[1] Orthopaedic Department, Bologna University, Istituto Ortopedico Rizzoli, Via G.C. Pupili 1, IT 40136 Bologna, Italy
[2] Biomechanics Lab., Bologna University, Istituto Ortopedico Rizzoli, Via G.C. Pupili 1, IT 40136 Bologna, Italy
[3] Department of Orthopedics, University Hospital, Lund, Sweden