Antepsoas vs. Transpsoas Approach to Lateral Interbody Fusion

Introduction: Lateral lumbar interbody fusion (LLIF) consists of antepsoas or transpsoas approaches. Few studies have directly compared the two surgical techniques. The primary outcome of this study is to analyze the radiographic parameters between the antepsoas and transpsoas approaches for lumbar interbody fusion.

Methods: Patients undergoing LLIF from L2-L5 were retrospectively reviewed at a single academic center. All interbody levels must have been accessed via a lateral approach, followed by posterior transpedicular fixation. Patients with L5-S1 interbody fusion and/or posterior column osteotomies were excluded. All cases must have utilized 10 mm cages in order to homogenize the radiographic parameters. All patients underwent both preoperative and postoperative 36-inch standing scoliosis x-rays. Foraminal height was calculated as the average of the interspaces fused.

Results: The antepsoas (n=20) and transpsoas (n=13) cohorts were equivalent in demographic data, including age and sex. Median levels of fusion for both groups equaled 1 (p=0.236). Although the preoperative foraminal height was equivalent between the two cohorts (p=0.438), postoperative foraminal height approached, but did not reach, a statistically significant difference (18.1 mm transpsoas cohort versus 15.5 mm antepsoas cohort, p=0.078). An increase in foraminal height of 2.8 mm in the transpsoas cohort was greater than 1.1 mm in the antepsoas cohort (p=0.006). Changes in lumbar lordosis, sagittal vertical axis, and pelvic tilt did not change between both groups. Preoperative pelvic and sacral slope were equivalent.

Conclusion : Antepsoas and transpsoas approaches achieve equivalent radiographic outcomes, except for the greater foraminal height restoration with the transpsoas. This likely owes to the more posterior placement of the interbody with the transpsoas operation, which should be considered in patients with significant foraminal stenosis.