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BACKGROUND CONTEXT Posterior cervical fusion (PCF) is successfully used to treat cervical spondylotic myelopathy, multilevel cervical stenosis, and cervical deformity. However, limited evidence exists regarding the appropriate level of proximal and distal extension of PCF constructs. Further investigation is required to understand the effects of construct endpoint on fusion rate, junctional failure, and sagittal deformity correction. PURPOSE To compare the surgical and radiographic outcomes of patients undergoing posterior cervical fusion (PCF) with constructs extending from C2-T2 to patients with constructs extending from C3-T1. STUDY DESIGN/SETTING This was a multicenter retrospective review of two prospective cohorts of patients undergoing PCF from C2-T2 or C3-T1 for subaxial cervical stenosis at two academic institutions from 2012 to 2020. PATIENT SAMPLE We identified 106 patients for inclusion in the C2-T2 cohort and 49 patients for inclusion in the C3-T1 cohort. OUTCOME MEASURES Pre- and postoperative cervical alignment parameters, distal screw loosening, distal junctional failure, and pseudarthrosis were measured. Methods Cervical alignment parameters were measured on both preoperative and postoperative radiographs performed greater than 6 months postoperatively. The cohorts were compared based on preoperative cervical alignment, postoperative cervical alignment, and change in cervical alignment. Postoperative radiographs were also assessed for signs of distal screw loosening, distal junctional failure, and pseudarthrosis. We utilized Student's t-test to compare all means between groups with p Results A total of 155 patients were included in the study (C2-T2: 106 patients, C3-T1: 49 patients). There were no significant differences in demographics or preoperative symptoms between cohorts. Fusion rates were significantly higher in the C2-T2 (93%) than the C3-T1 (80%, p=0.040) cohort. When comparing the C2-T2 to the C3-T1 cohort, the C3-T1 cohort had a significantly greater rate of proximal junctional failure (2% vs 10%, p=0.006), distal junctional failure (1% vs 20%, p Conclusions In patients undergoing PCF, a C2-T2 construct demonstrated lower rates of pseudarthrosis, DJF, PJF, and compensatory upper cervical hyperextension compared to a C3-T1 construct. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Studies in the lumbar spine suggest a correlation between sarcopenia and worse patient outcomes. To our knowledge, no studies have investigated whether an association exists between fatty degeneration of the cervical paraspinal musculature and cervical disability in the perioperative period. PURPOSE The purpose of this study is to determine whether paraspinal Goutalier grade of fat degeneration is associated with patient-reported outcomes in patients undergoing ACDF. STUDY DESIGN/SETTING Retrospective review of a prospectively collected cohort of patients who underwent 1 to 3 level ACDF between the years 2011-2014 at a single academic medical center. PATIENT SAMPLE Sixty-nine patients who underwent 1-3 level ACDF between the years of 2011-2014. OUTCOME MEASURES Goutalier classification, patient-reported outcomes such as neck disability index (NDI), RAND score, and EQ-5D score were measured. METHODS We performed a retrospective review of a prospective cohort of patients undergoing 1 to 3 level ACDF at a single institution between the years 2011-2014. We utilized preoperative MRI's to classify patients into Goutalier grades. Patient-reported outcomes including NDI, RAND score and EQ-5D score were collected and analyzed according to patients’ Goutalier grade. We utilized Student's t-test and ANOVA to compare all means between groups. The mid-P exact test was used to compare proportional differences between groups. RESULTS We identified 69 patients for inclusion. The cohort was 47.3% male. 29 patients were classified as Goutalier 0-1 (Group 1), 29 were Goutalier 1.5-2 (Group 2), and 11 were Goutalier 2.5-4.0 (Group 3). Determination of Goutalier grade by the two reviewers resulted in 82.8% agreement with correlation coefficient of 0.69 (Pearson, r2), demonstrating moderate interrater reliability. All Goutalier groups experienced significant improvement in all three outcome scores. Average postoperative NDI scores were 25.3 in Group 1, 13.9 in Group 2, and 25.1 in Group 3 (p=0.02). The percentage of patients in each group reporting worse disability after surgery was 17.2%, 3.3% and 9.1%, respectively (p=0.05) No statistically significant difference was seen between groups in postoperative EQ-5D (p=0.07) or RAND scores (p>0.05). CONCLUSIONS The present study is the first to assess the association between cervical paraspinal muscle Goutalier grade and patient reported outcomes following ACDF. Based upon our study, patients with worse cervical paraspinal degeneration may benefit from improved symptom relief in comparison to patients with a lesser degree of degeneration undergoing ACDF. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Background Context Lumbar epidural corticosteroid injections (LECIs) are frequently used in the treatment of lumbar intervertebral disc herniation with radiculopathy and lumbar spinal stenosis. Although widely used, their effect on the outcomes and complications of subsequent surgery is unclear. Postoperative infection can be a morbid complication following spine surgery, and recent literature has suggested that the risk may be increased in patients undergoing lumbar spinal surgery who had previously received LECIs. Purpose The purpose of this study is to define the overall postoperative infection rate in patients undergoing lumbar spine decompression surgery in the Military Health System (MHS) patient population and examine the effects of LECIs on postoperative infection rates. Study Design/Setting This is a retrospective case control database study (Level III study). Patient Sample The sample comprised all patients in the MHS who had a LECI before single-level lumbar decompression surgery from 2009 to 2014. Outcome Measures Postoperative infection within 90 days of surgery was used as the primary outcome measure for this study. Postoperative infection was identified using the International Classification of Diseases, 9th revision (ICD-9) diagnosis codes for postoperative infection. Methods The Military Health System Data Repository (MDR) database was searched for all patients who underwent single-level lumbar spine decompression surgery from 2009 to 2014 using Current Procedural Terminology (CPT) codes. Current Procedural Terminology codes were used to identify the subset of patients who received preoperative LECIs. For patients receiving an injection, cohorts were established based on the timing of the preoperative injection: 365 days. An age-based cohort, composed of patients 65 years of age and older, was also analyzed. A subgroup analysis of patients receiving more than one preoperative injection was performed. Postoperative infection within 90 days of surgery was identified using ICD-9 codes, and infection rates for all groups were calculated and compared with the control group who did not receive preoperative LECIs. No external funding was received for this study. Results We identified 6,535 patients (847 preoperative LECI and 5,688 control) for analysis. The overall infection rate for patients undergoing single-level lumbar decompression surgery in the MHS was 0.81%. The rate ranged from 0% to 1.57% in the injection groups, with an overall infection rate in the injection group of 1.18% versus 0.76% in the control group. Despite an increased odds ratio of 1.57 following injection, no statistically significant differences were found between the control group and any injection group based on timing of injection, patient age, or number of preoperative injections. Conclusions The results of this study suggest that within the MHS, preoperative LECIs do not significantly increase the risk of postoperative infection after single-level lumbar decompression. If a difference does exist, it is likely small.

BACKGROUND CONTEXT The clinical syndrome of radiculopathy from lumbar disc herniation (LDH) is a major cause of morbidity and cost among United States civilians and active duty service members. LDH is one of the most common diagnoses in spine practice with the incidence of incidence of symptomatic LDH in the United States estimated at 1% to 2%. PURPOSE The purposes of this study were to determine survival of conservative management of lumbar disc herniation in the military health system (MHS), and to determine risk factors to fail conservative management amongst MHS beneficiaries. STUDY DESIGN/SETTING After IRB approval we performed a retrospective observational review of Military Health System (MHS) beneficiaries. PATIENT SAMPLE The Military Heath System Data Repository (MDR) contains patient specific detail on all health care beneficiaries including active duty service members, dependents and retirees. In this set of patients, we then identified patients that failed conservative management, finding the time to the first post-diagnosis encounter for lumbar microdiscectomy or lumbar decompression. OUTCOME MEASURES Multivariable Cox proportional hazards models were used to evaluate the associations of patient and diagnosing facility characteristics with time to surgical intervention over the study period. METHODS The MDR was queried for all patients diagnosed with lumbar disc herniation from FY2011-2018; the earliest such diagnosis was kept for each patient as the initial diagnosis. Censoring was determined to be the first day of the last month each patient was eligible to receive MHS benefits. Patients were also queried for history of smoking status (yes/no) at any time during MHS care, age at the time of diagnosis, sex, MHS beneficiary category, and the skill/training of the diagnosing provider. RESULTS A total of 84,985 MHS beneficiaries including 62,771 active duty service members were diagnosed with LDH in a military treatment facility during the study period. 10,532 (12.4%) MHS beneficiaries, including 7,650 (10.9%) active duty service, failed conservative management onto surgical intervention with lumbar microdiscectomy or lumbar decompression. Multivariable Cox regression among all health care beneficiaries revealed that younger age, male sex, and history of smoking were each associated with higher risk of surgical intervention independent of diagnosing facility characteristics. CONCLUSIONS LDH compromises the readiness of our troops and negatively impacts healthcare costs for the Department of Defense (DoD). MHS beneficiaries with LDH have a good prognosis with approximately 88% of patients successfully completing conservative management. However, younger patients with a history of smoking should be educated that they are more likely to fail conservative management than patients without those demographic features. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT The surgical management of adult spinal deformity (ASD) presents a difficult challenge for spine surgeons and is associated with a high complication profile in the postoperative period. Particularly, junctional failure is a major postoperative complication that necessitates revision. Little is known about risk factors for distal junctional failure (DJF) compared to proximal junctional failure (PJF). PURPOSE The aim of this study is to identify risk factors associated with postoperative DJF in long constructs for ASD. STUDY DESIGN/SETTING A retrospective review was performed at a tertiary referral spine center. PATIENT SAMPLE Patients who underwent long construct fixation at our institution from 1st Jan 2007 to 31st December 2016. OUTCOME MEASURES Evaluate demographic, clinical, and radiological risk factors for postoperative occurrence of distal junctional failure in ASD patients. Additionally, assess the incidence rate and causative pathophysiology for DJF in these patients. METHODS Demographic, clinical and radiographic parameters were collated for patients with DJF in the postoperative period and compared to those without DJF. Survival analyses were performed using univariate logistic regression to identify variables with a p-value RESULTS A total of 102 patients were identified. Forty-one (40.2%) suffered DJF in the postoperative period, with rod fracture being the most common sign of DJF (13/65; 20.0%). Mean time to failure was 32.4 months. On univariate analysis, pedicle subtraction osteotomy (p=0.03), transforaminal lumbar interbody fusion (p CONCLUSIONS Recently, DJF has received recognition as its own entity due to a notable postoperative incidence. Few studies to date have evaluated risk factors for DJF. The results of our study highlight that pedicle subtraction osteotomy and poor correction of lumbar lordosis and sagittal vertical axis are significantly associated with postoperative occurrence of DJF. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Studies investigating the impact of interbody subsidence in ACDF suggest a correlation between subsidence and worse radiographic and patient-reported outcomes. Though some interbody subsidence is anticipated, a normal range of subsidence has yet to be defined. Furthermore, no study has investigated the variables influencing allograft subsidence in ACDF. PURPOSE The primary purpose of this study was to utilize computed tomography to characterize subsidence of allograft interbodies in ACDF. The secondary aim of this study was to determine the impact of patient- and graft-related variables on subsidence in ACDF. STUDY DESIGN/SETTING This was a retrospective study conducted at a single academic medical center. PATIENT SAMPLE Adult patients who underwent a 1 to 3 level ACDF with an allograft interbody and anterior plating between 2011-2017 were included. A total of 98 patients were included in the study. OUTCOME MEASURES Outcome measurements included superior endplate subsidence, inferior endplate subsidence, VAS scores, pseudoarthrosis, and reoperation rates. METHODS We performed a retrospective review of a prospective cohort of patients undergoing 1 to 3 level ACDF with an allograft interbody and anterior plating at a single institution between the years of 2011-2017. We collected demographic information, radiographic variables, and graft-related parameters. Graft subsidence was assessed on CT scan performed at least 6 months postoperatively. We classified subsidence as none if 4mm. Student's t-test and ANOVA were used to compare all means between groups. RESULTS We identified 98 patients (152 levels) for inclusion. On sagittal CT for the entire cohort, the mean superior endplate subsidence was 1.62mm+/-0.90 and the mean inferior endplate subsidence was 1.62mm+/-0.91. The number of levels that underwent 2mm, and >4mm of subsidence was 73 (48.0%), 79 (51.9%), and 18 (11.8%), respectively. Of the 18 levels with severe subsidence, 14 occurred in multi-level constructs, 2 of which occurred in both levels of a two-level ACDF in one patient. Of the remaining 12 levels of severe subsidence, 11 (92%) occurred at the caudal level and to a significantly higher degree at the inferior end plate (p 0.05). 16 patients (94.1%) with severe subsidence experienced pseudarthrosis compared to only 11 patients (13.6%) with CONCLUSIONS The present study is the first to utilize advanced imaging to quantify and characterize allograft subsidence in ACDF. Univariate analysis of patients with severe subsidence demonstrated that inferior screw placement in the caudal instrumented vertebra was associated with increased subsidence, likely due to decreased buttress support and an increased working length with an associated decrease in construct rigidity. Furthermore, excessive endplate resection was associated with an increase in both mild and severe subsidence. Based upon our study, some allograft subsidence in ACDF is expected, but too inferior screw placement at the caudal vertebral level and excessive endplate resection should be avoided to prevent severe subsidence. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Postoperative subsidence of transforaminal lumbar interbody fusion (TLIF) interbody cages can result in loss of lordosis and foraminal height, and in some cases recurrence of nerve root impingement and radicular symptoms. Hounsfield unit (HU) values as measured on computed tomography (CT) can be used in the assessment of bone quality and bone mineral density. PURPOSE Determine the association between HU measurement of the first lumbar vertebral body and cage subsidence after TLIF. We hypothesized that the HU measured in the vertebral body of L1 would be lower in patients with postoperative TLIF cage subsidence. STUDY DESIGN/SETTING Retrospective case-control study. PATIENT SAMPLE NA OUTCOME MEASURES NA METHODS We retrospectively reviewed all patients undergoing instrumented TLIF from two institutions between July 2004 and June 2014. Postoperative imaging studies (radiographs and CT) were evaluated for evidence of implant subsidence. Hounsfield unit values were obtained from the first lumbar vertebral body on postoperative CT scan. Primary outcomes of this study were presence of cage subsidence and measured HU value of first lumbar vertebral body. RESULTS We identified 89 patients with complete imaging who met our inclusion criteria, with a mean clinical follow up of 27 months. Forty-five patients (50.5%) had evidence of interbody cage subsidence. Average cage subsidence was 5.5mm, with a range of 2.2 to 10.8mm. We found implant height was significantly higher in the subsidence group (12.6mm) when compared to the nonsubsidence group (11.2mm). First lumbar vertebral body coronal (170.69±15.61 vs 138.64±14.21; P=0.003), sagittal (175.14±17.26 vs 140.16±13.71; P=0.002), axial (157.57±12.26 vs 134.35±12.30.83; P=0.009), and average HU (167.8±14.04 vs 137.71±12.83; P=0.002) were significantly higher in the non-subsided group vs subsided group (167.8±14.04 vs 137.71±12.83; P=0.002). The subsidence group had a fusion rate of 82% compared to 93% in the nonsubsidence group, although this finding did not reach statistical significance (p=0.08). CONCLUSIONS We found that HU measurements of the first lumbar vertebra are significantly higher in patients without evidence of TLIF cage subsidence when compared to patients with cage subsidence. We identified a trend toward a decreased fusion rate in the subsidence group, yet this finding was not statistically significant. Our findings suggest that HU measurements may function as a surrogate measurement for bone mineral density, and as a predictor for cage subsidence following TLIF. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Despite advances in surgical techniques, rates of recurrent lumbar disc herniation (LDH) range from 5-24%, representing the most common cause of surgical failure and subsequent reoperation. PURPOSE Our goal was to determine the reoperation rate, time to reoperation and type of revision procedures performed after single-level discectomy for LDH within the military health system. STUDY DESIGN/SETTING Restrospective. PATIENT SAMPLE Military health system. METHODS Using CPT codes to capture lumbar microdiscectomy procedures, 3,999 patients undergoing primary single-level microdiscectomy for lumbar disc herniation were identified between October 2012 and November 2017. Demographic data, as well as number and type of revision surgical intervention were investigated. Rates of subsequent procedures involving instrumented fusion and complications were recorded. RESULTS We identified 415 patients (10.3%) who required a revision surgery for a same-level reherniation. Of these patients requiring revision surgery at the same level of the index procedure, 9.3% required more than one revision surgery. The majority of first-time revision procedures consisted of revision microdiscectomy (290/415, 69.9%); however, 125 patients (30.1%) underwent single- or multi-level fusion for definitive treatment at time of first revision. Of the 40 patients requiring more than one revision, 21 (52.5%) eventually required a fusion procedure, which was significantly higher than patients having only one revision (p= CONCLUSIONS In our retrospective study of 3,999 patients undergoing single-level microdiscectomy for lumbar disc herniation, we identified 415 patients (10.4%) undergoing subsequent reoperation for a recurrent LDH at the same level. Within this group, 9.6% would require two or more reoperations, and 52.5% of these patients would ultimately undergo a lumbar arthrodesis at the same level as the initial disc herniation. Our findings characterize the lumbar disc reherniation population in the military, with major implications for the prognosis and treatment strategy of these commonly-treated injuries. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Background context Transforaminal lumbar interbody fusion (TLIF) is increasingly popular for the surgical treatment of degenerative lumbar disease. The optimal construct for segmental stability remains unknown. Purpose To compare the stability of fusion constructs using standard (C) and crescent-shaped (CC) polyetheretherketone TLIF cages with unilateral (UPS) or bilateral (BPS) posterior instrumentation. Study design Five TLIF fusion constructs were compared using finite element (FE) analysis. Methods A previously validated L3–L5 FE model was modified to simulate decompression and fusion at L4–L5. This model was used to analyze the biomechanics of various unilateral and bilateral TLIF constructs. The inferior surface of the L5 vertebra remained immobilized throughout the load simulation, and a bending moment of 10 Nm was applied on the L3 vertebra to recreate flexion, extension, lateral bending, and axial rotation. Various biomechanical parameters were evaluated for intact and implanted models in all loading planes. Results All reconstructive conditions displayed decreased motion at L4–L5. Bilateral posterior fixation conferred greater stability when compared with unilateral fixation in left lateral bending. More than 50% of intact motion remained in the left lateral bending with unilateral posterior fixation compared with less than 10% when bilateral pedicle screw fixation was used. Posterior implant stresses for unilateral fixation were six times greater in flexion and up to four times greater in left lateral bending compared with bilateral fixation. No effects on segmental stability or posterior implant stresses were found. An obliquely-placed, single standard cage generated the lowest cage-end plate stress. Conclusions Transforaminal lumbar interbody fusion augmentation with bilateral posterior fixation increases fusion construct stability and decreases posterior instrumentation stress. The shape or number of interbody implants does not appear to impact the segmental stability when bilateral pedicle screws are used. Increased posterior instrumentation stresses were observed in all loading modes with unilateral pedicle screw/rod fixation, which may theoretically accelerate implant loosening or increase the risk of construct failure.

Background context Deep surgical site infections (SSIs) following spinal surgery are a significant burden to the patient, patient's family, and the health-care system. Because of increasing pressures to reduce SSIs and control costs, some spine surgeons have begun placing lyophilized vancomycin powder directly into the surgical wound at the conclusion of the procedure. However, the literature supporting this practice remains limited. Purpose To review the current literature examining the use of prophylactic intrasite vancomycin powder to control SSIs in spinal surgery and determine if any standard recommendations can be made. Study design A systematic review. Methods Ovid Medline and PubMed were searched to identify English language articles. Results No current guidelines are available for the use of intrasite vancomycin powder in preventing SSIs, and no standard dosage for the drug exists. Based on the limited literature and evidence currently available, there appears to be a protective effect of intrasite vancomycin powder on the incidence of SSI, without evidence of side effects. However, case reports do exist describing the systemic side effects after intrasite vancomycin powder during spine surgery. Conclusions The interpretation of the available evidence supporting the use of intrasite vancomycin powder in surgical wounds is limited, and its extrapolation should be performed with caution. Despite the lack of significant high-quality evidence available in the literature, many surgeons have adopted this practice; anecdotally, it continues to provide protection from infection without apparent significant risk of side effects.

BACKGROUND CONTEXT Post-operative C5 palsy is a known complication following cervical decompression, occurring more frequently after posteriorly based procedures, but also occurring after approximately 2%–6% of anteriorly based surgeries. Although several risk factors for the development of a postoperative C5 palsy have been reported, including among others, excessive cord drift, change in overall cervical alignment, and increases in C4-5 intervertebral height, no consensus has emerged on definitive causation and the cause is likely multifactorial. PURPOSE To assess the rate of C5 palsy following anterior cervical decompression and fusion (ACDF) and determine whether any radiographic parameters can predict its occurance. STUDY DESIGN/SETTING Retrospective single institution, multisurgeon patient cohort. PATIENT SAMPLE A total of 226 patients who underwent ACDF between September 2015 and September 2016 were reviewed. The average age of the sample was 59years and 51% were female. A total of 122 patients were included in the final analysis. Patients were excluded if they underwent concomitant posterior surgery or corpectomy, if no postoperative motor strength was documented, or if radiographs were inadequate for accurate measurement. OUTCOME MEASURES The primary outcome measure was the development of a C5 palsy, defined as a decrease of at least one motor grade in deltoid and/or biceps brachii muscle function in the immediate postoperative period. Preoperative and immediate postoperative radiographs were reviewed to determine whether any parameters influenced the development of a C5 palsy. These parameters included: local (C4-5) cobb angle, C2-7 cobb angle, C2-7 sagittal vertical axis (SVA), C4-5 intervertebral height (measured from the superior endplate of C4 to the inferior endplate of C5), and C2-7 cervical height (measured from the superior endplate of C2 to the inferior endplate of C7). METHODS Patient demographic, surgical, and radiographic data was reviewed, including postoperative motor examination results and pre- and postoperative radiographs. Given the small sample size for the palsy group, Mann-Whitney U test was used to compare continuous variables between independent groups and Fisher's exact test was used to compare categorical variables between groups. RESULTS Seven patients developed a postoperative C5 palsy with an overall rate of 5.7%. There were no statistically significant differences in patient age, sex, or numbers of levels fused between the palsy and nonpalsy groups. Among all radiographic parameters evaluated, there were no statistically significant differences between the groups (p>.05). However, there was a trend toward increasing kyphosis within the palsy cohort compared to the nonpalsy cohort among the changes in C2-7 cobb angle (4.09°±10.2° of kyphosis vs. 1.25°±9.18° lordosis, p=.19), C4-5 cobb angle (3.04°±6.70° kyphosis vs. 2.91°±8.46° lordosis, p=.059), and SVA (8.46 mm±8.26vs. 5.31 mm±9.04, p=.32). There was marginal significance for increased change in C4-5 cobb angle predisposing toward palsy (1.24° vs. 4.01°, p=.059). There was also a nonsignificant trend toward increasing local (0.90 mm±6.95vs. 3.37 mm±5.46, p=.35) and overall intervertebral height (1.56 mm±10.34vs. 4.26 mm±7.54, p=.54) among the palsy versus nonpalsy groups, respectively. CONCLUSIONS In this single institution series, we identified a 5.7% postoperative C5 palsy rate following ACDF. Although some have suggested that certain radiographic parameters can predict the development of C5 palsy, in our series, we could not identify any radiographic parameters which increase this risk, including changes in overall cervical or local C4-5 alignment.

BACKGROUND CONTEXT Postoperative subsidence of the transforaminal lumbar interbody fusion (TLIF) cages can result in loss of lordosis and foraminal height, and in some cases recurrence of nerve root impingement and radicular symptoms. PURPOSE The purpose of this study is to determine factors associated with TLIF cage subsidence. Specifically, we sought to determine if preoperative disc height compared to cage height could be used to predict TLIF interbody cage subsidence. STUDY DESIGN/SETTING Retrospective case-control study. PATIENT SAMPLE We identified 127 patients with complete imaging who met our inclusion criteria, with a mean clinical follow up of 27 months. OUTCOME MEASURES The primary outcome of this study was presence of cage subsidence identified with radiograph or CT. METHODS We retrospectively reviewed all patients undergoing instrumented TLIF from two institutions between July 2004 and June 2014. Postoperative imaging studies (radiographs and CT) were evaluated for evidence of implant subsidence. Preoperative disc height was measured for the operative and adjacent level disc heights. The delta between cage height and disc heights were measured and compared between groups. RESULTS Fifty four patients (44.3%) had evidence of interbody cage subsidence. Average cage subsidence was 5.5mm, with a range of 2.2–10.8mm. We found implant height was significantly higher in the subsidence group (12.6mm) when compared to the nonsubsidence group (11.2mm). Additionally, the delta between cage height and preoperative disc height was significantly larger in the subsidence group delta (5.5mm vs. 3.9mm). Similarly, the delta between cage height and preoperative adjacent level disc height was also significantly larger (1.2mm vs. 3.8mm). CONCLUSIONS This study demonstrates that preoperative disc height and preoperative adjacent level disc height can be used to template TLIF cage height to potentially decrease rates of subsidence. Larger cages subsided more frequently than smaller cages. Patients with evidence of subsidence had larger deltas between cage height and preoperative disc height. Similarly, a significant difference existed if preoperative adjacent level disc height was compared to cage height. This demonstrates that preoperative imaging should be used for TLIF cage height templating to avoid subsidence.

BACKGROUND CONTEXT There has been increasing interest in examining the relationship of lumbar paraspinal muscle morphometry and outcomes after lumbar spinal surgery, as well as investigating any association between changes in paraspinal muscle density and low back pain.However, the relationship of the iliopsoas muscle to the posterior paraspinal muscles, and the effect of variation in psoas cross sectional area to lumbar disability in patients with degenerative spondylolisthesis, has not been extensively explored. PURPOSE We set out to compare the absolute psoas and paraspinal CSA in patients with degenerative lumbar spondylolisthesis and corresponding severe disability to similar patients with only mild or moderate disability. STUDY DESIGN/SETTING Retrospective cohort. PATIENT SAMPLE Inclusion criteria were any patient undergoing single level lumbar fusion for degenerative spondylolisthesis greater than 18 years of age at one institution, based on the ICD-9 code 721.42, with a preoperative lumbar spine MRI and completed preoperative patient-reported outcome scores. Patients under the age of 18 years, those lacking a preoperative lumbar spine MRI or completed preoperative patient-reported outcome scores, or those with a diagnosis other than degenerative lumbar spondylolisthesis were excluded from the study. METHODS We retrospectively reviewed the medical records of 101 patients undergoing lumbar fusion for degenerative spondylolisthesis. Patients were divided into Oswestry Disability Index (ODI) score 40 (severe disability, SD) groups. The total CSA of the psoas and paraspinal muscles were measured on preoperative magnetic resonance imaging (MRI). Student's t-test was used to compare continuous variables between groups. Multivariable logistic regression was performed analyzing the effects of ASA class, history of heart disease, smoking status and psoas CSA on lumbar disability. P RESULTS There were 37 patients in the SD group and 64 in the MMD group. Average age and body mass index were similar between groups. For the paraspinal muscles, average iliocostalis CSA was 1093.5mm2 versus 1192.2mm2 for the SD group versus the MMD group, respectively (p=.168). Similarly, the longissimus CSA was 685.8mm2 versus 764.8mm2 (p=.329), respectively, and the multifidus CSA was 499.1mm2 versus 526.0mm2 (p=.125), respectively. Psoas muscle CSA was significantly decreased in the SD group compared to the MMD group (1010.08mm2 vs. 1178.6mm2, p=.041). Multivariable logistic regression demonstrated that active smoking was independently associated with severe disability (OR=12.9, range: 1.19–140.2, p=.035), while psoas size in the upper quartile was significantly protective against severe disability (OR=0.13, range: 0.03–0.66, p=.013). CONCLUSIONS In patients with severe lumbar disability and a diagnosis of degenerative spondylolisthesis, when compared to similar patients with mild or moderate disability, we found significantly decreased absolute cross sectional area of the psoas muscle. In addition, multivariate analysis found that increased psoas CSA was significantly protective against severe lumbar disability. Our findings are suggestive of a potential association between psoas atrophy and worsening severity of lumbar disability.

BACKGROUND CONTEXT Postoperative C5 nerve root palsy is a known complication after decompressive cervical surgery, most commonly reported after posterior cervical decompression and fusion (PCDF). However, while the rate of C5 palsy after anterior cervical decompression and fusion (ACDF) is lower, the effect of increasing number of levels fused on the prevalence of C5 palsy is unclear. PURPOSE To examine the rate of C5 palsy after one-, two-, three- and four-level ACDF including the C4-5 level, without corpectomy, and without posterior decompression. STUDY DESIGN/SETTING Retrospective cohort. PATIENT SAMPLE Retrospective review of all anterior cervical discectomy and fusion patients at one institution over a 1 year period. OUTCOME MEASURES Manual motor testing grade. METHODS We performed a retrospective review of ACDFs performed at one institution by multiple surgeons between September 2015 and June 2016. Patient demographic and surgical information was reviewed, including postoperative motor examination results in the immediate postoperative period. C5 palsy was defined as motor decline of the deltoid muscle function by at least one level on standard manual muscle testing. Patients were excluded if undergoing concurrent posterior surgery or corpectomy, or if no postoperative motor strength was documented. Fisher's exact test was used to compare categorical variables between groups, and analysis of variance used to compare continuous variables. RESULTS We identified 226 patients undergoing single- or multilevel ACDF over the study time period, with a total of 196 meeting our inclusion criteria. Average age of all patients was 59.0 years and 49% were male, with no significant differences noted between groups undergoing single- or multilevel ACDF. Average follow up was 7 months. Ten patients developed postoperative C5 palsy, with an overall rate of 5.1%. There were no statistically significant differences in age, patient sex or numbers of levels fused between the palsy and no-palsy groups. We identified two C5 palsies in the single-level group (8.7%), two in the two-level group (3.1%), five in the three-level group (5.6%) and one in the four-level group (5.6%). These rates were not statistically significant between groups (p>.05). Six of the 10 patients with C5 palsy had complete recovery of final deltoid and/or biceps strength, while two patients had at least some level of strength recovery. Two patients had no measured improvement in C5 motor function by final follow up. CONCLUSIONS To our knowledge, no prior study has specifically compared the risk of C5 palsy between single- and multilevel ACDF when excluding corpectomy and posterior cervical cases. We found an overall C5 palsy rate of 5.1% for all patients undergoing one-, two-, three-, and four-level ACDF that included the C4-5 level at our institution. The rate of postoperative deltoid and/or biceps motor strength decline was lowest in the patients undergoing two-level ACDF and highest in the single-level group, but this finding did not reach statistical significance. Our rate of C5 palsy appears comparable to published literature.

BACKGROUND CONTEXT Lumbar microdecompression is one of the most common procedures in orthopedic spine surgery with an overall low complication and high satisfaction rate. The procedure is typically performed with visualization aids, either loupes or an operating room microscope. Several studies to date have investigated differences between these two magnification tools, with conflicting results. Some authors argue in favor of the microscope, citing improved visualization, better ergonomics and improved patient outcomes, while others argue that its use makes no clinical difference. These studies consist primarily of small patient cohorts numbering 50-100 subjects. PURPOSE The purpose of this study is to determine how the routine use of an operating room microscope during single level lumbar microdecompression impacts intraoperative and short-term surgical outcomes through an examination of the largest retrospective cohort to date. STUDY DESIGN/SETTING Retrospective review of American College of Surgeons National Surgical Quality Improvement Project (ACS-NSQIP) database. PATIENT SAMPLE A total of 43,948 patients who underwent single level lumbar microdecompression from 2005 to 2015. OUTCOME MEASURES Assessment of surgical benchmarks of operative time and length of hospital stay as well as differences in early (30 day) complication rates. The specific complications evaluated included the need for blood transfusion, return to the operating room, pulmonary embolism, deep venous thrombosis, sepsis, cerebrovascular accident, cardiac arrest, ventilator time greater than 48 hours, urinary tract infection, pneumonia, myocardial infarction, surgical site infections, and patient mortality. METHODS Using the ACS-NSQIP database, we identified all patients who underwent single level lumbar microdecompression (CPT 63030). They were divided into two cohorts, those cases that involved the use of an operating room microscope (CPT 69990), and those that did not. We compared intraoperative and postoperative procedural data as well as the incidences of local and systemic complications. RESULTS The ACS-NSQIP database identified 43,948 patients who underwent single level lumbar microdecompression from 2005 to 2015. Of that patient cohort 4,654 cases included the use of an operating room microscope. There were no clinically significant demographic differences between patient cohorts. We identified clinically important statistical differences in length of stay (1.37 vs. 1.75 days, p CONCLUSIONS The routine use of an operating room microscope in single level lumbar microdecompression does not affect short-term patient outcomes. Importantly, there is no difference in mean operative time or infection rate with the addition of a microscope. There is a statistically significant trend toward decreased length of stay and fewer blood transfusions in the microscope cohort; however, in the setting of a large database study and small absolute differences, the clinical implications of these findings are difficult to interpret. Based on these results, we conclude that the decision to use an operating room microscope in single level lumbar microdecompression should be left to the treating surgeon and based upon considerations of improvements in visualization, surgeon ergonomics and ability to educate surgical assistants. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Trauma, degenerative and neuromuscular deformities often require placement of implants into sacrum for construct stability. In these scenarios, fixation to the ilium if often added. To date, multiple studies have validated the correlation between Hounsfield units (HU) as measured on computed tomography (CT) and bone mineral density (BMD) on dual-energy X-ray absorptiometry (DXA) to assess bone quality and fracture risk. PURPOSE We sought to map the BMD of the iliosacral region at the S1 and S2 levels using HU. STUDY DESIGN/SETTING Observational. METHODS HU measurements taken from the anterior and posterior ilium, sacral ala and sacral body using a best fit circle encompassing a maximal amount of cancellous bone of 100 pelvic CT scans. Following the collection of all data points, an analysis of variance (ANOVA) model was created to test the means and standard deviations of each anatomic region. RESULTS The highest mean BMD was found in the following locations (in descending order): S1 sacral body (279.72 HU, 95% CI, 261.75-297.69), S1 anterior ilium (254.45 HU, 95% CI, 236.64-272.27), S2 anterior ilium (229.88 HU, 95% CI, 211.39-248.36), and the S2 sacral body (191.58 HU, 95% CI, 173.31-209.85). Comparing the anterior ilium to the sacral ala, there was a higher BMD measurement at both the S1 level by 151.7 HU (p CONCLUSIONS The findings indicate that there is significantly higher BMD of the anterior ilium and sacral body when compared to the sacral ala at both the S1 and S2 levels. Given this, fixation through the lumbopelvic region should include implant placement within the anterior ilium and/or the sacral body to ensure fixation through densest cancellous bone. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

COMMENTARY ON Goode AP, Richardson WJ, Schectman RM, Carey TS. Complications, revision fusions, readmissions, and utilization over a 1-year period after bone morphogenetic protein use during primary cervical spine fusions. Spine J 2014;14:2051-9 ( in this issue ).

BACKGROUND CONTEXT Cervical radiculopathy secondary to cervical spondylosis can manifest as pain, sensory disturbance, and/or motor deficit. While preoperative weakness is often used as an indication for early surgical intervention, few studies have examined the prognosis for upper extremity motor deficit following anterior cervical discectomy and fusion (ACDF). PURPOSE To determine the prognosis for motor recovery after anterior cervical discectomy and fusion in patients with preoperative motor weakness. STUDY DESIGN/SETTING Retrospective cohort. PATIENT SAMPLE Consecutive patients undergoing elective ACDF from September 2015 until June 2016. OUTCOME MEASURES Postoperative motor strength in all affected myotomes. METHODS We retrospectively examined a cohort of 618 consecutive patients that underwent elective ACDF from September 2015 until June 2016. Cases were performed by ten fellowship trained spine surgeons at our tertiary academic center. Data was collected regarding patient demographics and comorbidities. Cervical magnetic resonance imaging imaging was reviewed for the presence of cord compression, myelomalacia, and foraminal stenosis. Patients were divided into a group exhibiting significant preoperative weakness (Medical Research Council motor grade less than 4) and a group without significant weakness. Data regarding affected muscle groups and significant improvement postoperatively (to a motor grade 4 or greater) was recorded. Univariate analysis was performed to determine risk factors for failure to improve. RESULTS Overall, out of the 618 patients, 47.5% were male with an average age of 56.3years. 43.0% of patients exhibited myeloradiculopathy with 57% having exclusively cervical radiculopathy. Of those patients with myelopathy and cord compression, 40.5% demonstrated myelomalacia on cervical MRI. Average follow up was 6.2 months. Two-level fusions were most commonly performed (44.6%) followed by one-level (29.3%), three-level (21.7%), and four-level (4.4%) fusions. A total of 4.3% of patients demonstrated significant preoperative weakness. Of these patients, 57.1% of them had more than one muscle group affected. Triceps were the most commonly affected muscle group (26.9%) followed by hand intrinsics (23.1%), finger flexors (20.5%), deltoids (15.4%), and biceps (14.1%). Postoperatively, 75.3% of patients experienced an improvement in muscle strength (≥4). Despite being the most commonly weak muscle preoperatively, triceps most frequently showed improvement (95.2%) followed by finger flexors (87.5%), hand intrinsics (83.3%), and biceps (63.6%). Deltoids were much less likely to show improvement following surgery (8.3%). In a univariate analysis, myelomalacia on imaging (OR 28.9, p CONCLUSIONS This cohort's outcomes would suggest with intermediate follow up one can expect the vast majority (over 70%) of patients to show marked strength improvement postoperatively after ACDF. These results are encouraging for patients undergoing ACDF with significant preoperative motor weakness. However, patients with myelomalacia seem to be at risk for not improving, and should be counseled that their prognosis for strength improvement is more guarded.

BACKGROUND CONTEXT Osteoporosis remains a major cause of morbidity and mortality, despite increasing efforts among provider organizations to promote awareness and screening. Recent attention has turned to the opportunistic utilization of Hounsfield unit (HU) measurements from computed tomography (CT) as a potential screening method for low bone mineral density (BMD). We hypothesized that thoracic spine CT HU measurements will correlate with BMD measurements conducted with dual X-ray absorptiometry (DXA) scans of the femoral neck. PURPOSE To compare thoracic spine HU and femoral neck T-scores determined by DXA, and determine the accuracy with which thoracic HU values estimate central BMD. STUDY DESIGN/SETTING Retrospective review of patients with applicable imaging. PATIENT SAMPLE Fifty-six patients with both computed tomography scans including the thoracic spine obtained for any indication, and dual X-ray absorptiometry T-scores of the femoral neck. METHODS Patients with thoracic CT and DXA scans at one institution were included in the study. Hounsfield units were manually measured from the cancellous bone in T4 vertebrae by one author blinded to DXA scans. HU measurements were compared with femoral neck DXA t-scores. A receiver operator characteristic curve (ROC) with associated dataset was utilized to aid in determining maximum screening HU values for sensitivity and specificity. RESULTS Fifty-six patients with 58 CT scans and femoral neck DXAs were included in the study. The average HU in the osteoporotic group was significantly lower than the normal group (148.89HU±56.53HU vs. 217.56HU±65.69HU, respectively; p CONCLUSIONS Thoracic vertebrae HU measurements correlate with low BMD of the femoral neck as determined by DXA scan T-score. Screening values of 218 HU captured over 95% of those with low BMD, with sensitivity of 90%. Opportunistic utilization of thoracic HU as a screening method provides a simple, quick, and easily assessable screening tool for assessing low BMD.

IntroductionLong instrumented posterior fusion constructs to the lumbosacral spine have a significant rate of pseudoarthrosis and S1 screw failure. With the increasing popularity of Sacral Alar-Ili...

We report a case of severe, intracanal heterotopic ossification in a 54-year-old man following L5‐S1 transforaminal lumbar interbody fusion (TLIF). The patient presented to our clinic with recurrent low back pain, radiating left lower extremity pain and left L5 motor weakness (four of five strength) after previous left L5‐S1 decompression (7 years prior), and left L4‐L5 decompression and revision left L5‐S1 decompression (1 year prior). Imaging studies demonstrated L5‐S1 degenerative disc disease, spondylosis, and left L4‐L5/L5‐S1 foraminal stenosis. He underwent revision decompression from L4 to L5 and L5 to S1, and L5 to S1 TLIF with bilateral pedicle screw instrumentation and local autograft. Immediately postoperative, the patient had significant improvement in his lower extremity symptoms, and at 3 months postoperatively, he was able to return to work and was very satisfied, with complete relief of symptoms. The patient was subsequently readmitted for pain management 6 months postoperative for acute worsening of his low back pain and recurrence of his left leg pain. Magnetic resonance imaging demonstrated an acute left paracentral disc herniation at L4‐L5 (Fig. 1), and computed tomography scan demonstrated heterotopic ossification (HO) along the medial border of the L5‐S1 TLIF decompression/cage insertion track with encroachment on the canal (Fig. 2, A‐D). The formation of such severe intracanal HO without the use of bone morphogenetic protein or other adjuncts is unusual after TLIF. The patient had gradual improvement of his symptoms after analgesic medications and transforaminal corticosteroid injection. Given the patient’s clinical improvement, we will continue to observe him for any progression of the HO or development of new symptoms.