Loss of normal half-moon overlap sign (shoulder)

Last revised by Bálint Botz on 21 Aug 2020

Loss of half-moon overlap sign, which does not really roll off the tongue, is a sign of posterior shoulder dislocation on AP radiographs. 

On a normal true anteroposterior image, there is a half-moon overlap between the humeral head and the glenoid. In a posteriorly dislocated shoulder, there is lateral displacement of the humeral head with respect to the glenoid (losing the half-moon overlap). 

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Cases and figures

  • Normal overlap of humerus and glenoid
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  •  Posterior dislocation
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  • Case 3
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