General Session: Adult Spinal Deformity - Hall F

Presented by: K. Jegede

Author(s):

K. Jegede(1), J. Tishelman(1), G. Poorman(1), N. Stekas(1), L. Steinmetz(1), P. Passias(1), T. Errico(1), A. Buckland(1), T. Protopsaltis(1)

(1) NYU Langone Orthopedic Hospital, New York, NY, United States

Abstract

Introduction: Iatrogenic flatback deformity is a common cause of sagittal malalignment resulting in disability and revision surgery. Though not well described, repeat smaller fusions can result in SSD. Few studies report the effect of short lumbar fusions on overall balance and PI-LL mismatch. This study aims to evaluate PI-LL mismatch and SL deficits in degenerative lumbar surgery to investigate whether surgery for degenerative deformity (consisting of 1 to 4 level fusions) restores alignment or generates deformity.

Methods: Regional and global alignment was assessed in patients undergoing 4-level fusions or less with full body X-rays. Ideal overall lumbar lordosis was calculated using PI. The LL deficit was defined as Expected Lordosis-Postop Lordosis. The ideal percentage of segmental lumbar lordosis was obtained from previously published norms. Sub analysis was performed by surgical technique at each level. Chi squared test and T tests were used for categorical and continuous variables respectively, as well as multivariate ANOVA analysis.

Results: 296 total lumbar fusion levels in 114 patients were included (mean age 59y, 67%female). There was no significant change in SL or in the LL deficit pre to postop. 53.1% of patients had PI-LL>9 vs 44.3% postop. There was no significant change in global alignment (pre/post TPA=21.3 vs 20.4 , p=.14), 52.5% of patients had global SSD (TPA>20°). At baseline and follow up, L5-S1 had the greatest lordosis deficit (pre 3.1°, post 3.0°). No SL or PI-LL differences were found between techniques (Mean lordosis change: ALIF 1.96°, TLIF -.825°, LLIF 3.03°, PSF 1.80°). Comparison of 1-2 and 3-4 level fusions did not show significant differences. When comparing lordosis in fused and unfused segments, lordosis improved in the fusion (pre/post: 29.3 vs 32.7, p=.001), but it was lost in adjacent unfused levels (pre/post: 16.7 vs 15.3, p=.044).

Conclusion: In Degenerative short-segment fusions whether ALIF, LLIF, TLIF or PLF was employed a significant number of patients exhibit residual PI-LL mismatch. More attention to regional and global alignment must be employed even in short segment fusions to avoid generating fixed sagittal deformity.