Association of age-adjusted pelvic incidence minus lumbar lordosis correction with long-term radiographic and clinical outcomes in adult spinal deformity surgery.

Objective: Adequate correction of sagittal spinal malalignment is crucial in adult spinal deformity (ASD) surgery. Although the age-adjusted pelvic incidence (PI)-lumbar lordosis (LL) scheme has been widely used for ideal sagittal correction, its association with long-term surgical outcomes is not well documented. Therefore, the authors aimed to evaluate the association of age-adjusted PI-LL correction with long-term radiographic and clinical outcomes.

Methods: The authors included patients who underwent ≥ 5-level fusion including the sacrum for ASD between 2012 and 2023. The patients were categorized into three groups according to the correction status relative to the age-adjusted PI-LL target, as follows: undercorrection, matched correction, and overcorrection. The proximal junctional kyphosis/failure (PJK/F) rates, radiographic results, and clinical outcomes, including visual analog scale for back pain, Oswestry Disability Index (ODI), and Scoliosis Research Society (SRS)-22 scores, were compared between the PI-LL correction groups. To investigate the influence of PJK/F on the outcomes, patients with and without PJK/F were analyzed separately.

Results: Altogether, 384 patients were included in the study (mean age 69.0 years, mean total fused levels 7.9 levels, and mean follow-up duration 43.1 months). At 6 weeks postoperatively, all sagittal parameters were significantly more pertinently corrected in the overcorrection group than in the undercorrection and matched correction groups. PJK/F developed more frequently in the overcorrection group than in the undercorrection and matched correction groups. Final correction status, except the sacral slope, was more robust in the overcorrection group than in the undercorrection and matched correction groups. In the overall study cohort, the final ODI and SRS-22 scores were significantly better in the matched correction group than in the undercorrection and overcorrection groups. In the subgroup analysis, the clinical outcomes were comparable between the matched correction and overcorrection groups even with the exclusion of PJK/F.

Conclusions: Overcorrection relative to the age-adjusted PI-LL was associated with an increased risk of PJK/F. Clinical outcomes, such as ODI and SRS-22 scores, at the final follow-up were significantly better in the matched correction group than in the other correction groups. Even in the subgroup analysis excluding PJK/F, overcorrection did not provide any additional clinical benefit compared to matched correction.