelopathy (mJOA≥14), and (3) NRS-Neck ≤5 or improved by ≥2 points from baseline. Within each distinct deformity group, patients with good outcomes were compared to those with poor outcomes (ie, not meeting the criteria for good) for differences in demographics, HRQOL scores, and alignment, via Chi-squared or student's t tests., Results: Overall, 83 of 153 patients met the criteria of severe CD and 40 patients had complete 1-year follow-up of clinical/radiographic data. Patient breakdown by deformity pattern was: CT (N=13), FN (N=17), and FD (N=17), with 7 patients meeting criteria for both FD and FN deformities. Within the FD cohort, maximal focal kyphosis (ie, kyphosis at one level) was better corrected in patients with a "good" outcome (p=.03). In the FN cohort, patients with "good" outcomes presented preoperatively with worse horizontal gaze (McGregor Slope 21° vs. 6°, p=.061) and cSVA (72 mm vs. 60 mm, p=.030). "Good" outcome FN patients showed significantly greater postop correction of horizontal gaze (-25° vs. -5°, p=.031). In the CT cohort, patients with "good" outcomes had superior global alignment both pre- (SVA: -17 mm vs. 108 mm, p<.001) and postoperatively (50 mm vs. 145 mm, p=.001). CT patients with "good" outcomes also had better postop cervical alignment (cSVA 35 mm vs. 49 mm, p=.030), and less kyphotic segments during extension (p=.011). In the FD cohort, there were no differences between "good" and "poor" outcomes patients in preoperative alignment; however, "good" outcome patients showed superior changes in postoperative focal kyphosis (-2° vs. 5°, p=.030). Within all three deformity pattern categories, there were no differences between "good" and "poor" outcome patients with respect to demographics or surgical parameters (levels fused, surgical approach, decompression, osteotomy, all p>.050)., Conclusions: The results of this study show each CD patient's unique deformity must be carefully examined in order to determine the appropriate alignment goals to achieve optimal HRQOLs. In particular, the recognition of the sagittal morphotype can help assist surgeons to aim for specific alignment goals for CT, FN and FD. Distinct deformity specific intra-operative goals include obtaining proper sagittal global/cervical alignment for cervicothoracic patients, correcting maximal focal kyphosis in focal deformity patients, and correcting horizontal gaze for flatneck patients., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background Context: A variety of solutions have been suggested as candidates for the repair of the annulus fibrosis (AF), with the ability to withstand physiological loads of paramount importance., Purpose: The objective of our study was to capture the scope of biomechanical test models of AF repairs. We hypothesized that common test parameters would emerge., Study Design: Systematic Review METHODS: PubMed and EMBASE databases were searched for studies in English including the keywords "disc repair AND animal models," "disc repair AND cadaver spines," "intervertebral disc AND biomechanics," and "disc repair AND biomechanics." This list was further limited to those studies which included biomechanical results from annular repair in animal or human spinal segments from the cervical, thoracic, lumbar and/or coccygeal (tail) segments. For each study, the method used to measure the biomechanical property and biomechanical test results were documented., Results: A total of 2,607 articles were included within our initial analysis. Twenty-two articles met our inclusion criteria. Significant variability in terms of species tested, measurements used to quantify annular repair strength, and the method/direction/magnitude that forces were applied to a repaired annulus were found. Bovine intervertebral disc was most commonly used model (6 of 22 studies) and the most common mechanical property reported was the force required for failure of the disc repair device (15 tests)., Conclusions: Our hypothesis was rejected; no common features were identified across AF biomechanical models and as a result it was not possible to compare results of preclinical testing of annular repair devices. Our analysis suggests that a standardized biomechanical model that can be repeatably executed across multiple laboratories is required for the mechanical screening of candidates for AF repair., Clinical Significance: This literature review provides a summary of preclinical testing of annular repair devices for clinicians to properly evaluate the safety/efficacy of developing technology designed to repair annular defects after disc herniations., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Spinal fusion surgery is performed all over the world to help patients with cervical and thoracolumbar pathology. As outcomes continue to improve in patients with spine-related pathology, it is important to understand how we got to modern day spinal fusion surgery. Scientific innovations have ranged from the first spinal fusions performed with basic instrumentation in the late nineteenth century to contemporary tools such as pedicle screws, bone grafts, and interbody devices. This article tracks this technological growth so that surgeons may better serve their patients in treating spine-related pain and disability., Competing Interests: Conflicts of InterestSohrab Virk, MD, MBA, declares no conflicts of interest. Sheeraz Qureshi, MD, MBA, reports consulting fees from Stryker, Globus Medical, Inc., and Paradigm Spine; royalties from RTI, Globus Medical, Inc., and Stryker; ownership interest in Avaz Surgical and Vital 5; medical/scientific advisory board membership at Spinal Simplicity and Lifelink.com; board membership at Healthgrades and the Minimally Invasive Spine Study Group; and honoraria from AMOpportunities, outside the submitted work. Harvinder Sandhu, MD, reports personal fees from Biorestorative Therapies and Prosidyan Medical and stock or stock options from Amedica, Biorestorative Therapies, Paradigm Spine, Prosydian Medical, and Spinewave, outside the submitted work., (© Hospital for Special Surgery 2020.)

Objective: Our aim was to define a treatment strategy for patients with severe cervical deformity (sCD)., Methods: Surgical patients with sCD were isolated based on preoperative radiographic parameters. We sent 10 sCD cases to 7 surgeons to find consensus on approach, upper instrumented vertebrae (UIVs), lower instrumented vertebrae (LIVs), and osteotomy. We performed a descriptive analysis and created a treatment algorithm from the survey and then analyzed a database of surgical patients to find the frequency of following our algorithm., Results: We found consensus on 7 cases for a posterior approach because of cervicothoracic deformity. Of 15 patients within our sCD database that had cervicothoracic deformity, 13 had a posterior approach. There was consensus on 2 cases for an anteroposterior approach because of local kyphosis. Of 25 patients that had local kyphosis, 18 had an anterior approach. In 4 cases, there was consensus of UIV of C2. Of 35 cases that had posterior fusion more than 6 levels, 20 had UIV of C2. In 3 cases, there was consensus of LIV below a previously fused spine. Of 36 patients that had a fusion of T6 or higher, 34 had LIV below the previous UIV. In 6 cases, there was consensus against an osteotomy because of cervical spine flexibility. Nine of 12 patients that had an osteotomy in our database had no flexibility on dynamic radiographs., Conclusions: We outline an algorithm for deciding approach, UIV, LIV, and whether to do an osteotomy for patients with sCD based on consensus recommendations among spine surgeons., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: As the frequency of adult deformity surgery (ADS) continues to increase, our understanding of techniques that enhance fusion must continue to evolve because pseudarthrosis can be a serious and costly event., Purposes/questions: We sought to conduct a review of the literature investigating techniques that can enhance outcomes of ADS., Methods: Two databases were searched for keywords such as "advances in spinal fusion," "new technology in adult spinal deformity," "interbody devices for adult spinal deformity," "adult spinal deformity rods," and "screw design in adult spinal deformity" to examine recent literature and trends in ADS., Results: We identified 45 articles for our review. Topics studied include the use of multiple rods, interbody fusion, distal fixation techniques, and bone morphogenetic protein or iliac crest bone graft., Conclusions: Many recent innovations in treatments to enhance fusion in ADS have been studied, some more controversial than others. Further research into the efficacy of these techniques may increase fusion rates in ADS., Competing Interests: Conflict of InterestJeremy Steinberger, MD, Philip York, MD, and Sohrab Virk MD, MBA, declare that they have no conflicts of interest. Han Jo Kim, MD, reports personal fees from K2M and Zimmer Biomet and advisory board membership from AOSpine, outside the submitted work., (© Hospital for Special Surgery 2020.)

Background: Lumbar interbody fusion is among the most common types of spinal surgery performed. Over time, the term has evolved to encompass a number of different approaches to the intervertebral space, as well as differing implant materials. Questions remain over which approaches and materials are best for achieving fusion and restoring disc height., Questions/purposes: We reviewed the literature on the advantages and disadvantages of various methods and devices used to achieve and augment fusion between the disc spaces in the lumbar spine., Methods: Using search terms specific to lumbar interbody fusion, we searched PubMed and Google Scholar and identified 4993 articles. We excluded those that did not report clinical outcomes, involved cervical interbody devices, were animal studies, or were not in English. After exclusions, 68 articles were included for review., Results: Posterior approaches have advantages, such as providing 360° support through a single incision, but can result in retraction injury and do not always restore lordosis or correct deformity. Anterior approaches allow for the largest implants and good correction of deformities but can result in vascular, urinary, psoas muscle, or lumbar plexus injury and may require a second posterior procedure to supplement fixation. Titanium cages produce improved osteointegration and fusion rates but also increase subsidence caused by the stiffness of titanium relative to bone. Polyetheretherketone (PEEK) has an elasticity closer to that of bone and shows less subsidence than titanium cages, but as an inert compound PEEK results in lower fusion rates and greater osteolysis. Combination PEEK-titanium coating has not yet achieved better results. Expandable cages were developed to increase disc height and restore lumbar lordosis, but the data on their effectiveness have been inconclusive. Three-dimensionally (3D)-printed cages have shown promise in biomechanical and animal studies at increasing fusion rates and reducing subsidence, but additive manufacturing options are still in their infancy and require more investigation., Conclusions: All of the approaches to spinal fusion have plusses and minuses that must be considered when determining which to use, and newer-technology implants, such as PEEK with titanium coating, expandable, and 3D-printed cages, have tried to improve upon the limitations of existing grafts but require further study., Competing Interests: Conflict of InterestRavi Verma, MD, MBA, and Sohrab Virk, MD, MBA, declare that they have no conflicts of interest. Sheeraz Qureshi, MD, MBA, reports receiving consulting fees or royalties from Stryker, K2M, Paradigm Spine, Globus Medical, Medical Device Business Services, and Pacira Pharmaceuticals; owning shares of Avaz Surgical and Vital 5; and receiving royalties from RTI and Zimmer Biomet, outside the submitted work., (© Hospital for Special Surgery 2020.)

The biologic steps involved in creating a bony fusion between adjacent segments of the spine are a complex and highly coordinated series of events. There have been significant advancements in bone grafts and bone graft substitutes in order to augment spinal fusion. While autologous bone grafting remains the gold standard, allograft bone grafting, synthetic bone graft substitutes, and bone graft enhancers are appropriate in certain clinical situations. This article provides an overview of the basic biology of spinal fusion and strategies for enhancing fusion through innovations in bone graft material., Competing Interests: Conflict of Interest: Yoshihiro Katsuura, MD, Karim Shafi, MD, Chelsie Jacques, BS, Sohrab Virk, MD, MBA, declare that they have no conflict of interest. Sravisht Iyer, MD, reports personal fees from Globus Medical, outside the submitted work. Matthew Cunningham, MD, PhD, reports material support from DePuy Synthes, outside the submitted work., (© Hospital for Special Surgery 2020.)

Objective: Cervical deformity (CD) is difficult to define due to the high variability in normal cervical alignment based on postural- and thoracolumbar-driven changes to cervical alignment. The purpose of this study was to identify whether patterns of sagittal deformity could be established based on neutral and dynamic alignment, as shown on radiographs., Methods: This study is a retrospective review of a prospective, multicenter database of CD patients who underwent surgery from 2013 to 2015. Their radiographs were reviewed by 12 individuals using a consensus-based method to identify severe sagittal CD. Radiographic parameters correlating with health-related quality of life were introduced in a two-step cluster analysis (a combination of hierarchical cluster and k-means cluster) to identify patterns of sagittal deformity. A comparison of lateral and lateral extension radiographs between clusters was performed using an ANOVA in a post hoc analysis., Results: Overall, 75 patients were identified as having severe CD due to sagittal malalignment, and they formed the basis of this study. Their mean age was 64 years, their body mass index was 29 kg/m2, and 66% were female. There were significant correlations between focal alignment/flexibility of maximum kyphosis, cervical lordosis, and thoracic slope minus cervical lordosis (TS-CL) flexibility (r = 0.27, 0.31, and -0.36, respectively). Cluster analysis revealed 3 distinct groups based on alignment and flexibility. Group 1 (a pattern involving a flat neck with lack of compensation) had a large TS-CL mismatch despite flexibility in cervical lordosis; group 2 (a pattern involving focal deformity) had focal kyphosis between 2 adjacent levels but no large regional cervical kyphosis under the setting of a low T1 slope (T1S); and group 3 (a pattern involving a cervicothoracic deformity) had a very large T1S with a compensatory hyperlordosis of the cervical spine., Conclusions: Three distinct patterns of CD were identified in this cohort: flat neck, focal deformity, and cervicothoracic deformity. One key element to understanding the difference between these groups was the alignment seen on extension radiographs. This information is a first step in developing a classification system that can guide the surgical treatment for CD and the choice of fusion level.

Purpose: This study aimed to define the footprint of the direct and reflected heads of the rectus femoris and the relation of the anterior inferior iliac spine (AIIS) to adjacent neurovascular (lateral circumflex femoral artery and femoral nerve), bony (anterior superior iliac spine [ASIS]), and tendinous structures (iliopsoas)., Methods: Twelve fresh-frozen cadaveric hip joints from 6 cadavers, average age of 44.5 (±9.9) years, were carefully dissected of skin and fascia to expose the muscular, capsular, and bony structures of the anterior hip and pelvis. Using digital calipers, measurements were taken of the footprint of the rectus femoris on the AIIS, superior-lateral acetabulum and hip capsule, and adjacent anatomic structures., Results: The average dimensions of the footprint of the direct head of the rectus femoris were 13.4 mm (±1.7) × 26.0 mm (±4.1), whereas the dimensions of the reflected head footprint were 47.7 mm (±4.4) × 16.8 mm (±2.2). Important anatomic structures, including the femoral nerve, psoas tendon, and lateral circumflex femoral artery, were noted in proximity to the AIIS. The neurovascular structure closest to the AIIS was the femoral nerve (20.8 ± 3.4 mm)., Conclusions: The rectus femoris direct and reflected heads originate over a broad area of the anterolateral pelvis and are in close proximity to critical neurovascular structures, and care must be taken to avoid them during hip arthroscopy., Clinical Relevance: A thorough knowledge of the anatomy of the proximal rectus femoris is valuable for any surgical exposure of the anterior hip joint, particularly arthroscopic subspine decompression and open femoroacetabular impingement (FAI) surgery., (Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Evaluation of new technology in sports medicine is supposed to promote improvements in the care of patients. It is also supposed to prohibit technology that can harm patients. This evaluation process is not perfect and at times can promote technology that not only does not help patients but may harm them. Two examples of new sports medicine technology that were widely adopted but eventually abandoned are thermal capsulorrhaphy for treatment of shoulder instability and the Gore-Tex prosthetic ligament (W. L. Gore & Associates, Flagstaff, AZ) for patients with anterior cruciate ligament deficiency. On analysis of the quick adoption of these 2 failed procedures, certain recommendations are apparent for improvement of the evaluation process. There must be a sound rationale behind any new technology, basic science research into the theory of the medical technology, and demonstrated improvements in animal models and clinical studies that are prospective cohort studies or randomized controlled trials, and finally, there must be careful follow-up and postmarket surveillance., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)