Isolated posttraumatic osteoarthritis of the third carpometacarpal joint: a report of two cases

An alternative injury pattern suggests that carpometacarpal joint (CMCJ) injury may begin at the stable third CMCJ, not just the fifth CMCJ. We present two cases of isolated posttraumatic osteoarthritis in the third CMCJ, supporting this potential origin.

Two men with isolated third CMCJ posttraumatic osteoarthritis presented with dorsal hand swelling and pain, and decreased grip strength. Both visited our clinic more than six months from original injury. After radiographs and CT scan, isolated third CMCJ posttraumatic osteoarthritis was identified. 

Capitometacarpal arthrodesis was performed with satisfactory functional outcome. Flatt in 1959 describes the third CMCJ as the central pillar of the hand; therefore, the dislocation of this capitometacarpal joint is considered the essential injury capable of causing neighboring CMCJs to dislocate due to its strong intermetacarpal ligaments. However, if the force of the injury is insufficient to affect neighboring CMCJs, it can lead to lesions primarily affecting the third CMCJ, ultimately resulting in the development of isolated posttraumatic osteoarthritis in the third CMCJ.

The possibility of isolated third CMCJ posttraumatic osteoarthritis suggests a potential link to a CMCJ fracture dislocation mechanism originating from the third CMCJ, which should be differentiated from the similar clinical appearance of a carpal boss.

Keywords: Arthrodesis, capitometacarpal joint, osteoarthritis, third carpometacarpal joint, wrist fracture dislocation.