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

STUDY DESIGN: Retrospective cohort study. PURPOSE: 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. OVERVIEW OF LITERATURE: There is no clear evidence to dictate whether bilateral or unilateral cages promote superior radiographic or surgical outcomes in TLIF. METHODS: Patients >18 years old who underwent primary one- or two-level TLIFs at our institution were identified and propensity-matched 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. RESULTS: 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). CONCLUSIONS: 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.