Working Diagnosis:
Common extensor tendon tendinosis, ulnar nerve subluxation, and laxity of the cubital tunnel retinaculum.

Treatment:
Treatment included prolotherapy injections and physical therapy.

Outcome:
After successful treatment of the lateral epicondylitis, she was still experiencing subluxation of the ulnar nerve. An ultrasound-guided injection of 2 mL of 12.5% Dextrose was performed along the cubital tunnel retinaculum. At 4 weeks post injection, she was experiencing mild pain and paresthesia and still had frequent subluxation. At 12 weeks post injection, she had subluxation 3-4 times a week.

Author's Comments:
Ulnar subluxation is an uncommon cause of elbow discomfort and pain. It is associated paresthesia of the forearm and of the 4th and 5th digits. It can be diagnosed with accuracy using ultrasound imaging. Prolotherapy is the injection of a natural irritant to induce an inflammatory process and promote healing. Prolotherapy has been used for ligamentous laxity but is not well studied, especially in the setting of hypermobility.

Editor's Comments:
The ulnar nerve is formed from the C8 and T1 nerve roots and provides motor and sensory innervation to the medial arm, forearm, and hand. During elbow flexion, the ulnar nerve is susceptible to subluxation or dislocation as is passes posterior to the medial epicondyle. During dislocation, the nerve fully translocates anterior to the medial epicondyle. Subluxation occurs when the nerve translocates anteriorly, but not past the tip of the medial epicondyle. Subluxation is relatively common and does not always produce symptoms. It can result from many causes, including ligamentous laxity. Subluxation may cause mechanical compression or traction, leading to ulnar nerve neuropathy. When evaluated sonographically, ulnar nerves that sublux have a 20% larger cross-sectional area than ulnar nerves that do not (3.1 mm x 1.9 mm compared to 2.7 mm x 1.8 mm).

References:
Bordes SJ Jr, Jenkins S, Bang K, et al. Ulnar nerve subluxation and dislocation: a review of the literature. Neurosurgical review. 2021;44(2):793-798.
Okamoto M, Abe M, Shirai H, Ueda N. Morphology and dynamics of the ulnar nerve in the cubital tunnel. Observation by ultrasonography. J Hand Surg Br. 2000 Feb;25(1):85-9.

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