Anatomical Basis of Ulnar Approach in Carpal Tunnel Injection

Background: Local steroid injection may be an effective conservative treatment for carpaltunnel syndrome; however, the use of a blind injection technique can increase the chance ofmedian nerve or ulnar artery injury due to median nerve swelling or the close proximity of themedian nerve and ulnar artery around the distal wrist crease.Objectives: The purpose of this study is to investigate the relative location of the median nerveand ulnar artery to the palmaris longus (PL) tendon around the wrist in carpal tunnel syndrome.Study Design: An observational study.Setting: A university outpatient interventional pain management practice in the Republic ofKorea.Methods: Thirty hands of 15 patients with carpal tunnel syndrome and 30 hands of 15 healthysubjects were studied. Ultrasonography was performed to determine the relative relationship ofthe ulnar artery and median nerve to the PL tendon around the wrist.Results: There were statistically significant differences both in the distance from the medialmargin of the PL to the medial end of the median nerve and the distance from the medial endof the median nerve to the lateral end of the ulnar artery at all levels of scanning between the2 groups.Limitations: Limitations include the inclusion of a small number of patients with carpal tunnelsyndrome.Conclusion: It is important to recognize the risk of blind local steroid injection for carpaltunnel syndrome, which is most likely a result of swelling and/or flattening of the median nervearound the distal wrist crease. A real time, ultrasound-guided local steroid injection is preferredas a safe and accurate technique in carpal tunnel syndrome treatment.Key Words: Carpal tunnel syndrome, median nerve, ulnar artery, injection, steroid, injury,ultrasonography, risk, cross-sectional area