A Glenohumeral Situation
Temple GEM of the Week By: Adria Simon Edited by: Alexei Adan, Danielle Betz & Maura Sammon
Case: A 39 year old M presented complaining of L shoulder pain after an assault. Pt was attempting to break up a domestic altercation and was thrown to the ground, struck with fists. On exam pt has significant tenderness of the L shoulder, limiting exam; 2+ radial pulse; intact sensation to light touch over axillary, median, ulnar, and radial nerves.
X-Rays shown below (AP, oblique, scapular-Y):
Q: What is the relevant finding on this X-ray and how is this finding managed?
A: This patient has a posterior shoulder dislocation.
Seen most commonly following seizures, electrocution, or direct trauma to anterior shoulder, posterior shoulder dislocations account for approximately 2-4% of shoulder dislocations. The findings are subtle on AP films due to a near normal alignment of the humeral head with the glenoid and the dislocation is better visualized on axillary or scapular-Y views. Commonly associated injuries: humeral surgical neck fracture, humeral tuberosity fracture, reverse Hill-Sachs lesion, labral tear, and rotator cuff tear.
Posterior shoulder dislocations are generally more difficult to reduce than anterior dislocations. One technique is the traction-countertraction, where one provider applies lateral axial (away from body) traction and external rotation to the humerus, and a second provider provides countertraction by wrapping a sheet around the patient’s torso.
As with all reductions, the goal is to disengage the two structures impinged against each other by exaggerating the deformity or distance between them. In this case, an additional provider can apply pressure to the humeral head in the posterior and lateral directions to help disengage the anterior humeral head from the posterior rim of the glenoid.
*See attached video: https://www.youtube.com/watch?v=KRCqVekNEKc
Findings associated with posterior shoulder dislocations on the AP X-Ray:
Lightbulb Sign: internal rotation of the humerus causes a rounded appearance of the humeral head
Trough Line Sign: vertical line on the medial aspect of the humeral head
Rim Sign: widening of the glenohumeral joint
Some associated findings include the reverse Hill-Sachs deformity, an impaction fracture of the anteromedial aspect of the humeral head.