Does age-adjusted pelvic incidence minus lumbar lordosis overcorrection truly increase the risk of proximal junctional failure? A confounder-adjusted multivariate analysis in adult spinal deformity.

Abstract

Correction beyond age-adjusted pelvic incidence minus lumbar lordosis (PI-LL) targets (age-adjusted PI-LL overcorrection) is believed to increase the risk of proximal junctional failure (PJF) in adult spinal deformity (ASD) surgery. However, this association has not been analyzed after adjusting for confounding variables. To investigate whether age-adjusted PI-LL overcorrection independently increases the risk of PJF after accounting for potential confounders. Retrospective cohort study using prospectively collected data from a single tertiary spine center. A total of 177 patients who underwent lower thoracic (T8-T10) to sacropelvic fusion for ASD between 2015 and 2022, with a 2-year follow-up. PJF, defined as structural failure including proximal junctional angle ≥ 20°, vertebral fracture, fixation failure, myelopathy, or revision surgery. Patients were grouped by 6-week postoperative PI-LL status into under-, matched-, and over-correction groups based on age-adjusted PI-LL targets. Unadjusted and confounder-adjusted logistic regression analyses were conducted to evaluate the association between PI-LL correction and PJF. Confounding variables were those predictive of PJF and significantly imbalanced across correction groups. The unadjusted analysis showed a significantly higher PJF incidence in the overcorrection group compared to the matched correction group (47.2% vs. 27.1%, P = 0.004). However, after adjustment, age-adjusted PI-LL correction was no longer associated with PJF risk. Advanced age (odds ratio [OR] = 1.075, P = 0.048), lack of transverse process hook fixation (OR = 5.225, P = 0.001), and high preoperative thoracic kyphosis (OR = 1.046, P = 0.003) were independent risk factors for PJF. Overcorrection relative to age-adjusted PI-LL target does not independently increase PJF risk when key confounders are considered. Surgeons should focus on individual patient and surgical factors-particularly age, thoracic alignment, and prophylactic strategies-rather than relying solely on PI-LL correction thresholds in ASD surgical planning.