Abstract
Introduction: The progression of the collapse is influenced by the extent and location of the necrotic focus of the necrotic femoral head. The authors studied the extent of the necrotic focus on the joint surface by conventional antero-posterior radiographs in neutral position, and antero-posterior radiographs at the 45 degrees flexion position. The differences of the lesions in these two types of radiographs were analyzed.
Materials and Methods: The conventional antero-posterior radiographs of the neutral position, and the antero-posterior radiographs at the 45 degrees flexion positions in 115 hip joints of 86 patients with non-traumatic osteonecrosis of the femoral head were obtained for this study. These 115 hips showed extensive lesions and could be divided into two groups: Type C-1 or C-2 by classification of the Specific Disease Investigation Committee under the auspices of the Japanese Ministry of Health Labor and Welfare. Type C1 lesions occupy more than the medial 2/3 of the femoral head and C2 lesions extend laterally to the acetabular edge.
Results: At the neutral position, Type C-1 lesions were noted in 42 joints (36%). In these 42 hips, 13 showed Type C-1 (30%) at the 45 degrees flexion position. In contrast, 29 joints (70%) were Type C-2. Type C-2 lesions in 73 joints (64%) were shown in the neutral position. In these 73 hips, Type C-2 lesions were disclosed on 69 joints (95%) in the 45 degrees flexion position and Type C-1 was noted on 4 hips (5%).
Conclusions: Based on these results, the authors propose that location of the lesion on the joint surface varies with different hip positions.
The abstracts were prepared by Michael A. Mont, M.D. and Lynne C. Jones, Ph.D. Correspondence should be addressed to L. Jones at Good Samaritan Prof. Bldg., Suite 201, 5601 Loch Raven Blvd., Baltimore, MD 21239
