Comparison of carpal tunnel injection techniques: a cadaver study.

The purpose of the study was to evaluate the accuracy of injections into the carpal tunnel using three different portals in cadavers, and to define safe guidelines. In this study, 150 wrists of 75 cadavers (54 male, 21 female) were included. To compare three injection sites, 50 wrists of 25 cadavers were used for each technique; we used 23 gauge needles, and acrylic dye. The first injection technique: the needle was inserted 1cm proximal to the wrist crease and directed distally by roughly 45 in an ulnar direction through the flexor carpi radialis tendon. The second injection technique: the needle was inserted into the carpal tunnel from a point just ulnar to the palmaris longus tendon and 1cm proximal to the wrist crease. The third injection technique: the needle was inserted just distal to the distal skin crease of the wrist in line with the fourth ray. The first injection technique gave the highest accuracy rate, and this was also the safest injection site. Median nerve injuries caused by injection was seen mostly with the second technique. Although a steroid injection may provide symptomatic relief in patients with carpal tunnel syndrome, the median nerve and other structures in the carpal tunnel are at risk of injury. Because of that, the injection should be given using the correct technique by physicians skilled in carpal tunnel surgery.