1. Department of Orthopaedic Surgery, Japan Labor Health and Welfare Organization Spinal Injuries Center, Iizuka, Fukuoka, Japan.
2. Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, Higashiku, Fukuoka, Japan.
3. Department of Rehabilitation Medicine, Japan Labor Health and Welfare Organization Spinal Injuries Center, Iizuka, Fukuoka, Japan.
4. Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Shimokasuya, Isehara, Kanagawa, Japan.