1St Helens and Knowsley Hospitals NHS Trust, Department of Trauma and Orthopaedics, Merseyside, UK
2North Middlesex University Hospital, Department of Trauma and Orthopaedics, London, UK
3Southport and Ormskirk Hospitals NHS Trust, Department of Trauma and Orthopaedics, Southport, Merseyside, UK
4Northern General Hospital, Department of Trauma and Orthopaedics, Sheffield, UK