Faculty Bibliography

BACKGROUND CONTEXT: Obesity's impact on standing sagittal alignment remains poorly understood, especially with respect to the role of the lower-limbs. Given energetic expenditure in standing, a complete understanding of compensation in obese patients with sagittal malalignment remains relevant. PURPOSE: This study compares obese and non-obese patients with progressive sagittal malalignment for differences in recruitment of pelvic and lower limb mechanisms. STUDY DESIGN/SETTING: Single center retrospective review. PATIENT SAMPLE: 554 patients (277 obese, 277 non-obese) identified for analysis. OUTCOME MEASURES: Upper body alignment parameters: sagittal vertical axis (SVA) and T1 spino-pelvic inclination (T1SPi). Compensatory lower-limb mechanisms: pelvic translation (PS: pelvic shift), knee (KA) and ankle (AA) flexion, hip extension (SFA: sacrofemoral angle), and global sagittal angle (GSA). METHODS: Inclusion criteria were patients>/=18 years that underwent full body stereographic x-rays. Included patients were categorized as non-obese (N-Ob: BMI<30 kg/m2) and obese (Ob: BMI>/=30 kg/m2). To control for potential confounders, groups were propensity score matched by age, gender and baseline pelvic incidence (PI), and subsequently categorized by increasing spino-pelvic (PI-LL) mismatch: <10 degrees , 10 degrees -20 degrees , >20 degrees . Independent t-tests and linear regression models compared sagittal (SVA, T1SPi) and lower limb (PS, KA, AA, SFA, GSA) parameters between obesity cohorts. RESULTS: 554 patients (277 Ob, 277 N-Ob) were included for analysis, and were stratified to the following mismatch categories: <10 degrees : n=367; 10 degrees -20 degrees : n=91; >20 degrees : n=96. Ob patients had higher SVA, KA, PS and GSA compared to N-Ob (p<0.001 all). Low PI-LL mismatch Ob patients had greater SVA with lower SFA (142.22 degrees vs. 156.66 degrees , p=0.032), higher KA (5.22 degrees vs. 2.93 degrees , p=0.004) and PS (4.91 vs. -5.20 mm, p<0.001) compared to N-Ob. With moderate PI-LL mismatch, Ob patients similarly demonstrated greater SVA, KA, and PS, combined with significantly lower PT (23.69 degrees vs. 27.14 degrees , p=0.012). Obese patients of highest (>20 degrees ) PI-LL mismatch showed greatest forward malalignment (SVA, T1SPi) with significantly greater PS, and a concomitantly high GSA (12.86 degrees vs. 9.67 degrees , p=0.005). Regression analysis for lower-limb compensation revealed that increasing BMI and PI-LL predicted KA (r2=0.234) and GSA (r2=0.563). CONCLUSIONS: With progressive sagittal malalignment, obese patients differentially recruit lower extremity compensatory mechanisms while non-obese preferentially recruit pelvic mechanisms. The ability to compensate for progressive sagittal malalignment with the pelvic retroversion is limited by obesity.

Cervical spondylotic myelopathy (CSM) is the most common cause of spinal cord dysfunction in patients older than age 55, with operative management being a widely adopted approach. Previous work has shown that private insurance status, gender and patient race are predictive of the operative approach patients receive (anterior-only, posterior-only, combined anterior-posterior). The Nationwide Inpatient Sample from 2001 to 2010 was used to assess the potential role of multilevel CSM as a contributing factor in determining which operative approach CSM patients receive, as it is rare for an anterior-only approach to be sufficient for CSM patients requiring fusion of four or more involved levels. Multivariate analyses revealed that female sex (OR=3.78; 95% CI=2.08-6.89; p<0.0001), private insurance (OR=5.02; 95% CI=2.26-11.12; p<0.0001), and elective admission type (OR=4.12; 95% CI=1.65-10.32; p=0.0025) were predictive of increased receipt of a 3+ level fusion in CSM. No other variables, including patient age, race, income, or admission source were predictive of either increased or decreased likelihood of receiving fusion of at least three levels for CSM. In conclusion, female sex, private insurance status, and elective admission type are each independent predictors in CSM for receipt of a 3+ level fusion, while patient age, race and income are not. Given the propensity of fusions greater than three levels to require posterior approaches and the association between posterior CSM approaches and increased morbidity/mortality, these findings may prove useful as to which patient demographics are predictive of increased morbidity and mortality in operative treatment of CSM.

Introduction: Blood loss is a major concern in spine surgery. Blood transfusion promotes oxygen delivery and tissue perfusion during long, complex surgeries, yet carries with it rare but notable risks. The hemoglobin (Hb) trigger-the Hb value that initiates clinician administration of packed red blood cells (PRBCs)-is frequently used to evaluate physician compliance with existing transfusion guidelines. Randomized clinical trials have demonstrated similar or improved outcomes among patients receiving blood transfusions using a restrictive Hb trigger-defined as an intraoperative Hb level of <10 g/dL intraoperatively or <8 g/dL postoperatively-versus a liberal Hb trigger (>=10 g/dL intraoperatively or >=8 g/dL postoperatively) in cardiac and hip surgery. To the authors' knowledge, no study has examined the associated morbidity and financial impact of liberal transfusions within spinal surgery. We thus aimed to determine the perioperative clinical outcomes and costs associated with liberal versus restrictive transfusion triggers among spine surgery patients. Material and Methods: The surgical billing database at our institution was queried for inpatients discharged following spinal surgery between 2008 and 2015, yielding 33,043 patients. Patients were stratified into eight groups according to the spine surgical procedure performed. The values used were the reported institutional acquisition cost ($220/unit) and a mean estimated activity-based cost ($760/unit) based on a Society for the Advancement of Blood Management report. Outcomes considered included mortality, in-hospital morbidity, total costs, and length of stay. Results: A total of 6,931 patients met the inclusion criteria. PRBC transfusions occured in 2,374 patients (at least 1 unit of PRBCs), yielding an overall transfusion rate of 34.3%. Compared to the other surgical groups, most PRBC use occurred within posterior lumbar fusion patients. The mean intraoperative Hb trigger was 10.1 (SD = 1.7) g/dL and the mean postoperative Hb trigger was 10.1 (SD = 2.1) g/dL. For the 2,374 patients that were transfused with PRBCs, 1420 (59.8%) received a postoperative PRBC transfusion with a liberal postoperative Hb trigger (>=8 g/dL) while 529 (22.3%) received an intraoperative PRBC transfusion with a liberal intraoperative Hb trigger (>=10 g/dL). Logistic regression analysis revealed that patients with a nadir Hb of 8-10 g/dL transfused with PRBC had an independently higher risk of perioperative morbidity (odds ratio [OR] = 2.12; 95% confidence interval [CI], 1.24-3.64; P = .006). The additional cost when comparing restrictive and liberal transfusion triggers was estimated to be between $1,330,439 and $4,596,062 (58.7% of the estimated total cost of PRBC transfusion), with the cost varying by surgery type. When comparing liberal and restrictive PRBC transfusion triggers, an estimated additional $202,675 to $700,151 in institutional costs were incurred each year among patients undergoing spine surgery. Conclusion: Patients with a nadir Hb of 8 to 10 g/dL who were transfused had higher perioperative morbidity, even after adjusting for potential confounders. The additional cost incurred from liberal transfusion trigger reliance ranged from an estimated $202,675 to $700,151 annually. These findings point to a potential area for clinicians and institutions to improve patient outcomes and reduce costs

Introduction: Despite the potential for profound impact of adult cervical deformity (ACD) on function and healthrelated quality of life, there remains a paucity of highquality studies that assess outcomes of surgical treatment for these patients. Our objective was to assess outcomes following surgical treatment for ACD based on a prospective multicenter consecutive case series. Materials and Methods: Surgically treated ACD patients eligible for 1-year followup were identified from a prospectively collected multicenter database. Baseline deformity characteristics, surgical parameters, and 1-year outcomes were assessed. Standardized outcome measures included: Neck Disability Index (NDI, range 0-100), neck pain numeric rating scale (NRS) score (range 0-10), and EQ-5D index (range 0 -1) and subscores (range 1-3). Paired sample t-tests were used to compare 1-year and baseline measures. Results: Of 77 ACD patients, 55 (71%) had 1-year follow-up (64% women, mean age 61 years, mean Charlson Comorbidity Index [CCI] of 0.6, previous cervical surgery in 44%). Diagnoses included: cervical sagittal imbalance (62%), cervical kyphosis (60%), proximal junctional kyphosis (8%), and coronal deformity (10%). Posterior fusion was performed in 85% (mean number of vertebral levels=10), and anterior fusion was performed in 29% (mean number of vertebral levels = 5). Three-column osteotomy was performed in 24% of patients. Mean operative time was 6.5 hours and mean estimated blood loss was 0.9L. At 1-year following surgery, ACD patients had significant improvement in NDI (50.5 to 38.0, P < .001), neck pain NRS (6.9 to 4.3, P < .001), EQ-5D index (0.51 to 0.66, P < .001), and EQ-5D subscores: mobility (1.9 to 1.7, P = .019), usual activities (2.2 to 1.9, P = .007), pain/discomfort (2.4 to 2.1, P < .001), anxiety/depression (1.8 to 1.5, P = .014). A nonsignificant trend favoring improvement was observed for EQ-5D self-care (1.5 to 1.3, P = .070). Compared with patients that achieved 1-year follow-up, those lost to followup did not differ significantly with regard to age, gender, CCI, number of fused anterior or posterior vertebral levels, or baseline NDI, neck pain NRS, or EQ-5D scores. Conclusions: Based on a prospective multicenter series of adults with cervical deformity, surgical treatment provided significant improvement in multiple measures of pain and function, including the NDI, neck pain NRS score, and EQ-5D. Further follow-up will be necessary to assess the durability of these surgical procedures and the resulting improved outcomes

Introduction: Although adult cervical deformity (ACD) has been empirically associated with significant pain and disability, the magnitude of this negative impact has not been objectively quantified. Our objective was to assess whether symptomatic ACD patients have substantial negative health impact based on the EQ-5D compared with United States (U.S.) normative and chronic disease state values. Materials and Methods: ACD patients presenting for surgical evaluation and treatment were identified from a prospectively collected multicenter database. Baseline demographics, deformity characteristics, and EQ-5D scores were collected. EQ-5D scores were compared with ageand gender-matched U.S. normative and chronic disease state values. Results: Of 121 ACD patients, 115 (95%) completed the EQ-5D (61% women, mean age 61 years, previous cervical surgery in 46%). Diagnoses included: cervical sagittal malalignment (63%), cervical kyphosis (60%), proximal junctional kyphosis (9%) and coronal deformity (8%). The mean EQ-5D index was 0.511, which is 35% below the bottom 25th percentile score (0.790) for a similar age- and gender-weighted normative population and worse than the bottom 25th percentile for several other chronic disease states (diabetes [0.708], ischemic heart disease [0.708], and myocardial infarction [0.575]). The EQ-5D index of 0.511 seen in this ACD cohort is comparable to the bottom 25th percentile for blindness (0.543), emphysema (0.508) and heart failure (0.437). Based on EQ-5D subscores, patients reported impact on mobility (87%), daily self-care (47%), daily activities (91%), pain/discomfort (98%), and anxiety/depression (67%). Conclusions: The health impact of symptomatic ACD is substantial, with an EQ-5D index that is 35% below the bottom 25th percentile for an age- and gender-matched normative U.S. population. The markedly negative health impact of ACD was demonstrated across all domains of the EQ-5D. The overall mean EQ-5D index for ACD patients was worse than the bottom 25th percentile for several other chronic disease states, including chronic ischemic heart disease, malignant breast cancer, and malignant prostate cancer, and was comparable to the bottom 25th percentile values for blindness/low vision, emphysema, renal failure, and stroke

Introduction: Although three-column osteotomy (3CO; pedicle subtraction osteotomy [PSO] or vertebral column resection [VCR]) can provide powerful alignment correction and disability improvement in adult cervical deformity (ACD), these procedures are complex and associated with high complication rates. Previous reports on complications associated with 3CO for ACD have been primarily based on retrospective complication collection, which may substantially underestimate the true rates. Our objective was to provide a prospective assessment of cervical alignment improvement and complications in ACD patients treated with 3CO. Materials and Methods: Although three-column osteotomy (3CO; pedicle subtraction osteotomy [PSO] or vertebral column resection [VCR]) can provide powerful alignment correction and disability improvement in adult cervical deformity (ACD), these procedures are complex and associated with high complication rates. Previous reports on complications associated with 3CO for ACD have been primarily based on retrospective complication collection, which may substantially underestimate the true rates. Our objective was to provide a prospective assessment of cervical alignment improvement and complications in ACD patients treated with 3CO. Results: All 24 ACD patients treated with 3CO (15 PSO/ 9 VCR) achieved minimum 90-day follow-up (71% women, mean age 62 years, previous surgery in 54%). Diagnoses included: cervical sagittal imbalance (92%), cervical kyphosis (38%), proximal junctional kyphosis (17%), coronal deformity (8%) and distal junctional kyphosis (4%). The mean number of posterior fusion levels was 13, and 4% also had an anterior fusion. The most common 3CO levels were T1 (38%), T2 (29%) and T3 (21%). A total of 25 (19 major/6 minor) complications were reported, with 14 (58%) and 6 (25%) patients affected, respectively. Overall, 17 (71%) patients had at least one complication. The most common complications were excessive blood loss (>1.7L, 25%), neurologic deficit (17%), distal junctional kyphosis (DJK, 8%), wound infection (13%), and cardiorespiratory failure (8%). Four (17%) patients required re-operation within 90-days (2 for nerve root motor deficit, 1 deep wound infection, 1 implant pain/prominence). Cervical sagittal alignment improved significantly following 3CO: cervical lordosis (CL, 3degree to 13degree, P = .031), C2-7 sagittal vertical axis (66mm to 44mm, P < .001), and T1 slope minus CL (46degree to 27degree, P < .001). Conclusions: Among 24 ACD patients treated with 3CO, cervical sagittal alignment improved significantly following surgery. Overall, 17 (71%) patients had at least one complication (19 major/6 minor). The most common complications were excessive blood loss (>1.7L), neurologic deficit, DJK, wound infection, and cardiorespiratory failure. Future research focused on reducing these complications may present the greatest opportunities for safety and cost improvements for these procedures

Introduction: The length of stay (LOS) following adult spinal deformity (ASD) surgery is a critical time period allowing for recovery to levels safe enough for to return home or to rehabilitation. Thus, the goal is to minimize it for conserving hospital resources and third party payer pressure. Factors related to LOS have not been studied nor has a predictive model been created. The purpose was to create a preoperative predictive model to predict the LOS following ASD surgery. Material and Methods: Retrospective review of a multicenter, prospective ASD database. Inclusion criteria: operative pts, age >18 yrs, ASD. Pts with staged surgery at a separate hospitalization or LOS >30 days were excluded. 66 variables were initially evaluated with 40 being used for model building following univariable predictor importance >=0.90, redundancy, and collinearity testing. Variables included: demographic data, comorbidities, preop HRQOL, preop coronal and sagittal radiographic parameters, and modifiable surgical factors. A generalized linear model was constructed using a training dataset developed from a boostrapped sample with replacement using a random number generator. Pts randomly omitted from the boostrapped sample were included in the testing dataset. Accuracy was calculated by comparison of predicted LOS to the actual LOS. Results: A total of 689 patients were eligible with 653 meeting inclusion criteria. The mean LOS was 7.9 +/- 4.1 days (median = 7, range: 1-28). Following bootstrapping, a total of 893 pts were modeled, Training: 653, Testing: 240(36.6%). The linear correlations for the training and testing datasets were 0.632 and 0.507, respectively. Testing dataset accuracy within 2 days of actual LOS was 75.4% (181/240 pts). The top 10 predictors were the following in decreasing order: staged surgery (yes/ no), C7 SVA, number of posterior levels fused, Charlson Comorbidity Index, Total number of comorbidities, preop ODI score, iliac fixation (yes/no), preop SRS Activity score, preop SRS Appearance scores, and number of interbody fusion levels. Conclusion: A successful model was created to predict LOS following ASD surgery to an accuracy of 75% within 2 days. There are some factors related to LOS that are not likely captured in large databases, which may partially explain the 75% accuracy, such as rehab bed availability and social support resources

STUDY DESIGN: Retrospective cohort study of a prospectively-collected surgical database. OBJECTIVE: The aim of this study was to investigate the effect of smoking on 30-day morbidity and mortality in patients undergoing surgery for adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: There is conflicting evidence regarding the impact of smoking on short-term outcomes after spinal fusion. METHODS: A retrospective review of the prospectively-collected American College of Surgeons National Surgical Quality Improvement database was performed for the years 2007-2013. Patients who underwent spinal fusion for ASD were identified. 30-day morbidity and mortality were compared between current smokers and nonsmokers. The independent effect of smoking was investigated via multivariate logistic regression analysis. RESULTS: A total of 1,368 patients met inclusion criteria and were included in this study. Of the 1,368 patients, 15.9% were smokers and 84.1% nonsmokers. The proportion of smokers who developed at least one complication was 9.7% versus 13.6% for nonsmokers (p = 0.119). Major complication rates (including 30-day mortality) were 6.5% for smokers and 8.4% for nonsmokers (p = 0.328). Current smoking status was not associated with increased odds of developing any complication (OR 0.90; 95% CI, 0.47-1.71; p = 0.752) or major complications (OR 1.32; 95% CI 0.64-2.70; p = 0.447) after multivariate analysis. CONCLUSION: Smoking was not associated with higher 30-day complications or mortality after corrective surgery for ASD in this study. However, given the negative effects of smoking on overall health and spine surgery outcomes in the long-term, smoking cessation prior to spinal fusion is still recommended. LEVEL OF EVIDENCE: 3.

STUDY DESIGN: Cross-sectional study of a national surgical database. OBJECTIVE: To investigate the timing of complications after adult spinal deformity (ASD) surgery. SUMMARY OF BACKGROUND DATA: There is limited data on the range of days when complications after ASD surgery occur. METHODS: The American College of Surgeons National Surgical Quality Improvement database was reviewed for the years 2007-2013. Inclusion criteria were adult patients (over 21 years of age) who underwent spinal fusion for ASD. Ten unique complications occurring within 30 postoperative days were examined and the median day to diagnosis was recorded. RESULTS: A total of 1,250 patients met inclusion criteria with an overall complication rate of 13.5%. The median day of diagnosis (and interquartile range) for each complication was as follows: myocardial infarction (3.5, 1-5), pulmonary embolism (4, 2-16), reintubation (4.5, 1-11), pneumonia (6, 3-9), urinary tract infection (11, 5-15), sepsis (12, 6-18.5), deep vein thrombosis (12, 6-19), deep surgical site infection (SSI; 18.5, 13-23), superficial SSI (19, 13-24), and organ space SSI (21, 17-25). The three complications that were most commonly diagnosed before hospital discharge included pneumonia, reintubation, and myocardial infarction (diagnosed before discharge on more than 70% of cases). On the other hand, superficial, deep, and organ space infection were diagnosed in less than 40% of cases before patients left the hospital. On univariate analysis, predictors of complication occurrence included older age (p = .014), instrumentation of 7-12 levels (p = .034), and instrumentation of 13 or more levels (p = .035). CONCLUSION: Understanding the timing of specific complications after adult spinal deformity surgery is important for both patients and clinicians. Efforts in prevention of such conditions should continue, as well as heightened awareness during the periods of highest risk.

STUDY DESIGN: Retrospective cohort study OBJECTIVE.: To assess factors potentially impacting the operative approach chosen for CSM patients on a nationwide level. SUMMARY OF BACKGROUND DATA: Cervical spondylotic myelopathy (CSM) is one of the most common spinal disorders treated by spine surgeons, with operative management consisting of three approaches: anterior-only, posterior-only, or combined anterior-posterior. It is unknown whether the operative approach used differs based on patient demographics and/or insurance status. METHODS: The Nationwide Inpatient Sample from 2001-2010 was used for analysis. Admissions having a diagnosis code of 721.1 and a primary procedure code of 81.02/81.03, 81.32/81.33, 81.02/81.03 or 81.32/81.33 (combined anterior and posterior fusion/refusion at C2 or below), and 3.09 (decompression of the spinal canal including laminoplasty) were included. Analysis was adjusted for several variables including patient age, race, sex, primary payer for care, and admission source/type. RESULTS: Multivariate analyses revealed that non-Caucasian race [Black (OR = 1.39;95%CI = 1.32-1.47;p < 0.0001), Hispanic (OR = 1.51;95%CI = 1.38-1.66;p < 0.0001), Asian/Pacific Islander (OR = 1.40;95%CI = 1.15-1.70;p = 0.0007), Native American (OR = 1.33;95%CI = 1.02-1.73;p = 0.037)] and increasing age (OR = 1.03; p < 0.0001) were predictive of receiving posterior-only approaches. Female sex (OR = 1.39;95%CI = 1.34-1.43;p < 0.0001), private insurance (OR = 1.19;95%CI = 1.14-1.25;p < 0.0001), and non-trauma center admission type (OR = 1.29-1.39;95%CI = 1.16-1.56;p < 0.0001) were independently predictive of increased likelihood of receiving an anterior-only approach. Hispanic race (OR = 1.35;95%CI = 1.14-1.59;p = 0.0004) and admission source [another hospital (OR = 1.65;95%CI = 1.20-2.27;p = 0.0023), other health facility (OR = 1.68;95%CI = 1.13-2.51;p = 0.011)] were the only variables predictive of increased combined anterior-posterior approaches; Native American race (OR = 0.32;95%CI = 0.13-0.78;p = 0.013) decreased the likelihood of a combined anterior-posterior approach. CONCLUSIONS: Private insurance status, female sex, and Caucasian race independently predict receipt of anterior-only CSM approaches, while non-Caucasian race (Black, Hispanic, Asian/Pacific Islander, Native American) and non-private insurance predict receiving posterior-only CSM approaches. Given recent literature demonstrating posterior-only approaches as predictive of increased mortality in CSM (Kaye et al., 2015), our findings indicate that for CSM patients, non-Caucasian race may significantly increase mortality risk, while private insurance status may significantly decrease the risk of mortality. Further prospective study will be needed to more definitively address these issues. LEVEL OF EVIDENCE: 3.