Congenital Pseudoarthrosis of Clavicle 

Updated: May 07, 2018
Author: L Andrew Koman, MD; Chief Editor: Jeffrey D Thomson, MD 

Overview

Background

In 1930, Saint-Pierre reported congenital failure of clavicle formation. In 1963, Alldred reported nine cases of congenital pseudoarthrosis of the clavicle.[1] Congenital failure of formation (ossification) of the central portion of the clavicle produces a painless prominence in the anterior superior chest in the absence of trauma.[2, 3] The resultant synovial pseudoarthrosis usually develops on the right side. Functional impairment is uncommon in children. A case of pseudarthrosis of the clavicle causing thoracic outet syndrome is reported.[4]

In patients with congenital pseudoarthrosis of the clavicle, a painless mass over the right clavicle is the most common finding that prompts parents to seek consultation with a physician. Treatment may consist of mere observation or resection of the pseudoarthrosis and osteosynthesis.[5, 6, 7, 8, 9, 10, 11] Surgical intervention generally is recommended, to correct shoulder girdle hypermobility and an unsightly mass. Both problems can be treated by means of open reduction, resection of the pseudoarthrosis, and bone grafting.[8] Resection alone produces pain.

Pathophysiology

The clavicle is the first bone to undergo membranous ossification. It connects the sternum to the acromion and provides support for shoulder function. Congenital pseudoarthrosis of the midportion of the clavicle occurs when an environmental insult or anatomic or mechanical event disrupts diaphyseal membranous ossification.

In congenital pseudoarthrosis of the clavicle, the two primary ossification centers fail to unite. The two portions of the clavicle produced are connected by a fibrous bridge that is contiguous with the periosteum, and a synovial membrane develops.[6] The predominance of right-side involvement in the absence of situs inversus suggests that the vascular anlage of the subclavian artery that crosses the first rib just below the pseudoarthrosis site may be involved in the etiology.

Congenital pseudoarthrosis has never been associated with malignant degeneration.

Etiology

The etiology is unknown, and no relation to neurofibromatosis has been demonstrated. Abnormalities in aortic arch angiogenesis have been postulated, which would explain, in part, the right-side distribution. Failure of coalescence of the two primary ossification centers contributes to the pathology.[12] Left-side involvement is seen in patients with dextrocardia and situs inversus. The incidence of associated cervical ribs is 15%. Spontaneous healing is extremely rare.

Epidemiology

Congenital pseudoarthrosis is rare. Fewer than 200 cases have been reported in the English literature. The exact incidence and prevalence are unknown. The abnormality occurs almost entirely on the right side. Involvement of the left side usually occurs with dextrocardia and situs inversus.[13] Bilateral cases can occur but are rare and are typically associated with genetic syndromes.[14, 15]

Prognosis

The outcome is usually excellent, with prompt healing, few complications, and normal function.

 

Presentation

History and Physical Examination

A painless mass or swelling over the clavicle is the usual presenting concern. The patient has no history of trauma, and shoulder and arm movement are normal. A family history of similar deformities is rare. Neurofibromatosis rarely is an associated diagnosis. In older children, pain is infrequent but may occur.

In the typical presentation, the larger sternal side is tilted anteriorly and superiorly, and the smaller acromial portion curves gently to meet the pseudoarthrosis. The mass usually is painless, range of motion is full, and function is normal. Café au lait lesions typically are not seen.

 

Workup

Approach Considerations

Generally, laboratory studies are not necessary. Genetic testing is indicated in bilateral cases in which a syndrome is suspected. Imaging studies may be helpful (see below). Histologic findings consist of synovial-lined pseudoarthrosis.[12]

Imaging Studies

On plain radiography, anterior, posterior, and apical lordotic views usually are sufficient.[16] Pseudoarthrosis of the midclavicle on the right is easily visualized and has a characteristic pattern, with anterior and superior tilting of the sternal half and a smaller acromial portion.

Magnetic resonance imaging (MRI) 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. MRI is rarely indicated in this setting.

 

Treatment

Approach Considerations

Indications for intervention include pain, shoulder girdle instability that interferes with function, and altered self-esteem secondary to an unsightly appearance.[17] No major contraindications to intervention exist. However, internal fixation may be compromised by the size of the patient (and the clavicle).

In the future, the true etiology of congenital pseudoarthrosis may be delineated, and its predilection for the right chest will be understood. It is likely that injection with osteoinductive material will convert the pseudoarthrosis to normal membranous ossification or that the application of external bone-stimulating devices will induce osteoprogenitor cells to replace the pseudoarthrosis with normal bone.

Medical Therapy

Mere observation may be appropriate. No nonoperative techniques achieve union.

Surgical Therapy

Treatment with resection of the pseudoarthrosis, primary approximation of the ends of the clavicle or the use of autologous graft (eg, iliac crest), and rigid fixation with a plate and screws has yielded reliable results.[18, 19, 20] Poor results with the use of bovine cancellous xenograft (Tutobone) have been reported[21] ; this should be avoided because of reaction, nonunion, and difficulty achieving union. A case report details salvage with a vascularized bone graft.

Operative details

After taking a general history and performing a physical examination, evaluate the right upper extremity for range of motion (ROM), stability, and neurovascular function. The patient should be prepared for surgery, and the entire right upper limb should be prepared free to facilitate mobilization of the clavicle and to observe for neurovascular problems. Prophylactic antibiotics are appropriate if internal fixation is employed. A semisitting or beachchair position may be helpful to obtain exposure.

Surgical steps are as follows:

  • Expose the clavicle through a transverse incision
  • Control bleeding with electrocauterization
  • Expose the medial and lateral clavicle subperiosteally, excise the sclerotic ends, and resect the pseudoarthrosis
  • Determine if end-to-end repair is possible [22] ; if not, use a bone graft; do not use bovine xenograft (Tutobone)
  • Apply an appropriate-sized compression plate [23]
  • Reapproximate the periosteum
  • Close the wound in layers

Postoperatively, the patient is immobilized in a sling and swath; alternatively, a shoulder spica cast may be used for small children if internal fixation is inadequate.[24] The clavicle is protected until union is confirmed clinically and radiographically.

Complications

The major surgical complication is failure of the clavicle to unite.[25] However, in contradistinction to congenital pseudoarthrosis secondary to neurofibromatosis, union is common. Fixation with a plate and screws is superior to the use of threaded pins.[26]

Hardware is removed if painful or unduly prominent. Neurovascular injury is rare but may occur. Infection may occur in the postoperative period.