1. Department of Orthopaedic Surgery, University of Tokyo Hospital Branch, 3-28-6 Mejirodai, Bunkyo-ku, Tokyo 112, Japan.
2. Department of Orthopaedic Surgery, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tnnoudai, Tsukuba-shi, Ibaraki-ken, 305, Japan
3. Department of Orthopaedic Surgery, Tokyo Metropolitan Geriatric Hospital, 35 Sakae-chou, Itabashi-ku, Tokyo 173, Japan.