Metacarpal Fractures

Patients present after acute hand trauma with pain, swelling, and reduced grip. The mechanism stratifies the pattern: a closed-fist punch points to a boxer's fracture or fight bite; a fall on the thumb to a Bennett or Rolando; a crush or rotational injury to a shaft fracture. Document hand dominance, occupation, sport, and time since injury.

Examination:

• •Inspect for deformity (dorsal angulation in boxer's, loss of knuckle prominence), rotation, and skin integrity. Visible bone or laceration over a knuckle = open injury / fight bite until proven otherwise
• •Rotational assessment is mandatory: ask the patient to make a fist; each fingertip should point toward the scaphoid tubercle. Scissoring or overlap = malrotation = surgical referral
• •Palpate the metacarpal length and tenderness sites; assess CMC joint stability for thumb base injuries
• •Neurovascular check: ulnar nerve in 4th-5th MC injuries, median in carpal tunnel-pressure presentations, perfusion at each fingertip
• •In the closed-fist injury: ASK about the mechanism specifically. Patients often hide an altercation. Examine the FULLY clenched fist - the injury moves proximally when the fingers extend, hiding the joint puncture

A visible knuckle wound, even small, after a punch is a fight bite injuring the MCP joint capsule and metacarpal head. Treat as an open MCP joint injury (UK BOAST open fracture pathway plus NICE NG184 bite guidance).

Plain radiographs (PA, lateral, oblique of the affected hand) are first-line and define the fracture pattern. Dedicated views for the thumb (true AP and lateral) are essential for Bennett and Rolando fractures - the lateral demonstrates the volar ulnar fragment and dislocation of the rest of the metacarpal.

Key radiographic measurements:

• •Boxer's fracture (5th MC neck): angulation in degrees on lateral. Tolerated angulation increases from index (10-15 degrees) to little finger (40 degrees) because the ulnar two CMC joints have more flexibility to compensate
• •Shaft fractures: shortening (mm), angulation (degrees, dorsal/volar), and rotation (assess clinically; not radiographic)
• •Articular step-off: any over 1-2 mm at the thumb base or MCP head joint surface
• •Look for second sites of injury: associated phalangeal or carpal fractures, especially in high-energy mechanisms

CT is indicated for surgical planning of comminuted intra-articular fractures (Rolando, comminuted Bennett, multi-fragmentary MCP head) - it quantifies articular involvement and fragment morphology beyond plain film resolution.

MRI is rarely indicated acutely; reserved for suspected ligamentous injury, occult fractures, or chronic missed presentations.

In fight bite: plain X-ray to exclude foreign body (tooth fragment) and assess for fracture, alongside the soft-tissue assessment. Routine bloods (FBC, CRP) for fight bite or any open / suspected septic injury.

Management is driven by location, angulation, rotation, and articular involvement (NICE NG38, BSSH, BOAST).

Boxer's fracture (5th MC neck):

• •Angulation under threshold (under 40 degrees for 5th, less for radial digits) and NO rotational deformity: conservative. Buddy strapping or ulnar gutter cast for 2-3 weeks, then mobilise. The MUST trial (Lancet 2024) showed buddy strapping non-inferior to formal casting for non-rotated boxer's fractures - reduces UK fracture clinic burden
• •Over threshold angulation or any rotational deformity: closed reduction (Jahss manoeuvre - flex MCP and PIP to 90 degrees, apply axial pressure on the proximal phalanx) then immobilisation; or surgical fixation if reduction unstable
• •Open reduction and K-wire / plate fixation for irreducible or unstable patterns

Metacarpal shaft fractures:

• •Stable, undisplaced, no rotation: buddy strapping or splint for 3-4 weeks; early mobilisation
• •Shortening over 5 mm, angulation over 10 degrees in index/long or over 20-30 degrees in ring/little, or any rotational deformity: operative fixation (K-wires, lag screws, or plates)
• •Spiral fractures need particular vigilance for rotation - low threshold for fixation

Bennett and Rolando (thumb base):

• •Bennett: closed reduction and percutaneous K-wire fixation if reducible (the standard UK approach); ORIF with screws if irreducible or articular step persists
• •Rolando: usually requires ORIF or external fixation due to comminution; outcomes worse than Bennett with higher rates of post-traumatic arthritis
• •Both: cast immobilisation 4-6 weeks post-fixation

Reverse Bennett (5th MC base): K-wire fixation if displaced, given proximal traction from ECU.

Intra-articular metacarpal head fractures: ORIF for over 1-2 mm articular step or significant displacement; mini-fragment fixation typically.

Fight bite (closed-fist injury):

• •ED referral - this is an open MCP joint injury
• •IV co-amoxiclav (or clindamycin + ciprofloxacin in penicillin allergy) per NICE NG184
• •Tetanus prophylaxis as required
• •Theatre for joint washout and debridement; never close the wound primarily
• •Plain X-ray for foreign body and underlying fracture
• •Consider plastic surgery / hand surgery on call same day

Referral pathway: any open fracture, fight bite, displaced thumb base injury, rotational deformity, angulation beyond threshold, or articular step over 1-2 mm to hand surgery / fracture clinic same day or next day. Most boxer's fractures without rotation managed in primary care / minor injuries with buddy strapping.

Conservative pathway (boxer's fracture without rotation, shaft fractures stable / undisplaced):

• •Weeks 0-1: ice, elevation, buddy strapping or ulnar gutter splint; finger ROM encouraged from day 1 unless splinted
• •Weeks 1-3: progressive active and active-assisted ROM; buddy strapping continues for 3-4 weeks
• •Weeks 3-6: progressive grip strengthening; hand therapy referral if stiffness persists
• •Weeks 6-12: full return to ADLs, manual work, and sport. Most patients return to office work by week 1, manual work by week 3-6, contact sport by week 6-12

Post-operative (K-wire fixation):

• •Week 0-4: cast or removable splint with K-wires in situ; finger ROM in adjacent uninvolved digits
• •Week 4: K-wire removal; commence active ROM; hand therapy supervision begins
• •Weeks 4-8: progressive ROM and strengthening
• •Weeks 8-12: return to work and sport; full ROM and grip strength targets at 12 weeks

Post-operative (plate and screw fixation): generally earlier mobilisation with removable splint from week 1-2; progressive strengthening from week 4-6.

Post-fight-bite (closed-fist injury): immobilisation 1-2 weeks post-washout, then early ROM under hand therapy. Antibiotic course completion; close follow-up for joint infection and stiffness.

Thumb base injuries (Bennett, Rolando): cast immobilisation 4-6 weeks, progressive thumb ROM and pinch strengthening from week 6; full return at 12-16 weeks.

Persistent stiffness beyond 12 weeks, rotational deformity, or impaired pinch / grip warrants hand-therapy reassessment and possible secondary surgical opinion. Counsel patients on the high prevalence of post-traumatic stiffness without early mobilisation.

• •NICE NG38 Fractures (non-complex, 2016) - UK foundation framework: indications for manipulation, fixation, and conservative management; analgesia and follow-up principles for hand fractures.
• •MUST trial (Lancet 2024) - Buddy strapping non-inferior to formal casting for non-rotated boxer's fractures at 3 months; supports current UK practice of streamlined management for the commonest pattern.
• •BOAST Open Fractures - UK trauma standard: early IV antibiotics, limited wound handling, no primary closure, urgent senior orthopaedic input. Applies to open metacarpal fractures and fight bites.
• •NICE NG184 Bites (human and animal, antimicrobial prescribing) - First-line co-amoxiclav for human bites; clindamycin + ciprofloxacin in penicillin allergy. Fight bites are classified as human bites for antibiotic purposes.
• •Bennett (1882) / Rolando (1910) classifications - Persistent UK and international reference: Bennett 2-fragment partial articular fracture-dislocation vs Rolando comminuted T or Y intra-articular fracture. Drives operative-vs-non-operative decisions for thumb base injuries.

• •Rotational deformity is the absolute surgical indication regardless of angulation. Check the finger cascade: each flexed finger should point toward the scaphoid tubercle. Scissoring or overlap = malrotation = refer.
• •Angulation thresholds increase ulnarward: ~10 degrees (index), ~20 (long), ~30 (ring), ~40 (little) for metacarpal neck fractures. The ulnar two CMC joints compensate more than the rigid radial two.
• •Bennett vs Rolando: Bennett is a 2-fragment partial articular fracture-DISLOCATION (volar ulnar fragment held by anterior oblique ligament; rest of metacarpal pulled proximal-dorsal-radial by APL). Rolando is a comminuted intra-articular T/Y pattern with worse prognosis.
• •Fight bite (closed-fist injury) is a UK ED emergency: open MCP joint, IV co-amoxiclav, tetanus, theatre washout, never close primarily. The history is often hidden - ask specifically about altercations.
• •MUST trial (2024): buddy strapping is non-inferior to casting for non-rotated boxer's fractures. Modern UK practice favours the simpler intervention with early mobilisation.
• •Spiral shaft fractures ROTATE; transverse shaft fractures SHORTEN. Both can require fixation - rotation is the harder problem to detect on imaging and demands clinical assessment.