There are seven tarsal bones. Proximal row is formed by talus above, and the calcaneus below. The distal row contains, from medial to lateral side, medial cuneiform, the intermediate cuneiform, the lateral cuneiform and the cuboid.
Each tarsal bone is roughly cuboidal in shape, having six surfaces.
Calcaneus and talus tarsal bones are discussed individually.
It is cuboidal in shape but has a broader base oriented medially
Structure of Cuboid Bone
- The dorsal surface is rough for the attachment of ligaments. It is directed upwards and laterally.The dorsal cuboidal surface, upward and lateralward, is rough, for the attachment of ligaments.
- The plantar surface is crossed anteriorly by an oblique groove. The groove is bounded posteriorly by a prominent ridge. The groove is called the peroneal sulcus and it runs obliquely anteromedially. It lodges the tendon of the peroneus longus.The ridge ends laterally in an eminence, the tuberosity which presents an oval facet for gliding of sesamoid bone or cartilage frequently found in the tendon of the peroneus longus.
- The lateral surface is short and notched.
- The medial surface is extensive, being partly articular and partly nonarticular. An oval facet in the middle articulates with the lateral cuneiform bone. Proximal to this a small facet may be present for the navicular bone. It is rough in the rest of its extent, for the attachment of strong interosseous ligaments.
- The proximal or posterior surface is concavoconvex for articulation with the anterior surface of calcaneum. Its inferomedial angle projects backward as a process, which underlies and supports the anterior end of the calcaneus.
- The distal surface is triangular and also articular. It is divided by a vertical ridge into two areas. The medial, quadrilateral in form, articulates with the fourth
The cuboid articulates with
- Third cuneiform
- Fourth metatarsal
- Fifth metatarsal. It occasionally articulates with a fifth, the navicular.
Attachments on Cuboid
- The notch on the lateral surface, and the groove on the plantar surfaces, are occupied by the tendon of the peroneus longus .The ridge posterior to the groove gives attachment to the deep fibers of the long plantar ligament. Rough surface behind the groove gives attachment to plantar calcaneocuboid ligament, few fibers of the flexor hallucis brevis, and a fasciculus from the tendon of the tibialis posterior.
- The short plantar ligament is attached to the posterior border of the plantar surface. The posteromedial part of the plantar surface provides
- Insertion to a slip from the tibials posterior
- Origin to the flexor hallucis brevis.
- The nonarticular part of the medial surface provides attachment to ligaments, including the lateral limb of the bifurcate ligament.
Ossification of Cuboid
The cuboid bone ossifies from one centre which appears just before birth.
It forms the uppermost portion of the medial longitudinal arch of the foot and acts as a keystone of the arch.
The navicular bone has 6 surfaces.
- The posterior or proximal navicular surface is oval, concave, broader laterally than medially, and articulates with the rounded head of the talus.
- The medial surface has a blunt and prominent tuberosity, directed downwards. The tuberosity is separted from the plantar surface by a groove.
- The anterior surface is convex, and is divided into 3 facets for the three cuneiform bones.
- The dorsal surface is convex from side to side, and rough for the attachment of ligaments
- The plantar surface is irregular, and also rough for the attachment of ligaments.
- The lateral surface is rough and irregular for the attachment of ligaments and occasionally presents a small facet for articulation with the cuboid bone.
Attachments on Navicular
- Tibialis posterior attaches at the tuberosity of the navicular bone The groove below the tubrosity transmits a part of the tendon of this muscle to other bones.
- The plantar surface provides attachment to the spring ligament.
- The calcaneonavicular part of the bifurcate ligament is attached to the lateral surface.
- Talonavicular, cuneonavicular and cubonavicular ligaments attach to the dorsal surface
Ossification of navicular
Navicular ossifies from one centre which appears during the third year of life.
Articulations of Navicular
Cuneiforms are wedge shaped bones. In the medial cuneiform, the edge of the wedge forms the dorsal surface. In the intermediate and lateral cuneiforms, the thin edge of the wedge forms the plantar surface.
See the image below
- The medial surface is broad, quadrilateral and subcutaneous. Except for its anterior inferior edge which carries a smooth oval impression [for part of tibialis anterior tendon], this surface is rough.
- The lateral surface is marked by an inverted L-shaped facet along the posterior and superior margins for the intermediate cuneiform bone. The anterosuperior part of the facet is separated by a vertical ridge which creates an anterior area for articulation with the base of the second metatarsal bone.The anteroinferior part of the lateral surface is rough for the attachment of ligaments and part of the tendon of the peroneus longus.
- The anterior surface is convex and is much larger than the posterior surface. It articulates with the first metatarsal bone.
- The posterior surface is triangular, concave, and articulates with the most medial and largest of the 3 facets on the anterior surface of the navicular. [piriform facet].
- The plantar surface is formed by the base of the wedge. It is rough posterior part has a tuberosity for the insertion of fibers of the tendon of the tibialis posterior. Anterior part provides insertion to part of the tendon of the tibialis anterior.
- The dorsal surface is the narrow end of the wedge and is directed upward and lateralward. It is rough for the attachment of ligaments.
The first cuneiform articulates with
- Second cuneiform
- First metatarsal
- Second metatarsal.
Attachments of Cuneiform
- The greater part of the tibialis anterior is inserted into an impression on the anteroinferior angel of the medial surface.
- The plantar surface receives a slip from the tibialis posterior.
- A part of the peroneus longus is inserted into the rough antroinferior part of the lateral surface.
- The anterior surface is triangular and narrower than the posterior. It articulates with the base of the second metatarsal bone.
- The posterior surface is also triangular. It articulates with the middle facet on the anterior surface of the navicular.
- The medial surface carries an L-shaped articular facet, along the superior and posterior borders, for articulation with the medial cuneiform. Rest of medial surface is rough for the attachment of ligaments.
The rough dorsal surface forms the base of the wedge.
The plantar surface is sharp and tuberculated. It is also rough for the attachment of ligaments and for the insertion of a slip from the tendon of the tibialis posterior.
- First cuneiform
- Third cuneiform
- Second metatarsal.
The plantar surface receives a slip from the tibialis posterior.
The dorsal surface is oblong and formed by the base of the wedge. Its posterolateral angle prolong backward
- The plantar surface is formed by the edge of the wedge, has a rounded margin and serves for the attachment of part of the tendon of the tibialis posterior, part of the flexor hallucis brevis, and ligaments.
- Posterior or proximal surface is rough in its lower one third, and has a triangular facet in its upper two thirds for the navicular bone.
- The lateral surface is marked in its posterosuperior part by a triangular or oval facet for the cuboid. At the anteroinferior angel, a small facet may be present for the fourth metatarsal bone.
- The anterior surface bears triangular articular facet and articulates with the third metatarsal bone. the rough, nonarticular area serves for the attachment of an interosseous ligament. The 3 facets for articulation with the 3 metatarsal bones are continuous with one another; those facets for articulation with the second cuneiform and navicular are also continuous, but the facet for articulation with the cuboid is usually separate.
- The medial surface is marked along its posterior margin by a vertical strip indented in the middle, for articulation with the intermediate cuneiform bone. Along the anterior margin of the surface there is a facet, sometimes divided, for the base of the second metatarsal bone.
The third cuneiform articulates with
- Intermdiate or middle cuneiform
- Second, third, and fourth metatarsals.
The plantar surface receives a slip from the tibialis posterior, and may give origin to the flexor hallucis brevis.
Ossification of Cuneiforms
Each cuneiform bone ossifies from one centre, which appears
- Lateral cuneiform – first year in the lateral cuneiform
- Medial cuneiform – second year
- Intermediate cuneiform – third year
Here is a video, just to give you an idea about structural arrangement of tarsal bones
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