Use of pelvic incidence to predict proximal junctional failure in long-segment spinal fusion

OBJECTIVE: The objective of this study was to evaluate the impact of pelvic incidence (PI) on spinopelvic correction and complication rates following surgical correction of adult spinal deformity. METHODS: The authors conducted a retrospective analysis of a prospectively maintained database and identified 204 patients who underwent long-segment thoracolumbar fusions with pelvic fixation and a minimum of 1-year follow-up for deformity correction defined by the Scoliosis Research Society (SRS)-Schwab criteria. Patients were dichotomized into lower (108 patients) and higher (96 patients) PI groups on the basis of the mean value of 55°. Patient demographic characteristics, spinopelvic parameters, and complications were compared using univariate, multivariate, and mixed-effect analyses. RESULTS: Patients with higher PI demonstrated significantly lower rates of proximal junctional failure (PJF) than the lower PI group (9% vs 21%, p = 0.019). In particular, lower rates of PJF were found in patients with an upper thoracic upper instrumented vertebra (UIV) (0% vs 15%, p = 0.014). Multivariate analysis revealed that lower PI (OR 4.3, 95% CI 1.5-15.4, p = 0.006), lower thoracic UIV (OR 6.5, 95% CI 1.8-24.0, p = 0.005), and reoperation status (OR 23.8, 95% CI 5.8-97.8, p = 0.001) independently predicted PJF while controlling for significant differences. Bayesian mixed-effects modeling confirmed lower PI (OR 6.25, 95% credible interval [CrI] 1.52-50.0, posterior probability = 0.996) and lower thoracic UIV (OR 7.03, 95% CrI 1.6-76.0, posterior probability = 0.997) as significant predictors of PJF while controlling for random effects between patients. CONCLUSIONS: Patients with lower PI are at an increased risk of PJF following long-segment fusion. Preoperative PI morphology may be used to inform surgical planning and reduce the risk of junctional pathologies.