ulnar nerve dislocation

The elbow:
review of anatomy and common collateral ligament complex pathology using MRI. Four different patients with recurrent painful click in the elbow. Sagittal T2-weighted MRI (a), sagittal FS PD-weighted MRI (b), axial FS PD-weighted MRI (c), and axial T1-weighted MRI (d) showing synovial osteochondromatosis (a), a posterolateral plica (b), an ulnar nerve subluxation (c), and hypertrophy of the medial head triceps (d)
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Ulnar nerve dislocation is an uncommon cause of pain and paresthesias in the ulnar nerve distribution. It occurs if the ulnar nerve subluxates and then dislocates over the anterior aspect of the medial epicondyle during flexion and extension of the elbow.

Pathology

Ulnar nerve dislocation occurs in 16% of normal individuals . As the elbow is flexed or extended, the ulnar nerve dislocates over the anterior aspect of the medial epicondyle. A "snap" may be heard or felt. This motion may eventually result in ulnar neuropathy with characteristic pain and paresthesias along the ulnar nerve distribution.

Ulnar nerve dislocation is separate entity from snapping triceps syndrome, which is more uncommon. The nerve may dislocate in snapping triceps syndrome as well.

Radiographic features

Ultrasound

Ultrasound is the imaging modality of choice since it can dynamically image the relationship between the ulnar nerve and medial epicondyle during elbow flexion and extension.

To evaluate :

  • the transducer is placed transversely over the medial epicondyle, over the entrance to the cubital tunnel
  • the patient flexes the elbow
    • there is normally some movement of the ulnar nerve toward the apex of the medial epicondyle
    • dislocation occurs if there is translation of the ulnar nerve over the medial epicondyle
    • a snap may be heard or felt with the movement
  • evaluation of the ulnar nerve distal to the neuropathy may reveal a swollen and hypoechoic nerve, characteristic ultrasound findings in ulnar neuropathy.
MRI
  • ulnar neuropathy may be seen on standard elbow MRI, but a diagnosis of ulnar nerve dislocation can only be suggested with elbow MR in both the flexed and extended positions

Differential diagnosis

Possible differential considerations include

Siehe auch:
Assoziationen und Differentialdiagnosen zu Dislokation Nervus ulnaris:
Nervus
ulnaris
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