An ankle reference frame system suitable for medical imaging with partial view of the tibia

Definition of reference frames for the bones articulating at the ankle joint, that can be identified with high accuracy and repeatability, is essential for many biomechanical and clinical applications. Marker-inspired reference frames, representing the majority of exiting reference frame systems provide relatively low repeatability and accuracy since they rely on palpation and/or visual identification of a small number of anatomical landmarks. In this study, we introduce reference frames for the tibia and talus based on bony morphological features that can be easily identified in the 3D renderings of the bones obtained from medical imaging. A procedure for identifying the long axis of the tibia, essential for the tibial reference frame identification, from a partial view of its distal part is also presented.