1 Department of Orthopaedic Surgery, Shinshu University School of Medicine, Matsumoto, Nagano, and Department of Orthopaedic Surgery, Hokkaido University School of Medicine, Sapporo, Hokkaido, Japan mhayashi@shinshu-u.ac.jp.
2 Department of Orthopaedic Surgery, Shinshu University School of Medicine, Matsumoto, Nagano, and Department of Orthopaedic Surgery, Hokkaido University School of Medicine, Sapporo, Hokkaido, Japan.