Medial repair band: independent risk factor for collapse in traumatic osteonecrosis of the femoral head

Objective Femoral head collapse is closely associated with a poor prognosis in osteonecrosis of the femoral head (ONFH). This study aimed to evaluate the association between the MRI repair band and the progression to collapse in traumatic osteonecrosis of the femoral head (TONFH). Methods We retrospectively analyzed TONFH patients admitted from January 2016 to May 2023. The following clinical data were collected: patient age, sex, affected side, presence of complete fracture displacement, performance of emergency surgery, achievement of anatomical reduction, and other relevant clinical characteristics. Median follow-up was 44.5 months, with collapse >2 mm as the survival endpoint. Univariate and multivariate regression analyses assessed the association between MRI medial repair band and collapse. Inter-observer consistency was evaluated using Kappa test. We also analyzed the association between fracture displacement and MRI medial repair band. Results 148 TONFH patients were included [median age 46.50 years (IQR: 38.50–52.00); 67(45.27%) males, 81(54.73%) females]. Collapse occurred in 63 (collapse group) vs. 85 (non-collapse group). The interobserver reliability of the medial repair zone, as measured by the intraclass correlation coefficient (ICC), was 0.802.Multivariate analysis identified the medial repair band as an independent risk factor for collapse (OR: 13.350, 95% CI: 5.767–30.907; P < 0.001). Survival was significantly lower with a medial vs. lateral repair band ( P < 0.001). Garden type IV fracture was significantly associated with medial repair band formation (OR: 2.581, 95% CI: 1.304–5.106; P = 0.006). Conclusion The medial repair band on MRI is an independent risk factor for collapse in patients with TONFH; furthermore, Garden type IV is closely associated with the formation of the medial repair band. The MRI medial repair band is an imaging feature for assessing the risk of collapse in TONFH.