1. Department of Orthopaedic Surgery, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan
2. Department of Orthopaedic Surgery, Ibaraki Western Medical Center, 555 Otsuka, Chikusei 308-0813, Japan
3. Department of Orthopaedic Surgery, Ichihara Hospital, 3691 Osone, Tsukuba 300-3253, Japan
4. Department of Orthopaedic Surgery, Kenpoku Medical Center, Takahagi Kyodo Hospital, 1006-9 Kamiteduna-Agehocho, Takahagi 318-0004, Japan
5. Department of Orthopaedic Surgery, Tsukuba Central Hospital, 1589-3 Kashiwada-Cho, Ushiku 300-1211, Japan
6. Department of Orthopaedic Surgery, Showa General Hospital, 8-1-1 Hanakonagei, Kodaira 187-0002, Japan
7. Department of Orthopaedic Surgery, Moriya Daiichi Hospital, 1-17 Matsumaedai, Moriya 302-0102, Japan
8. Department of Orthopaedic Surgery and Sports Medicine, Tsukuba University Hospital Mito Clinical Education and Training Center, Mito Kyodo General Hospital, 3-2-7 Miyamachi, Mito 310-0015, Japan
9. Department of Orthopaedic Surgery, Ibaraki Seinan Medical Center Hospital, 2190 Sashima, Sakai 306-0433, Japan