Volar Midcarpal Portals in Wrist Arthroscopy

Purpose: To describe the placement of volar midcarpal portals using the inside-out technique, and the surrounding anatomical structures at risk. Methods: Five fresh-frozen cadavers were used. Volar ulnar midcarpal (VUMC) and volar radial midcarpal (VRMC) portals were placed using an inside-out technique. The distance between these portals to surrounding anatomical structures was measured in millimeters using a caliper. Results: The VUMC portal pierced the flexor digitorum profundus tendon to the middle finger in 1 specimen. The portal was an average 3.7 and 8.4 mm away from the ulnar artery and nerve, respectively. The VRMC portal pierced the palmaris longus in 2 specimens. It usually was between the flexor pollicis longus, the palmaris longus, and the median nerve. It was an average of 1.0 and 1.95 mm away from the median nerve and palmar cutaneous branch of the median nerve, respectively and in 1 specimen, was in contact with the median nerve after piercing the mesoneurium. Conclusions: With increasing use of volar midcarpal arthroscopy, the surgeon needs to have an understanding of the structures at risk when placing the VUMC and VRMC portals. Clinical relevance: When developing the volar midcarpal portals, the surgeon needs to pay close attention to the anatomical structures at risk and, in particular, the median nerve from the VRMC portal.