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Prior studies investigating the association between Body Mass Index (BMI) and patient outcomes following spine surgery have had inconsistent conclusions, likely owing to insufficient power, confounding variables, and varying definitions and cutoffs for BMI categories (eg, underweight, overweight, obese, etc.). Further, few studies have considered outcomes among low BMI cohorts.The current study analyzes how anterior lumbar interbody fusion (ALIF) perioperative outcomes vary along the BMI spectrum, using World Health Organization (WHO) categories of BMI.A retrospective cohort study.Patients undergoing stand-alone one or two-level anterior lumbar interbody fusion (ALIF) found in the 2005-2018 American College of Surgeons National Surgical Quality Improvement Program (NSQIP) databases.Thirty-day adverse events, hospital readmissions, post-operative infections, and mortality.Stand-alone one or two-level ALIF surgical cases were identified and extracted from the 2005-2018 National Surgical Quality Improvement Program (NSQIP) database. Posterior cases and those primary diagnoses of trauma, tumor, infection, or emergency presentation were excluded. Patients were then binned into WHO guidelines of BMI. The incidence of adverse outcomes within 30-day post-operation was defined. Odds ratios of adverse outcomes, normalized to the average risk of normal-weight subjects (BMI 18.5-24.9 kg/mIn total, 13,710 ALIF patients were included in the study. Incidence of adverse events was elevated in both the underweight (BMI18.5 kg/mUnderweight patients are at greater odds of experiencing postoperative adverse events than normal, overweight, obese class 1, or even obese class 2 patients. The present study identifies underweight patients as an at-risk population that should be given additional consideration by health systems and physicians, as is already done for those on the other side of the BMI spectrum.

BACKGROUND CONTEXT Past studies have focused on the association of high body mass index (BMI) on spine surgery outcomes. These investigations have reported mixed conclusions, possible due to insufficient power, poor controlling of confounding variables, and inconsistent definitions of BMI categories (e.g. underweight, overweight, and obese). Few studies have considered outcomes of patients with low BMI. PURPOSE To analyze how anterior cervical spine surgery outcomes track with World Health Organization categories of BMI to better assess where along the BMI spectrum patients are at risk for adverse perioperative outcomes. DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE Patients undergoing elective anterior cervical spine surgery were abstracted from the 2005 to 2016 American College of Surgeons National Surgical Quality Improvement Program database. OUTCOME MEASURES Thirty-day adverse events, hospital readmissions, postoperative infections, and mortality. METHODS Patients undergoing anterior cervical spine procedures (anterior cervical discectomy and fusion, anterior cervical corpectomy, cervical arthroplasty) were identified in the 2005 to 2016 National Surgical Quality Improvement Program database. Patients were then aggregated into modified World Health Organization categories of BMI. Odds ratios of adverse outcomes, normalized to average risk of normal weight subjects (BMI 18.5–24.9 kg/m2), were calculated. Multivariate analyses were then performed on aggregated adverse outcome categories controlling for demographics (age, sex, functional status) and overall health as measured by the American Society of Anesthesiologists classification. RESULTS In total, 51,149 anterior cervical surgery patients met inclusion criteria. Multivariate analyses revealed the odds of any adverse event to be significantly elevated for underweight and super morbidly obese patients (Odds Ratios [OR] of 1.62 and 1.55, respectively). Additionally, underweight patients had elevated odds of serious adverse events (OR=1.74) and postoperative infections (OR=1.75) and super morbidly obese patients had elevated odds of minor adverse events (OR=1.72). Relative to normal BMI patients, there was no significant elevation for any adverse outcomes for any of the other overweight/obese categories, in fact some had reduced odds of various adverse outcomes. CONCLUSIONS Underweight and super morbidly obese patients have the greatest odds of adverse outcomes after anterior cervical spine surgery. The current study identifies underweight patients as an at-risk population that has previously not received significant focus. Physicians and healthcare systems should give additional consideration to this population, as they often already do for those at the other end of the BMI spectrum.

The prevalence of dialysis-dependent patients in the United States is growing. Prior studies evaluating the risk of perioperative adverse events for dialysis-dependent patients are either institutional cohort studies limited by patient numbers or administrative database studies limited to inpatient data.The present study uses a large, national sample with 30-day follow-up to investigate dialysis as risk factor for perioperative complications independent of patient demographics or comorbidities.This is a retrospective cohort study.Patients undergoing elective spine surgery with or without dialysis from the 2005-2015 National Surgical Quality Improvement Program (NSQIP) database were included in the study.Postoperative complications within 30 days and binomial reoperation, readmission, and mortality within 30 days were determined.The 2005-2015 NSQIP databases were queried for adult dialysis-dependent and dialysis-independent patients undergoing elective spinal surgery. Differences in 30-day outcomes were compared using risk-adjusted multivariate regression and coarsened exact matching analysis for adverse events, unplanned readmission, reoperation, and mortality. The percentage of complications occurring before versus after hospital discharge was also assessed. The authors have no financial disclosures related to the present study.A total of 467 dialysis and 173,311 non-dialysis patients met the inclusion criteria. Controlling for age, gender, body mass index, functional status, and American Society of Anesthesiologists (ASA) class, dialysis patients were found to be at significantly greater odds of any adverse event (odds ratio [OR]=2.52 before, 2.17 after matching, p=.001), major adverse event (OR=2.90 before, 2.52 after matching, p=.001), and minor adverse event (OR=1.50 before matching, p=.025, but not significantly different after matching). Further, dialysis patients were significantly more likely to return to the operating room (OR=2.77 before, 2.50 after matching, p=.001), have unplanned readmissions (OR=2.73 before, 2.37 after matching, p=.001), and die within 30 days (OR=3.77 before, 2.71 after matching, p=.001). Adverse events occurred after discharge for 51.78% of non-dialysis patients and for 43.80% of dialysis patients.Dialysis patients undergoing elective spine surgery are at significantly higher risk of aggregated adverse outcomes, return to the operating room, readmission, and death than non-dialysis patients, even after controlling for patient demographics and overall health (as indicated by ASA class). These differences need to be considered when determining treatment options. Additionally, with bundled payments expected in spine surgery, physicians and hospitals need to account for increased costs and liabilities when working with dialysis patients.

Background Context Venous thromboembolism (VTE) is a known complication after spine surgery, but prophylaxis guidelines are ambiguous for patients undergoing elective spine surgery. Purpose The objective of this study was to characterize the incidence and risk factors for VTE and the association of pharmacologic prophylaxis with VTE and bleeding complications after elective spine surgery. Study Design/Setting This is a retrospective cohort study of patients undergoing elective spine surgery in the National Surgical Quality Improvement Program (NSQIP) database and a retrospective cohort analysis at an academic medical center. Patient Sample This study included 109,609 patients in the NSQIP database from 2005 to 2014 and 2,855 patients at the authors' institution from January 2013 to March 2016 who underwent elective spine surgery. Outcome Measures The incidence and risk factors for VTE were assessed in both cohorts based on the NSQIP criteria. The incidence of bleeding complications requiring reoperation was assessed based on operative reports in the institutional cohort. Materials and Methods Associations of patient and procedure factors with VTE were characterized in the NSQIP population. In the single-institution cohort, in addition to NSQIP variables, a chart review was completed to determine the use of VTE prophylaxis, the history of prior VTE, and the incidence of hematoma requiring reoperation. The association of patient and procedure variables, including pharmacologic prophylaxis and history of prior VTE, with VTE and hematoma requiring reoperation were determined with multivariate regression. Results Among 109,609 elective spine surgery patients in NSQIP, independent risk factors for VTE were greater age, male gender, increasing body mass index, dependent functional status, lumbar spine surgery, longer operative time, perioperative blood transfusion, longer length of stay, and other postoperative complications. There were 2,855 patients included in the institutional cohort. Pharmacologic prophylaxis was performed in 56.3% of the institutional patients, of whom 97.1% received unfractionated heparin. When controlling for patient and procedural variables, pharmacologic prophylaxis did not significantly influence the rate of VTE, but was associated with a significant increase in hematoma requiring a return to the operating room (relative risk=7.37, p=.048). Conclusions Pharmacologic prophylaxis, primarily with unfractionated heparin, after elective spine surgery was not associated with a significant reduction in VTE. However, there was a significant increase in postoperative hematoma requiring reoperation among patients undergoing prophylaxis. This raises questions about the routine use of unfractionated heparin for VTE prophylaxis and supports the need for further consideration of risks and benefits of chemoprophylaxis after elective spine surgery.