Fibula

For the ancient jewelry type, seeFibula (brooch).

Thefibula(pl.:fibulaeorfibulas) orcalf boneis alegboneon thelateralside of thetibia,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 thehead of the tibia,below theknee jointand 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 theankle joint.

Fibula
Position of fibula in human body (shown in red)
Cross section of human lower leg, showing fibula in centre (latin terminology)
Details
Pronunciation	/ˈfɪbjʊlə/
Articulations	Superiorandinferior tibiofibular joint Ankle
Identifiers
Latin	(os) fibula
MeSH	D005360
TA98	A02.5.07.001
TA2	1427
FMA	24479
Anatomical terms of bone

3D medical animation still shot of fibula structure

Structure

The bone has the following components:

• Lateral malleolus
• Interosseous membraneconnecting the fibula to the tibia, forming asyndesmosisjoint
• Thesuperior tibiofibular articulationis anarthrodialjointbetween thelateral condyleof the tibia and the head of the fibula.
• Theinferior 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 planningfree tissue transferbecause the fibula is commonly used to reconstruct themandible.The shaft is supplied in its middle third by a large nutrient vessel from thefibular artery.It is also perfused from itsperiosteumwhich receives many small branches from the fibular artery. The proximal head and theepiphysisare 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 isossifiedfromthreecenters, one for the shaft, and one for either end. Ossification begins in the body about the eighth week offetal life,and extends toward the extremities. At birth the ends arecartilaginous.

Ossification commences in the lower end in the second year, and in the upper about the fourth year. The lowerepiphysis,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 orhead of the fibulais of an irregular quadrate form, presenting above a flattened articular surface, directed upward, forward, and medialward, for articulation with a corresponding surface on thelateral condyle of the tibia. On the lateral side is a thick and rough prominence continued behind into a pointed eminence, the apex (styloidprocess), which projects upward from the posterior part of the head.

The prominence, at its upper and lateral part, gives attachment to thetendonof thebiceps femorisand to the fibular collateral ligament of the knee-joint, theligamentdividing the tendon into two parts.

The remaining part of the circumference of the head is rough, for the attachment ofmusclesand ligaments. It presents in front atuberclefor the origin of the upper and anterior fibers of theperoneus 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 thesoleus.

Body

Thebody of the fibulapresents four borders - the antero-lateral, the antero-medial, the postero-lateral, and the postero-medial; and four surfaces - anterior, posterior, medial, and lateral.

Borders

Theantero-lateral borderbegins 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.

Theantero-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 theinterosseous membrane,which separates the extensor muscles in front from the flexor muscles behind.

Thepostero-lateral borderis 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.

Thepostero-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

Theanterior surfaceis 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: theextensor digitorum longus,extensor hallucis longus,andperoneus tertius.

Theposterior surfaceis 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.

Themedial surfaceis the interval included between the antero-medial and the postero-medial borders. It is grooved for the origin of the tibialis posterior.

Thelateral surfaceis 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.

• 
  Position of fibula (shown in red)
• 
  3D image
• 
  Shape of fibula (right)
• 
  Diagram which depictsossificationof human fibula.
• 
  Lower extremity of right fibula. Medial aspect.
• 
  Ankle joint. Deep dissection.
• 
  Knee and tibiofibular joint. Deep dissection. Anterior view.
• 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:

Muscle attachments (seen from the front)

Muscle attachments (seen from the back)

Muscle	Direction	Attachment
Biceps femoris muscle	Insertion	Head of fibula
Extensor hallucis longus muscle	Origin	Medial side of fibula
Extensor digitorum longus muscle	Origin	Proximal part of the medial side of fibula
Fibularis tertius	Origin	Distal part of the medial side of fibula
Fibularis longus	Origin	Headand the lateral side of fibula
Fibularis brevis	Origin	Distal 2/3 of the lateral side of fibula
Soleus muscle	Origin	Proximal 1/3 of the posterior side of fibula
Tibialis posterior muscle	Origin	Lateral part of the posterior side of fibula
Flexor hallucis longus muscle	Origin	Posterior side of fibula

Clinical significance

As much of the fibula can be removed without it impacting an individual's ability to walk, the fibula is utilised as a source of bone material in fibularfree flapsurgeries.

Fractures

The most common type of fibula fracture is located at the distal end of the bone, and is classified asankle fracture.In theDanis–Weber classificationit has three categories:

• Type A:Fracture of thelateral malleolus,distalto 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 fibulaproximalto the syndesmosis.

AMaisonneuve fractureis aspiral fractureof the proximal third of the fibula associated with a tear of the distaltibiofibular syndesmosisand theinterosseous membrane.There is an associated fracture of the medialmalleolusor rupture of the deepdeltoid ligament.

Anavulsion fractureof thehead of the fibularefers to thefractureof the fibular head because of a sudden contraction of thebiceps femoris musclethat pulls its site of attachment on the bone. The attachment of the biceps femoris tendon on the fibular head is closely related to thelateral collateral ligamentof the knee. Therefore, this ligament is prone to injury in this type of avulsion fracture.

History

Etymology

The wordfibulacan be dated back to c. 1670. It derives from Latinfībula,which describes a clasp or brooch – seefibula (brooch)– and was first used in English for the smaller bone in the lower leg c. 1706. The bone was so called because it resembles a clasp like a modern safety pin.

The adjectiveperonealreferring to the fibula bone or its surrounding structures derives fromπερόνη: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 thefemur,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 thehorse), partial fusion with the tibia.

See also

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

References

This article incorporates text in thepublic domainfrompage 260of the 20th edition ofGray's Anatomy(1918)

External links

• Anatomy photo:17:st-1402at the SUNY Downstate Medical Center