Anatomic Reversal of Shoulder Joint After Neck of Humerus Fracture.

We report on a singular case of a unique form of post-traumatic reversal of the humeral head after humeral neck fracture, in which the pattern of collapse resulted in the formation of a native reverse polarity shoulder. In essence, the humeral head became a socket, and the glenoid rounded to become a head with well-preserved shoulder function. To our knowledge, this is the first case of an acquired shoulder deformity that bears a remarkable functional similarity to a prosthetic reverse polarity shoulder replacement.