Hamate metacarpal injury: a case series and suggested algorithm for treatment

Ulnar-sided carpometacarpal fractures and fracture-dislocations are relatively rare but significant injuries due to their impact on hand function. Hamate metacarpal injury represents a trauma to the ulnar corner of the hand. It could lead to fracture of the base of the fourth and fifth metacarpals with associated dislocation. The fourth and fifth carpometacarpal joints have a unique saddle-shaped structure consisting of the metacarpal bases and the distal articular surfaces of the hamate bone. This anatomical design ensures high congruence and significant stability while allowing a variety of movements essential for grip strength and hand dexterity. In this case series, we suggest the term "hamate metacarpal injury" to describe this injury better, as the injury includes dislocation, fracture-dislocation, or impaction to the joint.

We present and discuss six cases representing the various forms of this injury and the surgical approach and outcome. We propose a classification to sort the different injury patterns and help build a surgical plan.

All six cases recovered with good outcomes. All patients gained a full range of motion with a powerful grip.

The hamate metacarpal injury classification introduces a structured, mechanism-based, and treatment-oriented approach to a complex, often overlooked injury pattern. While further validation in larger cohorts is needed, this system has the potential to streamline diagnosis, guide appropriate interventions, and improve patient outcomes in US-CMC injuries.