Talus bone
Encyclopedia
The talus bone or astragalus is a bone in the collection of bones in the foot called the tarsus
. The tarsus forms the lower part of the ankle joint through its articulations with the lateral and medial malleoli of the two bones of the lower leg, the tibia
and fibula. Within the tarsus, it articulates with the calcaneus below and navicular in front. Through these articulations, it transmits the entire weight of the body to the foot.
The second largest of the tarsal bones, it is also one of the bones in the human body with the highest percentage of its surface area covered by articular cartilage
. Additionally, it is also unusual in that it has a retrograde
blood supply, i.e. arterial blood enters the bone at the distal end.
Facing anteriorly, the head
carries the articulate surface of the navicular bone, and the neck
, the roughened area between the body and the head, has small vascular channels.
The body
features several prominent articulate surfaces: On its superior side is the trochlea tali flanked by the articulate facets for the two malleoli. The ankle mortise, the fork-like structure of the malleoli, holds these three articulate surfaces in a steady grip, which guarantees the stability of the ankle joint. However, because the trochlea is wider in front than at the back (approximately 5-6 mm) the stability in the joint vary with the position of the foot: with the foot dorsiflexed (toes pulled upward) the ligaments of the joint are kept stretched, which guarantees the stability of the joint; but with the foot plantarflexed (as when standing on the toes) the narrower width of the trochlea causes the stability to decrease. Behind the trochlea is a posterior process with a medial and a lateral tubercle separated by a groove for the tendon of the flexor hallucis longus
. Exceptionally, the lateral of these tubercles forms an independent bone called os trigonum or "accessory talus". On the bone's inferior side, three articular surfaces serve for the articulation with the calcaneus, and several variously developed articular surfaces exist for the articulation with ligaments.
During the 7-8th intrauterine
month an ossification center is formed in the talus.
The Talus bone lacks a good blood supply. Because of this, healing a broken talus can take longer than most other bones. The bone does not get an ample supply of oxygen through the blood due to the low supply, which prolongs the healing process. One with a broken talus may not be able to walk for many months without crutches and will further wear a walking cast or boot of some kind after that.
Tarsus (skeleton)
In tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...
. The tarsus forms the lower part of the ankle joint through its articulations with the lateral and medial malleoli of the two bones of the lower leg, the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
and fibula. Within the tarsus, it articulates with the calcaneus below and navicular in front. Through these articulations, it transmits the entire weight of the body to the foot.
The second largest of the tarsal bones, it is also one of the bones in the human body with the highest percentage of its surface area covered by articular cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
. Additionally, it is also unusual in that it has a retrograde
Retrograde
-Retrograde:* Retrograde motion, in astronomy, describes retrograde motions of celestial bodies relative to a gravitationally central object* Apparent retrograde motion, in astronomy, is the apparent motion of planets as observed from a particular vantage point...
blood supply, i.e. arterial blood enters the bone at the distal end.
Structure
Though irregular in shape, the talus can be subdivided into three parts.Facing anteriorly, the head
Head of talus
The talus bone of the ankle joint connects the leg to the foot.For descriptive purposes the talus bone is divided into three sections, neck, body and head of talus....
carries the articulate surface of the navicular bone, and the neck
Neck of talus
The neck of talus is directed forward and medialward, and comprises the constricted portion of the bone between the body and the oval head.Its upper and medial surfaces are rough, for the attachment of ligaments; its lateral surface is concave and is continuous below with the deep groove for the...
, the roughened area between the body and the head, has small vascular channels.
The body
Body of talus
The body of the talus comprises most of the volume of the talus bone. It presents with five surfaces.-Superior surface:The superior surface of the body presents, behind, a smooth trochlear surface, the trochlea, for articulation with the tibia....
features several prominent articulate surfaces: On its superior side is the trochlea tali flanked by the articulate facets for the two malleoli. The ankle mortise, the fork-like structure of the malleoli, holds these three articulate surfaces in a steady grip, which guarantees the stability of the ankle joint. However, because the trochlea is wider in front than at the back (approximately 5-6 mm) the stability in the joint vary with the position of the foot: with the foot dorsiflexed (toes pulled upward) the ligaments of the joint are kept stretched, which guarantees the stability of the joint; but with the foot plantarflexed (as when standing on the toes) the narrower width of the trochlea causes the stability to decrease. Behind the trochlea is a posterior process with a medial and a lateral tubercle separated by a groove for the tendon of the flexor hallucis longus
Flexor hallucis longus muscle
The Flexor hallucis longus muscle is a muscle of the leg.It is one of the deep muscles of the posterior compartment of the leg. The other deep muscles of the leg are flexor digitorum longus and tibialis posterior. Tibialis posterior is most powerful of these deep muscles.The Flexor hallucis...
. Exceptionally, the lateral of these tubercles forms an independent bone called os trigonum or "accessory talus". On the bone's inferior side, three articular surfaces serve for the articulation with the calcaneus, and several variously developed articular surfaces exist for the articulation with ligaments.
During the 7-8th intrauterine
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
month an ossification center is formed in the talus.
The Talus bone lacks a good blood supply. Because of this, healing a broken talus can take longer than most other bones. The bone does not get an ample supply of oxygen through the blood due to the low supply, which prolongs the healing process. One with a broken talus may not be able to walk for many months without crutches and will further wear a walking cast or boot of some kind after that.
