Fifth Metacarpal Fracture

Excerpt

Overview of Fifth Metacarpal Fractures

Metacarpal fractures account for 40% of all hand fractures. Fifth metacarpal injuries account for 20% of all hand fractures and usually affect the young and active. Certain 5th metacarpal fracture patterns produce functional impairment, evident in declining 5th finger grip strength and 5th metacarpophalangeal (MCP) joint mobility. Manual dexterity consequently diminishes, causing missed workdays and their economic implications.

A boxer’s fracture is a fracture of the 5th metacarpal neck, named for the classic injury mechanism involving direct trauma to a clenched fist. This injury represents 10% of all hand fractures. The treatment varies based on whether the fracture is open or closed and its characteristics, including the degree of angulation, shortening, rotation, and presence of concomitant injuries. Immobilization with an ulnar gutter splint is the definitive treatment for closed, nondisplaced fractures without angulation or rotation. In contrast, open and significantly angulated or malrotated fractures or injuries with neurovascular involvement may require operative fixation.

Metacarpal Anatomy

The metacarpus comprises the palm's skeleton, connecting the wrist bones (carpus) and phalanges. Each digit has a metacarpal bone, with the 1st metacarpal supporting the thumb and the 5th metacarpal assisting the little finger. Each metacarpal has a head, shaft, neck, and base. The heads articulate with the proximal phalanges distally, while the bases articulate with the carpus proximally. The neck is the narrowed portion of the metacarpal bone just distal to the base. This area is commonly involved in boxer's fractures.

The metacarpal bones form the palm's framework and provide attachment points for muscles responsible for hand movements and grip strength. Metacarpals 2 to 5 are closely attached. Consequently, isolated fractures are often stable. The palm's bones are also highly vascularized. Thus, metacarpal fractures heal rapidly except if crushed or severely displaced. Metacarpal injuries can significantly impair hand function, affecting daily living, work, and sports activities if not properly treated.