Background CPT occurs in fewer than 1 in 140,000 children.3 The etiology of CPT cannot be determined in all cases. Suggestions that CPT results from intrauterine or birth trauma, metabolic disease, or vascular malformation are not fully substantiated.4 In 55% of cases, CPT has been linked to neurofibromatosis (NF).4 NF is an autosomal dominant disorder that affects neural crest cells and results in tumors along nerve pathways. There are two types: NF-1 and NF-2. NF-1 has more generalized effects, whereas NF-2 is related to acoustic neuromas. NF-1 can result in multiple subcutaneous masses, nerve-root compression, skeletal problems, and pigmentation abnormalities related to melanocyte dysfunction. The diagnosis is secured by the presence of two of the following seven characteristics: more than two neurofibromas under the skin, freckles in the groin or axillae, skeletal abnormalities, spotted irises, optic-nerve tumors, a first-degree relative with NF, or six café au lait spots larger than 5 mm.3 Although our patient did not have two clinical features for NF, we sent him for genetic testing to rule out NF-1. Test results were negative.
We also sent our patient for advanced imaging to further define the lesion. Rather than expose him to additional radiation with CT, MRI was performed under anesthesia with and without contrast (Figure 2). All bone tumors have good vascularity and thus enhance with contrast, so some experts have suggested that contrast is unnecessary for evaluating bone tumors. On the other hand, contrast can help distinguish between the mass and bone marrow edema. An area of marrow edema larger than the area of the lesion itself increases the likelihood that the process is benign.5 Additionally, benign tumors should be well-defined and have no soft-tissue involvement.
Various classification systems for CPT exist, but the one most frequently used is the Crawford system.3 The two types of CPT are nondysplastic (type 1) and dysplastic (type 2). The nondysplastic type is characterized by bowing, increased cortical density, and a narrowed medullary canal. Patients with type 1 CPT have a good overall prognosis. There are three subclasses of dysplastic CPT (A, B, and C), which progress in severity from a widened medullary canal to a cystic lesion to a full defect in the shaft and abutting tapered fragment ends. A type C pseudarthrosis is the worst-case scenario and has the poorest prognosis for healing.
Treatment Healing of CPT is often tenuous, so treatment is difficult. Multiple techniques have been implemented; however, recurrence is frequent regardless of the method used. Intramedullary rodding, external fixation, bone grafting, fibular transfers, and various combinations of these methods have been applied in the treatment of CPT.4,6,7 In some cases in which attempts at union are repeatedly unsuccessful or the deformity of the limb is too great, amputation is offered to provide a higher level of function to the patient.2 In this case, the baby's leg was placed in a knee-ankle- foot orthosis with a clamshell tibia component in order to increase support across the defect. If the CPT does not heal on its own, then bone grafting with fixation will be necessary in the future. JAAPA
Jason Smith practices at Shriners Hospital for Children in Philadelphia, Pennsylvania. Richard Davidson is an orthopedic surgeon at The Children's Hospital of Philadelphia. The authors have indicated no relationships to disclose relating to the content of this article.
Julie Vajnar, PA-C, RT, department editor
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