Base of Thumb Injuries

Base of thumb injuries include Bennett and Rolando fractures of the first metacarpal base, extra-articular base fractures and carpometacarpal dislocations. The thumb provides up to 40% of hand function, so intra-articular fractures are reduced accurately, usually with K wires or screw fixation.

Background

  • Thumb provides up to 40% of hand function
    • Total disability = loss of 22% of bodily function
  • CMC is biconcave-convex saddle-shaped joint
  • Axis of MC is pronated and flexed 80o relative to other MC

Imaging

Base of Thumb Injuries, radiograph of a bennett fracture of the thumb metacarpal base
Radiograph of a Bennett fracture of the thumb metacarpal base. Image by Pavel Ševela, Wikimedia Commons, CC BY-SA 4.0.
  • True AP – Robert’s view
  • True lateral – Bett’s view
  • Oblique view
  • Kapandji PA view

Fractures

  • Most common in young (0-16) and elderly (65+)
  • Classification:
    • Extra-articular
    • Partial intra-articular (Bennett)
    • Complete intra-articular (Rolando)
    • Severely comminuted fracture

Extra-articular

  • Metadiaphyseal junction fractures most common (epibasal fracture)
  • Apex dorsal angulation due to AddP, FPL & APB on distal fragment
  • Accept up to 30o angulation
    • Anything more = compensatory MCP hyperextension
  • Management:
    • Closed reduction – axial traction, extension & pronation with direct pressure over fracture
    • ORIF – k-wires, lag screw, plate, ex-fix

Bennett

  • Described by E.H. Bennett in 1882
  • Intra-articular 2 part fracture – volar ulnar fragment
  • Fragment held by anterior oblique ligament attachment to trapezium (beak ligament)
  • MC shaft subluxes dorsal/proximal/radial
  • Mechanism:
    • Axial load on partially flexed MC
  • Look for trapezium fractures and UCL injuries

Gedda Classification

TypeDescription
1Large single ulnar fragment with subluxation of MC base
2Impaction fracture without subluxation of MC base
3Small ulnar avulsion fragment with CMC dislocation

Management

  • Closed reduction – axial traction, abduction and pronation with pressure over MC base
  • Tensions dorsal ligament complex to reduce (Edmunds, 2006)
  • Poorer outcomes with casting alone (Kjaer-Peterson et al. 1990)
  • Closed reduction + intermetacarpal fixation to 2nd MC and/or trapezium
    • Can add k-wire through volar ulnar fragment
  • Open reduction if >1-2mm displacement/intra-articular step (controversial in literature)
    • Wagner approach
  • Consider distraction + ex-fix for fragments too small to fix

Rolando

  • Described by Silvio Rolando in 1910
  • Y or T shaped 3 part intra-articular fracture
    • Volar ulnar fragment + dorsal radial fragment
  • Worse prognosis – over 50% CMC OA (Langhoff et al. 1991)
  • Management:
    • CRIF for simple 3 part fractures if <1mm displacement
    • ORIF if >1mm displacement
    • Distraction + fixation/ligamentous reduction for highly comminuted fractures
      • Traction pinning, external fixation

1st CMC Dislocation

  • Rare (<1% of thumb injuries)
  • Mostly dorsal
  • Mechanism:
    • Axial force on flexed thumb
    • Dorsal force through 1st web space (e.g. handlebar into thumb)
  • Presentation:
    • Pain, swelling and bruising over thenar eminence
    • Unable to form fist

Anatomy

  • 16 ligaments stabilise CMC joint — 4 important ones:
    • Dorsoradial ligament check rein to radial subluxation (most important)
    • Anterior oblique ligament (superficial/deep)
    • Posterior oblique ligament
    • Intermetacarpal ligament

Investigations

  • Standard radiographs
  • MRI
    • Persistent/recurrent instability post reduction
    • Guides ligament reconstruction

Management

  • Closed reduction + immobilisation in extension/pronation
    • Only if stable on reduction
  • Closed reduction + percutaneous pinning
    • Recommended treatment
    • For more unstable injuries
  • Adding dorsal capsuloligamentous reconstruction with FCR autograft + pinning  leads to better strength & ROM and lower pain (Simonian & Trumble 1996)
  • Low incidence of recurrent dislocation

Ulnar Collateral Ligament Injuries

  • Thumb MCP joint stable throughout flexion/extension arc
  • Range of motion is extremely variable – even between sides in same pt
  • Consists of two parts:
    • Proper collateral ligament – taut in flexion
    • Accessory collateral ligament – taut in extension
  • Dynamic stability from adductor pollicis, FPB and EPB
  • Mechanism of injury
    • Excessive radial deviation at MCP joint
  • Acute injury = skier’s thumb
    • Usually distal avulsion
    • 50% have P1 fractures
  • Chronic injury = gamekeeper’s thumb

Physical Exam

  • Can differentiate complete from partial tears
  • Difficult in acute injuries due to pain/spasm
  • Unstable injury:
    • >35o joint angulation on valgus stress of flexed MCP = complete proper collateral lig tear
    • >35o joint angulation on valgus stress of extended MCP = complete accessory collateral lig tear
    • Greater than 20o variation in side to side valgus laxity
    • Lack of firm end point on stress testing

Stener Lesion

  • UCL torn and displaced proximal/superficial to adductor pollicis aponeurosis
  • Aponeurosis interposed between ligament and attachment point = unable to heal
  • Diagnosis:
    • Palpable mass proximal to MCPJ
    • XR – may see bony Stener lesion
    • MRI – specificity 95%, sensitivity 96%
  • Indication for surgical repair

Treatment

  • Acute:
    • Stable injuries/partial tears – 4 weeks immobilisation spica splint/cast
    • Unstable injuries/complete tears – surgical repair
      • Suture repair of ends vs suture anchor repair of avulsions
    • Avulsion fractures with no bony Stener lesion = controversial
      • Generally non-op for undisplaced fractures that are stable on stress testing
        • Be careful with stress testing – may turn undisplaced into displaced lesion
        • Consider leaving for 1-2 weeks then stress testing once pain settled and lesion not as mobile
      • Variable outcomes, painless non-unions, ongoing instability
  • Chronic (gamekeeper’s thumb)
    • Reconstruct only in absence of significant MCPJ arthritis
    • Up to 2yrs can consider mobilisation of UCL from scar and repair to bone with anchors
    • Dynamic procedures – utilising adductor pollicis or EPB
    • Static procedures – free tendon grafts to reconstruct ligaments

Complications

  • General:
    • Reduced grip/pinch strength and reduced function
    • Post-traumatic OA and pain/stiffness
  • Fractures
    • Malunion/non-union
    • Deformity
  • CMC dislocation + UCL injury
    • Recurrent instability
  • Surgical
    • Injury to dorsal branches of SRN
    • Pin site infection
    • Failed repair/reconstruction

References

  1. Carlsen BT & Moran SL. Thumb trauma: Bennett fractures, Rolando fractures, and ulnar collateral ligament injuries. J Hand Surg Am. 2009 May-Jun;34(5):945-52.
  2. Edmunds JO. Traumatic dislocations and instability of the trapeziometacarpal joint of the thumb. Hand Clin. 2006 Aug;22(3):365-92.
  3. Kjaer-Peterson K, Langhoff O, Andersen K. Bennett’s fracture. J Hand Surg Br. 1990 Feb;15(1):58-61.
  4. Langhoff O, Andersen K, Kjaer-Peterson K. Rolando’s fracture. J Hand Surg Br. 1991 Nov;16(4):454-9.
  5. Simonian PT & Trumble TE. Traumatic dislocation of the thumb carpometacarpal joint: early ligamentous reconstruction versus closed reduction and pinning. J Hand Surg Am. 1996 Sep;21(5):802-6.

Contributions

Page written by Dr James Drummond (orthopaedic registrar) 2020

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.