The Common Vein
Copyright 2010
Definition
The talus bone of the hind foot is characterized by it transmitting all the body weight when standing. The talus also has no muscular attachments. It is the 2nd largest of the tarsal bones.
It is part of the tarsal bones of the foot. The talus articulates with the fibula, tibia, and calcaneus. It consists of bone and cartilage.
Its unique structural feature is that it is about 60% covered with articular cartilage. The talus has a body, neck, and head making up its very irregular shape. The blood supply is retrograde, meaning that it enters from the distal end.
The head of the talus articulates with the navicular and the calcaneus.
The neck is located between the body and the head. This portion of the talus has many vascular channels.
The body articulates proximally articulates with the medial and lateral malleoli of the ankle joint mortise. Posteriorly, the talus has the trochlea superiorly and the posterior process. The posterior process is where the groove for the tendon of the flexor hallucis longus sits, the medial tubercle, and the lateral tubercle. In some individuals, there can be an os trigonum or accessory talus off the lateral tubercle.
Inferiorly, the talus articulates with the calcaneus at 3 sites.
During the 7th to 8th month of the fetus, the ossification center of the talus is formed. The talus as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in embryo.
The function of the talus is to transmit the weight of the human body from the tibia to the calcaneus through the talar body and to the forefoot through the talar head and then the spring ligament. The talus receives 5 to 10 times the body weight during normal ambulation.
Common diseases include anterior impingement syndrome of the ankle, arthritis, osteochondral defects, dislocation, fracture, congenital vertical talus, osteomyelitis, osteochondritis dissecans, coalition, and avascular necrosis.
Anterior impingement syndrome of the ankle is a condition of either soft tissue or bony impingement. Soft tissue impingement can be due to chronic instability from ankle sprains. Bony impingement can result from an anterior tibiotalar spur, extreme dorsiflexion during activities (ie ballet) impinging the tibia on the talar neck, a natural sulcus, or the formation of exostoses (new bone formation).
Arthritis can occur as a result of aging, rheumatoid arthritis, or as a result of post-traumatic changes.
Osteochondral defects can occur after trauma most commonly. Average age of patients with this condition is between 20-35 yrs.
Subtalar dislocation involves dislocation of the talonavicular and talocalcaneal joints usually as a result of trauma.
Congenital vertical talus is also known as “Rocker-Bottom” foot due to its rounded appearance. The shape of the foot is similar to a wheel. The condition is associated with neurologic and chromosomal disorders (including Edward’s Syndrome/Trisomy 18).
Osteomyelitis is an infection of the bone typically due to bacteria.
Osteochondritis dissecans is an osteochondral defect with partial or complete separation of a bone fragment.
A talocalcaneal coalition is a osseous, cartilaginous, or fibrous connection between the talus and the calcaneus that usually ossifies between 12 and 15 years of age and can cause pain and limited range of motion.
Avascular necrosis of the talus is a result of fracture or dislocation and the delicate blood supply to the talus.
Commonly used diagnostic procedures include clinical history, physical exam, plain radiographs, CT scan, bone scan, and MRI.
It is usually treated with either non-operative methods or operative methods. Arthritis can be treated with surgery, physical therapy, or NSAIDs. Fractures and dislocations of the talus can be treated with either closed reduction or surgery. Congenital vertical talus is usually treated surgically at 12 to 18 months of age. Osteomyelitis is treated with surgery and antibiotics. Coalitions may be treated nonoperatively with cast or surgically by excision of the bony bar or joint fusion.
References
Elstrom J, Virkus W, Pankovich (eds), Handbook of Fractures (3rd edition), McGraw Hill, New York, NY, 2006.
Koval K, Zuckerman J (eds), Handbook of Fractures (3rd edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.
Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Wheeless? Textbook of Orthopaedics: Injuries of the Talus (http://www.wheelessonline.com/ortho/injuries_of_the_talus)