1. Department of UltrasoundAffiliated People's Hospital of Jiangsu University Zhenjiang 212002 P. R. China
2. Department of Medical UltrasoundShanghai General HospitalShanghai Jiaotong University School of Medicine Shanghai 200080 P. R. China
3. State Key Laboratory of High Performance Ceramics and Superfine MicrostructureShanghai Institute of CeramicsChinese Academy of Sciences Shanghai 200050 P. R. China
4. Department of OrthopedicsNo. 455 Hospital of PLAThe Second Military Medical University Shanghai 200052 P. R. China