Generality
The tarsus is, in the human being, the set of 7 bones which, in each foot, takes place between the lower extremities of the tibia and fibula and the initial extremities of the 5 metatarsals.
The tarsus inserts numerous ligaments, including the lateral and medial ligaments of the ankle, the plantar fascia, the calcaneosavicular plantar ligament, and the calcaneus-cuboid ligament.
Also, it is the point where the Achilles tendon "inserts"; to be precise, the bone of the tarsus, which houses the Achilles tendon, is the calcaneus.
The tarsus is essential for the correct functionality of the foot and for the correct functionality of the ankle, the latter joint in which the talus and the calcaneus take an active part.
The main problems that can affect the tarsus are traumatic fractures and stress fractures.
What is the tarsus?
The tarsus is, in the human being, the group of 7 bones which, in each foot, resides between the distal ends of the tibia and fibula and the proximal ends of the 5 metatarsals (or metatarsal bones).
BRIEF REVIEW OF WHAT ARE TIBIA, PEOPLE AND METATARSIS
Belonging to the category of long bones, the tibia and fibula are the two bony elements that make up the skeleton of the leg; the leg is the anatomical section of the lower limb that begins just below the knee and ends at the ankle.
At the level of their distal extremities (ie the extremities furthest from the body trunk), the tibia and fibula have two bony prominences, called malleoli (singular malleolus), which take part in the important articulation of the ankle.
Moving on to the 5 metatarsals of the foot, these are the long bones that take place between the tarsus of the foot and the phalanges of the foot; in all 14, the phalanges of the foot are the bones of the toes.
Each metatarsal corresponds to a toe: the first metatarsal corresponds to the big toe, the second metatarsal corresponds to the second toe, the third metatarsal corresponds to the third toe and so on.
Three regions can be recognized in the metatarsals: a central region, called the body; a proximal region, called the base; finally, a distal region, identified with the term head.
The base of the metatarsals is the border point with the tarsal bones, while the head is the border point with the phalanges.
Note: the fibula is also known as a fibula. The adjectives that refer to fibula and fibula are, respectively, fibular and fibular.
THE TARSUS IS THE EQUIVALENT OF THE CARPUS OF THE HAND
The tarsus is equivalent, at the level of the hand, to the carpus. In the carpus, there are 8 bones and they border on the radius and ulna, on the proximal side, and with the 5 metacarpals, on the distal side. The radius and ulna are the bones of the arm and correspond, respectively, to the tibia and fibula; the metacarpals are the equivalent of the metatarsals.
Anatomy
The tarsus is a group of bones, which inserts various ligaments and tendons and which takes part in fundamental joints of the human body.
TARSAL BONES: ASTRAGALUS AND CALCAGNO
The talus and the calcaneus represent the proximal bones of the tarsus and play a fundamental role in the formation of the ankle, that is the joint that allows dorsiflexion, plantarflexion, eversion and inversion of the foot (see the chapter dedicated to the functions ).
In this case, the talus takes place, with its upper margin, inside the concavity deriving from the particular anatomy of the distal extremities of the tibia and fibula; this concavity is called a mortar. The calcaneus, on the other hand, participates in the ankle joint, inserting some extremely important ligaments for the correct functioning of the aforementioned joint element; the ligaments in question are the tibio-calcaneal ligament and the calcaneofibular ligament.
Together, the talus and calcaneus make up the back of the foot (or hindfoot).
The calcaneus and talus are the largest and second largest bones of the tarsus, respectively.
TARSAL BONES: NAVICULAR
The navicular is the intermediate bone of the tarsus group; it resides anterior to the talus, posterior to the three cuneiforms and lateral to the cuboid. It has a protuberance, which serves to insert the posterior tibial tendon.
TARSAL BONES: CUBOID AND WEDGE-SHAPES
The cuboid and the three cuneiforms are the most distal bones of the tarsus.
With a cube-like appearance, the cuboid bone occupies a lateral position with respect to the three cuneiforms and borders the heel, posteriorly, and the last two metatarsals (fourth and fifth metatarsal), anteriorly.
With a wedge-like appearance, the three cuneiforms (lateral, intermediate and medial) reside in front of the navicular bone and behind the first three metatarsals (first, second and third metatarsal).
The particular arrangement of the three cuneiforms and the cuboid allows the neighboring metatarsal bones to form the so-called transverse arch of the foot.
JOINTS OF THE TARSO
The joints in which the bones of the tarsus take part are:
- The ankle or talocrural joint. It represents the most important joint of the foot;
- The subtalar joint. It is the result of the synergism between the talus and the calcaneus;
- The talo-navicular joint. It is the result of the union between the talus and the navicular bone;
- The calcaneus-cuboid joint. It is the result of the relationship between the calcaneus and the cuboid bone.
- The tarsometatarsal joints. They are the articular elements that unite the bases of the metatarsals to the cuneiform bones (metatarsal bones of the first three fingers) and to the cuboid bone (metatarsal bones of the last two fingers).
LIGAMENTS
A ligament is a band of fibrous connective tissue, which connects two bones or two parts of the same bone together.
The ligaments related to the tarsal bones are: the plantar fascia, the calcaneus-navicular plantar ligament, the calcaneus-cuboid ligament and the medial (or deltoid) and lateral ligaments of the ankle.
There plantar fascia it is a long ligament, located on the lower edge of the foot (the so-called sole of the foot); it runs from the heel to the toe bones. Similar in shape to an arch, it allows the foot to bend and acts as a cushion that absorbs the shocks of walking, running, jumping, etc.
The calcaneo-navicular plantar ligament it is the ligamentous element, located on the sole of the foot, which goes from the calcaneus to the navicular bone. Its function is to provide support for the head of the talus.
The calcaneo-cuboid plantar ligament it is the ligament that runs from the calcaneus to the cuboid bone; its task is to help the plantar fascia during curvature.
THE medial ligaments (or deltoids) of the ankle are four separate elements, whose task is to join the tibial malleolus to the "talus in two points (anterior tibial ligament and posterior tibial ligament), to the calcaneus (tibio-calcaneal ligament) and to the" navicular bone (tibio-navicular ligament).
Finally, i lateral ligaments of the ankle they are three separate elements, whose function is to unite the fibular malleolus (ie of the fibula) to the talus in two points (anterior talofibular ligament posterior talofibular ligament) and to the calcaneus (calcaneofibular ligament).
TENDONS
A tendon is a band of fibrous connective tissue, which instead of joining two bones or two parts of the same bone - as ligaments usually do - joins a muscle to a bony element.
Among the tendons that have relations with the bones of the tarsus, the Achilles tendon deserves a mention for its importance within the musculoskeletal system. The Achilles tendon connects the calf muscles (the two twins and the soleus) at the heel; it is essential for walking, running and jumping. Its rupture severely limits a person's motor skills and requires reconstructive surgery, as its spontaneous healing is impossible.
Function
The tarsus is a fundamental element of the human foot, therefore it contributes significantly to the functions of the latter, which are:
- Ensure stability in the standing position;
- Absorb a large part of the weight of the body;
- Allowing for locomotion, the ability to jump and the ability to walk on uneven surfaces.
TARSUS AND ANKLE MOVEMENTS
Through the talus and the calcaneus, the tarsus is a fundamental component for the proper functioning of the ankle.
In fact, thanks to the tarsus (and the distal extremities of the tibia and fibula), the ankle joint is able to perform those movements that are critical for locomotion, running, jumps, etc.; these movements are: dorsiflexion, plantarflexion, the "eversion and" inversion.
- Dorsiflexion: it is the movement that allows you to lift the foot and walk on the heels.
- Plantarflexion: is the movement that allows you to point the foot towards the floor. The human being makes a plantarflexion movement when trying to walk on toes.
- Eversion: means to raise the lateral edge (i.e. the outer edge) of the foot, keeping the medial edge (i.e. the inner edge) on the floor.
- Inversion: means to raise the medial edge of the foot, keeping the lateral edge on the floor.
Associated pathologies
Like all bones in the human body, the bones of the tarsus can also fracture.
Fractures of the tarsal bones can be traumatic in nature (most cases) or due to excessive stress (minority of cases).
Among the bones of the tarsus most prone to traumatic fractures are the talus and the calcaneus.
The navicular bone and once again the calcaneus are among the tarsal bones most prone to stress fractures.
FRACTURE OF THE ASTRAGALUS
The fractures of the talus can be located in two distinct points: on the so-called neck of the talus or on the so-called body of the talus.
In most cases, talus neck fractures occur after excessive dorsiflexion of the foot. This movement, in fact, causes the neck to press, abnormally and violently, against the tibia, breaking due to the impact. When they occur, this type of bone lesions can alter the direct blood flow. to the talus and lead to episodes of osteonecrosis (or avascular necrosis).
Therefore, taking into consideration the fractures of the body of the talus, these are usually the result of jumps made from an excessive height. In these circumstances, in fact, the body of the talus hits violently against the tibio-fibular mortar (see the brief review of the tibia and fibula), thus suffering an injury.
FRACTURE OF CALCAGNO
In general, fractures of the calcaneus are the consequence of impacts that affect the calcaneus and force it violently against the talus.
The main circumstances that cause a heel fracture are falls on the heels.
Heel fractures are injuries capable of giving rise to various late complications, above all arthritis to the damage of the subtalar joint and severe pain during the eversion and inversion movements of the foot.
STRESS FRACTURES
Stress fractures to the tarsal bones are often the result of mechanical stress on the bone or bones that develop the injury. They typically affect those who regularly engage in sports such as running or jogging, as these individuals overload in repeatedly the bones of the tarsus and the entire lower limbs.
TREATMENT OF A TARSUS FRACTURE
Individuals who are victims of a traumatic tarsal fracture must wear a cast - clearly on the fractured foot - for at least 6 weeks and avoid, during this time, putting weight on the limb with the fracture.
Those who are victims of a stress fracture to the tarsal bones can limit themselves to the use of a brace or a crutch, to drastically limit the weight borne by the tarsus.
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