RÉSUMÉ
INTRODUCTION: Osteoarthritis of the trapeziometacarpal joint is one of the most common degenerative diseases of the hand for which a variety of surgical procedures have been developed. Arthroscopic techniques offer good results, although they have not been standardized. OBJECTIVE: To identify the main anatomical structures in relation to arthroscopy portals from the trapeziometacarpal joint and to determine their security area. MATERIAL AND METHODS: We conducted a transversal and descriptive study in which the anatomy was analyzed in seven cadaveric specimens. Fourteen thumbs were dissected after the arthroscopic portals were made. In all of the specimens the distance between the radial artery, the articular line and the arthroscopy portals was measured. RESULTS: The radial artery was found dorsal to the Extensor Pollicis Longus (EPL), 4-5 mm proximal to the dorsal arthroscopic portal, 4-8 mm to the articular line and 8-11 mm to the Extensor Pollicis Brevis (EPB). In two cases sensitive branches of the radial nerve were found through the dorsal portal. CONCLUSION: The anatomical evaluation defined a secure area for the dorsal portal between the EPL and the EPB. The proximal radial zone to the EPL must be avoided so that the dorsal branch of the radial nerve is not damaged.