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Updated: Jan 7 2024

Mallet Finger

Images - lateral_moved.jpg
  • Summary
    • Mallet Finger is a finger deformity caused by disruption of the terminal extensor tendon distal to DIP joint
    • Diagnosis is made clinically when the distal phalanx rests at ~45° of flexion with lack of active DIP extension.
    • Treatment is usually extension splinting of DIP joint for 6-8 weeks. Surgical management is indicated for volar subluxation of the distal phalanx, chronic injuries, or significant arthritis. 
  • Epidemiology
    • Risk factors
      • usually occur in the work environment or during participation in sports
    • Demographics
      • common in young to middle-aged males and older females
    • Anatomic location
      • most frequently involves long (most common), ring and small fingers of dominant hand
      • Zone 1 in the Kleinert and Verdant classification of extensor tendon injuries
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • traumatic impaction blow
          • usually caused by a traumatic impaction blow (i.e. sudden forced flexion) to the tip of the finger in the extended position.
          • forces the DIP joint into forced flexion
        • dorsal laceration
          • a less common mechanism of injury is a sharp or crushing-type laceration to the dorsal DIP joint
  • Classification
      • Doyle's Classification of Mallet Finger Injuries
      • Type I
      • Closed injury with or without small dorsal avulsion fracture
      • Type II
      • Open injury (laceration)
      • Type III
      • Open injury (deep soft tissue abrasion involving loss of skin and tendon substance)
      • Type IV
      • Mallet fracture
      • A = distal phalanx physeal injury (pediatrics)
      • B = fracture fragment involving 20% to 50% of articular surface (adult)
      • C = fracture fragment >50% of articular surface (adult)
  • Presentation
    • Symptoms
      • primary symptoms
        • painful and swollen DIP joint following impaction injury to finger
          • often in ball sports
    • Physical exam
      • inspection
        • fingertip rest at ~45° of flexion
      • motion
        • lack of active DIP extension
  • Imaging
    • Radiographs
      • recommended views
        • AP/Lateral of the finger
      • findings
        • often see bony avulsion at the base of the distal phalanx
        • may be a ligamentous injury with normal bony anatomy
        • assess for distal phalanx subluxation
    • Ultrasound
      • not typically necessary
      • findings
        • loss of tendon motion
        • complete or partial thickness tears
        • avulsion fracture
        • fluid at the tendon insertion
  • Treatment
    • Nonoperative
      • extension splinting of DIP joint for 6-8 weeks for 24 hours daily
        • indications
          • acute soft tissue injury (<12 weeks)
          • small or minimally displaced bony mallet injury without joint subluxation
          • chronic injury (>12 weeks) with supple, congruent, and nonarthritic joint
        • technique
          • maintain free movement of the PIP joint
            • if in a swan-neck posture at the time of injury, block PIP full extension with dorsal blocking splint
          • worn for 6-8 weeks
            • typically followed by 4 weeks of nocturnal splinting (controversial)
            • bony injuries splinted until fracture union
          • volar splinting has fewer complications than dorsal splinting
          • avoid hyperextension
            • due to risk of skin necrosis
          • begin progressive flexion exercises at 6 weeks
        • Outcomes
          • No differences in patient satisfaction or extensor lag between operative and nonoperative treatment
          • ~80% of patients have satisfactory outcome
    • Operative
      • CRPP vs ORIF
        • indications
          • absolute indications
            • volar subluxation of distal phalanx
          • relative indications
            • >50% of articular surface involved
            • >2mm articular gap
            • open injuries
      • surgical repair of the terminal tendon
        • indications
          • traumatic tendon laceration
      • surgical reconstruction of terminal tendon
        • indications
          • chronic injury (> 12 weeks) without contracture
          • segmental tendon loss
        • outcomes
          • tendon reconstruction has a high complication rate (~ 50%)
      • DIP arthrodesis
        • indications
          • painful, stiff, arthritic DIP joint
      • Swan neck deformity correction
        • indications
          • Swan neck deformity present
  • Techniques
    • CRPP
      • approach
        • percutaneous
      • fixation
        • dorsal extension block pinning with joint pinned in extension
          • Ishiguro technique vs. Modified Ishiguro technique
    • ORIF
      • approach
        • dorsal midline incision
      • fixation
        • simple pin fixation
        • dorsal blocking pin
    • Surgical reconstruction of terminal tendon
      • repair
        • direct repair often accompanied by trans-articular pin
        • this may be done with direct repair/tendon advancement, tenodermodesis, or spiral oblique retinacular ligament reconstruction
    • Swan neck deformity correction
      • techniques to correct Swan neck deformity include
        • lateral band tenodesis
        • FDS tenodesis
        • Fowler central slip tenotomy
        • minimal Swan Neck deformities may correct with treatment of the DIP pathology alone
  • Complications
    • Extensor lag
      • a slight residual extensor lag of < 10° may be present in up to 40% after either closed or operative treatment, however, no functional deficit.
      • lengthening of the terminal tendon by 1mm leads to a 25 degree extensor lag
    • Reduced DIP flexion
      • risk for adhesions due to close proximity to the skin and the DIP joint
      • shortening the extensor tendon by 1mm leads to reduced DIP flexion
    • Swan neck deformities
      • occurs due to
        • retracted terminal insertion leading to proportionally excessive pull on P2 from central slip
        • attenuation of volar plate and transverse retinacular ligament at PIP joint
        • dorsal subluxation of lateral bands
        • resulting PIP hyperextension
        • contracture of triangular ligament maintains deformity
    • Skin issues (maceration, ulceration, and nail deformities)
      • occurs at some degree in about 70% of those treated nonoperatively
      • limited soft tissue coverage puts the wound at risk of dehiscence and infection
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