The authors study the position of the median nerve at the time of endoscopic carpal tunnel release surgery in 93 hands. Distance measurements between the nerve and palmaris longus tendon and between adjacent wrist flexor tendons were made 1 cm proximal to the distal wrist crease. The authors found that the median nerve extended ulnar to the palmaris longus tendon in 88% of hands. In order to avoid injury to the median nerve (and ulnar nerve) during a carpal tunnel steroid injection, the authors proposed inserting the needle through the flexor carpi radialis tendon, 1 cm proximal to the distal wrist crease and directed at a 45 degree angle ulnarward.
The optimal technique for administering a steroid injection into the carpal remains controversial. An injection between the palmaris longus and flexor carpi ulnaris tendons has been recommended by some, between the palmaris longus and flexor carpi radialis tendon by others, as well as through the flexor carpi radialis tendon. The authors of this report their technique in 40 cases, but present only limited outcome data. It appears that variability of the median nerve makes nerve injury something to consider when administering an injection for carpal tunnel syndrome. Most likely, the nerve is closer than we think in many cases, regardless of technique.
Journal of Hand Surgery