K Kanaya1, T Wada2, T Yamashita2. 1. Department of Orthopedic Surgery, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan kkanaya@pop06.odn.ne.jp. 2. Department of Orthopedic Surgery, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan.