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The effect of osseous ankle configuration on chronic ankle instability
  1. Arno Frigg1,
  2. Olaf Magerkurth2,
  3. Victor Valderrabano1,
  4. Hans-Peter Ledermann2,
  5. Beat Hintermann3
  1. 1Orthopaedic Department, Musculoskeletal Care Centre, University Hospital of Basel, Basel, Switzerland
  2. 2Department of Radiology, University Hospital of Basel, Basel, Switzerland
  3. 3Clinic of Orthopaedic Surgery, Kantonsspital, Liestal, Switzerland
  1. Correspondence to:
 Dr A Frigg
 Spitalstrasse 21, Basel CH-4031, Switzerland;mail{at}


Background: Chronic ankle instability (CAI) is a common orthopaedic entity in sport. Although other risk factors have been studied extensively, little is known about how it is influenced by the osseous joint configuration.

Aim: To study the effect of osseous ankle configuration on CAI.

Design: Case–control study, level III.

Setting: Radiological examination with measurement of lateral x rays by an independent radiologist using a digital DICOM/PACS system.

Patients: A group of 52 patients who had had at least three recurrent sprains was compared with an age-matched and sex-matched control group of 52 healthy subjects.

Main outcome measures: The radius of the talar surface, the tibial coverage of the talus (tibiotalar sector) and the height of the talar body were measured.

Results: The talar radius was found to be larger in patients with CAI (21.2 (2.4) mm) than in controls (17.7 (1.9) mm; p<0.001, power >95%). The tibiotalar sector, representing the tibial coverage of the talus, was smaller in patients with CAI (80° (5.1°)) than in controls (88.4° (7.2°); p<0.001, power >95%). No significant difference was observed in the height of the talar body between patients with CAI (28.8 (2.6) mm) and controls (27.5 (4.0) mm; p = 0.055).

Conclusion: CAI is associated with an unstable osseous joint configuration characterised by a larger radius of the talus and a smaller tibiotalar sector. There is evidence that a higher talus might also play some part, particularly in women.

  • CAI, chronic ankle instability

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  • Published Online First 2 February 2007

  • Competing interests: None declared.