Lateral lumbar interbody fusion (LLIF) via the transpsoas approach is often performed with repositioning from lateral decubitus to prone for posterior instrumentation, which prolongs operative time and increases complexity. The single-position prone transpsoas (PTP) technique enables both interbody and posterior fixation without repositioning.

To evaluate whether single-position prone LLIF is non-inferior to the traditional dual-position approach.

A retrospective review of 115 patients who underwent LLIF with posterior fixation by a single surgeon (2015–2025) was performed; 93 met inclusion criteria. Patients were stratified into single-position prone (n = 46, 49.5%) and dual-position (n = 47, 50.5%) cohorts. Propensity score matching reduced selection bias. Primary endpoints included change in segmental lordosis and disc height, with a predefined non-inferiority margin of Cohen’s d < 0.4.

The average age was 64.7 ± 10.2 years; 52.7% were male. Mean operative time was 290.8 ± 127 min, with blood loss of 112.8 ± 117 cc. A total of 147 interbody cages were placed (mean 1.87 ± 0.96 levels per case), most commonly at L3−4 and L4−5. Radiographic and clinical follow-up averaged 10.9 and 29.2 months. Segmental lordosis improved 6.86 ° (single) vs. 7.67 ° (dual), and disc height increased 6.52 mm vs. 8.00 mm, both within non-inferiority thresholds (Cohen’s d: −0.29 and −0.13). Sacral slope change differed significantly (p = 0.005). Complication rate was 9.7%, revision rate was 10.8% (p = 0.167), with average revision at 15.1 months.

Single-position prone LLIF with posterior fixation is non-inferior to dual-position LLIF regarding key radiographic and clinical outcomes, offering an efficient alternative without compromising safety or deformity correction.