Tibia and Fibula



Tibia and Fibula


Andrew Pennock

Maya Pring



INTRODUCTION

Tibia and fibula shaft fractures heal so much more readily in children than in adults that they should be a joy to treat. The majority of children have a cast applied and only require a cast shoe and a note for school outlining their limitations.

Most tibial fractures in children are stable, and the child can soon be weight bearing in an above knee (long leg) cast. However, there is more variation to these fractures than is generally realized. If foresight is to be used to prevent problems in treatment, the characteristics of the fracture should be well understood. In this chapter, we will present tibia and fibula shaft fractures and discuss common variations according to their anatomic location. Proximal tibia epiphyseal fractures including tibial tubercle fractures are discussed in Chapter 14, and distal tibia epiphyseal fractures are discussed in Chapter 16.

“The beautiful thing about learning is nobody can take it away from you”

B.B. King







Figure 15-1 Congenital pseudoarthrosis of the tibia and fibula. This should not be confused with an acute fracture.


ASSESSING THE PATIENT

A non-walking child with a tibia fracture should always alert you to think about non-accidental trauma or child abuse. Make sure the described mechanism is consistent with the fracture. If there is any concern, have social work evaluate the child and family.

Evaluate the x-rays carefully as pseudoarthrosis of the tibia may be seen in very young children with no trauma—this can indicate underlying pathology such as neurofibromatosis. Look for tapered bone ends, smooth/sclerotic non-healing ends of the bone (Fig. 15-1).

Toddlers often have a twist and fall and sustain low-energy non-displaced spiral fractures. The child with a fracture will be exquisitely point tender at the location of the fracture and usually will not walk. A child that will crawl but will not walk likely has pathology below the knee. X-ray may not show the fracture initially, so a careful exam is important. If there is not a clear fracture on x-ray, think about infection as metaphyseal osteomyelitis is not uncommon in children. Leg pain is also a classic presenting complaint for children with undiagnosed leukemia. Do not assume there is a fracture just because there is a history of fall—if you don’t see it, consider labs including CBC with differential, CRP, and ESR.

As children get older and become adolescents, more force is necessary to fracture the tibia and soft tissue injury becomes more of a concern. For high-energy injuries, monitoring for compartment syndrome is critical. We admit all tibia fractures over the age of 6 for monitoring following reduction. One of the predictors of compartment syndrome after tibial fracture is age of the patient. In a study of 1,388 patients, McQueen showed the highest prevalence of compartment syndrome was between 12 and 19 years of age—youth was the strongest predictor of developing compartment syndrome.






Figure 15-2 Neurovascular anatomy inferior to the knee joint.



ANATOMY

The tibia is subcutaneous for most of its length, so displaced fractures can be easily identified. Because of the lack of soft tissue over the medial face, open fractures are more common than with other bones with a good soft tissue envelope; look carefully for the grade I open inside to outside fracture. Even if the fracture is not open, the skin is easily compromised and may subsequently necrose, so we recommend reducing a displaced tibia fracture sooner rather than later to protect the soft tissues.

The popliteal artery trifurcation is firmly adherent to the posterior aspect of the proximal tibia and is at risk of injury with more proximal fractures. The anterior tibial artery passes over the proximal edge of the interosseous membrane into the anterior compartment and is closely applied to the tibia. Because of this fixed position, the artery may be compressed, stretched, or torn. The peroneal nerve wraps around the proximal fibula and is at risk of injury with proximal fibula fractures (Fig. 15-2).

There are four muscle compartments in the leg: anterior, lateral, posterior superficial, and posterior deep (Fig. 15-3). The leg is the most common site to develop compartment syndrome following injury including tibia and fibula shaft fractures—see Chapter 19 for more information on identifying and treating compartment syndrome.




CLASSIFICATION

Physeal and intra-articular fractures at the knee and ankle are reviewed in Chapters 14 and 16 respectively. The majority of tibial fractures are isolated; 30% will have an associated fibula fracture. Tibia and fibula shaft fractures in children are classified by location (proximal—metaphyseal, shaft, distal—metaphyseal), and type of fracture (buckle, greenstick, spiral, oblique, transverse, comminuted) (see Chapter 1).






Figure 15-3 The four compartments of the lower leg.






Figure 15-4 Pathologic fracture through tibial non-ossifying fibroma.




PROXIMAL METAPHYSEAL FRACTURES

Often masquerading as “innocent little cracks,” neglected or missed proximal metaphyseal fractures can lead to significant problems for the patient. Two distinct types of fracture occur in this region, each with its own distinct set of complications.


Cozen Fracture

Metaphyseal greenstick fractures in children between the ages of 3 and 10 years are known as Cozen fractures. A valgus-directed force causes the medial cortex of the proximal tibia to open slightly. The x-ray angulation is typically unimpressive, and most of these fractures are accepted and are casted in situ following the adage that children’s fractures, particularly in younger children, can be expected to remodel and do not require exact angular correction. When the cast is removed, the child holds the leg flexed making it difficult to see hip to ankle alignment, so it is difficult to know if the leg is in valgus to start and/or if the leg subsequently grows into valgus (Fig. 15-5). It may be a combination of these two factors, but it is important to remember (and warn the parents) that Cozen fractures are known for late valgus deformity. Luckily, this usually resolves without intervention, but the broken leg may appear more knock-kneed for a year or two, which can be quite upsetting to the parents. If the deformity does not resolve with growth, these fractures happen in a young enough age group that guided growth is an option for correcting valgus before skeletal maturity. Very rarely, osteotomy of the tibia may be needed to restore alignment.






Figure 15-5 Progressive deformity following a Cozen fracture.


Why Progressive Valgus?

Several studies have suggested that the valgus was due to overgrowth of the medial tibia because of fracture hyperemia while the intact fibula acted as a tether. Aronson found that dividing the periosteum around the medial half of the proximal tibia in animals produced
valgus deformity. This may be due to mechanical release of the restraint the periosteum imposes on the growth plate. Likely the mechanism is multifactorial.

It has been our experience that if the fracture is anatomically reduced, significant late valgus is less likely. Sometimes anatomic reduction requires completing the fracture, and on occasion, the medial gap cannot be reduced by closed manipulation because of soft tissue interposition. Both the lower part of the pes anserinus and the thick periosteum avulsed from the lower fragment can be entrapped (Weber). In this instance, open reduction is needed to ensure reduction. Once open reduction is performed, the fracture is usually pinned to maintain reduction.


Complete Proximal Tibia Metaphyseal Fractures

The anterior tibial artery passes over the proximal edge of the interosseous membrane into the anterior compartment and is closely applied to the tibia (Fig. 15-6). Because of this fixed position, the artery may be compressed, stretched, or torn. The initial sign of vascular damage may be a cold, pale, pulseless leg that in about an hour becomes anesthetic and paralyzed, but often the findings are more subtle and appear slowly. Muscle ischemia alone is less dramatic; warm skin has misled many.

With a proximal fibular fracture, the temptation to blame calf and foot neurologic signs of ischemia on local peroneal nerve damage should be resisted. Arterial compromise and/or compartment syndrome must be suspected. Reduction is urgent because correction of the displacement and angulation may restore the circulation. An arteriogram or MR angiogram may be helpful but should not overly delay intervention. If an arterial repair is performed or compartment syndrome is diagnosed, four compartment fasciotomies should be performed with internal fixation of the fracture to protect the soft tissues (including the vascular repair) from further trauma.


DIAPHYSEAL FRACTURES


Toddler’s Fracture

Children under the age of 2 years may present with a painful limp or refusal to walk because of an occult tibia fracture. The injury may or may not have been witnessed. Toddlers often fall, and a rotational stress can cause an oblique distal tibia fracture or spiral non-displaced shaft fracture.

For a limping child with a suspected toddler’s fracture, the examination should start on the uninvolved side to provide a comparison for the symptomatic extremity. Examine the area you think is broken last — once you make the child cry, the rest of the exam is very difficult.






Figure 15-6 Proximal tibial metaphyseal fractures put the anterior tibial artery at risk.







Figure 15-7 Toddler’s fracture. The oblique fracture line on the injury film is very hard to see. The child was treated with a long leg cast. Three weeks later, the presence of healing callus confirms the diagnosis.

Gently palpate the foot and examine for any swelling or ecchymosis. Palpate the knee and thigh and log roll the hip; if you grab the tibia to rotate the hip, you will cause pain and may mistakenly think the problem is more proximal.

AP and lateral radiographs of the tibia and fibula should be obtained but are often normal. The fracture may not be visible on the initial radiographs especially if the injury is less than a week old.

If a toddler’s fracture of the tibia is suspected but the x-ray is normal, we usually get a CBC with differential, ESR, and CRP to rule out infection and leukemia. If the laboratory studies are normal we then apply a walking cast for 3 weeks. Repeat radiographs in 3 weeks will often show periosteal new bone formation, which helps to confirm the diagnosis (Fig. 15-7).


Diaphyseal Fractures in the Child and Adolescent

With an intact fibula, a tibia fracture may go on to varus deformity with posterior bowing unless the cast is molded into valgus with added posterior molding to prevent recurvatum (Fig. 15-8). The bowing may not be apparent on initial films but commonly develops in the course of 2 or 3 weeks if the cast is not suitably molded. It is a deformity more easily prevented than corrected.

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Nov 17, 2018 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Tibia and Fibula
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