The 2021 Association Research Circulation Osseous Classification for Early-Stage Osteonecrosis of the Femoral Head to Computed Tomography–Based Study

Kyung Hoi Koo, Michael A. Mont, Quanjun Cui, Jeremy T. Hines, Byung Ho Yoon, Wendy M. Novicoff, Yun Jong Lee, Edward Y. Cheng, Wolf Drescher, Philippe Hernigou, Shin Yoon Kim, Nobuhiko Sugano, De Wei Zhao, Yong Chan Ha, Stuart B. Goodman, Takashi Sakai, Lynne C. Jones, Mel S. Lee, Takuaki Yamamoto, Young Kyun LeeYusuhn Kang, James Burgess, Dennis Chen, Nicole Quinlan, Jian Zhong Xu, Jung Wee Park, Hong Seok Kim

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Background: The Association Research Circulation Osseous developed a novel classification for early-stage (precollapse) osteonecrosis of the femoral head (ONFH). We hypothesized that the novel classification is more reliable and valid when compared to previous 3 classifications: Steinberg, modified Kerboul, and Japanese Investigation Committee classifications. Methods: In the novel classification, necrotic lesions were classified into 3 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 computed tomography imaging, reliabilities were evaluated using kappa coefficients, and validities to predict future femoral head collapse by chi-squared 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, interobserver reliability (k = 0.545) and intraobserver agreement (63%-100%) of the novel method were higher than the other 3 classifications. The novel classification system was best able to predict future collapse (P < .05) and had the best discrimination between non-progressors and progressors in both the derivation cohort (area under the curve = 0.692 [0.522-0.863], P < .05) and the validation cohort (area under the curve = 0.742 [0.644-0.841], P = 2.46 × 10−5). Conclusion: This novel classification is a highly reliable and valid method of those examined. Association Research Circulation Osseous recommends using this method as a unified classification for early-stage ONFH. Level of Evidence: Level III, diagnostic study.

Original languageEnglish
Pages (from-to)1074-1082
Number of pages9
JournalJournal of Arthroplasty
Issue number6
StatePublished - Jun 2022

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© 2022 Elsevier Inc.


  • avascular necrosis
  • classification
  • femoral head
  • location
  • osteonecrosis
  • size


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