Tarsal bones
The foot contains seven tarsal bones. They serve to carry the weight and are divided into distal and proximal foot bones.
Inhaltsverzeichnis
Anatomy
The foot root (tarsus) lies between the lower leg and the metatarsus. It consists of seven individual bones. They are divided into the proximal and distal tarsal bones.
Proximal tarsal bones
Calcaneus
The calcaneus (heel bone) is the largest tarsal bone and the site of attachment for the Achilles tendon, the thickest and strongest tendon in the human body. The shape of the calcaneus is similar to a cuboid. There is a bony projection at the rear end, the calcaneal tuberosity (tuber calcanei). This forms the heel of the foot. On the underside of the calcaneal tuberosity there are two bone structures that are directed forward. These are the Proc. medialis tuberis calcanei and the Proc. lateralis tuberis calcanei. The Proc. anterior calcanei is located at the front of the calcaneus. The articular facies cuboidea is located on it. This is the articular surface that articulates with the cuboid bone. Medial to the calcaneus there is a bony protrusion, the Sustentaculum tali. On top of it is the Facies articularis talaris media. The upper side of the calcaneus also has two other joint surfaces, the facies articularis talaris anterior and the facies articulas talaris posterior. The sulcus calcanei is located between the facies articularis talaris media and the facies articularis talaris posterior. The tarsi sinus is a tunnel-shaped channel formed between the calcaneus and the talus by two bony depressions (calcaneus and tali sulcus). In this channel there are several ligaments which are important for the stability of the ankle joint.
Talus
The anklebone (talus) connects the foot with the leg. Its task is to transfer the forces generated by the body weight to the arch of the foot. It also forms the joint surface to the upper (Articulatio talocruralis) and lower ankle joint (Articulatio talotarsalis). It can be divided into two structures, the corpus tali and the ankle head (caput tali). On the upper side of the ankle bone there is a convex bone structure, the trochlea tali. Medial of this is the articular surface of the inner ankle (Facies malleolaris medialis). Lateral to this surface is a bony protrusion, the proc. posterior tali.
Lateral to the head of the ankle bone, the outer ankle is connected to the ankle bone via the lateral malleolar arteries. The proc. lateralis tali protrudes laterally from this surface. The joint surface for the scaphoid (Facies articularis navicularis) is located at the head of the ankle bone. The bone protrusion protruding backwards is called proc. posterior tali and is divided into two sections by the sulcus tendinis musculi flexoris hallucis longi. On the underside of the bone there are three joint surfaces, the facies articularis calcanea anterior, facies articularis calcanea media and facies articularis calcanea posterior. The articularis calcanea media and the articularis calcanea posterior are separated by the sulcus tali.
Distal tarsal bones
Os naviculare
The Os navicular (scaphoid) is a small bone that is located on the tibia side in the distal row of the tarsal. The bone is slightly arched and has a central elevation (Tuberositas ossis navicularis). Its diameter is only a few centimetres. Its shape is involved in the formation of the arch of the foot. The scaphoid has six sides. Via these the bone is connected to the three ossa cuneiformia (distal), the os cuboideum (distal) and the talus head (proximal). The surfaces are designated as follows: Facies anterior, posterior, superior, inferior, lateral and medial.
Os cuboideum
The cuboid bone (Os cuboideum) is located laterally in the distal tarsal row. It has a pyramidal or cube-like shape. The bone has the facies plantaris. This is characterized by a depression, the sulcus peronealis. The cuboid bone articulates with the calcaneus via the facies posterior. The facies anterior is divided into two halves by a bony structure. The medial half is connected to the Os metatarsal IV, the other to the Os metatarsale V. Furthermore, the facies lateralis and the facies medialis are located on the cuboid bone. The facies medialis is connected to the Os cuneiforme III.
Ossa cuneiformia The Ossa cuneiformia are three individual bones, Os cuneiforme laterale (lateral sphenoid bone), Os cuneiforme intermedium (intermedial sphenoid bone), Os cuneiforme mediale (medial sphenoid bone). The bones have a very small compact structure. Therefore they belong to the Ossa brevia (short bones).Due to the concise wedge shape of the Os cuneiforme intermedium and the Os cuneiforme laterale, the transverse arch of the foot is formed.
Function
The tarsal bones are involved in the formation of the ankle joint. Furthermore, they have a great load-bearing function. The majority of human weight rests on them when standing upright. Many muscles and tendons have their origin or attachment at the tarsal bones.
