The association between spinopelvic alignment and non-traumatic femoral head AVN: a case-control radiographic study.

Abstract

Background: Non-traumatic avascular necrosis (AVN) of the femoral head is primarily attributed to vascular compromise; however, the potential role of spinopelvic alignment in its development remains insufficiently defined. This study aimed to evaluate whether sagittal spinopelvic parameters differ between patients with non-traumatic AVN and asymptomatic individuals.

Methods: A retrospective case-control radiographic study was performed including 21 adults with bilateral Ficat-Arlet stage II-III non-traumatic AVN and 100 age- and sex-matched asymptomatic controls. Standardised standing full-length lateral radiographs were analysed to measure pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA). Spinopelvic morphology was classified using the Roussouly and Barrey systems. Interobserver reliability was evaluated using intraclass correlation coefficients (ICC), and statistical significance was set at p < 0.05.

Results: Patients with AVN demonstrated significantly lower PI, PT, SS, and LL values compared with controls (all p < 0.01), whereas TK did not differ significantly between groups. Although no statistically significant differences were observed in the distribution of Barrey and Roussouly types, a higher prevalence of Roussouly type 3 morphology was noted in the AVN cohort. Sex-related differences evident in the control group were not observed among AVN patients, and age showed minimal association with sagittal parameters. Inter-observer reliability was excellent for all measurements (ICC > 0.90).

Conclusions: Patients with non-traumatic AVN exhibit a distinct spinopelvic alignment profile characterised by reduced PI-derived sagittal parameters and limited compensatory pelvic orientation. These findings indicate that altered lumbopelvic biomechanics may be associated with increased mechanical stress on the femoral head and may reflect a biomechanical profile linked to AVN susceptibility. Further prospective studies are warranted to clarify the clinical implications of this association.