Anatomy
The osteology of the talus can be conceptualized as a domed box (the body) with a stout cylinder (the neck) projecting anteriorly. The superior articular dome is wider anteriorly than posteriorly, lending greatest stability to the tibiotalar joint in dorsiflexion. The anteriorly projecting talar neck is angled medially and plantarly and terminates in the ellipsoid talar head. Two bony processes protrude from the talar body. The posterior process extends posteromedially from the body and consists of posteromedial and posterolateral tubercles separated by a central sulcus through which the flexor hallucis longus tendon passes. The lateral process extends inferolaterally and bears articular cartilage both superiorly (facing the fibula) and inferiorly (facing the calcaneus). Inferiorly on the talar body, three facets articulate with the calcaneus, comprising the subtalar joint. A deep bony groove divides the anterior and middle facets and the posterior facet. This groove widens out into the sinus tarsi laterally.
A mean 57% of the talar surface is covered by articular cartilage.[3] This unique anatomic feature presents three challenges when treating talus injuries: (1) relatively little surface area is available for vascular inflow, (2) fracture displacement readily impairs the mechanics of nearby joints, and (3) access for surgical treatment requires navigating tight constraints.
High rates of talar osteonecrosis have motivated the investigation of the vascularity of the talus (Figure 1). Quantitative MRI has revealed contributions to talar blood supply by three major arteries: 47% from the posterior tibial artery, 36% from the anterior tibial artery, and 17% from the peroneal artery.[4] A branch of the posterior tibial artery, the artery of the tarsal canal, passes caudal to the talar neck between the posterior and middle facets and is the single most notable vessel supplying the talus. There is a dense cluster of vascular nutrient foramina on the underside of the talar neck, where the artery of the tarsal canal anastomoses with the artery of the tarsal sinus, derived from anterior tibial circulation.[3] Although the talar body was historically thought to receive nearly all blood flow in a retrograde manner from the talar neck, radiographic and plastination studies of cadaver tali have demonstrated concurrent antegrade flow entering the posterior tubercle through an anastomosis between the peroneal and posterior tibial circulations.[3–5]
Figure 1.
Illustration showing the blood supply to the talus.6
J Am Acad Orthop Surg. 2020;28(20):e878-e887. © 2020 American Academy of Orthopaedic Surgeons
