Thumb carpometacarpal arthroscopy: a topographic, anatomic study of the thenar portal.

Arthroscopic treatment of osteoarthritis of the thumb carpometacarpal joint has been well described; however, the current site of the 2 working portals, especially the 1-R portal, may be complicated by neurovascular morbidity. This is owing to the close proximity of these portals to important nerves and vessels surrounding the carpometacarpal joint. We studied 7 cadaveric wrists to map out the topographic, anatomic, and arthroscopic position of a new thenar portal. We hypothesized that it would increase considerably the safe zone distances of the portal from vital structures of the joint compared with the traditional portals. This study showed that the thenar portal increases considerably the safe zone of the portal from the sensory branches of the radial nerve and the radial artery and does not put the motor branch of the median nerve at risk. In addition the thenar portal allows for better visualization of the carpometacarpal joint, which leads to improved ability to perform arthroscopic trapeziectomy.