1. Orthopaedics and Traumatology Department, University of Perugia, 06126 Perugia, Italy
2. Institute of Motor Sciences, Department of Medicine and Surgery, University of Perugia, 06126 Perugia, Italy
3. Orthopaedics and Traumatology Department, S.Matteo degli Infermi Hospital, 06049 Spoleto, Italy