Boxer's Fracture (Fifth Metacarpal Neck)
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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Risk factors
- Punching a wall, door, or another person
- Contact sports (mixed martial arts, boxing, hockey)
- Alcohol intoxication
- 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 |
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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