Hand: Carpometacarpal dislocations

A carpometacarpal joint connect a finger to the hand.

The usual carpometacarpal dislocation involves the small finger CMC joint. Although a well molded cast can be effective, the treatment usually requires "pinning" of the dislocated joint for approximately 4 weeks.

Dislocations of the other carpometacarpal joints are less common, but the treatment principle is the same: each joint has to be reduced and held in place - with as many pins as needed.

Case study

The injury described below was from an industrial accident.

Here's a PA view. Notice that:

  1. The hamate small finger CMC is not subluxed.
  2. Notice the small fracture next to the ring finger metacarpal. The hamate-ring metacarpal joint is not far from its proper position.
  3. The capitate long finger CMC joint is dislocated.
  4. Index finger metacarpal is fractured, dislocated, and trapezoid is not in its proper place relative to the rest of the carpus.
  5. Trapezium, hamate, and radial styloid are all fractured, but those are the least of the problems.

The trapezoid is easier to see in this oblique view: it is dislocated from the rest of the carpus.

A 3D reconstruction view is not particularly helpful.

One way to think of this injury is as the hand equivalent of a Lisfranc injury of the foot.

The injury was approached through a large dorsal midline incision. A large amount of hematoma was removed, and then reduction was performed starting from the ulnar side and proceeding towards the thumb. Stabilization was performed with percutaneous pins. Here it is:

Patient was kept in a splint with pins for 2 weeks. Physical therapy was started at 2 weeks in order to prevent stiffness. Patient followed up weekly to check and care for the percutaneous pins, and to make sure physical therapy progressed correctly. Pins were removed at 4 weeks.

The patient eventually made a full recovery and was able to resume work at the same job. Here are the final xrays several months later: