A metacarpal neck fracture of the 5th digit may occur after a direct blow to the MCP joints of the clenched fist. The apex of the fractured metacarpal bone is dorsal. On physical examination, the “knuckle” is flattened and can be palpated on the volar surface. Exam should address neurovascular integrity and rotational deformity. Rotational deformity is evaluated by having the patient flex the digits at the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints; the four digits should point toward the scaphoid. If the involved digit overlaps another digit or does not point toward the scaphoid, a rotational deformity is present and needs to be corrected.
Boxer’s Fracture. Radiograph reveals a nondisplaced fracture through the neck of the metacarpal in the posteroanterior (PA) view. (Photo contributor: Meghan Breed, MD.)
Boxer’s Fracture. This fracture occurred when the patient punched a wall. There is loss of the “knuckle” when the dorsum of the hand is examined, especially noticeable when the patient makes a fist. (Photo contributor: Cathleen M. Vossler, MD.)
Management and Disposition
Up to 40 degrees of angulation on radiography is acceptable for the 4th and 5th metacarpals, whereas angulation of 10 to 20 degrees is acceptable for the 2nd and 3rd metacarpals. Closed reduction for angulation exceeding these limits should be attempted in the ED under appropriate nerve block. Treatment includes ice, elevation, and immobilization in a short-arm gutter splint in the intrinsic plus position (MCP joints are positioned in flexion and the PIP and DIP joints are positioned in extension). For reduction, the MCP joint is held in 90 degrees of flexion and pressure exerted on the metacarpal head, directed dorsally. Simultaneously, the apex of the fracture is directed palmerly. Postreduction radiographs are needed to ensure adequate reduction. Early follow-up (within 7 days) with a hand specialist is essential as the reduction can be lost with simple splinting. Higher degrees of angulation and fractures with any rotational deformity require follow-up for possible open reduction and fixation.
Subtle malrotation can be recognized by looking at the alignment of the nail beds with the digits flexed.
Complications include collateral ligamentous damage, extensor injury damage, and malposition or clawing of the fingers secondary to incomplete reduction.
Boxer’s Fracture: Rotational Deformity. Malpositioning of the right fifth digit. Normally, all digits point toward a single spot on the scaphoid. (Photo contributor: Alexander T. Trott, MD.)