[1] Institute of Orthopedics,
[2] S. Cuore Catholic University,undefined
[3] Rome,undefined
[4] Italy,undefined
[5] Department of Medical and Surgical Specialty,undefined
[6] University of Perugia,undefined
[7] Perugia,undefined
[8] Italy,undefined
[9] A. Fa. R Fatebenefratelli Isola Tiberina,undefined
[10] Rome,undefined
[11] and Institute of Neurology,undefined
[12] S. Cuore Catholic University,undefined
[13] Rome,undefined
[14] Italy,undefined
[15] via Flaminia 217,undefined
[16] I-00196 Rome,undefined
[17] Italy e-mail: rpadua@mclink.it Tel.: +39-6-30154353,undefined
[18] Fax: +39-06-3219514,undefined