Flat-top talus

Last revised by Henry Knipe on 15 Sep 2022

Flat-top talus is considered a complication of non-operative treatment of congenital talipes equinovarus (clubfoot) but can also be seen in surgically treated and non-treated patients and the etiology is not clear 1,2. It results in reduced ankle dorsiflexion due to anterior ankle impingement from the talus and/or navicular 1

Radiographic features

Plain radiograph

Talar dome flattening can be described as 3-5:

  • none
  • mild: talar trochlear curve is incongruous with the distal tibial articular surface
  • moderate: moderate incongruity of the articular surfaces or shortened AP curve extent with no incongruity
  • severe: trochlea is completely flat with marked incongruity of the articular surfaces

Other features of flat-top talus include 4,5:

  • increased R/L-ratio (radius-length ratio)
    • on a lateral ankle radiograph, measuring the radius (R) of the talar dome trochlear curvature vs length (L) from posterior extreme to the distal talar head
    • higher R/L-ratios are seen with flatter talar domes
    • normal R/L-ratio reported to be 0.365 mm +/- 0.045 mm

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