The Clinical Biomechanics Award 2013 -- presented by the International Society of Biomechanics: new observations on the morphology of the talar dome and its relationship to ankle kinematics.
BACKGROUND
Ankle passive kinematics is determined primarily by articular surface morphology and ligament constraints. Previous morphological studies concluded that the talar dome can be approximated by a truncated cone, whose apex is directed medially and whose major axis is the axis of rotation of the ankle. This and other functional morphology concepts were evaluated in this study whose goal was to describe and quantify the 3D morphology of the talus using 3D image-based bone models and engineering software tools.


METHODS
CT data from 26 healthy adults were processed to produce 3D renderings of the talus and were followed by morphological measurements including the radii of curvature of circles fitted to the medial and lateral borders of the trochlea and radii of curvature of coronal sections.


RESULTS
The surfaces containing the medial and lateral borders of the trochlea are not parallel and the radius of curvature of the medial border is larger than the lateral border. In the coronal plane the trochlear surface was mostly concave.


CONCLUSIONS
The trochlear surface can be modeled as a skewed truncated conic saddle shape with its apex oriented laterally rather than medially as postulated by Inman. Such shape is compatible, as opposed to Inman's cone postulate, with the observed pronation/supination and provides stable congruency in movements of inversion/eversion. The results challenge the fundamental theories of functional morphology of the ankle and suggest that these new findings should be considered in future biomechanical research and in clinical applications such as design of total ankle replacements.
Department of Mechanical Engineering and Mechanics, Drexel University, 32nd and Chestnut Streets, Philadelphia, PA 19104, USA. Electronic address: ssielger@coe.drexel.edu.
Sorin
S
Siegler
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
Jason
J
Toy
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
Damani
D
Seale
The Rothman Institute, Thomas Jefferson University, Philadelphia, PA, USA.
David
D
Pedowitz
D000328:Adult; D000842:Ankle; D000843:Ankle Joint / Q000033:anatomy & histology / Q000502:physiology; D001363:Awards and Prizes; D001696:Biomechanical Phenomena; D001703:Biophysics; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D011859:Radiography; D012399:Rotation; D013628:Talus / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology
Ankle kinematics; Functional morphology; Saddle shape; Talus; Trochlear surface; Truncated cone