Impact of obesity on outcomes following lumbar spine surgery: A systematic review and meta-analysis

The influence of obesity on spine surgery outcomes is highly controversial with a current clinical equipoise. Several studies suggest higher perioperative morbidity with obesity while other studies suggest otherwise. To address this gap in the literature, we conducted a systematic review and meta-analysis in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines with the objective of better defining the impact of obesity on outcomes following lumbar spine surgery. Risk of bias assessment was performed using the Newcastle-Ottawa Scale. Strength of evidence was assessed using the Grades of Recommendation, Assessment, Development and Evaluation (GRADE) Working Group system. Surgical outcomes such as blood loss, operative time, length of stay, complication and reoperation rates and functional outcomes represented by the change in Oswestry Disability Index and Visual Analog Scale-Back Pain were compared between obese and non-obese patients. A total of 32 studies with 23,415 patients were analyzed. Obese patients had slightly higher surgical blood loss (Mean Difference [MD]: 46.15 ml, CI: 20.21-72, p value < .001, I-2 = 85%) and longer operative times (MD: 17.17 min, CI: 9.91-24.43, p-value < .001, I-2 = 95%), but similar length of stay as compared to non-obese patients. Higher complication (OR = 1.34, C.I. = 1.13-1.58, p = 0.01, I-2 = 45%) and reoperation rates (OR = 1.40, C.I. = 1.19-1.64, p < 0.001, I-2 = 20) were observed in obese patients. The differences, however, were not significant for obese patients undergoing MIS surgery. Functional outcomes (change in ODI and VAS-BP) were similar between the two groups. Overall confidence in GRADE estimates was either low or very low for all outcomes. Obesity might be linked to higher adverse events following lumbar spine surgery. Minimally invasive spine surgery, however, might offer comparable outcomes between obese and non-obese patients. However, further studies are needed to evaluate whether these findings remain valid for morbidly obese (BMI > 40) patients as well.