[1] Seoul Natl Univ Bundang Hosp, Dept Orthopaed Surg, Bundang Hosp, 82 Gumi Ro,173 Beon Gil, Sungnam 13620, Gyeonggi, South Korea
[2] Ajou Univ, Coll Nat Sci, Dept Math, Gyeonggi, South Korea
[3] Univ Toronto, Hosp Sick Children, Div Orthopaed, 555 Univ Ave,S-107, Toronto, ON M5G 1X8, Canada
[4] Univ Toronto, Hosp Sick Children, Child Hlth Evaluat Sci Program, 555 Univ Ave,S-107, Toronto, ON M5G 1X8, Canada