Sorin Siegler1, Jason Toy2, Damani Seale2, David Pedowitz3. 1. Department of Mechanical Engineering and Mechanics, Drexel University, 32nd and Chestnut Streets, Philadelphia, PA 19104, USA. Electronic address: ssielger@coe.drexel.edu. 2. Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA. 3. The Rothman Institute, Thomas Jefferson University, Philadelphia, PA, USA.
Abstract
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. FINDINGS: 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. INTERPRETATION: 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.
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. FINDINGS: 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. INTERPRETATION: 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.
Authors: Ian D Hutchinson; Josh R Baxter; Susannah Gilbert; MaCalus V Hogan; Jeff Ling; Stuart M Saunders; Hongsheng Wang; John G Kennedy Journal: Clin Orthop Relat Res Date: 2015-12-21 Impact factor: 4.176
Authors: Joe A I Prinold; Claudia Mazzà; Roberto Di Marco; Iain Hannah; Clara Malattia; Silvia Magni-Manzoni; Maurizio Petrarca; Anna B Ronchetti; Laura Tanturri de Horatio; E H Pieter van Dijkhuizen; Stefan Wesarg; Marco Viceconti Journal: Ann Biomed Eng Date: 2015-09-15 Impact factor: 3.934