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Osteochondral Lesions of the Talus

Discussion

  • although a traumatic etiology is believed to play a major role in production of these lesions, idiopathic osteonecrosis may be another factor;
  • anterolateral lesions:
    • may result from impaction of talus on fibula as the dorsiflexed ankle is forced into inversion (see ankle sprain);
    • the vast majority are caused by trauma;
    • these lesions tend to be shallow;
  • posteromedial lesions:
    • most of these lesions probably arised from trauma (but many will have an atraumatic etiology);
    • may result from impaction of posteromedial talus on tibia, as plantar flexion ankle is forced into inversion and exteranal rotation;
    • these lesions are deeper and cup shaped;
    • exam: palpate just posterior to the medial malleolus with the ankle dorsiflexed (may resemble pending rupture of posterior tib)

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Exam

  • joint line tenderness and effusion;

Radiographs

  • osteochondral frx may be anterior or posterior to dome, requiring plantar or dorsiflexion of ankle to be visible on mortise view;
  • if radiographs are negative consider repeat radiographs in 2-4 weeks;
  • radiographic classification: (Berndt and Harty)
    • note: that radiographic findings may or may not correlate w/ arthroscopic findings nor prognosis;
      • I: small area of compression;
      • II: partially detached osteochondral lesion;
      • III: completely detached, non-displaced fragment;
      • IV: detached and displaced fragment;

Bone Scan

  • usually not ordered until 8-12 weeks following diagnosis;
  • a negative bone scan will r/o the diagnosis;
  • if bone scan is positive then order either CT or MRI;

CT Scan

  • offers more accurate staging of the lesion;

Treatments

Non Operative Treatment

  • no evidence that non wt bearing cast offers improved results over wt bearing casts;
  • no evidence that patients need to be immobilized if they are kept non wt bearing;

Operative Treatment

  • Arthroscopy of the Ankle:
    • osteochondral lesions of the talus can be debrided, and loose bodies and small osteochondral fragments can be removed;
    • use of non-invasive or invasive distraction improves access to joint and allows adequate debridement and curettage of bed;
    • anterolateral lesions can be addressed from the anterolateral portal;
    • in the study by Kumai, et al (1999), the authors noted good clinical results w/ arthroscopy and K wire drilling of the OCD lesions in patients who were younger than 50 years;
    • posteromedial lesions can be difficult to access;
      • w/ large fragments ORIF may be required, w/ osteotomy of the medial malleolus being required for exposure;
      • ORIF allows direct observation of the lesion and accurate repair;
      • w/ ORIF immobilization in a non wt bearing cast is required for 6-10 weeks

References