Tibial and fibular injuries

Essentials

1
Tibial shaft fractures are the commonest long bone fracture, with the subcutaneous nature of the tibia leaving it vulnerable to open injury.
2
Neurovascular injury and compartment syndrome are risks in tibial shaft fractures.
3
Proximal fibular fractures are associated with common peroneal (lateral popliteal) nerve injury.
4
Tibial tubercle injuries range from apophysitis to fracture.

Anatomy

The tibia is the weight-bearing strut of the lower leg. Proximally the tibia articulates with the femoral condyles and distally the bony extension provides medial stability to the ankle joint. Its shaft is triangular in cross section and is subcutaneous anteromedially.

The fibular head is proximal and connects to the fibular shaft by the neck. Distally, the fibula is palpated subcutaneously as the lateral malleolus.

The tibia and fibula are connected by superior and inferior tibiofibular joints and a dense interosseous membrane. Distally, this union is strengthened by a syndesmosis, which enhances the stability of the ankle mortise.

Fascial compartments of the lower leg

The lower leg is divided by bone and fascia into four compartments. Each compartment contains a sensory nerve and muscles with specific functions. Increased pressure within a compartment is evaluated clinically by impaired function according to the functional anatomy.

Anterior compartment

The anterior compartment contains the tibialis anterior, extensor hallucis longus, extensor digitorum longus and peroneus tertius, which dorsiflex the ankle and foot. The deep peroneal nerve supplies these muscles and the first web space of the foot. The anterior tibial artery is contained within the compartment down to the ankle, where it becomes the dorsalis pedis artery.

Lateral compartment

The lateral compartment contains the peroneus longus and peroneus brevis, which evert the foot, and the superficial peroneal nerve, which supplies sensation to the dorsum of the foot.

Superficial posterior compartment

The superficial posterior compartment contains the gastrocnemius, plantaris and soleus muscles, which plantarflex the ankle. The sural nerve lies in this compartment before piercing the fascia to supply the lateral side of the foot and distal calf.

Deep posterior compartment

The deep posterior compartment contains the tibialis posterior, flexor hallucis longus and flexor digitorum longus, which work to plantarflex the foot and toes. The popliteus is also in this compartment and is used for unlocking the knee when walking. The tibial nerve supplies sensory function to the sole of the foot. The compartment is transversed by the posterior tibial and peroneal arteries.

Fractures of the tibia

Tibial shaft fracture

Tibial shaft fractures are the most common long bone fracture. They are also the commonest open fracture owing to the subcutaneous nature of the tibial shaft.

A considerable amount of direct or indirect energy is needed for the tibial shaft to fracture. Direct injuries may occur secondary to bending forces or a direct blow. Direct violence causes deformation at the site of contact, resulting in transverse or comminuted, usually open, fractures. High-energy injuries have an increased degree of displacement, comminution, soft tissue injury and fibular involvement. They are largely unstable, with marked vascular and inter-osseous injury. There is a high risk of compartment syndrome, with up to 15% complicated by malunion or non-union.

Indirect torsional forces applied to the tibia produce a spiral fracture as the body rotates about a fixed foot. Such injuries are common in skiing incidents and have increasing degrees of comminution depending on the amount of energy applied.

Classification

The description of the fracture must be clear and concise in relation to the following ( Table 4.10.1 for the AO classification of tibial shaft fractures) :

Skin integrity: open or closed
Anatomic site: proximal, middle or distal third
Fracture type: transverse, oblique, spiral or comminuted
Angulation of the distal fragment in relation to the proximal fragment, expressed in degrees and direction (anterior, posterior, varus or valgus)
Degree of displacement and rotation
Involvement of the fibula
Any joint involvement

Table 4.10.1

AO classification of tibial shaft fractures

Type A (simple)	1	Spiral
	2	Oblique (angle >30 degrees)
	3	Transverse (angle <30 degrees)
Type B (multi-frag wedge)	1	Spiral wedge
	2	Bending wedge
	3	Fragmented wedge
Type C (multi-frag complex)	1	Spiral wedge
	2	Segmental
	3	Irregular

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