1. King’s College Hospital, Denmark Hill, London SE5 9RS, UK.
2. Southend General Hospital, Prittlewell Chase, Westcliff-on-Sea, Essex SS0 0RY, UK.
3. Institute of Orthopaedics, Royal National Orthopaedic Hospital Trust, Brockley Hill, Stanmore, Middlesex HA7 4LP, UK.