Metatarsus

The metatarsal - Latin metatarsals (plural ) or metatarsal ( singular) - are located in the foot between the tarsus and the toes. Humans have five metatarsals, which are numbered from the inside ( medial) to the outside ( lateral) with the numbers 1 to 5 at each distance. Thus, the metatarsal bone, which runs on the inner edge of the foot of the tarsus to the big toe, called the first metatarsal bone. Along with the big toe is the first metatarsal to the so-called first beam. All other corresponding form metatarsal with the toes the subsequent second, third, fourth and fifth beam.

Construction

The metatarsal bones have the following ingredients:

• Base
• Body (corpus )
• Head ( metatarsal head, caput)

In the area of ​​the base of the first metatarsal there is an extension, called a tuberosity of metatarsal I. This extension serves the tibialis anterior muscle as a approach. In the area of the base of the fifth metatarsal, there is also an extension called a tuberosity of metatarsal V. This extension serves the musculus peroneus brevis as an approach.

Joint surfaces

The articular surfaces of the head are convex and, together with the adjoining toe links the metatarsophalangeal joints.

The joint surfaces of the bases are formed more or less flat. They stand with the tarsus in contact and form the Lisfranc joint line ( articulationes tarsometatarseae ). The bases of the first to third metatarsal bones in each case form a hinge with the first to third cuneiform. The bases of the fourth and fifth metatarsals with the cuboid are connected.

The bases of the metatarsal bones are in the Tarsometatarsalgelenken ( articulationes tarsometatarsales ) articulated in conjunction with the cuneiform bones and the cuboid bone. They also have contact with each other. There are joint surfaces forming the Intermetatarsalgelenke ( articulationes intermetatarseae ). There are small furrows in which the sesamoid bones of the big toe are on the underside of the head of the first metatarsal.

Supination, pronation

The metatarsal bones can move slightly in a fan shape against one another and thereby enable mobility in the forefoot, which is called supination and pronation. Thus the forefoot to be able to adapt when walking on uneven surfaces.

Proportions

The first metatarsal is the shortest and strongest bone at the same time with the largest cross section. The large cross-section is required, because when walking the unwinding takes place predominantly over the big toe, and thus on the first beam. The second metatarsal bone is the longest metatarsal. The length of the subsequent metatarsal takes to the lateral border back from continuously.

Other common characteristics

For all metatarsals are long bones. The bases are designed wider towards the back of the feet as the feet. This results in an approximate wedge shape, which also form the transverse arch of the foot as in the cuneiform bones ( cuneiform ).

Fractures and diseases

In diseases such as bunions and flat feet are changes still in a position of the metatarsal bones.

For direct blows to the forefoot, the metatarsal bones can break. Also possible are called stress fractures, ie, fractures that do not come about by a sudden force (accident or otherwise), but due to fatigue of the bone material are ( march fracture). The fracture of the fifth metatarsal to the proximal Diaphysenende is called Jones fracture. Without been clarified, it may also cause an aseptic necrosis of bone (bone infarction ) of a metatarsal head, usually the second coming ( Kohler's Disease - Freiberg ).