1. Sapporo Hand Surgery and Congenital Hand Differences Center, Orthopaedic Hokushin-Higashi Hospital, Sapporo, Japan.
2. Department of Orthopaedic Surgery, Yamagata University School of Medicine, Yamagata, Japan.
3. Department of Orthopaedic Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.