The use of a dorsal-distal portal in trapeziometacarpal arthroscopy.

An accessory dorsal-distal portal (D-2) was developed to improve the visualization of the medial aspect of the trapezium during an arthroscopic trapeziectomy. This portal is ulnar to the extensor pollicis longus tendon and 1 cm distal to the V-shaped cleft at the juncture of the index and thumb metacarpal bases. The entry site is marked before the tourniquet is elevated to allow palpation or Doppler ultrasound of the radial artery in the anatomic snuffbox. A 22-gauge needle is inserted with proximal, radial, and palmar angulation to penetrate the joint space, which is viewed from either the 1-R or 1-U portal. A small skin incision is made and is followed by the insertion of a blunt trocar and cannula. An anatomic dissection of 5 cadaveric hands revealed that branches of the superficial radial nerve passed within 3.2 mm, the radial artery was 3.8 mm away, the first dorsal metacarpal artery was within 2.8 mm of this portal, and the cephalic vein was within 2.8 mm of this portal. On average, the D-2 portal was 17.2 mm from the 1-U portal (range, 12 to 20 mm). This study provides a safe, standardized approach to the D-2 portal for trapeziometacarpal arthroscopy, which is useful for evaluation of the dorsal capsular ligaments, provides access to medial osteophytes during an arthroscopic partial trapeziectomy, aids in the reduction of intra-articular metacarpal base fractures, and facilitates triangulation of the instruments.