403 Reciprocal Changes in Sagittal Parameters Following Single Level L4-5 TLIF With Unilateral Versus Bilateral Facetectomy

INTRODUCTION: Lumbar fusion aims to effectively restore segmental lordosis (SL) at the operative level. Transforaminal lumbar interbody fusion (TLIF) is a common surgical technique for lordosis restoration and correcting spinal alignment, however, the relationship between operative-level SL restoration and changes in other radiographic parameters following TLIF has not been well elucidated. METHODS: This was a retrospective study of patients undergoing single-level TLIF at L4-5 with either unilateral or bilateral facetectomy at a single institution between 2016 and 2023. Radiographic measurements were obtained via pre-and postoperative scoliosis films. Linear regression analysis was performed for changes in radiographic parameters as a function of ΔL4-L5 SL. RESULTS: 52 total patients were analyzed: 18 unilateral and 23 bilateral facetectomy. In the unilateral facetectomy group, ΔL4-5 SL was positively associated with distal lumbar lordosis (r=0.542; p=0.020), ADH (r=0.694; p=0.001), and LDI (r=0.637; p=0.005). ΔL4-5 SL was negatively correlated with ΔL3-4 SL (r=-0.471; p=0.048), Δproximal lumbar lordosis (r=-0.523; p=0.026), Δ spondylolisthesis percentage (r=-0.469; p=0.049). In the bilateral facetectomy group, ΔL4-5 SL was positively correlated with ΔLL (r=0.362; p=0.0351), Δdistal LL (r=0.597; p=0.001), and ΔADH (r=0.339; p=0.05). CONCLUSIONS: The change in operative-level segmental lordosis was positively associated with a change in distal lumbar lordosis (LL) and change in anterior disc height (ADH) for patients undergoing unilateral or bilateral facetectomy with single-level TLIF. In the unilateral facetectomy group, however, ΔL4-5 SL was negatively correlated with Δ L3-4 SL and Δ proximal LL, indicating a potential compensatory mechanism proximal to the operative site that did not occur in the bilateral facetectomy group. Further investigation is warranted to distinguish radiographic, surgical, and clinical outcome differences between patients undergoing TLIF with unilateral versus bilateral facetectomy.