Abstract

BACKGROUND: The Association Research Circulation Osseous (ARCO) developed a novel classification for early-stage (pre-collapse) osteonecrosis of the femoral head (ONFH). We hypothesized that the novel classification is more reliable and valid when compared to previous three classifications: Steinberg, modified Kerboul, and Japanese Investigation Committee classifications.METHODS: In the novel classification, necrotic lesions were classified into three types: Type 1 is a small lesion, where the lateral necrotic margin is medial to the femoral head apex; Type 2 is a medium-sized lesion, with the lateral necrotic margin being between the femoral head apex and the lateral acetabular edge; and Type 3 is a large lesion, which extends outside the lateral acetabular edge. In a derivation cohort of 40 early-stage osteonecrotic hips based on CT imaging, reliabilities were evaluated using kappa coefficients, and validities to predict future femoral head collapse by chi square tests and receiver operating characteristic curve analyses. The predictability for future collapse was also evaluated in a validation cohort of 104 early-stage ONFH.RESULTS: In the derivation cohort, inter-observer reliability (k=0.545) and intra-observer agreement (63 to 100%) of the novel method were higher than the other three classifications. The novel classification system was best able to predict future collapse (p<0.05) and had the best discrimination between non-progressors and progressors in both the derivation cohort (AUC =0.692[0.522-0.863], p<0.05) and the validation cohort (AUC=0.742[0.644-0.841], p=2.46x10-5).CONCLUSIONS: This novel classification is a highly reliable and valid method of those examined. ARCO recommends using this method as a unified classification for early-stage ONFH.

View details for DOI 10.1016/j.arth.2022.02.009

View details for PubMedID 35151809