Os cuneiform

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Cuneiform bones of man
Scheme of the human foot bones: The digits 4–6 denote the cuneiform bones.

As cuneiform (lat. For "sphenoid", plural cuneiform bones ) or Os tarsal three are bone denotes that part of the tarsus of the foot are. They lie between the navicular bone and the 1st to 3rd metatarsal bones .

Designations

The German term Keilbeine indicates the wedge shape of these bones, which can lead to confusion with the sphenoid bone of the skull ( Os sphenoidale ). The cuneiform bones are numbered 1 to 3 from the inner (medial) edge of the foot towards the outer (lateral) edge of the foot (→ metatarsal bones ). As an alternative to the numbering, the cuneiform bones can also be given the following names:

  • The first sphenoid bone is also known as the inner sphenoid bone, os cuneiforme mediale or os tarsale primum and is the largest of the three bones.
  • The second sphenoid bone is also known as the middle sphenoid bone, os cuneiforme intermedium or os tarsale secundum and is the smallest of the three bones.
  • The third sphenoid bone is also known as the outer sphenoid bone, os cuneiforme laterale or os tarsale tertium .

Articular surfaces

The forward (distal) sides of the sphenoid bones have articular surfaces for the 1st to 3rd metatarsal bones . The joints formed with the metatarsals are called tarsometatarsal joints ( Articulationes tarsometatarsales ) and are part of the Lisfranc joint line. To the rear (proximal) the sphenoid bones have articular surfaces for the scaphoid bone. The joints formed here are singly referred to as articulatio cuneonavicularis and numbered according to the cuneiform bones.

Cuneiform bones and transverse vaults

The sides of the cuneiform bones facing the dorsum of the foot ( dorsum pedis ) are wider than those facing the sole of the foot ( planta pedis ). This gives the cuneiform bones a wedge shape. Because of this shape, they form the transverse arch of the foot like the stones of a brick bridge arch. The wedge shape can also be found in the bases of the metatarsals.