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
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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Question 1MusculoskeletalMedium
A 21-year-old man presents to the emergency department after punching a wall during an argument. He reports pain and swelling over the back of his right hand. On exam, there is tenderness and swelling at the neck of the fifth metacarpal, loss of the normal knuckle contour with depression of the fifth metacarpal head, and palmar prominence of the head. The overlying skin is intact, and the small finger aligns normally without scissoring on composite flexion. Which of the following is the most likely diagnosis?
ASagittal band rupture at the knuckle
BCarpometacarpal joint dislocation
CFifth metacarpal shaft fracture
DFifth MCP joint dorsal dislocation
EBoxer's fracture of the fifth ray
Reveal answer & full explanation
Correct answer: E — Boxer's fracture of the fifth ray
ASagittal band rupture at the knuckle
BCarpometacarpal joint dislocation
CFifth metacarpal shaft fracture
DFifth MCP joint dorsal dislocation
EBoxer's fracture of the fifth ray✓
Why Boxer's fracture of the fifth ray is correct
A fracture of the fifth metacarpal neck classically follows axial loading from striking a solid object with a clenched fist, typically in a young adult man.
The hallmark findings are tenderness and swelling at the fifth metacarpal neck, loss/depression of the knuckle contour, and apex-dorsal angulation producing palmar prominence of the metacarpal head, exactly the picture here.
Diagnosis is confirmed with PA, lateral, and oblique hand radiographs; rotational alignment is assessed clinically, and no scissoring on composite flexion is reassuring.
Why the others are wrong
Fifth metacarpal shaft fracture — a diaphyseal fracture is tender along the mid-metacarpal with shortening or mid-bone angulation, whereas the tenderness here is at the neck with depression of the knuckle contour and palmar prominence of the metacarpal head.
Sagittal band rupture at the knuckle: extensor tendon subluxation at the MCP joint (boxer's knuckle) with no metacarpal fracture, so there is no knuckle depression or palmar prominence of the metacarpal head.
Carpometacarpal joint dislocation: deformity and pain at the base of the metacarpal from a high-energy mechanism, not the focal neck-level depression seen here.
Fifth MCP joint dorsal dislocation — can also make the metacarpal head prominent in the palm, but it follows forced hyperextension rather than a closed-fist strike, holds the small finger fixed in hyperextension at the MCP joint, and blocks normal composite flexion; here the finger flexes and aligns normally and the tenderness is at the metacarpal neck.
Question 2MusculoskeletalEasy
A 22-year-old man comes to the emergency department after punching a wall during an argument 2 hours ago. He reports pain and swelling over the ulnar side of his right hand. On examination there is tenderness and swelling at the fifth metacarpal neck, loss of the normal knuckle contour with a palmar prominence of the metacarpal head, and no skin lacerations. When asked to flex all fingers, the small finger points toward the scaphoid without overlapping the adjacent fingers. Distal sensation and capillary refill are intact. Which of the following is the most appropriate next diagnostic test?
AComputed tomography of the right hand
BMagnetic resonance imaging of the hand
CMini C-arm fluoroscopy of the hand
DPlain radiography of the right hand
EMusculoskeletal ultrasound of the hand
Reveal answer & full explanation
Correct answer: D — Plain radiography of the right hand
AComputed tomography of the right hand
BMagnetic resonance imaging of the hand
CMini C-arm fluoroscopy of the hand
DPlain radiography of the right hand✓
EMusculoskeletal ultrasound of the hand
Why Plain radiography of the right hand is correct
The clinical picture (axial load from a punch, dorsal knuckle depression with palmar prominence of the fifth metacarpal head) is classic for a boxer's fracture of the fifth metacarpal neck.
Three-view plain films (PA, lateral, and oblique) are the first-line and usually the only imaging needed; the lateral view quantifies apex-dorsal neck angulation, which drives the decision between closed reduction with splinting and operative fixation (the fifth metacarpal tolerates up to roughly 40 degrees, and some sources up to 70 degrees, before surgery is considered).
Rotational alignment is assessed clinically with composite finger flexion, not radiographically, and the exam here already shows no scissoring.
Why the others are wrong
Magnetic resonance imaging of the hand is excellent for occult soft-tissue, ligament, or stress injuries, but it is not the initial study for a suspected acute metacarpal fracture and is far more costly and slower.
Computed tomography of the right hand is reserved for complex intra-articular fractures or operative planning when plain films are inconclusive; it is the wrong sequence before radiographs are obtained.
Musculoskeletal ultrasound of the hand can detect cortical disruption and assess tendon or sagittal-band injury, but it does not reliably quantify metacarpal neck angulation and is not the standard first study for a bony hand injury.
Mini C-arm fluoroscopy of the hand — familiar from hand fracture care, where it is used to guide and confirm closed reduction, but its small-field intraprocedural spot images are not a substitute for the standardized PA, lateral, and oblique radiograph series used to diagnose the fracture and measure neck angulation, so formal plain films come first.
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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 (randomized trials show no functional benefit from reducing an isolated, non-rotated 5th MC neck fracture angulated up to 70 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
No reduction if angulation is within the acceptable threshold and there is no malrotation; if it exceeds the threshold, 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; buddy taping to the ring finger with early motion is an equally effective alternative for a non-rotated fracture that needs no reduction
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 still beyond acceptable thresholds after closed reduction, 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.
van Aaken 2016 — Fifth metacarpal neck fractures treated with soft wrap/buddy taping compared to reduction and casting: results of a prospective, multicenter, randomized trial (van Aaken J et al., Arch Orthop Trauma Surg 2016;136:135-142)
Martínez-Catalán 2020 — A Prospective Randomized Trial Comparing the Functional Results of Buddy Taping Versus Closed Reduction and Cast Immobilization in Patients With Fifth Metacarpal Neck Fractures (Martínez-Catalán N et al., J Hand Surg Am 2020;45:1134-1140)
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