Assessing the Risk of Junctional Complications Following Undercorrection of Sagittal Vertebral Axis in Degenerative Scoliosis.

Abstract

Positive sagittal balance is a common manifestation of kyphoscoliosis and is associated with significant functional impairment and disability. While surgical correction of the sagittal vertical axis (SVA) can improve spinal alignment, it carries a risk of postoperative complications such as proximal junctional kypohosis (PJK) or failure (PJF). This study explores if age-adjusted undercorrection of SVA may decrease the risk of PJK/PJF relative to ideal or overcorrection. This was a single-institution retrospective analysis of patients with degenerative scoliosis who underwent instrumented fusion between 2009 and 2022 for sagittal imbalance. Patients were grouped based on age-adjusted SVA ideal-correction, undercorrection, or overcorrection. Postoperative outcomes were recorded, and PJK/PJF was evaluated at 3-month intervals up to 2 years postoperatively with risk factors assessed via multivariable logistic regression. Of 70 total patients, we identified three sub-groups: 32 with SVA undercorrection, 28 with ideal correction, and 10 with overcorrection. There were similar rates of number of levels fused across all three sub-groups (P = 0.420), and all 3 groups exhibited statistically significant radiographic improvements in spinal alignment (P <0.001). SVA undercorrection did not significantly alter the occurrences of radiographic-only PJK (38.6%; P = 0.400), symptomatic PJK/PJF (15.7%; P = 0.770), or 2-year reoperation risks (P = 0.18-0.65). Symptomatic PJK/PJF patients had a significantly higher 2-year reoperation rate compared to radiographic-alone (90.9% vs. 43.8%; P = 0.04). Among undercorrected patients, multivariable regression identified a 1.25× increased odds of symptomatic PJK/PJF with greater correction of lumbar lordosis (P = 0.03). While age-adjusted SVA undercorrection significantly improved spinal alignment, itdid not significantly alter the risk of PJK/PJF compared to ideal or overcorrection. This may support the ability to reduce surgical morbidity with less extensive deformity correction while maintaining surgical outcomes.