Because of the history of penetrating trauma, the poor response to anti-inflammatory medication, the atypical location, and the significant soft tissue swelling, osteoid osteoma was not considered.
Often bone scintigraphy is performed in osteoid osteoma as the primary diagnostic modality when the clinical history is atypical or vague, or when the radiographs are equivocal or normal. Because the scintigraphic appearance of osteoid osteoma on delayed images may vary from an extremely localized mild increased activity (1), blood pool images at five minutes should be performed. On blood pool imaging, osteoid osteoma invariably shows a localized increase in activity whereas osteomyelitis shows more diffuse activity.
In those cases where bone scan is equivocal, Lisbona and Rosenthall (2) suggest that Ga-67 imaging may be helpful in distinguishing acute/subacute osteomyelitis from osteoid osteoma. Although reporting on a series of only five patients, all cases of osteoid osteoma with intense Tc-99m-MDP deposition demonstrate low grade Ga-67, unlike osteomyelitis where radiogallium is known to concentrate intensely. These studies must be interpreted cautiously since avid Tc-99m-MDP deposition with very low gallium uptake can be seen with fracture, infarction, chronic osteomyelitis and acute osteomyelitis under antibiotic treatment (2).
When a patient presents with bone pain localized to a particular region, plain radiographs should be obtained. If a characteristics lesion is found, other imaging modalities are unnecessary. Both blood pool and delayed bone scans should be reserved for cases where it is difficult clinically to determine the exact site of pain. Bone scintigraphy can localize the site where subsequent radiographs should be centered. When radiographs are negative, a positive bone scan can direct a biopsy. A bone scan is also useful to determine whether a nondescript bone lesion on radiographs is active or not and whether synchronous lesions exist.
2) Lisbona R, Rosenthall L. Role of radionuclide imaging in osteoid osteoma. Am J Roentgenol 1979; 132:77-80.
2) Winter PF, et al. Scintigraphic detection of osteoid osteoma. Radiology 1977; 122:1277-178.
3) Gilday DL, Ash JM, Benign bone tumors. Semin Nucl Med 1976; 6:33-46.
4) Gilday DL. Diagnosis of obscure childhood osteoid osteomas with the bone scan (abst). J Nucl Med 1974; 15:494.
5) Simon MA, Kirchner PT. Scintigraphic evaluation of primary bone tumors. J Bone Joint Surg 1980;62:758-764.
J. Anthony Parker, MD PhD, email@example.com