Three‐dimensional analysis of talar trochlea morphology: Implications for subject‐specific kinematics of the talocrural joint

Abstract

Three-dimensional (3D) behavior of the talocrural joint is primarily determined by the articular surface morphology of the talar trochlea and tibiofibular mortise. However, morphological features of the anterior and posterior regions of the talar trochlea remain unclear. The objectives of this study were to evaluate anterior and posterior radii of the medial and lateral talar trochlea and to estimate subject-specific kinematics of the talocrural joint. Fifty dry tali were scanned using computed tomography to create 3D bone models. Radii of curvature of the anterior and posterior region at both the medial and lateral trochlea were calculated. Orientations of the dorsiflexion and plantarflexion axis passing through the centers of the circles fitted to the anterior region of the medial and lateral trochlea and through the centers of the circles fitted to the posterior region of the medial and lateral trochlea were evaluated, respectively. The anterior radius of the medial trochlea was significantly smaller than that of the lateral trochlea by a mean of 7.8 mm (P < 0.001). The posterior radius of the medial trochlea was larger than that of lateral trochlea in 30 samples (60%) and vice versa in 20 samples (40%). Unilateral asymmetric shape of anterior trochlea would induce external rotation of the talus during ankle dorsiflexion, whereas bilateral asymmetric shape of posterior trochlea would induce opposite axial rotations among subjects during ankle plantarflexion, which would help the physical therapists to restore talocrural joint motions to ideal state for patients with ankle injuries. Clin. Anat. 29:1066-1074, 2016. © 2016 Wiley Periodicals, Inc.

Talar Dome Investigation and Talocrural Joint Axis Analysis Based on Three-Dimensional (3D) Models: Implications for Prosthetic Design

“…Some recent research studies revealed that the talar dome was a saddle-shaped, skewed, truncated cone with laterally oriented apex and the radius of curvature of the lateral border was smaller than the medial border without the fixed rotation axis [19–21], which were different from previous conclusions [10]. Furthermore, the unilateral and bilateral asymmetries between the radii of the medial and lateral talar trochleae were found by dividing the trochleae into anterior and posterior regions, in which the anteromedial radius was smaller than anterolateral or posteromedial radius [22]. These results were similar to one early study that medial trochlea had two parts of different radii, whereas the lateral trochlea had one radius [23].…”

“…Better restoration of the morphology of the talar dome is essential to improve the biomechanical research and ankle implant design [11]. However, the results on the radius of the talar dome were controversial, and the repeatability of their methods was not so good [19–22, 24, 26]. The current study found that bilateral asymmetry circles of the medial and lateral crests of the talar dome with four parts of different radii resulted in dorsiflexion and plantarflexion axes constantly changing throughout the talocrural joint motion.…”

“…On the one hand, intrinsic error could exist when measuring cadaver specimens or manually determining subject points on the three-dimensional (3D) reconstructed model. Thus, the coordinate system established by the landmarks might not be accurate [10, 11, 22–25]. On the other hand, not many studies positioned the foot and lower extremity in the neutral position, in which both the longitudinal axis of the second metatarsal and mechanical axis were parallel to the sagittal plane of gantry during CT image collection [26].…”

Subject-Specific Axes of Rotation Based on Talar Morphology Do Not Improve Predictions of Tibiotalar and Subtalar Joint Kinematics

“…Representation of subject-specific anatomy may be particularly important when modeling the ankle due to the highly variable morphology of the talus. 24,35 Multiple studies have described methods to define subject-specific axes of rotation at the tibiotalar and subtalar joints. 2,9,15,16,28,32,36 These include anatomical landmark methods, which use palpable bony landmarks to estimate the location and orientation of joint axes 9,10 ; functional methods, which require axes be fitted to recorded motion 15,31 ; imaging methods, which directly measure helical axes of rotation 2,14,17,32 ; as well as optimization methods, which fit a pre-defined joint model to a measured motion.…”

“…Here, tibiotalar and subtalar joint kinematics measured in vivo by dual-fluoroscopy served as the reference standard. Given that the morphology of the talus is highly variable across individuals, 24,35 we hypothesized that there would be significant differences in axes of rotation between the generic and subject-specific models. We further hypothesized that the subject-specific models would provide a more accurate representation of in vivo motion and would thereby predict joint kinematics in better agreement with the dual-fluoroscopy results than generic models.…”