A 22-year-old man is brought to the emergency department by his friends following a physical altercation at a local bar. He reports intense pain and swelling over the dorsum of his right hand. He states that the injury occurred when he punched a wall in frustration. On physical examination, there is significant edema and ecchymosis over the ulnar aspect of the hand. There is a visible loss of the normal knuckle prominence at the fifth metacarpophalangeal joint. When the patient is asked to make a fist, the fifth digit exhibits slight malrotation, overlapping the fourth digit. Neurovascular status is intact distally. Radiography of the hand reveals a transverse fracture through the neck of the fifth metacarpal with 40° of volar angulation.
Which of the following is the most likely diagnosis?
The correct answer is:
B) Boxer’s fracture
The patient has sustained a Boxer's fracture, which is a transverse fracture of the fifth metacarpal neck. This injury classically occurs when a person strikes a hard object with a closed, unprotected fist. The force of the impact is transmitted through the metacarpal, causing the head of the bone to tilt toward the palm (volar angulation). This results in the "loss of knuckle" appearance seen on physical exam. A critical part of the evaluation for this fracture is checking for rotational deformity. If the fingers overlap when making a fist (scissoring), it indicates the need for formal reduction or surgical intervention.
Answer choice A: Bennett fracture, is incorrect. This is an intra-articular fracture at the base of the thumb. It typically involves a small fragment of bone that remains attached to the volar oblique ligament while the rest of the thumb metacarpal is displaced proximally and radially by the abductor pollicis longus.
Answer choice C: Colles fracture, is incorrect. This is a common fracture of the distal radius with dorsal displacement, often occurring after a fall on an outstretched hand (FOOSH). It creates a "dinner fork deformity" of the wrist rather than an injury to the metacarpals.
Answer choice D: Rolando fracture, is incorrect. Like the Bennett fracture, this occurs at the base of the first metacarpal, but it is a comminuted (Y-shaped or T-shaped) intra-articular fracture. It has a much worse prognosis than a Bennett or Boxer's fracture and almost always requires surgery.
Answer choice E: Scaphoid fracture, is incorrect. This is the most common carpal bone fracture, typically presenting with tenderness in the anatomical snuffbox following a FOOSH injury. It does not typically occur after punching a wall and does not involve the metacarpal neck.
Key Learning Point
A Boxer’s fracture is a fracture of the fifth metacarpal neck caused by a direct blow with a clenched fist. Physical exam findings include loss of the fifth knuckle prominence and potential rotational malalignment (fingers scissoring). Management involves ulnar gutter splinting for stable fractures, but significant angulation (usually >40°) or any rotational deformity requires reduction or surgical fixation.
