1069 Disparities in Presentation and Outcomes of Symptomatic Proximal Junctional Kyphosis Based on Over and Under Correction in Adult Spinal Deformity Corrections

INTRODUCTION: Proximal junctional kyphosis(PJK) is prevalent after adult spinal deformity(ASD) surgery. METHODS: ASD patients fused from at least 5 levels from sacrum with 2Y data were included. Radiographic PJK (radPJK) was defined by Lafage et al. criteria. RadPJK and reoperation for PJK (reopPJK) were evaluated by summation of the Sagittal Age-Adjusted Alignment Score (SAAS) components (TPA, PT, PI-LL). SAAS score was matched (M) if between -1 and 1, under (U) if <-1, and overcorrected (O) if >1. RESULTS: 1065 patients met inclusion. O had earlier onset of radPJK and reopPJK relative to those U (p<.05). Multivariable analysis depicted increased O to have a progressively higher likelihood of radPJK, with O having 1.8x higher odds of radPJK and 5x higher odds of reopPJK compared to U (all p<.05). Increasing age and frailty in O were significant factors increasing the likelihood of reopPJK, whereas lower PI was for U.SAAS score of >2 and >5 increased the likelihood of radPJK and reopPJK respectively, while U to <-6 was for reopPJK. In those requiring reopPJK, U had worse ODI, SRS22r pain, appearance, and satisfaction at the time of occurrence(p<.05). Reoperation improved HRQLs, however to a lesser extent for those mismatched in SAAS. U had a lower MCID rate at 2Y for ODI, SRS22r activity, pain, appearance, and satisfaction (p<.05). PJK prophylaxis affected HRQLs to a greater extent in O relative to U, with 1.5x higher rate of reaching MCID(p<.05). CONCLUSIONS: Under-correction required greater malalignment based on age-adjusted targets, than overcorrection for the development of symptomatic PJK. Those overcorrected were more likely to have earlier and more severe PJK requiring reoperation, while those under-corrected presented with worse disability.