1. Dept. of Orthopaedic Surgery, University of Tsukuba, Graduate school of Comprehensive Human Sciences, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
2. Showa University Hospital, 1-5-8, Hatanodai, Shinagawa, Tokyo 142-8666, Japan
3. Senpo Tokyo Kowa Hospital, 3-10-11, Takanawa, Minato-ku, Tokyo 100-8066, Japan