Boxer fracture (fifth metacarpal neck) !
A boxer fracture is a break of the fifth metacarpal just behind the little-finger knuckle, usually from punching a hard object with a closed fist.
Updated 2026-10-29
Structures involved
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- 5th metacarpal
- 4th metacarpal
- Proximal phalanx, little finger
- Knuckle collateral ligaments
- Extensor tendons
- Finger joint capsules
What it is
A fracture of the neck of the fifth metacarpal, just behind the knuckle of the little finger, typically from punching a hard object with a closed fist. The head usually tilts toward the palm.
Who gets it
One of the most common hand fractures, typically in young men after a punch or fight. It is also seen after falls and direct blows.
Causes
- Punching a wall, a person or another hard object with a clenched fist
- Fall onto a closed hand
- Direct blow to the ulnar side of the hand
Risk factors
- Young male sex
- Interpersonal violence and alcohol use
- Contact and combat sports without proper technique or protection
Pathophysiology
Axial force through the fifth knuckle breaks the thinner neck of the metacarpal. The intrinsic muscles and volar comminution tilt the head toward the palm (apex dorsal angulation). The fifth carpometacarpal joint is mobile, so more angulation is tolerated than in the index or middle fingers, but rotation is never well tolerated because it makes the fingers overlap when the fist closes.
Classification
- By site: head, neck (boxer fracture), shaft or base of the fifth metacarpal
- Closed or open (fight bite)
- By angulation, shortening and rotational deformity; acceptable limits vary between guidelines
Symptoms and signs
- Pain, swelling and bruising over the ulnar side of the hand
- Loss or flattening of the fifth knuckle
- Pain when making a fist
- Little finger overlapping the ring finger when flexed (malrotation)
Diagnosis
- Clinical
- Tenderness over the fifth metacarpal neck and loss of the knuckle contour. Rotation check: when the patient makes a fist, all fingertips should point toward the scaphoid without overlapping. Any skin break over the knuckle is assumed to be a fight bite.
- Tests
- Wound swab or joint fluid culture if a fight bite is infected.
- Imaging
- Hand X-rays in anteroposterior, oblique and lateral views to measure angulation and shortening, and to look for a foreign body such as a tooth fragment.
Differential diagnosis
- Fifth metacarpal shaft or base fracture
- Fourth metacarpal fracture
- MCP joint dislocation or collateral ligament injury
- Hand contusion
- Septic arthritis of the MCP joint from a fight bite
Goal of treatment
Achieve union with no rotational deformity and acceptable angulation, preserve grip and motion, and prevent infection in fight bites.
Treatment
- Acute
- Fight bites need urgent wound exploration, thorough irrigation and often debridement, with tetanus protection; they are not closed primarily.
- Conservative
- Antibiotics that cover human mouth flora (such as a penicillin with a beta-lactamase inhibitor) for fight bites.
- Medical
- Most closed fractures with acceptable angulation and no rotation are managed with closed reduction if needed and an ulnar gutter splint or buddy taping, with early motion.
- Surgical
- Surgery (percutaneous pins, intramedullary fixation or plates) for malrotation, excessive angulation or shortening, open fractures or unstable patterns.
- Rehabilitation
- Hand therapy for stiffness and grip strength.
Complications
- Malrotation with scissoring of the fingers
- Loss of the knuckle prominence (cosmetic, usually little functional effect)
- Septic arthritis or osteomyelitis from a fight bite
- Stiffness and extensor tendon adhesions
- Pseudoclawing with marked angulation
Prognosis
Most heal well with good function; residual loss of the knuckle is common but rarely limiting. Outcome is worse with unrecognised malrotation or infected fight bites.
Prevention
- Avoiding punching hard objects
- Proper technique and protective equipment in combat sports
Test yourself
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Which bone and which part of it are broken in a boxer fracture?
The neck of the fifth metacarpal.
How do clinicians check for rotational deformity in a metacarpal fracture?
They ask the patient to make a fist: all fingertips should point toward the scaphoid without overlapping. Scissoring means malrotation.
Why is a small wound over the knuckle after a punch dangerous?
It may be a fight bite: teeth can carry mouth bacteria into the MCP joint, causing septic arthritis. It needs exploration, irrigation and antibiotics.
Why is more angulation accepted in fifth than in second metacarpal neck fractures?
The fifth carpometacarpal joint is mobile and compensates for angulation; the second and third are rigid.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Fifth Metacarpal Fracture (StatPearls (NCBI Bookshelf), 2024).
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