Gian Luca Erre1, Marco Piras2, Maurizio Conti3, Giuseppe Passiu2. 1. Rheumatology Unit, Department of Clinical and Experimental Medicine, Azienda Ospedaliero Universitaria di Sassari, Viale San Pietro 8, 07100 Sassari, Italy. Electronic address: e.gianluca@libero.it. 2. Rheumatology Unit, Department of Clinical and Experimental Medicine, Azienda Ospedaliero Universitaria di Sassari, Viale San Pietro 8, 07100 Sassari, Italy. 3. Radiological Sciences Unit, Department of Clinical and Experimental Medicine, University of Sassari, Viale San Pietro, 07100 Sassari, Italy.