PEDIATRIC TIBIA AND FIBULA

EPIDEMIOLOGY

Tibia fractures represent the third most common pediatric long bone fracture, after femur and forearm fractures.

They represent 15% of pediatric fractures.

The average age of occurrence is 8 years of age.

Of these fractures, 30% are associated with ipsilateral fibular fractures.

The ratio of incidence in boys and girls is 2:1.

The tibia is the second most commonly fractured bone in abused children; 26% of abused children with fractures have a tibia fracture.

ANATOMY

The anteromedial aspect of the tibia is subcutaneous, with no overlying musculature for protection.

Three consistent ossification centers form the tibia:

• Diaphyseal: Ossification occurs at 7 weeks of gestation.

• Proximal epiphysis: The ossification center appears just after birth, with closure at age 16 years.

• Distal epiphysis: The ossification center appears in the second year, with closure at age 15

  years.

The medial malleolus and tibial tubercle may present as separate ossification centers and should not be confused with fracture.

Fibular ossification centers:

• Diaphyseal: Ossification occurs at 8 weeks of gestation.

• Distal epiphysis: The ossification center appears at age 2 years, with closure at age 16 years.

• Proximal epiphysis: The ossification center appears at age 4 years, with closure at age 16 to 18

  years.

  MECHANISM OF INJURY

Of pediatric ipsilateral tibia and fibula fractures, 50% result from motor vehicle trauma.

Of tibia fractures with an intact fibula, 81% are caused by indirect rotational forces.

Children ages 1 to 4 years old are susceptible to bicycle spoke trauma, whereas children 4 to 14 years old most often sustain tibia fractures during athletic or motor vehicle accidents.

Isolated fibula fractures are usually the result of a direct blow.

CLINICAL EVALUATION

Full pediatric trauma protocol must be observed because >60% of tibial fractures are associated with motor vehicle or pedestrian–motor vehicle trauma.

Patients typically present with the inability to bear weight on the injured lower extremity, as well as pain, variable gross deformity, and painful range of motion of the knee or ankle.

Neurovascular evaluation is essential, with assessment of both the dorsalis pedis and posterior tibial artery pulses.

Palpation of the anterior, lateral, and posterior (deep and superficial) muscle compartments should be performed to evaluate possible compartment syndrome. When suspected, compartment pressure measurement should be undertaken, with emergent fasciotomies performed in the case of compartment syndrome.

Field dressings/splints should be removed with exposure of the entire leg to assess soft tissue compromise and to rule out open fracture.

RADIOGRAPHIC EVALUATION

Anteroposterior (AP) and lateral views of the tibia and knee should be obtained. AP, lateral, and mortise views of the ankle should be obtained to rule out concomitant ankle injury.

Comparison radiographs of the uninjured contralateral extremity are rarely necessary.

Technetium bone scan or magnetic resonance imaging (MRI) may be obtained to rule out occult fracture in the appropriate clinical setting.

PROXIMAL TIBIAL METAPHYSEAL FRACTURES

Epidemiology

Uncommon, representing <5% of pediatric fractures and 11% of pediatric tibia fractures

Peak incidence at 3 to 6 years

Anatomy

The proximal tibial physis is generally structurally weaker than the metaphyseal region; this accounts for the lower incidence of fractures in the tibial metaphysis.

Mechanism of Injury

Most common is force applied to the lateral aspect of the extended knee that causes the cortex of the medial metaphysis to fail in tension, usually as nondisplaced greenstick fractures of the medial cortex.

The fibula usually does not fracture, although plastic deformation may occur.

Clinical Evaluation

The patient typically presents with pain, swelling, and tenderness in the region of the fracture.

Motion of the knee is painful, and the child usually refuses to ambulate.

Valgus deformity is typically present.

Radiographic Evaluation

AP and lateral views of the tibia should be obtained, as well as appropriate views of the knee and ankle to rule out associated injuries.

Classification

Descriptive

Angulation Displacement Open versus closed

Pattern: transverse, oblique, spiral, greenstick, plastic deformation, torus Comminution

Treatment

Nonoperative

Nondisplaced fractures may be treated in a long leg cast with the knee in near full extension and with a varus mold.

Displaced fractures should undergo closed reduction with the patient under general anesthesia or conscious sedation, with application of a long leg cast with the knee in full extension and varus moment placed on the cast to prevent valgus collapse.

The cast should be maintained for 6 to 8 weeks with frequent radiographic evaluation to rule out displacement.

Normal activities may be resumed when normal knee and ankle motions are restored and the fracture site is nontender.

Operative

Fractures that cannot be reduced by closed means should undergo open reduction with removal of interposed soft tissue.

The pes anserinus insertion should be repaired if torn, with restoration of tension.

A long leg cast with the knee in full extension should be placed and maintained for 6 to 8 weeks postoperatively with serial radiographs to monitor healing.

Open fractures or grossly contaminated fractures with associated vascular compromise may be treated with debridement of compromised tissues and external fixation, particularly in older children. Regional or free flap or skin grafting may be required for skin closure.

Complications

Progressive valgus angulation: May result from a combination of factors, including disruption of the lateral physis at the time of injury, fracture overgrowth, entrapment of periosteum at the medial fracture site with consequent stimulation of the physis, or concomitant pes anserinus injury that results in a loss of inhibitory tethering effect on the physis, allowing overgrowth. The deformity is most prominent within 1 year of fracture; younger patients may experience spontaneous correction with remodeling, although older patients may require hemiepiphysiodesis or corrective osteotomy.

Premature proximal tibial physeal closure: May occur with unrecognized crush injury (Salter–Harris type V) to the proximal tibial physis, resulting in growth arrest. This most commonly affects the anterior physis and leads to a recurvatum deformity of the affected knee.

DIAPHYSEAL FRACTURES OF THE TIBIA AND FIBULA

Epidemiology

Of pediatric tibial fractures, 39% occur in the middle third.

Approximately 30% of pediatric diaphyseal fractures are associated with a fracture of the fibula. Occasionally, this is in the form of plastic deformation, producing valgus alignment of the tibia.

Isolated fractures of the fibular shaft are rare and result from direct trauma to the lateral aspect of the leg.

Anatomy

The nutrient artery arises from the posterior tibial artery, entering the posterolateral cortex distal to the origination of the soleus muscle, at the oblique line of the tibia. Once the vessel enters the intramedullary canal, it gives off three ascending branches and one descending branch. These give rise to the endosteal vascular tree, which anastomoses with periosteal vessels arising from the anterior tibial artery.

The anterior tibial artery is particularly vulnerable to injury as it passes through a hiatus in the interosseous membrane.

The peroneal artery has an anterior communicating branch to the dorsalis pedis artery.

The fibula is responsible for 6% to 17% of weight-bearing load. The common peroneal nerve courses around the neck of the fibula, which is nearly subcutaneous in this region; it is therefore especially vulnerable to direct blows or traction injuries at this level.

Mechanism of Injury

Direct: Trauma to the leg occurs, mostly in the form of vehicular trauma or pedestrian–motor vehicle accident.

Indirect: In younger children, most tibial fractures result from torsional forces. These spiral and

oblique fractures occur as the body mass rotates on a planted foot. The fibula prevents significant shortening when intact, but the fracture frequently falls into varus.

Clinical Evaluation

The patient typically presents with pain, swelling, and tenderness in the region of the fracture.

Motion of the knee is painful, and the child usually refuses to ambulate.

Children with stress fractures of the tibia may complain of pain on weight bearing that is partially relieved by rest.

Radiographic Evaluation

Standard AP and lateral views of the leg should be obtained.

Radiographs of the ipsilateral ankle and knee should be obtained to rule out associated injuries.

Comparison views of the uninjured, contralateral leg may be obtained in cases in which the diagnosis is unclear.

MRI may be obtained to rule out occult fracture.

Classification

Descriptive

Angulation Displacement Open versus closed

Pattern: transverse, oblique, spiral, greenstick, plastic deformation, torus Comminution

Treatment

Nonoperative

Most pediatric fractures of the tibia and fibula are uncomplicated and may be treated by simple manipulation and casting, especially when they are nondisplaced or minimally displaced. However, isolated tibial diaphyseal fractures tend to fall into varus, whereas fractures of the tibia and fibula tend to fall into valgus with shortening and recurvatum (Fig. 50.1).

Displaced fractures may be initially treated with closed reduction and casting with the patient under general anesthesia.

• In children, acceptable reduction includes 50% apposition of the fracture ends, <1 cm of shortening, and <5- to 10-degree angulation in the sagittal and coronal planes with <5 degrees of rotation.

• A long leg cast is applied with the ankle slightly plantar flexed (20 degrees for distal and middle third fractures, 10 degrees for proximal third fractures) to prevent posterior angulation of the fracture in the initial 2 to 3 weeks. The knee is flexed to 45 degrees to provide rotational control and to prevent weight bearing.

• Fracture alignment must be carefully monitored, particularly during the initial 3 weeks. Atrophy and diminished swelling may result in loss of reduction. Some patients require repeat manipulation and cast application under general anesthesia 2 to 3 weeks after initial casting.

• The cast may require wedging (opening or closing wedge) to provide correction of angulatory deformity. If the anticipated wedge is to be greater than 15 degrees, it is advisable to change the cast.

• Time to healing varies according to patient age:

• Neonates: 2 to 3 weeks

• Children: 4 to 6 weeks

• Adolescents: 8 to 12 weeks

  Operative

Operative management of tibial fractures in children are typically required in <5% of cases.

Indications for operative management include:

• Open fracture

• Fractures in which a stable reduction is unable to be achieved or maintained

• Associated vascular injury

• Fractures associated with compartment syndrome

• Severely comminuted fractures

• Associated femoral fracture (floating knee)

• Fractures in patients with spasticity syndromes (cerebral palsy, head injury)

• Patients with bleeding diatheses (hemophilia)

• Patients with multisystem injuries

Open fractures or grossly contaminated fractures with associated vascular compromise may be treated with debridement of compromised tissues and external fixation, particularly in older children. Regional or free flaps or skin grafting may be required for skin closure.

Other methods of operative fixation include percutaneous pins, plates and screws, flexible or “elastic” intramedullary nails or rigid intramedullary nails (in adolescents, after closure of the proximal tibia physis).

Postoperatively, a long leg cast is usually placed (depending on the method of fixation), with the knee in 15 degrees of flexion to allow for rotational control. The cast is maintained for 4 to 16 weeks depending on the status of healing, as evidenced by serial radiographs, as well as the healing of associated injuries.

Complications

Compartment syndrome: In pediatric tibia fractures, compartment syndrome is most common after severe injury in which the interosseous membrane surrounding the anterior compartment is disrupted. Patients with elevated compartment pressures >30 mm Hg or within 30 mm Hg of diastolic blood pressure should receive emergency fasciotomies of all four compartments of the leg to avoid neurologic and ischemic sequelae.

Angular deformity: Correction of deformity varies by age and gender.

• Girls <8 years old and boys <10 years old often experience significant remodeling.

• Girls 9 to 12 years old and boys 11 to 12 years old can correct up to 50% of angulation.

• In adolescents >13 years, <25% angular correction is expected.

• Posterior and valgus angulation tends to correct the least with remodeling.

Malrotation: Rotational deformity of the tibia does not correct with remodeling and is poorly

tolerated, often resulting in malpositioning of the foot with the development of associated ankle and foot problems. Supramalleolar osteotomy may be required for rotational correction.

Premature proximal tibial physeal closure: This may occur with unrecognized crush injury (Salter–Harris type V) to the proximal tibial physis, resulting in growth arrest. This most commonly affects the anterior physis and leads to a recurvatum deformity of the affected knee.

Delayed union and nonunion: Uncommon in children, but it may occur as a result of infection, the use of external fixation, or inadequate immobilization. Fibulectomy, bone grafting, reamed intramedullary nailing (adolescents), and plate fixation with bone grafting have all been described as methods to treat tibial nonunions in the pediatric population.

FRACTURES OF THE DISTAL TIBIAL METAPHYSIS

Epidemiology

Fractures of the distal third of the tibia comprise approximately 50% of pediatric tibia fractures.

Most occur in patients younger than 14 years, with the peak range of incidence in children between ages 2 and 8 years.

Anatomy

Distally, the tibia flares out as the cortical diaphyseal bone changes to cancellous metaphyseal bone overlying the articular surface. This is similar to the tibial plateau in that there is primarily cancellous bone within a thin cortical shell.

Mechanism of Injury

Indirect: An axial load results from a jump or fall from a height.

Direct: Trauma to the lower leg occurs, such as in bicycle spoke injuries in which a child’s foot is thrust forcibly between the spokes of a turning bicycle wheel, resulting in severe crush to the distal leg, ankle, and foot with variable soft tissue injury.

Clinical Evaluation

Patients are typically unable to ambulate or are ambulatory only with severe pain.

Although swelling may be present with variable abrasions or lacerations, the foot, ankle, and leg typically appear relatively normal without gross deformity.

The entire foot, ankle, and leg should be exposed to evaluate the extent of soft tissue injury and to assess for possible open fracture.

A careful neurovascular examination is important, and the presence of compartment syndrome must be excluded.

In cases of bicycle spoke injuries, palpation of all bony structures of the foot and ankle should be performed, as well as assessment of ligamentous integrity and stability.

Radiographic Evaluation

AP and lateral views of the leg should be obtained. Appropriate views of the ankle and knee

should be taken to rule out associated injuries, as well as views of the foot as indicated.

Fractures of the distal metaphysis typically represent greenstick injuries, with anterior cortical impaction, posterior cortical disruption, and tearing of the overlying periosteum, often resulting in a recurvatum pattern of injury.

In severe torsional injuries with impaction or distraction forces, a spiral fracture may result.

Computed tomography is usually unnecessary, but it may aid in fracture definition in comminuted or complex fractures.

Classification

Descriptive

Angulation Displacement Open versus closed

Pattern: transverse, oblique, spiral, greenstick, plastic deformation, torus Comminution

Associated injuries: knee, ankle, foot

Treatment

Nonoperative

Nondisplaced, minimally displaced, torus, or greenstick fractures should be treated with manipulation and placement of a long leg cast.

In cases of recurvatum deformity of the tibial fracture, the foot should be placed in plantar flexion to prevent angulation into recurvatum.

After 3 to 4 weeks of cast immobilization, if the fracture demonstrates radiographic evidence of healing, the long leg cast is discontinued and is changed to a short leg walking cast with the ankle in the neutral position.

A child with a bicycle spoke injury should be admitted as an inpatient for observation, because the extent of soft tissue compromise may not be initially evident.

• A long leg splint should be applied with the lower extremity elevated for 24 hours, with serial examination of the soft tissue envelope over the ensuing 48 hours.

• If no open fracture exists and soft tissue compromise is minimal, a long leg cast may be placed

  before discharge, with immobilization as described previously.

  Operative

Surgical intervention is warranted for cases of open fracture or when stable reduction is not possible by closed means.

Unstable distal tibial fractures can typically be managed with closed reduction and percutaneous pinning using Steinmann pins or Kirschner wire fixation. Rarely, a comminuted fracture may require open reduction and internal fixation using pins or plates and screws placed either open or in a percutaneous manner. Flexible or elastic intramedullary nails (EIN) may be utilized as well

(Fig. 50.2).

• Postoperatively, the patient is immobilized in a long leg cast. The fracture should be monitored with serial radiographs to assess healing. At 3 to 4 weeks, the pins may be removed with replacement of the cast either with a long leg cast or a short leg walking cast, based on the extent of healing.

   

   

   

Open fractures may require external fixation to allow for wound management. Devitalized tissue should be debrided as necrosis becomes apparent. Aspiration of large hematomas should be undertaken to avoid compromise of overlying skin. Skin grafts or flaps (regional or free) may be necessary for wound closure.

Complications

Recurvatum: Inadequate reduction or fracture subsidence may result in a recurvatum deformity at

the fracture. Younger patients tend to tolerate this better, because remodeling typically renders the deformity clinically insignificant. Older patients may require supramalleolar osteotomy for severe recurvatum deformity that compromises ankle function and gait.

Premature distal tibial physeal closure: This may occur with unrecognized crush injury (Salter–Harris type V) to the distal tibial physis, resulting in growth arrest.

TODDLER’S FRACTURE

Epidemiology

A toddler’s fracture is by definition a spiral fracture of the tibia in the appropriate age group.

Most of these fractures occur in children younger than 2.5 years.

The average age of incidence is 27 months.

This tends to occur in boys more often than in girls and in the right leg more frequently than the left.

Anatomy

The distal epiphysis appears at approximately 2 years of age; thus, physeal injuries of the distal tibia may not be readily apparent and must be suspected.

Mechanism of Injury

The classic description of the mechanism of a toddler’s fracture is external rotation of the foot with the knee in fixed position, producing a spiral fracture of the tibia with or without concomitant fibular fracture.

This injury has also been reported as a result of a fall.

Clinical Evaluation

Patients typically present irritable and nonambulatory or with an acute antalgic limp.

The examination of a child refusing to ambulate without readily identifiable causes should include a careful history, with attention to temporal progression of symptoms and signs (e.g., fever), as well as a systematic evaluation of the hip, thigh, knee, leg, ankle, and foot, with attention to points of tenderness, swelling, or ecchymosis. This should be followed by radiographic evaluation as well as appropriate laboratory analysis if the diagnosis remains in doubt.

In the case of a toddler’s fracture, pain and swelling are variable on palpation of the tibia. These features are usually appreciated over the anteromedial aspect of the tibia, where its subcutaneous nature allows for minimal soft tissue protection.

Radiographic Evaluation

AP and lateral views of the leg should be obtained.

An internal oblique radiograph of the leg may be helpful for demonstration of a nondisplaced spiral fracture as these fractures may be quite difficult to appreciate on plain films.

Occasionally, an incomplete fracture may not be appreciated on presentation radiographs but may become radiographically evident 7 to 10 days after the injury as periosteal new bone formation

occurs.

Technetium bone scans may aid in the diagnosis of toddler’s fracture by visualization of diffusely increased uptake throughout the tibia. This may be differentiated from infection, which tends to produce a localized area of increased uptake.

Treatment

A long leg cast for 2 to 3 weeks followed by conversion to a short leg walking cast for an additional 2 to 3 weeks is usually sufficient.

Manipulation is generally not necessary because angulation and displacement are usually minimal and within acceptable limits.

Complications

Complications of toddler’s fractures are rare owing to the low-energy nature of the injury, the age of the patient, and the rapid and complete healing that typically accompanies this fracture pattern.

Rotational deformity: Toddler’s fractures may result in clinically insignificant rotational deformity of the tibia as the fracture slides minimally along the spiral configuration. This is usually unnoticed by the patient but may be appreciated on comparison examination of the lower limbs.

STRESS FRACTURES

Epidemiology

Most tibial stress fractures occur in the proximal third.

The peak incidence of tibial stress fractures in children is between the ages of 10 and 15 years.

Most fibular stress fractures occur in the distal third, but may also occur in the proximal third.

The peak incidence of fibular stress fractures in children is between the ages of 2 and 8 years.

The tibia is more often affected than the fibula in children; the opposite is true in adults.

Mechanism of Injury

An acute fracture occurs when the force applied to a bone exceeds the bone’s capacity to withstand it. A stress fracture occurs when a bone is subjected to repeated trauma with a strain that is less than what would have produced an acute fracture.

With microtrauma, osteoclastic tunnel formation increases to remodel microcracks. New bone formation results in the production of immature, woven bone that lacks the strength of the mature bone it replaced, predisposing the area to fracture with continued trauma.

Stress fractures in older children and adolescents tend to be as a result of athletic participation.

Distal fibula stress fractures have been referred to as the “ice skater’s fracture,” because of the repeated skating motion that results in a characteristic fibular fracture approximately 4 cm proximal to the lateral malleolus.

Clinical Evaluation

Patients typically present with an antalgic gait that is relieved by rest, although younger patients

may refuse to ambulate.

The pain is usually described as insidious in onset, worse with activity, and improved at night.

Swelling is generally not present, although the patient may complain of a vague ache over the site of fracture with tenderness to palpation.

Knee and ankle range of motion are usually full and painless.

Occasionally, the patient’s symptoms and signs may be bilateral.

Muscle sprains, infection, and osteosarcoma must be excluded. Exercise-induced compartment syndrome overlying the tibia may have a similar clinical presentation.

Radiographic Evaluation

AP and lateral views of the leg should be obtained to rule out acute fracture or other injuries, although stress fractures are typically not evident on standard radiographs for 10 to 14 days after initial onset of symptoms.

Radiographic evidence of fracture repair may be visualized as periosteal new bone formation, endosteal radiodensity, or the presence of “eggshell” callus at the site of fracture.

Technetium bone scan reveals a localized area of increased tracer uptake at the site of fracture and may be performed within 1 to 2 days of injury.

Computed tomography rarely demonstrates the fracture line, although it may delineate increased marrow density and endosteal/periosteal new bone formation and soft tissue edema.

Magnetic resonance imaging may demonstrate a localized band of very low signal intensity continuous with the cortex.

Classification

Stress fractures may be classified as complete versus incomplete or acute versus chronic or recurrent. They rarely are displaced or angulated.

Treatment

The treatment of a child presenting with a tibial or fibular stress fracture begins with activity modification.

The child may be placed in a long leg (tibia) or short leg (fibula) cast, initially non–weight bearing with a gradual increase in activity level. The cast should be maintained for 4 to 6 weeks until the fracture site is nontender and radiographic evidence of healing occurs.

Nonunion may be addressed with open excision of the nonunion site with iliac crest bone grafting or electrical stimulation.

Complications

Recurrent stress fractures: These may be the result of overzealous training regimens, such as for gymnastics or ice skating. Activity modification must be emphasized to prevent recurrence.

Nonunion: This is rare, occurring most commonly in the middle third of the tibia.