Pseudoaneurysm overlying an osteochondroma: a noteworthy complication
© The Author(s) 2010
Received: 29 May 2009
Accepted: 19 October 2010
Published: 20 November 2010
Pseuodaneurysms are an extremely rare complication of osteochondromas. We describe a case of traumatic pseudoaneurysm of the brachial artery presenting as a soft tissue mass in a patient who was treated for an osteochondroma 3 years earlier. This case demonstrates that radiographic follow-up of large osteochondromas is mandatory and that, in patients with soft tissue masses and a history of osteochondroma, pseudoaneurysms should be included in the differential diagnosis.
Osteochondromas are hamartomas derived from an aberrant subperiosteal germ of the physeal cartilage and grow by normal enchondral ossification . They are the most common benign tumors of bone, accounting approximately for one third of benign lesions of the skeleton . Nevertheless, as they are usually asymptomatic, the real incidence is probably higher . Patients usually present during the second decade of life . Malignant transformation has been reported as a very rare complication, accounting for <1% and occurring after puberty more frequently in the limb girdles [1, 4, 5]. In cases of hereditary multiple osteochondromas, the risk of sarcomatous change is higher [1, 6, 7].
The radiographic appearance of this tumor is often diagnostic: as a matter of fact, the continuity of the lesion with the underlying native bone cortex and medullary canal is pathognomonic of osteochondroma. Computed tomography (CT) and magnetic resonance (MR) imaging are useful for identifying and studying complications such as malignant transformation, bone fracture, vascular compromise, neurologic sequelae, and overlying bursa formation. The thickness of the cartilage cap is typically 1–3 cm in young patients, whereas in adults, it is often only a few millimeters thick or entirely absent [4, 8–10]. A continuously growing lesion and a hyaline cartilage cap >1.5-cm thick, after skeletal maturity, suggest malignant transformation. Cortical bone is devoid of mobile protons and shows low signal intensity in all pulse MR sequences, whereas the medullary component has the appearance of yellow marrow. MR imaging is the best radiologic modality for visualizing the effect of the lesion on surrounding structures and evaluating the hyaline cartilage cap. The high water content in nonmineralized portions of the cartilage cap has an intermediate to low signal intensity on T1-weighted MR images and very high signal intensity on T2-weighted images. These features typically allow accurate measurement of the cartilage cap thickness and distinction from overlying muscle on MR images [4, 11–13].
Surgical excision is limited to symptomatic osteochondromas; as a matter of fact, when the tumor is asymptomatic, surgery is not recommended [1, 14]. Indications for surgical resection are pain, deformity, compression to a neurovascular bundle, continuous growth, and suspected malignant transformation [1, 14, 15]. However, when a child presents with a large osteochondroma close to a neurovascular bundle, surgery is indicated to avoid further enlargement, which would make surgery more challenging with a higher risk of neurovascular complications. Pseudoaneurysm represents an extremely rare complication of osteochondroma and typically involves the popliteal and femoral arteries [16, 17]. We present a case of posttraumatic pseudoaneurysm of the brachial artery occurring after incomplete resection of an osteochondroma and presenting as a soft tissue mass.
Pseudoaneurysms are a rare complication of osteochondromas and they are more frequent after the end of the enchondral ossification phase, when the cartilaginous cap become bony and sharp . A hard swelling is the most common pattern of clinical presentation . The most frequent site of this complication is the distal femur, whereas the arm is an extremely rare site, with only a few cases of pseudoaneurysm of the brachial artery reported in the literature [18–21]. Repair of the arterial injury is seldom possible. When an end-to-end anastomosis cannot be performed, graft replacement with the autologous saphenous vein or with a synthetic graft is preferred . As a matter of fact, in our case, the extent of the pseudoaneurysm made the brachial artery non-reparable, and the vascular surgeon opted for a reconstruction with a saphenous vein graft.
The case presented here is quite unusual, but the clinical presentation reflects the typical case found in the literature: an adolescent male, already treated for a large osteochondroma in an area with high risk of neurovascular compression, reporting a sport-related injury. The differential diagnosis included malignant transformation and Ewing’s sarcoma, so we performed contrast-enhanced MRI and angiographic MRI to rule out these diagnoses. MRI is mandatory for evaluating such atypical masses in children and adolescents . Moreover, malignant transformation is extremely rare in adolescence , and Ewing’s sarcoma often presents with other signs and symptoms, such as fever, increased serum lactate dehydrogenase and erythrocyte sedimentation rate, leukocytis, and anemia , which were not present in our patient. Therefore, according to the patient’s history of blunt trauma, to MRI features, and to the surgical findings of close proximity of the pseudoaneurysm to a cartilaginous spur, the diagnosis was traumatic pseudoaneurysm caused by an osteochondroma. This case shows how important it is to perform adequate resection of a large osteochondroma arising in close proximity to neurovascular structures. On the other hand, osteochondromas in adolescence may spontaneously regress  or recur, even after adequate resection, so that a radiographic follow-up is mandatory .
In conclusion, we emphasize the importance of correct treatment and follow-up of large osteochondromas in dangerous regions in order to avoid such complications. We also encourage the orthopedic oncologist to include pseudoaneurysms in the differential diagnosis of soft tissue masses, especially when there is a history of osteochondroma resection.
Conflict of interest
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