Trough line sign

The trough line sign is a sign of posterior shoulder dislocation on AP films. 

In posterior dislocation, the anterior aspect of the humeral head becomes impacted against the posterior glenoid rim. With sufficient force, this causes a compression fracture on the anterior aspect of the humeral head. This compression fracture is analogous to the Hill-Sachs compression fracture seen with anterior shoulder dislocation of the glenohumeral joint. 

Frontal radiographs reveal two nearly parallel lines in the superomedial aspect of the humeral head.

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Article information

rID: 12244
Section: Signs
Tags: refs, cases
Synonyms or Alternate Spellings:

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