1Orthopaedic Biomechanics Laborutory, Department of Orthopaedic Surgery, Charles A. Dana Research Institute, Beth Israel Hoypital and Harvard Medical School, Boston, Massuchusetts, U.S.A
2Department or Orthopedic Surgery, St. Josef Hospital and Ruhr University, Bochum, F.R.G
3Orthopedic Research Laboratory, Department of Orthopedic Surgery, State University of New York Health Science Center, Syracure, New York, U.S.A.