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Updated: Oct 13 2023

Metacarpal Fractures

Images
https://upload.orthobullets.com/topic/6037/images/multiple mc fractures.jpg
https://upload.orthobullets.com/topic/6037/images/metacarpal rotation.jpg
https://upload.orthobullets.com/topic/6037/images/mtthq2.jpg
https://upload.orthobullets.com/topic/6037/images/46_metacarpal-head-screw_11al.jpg
https://upload.orthobullets.com/topic/6037/images/mc shaft fx.jpg
  • summary
    • Metacarpal Fractures are the most common hand injury and are divided into fractures of the head, neck, or shaft.
    • Diagnosis is made by orthogonal radiographs the hand.
    • Treatment is based on which metacarpal is involved, location of the fracture, and the rotation/angulation of the injury.
  • Epidemiology
    • Incidence
      • metacarpal fractures account for 40% of all hand injuries
    • Demographics
      • men aged 10-29 have highest incidence of metacarpal injuries
    • Anatomic location
      • metacarpal neck is most common site of fracture
      • fifth metacarpal is most commonly injured
  • Etiology
    • Mechanism of injury
      • direct blow to hand or rotational injury with axial load
      • high energy injuries (ie. automobile) may result in multiple fractures
    • Associated conditions
      • wounds may indicate open fractures or concomitant soft tissue injury
        • tendon laceration
        • neurovascular injury
      • compartment syndrome
        • closed injuries with multiple fractures or dislocations
        • crush injuries
  • Anatomy
    • Metacarpal anatomy
      • concave on palmar surface
      • 1st, 4th, and 5th digits form mobile borders
      • 2nd and 3rd digits form stiffer central pillar
        • index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others
      • three palmar and four dorsal interossei muscles arise from metacarpal shafts
    • Insertional anatomy
      • extensor carpi radialis longus/brevis
        • insert on the base of metacarpal II, III (respectively); assist with wrist extension and radial flexion of the wrist
      • extensor carpi ulnaris
        • inserts on the base of metacarpal V; extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist
      • abductor pollicis longus
        • inserts on the trapezium and base of metacarpal I; abducts thumb in frontal plane; extends thumb at carpometacarpal joint
      • opponens pollicis
        • inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips
      • opponens digiti minimi
        • inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.
  • Presentation
    • Physical exam
      • inspect for open wounds and associated injuries
        • fight wounds over MCP joint are open until proven otherwise
        • extensor tendon can be lacerated and retracted
        • dorsal wounds over metacarpal fractures are almost always open fractures
      • deformity indicates location
        • deformity at metacarpal base may indicate CMC dislocation
        • shortening can be assessed by comparing contralateral hand
          • may be prevented by transverse intermetacarpal ligaments in isolated fracture of the 3rd or 4th metatcarpal shafts
        • malrotation assessed by lining up fingernail in partial flexion and full flexion if possible, compare to contralateral side
      • motor examination
        • typically no motor deficits unless open wounds present
        • check integrity of flexor/extensor tendons in presence of open wounds
      • neurovascular examination
        • dorsal wounds may affect dorsal sensory branch of radial/ulnar nerve
        • volar wounds can involve digital nerves
  • Imaging
    • Radiographs
      • recommended views
        • PA
        • lateral
        • ER oblique
          • best view to see 4th/5th CMC fracture/dislocation
        • IR oblique
          • best view to see 2nd/3rd CMC fracture/dislocation
      • optional views
        • brewerton
          • best view to see metacarpal head fractures
        • roberts
          • best view to see thumb CMC fracture/dislocation
    • CT
      • indications
        • inconclusive radiographs of CMC fractures/dislocations
        • multiple CMC dislocations
        • complex metacarpal head fractures
  • Diagnosis
    • Radiographic
      • diagnosis confirmed by history, physical exam, and radiographs
  • General Treatment
    • Nonoperative
      • immobilization
        • indications
          • must be stable pattern
          • no rotational deformity
          • acceptable angulation & shortening (see table)
      • Acceptable nonoperative criteria 
      • Acceptable shaft angulation (degrees)
      • Acceptable shaft shortening (mm)
      • Acceptable neck angulation (degrees)
      • Index & Long finger
      • 10-20
      • 2-5
      • 10-15
      • Ring finger
      • 30
      • 2-5
      • 30-40
      • Little finger
      • 40
      • 2-5
    • Operative
      • operative treatment
        • general indications
          • open fx
          • intra-articular fxs
          • rotational malalignment of digit
          • significantly displaced or angulated fractures (see above criteria)
          • multiple metacarpal shaft fractures
          • loss of inherent stability from border digit during healing process
        • postoperative
          • early motion is critical
          • remove pins/ cast at ~ 4 weeks
  • Treatment - Metacarpal Head Fractures
    • Operative
      • ORIF
        • indications
          • no degree of articular displacement acceptable
          • majority requires surgical fixation
      • external fixation
        • indications
          • severely comminuted fractures
      • MCP arthroplasty
        • indications
          • severely comminuted fractures
      • MCP fusion
        • indications
          • arthritis late disease
    • Techniques
      • ORIF
        • approach
          • dorsal incision
          • either centrally split extensor apparatus or release and repair sagittal band
        • fixation
          • hardware cannot protrude from joint surface
          • fix with multiple small screws in collateral recess, headless screws, or k-wires
          • ideal fixation should allow for early motion
    • Complications
      • stiffness
        • most common
        • prevented with early motion
  • Treatment - Metacarpal Shaft Fractures
    • Nonoperative
      • immobilization
        • indications
          • nondisplaced metacarpal neck fractures
          • acceptable angulation (see above table)
          • no malrotation
        • immobilize MCP joints in 70-90 degrees of flexion
        • cast for 4 weeks
    • Operative
      • ORIF vs. CRPP
        • indications
          • open fractures
          • unacceptable angulation (see above table)
          • any malrotation
          • multiple fractures
    • Techniques
      • closed reduction percutaneous pinning
        • place antegrade through metacarpal base or retrograde through collateral recess
          • remove pins at 4 weeks
      • open reductions with lag screw
        • can use multiple lag screws for long spiral fractures
          • try to get at least two lag screws
      • open reduction with dorsal plating
        • works best for transverse fractures
        • try to cover plate with periosteum to prevent tendon irritation
        • begin early motion to prevent tendon irritations
      • intramedullary headless compression screw
        • indicated only for axially stable fractures
  • Treatment - Metacarpal Neck Fractures
    • Nonoperative
      • reduction and casting
        • acceptable degrees of apex dorsal angulation (varies by study, see above table)
        • immobilize MCP joints in 70-90 degrees of flexion, leave PIP joints free
        • cast for 4 weeks
        • reduce using Jahss technique
          • 90 degrees MCP flexion, dorsal pressure through proximal phalanx while stabilizing metacarpal shaft
    • Operative
      • reduction and fixation
        • indications
          • unacceptable angulation (see above table)
          • open fractures
          • any malrotation
          • intraarticular fractures
    • Technique
      • CRPP with MCP's flexed
        • antegrade through metacarpal base
        • retrograde through collateral recess
      • ORIF
        • perform if cannot get reduction for CRPP
        • difficult to plate because limited bone for distal fixation
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