The Impact of Obesity on Risk Factors for Adverse Outcomes in Patients Undergoing Elective Posterior Lumbar Spine Fusion

Deeptee Jain, MD; Wesley Durand, BS; Jeremy D. Shaw, MD; Shane Burch, MD; Vedat Deviren, MD; Sigurd Berven, MD


Spine. 2021;46(7):457-463. 

In This Article

Abstract and Introduction


Study Design: Retrospective case–control study.

Objective: The aim of this study was to determine the influence of obesity on risk factors for adverse outcome after lumbar spine fusion (LSF).

Summary of Background Data: Obesity is risk factor for complications after LSF and poses unique challenges regarding optimization of care. Nonetheless, this patient population is not well-studied.

Methods: Adult patients undergoing LSF were identified the State Inpatient Database. Patients were identified as obese or nonobese using ICD-9 codes. Outcome variables were 90-day readmission, major medical complication, infection, and revision rates. Data were queried for demographics, comorbidities, surgery characteristics, and outcome variables. Logistic multivariate regression was utilized, serially testing interactions between obesity and other independent variables in separate models for each outcome. The Benjamini-Hochberg procedure was used to adjust statistical significance for multiple comparisons.

Results: A total of 262,153 patients were included: 31,062 obese and 231, 091 nonobese. For major complications, obese patients had lower odds ratios (ORs) versus nonobese patients for cerebrovascular accident, diabetes with chronic complications, age ≥65, congestive heart failure, history of myocardial infarction, renal disease, chronic pulmonary disease, Medicare/Medicaid payor, more than two levels fused, transforaminal/posterior lumbar interbody fusion, and female sex, and higher OR for non-White race. For readmission, obese patients had lower OR for age ≥65, history of MI, renal disease, and mental health disease, and higher OR for female sex. For revision, obese patients had higher OR for female sex and TLIF/PLIF. For infection, obese patients had lower OR for diabetes with and without chronic complications, and higher OR for female sex.

Conclusion: Many medical comorbidities have less impact in obese patients than nonobese patients in predicting adverse outcomes despite increased rates of adverse outcomes in obese patients. These findings reflect the impact of obesity as an independent risk factor and have important implications for preoperative optimization.

Level of Evidence: 3


Obesity is increasingly prevalent in the United states, affecting an estimated 35% of the population.[1] Obese patients known to have increased rates of disc degeneration and low back pain.[2] Recent literature has demonstrated that obese patients undergoing spine surgery have greater blood loss, longer operative times, and higher rates of surgical site infection, revision rates, and mortality as compared to nonobese patients.[3,4] Despite these increased risks, obese patients have improved outcomes and a good treatment effect with surgery, and thus warrant surgical management if indicated.[5]

Under the Patient Protection and Affordable Care Act, readmissions have become an important metric of quality of care. The Centers for Medicare and Medicaid Services have initiated a readmission reduction program which penalizes hospitals up to 3% for each readmission episode.[6–9] Age, female sex, African American race, Medicare/Medicaid insurance, medical comorbidities,[10,11] and number of levels have all been implicated as risk factors for readmission in spine surgery.[12] However, there is no literature specifically examining risk factors of spine surgery in obese patients, who comprise a large subset of the spine surgery patient population. Thus, understanding modifiable and nonmodifiable risk factors in addition to obesity to identify patients at high risk have important implications in preoperative optimization to promote the best outcome and may play a role in determining future payment models.

The purpose of this study was to evaluate risk factors for readmission, as well as infection, revision surgery, and medical complications that may have a differential effect in obese vs non obese patients, using posterior lumbar spine fusion (LSF), one of the most commonly performed spine surgeries, as a specific example.