Base of Thumb Fractures

Base of Thumb Fractures

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Case

35 year old male comes in after a fall whilst playing contact sport. He has pain and deformity to the thumb with gross swelling and bruising.

Summary

Thumb function constitutes 50% of overall hand function. Recognition, early diagnosis and treatment generally result in better functional outcomes after thumb injuries. 80% of thumb fractures involve the base of the thumb or metacarpal. The 1^st metacarpal is the most commonly injured as it has no protection from adjacent bones and less stability.

Presentation

• History
  • Usually caused by an injury involving an axial force applied to the thumb whilst it is flexed.
  • In the younger age this is usually a sports injury or road traffic accident.
  • In the older age-group (>50 years) the injury is usually an accidental fall.
  • Immediate pain, swelling, bruising and limitation of movement following injury
• Delayed presentations
  • Hyperextension deformity may be present with a history more in keeping with base of thumb osteoarthritis.
  • Swelling and bruising may have resolved with reduction in pain and partial restoration of function.

'Examination

• Look
  • Localised swelling and bruising
  • Deformity or asymmetry
  • Look for any skin breaches suggestive of open fracture (High risk of infection)
• Feel
  • Localised tenderness over base of thumb
  • Check neurovascular status (thumb tip pink, warm, CRT<2s, sensation to light touch)
• Move
  • Pain limiting ROM

Figure1: Red Flags: Skin overlying the fracture compromised = OPEN fracture

Investigation

• Imaging
• X-ray Hand/Thumb (PA/Lateral/Oblique views)(Figure 1)
• CT Thumb
  • Not routinely performed, useful to confirm joint subluxation or for pre-operative planning
  • Not typically available to primary care clinicians
• MRI shoulder
  • Not routinely performed, useful if associated soft tissue injury suspected
  • Not typically available to primary care clinicians

Differentials

• Soft tissue injury

Classification Based on fracture pattern (Figure 2)

• Extra-articular (Figure 1a and b)
• Oblique
• Transverse
• Intra-articular
• Bennett (Figure 1c and d)
• Rolando (Figure 1e)
• Comminuted

Extra-articular Fracture

• Usually at meta-diaphyseal junction
• Flexor pollicis longus tends to pull the distal fragment into flexion
• Abductor pollicis holds the proximal fragment in abduction

Bennett Fracture

• Fracture line into the joint surface
• Palmar ulna fragment held in place by strong anterior oblique (beak) ligament
• Abductor pollicis longus pulls shaft radially and dorsally can leave the joint subluxed/dislocated

Rolando' Fracture

• Fracture line into the joint surface
• Y or T shaped fracture line
• Multiple fragments

Figure 2

Management

Conservative

• Closed reduction + thumb spica cast/splinting
• Elevation
• NSAIDs
• Physiotherapy after immobilisation

Operative

• Closed reduction + k-wire fixation
• Open reduction + fixation with screws or plates
• Distraction and external fixation

When to Refer

See treatment algorithm (figure 3)

Prognosis/Managing Expectations

• Immobilisation for 4-6 weeks
• Mobilisation and functional rehabilitation 3-4 months
• Incidence of post-traumatic osteoarthritis unknown but higher risk with intra-articular base of thumb fractures

Treatment Algorithm