Updated: 5/15/2021

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 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
  • 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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(SBQ17SE.15) A 38-year-old right-hand-dominant computer programmer trips over his cape and falls on his right hand at a renaissance fair. He experiences immediate pain and swelling about the base of his right thumb. He presents to your office where initial radiographs are obtained (Figure A). The muscles responsible for the characteristic deforming forces on the thumb metacarpal shaft are innervated by which nerve(s)?

QID: 211270
FIGURES:
1

Ulnar nerve only

4%

(81/1912)

2

Ulnar and anterior interosseous nerve (AIN)

12%

(237/1912)

3

Ulnar and posterior interosseous nerve (PIN)

48%

(921/1912)

4

Ulnar and recurrent branch of the median nerve

24%

(462/1912)

5

Recurrent branch of the median nerve and AIN

10%

(190/1912)

L 4 A

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

QID: 477
1

Pronator quadratus

0%

(24/5289)

2

Flexor pollicis longus

1%

(73/5289)

3

Extensor pollicis longus

2%

(127/5289)

4

Adductor pollicis longus and abductor pollicis

10%

(533/5289)

5

Abductor pollicis longus and adductor pollicis

85%

(4507/5289)

L 2 C

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