Generality
The tarsus is, in the human being, the set of 7 bones which, in each foot, takes place between the lower extremities of tibia and fibula and the initial ends of the 5 metatarsals.
The tarsus inserts into numerous ligaments, including the lateral and medial ligaments of the ankle, the plantar fascia, the calcareous-navicular plantar ligament and the calcaneo-cuboid ligament.
Moreover, it is the point where the Achilles tendon is inserted; to be precise, the tarsus bone, which houses the Achilles tendon, is the calcaneus.
The tarsus is fundamental for the correct functionality of the foot and for the correct functionality of the ankle, the latter being an active part of the talus and calcaneus.
The main problems that can affect the tarsus are traumatic fractures and stress fractures.
What is tarsus?
The tarsus is, in the human being, the group of 7 bones which, in each foot, reside between the distal extremities of the tibia and fibula and the proximal ends of the 5 metatarsals (or metatarsal bones).
BRIEF REVIEW OF WHAT ARE TIBIA, PERONE AND METATARSI
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 tract of the lower limb that begins just below the knee and ends at the ankle .
At the level of their distal extremities (ie the most distant extremities from the trunk of the body), tibia and fibula present two bony prominences, called malleoli (singular malleolus ), which take part in the important articulation of the ankle .
Turning then 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.
To each metatarsus corresponds a toe: the first metatarsus corresponds to the big toe, the second metatarsus corresponds to the second toe, to the third metatarsal corresponds the third toe and so on.
In the metatarsals, three regions can be identified: 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 fibula. The adjectives that refer to fibula and fibula are, respectively, peroneal and fibular.
THE TARSO IS THE EQUIVALENT OF THE CARO OF THE HAND
The tarsus is equivalent to the carpus at the level of the hand. In the carpus, the bones are 8 and border with radius and ulna, on the proximal side, and with the 5 metacarpals, on the distal side. Radio and ulna are the bones of the arm and correspond, respectively, to tibia and fibula; the pasterns are the equivalent of metatarsals.
Anatomy
The tarsus is a group of bones, which gives insertion to various ligaments and tendons and which takes part in fundamental joints of the human body.
BONE TARSALI: ASTRAGALO 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, subversion and inversion of the foot (see the chapter dedicated to the functions).
In this case, the astragalus takes place, with its upper margin, inside the concavity deriving from the particular anatomy of the distal extremities of tibia and fibula; this concavity is called a mortar . The calcaneus, on the other hand, participates in the ankle joint, giving insertion to some extremely important ligaments for the correct functioning of the aforementioned joint element; the ligaments in question are the tibio-calcaneal ligament and the calcaneo-fibular ligament .
Together, talus and calcaneus form the back of the foot (or hindfoot).
The calcaneus and the talus are, respectively, the largest bone and the second largest bone in the tarsus.
BONE TARSALI: NAVICULATE
The navicular is the intermediate bone of the tarsus group; it resides anteriorly to the astragalus, posteriorly to the three cuneiforms and laterally to the cuboid. It has a protuberance, which serves to give insertion to the posterior tibial tendon .
BONE TARSALI: CUBOID AND CUNEIFORMES
The cuboid and the three cuneiforms are the most distal bones of the tarsus.
Looking like a cube, the cuboid bone occupies a lateral position with respect to the three cuneiforms and borders on the heel, posteriorly, and with the last two metatarsals (fourth and fifth metatarsus), anteriorly.
Looking like a wedge, the three cuneiforms (lateral, intermediate and medial) reside in front of the navicular bone and behind the first three metatarsals (first, second and third metatarsus).
The particular arrangement of the three cuneiforms and the cuboid allows the neighboring metatarsal bones to constitute the so-called transverse arch of the foot .
TARSO JOINTS
The joints to which the bones of the tarsus take part are:
- The ankle or talocrural joint . It represents the most important articulation of the foot;
- The subtalar joint . It is the result of the synergy between astragalus and heel bone;
- The talo-navicular joint . It is the result of the union between the talus and the navicular bone;
- The calcaneo-cuboid joint . It is the result of the relationship between calcaneus and cuboid bone.
- The tarsus-metatarsal 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.
The ligaments that relate to the bones of the tarsus are: the plantar fascia, the calcareous-navicular plantar ligament, the calcaneo-cuboid ligament, and the medial (or deltoid ) and lateral ligaments of the ankle .
The plantar fascia 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 bones of the fingers. Similar in shape to an arch, it allows the curvature of the foot and acts as a cushion that absorbs the shocks of a walk, a run, a jump etc.
The plantar calcaneo-navicular ligament 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 to the head of the talus.
The plantar calcaneo-cuboid ligament is the ligament that runs from the calcaneus to the cuboid bone; its job is to help the plantar fascia during bending.
The medial (or deltoid) ligaments of the ankle are four separate elements, whose task is to join the tibial malleolus to the talus at two points (anterior talo-tibial ligament and posterior talo-tibial ligament), to the calcaneus (tibio-calcaneal ligament) and to the navicular bone (tibio-navicular ligament).
Finally, the lateral ligaments of the ankle are three separate elements, whose function is to join the peroneal malleolus (that is, the fibula) to the astragalus in two points (anterior talo-fibular ligament ligament-fibular ligament ligament) and to the calcaneus fibular).
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 normally do - joins a muscle to a bone element.
Among the tendons that have relations with the bones of the tarsus, the Achilles tendon deserves a mention, due to its importance within the locomotor apparatus. The Achilles tendon connects the calf muscles (the twins and the soleus) to the heel; It is essential for walking, running and jumping. Its break severely limits the motor skills of a person and requires reconstructive surgery, as it is impossible for her to heal spontaneously.
Function
The tarsus is a fundamental element of the human foot, therefore it contributes in a decisive way to the functions of the latter, which are:
- Ensure stability in the standing position;
- Absorb a good part of your body weight;
- Allow locomotion, the ability to make jumps and the ability to walk on uneven surfaces.
TARSO AND MOVEMENTS OF THE ANKLE
Through the astragalus and calcaneus, the tarsus is a fundamental component for the correct function of the ankle.
In fact, thanks to the tarsus (and to the distal extremities of tibia and fibula), the ankle joint is able to perform those critical movements for locomotion, running, jumps etc; these movements are: dorsiflexion, plantarflexion, subversion and inversion.
- Dorsiflexion : it is the movement that allows you to lift your foot and walk on your heels.
- Plantarflexion : it is the movement that allows you to point your foot towards the floor. The human being performs a plantarflexion movement when he tries to walk on his toes.
- Eversion : means raising the side edge (ie the outer edge) of the foot, keeping the medial edge (ie the inner edge) on the floor.
- Inversion : it means raising the medial edge of the foot, keeping the side 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 most cases) or due to excessive stress (minority of cases).
Among the bones of the tarsus most subject to traumatic fractures are the talus and calcaneus.
Among the bones of the tarsus most subject to stress fractures are the navicular bone and the heel again.
ASTRAGALUS FRACTURE
Astragalus fractures 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, fractures of the neck of the talus are subsequent to 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. The moment they take place, this type of bone lesions can alter direct blood flow to the talus and result in episodes of osteonecrosis (or avascular necrosis ).
Taking into consideration the fractures of the body of the talus, these are usually the result of jumps carried out from an excessive height. In such circumstances, in fact, the body of the talo beats violently against the tibio-fibular mortar (see the brief review of the tibia and fibula), thus suffering a lesion.
FRACTURE OF THE CALCIUM
Typically, fractures of the calcaneus are the consequence of impacts that affect the heel and violently push the heel against the talus.
The main circumstances that cause a heel fracture are falls on the heels.
The fractures of the calcaneus are injuries that can give rise to various late complications, on all the arthritis against the subtalar joint and the strong pain during the movements of eversion and inversion of the foot.
STRESS FRACTURES
Stress fractures to the bones of the tarsus are often the consequence of mechanical stress on the bone or bone that develop the injury. Generally, they affect those who regularly practice sports such as running or jogging, as these individuals repeatedly overload the bones of the tarsus and the entire lower limbs.
TREATMENT OF A TARSO FRACTURE
Individuals who are victims of a traumatic tarsal fracture must wear plaster - clearly on the fractured foot - for at least 6 weeks and avoid giving weight to the limb with a fracture during this time.
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 of the tarsus.
