1. Principal Physicist, Department of Medical Physics and Clinical Engineering, Royal Hallamshire Hospital, Sheffield S10 2JF, England.
2. Registrar, Department of Orthopaedics, Northern General Hospital, Sheffield, England.
3. Consultant Orthopaedic Surgeon, Department of Orthopaedics, Northern General Hospital.
4. Senior Lecturer in Orthopaedics, Manchester University, Manchester, England.
5. Professor and Head of Department of Orthopaedics, University of Sheffield, Royal Hallamshire Hospital.