Support for weightbearing is provided primarily by the tibia.
The tibia has a thick cortex, and significant force is required
to fracture it. Proximally, the tibia splays out to form the medial
and lateral plateaus that articulate with the femoral condyles.
The lateral plateau is higher and smaller than the medial and is
more susceptible to fracture. The distal tibia articulates with
the fibula laterally and the talus inferiorly. The tibia and fibula
are connected by a dense interosseous membrane. The distal tibial
articulation is supported by the ankle syndesmosis, a series of
ligaments inferior to the interosseous membrane. The fibula has
a small diameter and lies lateral and posterior to the tibia. It
bears little weight but is more easily fractured than the tibia.
The lower leg is divided into four compartments, each coursing
parallel to the tibia (Figure 272-1). The
compartments are enclosed by nonexpandable bones and connective
tissue that limit the compartment size and prevent compartment expansion
if its volume increases. Each compartment contains muscles and nerves
that may sustain permanent damage with elevated tissue compartment
pressure (Table 272-1). (See also Chapter 275, Compartment Syndrome.)
Lower leg anatomy.
Table 272-1 Lower Leg Anatomy
| Save Table
Table 272-1 Lower Leg Anatomy
|Anterior||Lateral||Superficial Posterior||Deep Posterior|
|Muscles||Dorsiflex foot and ankle||Plantarflex and evert foot||Flex knee and ankle||Plantarflex toes, inversion foot|
|Nerve||Deep peroneal||Superficial peroneal||Sural||Posterior tibial|
|Sensation||First dorsal webspace||Dorsum of foot||Lateral aspect of foot and distal calf||Sole of foot|
|Artery||Anterior tibial||—||—||Posterior tibial|
A cross-section at the midcalf level shows the anterior compartment enclosed
by the tibia, interosseous membrane, and anterior crural septum
(Table 272-1 and Figure
272-1). Muscles in the anterior compartment group dorsiflex
the foot and ankle. The deep peroneal nerve courses within the anterior
compartment and exits to provide sensation to the dorsal web space
between the first and second toes.
The lateral compartment is bordered by the anterior crural septum,
the fibula, and the posterior crural septum. Its muscles plantarflex
and evert the foot. The superficial peroneal nerve in this compartment
provides sensation to the dorsum of the foot. The superficial posterior
compartment contains muscles that flex the knee and the tibiotalar
joints. Its sural nerve provides sensation for the lateral aspect
of the foot and the distal calf. The muscles of the deep posterior
compartment plantarflex the foot and toes and invert the foot. The
posterior tibial nerve that exits this compartment provides sensation
to the sole of the foot.
Leg injuries are initially evaluated with a directed history,
including the mechanism of injury. The history may give clues about
nontraumatic soft tissue injuries. Evaluate the nerves by checking
sensation in the web space, lateral heel, and sole of the foot.
To test motor function, plantar and dorsal flex the foot, and evert
the foot. Evaluate the extent of soft tissue injury visually and
by palpating the compartmental muscle groups. It is often the extent
of soft tissue injury, rather than the fracture itself, that determines
the outcome. Palpate the tibia and fibula along their entire lengths.
Palpate the popliteal, dorsal pedal, and posterior tibial pulses.
An absent or decreased pulse may indicate the need for urgent fracture
reduction and further vascular evaluation. Anteroposterior (AP)
and lateral radiographs of the leg that include the knee and ankle
are sufficient to evaluate bony injuries. If ankle or knee injuries
are suspected, then further imaging is needed. If a tibial shaft
fracture is suspected, splint the leg with a radiolucent device
to control pain and prevent further soft tissue damage before obtaining
films. Check pulses, movement, and sensation before and after splinting
Wounds should be cleansed and debrided of loose tissue and foreign
material. Administer tetanus immunization as indicated. Splinting
of fractures should occur before radiographs are obtained; this
will prevent further damage to soft tissue caused by movement of
bone fragments. (see video: Posterior Leg Splint.) Irrigate open
wounds and administer parenteral antibiotics (such as cefazolin,
1 gram IV) for open fractures. If compartment syndrome is suspected,
pressure should be measured (see Chapter 275, Compartment Syndrome). Treatment of compartment syndrome is fasciotomy
of the involved compartment.
Wounds that are not adequately cleansed and debrided are prone
to infection. Patients with compartment syndromes may develop permanent disability
if elevated tissue pressures are not suspected or diagnosed in a timely
fashion. Fractures that are not adequately aligned or immobilized heal
poorly or not at all.
The tibia is the most commonly fractured long bone. Fractures
often result in open injuries because of the minimal amount of subcutaneous
tissue between it and the skin. The fracture pattern seen on radiographs
will give a clue to the force that caused the injury. Transverse
shaft fractures typically result from a direct blow to the bone.
Spiral fractures are the result of rotational forces. A comminuted
fracture suggests the mechanism had a very high energy impact. A
force powerful enough to shatter the dense cortex of the tibial
shaft will often be transmitted through the interosseous membrane
to the fibula, fracturing that bone as well.
Open tibial shaft fractures have been classified by Gustillo.1 A
Grade 1 injury has minimal soft tissue contusion and a skin laceration
that is 1 cm in length or less. A Grade 2 injury involves a wound
with a >1-cm laceration with moderate soft tissue injury and moderate
contamination; the tibia is moderately comminuted. A Grade 3 injury
can involve segmental injury to the tibia, a vascular ...