Presentation
The patient injured his right hand while playing soccer. The patient had weak flexion and extension at the MCP and IP joints of the right thumb. The ulnar aspect of the thumb MCP joint was tender to palpation. There was pain and laxity with radial deviation at the thumb MCP joint.
Patient Data
Radiographs of the right hand show a mildly displaced small avulsion fracture of the thumb proximal phalanx base. This is separate from an adjacent sesamoid. There is no subluxation or dislocation.
MRI of the right thumb without IV contrast was obtained 5 days after the radiographs. The MRI demonstrates a tear of the ulnar collateral ligament (UCL) of the thumb MCP joint from its proximal phalanx insertion. The UCL is torn and retracted proximal to the adductor aponeurosis. This appearance can be described as a "yo-yo on a string" characteristic of a Stener lesion. Mild marrow oedema is seen in the volar aspect of the thumb metacarpal head and the sesamoids.
The avulsion fracture of the thumb proximal phalanx base is poorly visualised on this MRI. Increased signal in the volar plate of the thumb MCP joint is suggestive of volar plate injury. There is soft tissue oedema around the thumb MCP joint. The flexor and extensor tendons of the thumb are intact. Fluid signal around the extensor pollicis longus tendon is indicative of tenosynovitis. Wrap artifact is noted on the axial sequences.
Case Discussion
This patient's ulnar collateral ligament (UCL) rupture was treated surgically with ligament repair about 2 weeks after the original injury. Intraoperatively, it was confirmed that the UCL had ruptured from its insertion at the base of the proximal phalanx and that the adductor aponeurosis was partially torn. One suture anchor was used in the repair. At the most recent follow-up, the patient reported a near-complete resolution of pain.
It is estimated that approximately 200,000 UCL injuries of the thumb MCP joint occur annually in the US; ranging from mild sprains to complete ruptures 1. Ruptures were further described by Stener as being non-displaced or displaced in relation to the adductor pollicus aponeurosis. The latter is assigned the eponym, "Stener lesion" 1. The presence of a Stener lesion is an important finding, as it necessitates operative management. Since the adductor aponeurosis becomes interposed between the joint and the torn ligament, the ruptured ends of the UCL remain separated and do not heal with non-operative therapies 2.
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