Apical Vertebral Translation as a Coronal Risk Factor for Side-Specific Hip Osteoarthritis in Adult Degenerative...

Study designA retrospective cross-sectional study.ObjectivesTo evaluate the impact of coronal plane imbalance in adult degenerative scoliosis (ADS) on the severity and side-specific pattern of hip osteoarthritis (OA).MethodsPatients older than 50 years with Cobb angle >10° who underwent preoperative EOS images were retrospectively recruited. Hip OA severity was assessed using Kellgren-Lawrence (KL) grades and categorized into mild (KL <3 bilaterally) or severe (≥ one hip with KL ≥3). Coronal parameters-including Cobb angle, apical vertebral translation (AVT), pelvic obliquity (PO), and coronal balance distance-along with sagittal spinopelvic parameters were measured. Associations between radiographic variables and OA severity (worse, concave, and convex sides) were evaluated using Spearman correlation and multivariate logistic regression.ResultsAmong 189 patients, those with severe hip OA demonstrated significantly greater AVT and PO despite similar Cobb angles. AVT correlated with worse-side OA (r = 0.259, P < 0.001), convex-side OA (r = 0.154, P = 0.034), and concave-side OA (r = 0.246, P < 0.001); PO correlated with worse-side and concave-side OA. Logistic regression identified AVT as an independent risk factor for worse-side (OR 1.062) and concave-side OA (OR 1.077), whereas Cobb angle appeared protective for convex-side OA (OR 0.942). Sagittal parameters (PT, PI-LL, SVA) were also elevated in severe OA patients, consistent with hip-spine compensatory mechanisms.ConclusionCoronal imbalance in ADS, particularly increased AVT and pelvic obliquity, is associated with the severity and asymmetry of hip OA independent of Cobb angle magnitude. AVT may serve as a radiographic marker for identifying ADS patients at higher risk of asymmetric hip degeneration.