Neoplasms of the Elbow

Osteoid Osteoma and Osteoblastoma

Osteoid osteoma arising in an intraarticular location is relatively uncommon; however, it may occur in the region of the elbow. It is relatively common at the elbow, but only a few reports on the presentation, diagnosis, and management have appeared. This small benign bone tumor occurs in patients of any age, most commonly children and young adults. As with most bone tumors, boys and men are more commonly affected than girls and women. Unremitting pain, especially at night, is the dominating symptom; however, progressive loss of motion is characteristic at the elbow. Occasionally, the pain may be experienced at a site remote from the lesion. Another peculiar feature of this tumor is its occasional association with atrophy of the adjacent soft tissues. In the Mayo Clinic's experience with 14 such cases, eight have occurred in the distal humerus, four in the ulna (two coronoid, two olecranon), and two in the radial head–neck region ( Fig. 81.2 ).

Motion loss with an osteoid osteoma at or near the elbow joint selectively affects the flexion arc, but pronation and supination are preserved. In addition, there may be a synovial reaction that may further confuse the diagnosis. The most striking feature of these tumors is the prolonged average time required for making the diagnosis. In the Mayo Clinic's experience, the delay to diagnosis averaged almost 2 years.

The osteoid osteoma, by definition, is small, usually no more than 1.5 cm in diameter. Lesions that are clinically and histologically similar but are 2 cm or more in diameter are referred to as osteoblastomas; these lesions have clinical features somewhat different from those of osteoid osteoma, but loss of motion is a common feature. Osteoid osteoma is small when first encountered and remains small, a feature that suggests the diagnosis.

An extensive diagnostic evaluation is usually performed but is not necessary to make the diagnosis if one is sensitive to the features described previously. When the patient complains of unremitting pain in the elbow, plain radiographs may or may not reveal the presence of the tumor ( Fig. 81.3 ). The lesion typically appears as a central small nidus, with a radiolucent area surrounded by an area of sclerosis. When the lesion is located on the surface of the bone, there may be periosteal new bone formation that obscures the nidus. A further unusual radiographic feature of subperiosteal new bone formation in adjacent bones has been reported. The authors concluded that “awareness of this association will prevent misdiagnosis of the benign neoplasm as an inflammatory arthritis.”

Technetium-99m scintigraphy has been essential in locating these lesions. If technetium-99m scintigraphy reveals no abnormality, an osteoid osteoma is unlikely; however, if the bone scan is positive, further diagnostic studies of the involved area should be undertaken ( Fig. 81.4 ). If there is any significant synovial reaction, there may be increased uptake owing to the synovitis, as well as to the lesion itself.

Today, thin-section (0.5–2.0 mm) CT and multiplanar reconstructions utilizing bone window are the diagnostic standard to confirm the benign nature of bone reaction and to identify the nidus.

The role of MRI in the evaluation of osteoid osteoma is controversial. A constant finding on MRI scans is marked bone marrow edema corresponding to the highly vascularized mesenchymal tissue. Gadolinium enhancement increases the nidus conspicuity.

Grossly, there is usually some sclerotic bone surrounding a central nidus. This nidus may be somewhat redder than the surrounding cortical bone and has been described as having the appearance of a small cherry. It is sometimes helpful to obtain radiographs of the excised block of tissue before the pathologist cuts into the block. Microscopic examination of the surrounding bone shows no unusual features; the nidus itself consists of a network of osteoid trabeculae (see Fig. 81.3 ).

Osteochondroma

Osteochondroma is probably the most common benign bone tumor, but it is rare at the elbow. The incidence may be somewhat higher than that reflected in our surgical experience, however, because osteochondromas are often asymptomatic.

The tumor commonly arises from the metaphyseal region of long bones and usually stops growing when skeletal maturity is reached but remains present in adulthood ( Fig. 81.5 ). It may be pedunculated on a stalk or sessile and have a broad base ( Fig. 81.6 ). The tumor is covered by a cartilage cap, which, if greater than 1.5 cm to 2 cm thick, should raise the suspicion of malignant transformation. This occurs in approximately 1% of solitary and up to 5% of multiple osteochondromas.

When multiple bones are involved, severe deformity of the elbow may occur and the risk of malignancy also increases. Hence patients with multiple osteochondromas should be carefully observed through periodic follow-up examination.

Osteochondromas in the region of the elbow may cause painless loss of motion. The tumor may also cause nerve compression and even dislocation of the joint.

If there are symptoms or mechanical or cosmetic difficulties, complete excision of the osteochondroma is performed. Simple excision generally results in cure, although local recurrence has occurred, probably because of incomplete excision of the cartilage cap.