The CMC joints are arthrodial diarthoses (gliding joints) except the fifth, which is a modified saddle joint. Almost no movement is possible at the 2nd and 3rd metacarpals, and 15-20 degrees of flexion is possible at the 4th and 5th.
The deep (motor) branch of the ulnar nerve lies immediately volar to the fifth CMC joint as it winds around the hook of the hamate. The deep palmar arterial arch lies directly beneath the 3rd CMC articulation.
Most of these are dorsal dislocations or fracture dislocations. Radiographic visualization is difficult.
Look for CMC dislocations when you see metacarpal fractures!

Treatment – Acute
Closed reduction and K-wiring; seems to give superior results than ORIF, but ORIF would be necessary in open injuries. When wiring, the emphasis is on restoration of the metacarpal shaft alignment and length – K-wiring can be from the metacarpal to adjacent metacarpal, or into the carpal bone itself.

Treatment – Chronic
If beyond 3 weeks and the incongruity of the joint is mild (whatever that means) they recommend doing nothing.
For symptomatic arthritis, arthrodesis or interposition arthroplasty.

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