1. Department of Orthopaedics, Chang Gung Memorial Hospital, Chang Gung Medical & Engineering College, 5 Fu-Hsing Street, Kweishan, Taoyuan, Taiwan, Republic of China.
2. Department of Orthopaedics, Mayo Clinic/Mayo Foundation, Rochester, Minnesota 55905, USA.
3. Orthopaedic Biomechanics Laboratory, School of Medical, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2196, USA.