CARPOMETACARPAL DISLOCATION - AN AID TO DIAGNOSIS

Although the 'true' lateral radiograph of the hand has improved diagno sis of carpometacarpal dislocation, cases can still be missed if only the carpometacarpal joint area is inspected, as overlap of the adjoini ng joints can make interpretation difficult. Measurement of the angle between the long axis of the second and fifth metacarpal bones on a tr ue lateral radiograph, in cases of fifth carpometacarpal dislocation i s advocated, as the carpometacarpal angle is increased compared with c ontrols (38.5-degrees compared with 9.8-degrees). A lesser increase in the carpometacarpal angle is suggestive of subluxation of this joint and this should be examined under anaesthesia.