Associated malformations are almost always present with a Sprengel deformity. These can include anomalies in the cervicothoracic vertebrae or the thoracic rib cage. The most common anomalies are absent or fused ribs, chest wall asymmetry, Klippel-Feil syndrome, cervical ribs, congenital scoliosis, and cervical spina bifida. When scoliosis is present, the most common curves are in the cervicothoracic or upper thoracic region. A relationship between a Sprengel deformity and diastematomyelia has also been shown. Renal anomalies occur in one third of patients. In some patients, an osseous and cartilaginous structure called an omovertebral bone originates in the upper part of the scapula and attaches to the spinous process of a cervical vertebra. This abnormal bar, occasionally in combination with contracture of the levator scapulae muscles, may further limit scapular motion. This omovertebral bone is best visualized on a lateral or oblique radiograph of the cervical spine.

If the deformity is severe enough to warrant surgical intervention, surgery provides considerable cosmetic benefit in appropriately selected patients. It restores a more natural contour to the shoulders and neck and also produces an apparent increase in neck length. The affected shoulder, however, remains smaller. Surgery is indicated for children between 3 and 8 years of age with significant deformities, both functional and cosmetic. Patients older than 8 years of age are not good candidates for scapular displacement procedures, because there is an increased risk of injury to the brachial plexus from stretching or compression by the clavicle. Removal of an omovertebral bone may increase neck and shoulder motion.

CONGENITAL ABSENCE OF CLAVICLE (CLEIDOCRANIAL DYSOSTOSIS)

A hereditary congenital disorder, absence of the clavicle is due to haploinsufficiency caused by mutations in the CBFA1 gene, which is located on the short arm of chromosome 6. It is usually inherited in an autosomal dominant fashion, but in some cases the cause is not known. This defect results in incomplete formation of the clavicles, skull, and pubis and in some patients involves other skeletal structures as well. The entire clavicle may be absent, or simply a small segment of the middle or outer portion may be missing. The defect is bilateral in 82% of patients. Delayed closure of the cranial sutures and fontanelles and incomplete development of the pubis are frequent major manifestations. The defect in the pubis may be quite alarming and has been mistaken for erosion by a tumor.

Scoliosis and anomalies of the mandible, teeth, and small bones of the hands and feet occur in severely affected patients. The typical patient has a large head, small face, long neck, drooping shoulders, narrow chest, and short stature. In most patients, the condition is not disabling.

CONGENITAL PSEUDARTHROSIS OF CLAVICLE

A rare condition, congenital pseudarthrosis usually occurs in the middle third of the clavicle, owing to failure of union between the medial and lateral ossification centers. The nonunion is present at birth and does not heal spontaneously. Recent studies indicate that the condition occurs most often on the right side, and the lesion may thus be due to pressure on the developing clavicle by the subclavian artery, which is normally at a higher level on the right side. The deformity may become larger and more obvious as the child grows, with a false joint developing between the enlarged ends of the clavicular fragments. The affected shoulder tends to droop forward and lower nearer the midline than the normal shoulder. The condition may be confused with a simple fracture, cleidocranial dysostosis (Plate 4-28), or neurofibromatosis (see Plates 4-20 to 4-23). The enlarged ends of the clavicular fragments are palpable, and there is a variable degree of painless motion between them. Functional problems are rare, and surgery is recommended only for patients who have pain, an unsightly lump, or shoulder weakness.