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 degrees and the maximum was 25 degrees. 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.