Osteochondral Lesions of the Talus Workup

Updated: Feb 11, 2019
  • Author: Christopher F Hyer, DPM, FACFAS; Chief Editor: Thomas C Dowd, MD  more...
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Workup

Radiography

Patients with an acute ankle injury with hemarthrosis or substantial tenderness first undergo weightbearing plain radiography (anteroposterior [AP], lateral, and mortise views). Radiographs in varying degrees of plantarflexion and dorsiflexion may help in diagnosing posteromedial and anterolateral lesions, respectively. [34]  Plain radiographs of the opposite ankle should be considered, especially if symptoms are apparent, because of the 10-25% incidence of a contralateral lesion. [35]

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Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) can be used to identify occult injuries of the subchondral bone and cartilage that may not be detected with routine radiographs. [36, 37]  Postoperative MRI evaluation may also be considered to assess healing after surgical management. [38]

Classic MRI findings include areas of low signal intensity on T1-weighted images, which suggest sclerosis of the bed of the talus and indicate a chronic lesion. [39, 40]  T2-weighted images reveal a rim that represents instability of the osteochondral fragment. [39, 41]  Posttreatment MRI depicts a reduction or disappearance of the low signal intensity on T1-weighted images and the rim on T2-weighted images.

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Arthroscopy

Arthroscopy may be used as the basis for staging osteochondral lesions of the talus (OLTs). In 1995, Cheng et al developed a comprehensive arthroscopic classification system (see Staging). [42]  Typically, arthroscopy is performed to confirm the diagnosis and in conjunction with treatment. Isolated diagnostic arthroscopy is rarely performed.

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Staging

OLTs should be staged. MRI is used to evaluate the quality of the overlying cartilage and to assess the stability of the lesion. [43]  Several staging systems have been developed on the basis of the first system that Berndt and Harty proposed in 1959 (see the image below). [3]  

Berndt and Harty staging system for osteochondral Berndt and Harty staging system for osteochondral lesions of the talus, with grades 1-4.

In 1996, Ferkel modified this classic system and developed another system, based on computed tomography (CT) findings. [44]  (See the images below.) Ferkel's system corresponds to the stages in the Berndt and Harty classification but also considers fragment separation, the presence of subchondral cysts, and the extent of osteonecrosis.

Osteochondral lesions of the talus. Classification Osteochondral lesions of the talus. Classification system based on CT.
Osteochondral lesions of the talus. Modified stagi Osteochondral lesions of the talus. Modified staging system by Loomer et al.

MRI is sensitive in detecting bone signal changes. In 1999, Hepple et al devised the following staging system [45] :

  • Stage 1 - Articular cartilage damage only
  • Stage 2 - Cartilage injury with underlying fracture
  • Stage 2a - Cartilage injury with underlying fracture and edema
  • Stage 2b - Cartilage injury with underlying fracture but no edema
  • Stage 3 - Detached (rim signal) but not displaced fragment
  • Stage 4 - Displaced fragment
  • Stage 5 - Subchondral cyst formation

Cheng et al developed the following arthroscopic staging system [42] :

  • Stage A - Smooth, intact, but soft or ballotable; stable
  • Stage B - Rough surface; stable
  • Stage C - Fibrillation/fissuring; stable
  • Stage D - Flap present or bone exposed; unstable
  • Stage E - Loose, undisplaced fragment; unstable
  • Stage F - Displaced fragment; unstable
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