Measurement of Necrotic Lesion in Osteonecrosis of Femoral Head

Purpose: The size of the necrotic lesion is known to be the most important prognostic factor in osteonecrosis of the femoral head (ONFH). We evaluated the accuracy and relationship of three different measuring methods of necrotic lesions for ONFH. Materials and Methods: Sixty hips that had ONFH were measured on an MRI by two orthopaedic surgeons using Steinberg, Kim, and modified Kerboul methods. Based on the lesion size of the necrosis as measured with the computerized Steinberg method, the hips were divided into Group I (small lesion: less than 15%), Group II (medium lesion: 15~30%), and Group III (large lesion: more than 30%). Data of the Kim and modified Kerboul methods were reclassified by statistical analysis according to the groups classified by the Steinberg method. Results: Average lesion size of Group I (16 hips) was 10.92%, the average size of Group II (33 hips) was 21.68%, and the average size of Group III (11 hips) was 36.80%. We established a new criteria of the Kim and modified Kerboul methods based on Steinberg. The Kim method was reclassified into Groups I (less than 18%), II (18~33%), and III (33% or more). And the modified Kerboul method was divided into Groups I (less than 200.6。 ), II (200.6~262.4。 ), and III (more than 262.4。 ) as well. Conclusion: New criteria for the Kim and modified Kerboul method would be a useful indicator for the prognosis and treatment plan in ONFH.