Updated: 10/6/2018

Base of Thumb Fractures

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Questions
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Evidence
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Introduction
  • A base of the thumb metacarpal fracture includes
    • extra-articular fractures 
    • Bennett fracture (partial intra-articular) 
    • Rolando fracture (complete intra-articular) 
    • severely comminuted fracture
  • Epidemiology
    • incidence
      • 80% of thumb fractures involve the metacarpal base
      • the most common pattern is extraarticular epibasal fracture
  • 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
  • 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
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
 • a pure transverse fracture line not involved the articular surface

Intra-articular Bennett  • intra-articular fracture with a palmar radial 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
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
 

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Questions (1)

(OBQ08.91) Which of the following muscles provide the primary deforming forces to Bennett and Rolando fractures (base of the 1st metacarpal fractures)? Review Topic

QID: 477
1

Pronator quadratus

0%

(18/3944)

2

Flexor pollicis longus

1%

(57/3944)

3

Extensor pollicis longus

3%

(100/3944)

4

Adductor pollicis longus and abductor pollicis

9%

(373/3944)

5

Abductor pollicis longus and adductor pollicis

86%

(3379/3944)

ML 2

Select Answer to see Preferred Response

PREFERRED RESPONSE 5
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Topic COMMENTS (7)
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