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

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.