Anatomical Basis of Ulnar Approach in Carpal Tunnel Injection

Background: Local steroid injection may be an effective conservative treatment for carpal tunnel syndrome; however, the use of a blind injection technique can increase the chance of median nerve or ulnar artery injury due to median nerve swelling or the close proximity of the median nerve and ulnar artery around the distal wrist crease. Objectives: The purpose of this study is to investigate the relative location of the median nerve and 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 of Korea. Methods: Thirty hands of 15 patients with carpal tunnel syndrome and 30 hands of 15 healthy subjects were studied. Ultrasonography was performed to determine the relative relationship of the ulnar artery and median nerve to the PL tendon around the wrist. Results: There were statistically significant differences both in the distance from the medial margin of the PL to the medial end of the median nerve and the distance from the medial end of the median nerve to the lateral end of the ulnar artery at all levels of scanning between the 2 groups. Limitations: Limitations include the inclusion of a small number of patients with carpal tunnel syndrome. Conclusion: It is important to recognize the risk of blind local steroid injection for carpal tunnel syndrome, which is most likely a result of swelling and/or flattening of the median nerve around the distal wrist crease. A real time, ultrasound-guided local steroid injection is preferred as a safe and accurate technique in carpal tunnel syndrome treatment.