A Comparison of Radiographic Alignment between Bilateral and Unilateral Interbody Cages in Patients Undergoing Transforaminal Lumbar Interbody Fusion.

Abstract

Retrospective cohort study. To compare radiographic outcomes between unilateral and bilateral cage placement in transforaminal lumbar interbody fusions (TLIF) and to determine if the rate of fusion at the 1-year postoperative point was different in patients who received bilateral versus unilateral cages. There is no clear evidence to dictate whether bilateral or unilateral cages promote superior radiographic or surgical outcomes in TLIF. Patients >18 years old who underwent primary one- or two-level TLIFs at our institution were identified and propensitymatched in a 3:1 fashion (unilateral:bilateral). Patient demographics, surgical characteristics, and radiographic outcomes, including vertebral endplate obliquity, segmental lordosis, subsidence, and fusion status, were compared between groups. Of the 184 patients included, 46 received bilateral cages. Bilateral cage placement was associated with greater subsidence (1.06±1.25 mm vs. 0.59±1.16 mm, p=0.028) and enhanced restoration of segmental lordosis (5.74°±14.1° vs. -1.57°±10.9°, p=0.002) at the 1-year postoperative point, while unilateral cage placement was associated with an increased correction of endplate obliquity (-2.02°±4.42° vs. 0.24°±2.81°, p<0.001). Bilateral cage placement was significantly associated with radiographic fusion on bivariate analysis (89.1% vs. 70.3%, p=0.018) and significantly predicted radiographic fusion on multivariable regression analysis (estimate, 1.35; odds ratio, 3.87; 95% confidence interval, 1.51-12.05; p=0.010). Bilateral interbody cage placement in TLIF procedures was associated with restoration of lumbar lordosis and increased fusion rates. However, endplate obliquity correction was significantly greater for patients who received a unilateral cage.