[Inter-observer agreement on the Eaton-Littler classification of trapeziometacarpal joint osteoarthritis]. 
To study the concordance of the radiographic classification of Eaton-Littler for the diagnosis of basal thumb joint osteoarthritis (BTJO).  The null hypothesis was that the concordance was due to chance and the alternative was that the concordance was not due to chance.  We have observed the x-rays of 46 patients with symptoms and clinical signs of BTJO.  They were independently classified by five physicians: three experts in upper extremity, one in radiology and a fourth year resident of Orthopedics.  We studied the concordance in the observations through the global Kappa.  The diagnosis of BTJO is based primarily on clinical exploration, radiology is a complementary method of confirmation.  The classification of Eaton-Littler proposes 4 stages of the disease, with a therapeutic involvement.  The concordance of the radiographic classification of Eaton-Littler is moderate.