1. Department of Orthopedics and Traumatology, Medical University- Sofia, Bulgaria
2. Diagnostische und interventionelle Radiologie, Chirurgisches Klinikum München Süd, Germany
3. Chirurgisches Klinikum München Süd, Head Department of Endoprosthetics, Germany
4. Kinov Medical University-Sofia, Head Department of Orthopedics, University Hospital Queen Giovanna—ISUL, Bulgaria