Plain weight-bearing radiographs of a healthy foot and ankle: a) anteroposterior view; b) hindfoot alignment view; c) dorso-plantar view; d) lateral view.[1]
The subtalar joint is difficult to evaluate radiographically. Usually a weight-bearing AP or mortise view along with a lateral view is sufficient for foot and ankle assessment.
Hindfoot alignment measurements using plain weight-bearing radiographs and weight-bearing CT scans: a) anteroposterior view, tibiotalar surface angle (TTS) is used to measure inclination of the talus in relation to the tibial axis; b) hindfoot alignment view, the moment arm of the calcaneus and lateral tibio-calcaneal angle are used to assess the hindfoot alignment; c) weight-bearing CT scan, subtalar vertical angle (SVA) is used to measure the subtalar joint axis relative to the ground; d) weight-bearing CT scan, inftal-subtal angle (ISTA) is used to assess the talar morphology and inftal-supcal angle (ISCA) to determine the inclination of the calcaneus in relation to the talus.[1]
Weight-bearing AP or mortise view
Weight-bearing lateral view
Dorso-plantar view allows assessment of the talo-calcaneal angle. This angle is increased in flat feet and reduced in cavus feet.
Hindfoot view (e.g. hindfoot alignment view, long axial view). This allows assessment of the hindfoot axis in chronic ankle instability
Stress radiographs. These aren't generally recommended. Intra-operatively however they can be used to distinguish between ankle and subtalar joint instability
Harries-Beth, Broden, lateral oblique axial views. These can allows proper assessment of the subtalar joint
Hindfoot alignment view.
Long axial view. Also allows viewing hindfoot alignemnt
Subtalar view
References
โ 1.01.1Krรคhenbรผhl et al.. The subtalar joint: A complex mechanism. EFORT open reviews 2017. 2:309-316. PMID: 28828179. DOI. Full Text.