Centre of Rotation of the Human Subtalar Joint Using Weight-Bearing Clinical Computed Tomography

Abstract

Accurate in vivo quantification of subtalar joint kinematics can provide important information for the clinical evaluation of subtalar joint function; the analysis of outcome of surgical procedures of the hindfoot; and the design of a replacement subtalar joint prosthesis. The objective of the current study was to explore the potential of full weight-bearing clinical computed tomography (ct) to evaluate the helical axis and centre of rotation of the subtalar joint during inversion and eversion motion. A subject specific methodology was proposed for the definition of the subtalar joint motion combining threedimensional (3D) weight-bearing imaging at different joint positions with digital volume correlation (DVC). The computed subtalar joint helical axis parameters showed consistency across all healthy subjects and in line with previous data under simulated loads. A sphere fitting approach was introduced for the computation of subtalar joint centre of rotation, which allows to demonstrate that this centre of rotation is located in the middle facet of the subtalar joint. Some translation along the helical axis was also observed, reflecting the elasticity of the soft-tissue restraints. This study showed a novel technique for non-invasive quantitative analysis of bone-to-bone motion under full weight-bearing of the hindfoot. Identifying different joint kinematics in patients with ligamentous laxity and instability, or in the presence of stiffness and arthritis, could help clinicians to define optimal patient-specific treatments. The subtalar joint describes an articulation between talus and calcaneus, forming one of two joints of the hindfoot with the tibiotalar or ankle joint above the talus and the subtalar joint below. The talus comprises of three facets (anterior, middle and posterior) that articulate with the mating facets on the calcaneus at the subtalar joint. The bones are connected by a complex of ligamentous structures that connect the talus to the calcaneus and both structures to the adjacent navicular bone, which is intricately involved in hindfoot and midfoot motion (Fig. 1). The subtalar joint is the primary joint involved in motion and posture of the hindfoot in the frontal plane. Motion is complex and it combines dorsiflexion, abduction and eversion in one direction and plantarflexion, abduction and inversion in the other 1. Problems associated to the subtalar joint can have a significant impact on function 2 , preventing participation in sports and normal daily activities. Common pathologies affecting the joint include instability following ligamentous injury 3 , and painful flat feet in children and adults. In addition, end stage ankle and hindfoot arthritis is a major problem that has been shown to affect quality of life as much as end stage heart disease 4,5. Although the incidence of subtalar joint arthritis is unknown, approximately 3.4% of the population aged over 50 has radiographic hindfoot arthritis, which is more than 300,000 people in the UK 6. The most common cause of subtalar joint arthri...

Difference in orientation of the talar articular facets between healthy ankle joints and ankle joints with chronic instability

“…Also, in planning a joint replacement, a sound knowledge of the joint morphology is needed with consideration of the interrelationship of both joint levels. 28 F I G U R E 3 Cylinder radii (mean and standard deviation) of the superior talar facet (TalusSF) and the posteroinferior talar facet (TalusIF). The dot indicates an outliers (>3 times the standard deviation from the mean value).…”

Effect of Lateral Column Lengthening on Subtalar Motion in a Cadaveric Model

“…24 Newer technology using weightbearing computed tomography to determine the center of rotation of the subtalar joint may obviate the limitations of biomechanical studies such as ours by allowing for a more direct and accurate means of assessing the effects of lateral column lengthening on both subtalar and transverse tarsal mechanics. 18…”

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