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Septic sacroiliitis is an uncommon condition that is often diagnosed late. Two cases in the immediate postpartal period are reported. Magnetic resonance imaging contributed decisively to the early diagnosis.

Insufficiency fractures often occur in the sacrum and pubic rami but have rarely been reported in the ilium, where their frequency may be underestimated. We studied a series of 14 patients with insufficiency fractures of the ilium. Six patients had an oblique fracture through the wing of the ilium (which was bilateral in one case) and nine a supraacetabular fracture, with in one case a superomedial extension into the iliac wing. The initial radiographs were normal, making the diagnosis difficult. A linear area of sclerosis along the fracture line was seen after a few weeks. The radionuclide examination provided early detection and often demonstrated multiple insufficiency fractures (mean 2.1 per patient). Computed tomography missed some of the fractures, whereas magnetic resonance imaging proved a reliable diagnostic tool, especially in patients with supraacetabular fractures, showing the fracture as a line of low signal surrounded by an area of edema whose contours were exactly the same as those of the hyperactive focus on the radionuclide scan. Osteoporosis was a causative factor in all 14 patients and vitamin D deficiency in seven. Also, three patients had a history of fluoride therapy.

Classical bone scintigraphy can be completed by a dynamic study of the blood supply of a previously defined anatomical region. Our protocol consists of the recording of early images in the histogram mode, centred on the selected pathological region and on the symmetrical region which acts as a control. One film is taken every 3 seconds for 3 minutes following an intravenous injection of 20 mci of Tc99m MDP into a cubital fossa vein. More limited symmetrical zones of interest are visualised on the image obtained by summation of all of the information obtained during the second minute following the arterial passage of the radioactive bolus. The curve reflecting the variation in activity for each zone of interest over these three minutes can therefore be obtained. The first part of the curve, until the first slope change, corresponds to the arterial phase (blood flow), the second part, which includes a brief venous phase, corresponds to the vasculo-tissue phase (blood pool). The value of these bone image, which allow a very detailed analysis of the topography and intensity of the uptake, is above all diagnostic, while the early, vascular images and the resulting curves are essentially of pathophysiological interest. Bone angioscintigraphy is a triple examination and one of its best applications is in reflex sympathetic dystrophy. It is able to distinguish very objectively between "hot" and "cold" forms and it can indicate the most appropriate treatment for each case and follow the effects of treatment. The other indications for bone angioscintigraphy also include Paget's disease, especially the monitoring of treatment, osteomyelitis, sarcomas and osteonecrosis.

Ossifying enthesites present an undeniable diagnostic value in every chronic inflammatory rheumatism at an early stage, not only in adults but also in children. Bony scintigraphy discovers them in most localizations at a preradiological stage, as soon as they cause pain. The scanner examination enables to follow the anatomical evolution of the ossifications. It is perfectly suitable for the study of sacro-iliac and interapophyseal joints. Ossifying enthesites, the evolution of which spreads over several years, often depend on mechanical, professional or athletic constraints. Ossifying enthesitis is a common characteristics of "classic" spondylo-arthropathies which are all ossifying polyenthesites: ankylosing spondylarthritis, psoriasic rheumatism, rheumatism of enteropathies, Fiessinger-Leroy-Reiter syndrome and juvenile spondylo-arthropathies.