Fibula

The fibula (plural: fibulae) is the smaller bone of the leg and contributes to the knee and ankle joints but is not weightbearing. The distal fibula (i.e. lateral malleolus) is the only part that is required for normal lower limb function, which allows plastic surgeons the remove large segments of it.

Gross anatomy

Osteology

The thin long 'lesser' bone of the leg runs posterolateral to the tibia and has a head (proximal), neck, shaft and distal end known as the lateral malleolus:

• the head has a small superiorly pointed tubercle, the apex or styloid process, and an articular surface for the tibia
• the neck is immediately inferior to the head
• the shaft is triangular in cross section and has a sharp medial crest that runs longitudinally down the shaft and serves as an attachment for the broad strong interosseous membrane
• the lateral malleolus contains a facet medially, to articulate with the talus

It is the most slender of all the long bones.

Articulations

Proximal

• proximal tibiofibular joint

Distal

• distal tibiofibular syndesmosis
• talocrural joint

Attachments

Musculotendinous

Proximal

• biceps femoris: head and styloid process
• peroneus longus: head
• soleus: posterior head

Shaft

• interosseous membrane
• peroneus longus: lateral upper shaft
• peroneus brevis: lateral upper shaft
• peroneus tertius: anterior shaft
• extensor hallucis longus: anterior shaft
• extensor digitorum longus: anterior shaft
• soleus: posterior upper shaft
• tibialis posterior: posterior upper shaft
• flexor hallucis longus: lower and mid posterior shaft

Ligamentous

Proximal

• proximal tibiofibular joint

Distal

• distal tibiofibular syndesmosis
  • anterior tibiofibular ligament
  • posterior tibiofibular ligament 
• talocrural joint
  • anterior talofibular ligament (ATFL)
  • posterior talofibular ligament (PTFL)
  • calcaneofibular ligament

Relations

The tendons of peroneus longus and brevis pass behind the lateral malleolus whereas the tendon of peroneus tertius passes in front of it.

Blood supply

Branches of the fibular artery give off one or more large nutrient arteries that enter the shaft of the fibula. These branches are important for the harvest of the fibular shaft for plastic surgical reconstruction (free fibular graft, usually for mandibular reconstruction).

Branches of the anterior tibial artery supply the head.

Variant anatomy

• fibular hemimelia

Radiographic features

Plain film

It is important to understand the 3-dimensional orientation of the lateral malleolus within the ankle. The lateral malleolus is longer, larger and more posterior than the medial malleolus. Hence on a true lateral radiograph of the ankle, it is posterior to the medial malleolus.

Development

Ossification

content pending

Related investigations

Plain film

• knee series
• tibia/fibula series
• ankle series

Cross-sectional imaging

• leg CT
• leg CTA (for fibular free graft workup)
• leg MRI

Related pathology

• ankle fractures
  • Weber classification
  • Lauge-Hansen classification
• Maisonneuve fracture