1. Trauma and Orthopaedics, Croydon University Hospital, Croydon District, London CR7 7YE, UK
2. Hip Reconstruction Unit, University College Hospital London, Bloomsbury, London NW1 2BU, UK
3. America Hip Institute, Chicago, IL 60018, USA
4. Northwestern University, Chicago, IL 60208, USA
5. University Hospitals Coventry and Warwickshire, Clifford Bridge Rd, Coventry CV2 2DX, UK
6. Research Department, South West London Elective Orthopaedic Centre, London KT18 7EG, UK
7. Fourways Life Hospital, Johannesburg, South Africa