Bone: Bones of the Foot: Talus & calcaneus

The **talus** is a bone in the hindfoot that articulates with the tibia, fibula, calcaneus, and navicular bones.

The talus has been described as having three main components: a head, a neck, and a body.

* The talar body has a curved smooth trochlear surface also termed the talar dome, which is covered with cartilage. Other parts of the talar body include the central portion, the posterior process and the lateral process.
* The talar head is the part that articulates with the navicular bone.
* The talar neck connects the talar head and body, which is inclined downwards distally and medially.
* Posterior process: Groove between medial & lateral tubercles for flexor hallucis longus tendon

Articulations

* talar body
	+ tibia, fibula, and 3 inferior facets articulate with calcaneus
	+ lateral surface: lateral malleolus of distal fibula
	+ trochlea: distal tibia
* talar head: navicular bone

Attachments:

2/3 covered by cartilage, dominant blood supply enters neck. No muscles originate or insert on the talus.

Ligamentous

* anterior talofibular ligament
* posterior talofibular ligament
* talocalcaneal ligament
* interosseous talocalcaneal ligament
* deltoid ligament

Blood supply

* posterior tibial artery
* anterior tibial artery/dorsalis pedis artery
* peroneal/fibular arteries

The vascular supply to the talus is considered tenuous due to the lack of muscular attachment to the bone 1.

Nerve supply

* deep fibular nerve
* posterior tibial nerve
* saphenous nerve
* sural nerves

Variant anatomy

* the posterior process of the talus may not be fused to the central portion of the body, resulting in an os trigonum
* congenital vertical talus

The **calcaneus** is the largest bone in the hindfoot. It articulates with the talus superiorly and the cuboid anteriorly, and shares a joint space with the talonavicular joint, appropriately called the talocalcaneonavicular joint. The calcaneus transfers most of the body weight from the lower limb to the ground.

The calcaneus is an irregular, roughly box-shaped bone sitting below the talus.

Osteology:

**Dorsal part of the calcaneus**

* circular and provides the attachment site for the Achilles tendon posteriorly

* calcaneal tuberosity:

* + medial and lateral process at plantar surface

* + calcaneal tubercle at anterior projection for short plantar ligament

**Lateral part of the calcaneus:**

* fibular trochlea (peroneal tubercle), where the tendons of the fibularis brevis and longus muscles pass.

**Medial part part of calcaneus:**

* sustentaculum tali which supports the anteromedial part of the talus.

* + inferiorly is a groove accommodating the flexor hallucis longus tendon and superiorly facet for the middle portion of the subtalar joint.

**Superior part of calcaneus:**

* The anterior and posterior facets of the talocalcaneal joint

* Between these two facets runs a the calcaneal sulcus, which together with the talar sulcus superiorly forms the tarsal sinus (sinus tarsi).

Articulations

Superiorly, the calcaneus articulates with the talus at the talocalcaneal joint, also known as the subtalar joint, making contact at anterior, middle and posterior facets.

Anterior process of the calcaneus articulates with the navicular (calcaneonavicular joint) and the cuboid (calcaneocuboid joint) bones.

Attachments

**Musculotendinous**

* triceps surae, i.e. gastrocnemius and soleus (insertion: calcaneal tuberosity through calcaneal/Achilles tendon)
* abductor hallucis (origin: medial process of calcaneal tuberosity
* flexor digitorum brevis (origin: calcaneal tuberosity)
* quadratus plantae (origin: plantar surface of calcaneus)
* abductor digit minimi (origin: medial and lateral process of calcaneal tuberosity)
* extensor digitorum brevis (origin: dorsolateral)
* extensor hallucis brevis (origin: dorsal, tarsal sinus)

**Ligamentous**

* lateral: lateral collateral ligament of the ankle joint
* inferior: short plantar ligament (at calcaneal tubercle)
* superior: tarsal sinus ligaments, including:
	+ cervical ligament
	+ talocalcaneal interosseous ligament,
	+ lateral, intermediate, and medial roots of the inferior extensor retinaculum
* anterior: plantar calcaneonavicular ligament (the spring ligament)

Variant anatomy

* os calcaneus secundarius
* talocalcaneal coalition