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.

BACKGROUND CONTEXT: 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.

PURPOSE: To investigate whether age-adjusted PI-LL overcorrection independently increases the risk of PJF after accounting for potential confounders.

STUDY

DESIGN

Retrospective cohort study using prospectively collected data from a single tertiary spine center.

PATIENT SAMPLE: 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.

OUTCOME MEASURES: PJF, defined as structural failure including proximal junctional angle ≥20°, vertebral fracture, fixation failure, myelopathy, or revision surgery.

METHODS

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.

RESULTS

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=.004). However, after adjustment, age-adjusted PI-LL correction was no longer associated with PJF risk. Advanced age (odds ratio [OR]=1.075, p=.048), lack of transverse process hook fixation (OR=5.225, p=.001), and high preoperative thoracic kyphosis (OR=1.046, p=.003) were independent risk factors for PJF.

CONCLUSIONS

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.