Metacarpal fractures

Metacarpal fractures are caused by direct or indirect trauma to metacarpal bones and account for approximately 30% of all hand fractures. Metacarpal fractures may occur at the metacarpal head, neck, base, or shaft. Because fracture of the 4^th or 5^th metacarpal neck most commonly occurs when a clenched fist comes in contact with a solid object, this type of metacarpal fracture is also known as a boxer's fracture. Clinical features include general fracture signs (e.g., pain, swelling, tenderness, reduced range of motion), incomplete grip, and, in some cases, deformity. An x-ray of the hand usually confirms a metacarpal fracture and may be used to identify associated joint dislocation. Treatment is predominantly conservative and involves reduction and immobilization. Surgical treatment is required for severe cases (e.g., open fractures, intraarticular fractures, malalignment). Complications include permanent deformity, osteoarthritis, and reduced grip strength.

• Account for approx. 30% of all hand fractures
• Most commonly involve the 5^th metacarpal

Reference:^[1]

Epidemiological data refers to the US, unless otherwise specified.

• Direct or indirect trauma to the metacarpal bones; (e.g., a fall, striking a firm object with a clenched fist, forced hyperextension or rotation of the joints)
• Fatigue fractures in rare cases (e.g., stress injuries in athletes, occupational injuries due to repetitive strain)
• Common mechanisms of injury
  • Direct trauma → transverse fracture
  • Torsional trauma → oblique or spiral fracture
  • Crush injury → comminuted fracture

• Anatomical location
  • Fractures of the metacarpal head, neck, base, and shaft
  • A fracture of the 4^th or 5^th metacarpal neck is called a boxer's fracture because it is usually caused by a closed fist forcibly coming into contact with a solid surface.
• Type of fracture: transverse, oblique, spiral, comminuted (see “Fracture classification” in “General principles of fractures”)
• First metacarpal fractures
  • Intraarticular
    • Type I metacarpal base fracture (Bennett fracture-dislocation)
      • Two-part fracture of the metacarpal base
      • The 1^st metacarpal shaft fragment is radially and proximally dislocated by the pull of the abductor pollicis longus muscle.
    • Type II metacarpal base fracture (Rolando fracture)
      • Comminuted fracture of the metacarpal base
      • The fragments often form a T- or Y-shaped pattern.
  • Extraarticular
    • Type III metacarpal base fracture: transverse or oblique fracture of the metacarpal base
    • Type IV metacarpal base fracture: a pediatric physeal fracture, most commonly a type II Salter-Harris fracture (see “Pediatric fractures”)

• See “Fracture signs” in “General principles of fractures.”
• Pain, swelling, and tenderness at the site of the affected metacarpal
• Reduced range of motion at the carpometacarpal (CMC) and metacarpophalangeal joints
• Palpable or visible bone and/or joint deformity
  • Angulation (mostly dorsal angulation → loss of the knuckle contour and/or pseudoclaw deformity)
  • Malrotation → digital overlap
  • Shortening
  • Displacement
• Concomitant injuries
  • Tissue/skin injuries (e.g., laceration, protrusion of bone fragments)
  • Neurovascular lesions
  • Fractures of the scaphoid and/or distal radius/ulna

The management of the affected bone/joint is determined by the type and severity of the deformities that are present (e.g., displacement, malrotation, shortening).

• X-ray ^[1]
  • Definitive diagnosis typically requires three radiographic views: anteroposterior, lateral, and oblique
  • Additional radiographic views for specific injuries
    • 1^st metacarpal fractures
      • Visualization of the 1^st CMC joint: true anteroposterior view (Robert view) in full pronation
      • Bennett fracture-dislocation: true lateral view (Bett view)
    • 2^nd–5^th metacarpal base fractures
      • Visualization of the 2^nd–3^rd CMC joints: semipronated oblique view
      • Visualization of the 4^th–5^th CMC joints: semisupinated oblique view
• CT: only indicated for severe fractures, CMC joint dislocation, and intraarticular fractures with bone fragmentation
• Musculoskeletal ultrasound: may be performed in linear areas of bone (e.g., diaphysis/metaphysis of the metacarpals)

• General
  • See “General fracture care” in “General principles of fractures.”
  • Ensure concomitant injuries and/or infections are also treated.
• Conservative treatment ^[1]
  • Indication
    • Simple, closed, and stable metacarpal fractures
    • Mild deformity is often preferable to surgical treatment.
  • Treatment options
    • Closed reduction, if necessary
    • Immobilization for approx. 4 weeks, depending on physical examination findings
      • 1^st metacarpal fractures: short-arm thumb spica splint
      • 2^nd–4^th metacarpal fractures: palmar wrist splint/cast
      • 5^th metacarpal fractures : ulnar gutter splint/cast or twin taping to the ring finger
• Surgical treatment ^[2]
  • Indication
    • Open fractures
    • Intraarticular fractures occupying > 25% of the articular surface ^[1]
    • Displaced fractures with a step-off of > 1 mm or subluxation/dislocation of the CMC joint
    • Deformities leading to functional impairment: severe angulation , shortening , or malrotation ^[3]
  • Treatment options: fracture fixation with K-wires, interfragmentary screws, or mini plates

The majority of metacarpal fractures can be treated conservatively.

• Permanent deformity (e.g., malrotation, misalignment, bone reduction)
• Reduced grip strength
• Joint stiffness
• Recurrent joint dislocation
• Osteoarthritis

We list the most important complications. The selection is not exhaustive.