Ulnar nerve dislocation
Numbness ulnar side of left hand for several months.
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Normal appearance of the left ulnar nerve with a homogeneous echo-texture. No focal thickening. Cross sectional area of 5 mm2.
On dynamic flexion and extension scanning of the elbow, however, the ulnar nerve is subluxing over the medial epicondyle resulting in an ulnar nerve dislocation (video).
Ultrasound, being a real time study, is the imaging modality of choice for diagnosing ulnar nerve dislocation over the medial epicondyle during dynamic flexion and extension of the elbow. The transducer should be placed transversely between the olecranon and the medial epicondyle during the dynamic maneuver. It is important to ensure light transducer pressure is applied, otherwise we might prevent the ulnar nerve from sliding over the medial epicondyle. A snap was felt with the movement.