[1] Hokkaido Univ Hosp, Sapporo, Hokkaido, Japan
[2] Hokkaido Univ, Grad Sch Med, Dept Adv Med Spine & Spinal Cord Disorders, Kita Ku, North 15,West 7, Sapporo, Hokkaido 0608638, Japan
[3] Hokkaido Univ, Grad Sch Med, Dept Orthopaed Surg, Kita Ku, North 15,West 7, Sapporo, Hokkaido 0608638, Japan
[4] Orthopaed Hokushin Hosp, Dept Orthopaed Surg, Kikusuimotomachi 3-3, Sapporo, Hokkaido 0030823, Japan
[5] Japan Community Hlth Care Org Hokkaido Hosp, Dept Orthopaed Surg, Nakanoshima 1-8, Sapporo, Hokkaido 0628618, Japan