DEFORMITIES OF THE CLAVICLE AND SHOULDER
Congenital Pseudarthrosis of the Clavicle
Idiopathic congenital pseudarthrosis of the clavicle refers to the presence of a fibrous tissue-filled gap within the clavicular shaft in a patient with no evidence of fibrous dysplasia or neurofibromatosis. There are hyaline cartilage caps at the bony margins of the defect, with fibrocartilage occupying the remainder of the defect. Congenital pseudarthrosis of the clavicle almost always occurs on the right or is bilateral (10%). Isolated involvement of the left clavicle is usually accompanied by situs inversus and dextrocardia. Cervical ribs occur with an increased frequency in these patients. Rarely, a familial occurrence is present.1,2
The pathogenesis of congenital pseudarthrosis of the clavicle may involve bony resorption due to pulsation of a nearby artery in the developing fetus. Other postulated pathophysiologic etiologies include failure of coalescence of the 2 centers of clavicular ossification or a defect in the primary ossification center of the clavicle. The most common clinical presentation is that of a painless lump of the midportion of the clavicle. (Pain is common in patients with nonunion of a clavicle fracture.) Rarely, there are symptoms of thoracic outlet syndrome.3
Congenital pseudarthrosis of the clavicle appears radiographically as a defect in the midportion of the clavicle, typically at the junction of the mid and lateral thirds (Figure 58-1). There is no visible callus formation. The margins of the defect are well corticated and rounded. The ends of the bones often are somewhat enlarged, particularly in older patients. The lateral segment of the clavicle often has a curved appearance, and is sometimes hypoplastic. The medial segment of the clavicle almost always is superior to the lateral segment, and there usually is slight overriding. An ipsilateral cervical rib is present in some patients.4
Congenital pseudarthrosis of the clavicle in 4 different children.
A. The bony margins of the clavicular defect in this 3-dayold infant are smooth and slightly sclerotic. There is slight overriding. B. A large ipsilateral cervical rib is present in this 9-month-old. C. The lateral segment of the abnormal clavicle has a curved appearance in this 15-year-old patient. D. The portions of the clavicle adjacent to the defect are somewhat enlarged and irregular in this 17-year-old patient.
Additional considerations in the differential diagnosis of clavicle defects are cleidocranial dysplasia and posttraumatic pseudarthrosis. The clavicular defects of cleidocranial dysplasia are almost always bilateral. The gaps tend to be wider than in congenital pseudarthrosis. The remaining portions of the clavicles are often somewhat hypoplastic. There are also coexistent deformities elsewhere in the skeleton (see Chapter 57 for additional discussion of cleidocranial dysplasia). With posttraumatic pseudarthrosis, the bone ends are usually bulbous due to exuberant callus formation. These patients typically have pain with palpation ...