A bi-radial approach to define the sagittal geometry of the healthy ankle

Background: Previous descriptions of the sagittal geometry of the tibia and talus have involved single radius curves. The purpose of this investigation was to: determine if the sagittal curvature of the medial and lateral sides of the talus and tibia can be described by dividing the condyles into anterior and posterior regions, determine tibiotalar congruency, and categorize the morphological configurations of the talus and tibia.

Methods: Eighteen subjects underwent weightbearing CT scans and the osseous curvature was analyzed.

Results: For the talus, the medial anterior radius was smaller than the lateral anterior radius. For the distal tibia, the lateral posterior radius was smaller than the medial posterior radius. Tibiotalar congruency varied by region. The most common geometric configuration was two cones, one anterior and one posterior, pointed in opposite directions.

Conclusion: The sagittal profiles of the tibia and talus can be more accurately described using a bi-radial approach as compared to a single radius.