Bone scintiscanning in Orthopedics

diagnosis: stated earlier, bone scan is quite non specific and exceptions prove the rule. Regional pain that aggravates at Radionuclide imaging is perhaps the only means to image night in a young patient is quite typical of osteoid osteoma. the physiology of skeletal system. About 30% of mineral Osteoid osteoma and fibrous dysplasia are two entities loss must take place before an abnormality become visible where the role of bone scan perhaps surpasses even that of on conventional radiograph [1]. This may take a few days histopathology [3,4]. to several months depending on the type of pathology. In contrast skeletal scintigraphy shows “hot spots” based on Osteoid osteoma appears as focal avid tracer accumulation regional osteoblastic activity and becomes manifest within in the bone with a zone of less avid surrounding activity 24 hours of onset of insult. About 5 to 15% increase in bone (double density sign). Radiologically there may be an area turnover activity will show as a hot spot on a bone scan [2]. of sclerosis in the bone. Osteoid osteoma may be cortical, medullary, intracapsular, periosteal. Periosteal type of Technetium 99m-methylene diphosphonate is the lesion may sometimes lead to significant sclerosis in the radiopharmaceutical compound that optimally localizes adjoining bone making diagnosis difficult on Plain to the bones 3 hours post intravenous administration. radiograph, CT or MRI. However, bone scan will show a Images are acquired using a gamma camera that senses the well defined focus of intense tracer accumulation in the low energy gamma radiation. region of nidus (Fig 3). The nidus appears as a small Bone scan is by far the most challenging of all nuclear scans osteolytic area in CT scan. to interpret because of its non specificity. Any pathology Fibrous dysplasia appears as increased radiotracer that accounts for variation in osteoblastic activity of the accumulation in the involved bones. When multiple bones skeleton will result in increased tracer localization in the are involved the abnormality is usually confined to one skeleton. This could be because of local or systemic cause. side of skeleton. A typical scan finding obviates the need This is a pictorial essay that illustrates certain important for histology (Fig 5). entities encountered in day to day orthopedic practice.