Congenital Pseudarthrosis of the Clavicle: A Case Presentation and Review of the Literature

Robert S. Adelaar, M.D. James R. Urbaniak, M.D.


Congenital pseudarthrosis of the tibia is frequently encountered by members of children's amputee clinic teams. On the other hand, congenital pseudarthrosis of the clavicle is rarely seen, yet medical specialists engaged in managing children's limb problems should be aware of this entity. Congenital pseudarthrosis of the clavicle was first described by FitzWilliams in his series of cases demonstrating hereditary craniocleidodysostosis (HCD) in 19105. He described an eight-year-old girl with a defect in her right clavicle but without any other skeletal manifestations. In 1930, Saint-Pierre reported a second case of a female with congenital pseudarthrosis of the right clavicle which was noted shortly after birth9. Since that time, an additional 39 cases of this condition have been reported2,9,11. In the cases described, the abnormality most commonly presents as a painless, cosmetically unappealing mass which occurred over the right clavicle in all but one case12. Congenital pseudarthrosis is usually noted before the age of nine years, and often immediately after birth.

Clinical Syndrome

The clinical syndrome is characterized by a nontender mass over the middle one-third of the right clavicle which demonstrates a variable degree of nontender motion. A constant relationship between both fragments is usually found with the larger sternal fragment anterior and superior to the medial portion of the distal segment which is directed medially, superiorly and posteriorly. The acromial segment would be directed inferiorly and anteriorly due to the weight of the upper limb. The ipsilateral shoulder is anterior and medial, and the posterior scapular border is usually prominent2,5,9. Radiographic analysis reveals a separation in the mid-third of the clavicle with both fragments characteristically having round, smooth edges.

There has been no evidence of hereditary predisposition to this condition. The most feasible theory, proposed by Grueneberg7, postulates a hormonal or environmental disruption of the developing limb bud. Since both clavicles are not affected equally, and there are no other systemic manifestations, he felt that mutational changes in genes could not be responsible.

The pathological findings at surgery have been described by Allred2 and Jinkins8 as a true pseudarthrosis with cartilage covering the bone ends. Synovial fluid is present in the capsule encasing the pseudarthrosis. The sternal end is always larger than the acromial end, and the pseudarthrosis is usually located lateral to the center of the right clavicle.

Etiology

Consideration of the embryological development of the clavicle as presented by Fawcett4 is necessary in attempting to advance a plausible cause for this condition. The stages of development of the clavicle are as follows: at the 11-mm. (crown to rump) stage, the clavicle is entirely composed of connective tissue; at the 15-mm. stage (Fig. 1 ), two distinct layers exist-an outer connective tissue jacket and two precartilage centers; at the 17-mm. stage (5 to 7 weeks), the cartilage centers start to undergo ossification with the sternal end being slightly advanced in calcification as compared to the acromial end; at the 19-mm. stage, a precartilage bridge between the two centers begins to ossify and is completed by the forty-fifth day (see Fig. 1 and Fig. 2 ) although the osseous connection remains tenuous for a long period of time. Grueneberg7 has astutely proposed that, at this stage, a hormonal or mechanical environmental influence on this precartilage connection is responsible for incomplete ossification, and pseudarthrosis of the clavicle occurs.

Differential Diagnosis

The differential diagnosis of this condition includes hereditary cranioclei-dodysostosis, birth fracture, nonunion of a fractured clavicle and neurofibromatosis. Hereditary craniocleidodysostosis is a familiar disorder first described by Martin in 1765 and is characterized by defects in ossification of the membranous bones. The commonly described skeletal manifestations are: clavicular and pelvic ring abnormalities in development, frontal bossing, wide fontanelles, dental anomalies, and epiphyseal disorders of the hands and feet3. Hereditary transmission is thought to be autosomal dominant with variable penetrance12. Therefore, there can be many form fruste of the condition with the most common presentation of the clavicular disorders being total absence of the clavicle. Other forms are an absent acromial segment, or a mid-clavicular defect bridged by a fibrous band. The latter type most closely simulates congenital pseudarthrosis of the clavicle. This syndrome can be observed with equal frequency in either clavicle, or both. Roentgenograms of the skull and pelvis are useful in differentiating this syndrome from congenital pseudarthrosis. In addition, a dimple over the clavicular defect rather than an elevation is usually apparent. In HCD. associated defects in the clavicular portion of the trapezius and anterior deltoid muscle often occur. The clinical presentation of HCD is characterized by a slender build, large head, shrunken face, long neck, winged scapula, an abnormal spinal curvature and drooping shoulders. Typically the child has a normal mentality3.

A birth fracture is usually associated with limited and painful shoulder-girdle motion, and often manifests as a pseudoparalysis of the upper limb. Exuberant callous formation occurs with a birth fracture that persists as a nonunion. The fracture is usually of the greenstick type and associated with a difficult labor.

Pseudarthrosis of the long bones occurs in patients with neurofibromatosis or von Recklinghausen disease. The defect has been described as an intermingling of neural with osteoid tissue to produce poorly calcified and disorganized osteoid. Development of an interosseous neurofibroma from a nerve as it enters the bone and atypical nerve stimulation producing abnormal growth have been reported as causes of the pseudarthrosis1,6. The tibia is the most common site of pseudarthrosis in neurofibromatosis. Radiographic examination reveals tapered bone fragments with sclerotic edges in contrast to the large smooth ends found in congenital pseudarthrosis of the clavicle. Other manifestations such as café-au-lait spots and extraosseous tumors help to establish the diagnosis of neurofibromatosis.

Case History

S.N. is a 2 1/2-year-old male product of a normal pregnancy and a full-term vertex delivery without any evidence of trauma at birth or complications immediately postpartum. The child was evalualed in the Duke Children's Upper-Limb Clinic for a painless mass over the right clavicle which was noted a short time after birth- The parents believed that the mass had increased in size and were concerned about the drooping of the right shoulder (Fig. 3 and Fig. 4 ). This child had normal use of the right upper limb. The family history was negative with respect to any congenital anomalies.

Physical examination revealed a well-developed black male with no asymmetry or enlargement of the skull. A nontender mass measuring 2 1/2 x 4 cm. was present over the right midclavicular region with obvious motion in the area of the mass on shoulder movements. The right shoulder, which had a normal range of motion, was positioned slightly anterior, medial and inferior. No café-au-lait spots or extraosseous masses were present (Fig. 3 and Fig. 4 ).

Radiographic examination revealed a pseudarthrosis of the mid-clavicle. The fragments had large, smooth borders, and the sternal portion was larger (Fig. 5 ). No skull abnormalities were noted.

Serial examinations have revealed minimal motion at the pseudarthrosis site. There has been no appreciable increase in the size of the mass. The limited mobility of the pseudarthrosis in this patient is a good prognosis sign. Because of the favorable signs of the small mass, minimal motion of the pseudarthrosis, and normal shoulder motion, our treatment plan has been one of careful observation.

Discussion

The clavicle is one of the first bones to ossify and one of the few to do so by in-tramembranous ossification. The clavicle functions as a rigid base for muscle attachments, a structural support for the glenohumeral joint, and a vehicle to increase shoulder range of motion and range of grasp. The clavicle also protects the major neurovascular structures, as well as providing a cosmetically graceful curve to the upper torso10. Congenital pseudarthrosis of the clavicle may cause some limitation of shoulder-girdle function. Pain or symptoms of neurovascular compression do not occur. Cosmetic disfigurement is the principal, and often the only, affliction.

Methods of management of this condition are nearly as varied as those of congenital pseudarthrosis of the tibia. Allred2 emphasized in a review of nine patients that the deformity progressed and resulted in functional disability of the ipsilateral shoulder and cosmetic deformity with its associated adverse psychological effects. He further stressed that the degree of severity of the deformity was directly related to the amount of motion at the pseudarthrosis. In no instance did union occur without bone grafting, which was performed up to eight years of age. Allred mentioned the optimal age for grafting as being in the two- to four-year-old period. In girls over eight years of age, trimming of the mass was the only treatment recommended. Jinkins8 also proposed early stabilization as the treatment of choice.

Wall12, on the other hand, did not think that there was any indication for stabilization in his series of four patients on whom he had a reasonably long follow-up. The clavicular mass did not increase appreciably, and there was no progression in the deformity of the shoulder girdle.

Treatment depends on the severity of the deformity and the age and sex of the child. The patients who initially have no alteration in shoulder-girdle biomechanics, or severe cosmetic deformity, should be observed periodically. Patients who demonstrate increasing mobility of the clavicular pseudarthrosis. a poor prognostic sign, must be watched closely. If increased cosmetic deformities develop (especially in females) and alteration of shoulder-girdle function occurs, surgical Stabilization should be performed before the age of eight years. A cosmetic deformity in a female over eight years of age can be treated with local excision only. The recommended surgery would be resection of the pseudarthrosis and stabilization by an onlay autogenous iliac bone graft and K-wire or screw fixation. The hardware should be removed after the fusion is complete. Unlike congenital pseudarthrosis of the tibia, the surgical fusion is usually successful; especially between ages two to four years2,8.

Summary

Congenital pseudarthrosis of the clavicle is rare. The anomaly usually occurs in the right clavicle and is manifested by a painless and cosmetically unappealing mass. The greater the motion at the pseudarthrosis, the greater is the cosmetic deformity. The defect apparently occurs from an abnormal stimulus during the forty-fifth day of fetal development. A case report has been presented and a differential diagnosis discussed. Treatment should be observation in those cases with a mild deformity, and surgical resection and stabilization in those with a severe deformity, with the surgery performed before the age of eight years.

Division of Orthopaedic Surgery Duke University Medical Center Durham, North Carolina

References:
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