1. Department of Orthopaedics and Spine Surgery, Krankenhaus Mechernich, Mechernich, Germany
2. Clinical Research, Alsbach, Germany
3. Faculty of Medicine, Alexandria University, Alexandria, Egypt
4. Department of Orthopaedics and Spine Surgery, Wadi el Neel Military Hospital, Cairo, Egypt
5. Department of Orthopaedics and Trauma Surgery, University Hospital Bonn, Bonn, Germany