Morphologic analysis of the subtalar joint using statistical shape modeling

Abstract

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.

Assessment of Progressive Collapsing Foot Deformity Using Semiautomated 3D Measurements Derived From Weightbearing CT Scans

“…36,37 However, associated hind-and midfoot deformities pose a particular challenge for an accurate assessment due to their superposition on weightbearing radiography. 20,21 In addition, the patient's position toward the radiographic beam has a marked impact on the measurement. 2,4 The recent introduction of weightbearing (cone-beam) computed tomography (WBCT) systems has enabled us to overcome the aforementioned shortcomings and allows an accurate assessment of foot and ankle disorders.…”

Assessment of Hindfoot Alignment Comparing Weightbearing Radiography to Weightbearing Computed Tomography

“…The human calcaneus may also demonstrate substantial shape variations, as shown in several studies, and thus be misrepresented by a simplified 2D radiographic representation. 31,36,39,42 Several limitations of our study exist. The first relates to the retrospective design with no prespecified exclusion factors; however, since this study included a large consecutive patient cohort with contemporaneously performed HAV and WBCT imaging, the results of the study are generalizable to patient populations.…”

“…Third, the true shape of the plantar aspect of the calcaneus was not analyzed in the present study. Further investigations analyzing shape modeling of the calcaneus 31,43 may provide more insight into these anatomic variations and the effects they have on hindfoot alignment. Fourth, our study introduces a novel measurement method utilizing WBCT to assess hindfoot alignment, which may add clarity or even confusion to existing measurement techniques.…”

Konventionelle Bildgebung Fuß und Sprunggelenk – akut und chronisch

“…Im medialen Bereich des Gelenks zeigte sich im CT dagegen keine Neigung, während im Röntgen weiterhin eine Neigung von 10,8°g emessen werden konnte [41]. Zusätzlich sind die vielen anatomischen Variationen des subtalaren Gelenks zu berücksichtigen [42]. In einer von Colin et al veröffentlichten Arbeit zur Konfiguration des Rückfußes an 59 gesunden Patienten zeigte sich im CT bei 88 % eine konkave Form der posterioren Gelenkfacette.…”