Benign primary bone tumors, including osteochondromas, rarely occur in the clavicle. We report an atypical case in which an osteochondroma developed in the medial part of the clavicle and caused thoracic outlet syndrome with primary subclavian vein thrombosis (Paget-Schroetter syndrome), brachial plexus paresthesias, and mechanical sternoclavicular pain in an otherwise healthy young man. To our knowledge, we are the first to report a case of thoracic outlet syndrome that was caused by an osteochondroma of the medial part of the clavicle. The two other medial clavicular tumors that have been reported in the literature were asymptomatic1,2. We present the natural history of this lesion and report the outcome after local excision through a clavicular osteotomy followed by internal fixation. We also discuss clavicular embryology and speculate on the pathoanatomic origin of a medial clavicular osteochondroma. The patient and his family were informed that data concerning this case would be submitted for publication.
Case Report
A sixteen-year-old male high-school student who worked part-time as a butcher presented to a vascular surgeon with a six-week history of insidious swelling in the left, nondominant arm. The patient also complained of diffuse brachial plexus paresthesias. He smoked one pack of cigarettes per year but was otherwise healthy. A laboratory evaluation for thrombophilia revealed normal findings. The family history was negative for hereditary bone tumors and thromboembolism. A venogram revealed complete occlusion of the left subclavian vein along with adjacent partial obstruction of the axillary vein. Increased collateral venous drainage was present, suggesting external compression. This finding was consistent with a primary subclavian thrombosis resulting from thoracic outlet syndrome, also known as Paget-Schroetter syndrome. Routine radiographs of the chest were initially interpreted as normal, although a later retrospective review ultimately revealed the lesion. Magnetic resonance images of the shoulder revealed no obvious extrinsic masses compressing the lateral aspects of the subclavian vessels or brachial plexus, although the medial aspects of these structures were not scanned. However, possible anterior scalene hypertrophy was noted, suggesting a specific type of thoracic outlet syndrome, namely, scalenus anticus syndrome. Thoracic outlet exploration was considered but was not performed given the absence of a definite extrinsic compression etiology. Interventional thrombolysis of the subclavian vein failed because of a technical inability to access the occluded vein. Anticoagulation therapy with Coumadin (warfarin) was instituted for one year, without any change in symptoms; it was stopped thereafter because of its inconvenience to the patient.
Three years after the onset of thrombosis, the patient was working full-time as a butcher and presented to his chiropractor because of new sternoclavicular pain and popping, which worsened with butchering duties that required ballistic overhead movements and heavy lifting. A radiograph of the shoulder revealed a conspicuous sessile osteolytic bone lesion on the medial part of the clavicle, adjacent to the sternoclavicular joint (Fig. 1). A retrospective review of an initial chest radiograph that had been made three years earlier also revealed this same lesion. There had been no obvious radiographic changes during the three-year interval. The patient was referred to the orthopaedic tumor service for further evaluation.
Physical examination revealed engorged veins throughout the proximal aspect of the arm. The range of motion of the shoulder was full. The sternoclavicular joint was tender, without a palpable mass. Forward flexion of the shoulder and adduction of the arm generated an audible and palpable pop over the sternoclavicular joint. The patient had full motor strength, a bounding radial pulse, and diffuse altered sensation throughout the hand and forearm. Adson’s test was positive.
A computerized tomographic scan demonstrated an osseous tumor that was located
Fig. 1
Radiograph showing a central osteolytic bone lesion on the medial aspect of the left clavicle.
The patient elected surgical decompression. An oblique clavicular osteotomy was performed distal and lateral to the lesion. Elevation of the medial clavicular fragment revealed a large, irregularly shaped osseous tumor compressing the neurovascular structures. After elevation of adherent soft tissues, the tumor was excised from the posterior aspect of the clavicle with an oscillating saw. The clavicular osteotomy site was reduced and was secured with lag screw- and-plate fixation (Fig. 3). The tumor measured 3.3 1.6 1.6 cm. The cartilage cap was small and without evidence of malignant transformation. The pathologic diagnosis was benign osteochondroma (Fig. 4).
Soon after surgery, the brachial plexus paresthesias resolved but the subclavian vein thrombosis with postphlebitic syndrome was clinically unchanged. Dilated and tortuous collateral veins persisted over the shoulder.
After three months of shoulder-strengthening rehabilitation, the patient had full range of motion of the glenohumeral and sternoclavicular joints. He no longer had crepitus or sternoclavicular popping. The clavicular osteotomy site was painless and had healed radiographically by three months after surgery, without complications (Fig. 3). The patient resumed light work and activities. Eight months postoperatively, a repeat venogram revealed the persistence of subclavian and axillary vein thrombosis, but with only partial obstructions, indicating some degree of recanalization. As we do not know the precise time when the partial recanalization of the subclavian vein occlusion occurred, we can only surmise that it may have occurred sometime after surgery as a result of the thoracic outlet decompression.
Discussion
We have described a rare case of thoracic outlet syndrome, with axillary-subclavian vein thrombosis and brachial plexus compression, secondary to an atypical medial clavicular osteochondroma. The axillary-subclavian vein has a unique position in the thoracic outlet at the junction of three major anatomic structures: the neck, the shoulder girdle, and the thorax. Our patient’s strenuous overhead work as a butcher probably exacerbated the thoracic outlet compression, causing depression of the shoulder girdle and scissoring the subclavian vein between the clavicular tumor and the first rib3. An extrinsic anatomic compression mechanism is present in most cases of effort-induced subclavian thrombosis, or Paget- Schroetter syndrome4,5. Anatomic sources of this extrinsic compression include congenital clavicular pseudarthrosis, cervical ribs, clavicular nonunion, clavicular malunion, hypertrophy of the scalenus anterior, hypertrophy of the subclavius, a prevenous phrenic nerve, abnormal insertion of the pectoralis minor muscle, clavicular tumors, and an abnormally small space between the clavicle and the first rib6-8.
Fig. 2
Sagittal computerized tomographic scan of the medial part of the left side of the chest, demonstrating an osseous lesion projecting posteriorly from the medial aspect of the clavicle and confirming cortical and medullary continuity between the lesion and the host clavicle.
Fig. 3
Radiograph, made three months after surgery, showing union with stable fixation at the site of the clavicular osteotomy.
According to the Mayo Clinic registry, only 0.5% of about 750 reported solitary osteochondromas were located in the clavicle9. Of the nine solitary clavicular osteochondromas that have been reported in the English-language literature, two developed in the medial third of the clavicle, one developed in the middle third, and six developed in the lateral third1,2,7,10-12. In contrast to the lesion in our patient, both of the other medial clavicular tumors reported in the literature were asymptomatic1,2. However, most lateral clavicular osteochondromas are symptomatic because of either extrinsic mechanical irritation of the rotator cuff or other mechanical alteration of shoulder girdle function1,11,12. Filis et al. reported the case of a patient with thoracic outlet syndrome resulting from a lateral clavicular osteochondroma who was managed with extensive decompression, including tumor excision and anterior scalenectomy7. We believe that primary bone tumors of the clavicle, albeit rare, should be added to the differential diagnosis ofsternoclavicular pain and thoracic outlet syndrome. Our main conclusion based on this rare case is that effective imaging with radiographs, magnetic resonance images, and computerized tomographic scans of the thoracic outlet and the medial part of the clavicle must be performed when there is any doubt about the cause of thoracic outlet syndrome. In the case of our patient, there also could have been a diagnostic role for contrast-enhanced computerized tomographic imaging, which could have been used to directly visualize the osteochondroma that was compressing adjacent contrast- enhanced vessels.
Fig. 4
Photomicrograph revealing some orderly organization of cartilage cells undergoing endochondral ossification (above), with an expected transition to trabecular bone (below). The cartilage cap was typical, small, and without evidence of malignant transformation (hematoxylin and eosin, 4).
Osteochondromas are thought to arise from either trauma or a deficiency in the perichondral ossification groove of Ranvier. Since this tumor arises in association with physeal growth, bones developing by means of intramembranous ossification, such as the skull, clavicle, and spine, are rarely involved13. In humans, the clavicle represents a remnant of an ancestral dermal exoskeleton and serves to stabilize the shoulder girdle14. Histologic studies of human embryos have indicated that the clavicular mesenchymal anlage ossifies primarily through two intramembranous primary ossification centers, appearing at six weeks and fusing at seven weeks15. Both the sternal and acromial ends of the clavicle have articular cartilage, but, after birth, a secondary ossification center develops in the cartilaginous sternal end only16. This medial (sternal) secondary ossification center and physis contribute almost 80% of the clavicle’s longitudinal growth, whereas the primary ossification centers contribute little to the increase in clavicular length15. This secondary ossification center unites with the rest of the clavicle by or before the twenty-fifth year17. It seems plausible that an osteochondroma of the medial part of the clavicle develops from the physis associated with this secondary ossification center.
References
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BY ANTHONY V. MOLLANO, MD, MARK L. HAGY, MD, KEVIN B. JONES, MD, AND JOSEPH A. BUCKWALTER, MD
Investigation performed at the University of Iowa, Iowa City, Iowa
Anthony V. Mollano, MD
Mark L. Hagy, MD
Kevin B. Jones, MD
Joseph A. Buckwalter, MD
Department of Orthopaedics and Rehabilitation, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242. E-mail address for A.V. Mollano: [email protected]
The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Copyright Journal of Bone and Joint Surgery, Inc. Dec 2004
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