1. Department of Orthopaedics, Shandong Provincial Hospital Affiliated to Shandong University, Ji’nan, P.R. China,
2. Department of Orthopaedics, Affiliated Hospital of Taishan Medical University, Taian, P.R. China, and
3. Department of Orthopaedics, General Hospital of Ji’nan Military Command, Ji’nan, P.R. China