[1] Korea Univ, Ansan Hosp, Dept Orthoped, Ansan 425707, South Korea
[2] Korea Univ, Guro Hosp, Dept Orthoped, Ansan 425707, South Korea
[3] Korea Univ, Ansan Hosp, Dept Thorac & Cardiovasc Surg, Ansan 425707, South Korea
[4] Korea Univ, Anam Hosp, Dept Orthoped, Ansan 425707, South Korea