What are metatarsal bones?
The five long bones of the metatarsus of the foot are known as the metatarsals. Just as metacarpals of the hand are made of different components, similarly, metatarsals are made of different components such as a proximal base, shaft, and distal head. Arches of the foot are formed by the metatarsal along with the tarsal. This is important for weight-bearing and for walking purposes.
The bones of the foot are known as metatarsal bones. They are located between the heel and the toes. Metatarsus is referred to as the group of five long cylindrical bones. These bones are not named individually but from inside to outside they are numbered. The innermost bone is the first one that is related to the big toe. After which are the second, third, fourth and the fifth metatarsal. The ligaments and the bones are attached to each other thus forming an arch. During walking, the weight of the body is supported and transferred by these bones.
The bone is divided into three parts anatomically, that is the base, head, and bone of the body. The posterior wedge-shaped part is known as the base which is present at the end of the metatarsal bone. From behind the ankle bone and the base of the metatarsal attach to each other while it joins with the other bones at the side.
The base is extended to the head by the part of the metatarsal known as the body. Towards the base, this body is much wider. The front end of the metatarsal bone is known as the head and it faces the toes. The front end joins the phalanges. A football player's fracture of the metatarsal is very common since the foot is not properly protected by the faulty design of the footwear.
Stress fractures also occur in the metatarsal. This is also known as March fractures. Usually, after long marches, this has been commonly observed in soldiers. From medial to lateral side the five metatarsal bones have been numbered.
Each long bone is miniature and described as:
- Base - the proximal end of the metatarsal bone is known as the base and with the tarsal bone is articulates. In such a way it is set obliquely that backward and laterally it is projected.
- Shaft - dorsally the shaft is convex and ventrally the shaft is concave. It is prismoid shaped and from the base to the head, it tapers. From the shaft originates the interossei.
- Head - the distal end of the metatarsal is known as the head. From the sides it is flat. In order to form metatarsophalangeal joint articulation takes place between the head of the metatarsal with the phalanx.
The anatomical head is a constriction that is present at the proximal part of the head. Surgical neck is another constriction that is present proximal to the shaft. Studies have found that metatarsal bone anatomy is the same on the left and right side.
First metatarsal bone
It is short, thick and strong. It has been designed so that it can transmit body weight. There is a kidney-shaped facet at the proximal surface of the base. Outwards this facet is concave. The articulation takes place between the first metatarsal and the medial cuneiform. Also, to some extent, articulation also takes place with the intermediate cuneiform and with respective phalanx it articulates on the distal side.
In order to receive the tarsometatarsal ligaments, there is a groove on the circumference of the kidney-shaped facet. Medially the base is attached to the tibialis anterior tendon. Usually, on the sides, there is no articular facet but to articulate with the second metatarsal an oval facet may be present.
For the insertion of peroneus longus on the plantar surface, a rough oval prominence is present. There is a well-marked prismoid form on the body of the bone. On the plantar surface, there is a large head and two grooved facets.
An elevation separates these both structures so that with the sesamoid bone it can articulate. There are two grooved facets on the plantar surface and they are separated by a smooth elevation.
Second metatarsal bone
The longest metatarsal bone is the second bone whose base wedge is shaped. The three cuneiform bones form a recess in which this base projects backward and is held. For the medial cuneiform, there is a dorsal facet on the medial side of the base which articulates with the cuneiform bone, third metatarsal, and the first metatarsal bone.
Above it has a broad base and below it is rough and narrow. There are four articulate surfaces present: the base posteriorly articulates with the intermediate cuneiform bone. On the upper part with the medial cuneiform, the facet articulates.
Upper and lower facets are present on the lateral aspect of the base and a rough non-articular interval separates them, the lateral articular surfaces are separated into two by a vertical ridge. The articulation takes place between the third metatarsal and the anterior one and articulation takes place between the lateral cuneiform and the posterior ones.
For articulation with the first metatarsal, there is a fifth facet present that has an oval shape, near the base on the medial side of the body this is located. For the lisfranc joint, the second metatarsal acts as a keystone. It is like a final piece and it allows the arch it bears weight.
Third metatarsal bone
The long bone is the foot is known as the third metatarsal and it is the second-longest bone that has a wedge-shaped base. Proximally articulation takes place between the third metatarsal and the third cuneiform. Medially articulation takes place with the second metatarsal by two facets.
For the fourth metatarsal, a single facet is present. At the dorsal angle of the base, this last facet is located. With the third proximal phalanx and the head, articulation takes place.
Fourth metatarsal bone
This is the third metatarsal bone and is smaller in size. It has a wedge-shaped base and for articulation, with the cuboid, it has a quadrangular surface. There is one dorsal face on the lateral side for the fifth metatarsal bone. Dorsally there is one facet on the base on the medial side.
This facet is divided into two parts proximal part and distal part. The proximal part is for the lateral cuneiform and the distal part is for the third metatarsal bone. The articulation takes place between the head and the fourth proximal phalanx.
Fifth metatarsal bone
This is a long bone in the foot. Of the five metatarsal bones, this is the second smallest bone. There is a large tuberosity or styloid process present on the fifth metatarsal bone. On the lateral side and backside, it has projections. In a transverse direction, the triangular surface is cut obliquely so that the base can articulate.
For the fourth metatarsal bone, there is one facet on the medial side of the base. The tendon of the abductor digit minimi forms a groove on the plantar surface of the base.
The articulation takes place between the head and the fifth proximal phalanx. The projecting part of the tuberosity and the lateral process of the tuberosity are connected by a strong band of the plantar aponeurosis.
Studies have found that morphometric measurements of metatarsals in themselves are the same and there is no significant difference.
Attachments of metatarsal bones
First metatarsal bone
On the medial side of the base of the first metatarsal bone is inserted a part of the tibialis anterior.
At the inferior angle of the lateral surface of the base of the first metatarsal bone is inserted the greater part of the peroneus longus.
From the medial side of the bone originates the lateral part of the first dorsal interossei muscle. Spreading the toes is the function of the muscle.
Second metatarsal bone
The second metatarsal bone attaches the first and the second dorsal interossei muscle.
From the medial side of the bone originates the first dorsal interossei and from the lateral side originates the second dorsal interossei. Spreading the toes is the main function of the dorsal interossei.
From the lateral side of the metatarsophalangeal joint originates the horizontal head of the adductor halluccis. Even from the deep transverse metatarsal ligament, it originates.
Third metatarsal bone
The third metatarsal bone originates from the second and third interossei muscles. From the medial side, the second one originates and from the lateral side, the third one originates.
Fourth metatarsal bone
From the fourth metatarsal bone originates the third and the fourth dorsal interossei muscle. From the medial side originates the third dorsal interossei and from the lateral side originates the fourth dorsal interossei.
From the medial side of the base and the shaft of the fourth metatarsal originates the second plantar interossei muscle.
From the lateral side of the metacarpophalangeal joint originates the horizontal head of the adductor hallucis.
Fifth metatarsal bone
On the dorsal surface of the tuberosity of the fifth metatarsal bone is inserted the peroneus Brevis.
On the medial part of the dorsal surface of the base and the shaft of the fifth metatarsal bone is the peroneus Tertius that is inserted.
From the plantar surface of the base of the fifth metatarsal bone arises the flexor digito Minimi Brevis.
From the medial side of the shaft originates the fourth dorsal interossei muscle.
From the medial side of the base and the shaft of the fifth metatarsal is the third plantar interossei muscle. Moving the fourth toe medially and moving the toes together is the main function of this muscle.
From the deep transverse metatarsal ligament arises the horizontal head of the adductor hallucis
Joints
- Tarsometatarsal joint - This joint is formed by the ankle with the toes. The proximal base of the metatarsal will connect with the tarsal bone such as the cuboid or the cuneiform bone to form the tarsometatarsal joint.
- Metatarsophalangeal joints - articulation takes place between the distal head and corresponding phalanx. Also, articulation takes place between the sesamoid bone present on the plantar surface and the head of the metatarsal bones.
- Intermetatarsal joint - this joint is formed by the articulation between the bases of the metatarsal with each other. Articular facets are the smooth area present on the metatarsal which articulates with the other bones. From the medial side of the base and the shaft of the third metatarsal originates the first plantar interossei. Moving the third toe medially and moving the toes together is the main function of the muscles. From the lateral side of the metacarpophalangeal joint originates the horizontal head of the adductor hallucis.
Ossification of the bones
One primary center and one secondary center ossifies each metatarsal bone.
- Primary center - in the first metatarsal during the tenth week of the fetal life in the shaft it appears. In the rest of the metatarsal, it appears during the ninth week of fetal life.
- Secondary centers - during the third year the base of the metatarsal appears. During the third and the fourth year, another metatarsal appears. For the tuberosity of the fifth metatarsal bone, a separate center may be present. By the seventeenth and twentieth year union takes place between the shaft and the secondary center.
Function
Supporting the weight of the body is the main function of the metatarsal that they do along with the calcaneus. There are five main points of contact with the ground that the metatarsal has. These are as follows:
- The two sesamoid bones and the first metatarsal head
- The second metatarsal head
- The head of the third metatarsal bone
- The head of the fourth metatarsal bone
- The head of the fifth metatarsal bone
Since the first metatarsal bone is the strongest and thickest of all the metatarsals hence it supports the majority of the weight. The second to fifth metatarsal bones provide balance and comfort to the first metatarsal bone so that it can support the load.
Metatarsal can be affected by fracture which is not quite common but can occur when over the foot any heavy object rolls or falls over.
