The safest location for steroid injection in the treatment of carpal tunnel syndrome.

Steroid injections are routinely performed for carpal tunnel syndrome. Direct needle injury of the median nerve is the major complication of these injections. The safest location of the injection remains controversial. The purpose of this study is to define safe guidelines to avoid nerve injury. The distances between the Median nerve, Palmaris Longus, Flexor Carpi Ulnaris and Flexor Carpi Radialis tendons were measured pre-operatively, 1cm proximal to the distal wrist crease in 93 endoscopic carpal tunnel releases. We found that the median nerve extended ulnarly beyond the Palmaris Longus tendon in 82 hands (88%). It is concluded that the median nerve is at risk if the injection is performed within 1cm on either the ulnar or radial side of the Palmaris Longus tendon. More ulnarly, there is risk to the ulnar pedicle. The safest location is to inject through the FCR tendon.