Side of Approach Does Not Affect Outcomes in Direct Lateral Lumbar Interbody Fusion: A Noninferiority Retrospective Cohort Study

BACKGROUND: Lateral lumbar interbody fusion (LLIF) is a minimally invasive surgical technique with various clinical benefits. However, there is no consensus on the optimal side of approach. This study investigates clinical and radiographic outcomes associated with surgical laterality, where the approach side was chosen based on operating room theater flow rather than anatomy. METHODS: Retrospective analysis of prospectively collected data from 233 patients (2016-2021) who underwent LLIF by 2 surgeons, each consistently using a specific side according to operating room setup. Outcomes included the Oswestry Disability Index, visual analog scale, 12-Item Short Form Health Survey, and radiographic fusion. Statistical comparisons included predefined noninferiority margins for operative time (15 minutes) and fusion (10%). RESULTS: = 0.66), visual analog scale, Oswestry Disability Index, or complication rates. Fusion at 12 months was 94.9% vs 93.2%, respectively. CONCLUSIONS: LLIF outcomes did not differ by side of approach. While anatomical considerations may apply in selected cases (eg, coronal deformity), theater flow factors can guide side selection without compromising outcomes. This study is limited by surgeon-side bias and the absence of randomization. CLINICAL RELEVANCE: This study demonstrates that when performing LLIF, the side of approach (left vs right) does not significantly affect operative time, fusion rates, complication rates, or patient-reported outcomes when chosen based on operating room theater flow rather than patient anatomy. These findings suggest that surgeons may prioritize ergonomic efficiency and operating room logistics without compromising clinical or radiographic results, except in specific cases such as significant coronal deformity or prior retroperitoneal surgery. LEVEL OF EVIDENCE: Level 3.