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

Abstract

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.

Typical Shape Differences in the Subtalar Joint Bones Between Subjects with Chronic Ankle Instability and Controls

“…All CAI patients visited Amsterdam UMC for persistent complaints of ankle instability in combination with recurrent lateral sprains, with or without pain and had undergone non‐surgical treatments at least for 6 months without success. Healthy controls ( n = 40) were the individuals who had voluntarily undergone CT scanning either as a part of a study investigating the in‐vivo measured range of motion of the STJ (20 healthy controls) or as a part of a study on the 3D orientation of the posterior facet of the STJ (20 healthy controls). None of the volunteers had concomitant ankle injury or other joint pathology, recorded complaints, or surgery of the lower extremities.…”

“…As all CT scans were retrospectively acquired from the CAI patients, the medical ethical committee provided a waiver. Regarding the healthy controls, the participating volunteers had signed informed consents prior to image acquisition and participation in the previously performed studies . Both studies were also approved by the medical ethics committee of Amsterdam UMC.…”

Bilateral symmetry of the subtalar joint facets and the relationship between the morphology and osteoarthritic changes

“…For the present study two data sets were used. The first data set was acquired for the present study, and the second comes from a previous study (Kleipool et al, 2019).…”

“…As mentioned in the beginning of this section, data from a previous study on living individuals were also included (Kleipool et al, 2019) to account for the 3D morphology of the posterior facet compared to The posterior facet is separated from the middle, but the middle is connected to the anterior facet by a small bridge. Type C: The posterior facet is separated, but the anterior and middle facets form one facet.…”

Can Weightbearing Computed Tomography Scans Be Used to Diagnose Subtalar Joint Instability? A Cadaver Study

“…2,4 While conventional radiographs are limited in assessing the subtalar joint, weightbearing computed tomography (CT) scans have demonstrated emerging diagnostic applications as they offer an accurate representation of hindfoot joint alignment under weightbearing conditions. [22][23][24][25] However, the clinical use of this imaging modality to diagnose subtalar joint instability has yet to be investigated. We hypothesized that isolated subtalar joint instability can accurately be diagnosed when using weightbearing CT scans in a cadaver model.…”