Fracture of the neck of the fifth metacarpal from striking with a closed fist.
Also known as: boxer's fracture, fifth metacarpal neck fracture, brawler's fracture, MCP fracture
Overview
Fracture of the neck of the fifth metacarpal, classically resulting from axial loading of the metacarpal head while striking a solid object with a clenched fist. Despite the name, the injury is more typical of untrained brawlers than trained boxers, who are taught to land force across the second and third metacarpals.
Epidemiology
Most common metacarpal fracture and one of the most common hand fractures in young adult men. Bimodal age distribution centered in late adolescence and early adulthood.
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Underlying mental health or anger management concerns
Pathophysiology
Axial force transmitted from the metacarpal head into the metacarpal neck exceeds the cortical bone strength at the metaphysis, producing apex-dorsal angulation. The intrinsic muscles of the hand and the pull of the flexor and extensor tendons drive the distal fragment volarly.
Clinical presentation
Symptoms
Pain and swelling over the dorsal aspect of the fifth metacarpal
Loss of the normal knuckle contour with depression of the fifth metacarpal head
Difficulty making a fist or gripping
Signs / physical exam
Tenderness and swelling at the fifth metacarpal neck
Apex-dorsal angulation with palmar prominence of the metacarpal head
Rotational malalignment — best assessed by asking the patient to flex all fingers; the small finger should point toward the scaphoid, with no overlap (scissoring) with adjacent fingers
Inspect skin carefully for lacerations suggesting fight bite
Classic findings
Dorsal knuckle depression with palmar prominence of the metacarpal head and pain after a punch.
Differential diagnosis
Bennett fracture — Intra-articular fracture-dislocation at the base of the thumb metacarpal
Rolando fracture — Comminuted intra-articular fracture at the base of the thumb metacarpal
Fight bite (human bite) — Lacerations over the dorsal MCP from striking a tooth — high risk of septic arthritis; surgical irrigation often required
Sagittal band rupture (boxer's knuckle) — Extensor tendon subluxation at MCP joint without metacarpal fracture
Carpometacarpal dislocation — Pain at the base of the metacarpal with deformity; high-energy mechanism
Diagnostic workup
Diagnostic criteria
Acceptable angulation thresholds for closed treatment (greater tolerance distally due to CMC joint mobility): 2nd MC ≤10 degrees, 3rd MC ≤20 degrees, 4th MC ≤30 degrees, 5th MC ≤40 degrees (some sources accept up to 70 degrees for isolated 5th MC neck with no rotation, but functional outcomes are best when angulation is reduced to <30 degrees). Any rotational deformity, intra-articular extension, or open fracture is an indication for operative care.
Labs
None required for isolated injury; CBC and broad-spectrum antibiotics for fight bite
Imaging
PA, lateral, and oblique hand radiographs
Measure metacarpal neck angulation on lateral view (apex dorsal)
Assess for rotational deformity clinically rather than radiographically
Diagnostic algorithm
Metacarpal
Acceptable Dorsal Angulation
Reason
2nd
≤10 degrees
Minimal CMC mobility
3rd
≤20 degrees
Limited CMC mobility
4th
≤30 degrees
Moderate CMC mobility
5th
≤40 degrees (functional)
Greatest CMC mobility compensates for angulation
Acceptable dorsal angulation thresholds for closed management of metacarpal neck fractures.
Treatment
First-line
Closed reduction (Jahss maneuver — flex MCP and PIP to 90 degrees and apply dorsally directed pressure to the proximal phalanx while supporting the metacarpal shaft) under hematoma block or finger block
Immobilization in ulnar gutter splint with MCP joints flexed 70-90 degrees, IP joints extended (intrinsic-plus position) for 3-4 weeks
Hand therapy and gradual return to activity
NSAIDs and ice for pain control
Second-line / adjunct
Operative fixation (closed reduction with percutaneous pinning, intramedullary nail, or open reduction and internal fixation) for: rotational malalignment, angulation exceeding acceptable thresholds, intra-articular fracture, open fracture, or multiple metacarpal fractures
Fight bite — surgical irrigation and debridement of the MCP joint, IV antibiotics covering oral flora (ampicillin-sulbactam) and tetanus prophylaxis; never close the wound primarily
Complications
Rotational malunion with finger scissoring
Loss of MCP extension (extensor lag)
Pseudoclaw deformity from volar angulation altering intrinsic balance
Stiffness of MCP and PIP joints
Septic arthritis or osteomyelitis from missed fight bite
Loss of grip strength
PANCE pearls
Always inspect for fight bite — even a small dorsal MCP laceration after striking another person is treated as a contaminated joint injury until proven otherwise.
Rotational alignment is the most important parameter — overlap (scissoring) of fingers during composite flexion is unacceptable.
The fifth metacarpal tolerates more angulation than the second or third because of greater carpometacarpal joint mobility.
Intrinsic-plus splinting (MCP flexion 70-90 degrees, IP extension) prevents collateral ligament shortening and joint contracture.
References
AAOS — American Academy of Orthopaedic Surgeons clinical guidance on metacarpal fractures
ASSH — American Society for Surgery of the Hand evidence-based guidance on hand fractures
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