1. Department of Spinal Studies and Surgery, Queens Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
2. Department of Trauma and Orthopaedics, The Pulvertaft Hand Centre, The Royal Derby Hospital, Uttoxeter Road, Derby DE22 3NE, UK.
3. School of Biosciences, University of Birmingham, Birmimgham B15 2TT, UK.