Fractures of the fourth metacarpal

To determine (a) the degree of shortening associated with isolated fourth metacarpal fractures and the functional outcome after operative or nonoperative (protocol of casting and outrigger) treatment (clinical portion), and (b) the role of the deep metacarpal ligament in minimizing shortening after isolated fourth metacarpal osteotomies simulating clinical fracture (cadaveric portion).

This two-part study included a retrospective clinical portion and a cadaveric investigation.

First, the records of twenty-four patients with isolated displaced oblique or spiral fourth metacarpal fractures without adjacent metacarpal fractures were retrospectively reviewed. The amounts of shortening after nonoperative (seventeen patients) and operative (seven patients) intervention were compared. Second, seven hands were studied to compare the length of intact fourth metacarpals to that after oblique osteotomies and after deep metacarpal ligament sectioning. The differences in shortening measurements were statistically analyzed using a paired t test.

There was no significant difference in mean initial shortening (+/-SD) between operative and nonoperative patients (2.65 +/- 1.85 mm vs. 4.19 +/- 1.83 mm, respectively; p < 0.09; overall average shortening, 3.1 mm) or functional outcome. The cadaveric study documented the important role of the deep metacarpal ligament in minimizing fourth metacarpal shortening. Fourth metacarpals osteotomized with an intact deep metatarsal ligament had significantly less mean shortening (+/-SD) than those with a sectioned deep metacarpal ligament: 2.1 versus 5.8 mm, respectively (p < 0.001).

In the absence of unreducible rotational malalignment, fourth metacarpal fractures may be adequately treated nonoperatively with a protocol of casting and outrigger.