Congenital pseudoarthrosis of the clavicle is a rare anomaly and was first described by Fitzwilliams in 1910.
Congenital pseudoarthrosis of clavicle results in congenital failure of formation [ossification] of the central portion of the clavicle that manifests as a painless lump in the clavicle.
Functional impairment is uncommon in children.
The pseudoarthrosis is fully present at birth.
Familial incidence is reported in some patients, particularly in bilateral cases.
The right clavicle has been affected in almost all the reported cases.
Etiology of Pseudoarthrosis of Clavicle
Clavicle connects the sternum to the acromion and provides support for shoulder function. The clavicle is the first bone of the skeleton to become ossified in the fourth week of gestation, and fusion of the two ossification centers occurs around the seventh week.
Disruption of membranous ossification due to environmental insult or anatomic or mechanical event is the main reason behind the development of congenital pseudoarthrosis of the clavicle.
The cause is not known though abnormalities in aortic arch angiogenesis have been postulated. The incidence of associated cervical ribs is 15%.
Excessive pressure exerted by pulsation of the subclavian artery during the process of development of the clavicle, abnormal intrauterine position, and genetic causes have been suggested as possible causes.
It must be noted that the defect is not due to nonunion of a birth fracture of normal bone as all neonatal clavicular fractures unite rapidly with massive callus.
Presentation of Congenital Pseudoarthrosis Of Clavicle
A nontender swelling just lateral to the middle of the clavicle is discovered at birth or soon afterward. There is no history of birth injury or other trauma.
At the site of pseudoarthrosis, the adjacent ends of the clavicular fragments are enlarged, and there is a variable degree of painless mobility between them. The larger sternal fragment is tilted upward and lies in front of and slightly above the medial end of the smaller acromial portion.
The deformity tends to become more obvious with the child’s growth. Pseudoarthrosis may become painful with some activities that involve movements above head level or with direct compression of the focus.
The deformity usually increases and becomes unsightly with further growth, more so when there is marked mobility at the site of the pseudarthrosis. The overlying skin becomes thin and atrophic. Cosmetically the deformity may be a source of embarrassment to the child.
There is some drooping of the affected shoulder with asymmetry and prominence of the vertical border of the scapula. Mild pain around the shoulder girdle and upper arm may be present.
There is little or no functional disability. A few children complain of weakness of the arm and limitation of shoulder abduction.
The radiographic findings are characteristic and include clear separation in the middle portion, with the medial fragment positioned above the lateral fragment because of the action of muscle forces and the postural traction exerted by the weight of the upper limb.
Because of the weight of the upper limb, the lateral segment of the clavicle is tilted inferiorly, the shoulder droops, is rotated forward and is nearer to the midline than the opposite normal side.
In congenital pseudoarthrosis of the clavicle, there are no other skeletal abnormalities present, a feature that distinguishes it from cleidocranial dysostosis.
MRI is rarely indicated but may be used to determine the extent of the fibrous union, the location of the great vessels, and the space available within the thoracic outlet.
Treatment of Congenital Pseudoarthrosis Of Clavicle
No conservative treatment achieves the union and not all the cases require surgical treatment. Indications for operative treatment are the progressive pain, unpleasant deformity, functional limitation, and late-starting thoracic outlet syndrome.
Treatment consists of excision of the pseudoarthrosis mass, curettage of the bone ends, internal fixation with a threaded Steinmann pin or semitubular plate and grafting with cancellous onlay autogenous bone graft from the ilium.
Image Credit: Eorif