Pediatric Tibia and Fibula Fractures
"Pediatric tibia and fibula fractures: epidemiology, anatomy, mechanism of injury, clinical evaluation, radiographic evaluation, classification, treatment, and complications."
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.