Pseudorotation of the little finger metacarpal

Fractures of the little finger metacarpal are common, and are often associated with significant soft-tissue swelling and the appearance of rotational malalignment when the fingers are flexed. Our hypothesis is that soft-tissue swelling causes this apparent rotational deformity of the flexed little finger. The fourth intermetacarpal spaces of three of the authors' non-dominant hands were injected with saline. Following injection, all the hands exhibited the appearance of internal rotation of the little finger. The mean change in rotation was 16° and the maximum was 25°. There was no change in the plane of the nail plate in extension in any hand. We conclude that soft-tissue swelling can cause the appearance of internal rotation of the flexed little finger in the absence of fracture.