1. Department of Ageing, Neurosciences, Head-Neck and Orthopedics Sciences, Orthopedics and Trauma Surgery Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, 00168 Rome, Italy
2. Orthopedics and Trauma Surgery, Mater Olbia Hospital, 07026 Olbia, Italy
3. U.O.C. II Clinic of Orthopedics and Traumatology, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy
4. Department of Statistics and Quantitative Methods, University of Milano-Bicocca, 20126 Milan, Italy