NATURAL COURSE AND PREDICTION OF PROGNOSIS OF FEMORAL HEAD OSTEONECROSIS

Radiographic Analysis of the Location of the Lesion at the Neutral and Flexion Position in the Non-traumatic Osteonecrosis of the Femoral Head
S Tamaoki, T Atsumi, Y Hiranuma, T Kajiwara, Y Asakura, J Suzuki
Department of Orthopaedic Surgery, Fujigaoka Hospital, Showa University School of Medicine, Yokohama, Japan

Purpose: The progression of the collapse is influenced by the extent and location of the necrotic focus of the necrotic femoral head. We studied the extent of the extensive necrotic focus on the joint surface by the conventional antero-posterior radiographs of the neutral position, and antero-posterior radiographs 45 degrees flexion position. The deference of the lesion in these two kinds of radiographs was analyzed.

Patients and Methods: The conventional antero-posterior radiographs of the neutral position, and antero-posterior radiographs 45 degrees flexion positions 115 hip joints of 86 cases with non-traumatic osteonecrosis of the femoral head was obtained for this study. These 115 hips showed the extensive lesion and divided into two groups: TypeC-1, C-2 by classification of Specific Disease Investigation Committee under the auspicies of the Japanese Ministry of Health Labor and Welfare. Type C1 lesions occupy more than the medial 2/3, C2 extended laterally to the acetabular edge.

Results: On the neutral position, TypeC-1 was noted on 42 joint (36%). In these 42 hips, 13 joint showed TypeC-1 (30%) on 45 degrees flexion position. In contrast, 29 joint (70%) was TypeC-2. TypeC-2 on73 joint (64%) was shown on neutral position. In these 73 hips, Type C-2 was disclosed on 69 joints (95%) on 45 degrees flexion position, Type C-1 was noted on 4 hips (5%). From these results, we thought that location of the lesion on joint surface was varied on different positions.