Effect of Body Mass Index on Fusion Outcome After Short-Segment Posterior Lumbar Fusion

Objective: Obesity is a growing epidemic in the United States. While many adverse effects of obesity on surgical outcome are well studied, a direct correlation among obesity, pseudarthrosis, and adjacent segment pathology is not well defined. In this study we aimed to identify the effect of body mass index (BMI) on pseudarthrosis, adjacent segment pathology (ASP), and reoperation after short-segment (1–3 levels) open posterior lumbar fusion (PLF). Methods: This is a retrospective study of patients with degenerative spine pathologies who underwent 1-, 2-, or 3-level PLF surgery between 2010 and 2020. The relevant medical and imaging records were reviewed, and the following variables were recorded: age, gender, BMI, smoking status, surgical details, follow-up length, need for reoperation, indication for reoperation (pseudarthrosis or occurrence of ASP). Results: We included363 patients in our study. Twenty-five patients (6.9%) developed pseudarthrosis, 109 (30%) developed ASP, and 104 patients (28.7%) underwent reoperation for either of these reasons. BMI was significantly less in those who developed pseudarthrosis compared with those who did not (28.6 ± 5.5 vs. 31.2 ± 6.2, respectively; P = 0.04). BMI was not significantly different in those who developed ASP or underwent reoperation compared with those who did not (P = 0.06 and 0.08, respectively). Multivariate regression analysis showed none of the variables in the model (age, gender, tobacco use, BMI, and its classes) significantly predicted pseudarthrosis, ASP, or reoperation (P > 0.1 for all variables). Conclusions: Obese patients undergoing short-segment open PLF have comparable results in terms of pseudarthrosis, ASP, and reoperation.