Adverse Impact of Obesity on Lumbar Spine Fusion, Patient-Reported Outcomes and Costs: A Systematic Review and Meta-Analysis.

Study design: Systematic review and meta-analysis.

Purpose: The objective of this study is to determine the impact of obesity on three key lumbar spinal surgery outcomes: the incidence of spinal nonunion, patient-reported outcome measures (PROMs), and the associated healthcare costs.

Summary of background data: Obesity is a well-recognized risk factor in various medical fields, notably impacting outcomes in orthopedics and traumatology. While there is substantial documentation of the complications associated with obesity in general surgical procedures, the relationship between obesity and spinal surgery outcomes remains less clear. The inconsistency in the evidence presents a significant gap in our understanding of how obesity influences the results of spinal surgeries, particularly in terms of nonunion rates, patient-reported outcomes, and the associated healthcare costs.

Methods: A systematic search was conducted in PubMed, EMBASE, Scopus, and the Cochrane Library following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Studies comparing patients with or without obesity with lumbar spinal fusion were included. Comparative studies (cohort and case-control) were included. For dichotomous variables such as spinal nonunion, analysis was conducted using odds ratios (OR); for continuous variables such as PROMs (Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), and 12/36-Item Short Form Survey (SF-12/36), and costs, analyses were performed using mean differences (MD) or standardized mean differences (SMD).

Results: Fifteen studies with a pool of 61341 patients were included. Obesity (BMI≥30) was significantly associated with a higher nonunion frequency (OR 2.10, 95%CI 1.23 to 3.60, P<0.01). The ODI was significantly worse in the obesity group (MD 6.29, 95% CI 4.71 to 7.88, P<0.001). Greater pain was measured by the VAS back pain (MD 0.95, 95% CI 0.17 to 1.73, P<0.05) and VAS leg pain (MD 0.94, 95% CI 0.68 to 1.20, P<0.001) scales for lumbar surgery patients with obesity. The SF-12/36 showed significantly worse outcomes in patients with obesity (SMD -0.46, 95%CI -0.82 to -0.09, P=0.01). Hospitalization costs were significantly higher in patients with obesity (SMD 0.09, 95%CI 0.05 to 0.12, P<0.001).

Conclusion: This meta-analysis suggests that obesity is significantly associated with higher nonunion rates, poorer patient-reported outcome measures including Oswestry Disability Index, Visual Analogue Scale, and 36-Item Short Form Survey, and higher hospitalization costs following lumbar spinal fusion.

Level of evidence: III.