A case of false results of osteoscintigraphy in search of bone metastases after endoprosthesis of shoulder and hip joints

Abstract

the clinical case demonstrates the erroneous interpretation of the results of a radionuclide study of the locomotor system without taking into account the anamnesis and clinical and laboratory data. To search for bone metastases, osteoscintigraphy is used all over the world, which allows to diagnose them at a preclinical stage of the process, ahead of radiological ones by 4-5 months. Cancer of the mammary and prostate glands, as well as kidney cancer, metastasize to the bones very early. About 50% of cases of these metastases are detected in the absence of clinical manifestations, which prompts regular control osteoscintigraphy regardless of complaints and clinical condition of patients. Research is carried out on gamma cameras, and phosphate compounds labeled with the technetium isotope are used as a radioactive drug. 3 hours after its intravenous injection with an activity of 600 MBq, in normal conditions against the background of uniform distribution in the bones, increased accumulation is noted in the area of the base of the skull, ribs, angles of the shoulder blades, vertebrae, pelvic bones, and meta-epiphyseal sections of tubular bones. The results of the research are evaluated qualitatively and quantitatively. With high-quality, hyperfocuses of the isotopes are visually determined in separate areas of the skeleton. But it is the quantitative analysis that allows us to draw a conclusion about the secondary damage to the skeleton. A difference in the accumulation of the isotope in any part of the skeleton in comparison with an unaffected area above 150% is considered a sign of metastases. It should be noted that phosphates labeled with radioactive technetium sometimes provide a fairly high level of fixation in areas of inflammatory, degenerative-dystrophic or traumatic processes. What we observed in this case. A patient with breast cancer underwent joint endoprosthesis twice: first of the shoulder, and then of the hip joint. The cause was pathological osteoporosis and degenerative-dystrophic changes. On subsequent control osteoscintigrams, there were no foci of increased accumulation of the radiopharmaceutical in the skeleton. But after the second endoprosthesis of the hip joints six months later, hyperfixation of the isotopes  in the corresponding joints was detected, on the basis of which the conclusion of their metastatic lesion was made. The patient did not indicate before the study about the recent endoprosthesis. She did not notice any pain syndrome. In order to calm down, she did an osteoscintigraphy after 5 months. The inclusion of the isotopes in the hip joints was significantly reduced and did not exceed the upper limit. Some laboratory parameters such as alkaline phosphatase and ionized calcium are known to be significantly elevated in metastatic bone disease. The patient's content was within normal limits. All this made it possible to remove the preliminary conclusion regarding the secondary damage to the skeleton. And the increased accumulation of radionuclide should be considered a consequence of postoperative intervention. Thus, before passing a verdict on bone metastases, a thorough study of the anamnesis, radiological and clinical laboratory research data is necessary.