The impact of preoperative lordosis distribution index on postoperative sagittal alignment and outcomes after lumbar fusion surgery for degenerative spine disease.

PURPOSE: The purpose of this study is to evaluate the impact of preoperative LDI on postoperative sagittal alignment and surgical/patient-reported outcomes (PROMs) in a degenerative cohort. METHODS: Patients who underwent 1–2 level elective primary lumbar fusion (2014–2020) for degenerative disease were retrospectively identified. Preoperative/postoperative radiographs were reviewed for global, upper (L1-L3) and lower (L4-S1) LL, pelvic-incidence (PI), PI-LL mismatch, and pelvic tilt (PT). PI-LL mismatch and PT were assessed based on the literature. LDI was calculated as lower LL/global LL. Patients were categorized into preoperative hypolordosis (LDI < 0.5), normal (LDI 0.5–0.8), and hyperlordosis (LDI > 0.8) groups. RESULTS: 267 patients were included (87 hypolordosis/149 normal/31 hyperlordosis). Age and male percentage increased across groups. Average length of follow-up was similar between LDI groups. The hypolordotic group received more anterior lumbar interbody fusions (ALIF) and had more cranial fusion. Postoperative LDI groups were aligned with preoperative LDI groups—hyperlordotic patients had the most LDI improvement (-0.06; p = 0.004). Hyperlordotic patients had the most postoperative PI-LL above 10° (54.5%; p = 0.025), but all groups experienced PI-LL and PT improvements. Hospital length of stay (LOS) differed between groups, but multivariable regression showed this was attributable to age, ALIF, and levels decompressed. The preoperative hyperlordosis group had higher 90-day complication rates. CONCLUSION: LDI group does not appear to be independently associated with outcomes after lumbar fusion; limiting the utility of this measurement in degenerative cases. Although all LDI groups experienced postoperative improvements in alignment, hyperlordotic patients tended to have persistent PI-LL mismatch.