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The fibula or calf bone is a leg bone on the lateral side of the
tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it conn ...
, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is small, placed toward the back of the
head of the tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connec ...
, below the knee joint and excluded from the formation of this joint. Its lower extremity inclines a little forward, so as to be on a plane anterior to that of the upper end; it projects below the tibia and forms the lateral part of the ankle joint.


Structure

The bone has the following components: * Lateral malleolus *
Interosseous membrane An interosseous membrane is a thick dense fibrous sheet of connective tissue that spans the space between two bones, forming a type of syndesmosis joint. Interosseous membranes in the human body: * Interosseous membrane of forearm * Interosseous ...
connecting the fibula to the tibia, forming a syndesmosis joint * The
superior tibiofibular articulation The proximal tibiofibular articulation (also called superior tibiofibular joint) is an arthrodial joint between the lateral condyle of the tibia and the head of the fibula. The contiguous surfaces of the bones present flat, oval facets cove ...
is an arthrodial joint between the lateral condyle of the tibia and the head of the fibula. * The inferior tibiofibular articulation (tibiofibular syndesmosis) is formed by the rough, convex surface of the medial side of the lower end of the fibula, and a rough concave surface on the lateral side of the tibia.


Blood supply

The blood supply is important for planning free tissue transfer because the fibula is commonly used to reconstruct the
mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
. The shaft is supplied in its middle third by a large nutrient vessel from the
fibular artery In anatomy, the fibular artery, also known as the peroneal artery, supplies blood to the lateral compartment of the leg. It arises from the tibial-fibular trunk. Structure The fibular artery arises from the bifurcation of tibial-fibular trunk int ...
. It is also perfused from its periosteum which receives many small branches from the fibular artery. The proximal head and the epiphysis are supplied by a branch of the anterior tibial artery. In harvesting the bone the middle third is always taken and the ends preserved (4 cm proximally and 6 cm distally)


Development

The fibula is ossified from ''three'' centers, one for the shaft, and one for either end. Ossification begins in the body about the eighth week of fetal life, and extends toward the extremities. At birth the ends are cartilaginous. Ossification commences in the lower end in the second year, and in the upper about the fourth year. The lower epiphysis, the first to ossify, unites with the body about the twentieth year; the upper epiphysis joins about the twenty-fifth year.


Head

The upper extremity or head of the fibula is of an irregular quadrate form, presenting above a flattened articular surface, directed upward, forward, and medialward, for articulation with a corresponding surface on the lateral condyle of the tibia. On the lateral side is a thick and rough prominence continued behind into a pointed eminence, the apex (''styloid process''), which projects upward from the posterior part of the head. The prominence, at its upper and lateral part, gives attachment to the tendon of the
biceps femoris The biceps femoris () is a muscle of the thigh located to the posterior, or back. As its name implies, it has two parts, one of which (the long head) forms part of the hamstrings muscle group. Structure It has two heads of origin: *the ''long ...
and to the fibular collateral ligament of the knee-joint, the ligament dividing the tendon into two parts. The remaining part of the circumference of the head is rough, for the attachment of muscles and ligaments. It presents in front a tubercle for the origin of the upper and anterior fibers of the peroneus longus, and a surface for the attachment of the anterior ligament of the head; and behind, another tubercle, for the attachment of the posterior ligament of the head and the origin of the upper fibers of the soleus.


Body

The body of the fibula presents four borders - the antero-lateral, the antero-medial, the postero-lateral, and the postero-medial; and four surfaces - anterior, posterior, medial, and lateral. ;Borders The antero-lateral border begins above in front of the head, runs vertically downward to a little below the middle of the bone, and then curving somewhat lateralward, bifurcates so as to embrace a triangular subcutaneous surface immediately above the lateral malleolus. This border gives attachment to an intermuscular septum, which separates the extensor muscles on the anterior surface of the leg from the peronaei longus and brevis on the lateral surface. The antero-medial border, or interosseous crest, is situated close to the medial side of the preceding, and runs nearly parallel with it in the upper third of its extent, but diverges from it in the lower two-thirds. It begins above just beneath the head of the bone (sometimes it is quite indistinct for about 2.5 cm. below the head), and ends at the apex of a rough triangular surface immediately above the articular facet of the lateral malleolus. It serves for the attachment of the
interosseous membrane An interosseous membrane is a thick dense fibrous sheet of connective tissue that spans the space between two bones, forming a type of syndesmosis joint. Interosseous membranes in the human body: * Interosseous membrane of forearm * Interosseous ...
, which separates the extensor muscles in front from the flexor muscles behind. The postero-lateral border is prominent; it begins above at the apex, and ends below in the posterior border of the lateral malleolus. It is directed lateralward above, backward in the middle of its course, backward, and a little medialward below, and gives attachment to an aponeurosis which separates the peronaei on the lateral surface from the flexor muscles on the posterior surface. The postero-medial border, sometimes called the oblique line, begins above at the medial side of the head, and ends by becoming continuous with the interosseous crest at the lower fourth of the bone. It is well-marked and prominent at the upper and middle parts of the bone. It gives attachment to an aponeurosis which separates the tibialis posterior from the soleus and flexor hallucis longus. ;Surfaces The anterior surface is the interval between the antero-lateral and antero-medial borders. It is extremely narrow and flat in the upper third of its extent; broader and grooved longitudinally in its lower third; it serves for the origin of three muscles: the
extensor digitorum longus The extensor digitorum longus is a pennate muscle, situated at the lateral part of the front of the leg. Origin and insertion It arises from the lateral condyle of the tibia; from the upper three-quarters of the anterior surface of the body of ...
, extensor hallucis longus, and
peroneus tertius In human anatomy, the fibularis tertius (also known as the peroneus tertius) is a muscle in the anterior compartment of the leg. It acts to tilt the sole of the foot away from the midline of the body ( eversion) and to pull the foot upward towar ...
. The posterior surface is the space included between the postero-lateral and the postero-medial borders; it is continuous below with the triangular area above the articular surface of the lateral malleolus; it is directed backward above, backward and medialward at its middle, directly medialward below. Its upper third is rough, for the origin of the soleus; its lower part presents a triangular surface, connected to the tibia by a strong interosseous ligament; the intervening part of the surface is covered by the fibers of origin of the flexor hallucis longus. Near the middle of this surface is the nutrient foramen, which is directed downward. The medial surface is the interval included between the antero-medial and the postero-medial borders. It is grooved for the origin of the tibialis posterior. The lateral surface is the space between the antero-lateral and postero-lateral borders. It is broad, and often deeply grooved; it is directed lateralward in the upper two-thirds of its course, backward in the lower third, where it is continuous with the posterior border of the lateral malleolus. This surface gives origin to the peronaei longus and brevis. File:Fibula - animation.gif, Position of fibula (shown in red) File:Human fibula.stl, 3D image File:Right fibula - close-up - animation.gif, Shape of fibula (right) File:Gray263.png, Diagram which depicts ossification of human fibula. File:Gray262.png, Lower extremity of right fibula. Medial aspect. File:Slide5CEC4.JPG, Ankle joint. Deep dissection. File:Slide1besa.JPG, Knee and tibiofibular joint. Deep dissection. Anterior view. File:Fibula Anatomy by Jason Christian.webm, Fibula Anatomy


Function

The fibula does not carry any significant load (weight) of the body. It extends past the lower end of the tibia and forms the outer part of the ankle providing stability to this joint. It has grooves for certain ligaments which gives them leverage and multiplies the muscle force. It provides attachment points for the following muscles:


Clinical significance


Fractures

The most common type of fibula fracture is located at the distal end of the bone, and is classified as ankle fracture. In the Danis–Weber classification it has three categories: *Type A: Fracture of the lateral malleolus, distal to the syndesmosis (the connection between the distal ends of the tibia and fibula). *Type B: Fracture of the fibula at the level of the syndesmosis *Type C: Fracture of the fibula
proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...
to the syndesmosis. A Maisonneuve fracture is a
spiral fracture A spiral fracture (a.k.a. torsion fracture) is a bone fracture occurring when torque (a rotating force) is applied along the axis of a bone. Spiral fractures often occur when the body is in motion while one extremity is planted. For example, a s ...
of the proximal third of the fibula associated with a tear of the distal
tibiofibular syndesmosis In anatomy, fibrous joints are joints connected by fibrous tissue, consisting mainly of collagen. These are fixed joints where bones are united by a layer of white fibrous tissue of varying thickness. In the skull the joints between the bones a ...
and the
interosseous membrane An interosseous membrane is a thick dense fibrous sheet of connective tissue that spans the space between two bones, forming a type of syndesmosis joint. Interosseous membranes in the human body: * Interosseous membrane of forearm * Interosseous ...
. There is an associated fracture of the medial malleolus or rupture of the deep
deltoid ligament The deltoid ligament (or medial ligament of talocrural joint) is a strong, flat, triangular band, attached, above, to the apex and anterior and posterior borders of the medial malleolus. The deltoid ligament is composed of 4 fibers: 1. Anterior ti ...
. An
avulsion fracture An avulsion fracture is a bone fracture which occurs when a fragment of bone tears away from the main mass of bone as a result of physical trauma. This can occur at the ligament by the application of forces external to the body (such as a fall ...
of the head of the fibula refers to the fracture of the fibular head because of a sudden contraction of the biceps femoris muscle that pulls its site of attachment on the bone. The attachment of the biceps femoris tendon on the fibular head is closely related to the lateral collateral ligament of the knee. Therefore, this ligament is prone to injury in this type of avulsion fracture.


History


Etymology

The word '' fibula'' can be dated back to c. 1670 to describe a clasp or brooch – see fibula (brooch) – and was first used in English for the smaller bone in the lower leg c. 1706. It derives from Latin ''fībula,'' also meaning a clasp or brooch. The bone was so called because it resembles a clasp like a modern safety pin.etymonline.com
/ref> The adjective peroneal referring to the fibula bone or its surrounding structures derives from : perónē, the Ancient Greek word for a clasp.


Other animals

Because the fibula bears relatively little weight in comparison with the tibia, it is typically narrower in all but the most primitive tetrapods. In many animals, it still articulates with the posterior part of the lower extremity of the
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates ...
, but this feature is frequently lost (as it is in humans). In some animals, the reduction of the fibula has proceeded even further than it has in humans, with the loss of the tarsal articulation, and, in extreme cases (such as the horse), partial fusion with the tibia.


See also

* Peroneal * Fibular hemimelia — congenital absence or shortening of the fibula


References


External links

* {{Authority control Bones of the lower limb Long bones