Calcaneus:
Has thin cortex
Compression trabeculae are seen superiorly parallel to the superior surface and traction trabeculae inferiorly perpendicular to the above with neutral triangle between them
The thicked anterior cortex inferior to posterior articular facet is called thalamic portion
Lateral surface: flat, subcutaneous, central peroneal tubercle for calcaneofibular ligament. Lateral talocalcaneal ligament attaches anterosuperiorly to peroneal tubercle
Medial surface: held to talus by interosseous ligament and medial talocalcaneal ligaments. Sustentaculum tali is seen at anterior aspect of medial surface and the groove inferior to it transmits FHL. Neurovascular bundle lies adjacent to medial border, which may be injured during trauma or surgery and is key element in the surgical management of calcaneal fractures
Joints: 4 articulating surfaces: 3 superior - the posterior, middle, and anterior facets; and 1 anterior - calcaneocuboid joint. Calcaneal sulcus is seen between posterior and middle & anterior facets running posteromedially. Sinus tarsi is canal formed between this calcaneal sulcus and talus. Sustentaculum tali supports middle calcaneal facet, calcaneal beak supports anterior facet
Talus:
Head - convex. Its anterior surface articulates with navicular bone, inferomedial surface articulates with anterior and middle facets of calcaneus, spring ligament and deltoid ligament Neck - narrow superiorly, inferiorly and laterally
Body - wide anteriorly narrow posteriorly
Tubercles - lateral and posterior. Posterior is divided into medial and lateral tubercles by groove for FHL tendon. Os trigonum (50% of population) is seen over lateral tubercle.
Joints - Ankle joint = talotibial joint. Talocalcaneal joint = subtalar joint. Talonavicular joint
Blood supply - 3 extraosseous arteries - posterior tibial, dorsalis pedis and peroneal and also introsseous arteries
References:
1. Daftary A et al. Fractures of the Calcaneus: A Review with Emphasis on CT. RadioGraphics 2005;25:1215-1226
2. Pearce DH et al.Avascular Necrosis of the Talus: A Pictorial Essay. Radiographics 2005;25:399-410
