Updated: 10/4/2016

Ring Avulsion Injuries

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Introductions
  • Definition
    • sudden pull on a finger ring results in severe soft tissue injury ranging from circumferential soft tissue laceration to complete amputation  
    • skin, nerves, vessels are often damaged 
  • Epidemiology
    • incidence
      • 150,000 incidents of amputations and degloving in the US per year
      • 5% of upper limb injuries
    • location
      • usually only involves 1 digit (with ring)
    • risk factors
      • working with machinery 
      • wearing a ring
  • Mechanism
    • patients catch their wedding band or other finger ring on moving machinery or protruding object 
    • long segment of macro- and microscopic vascular injury from crushing, shearing and avulsion
  • Prognosis
    • outcomes of injury 
      • extent of injury is greater than what it appears to be
      • poor prognosis because of long segment vascular injury
    • treatment outcomes
      • advances in interposition graft techniques have improved results with ring avulsion replantation
Anatomy
  • Muscles
    • avulsed digits are devoid of muscles and will survive >12h if cooled
  • Skin
    • skin is the finger's strongest soft tissue
      • once the skin tears, the remaining tissue quickly degloves
  • Biomechanics
    • Urbaniak Class I injuries at 80N of traction force
    • Urbaniak Class III injuries at 154N of traction force
    • Standard wedding band (3mm wide, regardless of alloy) will not open at 1000N
Classification
 
Urbaniak Classification
Class
Description
Treatment
Images
Class I Circulation adequate Standard bone and soft tissue care  
Class II Circulation inadequate Vessel repair  
Class III Complete degloving or complete amputation Amputation  
 
Kay, Werntz and Wolff Classification
Class
Description
Treatment
Images
Class I Circulation adequate Standard bone and soft tissue repair
Class II Arterial compromise only Vessel repair
Class III Inadequate circulation with bone, tendon, or nerve injury.
Amputation

 

Class IV Complete degloving or complete amputation.
Amputation

Presentation
  • History
    • may have history of working with machinery, getting caught in door
  • Symptoms
    • pain
    • bleeding
    • lack of sensation at tip
  • Physical exam
    • inspection
      • irrigate wound and inspect for visible avulsed vessel, nerve, tendon, damaged skin edges
      • staggered injury pattern  
        • proximal skin avulsion (from PIPJ to base of digit)
        • distal bone fracture or dislocation (distal to PIPJ, often at DIPJ level)
Imaging
  • Radiographs
    • recommended views
      • Xray both segments (the amputated part, if present, and the remaining digit)  
Treatment
  • Initial
    • place amputated part, if present, in bag with saline-moistened gauze, followed by bag of ice water
    • antibiotics and tetanus prophylaxis
  • Operative
    • replantation +/- vein graft, DIPJ fusion 
      • indications
        • disruption of venous drainage only
        • disruption of venous and arterial flow (requires revascularization)
        • requires intact PIPJ and FDS insertion
      • contraindication
        • complete amputation (especially proximal to PIPJ and FDS insertion) is relative contraindication to replantation
      • outcomes
        • survival
          • lower overall survival for avulsed digits replantation (60%) than finger replantation in general (90%)
          • lower survival for complete (66%) vs incomplete avulsion replantation (78%)
          • lower survival for avulsed thumb (68%) than finger (78%) replantation
            • surgeons more likely to attempt technically difficult avulsed thumb replantation where conditions not favorable because of importance of thumb to hand function (unlike other digits, where revision amputation would be performed instead)
        • sensibility
          • most achieve protective sensibility (2PD 9mm)
          • better sensibility with incomplete avulsion replantation (8mm) than complete (10mm)
        • range of motion
          • average total arc of motion (TAM) of 170-200 degrees
          • better TAM with incomplete avulsion replantation (199 degrees) than complete (174 degrees)
    • revision amputation
      • indications
        • complete degloving
        • bony injury with nerve and vessel injury
        • bony amputation proximal to FDS insertion or proximal to PIPJ
          • replantation likely to leave poor hand function
          • consider revision amputation or ray amputation
Surgical Technique
  • Replantation/revascularization
    • approach
      • under operating microscope mid-lateral approach to digit
    • technique
      • arteries
        • thorough debridement of nonviable tissue
        • thorough arterial debridement (inadequate debridement leads to failure)
        • repair using vein grafts because of significant vascular damage
        • may need another step-down vein graft because of difficulty in arterial size matching (small artery, large vein graft)
        • may reroute arterial pedicle from adjacent digit
          • disadvantage is this sacrifices major artery from adjacent digit
      • veins
        • repair at least 2 veins
        • important factor in revascularization failure
      • bone
        • if amputation occurs at DIPJ, perform primary arthrodesis of DIPJ
      • skin
        • perform full-thickness skin grafts or venous flaps to prevent tight closure or may utilize commercially available synthetic acellular dermal matrix.  
Complications
  • Complications of replantation
    • cold intolerance (70%)
    • revascularization/replantation failure
      • factors include
        • most significant factor is repair of <2 veins
        • vascular damage up to digital pulp
      • smoking and level of bone injury have not been found to affect survival
    • flexion contracture
    • malunion
    • revision surgery
  • Complications of revision amputation
    • hyperaesthesia
 

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