[1] IRCCS Ist Ortoped Rizzoli, Pediat Orthoped & Traumatol, I-40136 Bologna, Italy
[2] AOU Citta Salute & Sci Torino, Unit Clin Epidemiol, CPO Piemonte, I-10126 Turin, Italy
[3] IRCCS Ist Ortoped Rizzoli, Dept Rare Skeletal Disorders, I-40136 Bologna, Italy
[4] IRCCS Ist Ortoped Rizzoli, Clin Trial Ctr, I-40136 Bologna, Italy
[5] IRCCS Osped Pediatr Bambino Gesu, Dept Orthoped & Traumatol, I-00146 Rome, Italy