The authors studied the effects of soft-tissue swelling on rotational alignment of the small finger. The 4th intermetacarpal spaces in 3 of the authors’ non-dominant hands were injected with saline. Following injection, all 3 hands exhibited the appearance of internal rotation of the small finger. The mean change in rotation was 16 degrees with only 1 degree or less of abduction of the 5th metacarpal. There was no alteration in the plane of the nail with active finger extension.
This study shows that soft-tissue swelling in the 4th intermetacarpal space can cause a transient rotational deformity of the small finger in the absence of fracture. The pseudorotational deformity appears to occur at the level of the 5th metacarpophalangeal joint. True malrotation associated with a fracture should alter the plane of the small finger nail when the finger is extended.
J Hand Surg