An anatomically contoured interbody cage is associated with reduced subsidence after oblique lumbar interbody fusion: a comparative cohort study.

Abstract

Background: This study compared subsidence and segmental lordosis correction between a novel anatomically contoured cage and a conventional wedge-shaped cage used for oblique lumbar interbody fusion (OLIF).

Research design and methods: This retrospective cohort included 38 patients undergoing OLIF at 60 levels with bilateral pedicle screw fixation. Subsidence was defined as ≥2 mm endplate penetration assessed on six-month computed tomography. Generalized estimating equations accounted for within-patient clustering and adjusted for minimum Hounsfield units, with additional adjustment for age or operated level in separate models.

Results: Subsidence occurred at 2/30 levels (6.7%) treated with the anatomically contoured cage and 10/30 (33.3%) treated with the conventional cage (p = 0.021). The conventional cage was associated with higher odds of subsidence in the primary model (odds ratio [OR] 5.45; 95% confidence interval [CI] 1.35-22.00; p = 0.017). This association remained significant after age adjustment (OR 4.68; 95% CI 1.02-21.46; p = 0.047), but not after operated-level adjustment (OR 4.44; 95% CI 0.80-24.68; p = 0.088). Subsidence was associated with less lordosis gain (adjusted difference -3.33°; 95% CI - 5.03 to -1.62; p < 0.001).

Conclusions: The anatomically contoured cage was associated with lower subsidence, but this association was sensitive to operated-level adjustment. The small sample and non-randomized design warrant cautious interpretation and prospective confirmation.