Clinical Significance of Lordosis Orientation on Proximal Junctional Kyphosis Development in Long-Segment Fusion Surgery for Adult Spinal Deformity

Abstract

To evaluate the clinical impact of lordosis orientation (LO) on proximal junctional failure (PJK) development in adult spinal deformity (ASD) surgery METHODS: This study included 152 patients who underwent low thoracic (T9 -T12) to pelvis fusion and followed up for ≥2 years. In the literature, six radiographic parameters representing LO were introduced, such as uppermost instrumented vertebra (UIV) slope, UIV inclination, UIV - femoral angle (UIVFA), thoracolumbar tilt, thoracolumbar slope, and lordosis tilt. Various clinical and radiographic factors, including six LO parameters, were investigated using logistic regression analysis to identify risk factors for PJK. The mean age was 69.4 years, and 136 patients were females (89.5%). PJK developed in 65 patients (42.8%). Multivariate logistic regression analysis revealed that only small postoperative pelvic incidence (PI) - lumbar lordosis (LL) (Odds ratio [OR] = 0.962, 95% CI : 0.929 - 0.996, P = 0.030) and large UIVFA (OR = 1.089, 95% CI : 1.028 - 1.154, P = 0.004) were significant for PJK development. UIVFA showed significantly positive correlation with pelvic tilt (CC = 0.509), thoracic kyphosis (CC = 0.384), and lordosis distribution index (CC = 0.223). UIVFA was also negatively correlated with sagittal vertical axis (CC = -0.371). However, UIVFA did not correlate with LL, PI-LL, or T1 pelvic angle. LO significantly increases the risk of PJK development in ASD surgery. Multivariate analysis revealed that smaller postoperative PI-LL and greater UIVFA were significant risk factors for PJK. Surgeons should avoid undercorrection as well as overcorrection to prevent PJK development.