1. Department of Orthopaedic Surgery Saitama Red Cross Hospital, 8-3-33, Kamiochiai, Cyuuou-ku, Saitama-shi, Saitama-ken 338-8553, Japan.
2. Department of Orthopaedic Surgery, Adult Reconstruction Hip Service, Nissan Tamagawa Hospital, 4-8-1, Seta, Setagaya-ku, Tokyo 158-0095, Japan.