All patients will be examined clinically preoperatively, at 3, 6, 12, 24 and 36 months and at maximum follow-up. Different score scales will be used to objectivate the clinical results (AOFAS, SF-36, VAS). X-rays and MRI scan will be also taken preoperatively, and MRI will be executed at 12, 24 and 36 months of follow-up. In particular, a new qualitative MRI called T2 mapping will be performed at 24 months.