Working Diagnosis:
Right ulnar neuritis with subluxation of the ulnar nerve.

Treatment:
The patient was started in physical therapy initially for scapular stabilization. She had improvement in her shoulder strength, but continued to have noticeable snapping and pain with elbow extension after 4 weeks. She was referred to an Orthopedic surgeon and diagnosed ulnar nerve subluxation at terminal extension. Due to her symptoms preventing her from doing the things she enjoyed (gymnastics) she desired to proceed with surgery. A transposition of the ulnar nerve was completed without complications.

Outcome:
The patient reported persistent improvement in her symptoms at follow up appointments without complications from the surgery. She started a second course of physical therapy at 1 week post-op. While her pain gradually improved, she continued to notice a palpable pop with terminal elbow extension. She was progressed back to gymnastic activities and at 10 weeks post-op her pain had completely resolved. She continued to notice some snapping and the ulnar nerve could be palpated outside of the cubital tunnel. However, in the absence of significant symptoms and with return to full athletic activity, no further imaging, testing or evaluation was deemed necessary. The palpable pop was felt to be along the intermuscular septum or possibly medial border of distal triceps.

Editor's Comments:
This case posed a clinical challenge as this patient’s symptoms and exam created a very broad differential diagnosis with many potential red herrings (e.g. shoulder weakness, anconeus epitrochlearis). It would be interesting to hear more about her ultrasound findings. Was any ulnar nerve or triceps tendon subluxation appreciated with dynamic exam? Another way to assess for subluxation would be to compare flexion and extension MR views. While snapping at the elbow is most commonly a result of ulnar nerve dislocation over the medial epicondyle of the humerus, it can also be caused by a portion of the medial head of the triceps or an accessory triceps tendon. It is important to note that ulnar nerve and triceps dislocation are not mutually exclusive and can occur concomitantly. Standard MR and ultrasound imaging with the elbow in full extension often fail to diagnose the dynamic abnormalities that occur with these conditions. When the diagnosis is in question, dynamic imaging should be performed.

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