Assessment of Coronal Plane Subtalar Joint Alignment in Peritalar Subluxation via Weight-Bearing Multiplanar Imaging

Evaluation of the subtalar joint using conventional radiographs is difficult. The purpose of this study was to assess how the posterior facet of the subtalar joint is projected on eight standard radiographic views of the foot and ankle. Weightbearing computed tomography (CT) scans of 27 volunteers without ankle pathology were performed. Eight standard views of the foot and ankle (antero‐posterior [AP] view, mortise view, subtalar view, four different Broden views) were reconstructed using digitally reconstructed radiographs (DRRs). The appearance of the posterior facet of the subtalar joint was assessed for each view. In addition, the position of the joint line was projected onto three‐dimensional (3‐D) models of the calcaneus. We found (i) on the AP view of the ankle joint, the posterior part of the posterior facet is visualized and appears convex (calcaneal side); (ii) on the mortise view of the ankle joint, a slightly more anterior part (compared to the AP view) is visualized and appears either convex or flat; (iii) on the subtalar view, the anterior part of the posterior facet is visualized and appears either convex, flat or concave; and (iv) using the Broden views, the posterior and anterior part of the posterior facet can be visualized. This study clarifies which parts of the posterior facet of the subtalar joint are visualized on eight standard views of the foot and ankle. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

Section: Discussionsupporting

confidence: 73%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Imaging of the subtalar joint: A novel approach to an old problem

Krähenbühl

Lenz

Lisonbee

et al. 2019

“…The posterior facet of the subtalar joint is the largest and is always present. There is variation in its orientation and this has been linked to the development and progression of osteoarthritis, and to adult‐acquired flatfoot deformity . The posterior facet is convex in a sagittally oriented plane and flat or slightly concave in a coronally oriented plane …”

mentioning

confidence: 99%

Study on the three‐dimensional orientation of the posterior facet of the subtalar joint using simulated weight‐bearing CT

Kleipool

Dahmen

Vuurberg

et al. 2018

The purpose of this study was to describe the normal 3D orientation and shape of the subtalar calcaneal posterior facet. This is not adequately described in current literature. In a supine position both feet of 20 healthy subjects were imaged in a simulated weight‐bearing CT. A cylinder and plane were fitted to the posterior facet of the surface model. The orientation of both shapes was expressed by two angles in (1) the CT‐based coordinate system with the axis of the foot aligned with the sagittal axis and (2) a coordinate system based on the geometric principal axes of the subject's calcaneus. The subtalar vertical angle was determined in the intersection in three different coronal planes of the cylinder. The cylinder's axis oriented from supero‐postero‐laterally to infero‐antero‐medially. The plane's normal directed supero‐antero‐medially in the CT‐based coordinate system, and supero‐antero‐laterally in the other coordinate system. The subtalar vertical angle was significantly different (p < 0.001) between the three defined coronal planes and increased from anterior to posterior. The mean diameter of the fitted cylinder was 42.0 ± 7.7 mm and the root mean square error was 0.5 ± 0.1 mm. The posterior facet can be modelled as a segment of a cylinder with a supero‐postero‐lateral to infero‐antero‐medial orientation. The morphometry of the posterior facet in a healthy population serves as a reference in identifying abnormal subtalar joint morphology. More generally this study shows the need to include the full 3D morphology in assessing the orientation of the subtalar posterior facet. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1–8, 2018.

Morphologic analysis of the subtalar joint using statistical shape modeling

Krähenbühl

Lenz

Lisonbee

et al. 2020

Weightbearing computed tomography (WBCT) enables visualization of the foot and ankle as patients stand under load. Clinical measurements of WBCT images are generally limited to two‐dimensions, which reduces the ability to quantify complex morphology of individual osseous structures as well as the alignment between two or more bones. The shape and orientation of the healthy/normal subtalar joint, in particular, is not well‐understood, which makes it very difficult to diagnose subtalar pathoanatomy. Herein, we employed statistical shape modeling to evaluate three‐dimensional (3D) shape variation, coverage, space, and congruency of the subtalar joint using WBCT data of 27 asymptomatic healthy individuals. The four most relevant findings were: (A) talar and calcaneal anatomical differences were found regarding the presence of (a) the talar posterior process, (b) calcaneal pitch, and (c) curvature of the calcaneal posterior facet; (B) the talar posterior facet articular surface area was significantly greater than the calcaneal posterior facet articular surface area; (C) the posterior facet varied in joint space distance, whereas the anteromedial facet was even; and (D) the posterior and anteromedial facet of the subtalar joint was consistently congruent. Despite considerable shape variation across the population, the posterior and anteromedial articular facets of the subtalar joint were consistently congruent. Results provide a detailed 3D analysis of the subtalar joint under a weightbearing condition in a healthy population which can be used for comparisons to pathological patient populations. The described SSM approach also shows promise for clinical evaluation of the subtalar joint from 3D surface reconstructions of WBCT images.