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Updated: Jul 28 2023

Base of Thumb Fractures

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  • summary
    • Base of Thumb metacarpal fractures can be extra-articular fractures, Bennett fractures (partial intra-articular), or Rolando fractures (complete intra-articular).
    • Diagnosis can be made by orthogonal radiographs of the thumb.
    • Treatment ranges from splint immobilization for certain extra-articular fractures to surgical fixation for displaced Bennett or Rolando fractures.
  • Epidemiology
    • Incidence
      • 80% of thumb fractures involve the metacarpal base
      • the most common pattern is extraarticular epibasal fracture
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • most Bennett and Rolando are fractures caused by axial force applied to the thumb in flexion
      • pathoanatomy
        • imperfect reductions and above forces lead to increased joint contact pressures and subsequent predisposition to early arthritis
        • excessive angulation may lead to MCP joint hyperextension deformity
  • Anatomy
    • Osteology
      • CMC joint is a saddle-shaped joint composed of the trapezium and the base of the thumb (1st) metacarpal
        • flexion-extension motion
        • abduction-adduction motion
    • Muscles
      • three muscles provide deforming forces at the base of the thumb
        • abductor pollicis longus (PIN)
          • proximal, dorsal, and radial force on the shaft fragment
        • extensor pollicis longus (PIN)
          • proximal, dorsal, and radial force on the shaft fragment
        • adductor pollicis (Ulnar n.)
          • supination and adduction force on the shaft fragment
    • Ligament
      • volar beak ligament
        • spans the tuberosity of the trapezium to the volar edge of the 1st metacarpal
        • keeps trapezium connected to the volar-ulnar base fragment
      • dorsoradial ligament
        • spans the dorsoradial tubercle of the trapezium to the dorsal base of the 1st metacarpal
    • Biomechanics
      • very limited axial rotation
      • average flexion-extension of 53 degrees
      • average abduction-adduction of 42 degrees
  • Classification
      • Classification of fractures of the first metacarpal
      • Extra-articular oblique
      • Oblique fracture line not involving the articular surface
      • Extra-articular transverse
      • Pure transverse fracture line not involving the articular surface
      • Intra-articular Bennett
      • Intra-articular fracture with a palmar ulnar fragment
      • Intra-articular Rolando
      • Y or T shaped complete intra-articular fracture
      • Intra-articular comminuted
      • Severely comminuted complete intra-articular fracture
  • Presentation
    • Symptoms
      • acute pain at the base of thumb with
    • Physical exam
      • inspection
        • swelling and ecchymosis
        • tenderness to palpation at CMC joint
      • motion
        • pain with range of motion
  • Imaging
    • Radiographs
      • recommended views
        • true AP of thumb (Robert's View)
          • arm in full pronation with dorsum of thumb on cassette
        • true lateral of thumb
          • hand pronated 30 degrees and beam angled 15 degrees distally
        • oblique
      • optional imaging
        • traction view may be obtained to better understand the fracture pattern in Rolando and severely comminuted fractures
      • findings
        • bennett fractures
          • a small fragment of 1st metacarpal base articulating with trapezium
        • rolando fractures
          • Y sign
            • represents a splitting of the 1st metacarpal base into volar and dorsal fragments
      • criteria dictating treatment
        • extra-articular fracture
          • <30 degrees angulation
        • Bennett's fracture
          • <1mm articular step-off
        • Rolando
          • comminution dictates operative strategy
      • sensitivity and specificity
        • a 30-degree pronated view provides the best view
    • CT
      • indications
        • complex fracture patterns for assessment of fracture fragment detail
  • Diagnosis
    • Radiographic
      • diagnosis confirmed by history, physical exam, and radiographs
  • Treatment
    • Nonoperative
      • closed reduction and thumb spica casting
        • indications
          • extra-articular fractures with <30 degrees of angulation following closed reduction
          • Bennett fractures with <1mm displacement
        • modalities
          • a reduction is achieved with longitudinal traction, palmar abduction, and pronation
      • thumb spica casting
        • indications
          • fractures greater than 3 weeks old that will no motion at fracture site should be treated allowance of step-off and casting
    • Operative
      • closed reduction and percutaneous k-wire fixation
        • indications
          • extra-articular fractures with >30 degrees of angulation following closed reduction
          • inability to maintain reduction <30 degrees with thumb spica
          • Rolando fracture <1mm displacement
          • small fracture fragments that are not amenable to screw fixation
      • open reduction internal fixation
        • indications
          • >1mm of displacement in Bennett, Rolando, and severely comminuted fractures with large fracture fragments amenable to fixation
      • distraction and external fixation
        • indications
          • Rolando fracture with >1mm displacement and major soft tissue injury
          • severely comminuted fractures with major soft tissue injury or impacted articular fragments
          • Bennett, Rolando, or severely comminuted fractures with fragments too small for ORIF
  • Techniques
    • Closed reduction and percutaneous k-wire fixation
      • instrumentation
        • a transverse extra-articular fracture can be treated with transarticular k-wire fixation
        • oblique extra-articular fractures can be treated with intermetacarpal k-wire fixation
      • complication specific to this treatment
        • loss of reduction
    • Open reduction internal fixation
      • approach
        • volar approach of Gedda and Moberg
      • soft tissue
        • thenar muscles are reflected volarly and a longitudinal capsulotomy is made
      • bone work
        • fracture is clamped in a volar-dorsal plane
      • instrumentation
        • fracture provisionally reduced with k-wire and fixed with screws or T-plate depending on fracture pattern
      • complication specific to this treatment
        • injury to the superficial branch of the radial nerve
        • wound healing complications if significant edema is present
      • outcomes
        • adequacy of anatomic reduction predicts development of radiographic arthritis but does not predict symptomatic arthritis
    • Distraction and external fixation
      • instrumentation
        • two 3mm are placed in the dorsoradial aspect of the distal shaft of the metacarpal
        • two 3mm are placed in the dorsoradial aspect of the radius
        • pins may be placed into the second metacarpal shaft to control deforming forces
      • complications specific to this treatment
        • pin site infection
  • Complications
    • Posttraumatic arthirtis
      • incidence
        • the exact incidence is unclear
      • risk factors
        • highly comminuted intra-articular fracture
        • major step off
        • multiple small fragments
    • Malunion
  • Prognosis
    • Malreductions may lead to early short-term stiffness or instability and long-term radiographic arthritis
    • Prognostic variables
      • favorable
        • acute intervention
        • extra-articular fracture
      • negative
        • Bennett fracture
        • Rolando fracture
        • severely comminute fracture
        • delayed intervention
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