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.

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.

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.

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.

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).

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.