# Anatomic Reversal of Shoulder Joint After Neck of Humerus Fracture

## TL;DR

A rare case of a shoulder joint reversing its anatomy after a fracture is reported, resembling a prosthetic replacement.

## Contribution

This is the first documented case of an acquired shoulder deformity mimicking a reverse polarity shoulder replacement.

## Key findings

- A unique post-traumatic reversal of the humeral head occurred after a humeral neck fracture.
- The shoulder retained functional integrity despite the anatomical reversal.
- The deformity closely resembles a prosthetic reverse polarity shoulder replacement.

## Abstract

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.