[Quantitative bone scintigraphy in the study of the sacroiliac joint in chronic inflammatory rheumatism]

Scintillation counting of the sacro-iliac bones using technetium pyrophosphate or diphosphate is a simple examination without danger. The uptake opposite each sacro-iliac bone is assessed by reference to that of the lumbar spine visible on the film. A study of a control group of 81 subjects permits one to determine the existence of variations in relation to age: the fixation is high in subjects under the age of 20 years and reduced in adults aged over 50 years. The 44 controls from 20 to 50 years, permit one to retain as reference value, the ratio 1.14 for the right sarco-iliac bone and 1.11 for the left sarco-iliac bone with a confidence interval of 0.13. There was noted a significantly high uptake during arthritis. Whether this was the axial form (40 cases) or the peripheral from (7 cases) and during Reiter's syndrome (15 cases). This hyperfixation was more frequent and more important when the sacro-iliac involvements (whether accompanied or not by radiological signs) were the cause of inflammatory pain. Increased uptake was also noted during other forms of chronic inflammatory rheumatism: rheumatoid arthritis (10 cases). Chronic inflammatory rheumatism (unclassifiable) 20 cases. It thus seems that one may retain in many cases the existence of sacro-iliac inflammatory changes without the latter being necessarily accompanied by clinical or radiological signs. The discovery of hyperfixation of the sacro-iliacs during chronic inflammatory rheumatism is further evidence in favour of the diagnosis of sacro-iliac arthritis but should be interpretated in the light of the general context.