Feasibility of ultrasound-guided ulnar nerve injections at the cubital tunnel using a lateral-to-medial approach

Purpose: Describe an alternative approach to perform ultrasound-guided injections into the cubital tunnel as a pilot study for cubital tunnel syndrome (CTS) treatment feasibility. Methods: The ulnar nerve was visualized bilaterally on four non-embalmed cadaveric models which were placed in a supine position. To image the cubital tunnel, the subject's elbow was examined in external rotation with the elbow angle at approximately 40° flexion (full elbow extension is considered 0°). The ultrasound transducer was placed transverse to the condylar groove along the medial epicondyle-olecranon axis and the ulnar nerve was identified. Methylene blue 0.35 mL was injected into the ulnar nerve perineural space under ultrasound guidance in a lateral-to-medial approach. Post-injection incisions were made to expose the underlying ulnar nerve and examine the injection sites. Injections were considered accurate if the ulnar nerve perineural space was dyed, and were considered precise if the injection was localized without damaging the ulnar collateral artery. Results: Dissection revealed that the ulnar nerves were covered with dye from the cubital tunnel inlet to outlet. 8-of-8 (100%) injections were accurate; 8-of-8 (100%) injections were precise. Conclusion: This pilot study shows that a lateral-to-medial approach to injecting the cubital tunnel under ultrasound guidance is accurate and precise. The clinical efficacy of such a procedure using corticosteroids should be examined through clinical trials and the results should be compared to other techniques used for treating CTS.