[1] Univ Pavia, Dept Clin Surg Diag & Pediat Sci, Locomotor Syst Dis Unit, I-27100 Pavia, Italy
[2] Citta Pavia Inst, Orthoped & Traumatol Unit, I-27100 Pavia, Italy
[3] Citta Pavia Inst, Outpatient Ultrasound Serv, I-27100 Pavia, Italy
[4] Hlth Protect Agcy Pavia ATS Pavia Italy, Epidemiol Unit, I-27100 Pavia, Italy
[5] Univ Pavia, Dept Publ Hlth Expt & Forens Med, Lab Adapted Motor Act, I-27100 Pavia, Italy
[6] Univ Milan, Dept Biomed Surg & Dent Sci, Via Festa Perdono 7, I-20122 Milan, Italy
[7] AON SS Antonio & Biagio & Cesare Arrigo, Childrens Hosp, Pediat Orthoped & Traumatol Unit, I-15121 Alessandria, Italy