Contribution to the diagnosis of idiopathic femoral head necrosis by scintigraphy with 99mTc-MDP assessed quantitatively by computer

The authors have studied by quantification the bone uptake of 99mTc-MDP in femoral head necrosis in order to evaluate in an objective manner conventional scintigraphy, and thus to increase the sensitiveness and efficacy of an exploration for an early diagnosis of these patients. Twenty cases of femoral necrosis have been studied, diagnosed in all cases by histopathological analysis; in twelve of them the process was unilateral and in the other eight bilateral. All explorations were carried out with 99mTc-MDP, a gamma camera and a PDP 11/40 computer for the quantitative study with the obtention of indices relating the activity between the femoral heads and, of these, to a normal vertebra. Quantification in the control group showed that the uptake of the nuclide was similar in both femoral heads and is lower than this in the vertebra. In all cases of unilateral necrosis the abnormal deviations of the indices relating the pathological head to the contralateral head and the lumbar vertebra were significant. In bilateral femoral head necrosis, an increase has been observed in all indices, although only the index relating the contralateral femoral head suspect of a lesion to vertebral activity was statistically significant. The proposed method for quantifying can be carried out easily and is very useful for diagnosing femoral necrosis since it improves the results of a subjective assessment of the scintigraphic image and can earlier detect the abnormal uptake of the lesion.