1. Department of Orthopaedics; University of Zurich; Balgrist University Hospital; Forchstrasse 340 Zurich 8008 Switzerland
2. Oxford University Hospitals; Oxford United Kingdom
3. Senior Lecturer Suez Canal University; Ismailia Egypt
4. Laboratory for Orthopaedic Biomechanics; Swiss Federal Institute of Technology in Zurich (ETHZ); Zurich Switzerland