Abstract
BACKGROUND: Lumbar spondylolisthesis often causes pain and disability, requiring surgical intervention. While prior studies explore the impact of body mass index (BMI) on outcomes following lumbar fusion, the effect of different surgical approaches, specifically transforaminal lumbar interbody fusion (TLIF) and lateral lumbar interbody fusion (LLIF), across BMI categories remains unclear. This study evaluates patient-reported outcomes (PROs) following TLIF and LLIF in low-grade degenerative and isthmic spondylolisthesis, focusing on BMI stratification. METHODS: This study retrospectively analyzes patients with low-grade degenerative and isthmic spondylolisthesis who underwent lumbar fusion between 2010 and 2023. Patients were stratified by BMI into the following four groups: non-obese (<30), class I (30-34.9), class II (35-39.9), and class III (≥40). It assesses PROs using the Oswestry Disability Index (ODI) and visual analog scale (VAS) for pain at baseline and 12 months, comparing the achievement of minimal clinically important difference (MCID) between TLIF and LLIF. RESULTS: This analysis included 72 patients showing significant improvements in ODI (mean change: 17.0; p<0.001) and VAS (mean change: 2.3; p<0.001) scores across all BMI categories at 12 months. TLIF and LLIF achieve similar rates of MCID, with no statistically significant differences between the surgical approaches (p=0.72). Non-obese and class II patients maintain sustained improvements. CONCLUSION: Lumbar fusion using both open and minimally invasive (MIS) TLIF and LLIF leads to significant disability reduction across BMI categories, indicating that obesity does not contraindicate lumbar fusion. Surgical approach selection should focus on individual patient factors rather than BMI alone. Prospective studies with extended follow-up will further clarify the long-term impact of these approaches.