Hyperextension injury to the PIP joint or to the MP joint of the thumb--a clinical study.

We present a prospective study of the diagnosis and clinical course of 60 patients with 57 pure hyperextension injuries to the proximal interphalangeal (PIP) joint of the long fingers (fingers 2-5) and seven injuries to the metacarpophalangeal (MP) joint of the thumb. Thirty four of the injuries (57%) were related to ball sports, and the ulnar fingers of the non-dominant hand were usually affected. There were 24 avulsion fractures at the site of the insertion of the volar plate on to the middle phalanx. Twelve (20%) initially presented with hyperextension instability, and this was usually associated with an avulsion fracture. Thirty four of the patients (57%) had symptoms for less than one month, while 10 (17%) complained of symptoms six months after the injury. Severe complications such as daily pain and stiffness were encountered in three cases. The triad sign (pain on extreme flexion and extension) was of no use as a diagnostic or prognostic factor, nor did the radiographic stress-view help to identify acute instability of the joint.