144 Influence of Cage Type and Dimensions on Realized Segmental Lordosis in Patients Undergoing Transforaminal Lumbar Interbody Fusion

INTRODUCTION: Transforaminal lumbar interbody fusion (TLIF) is a common surgical technique used to improve indirect decompression along with sagittal plane correction in the form of segmental lordosis. However, for many it is a kyphosing operation and the cage parameters and intraoperative techniques that help maximize sagittal correction are unclear. METHODS: Patients treated with 1-/2-level TLIF at a single tertiary care center for degenerative pathologies with minimum 6-week radiographic follow-up were identified. Changes in segmental lordosis of the implanted segmented from pre- to postoperative were assessed. Univariable comparisons were made between patients implanted with banana-type and bullet-type devices. Multivariable linear regression was performed to identify independent predictors of postoperative segmental lordosis and change in segmental lordosis. RESULTS: 199 patients (mean 65.5 ± 9.6 yr; 43.2% male) treated at 239 levels were included. 104 levels were implanted with bullet-type cages and 135 with banana-type with an average change in segmental lordosis of 2.3 ± 6.2°. Comparison of patients implanted with banana- and bullet-type devices showed significantly greater postoperative disc height at the mid-disc (8.8 ± 3.1 vs 7.1 ± 2.3; p=0.001) and posterior disc (6.0 ± 2.9; 4.8 ± 1.9; p<0.001) for banana type devices. Average postoperative segmental lordosis was also greater for those implanted with banana-type devices (15.5 ± 7.0 vs 11.9 ± 6.3°; p<0.001). Multivariable linear regression showed that independent predictors of change in segmental lordosis were preoperative segmental lordosis (β -0.45° per degree; [-0.549, -0.340]; p<0.001), higher pelvic incidence (β = 0.094° per degree; [0.035, 0.154]; p=0.02), and use of a bullet-type vs banana-type cage (β = -2.544°; [-3.952, -1.135]; p<0.001). CONCLUSIONS: Banana-type interbodies were associated with significantly greater increases in lumbar segmental lordosis and the use of properly placed banana-type devices may offer the best means of sagittal plane correction in patients undergoing TLIF.