General information
The metatarsus consists of five metatarsal bones (Os metatarsalia I – V), which are connected by joints. They are located in the foot between the toes and the root of the foot. Together with the respective toes, each metatarsal forms a beam, which divides the entire foot into five beams. The first ray is formed by the big toe and the corresponding metatarsal bone, the fifth ray is formed by the little toe and the metatarsal bone.
Structure
The metatarsus consists mainly of the five metatarsal bones, which all have the same basic structure. Each metatarsal consists of a base, a body (corpus) and a head (caput, metatarsal head). In the area of the base of the first metatarsal there is a bony extension.
This is called Tuberositas ossis metatarsalis I. This is where the anterior tibial muscle comes in, which can lift the foot and rotate it inwards. There is also an extension in the area of the fifth metatarsal bone, the Tuberositas ossis metatarsalis V. This serves as an attachment for the musculus peronaeus brevis, which can bend the foot and turn it outwards.
The bases as well as the heads of the individual bones have joint surfaces, allowing the metatarsal bones to interact with the adjacent bony structures. The heads form a convex joint surface and interact with the adjacent metatarsals. They thus form the five metatarsophalangeal joints.
The bases of the metatarsals are rather flat and are in contact with the tarsal. The bases of the first to third metatarsals articulate with the three ossa cuneiformia (sphenoid bones), the bases of the fourth and fifth metatarsal articulate with the cuboid bone. The Lisfranc joint line is formed between the tarsal and the bases of the metatarsals.
In addition, the individual bases of the metatarsals are in contact with each other and form the intermetatarsal joints. Two sesamoid bones are located in the area of the metatarsophalangeal joint of the big toe. These are embedded in the tendons and the capsule-ligament apparatus.
The abductor hallucis muscle and part of the flexor hallucis brevis muscle are attached to the middle sesamoid bone. Both muscles serve to bend the big toe and to maintain the longitudinal arch of the foot, the abductor also serves to brace the big toe. The adductor hallucis muscle is attached to the lateral sesamoid bone.
This muscle maintains the transverse arch of the foot and can attach the big toe to the foot. In addition, the second part of the muscle flexor hallucis brevis attaches to this sesamoid bone and bends the big toe in the base joint. As part of the entire foot, the metatarsus is involved in building and maintaining the longitudinal and transverse arch.
In addition, the individual metatarsal bones can be shifted against each other and thus allow the foot to rotate both internally and externally, allowing it to adapt to uneven surfaces when walking. In addition, the metatarsal bones are the starting point of various muscles, which allows flexion and extension of the entire foot and the movements of the big toe. In the case of a hallux valgus or a splayfoot, there are changes in the position of the metatarsal bones.
The metatarsal bones can break if a direct force is applied to the foot from the front. In addition to this injury pattern, the metatarsals can also break under constant stress on the metatarsus. This type of fracture is called fatigue fracture.
The metatarsus consists of five bones, Ossa metatarsalia I- V, which have various articulated connections to the adjacent bones of the foot. This ensures the mobility of the foot and the adaptation to uneven ground when walking. In addition, various muscles attach to the bones of the metatarsus, which ensure both the mobility and the tension and posture of the longitudinal and transverse arch.
The very common malpositioning of the big toe (hallux valgus) is caused by a malpositioning of the metatarsal bones, as is the splayfoot. Fractures are also possible in the metatarsus, which can lead to a fracture due to the direct application of force or constant stress.