The fibula is one of the two long bones in the lower leg, alongside the tibia. It is the smaller and thinner of the two and primarily provides structural support and stability to the lower leg. The fibula does not bear significant weight but serves as an attachment site for muscles and ligaments. It extends from the knee to the ankle and is connected to the tibia through the proximal and distal tibiofibular joints, as well as an interosseous membrane.
Location
The fibula is located in the lateral part of the lower leg, running parallel to the tibia. It extends from its proximal end near the lateral condyle of the tibia down to its distal end, forming part of the lateral aspect of the ankle joint.
Structure and Anatomy
The fibula is a slender, long bone located on the lateral side of the lower leg. It runs parallel to the tibia and is composed of three main sections: the proximal end, shaft, and distal end.
Proximal End
Fibular Head
- Shape and Position: Rounded and slightly enlarged, forming the proximal end of the fibula.
- Articulations: Articulates with the lateral condyle of the tibia at the proximal tibiofibular joint.
- Attachment Sites: Provides attachment for ligaments such as the anterior and posterior ligaments of the fibular head and muscles like the biceps femoris.
Neck of the Fibula
- Location: Narrow region just below the fibular head.
- Significance: The common peroneal (fibular) nerve courses around this area, making it clinically significant for potential nerve injury.
Shaft
Shape and Surfaces
The shaft of the fibula is slender and triangular in cross-section, consisting of three surfaces:
- Lateral Surface: Provides attachment for the peroneus longus and brevis muscles.
- Medial Surface: Faces the tibia and forms the interosseous border, where the interosseous membrane connects the fibula to the tibia.[2]
- Posterior Surface: Serves as an attachment site for the flexor hallucis longus and other deep posterior leg muscles.
Borders
The shaft has three borders: anterior, posterior, and interosseous.
- Anterior Border: Sharp and prominent, providing structural strength.
- Posterior Border: Rounded and less distinct.
- Interosseous Border: Medially oriented and serves as the attachment site for the interosseous membrane.[3]
Curvature
The shaft is slightly curved, with variations that adapt to muscle attachments and structural requirements.
Distal End
Lateral Malleolus
- Shape and Position: Enlarged and pyramid-shaped, forming the distal end of the fibula.
- Articulations: Articulates with the talus at the ankle joint and provides stability to the lateral aspect of the ankle.[5]
- Attachment Sites: Serves as an anchor point for ligaments like the anterior talofibular, posterior talofibular, and calcaneofibular ligaments.
Malleolar Fossa
- Location: Posterior to the lateral malleolus.
- Significance: Provides attachment for ligaments involved in ankle joint stability.
Articulations
Proximal Tibiofibular Joint
A synovial joint between the fibular head and the lateral condyle of the tibia.
Distal Tibiofibular Joint
A syndesmosis joint formed between the distal end of the fibula and the tibia. This joint is stabilized by strong ligaments.
Ankle Joint
The distal end of the fibula contributes to the formation of the lateral part of the ankle joint, articulating with the talus.[7]
Vascular Supply
The fibula is supplied by branches of the anterior tibial, posterior tibial, and peroneal arteries. Nutrient foramina on the shaft allow for vascular entry.
Muscular and Ligamentous Attachments
- Muscle Attachments: The fibula serves as an origin or insertion site for several muscles, including:
- Lateral compartment: Peroneus longus and brevis.
- Posterior compartment: Flexor hallucis longus and soleus.[8]
- Anterior compartment: Extensor hallucis longus and extensor digitorum longus.
- Ligament Attachments: Key ligaments, such as the interosseous ligament and the ligaments of the ankle joint, anchor to the fibula.
Notable Features
The fibula is primarily a structural bone and is involved in muscle attachment and joint stabilization. Despite its slender appearance, it plays a significant role in the architecture of the lower leg.
Function
- Structural Support: The fibula provides lateral stability to the lower leg and contributes to the overall framework of the leg.[1] Although it does not bear significant weight, it plays an essential role in maintaining leg alignment.
- Stabilization of the Ankle Joint: The fibula forms the lateral malleolus, a key component of the ankle joint. It provides stability to the lateral aspect of the ankle, preventing excessive inversion or eversion during movement.
- Muscle and Ligament Attachment: The fibula serves as an attachment site for several muscles and ligaments involved in lower leg and foot movement. This includes muscles for dorsiflexion, plantarflexion, eversion, and inversion of the foot.
- Support for Interosseous Membrane: The fibula anchors the interosseous membrane, a fibrous sheet that connects the tibia and fibula. This membrane provides additional stability to the leg and serves as a partition for muscle compartments.
- Load Transfer During Locomotion: While the fibula does not carry a significant portion of the body’s weight, it helps transmit forces from the ankle to the tibia and contributes to the mechanics of walking and running.
- Role in Bone Grafting: The fibula is commonly used in bone grafting surgeries because of its relative redundancy in weight-bearing functions and its ability to regenerate.
Clinical Significance
The fibula is critical in various clinical contexts due to its anatomical features and functional roles:
- Fractures:
- Isolated Fibular Fractures: Common in sports injuries or trauma, often involving the lateral malleolus.[4]
- Combined Injuries: Fractures of the fibula often occur with tibial fractures or ankle injuries, such as in bimalleolar or trimalleolar fractures.
- Fibular Grafts: The fibula is frequently used as a donor site for bone grafting in reconstructive surgeries due to its ability to regenerate and its limited weight-bearing role.
- Nerve Injury: The common peroneal nerve, which wraps around the neck of the fibula, is susceptible to injury from trauma or compression, leading to conditions like foot drop.
- Deformities and Malalignment: Improper healing of fibular fractures or congenital abnormalities can lead to malalignment of the lower leg and ankle instability.
- Osteomyelitis and Tumors: The fibula can be affected by infections (osteomyelitis) or bone tumors, requiring clinical intervention.[6]