Fractures of the Tibia and Fibula

Relevant Anatomy

The shafts of the tibia and fibula are composed of a proximal metaphysis, central diaphysis, and distal metaphysis. The blood supply to the tibia is from (1) a nutrient artery, which is a branch of the posterior tibial artery that enters at the junction of the distal and middle thirds of the tibia and is responsible for the endosteal or medullary blood supply; (2) periosteal vessels, which are segmented and enter from muscular attachments; and (3) epiphyseal vessels. The inner two-thirds of the cortex is supplied by the endosteal vessels, and the outer third is supplied by the periosteal vessels. Proximally, the epiphyseal and periosteal vessels are branches of the medial and lateral inferior geniculate arteries from the popliteal artery. The collateral circulation is rich proximally, especially on the medial aspect. Tibia fractures distal to the nutrient artery may deprive the distal fragment of its medullary blood supply, and, in such cases, the distal end of the tibia must rely on its periosteal and metaphyseal blood supply for healing. This supply is limited because of a lack of muscle attachment, and a slower rate of healing generally results. Periosteal and soft tissue stripping of the distal fracture from the injury or surgical intervention further slows the healing process.

The blood supply to the fibula is from the peroneal artery, which gives off a nutrient artery that enters the diaphysis just proximal to its midpoint. The rest of the artery supplies multiple segmental musculoperiosteal vessels that pass circumferentially around the fibula and supply both the fibula and the adjacent muscles.

From a surgical perspective, remember that the popliteal artery descends between the posterior aspects of the medial and lateral femoral condyles. It passes between the medial and lateral heads of the gastrocnemius muscle and along the distal border of the popliteus muscle before dividing into the anterior and posterior tibial arteries. The anterior tibial artery passes anteriorly between the two heads of the tibialis posterior muscle and enters the anterior compartment of the leg by passing through the proximal aspect of the interosseous membrane at the flare of the proximal tibial and fibular metaphyses. Displaced fractures in this region may damage the anterior tibial artery. Fortunately, such injuries rarely occur. The foramen in the interosseous membrane is long and narrow; it affords some protection inasmuch as the anterior tibial artery is allowed to move both proximally and distally. Corrective varus or valgus osteotomies of the proximal portion of the tibia can also damage the anterior tibial artery. Subperiosteal dissection in the region below the tibial tubercle helps protect this vessel.

Fracture Patterns

Fracture patterns involving the tibial and fibular diaphyses include compression (torus), incomplete tension-compression (greenstick), and complete fractures. Plastic deformities can also occur but predominantly involve the fibula. Complete fractures are further classified according to the direction of the fracture (i.e., spiral, oblique, or transverse) and as comminuted or segmental. Approximately 37% of tibial fractures are comminuted. Tibial and fibular fractures may also be open or closed, depending on the integrity of the overlying skin and soft tissues.

Prevalence

Fractures of the tibial and fibular shafts are the most common long bone fractures of the lower extremity and represent approximately 15% of all pediatric fractures. They occur more frequently in boys than in girls. Parrini and colleagues reported on 1027 long bone fractures in children between 1 and 11 years of age, including 326 tibial fractures (32%); 157 were isolated fractures of the tibia, and 169 fractures were of both the tibia and fibula. Cheng and Shen studied 3350 children with 3413 limb fractures and also found tibial shaft fractures to be the most common lower extremity fracture, with a relatively static prevalence of 9% to 12% throughout various pediatric age groups.

An epidemiologic study by Karrholm and associates in Sweden in 1981 showed an annual incidence of 190 tibial fractures per 10,000 boys between infancy and 18 years of age and 110 tibial fractures per 10,000 girls in the same age range. In boys, the incidence peaked between 3 and 4 years of age and again between 15 and 16 years of age. The first peak involved predominantly spiral or oblique fractures, and the second peak involved primarily transverse fractures. In girls, the incidence was relatively even up to 11 to 12 years of age, and the tendency was toward a declining incidence with advancing age.

Mechanisms of Injury

Fractures of the tibia and fibula may be the result of direct or indirect forces. Direct trauma frequently produces a transverse fracture or segmental fracture pattern, whereas indirect forces are typically rotational and produce an oblique or spiral fracture.

In a 1982 study by Karrholm and associates, motor vehicle accidents involving children as passengers, as bicycle riders, or as pedestrians were the most common mechanism of tibial fractures. The age range of children in motor vehicle accidents was 8 to 14 years. Of interest, injuries from winter sports activities had almost the same incidence as motor vehicle accidents in girls. Falls were the most common mechanism of injury in young children. In a 1988 study by Shannak of 142 tibial shaft fractures, motor vehicle accidents caused 63% of the fractures; falls, 18%; direct violence, 15%; and sports, only 4%. A 2007 study by Kute and associates evaluated the trauma database of a pediatric level I trauma center and found that, of 238 patients admitted after all-terrain vehicle accidents, 63% of patients had fractures; of those, 14% occurred in the tibia and fibula.

Consequences of Injury

Despite the frequency of pediatric tibial and fibular fractures, the consequences for most children are minimal. These fractures heal readily with minimal complications. Children typically have a rapid return to normal activities, including sports, and minimal disability. However, in a small percentage of cases, especially those involving open fractures or severe soft tissue injury, residual disability may occur.

Associated Injuries

It is not uncommon for children who sustain tibial and fibular fractures to have associated injuries, especially children who are victims of high-energy trauma, such as from motor vehicle–related accidents. In the study by Karrholm and associates, 27 of 480 children (6%) with tibial and fibular fractures sustained associated injuries, of which the most common were head injuries, fractures of the femur, and injury to an upper extremity. Other body areas (i.e., face and neck, chest, and abdomen) may also be injured, depending on the severity of the trauma. Children with open tibial fractures have the highest incidence of associated injuries.

Classification

A classification of nonphyseal fractures of the tibia and fibula is presented in Box 14.1 . A modification of the classification of Dias, this classification divides the tibial and fibular shafts into their three major anatomic areas: proximal metaphysis, diaphyses, and distal metaphysis. Fractures of the tibial and fibular diaphyses are subdivided according to the location (proximal third, middle third, and distal third) and the combination of bones fractured. This classification is useful for determining treatment methods and understanding potential long-term results and possible complications.

The recently proposed AO Pediatric Comprehensive Classification of Long Bone Fractures has recently been shown to be clinically relevant with regard to growth and recovery. However, further studies for confirmation are necessary.

History

The typical symptom of a tibial or fibular fracture is pain. However, the severity of the pain varies with the magnitude of the injury, the mechanism, and the age of the child. Frequently, a history is unavailable because the injury was not observed and the child is unable to verbalize symptoms or the mechanism of injury. In these cases, child abuse or battered child syndrome must also be considered (see Chapter 20 ). In young children, an inability to walk may be the only sign or symptom. If the child is able to speak, it is important to ascertain the mechanism of injury, if possible.

Physical Examination

Because pain is the major symptom in a tibial or fibular shaft fracture, it is important to have the child point to the most painful area. Palpation in this area may reproduce or increase the child’s discomfort. Deformity is not a common finding in young children because many tibial fractures are nondisplaced. Swelling or edema of the lower part of the leg also varies according to the mechanism of injury, the extent of soft tissue injury, and the presence of displacement. Usually, the soft tissue swelling is maximal at the fracture site. Stress examination may reveal instability or crepitation but invariably increases pain. A stress examination is usually unnecessary when a fracture is suspected. Injured extremities with a suspected tibial fracture are best splinted before radiographic evaluation, usually with a long leg posterior plaster splint. This relieves pain, prevents additional injury to the soft tissues, and allows for more accurate positioning of the extremity for radiographs.

Nerve damage in association with closed tibial and fibular fractures is very uncommon (see “Neurologic Injury” section). However, in all fractures, it is important to check dorsiflexion and plantar flexion of the foot and toes, as well as sensation, especially to touch. Nerve damage, if present, is most likely the result of a direct injury to the peroneal nerve at the proximal fibular metaphysis.

Arterial injuries associated with a closed tibial shaft fracture are also very uncommon (see “Vascular Injury” section). The peripheral pulses of the dorsalis pedis and posterior tibial arteries must be evaluated and recorded at the initial physical examination. Arterial injuries are most likely to be associated with a displaced proximal tibial metaphyseal fracture or an open fracture. Capillary circulation, sensation to the toes, pain on passive stretching, and pain out of proportion to the injury must be monitored carefully because compartment syndromes can occur in children after tibial fractures (see “Compartment Syndrome” section).

The soft tissues of the lower part of the leg must also be evaluated. It is important to assess the integrity of the skin at the fracture site. Fractures related to bicycle spoke injuries may ultimately result in full-thickness skin loss requiring delayed skin grafting. Any evidence of skin penetration at the fracture site is an indication that the fracture is open and contaminated (see “Open Tibial and Fibular Fractures” section).

Radiographic Evaluation

When a tibial or fibular shaft fracture is suspected, radiographs must be taken. After splinting of the injured extremity, anteroposterior (AP) and lateral radiographs are obtained. They must include the knee and ankle joints to rule out an associated epiphyseal fracture. Comparison radiographs of the opposite extremity may be indicated in complicated injuries, but this situation is unusual. Occasionally, incomplete fractures, such as a torus fracture, may be difficult to visualize. A spiral fracture of the tibial shaft with an intact fibula may be visible on only one view. It is therefore imperative that orthogonal radiographs always be obtained. Oblique radiographs may be beneficial if the initial radiographic appearance is normal but a fracture is suspected.

Special Diagnostic Studies

Special diagnostic imaging studies of the tibia and fibula may include ultrasonography, technetium bone scans, computed tomography (CT), and magnetic resonance imaging (MRI).

Ultrasonography was recently shown to be at least as successful as radiography in diagnosing tibia fractures in both children and adults. Although not commonly used, it can be considered in difficult cases or when radiography may not be readily available.

Technetium bone scans may be useful in identifying occult fractures, especially in infants. Park and colleagues found that bone scans could be used to differentiate occult fractures of the femur or tibia from early acute osteomyelitis in infants. Images obtained early (1–4 days after the onset of symptoms) demonstrated a subtle increase in uptake along the entire length of the injured bone when an occult fracture was present. The distribution of uptake was similar regardless of the fracture pattern. In early acute osteomyelitis, focal uptake was observed at the site of infection. Technetium bone scan can also be useful in toddler’s and stress fractures.

CT of the tibia can be used to assess torsional alignment after complex unilateral fractures. It can also be used in the assessment of pathologic fractures of the tibia to determine the presence, size, and intralesional contours of the lesion. MRI can be used to detect early stress fractures accurately. This procedure, although expensive, avoids the high doses of radiation incurred with bone scans and CT.

Fractures of the Proximal Tibial Metaphysis

Proximal tibial metaphyseal fractures are relatively uncommon injuries that generally occur in children between 3 and 6 years of age (range, 1–12 years). The male-to-female ratio of approximately 3:1 closely parallels the incidence of tibial fractures by gender in children. These fractures are typically the result of a direct injury to the lateral aspect of the extended knee. Most of these fractures have minimal or no displacement and appear benign radiographically; however, they may, in fact, be followed by a posttraumatic valgus deformity. Greenstick and complete fractures are most commonly associated with a valgus deformity. Such deformities are unusual after a torus fracture. In a greenstick fracture, the medial cortex (tension side) fractures while the lateral cortex (compression side) remains intact or hinges slightly. If the lateral cortex hinges, a valgus deformity occurs. However, displacement is not usually seen, and apposition remains normal. The fibula is typically intact but may occasionally sustain either a fracture or plastic deformation. Radiographically, the degree of angulation can be difficult to ascertain unless radiographs are obtained of both lower extremities symmetrically positioned on a long cassette and the true angulation is measured. Oblique views and, occasionally, fluoroscopy may be beneficial in defining the fracture and any angulation.

There have been numerous reports of posttraumatic genu valgum after proximal tibial fractures. Interestingly, similar valgus deformities may occur in association with other conditions affecting the proximal tibial metaphysis, such as acute and chronic osteomyelitis, harvesting of a bone graft, excision of an osteochondroma, and osteotomy.

The incidence of a valgus deformity after a proximal tibial metaphyseal fracture varies greatly, ranging from 0% to 62%. Theories regarding the cause of valgus deformity have included injury to the lateral aspect of the proximal tibial physis, inadequate reduction, premature weight bearing, hypertrophic callus formation, dynamic muscle action, soft tissue interposition (periosteum, pes anserinus, medial collateral ligament), tethering from an intact fibula, and asymmetric growth stimulation. However, valgus deformity has been reported after complete fractures of the proximal ends of the tibia and fibula.

Currently, most authors attribute valgus deformity to asymmetric growth of the proximal part of the tibia. Houghton and Rooker, in experimental studies with immature rabbits, found that medial hemicircumferential division of the periosteum resulted in valgus overgrowth. They believed that if the medial periosteum is torn during a proximal tibial metaphyseal fracture, asymmetric overgrowth occurs and produces a valgus deformity. Spontaneous correction with growth has also been observed.

Aronson and colleagues in 1990 reported on an experimental model with immature rabbits that confirmed asymmetric growth as the cause of posttraumatic valgus deformity. Twenty-two 8-week-old rabbits were divided into two equal groups. In one group, the periosteum on the medial aspect of the proximal tibial metaphysis was excised, and a partial osteotomy involving the medial half of the metaphysis was performed. In the other group, the same procedure was performed on the lateral side. Parallel K-wires were inserted above and below the partial osteotomy. A valgus deformity (mean of 12 degrees) occurred in the first group, and a varus deformity (mean of 10 degrees) developed in the second. In each animal, the K-wires remained parallel, thus indicating that the deformity occurred at the physis. Despite the asymmetric growth, the light microscopic appearance of the physes was normal. The deformities were therefore attributed to asymmetric physeal growth, which was not demonstrable histologically. Ogden reported that the normal circulation to the knee has a more extensive medial geniculate blood supply, especially in the proximal tibial region, than a lateral geniculate supply, which may be responsible for transient eccentric growth. Zionts and colleagues supported the concept of eccentric growth by demonstrating, in quantitative scintigraphic studies, proportionally greater uptake on the medial side than the lateral side and overall increased uptake on the injured as compared with the uninjured side. In 1995, Ogden and colleagues performed detailed measurements of the metaphyseal-diaphyseal-metaphyseal distances medially and laterally of the injured and noninjured tibias of 17 children with 19 proximal tibial metaphyseal fractures (2 children had bilateral fractures) monitored for a mean of 3.7 years (range, 2–7 years). The difference between the medial and lateral sides of the injured tibias was 7.4 mm, which was an indication of eccentric medial growth. Interestingly, the 3.3-mm difference noted between the injured and uninjured lateral sides was a reflection of overall growth stimulation on the injured side. These observations occurred with or without an intact fibula.

It is clear from these studies that a valgus deformity is not usually a complication of the initial reduction but, instead, is secondary to differential growth between the medial and lateral aspects of the proximal tibial epiphysis.