Osteitis Condensans Ilii

Osteitis condensans ilii is a nonspecific, self-limited inflammatory disease of the iliac bone in women more typically of childbearing age. This condition may be seen in older women, and even in men although rarely. One study revealed its incidence to be 1.6% (Numaguchi 1971). It is mostly bilateral and symmetrical, although unilateral cases are not rare. The cause is unknown, but, as with osteitis pubis, it has been related to abnormal stress of pregnancy and delivery, which cannot explain its occurrence in men.

The radiographic features of osteitis conden-sans ilii in the classic cases are simple yet unique, presenting triangular or spinnaker-like condensation of the ilia at the sacroiliac joints bilaterally and symmetrically (Fig. 7.1A). The condensation is localized to the lower anterior aspects of the ilia. Unlike in osteoarthritis, infective arthritis, or seronegative arthropathy, the sacroiliac joints in this condition are little affected and sacral involvement is minimal if any. The shape changes according to the degree of sacral inclination in relation to the radiographic projection (Fig. 7.2A). Regional osteophytic beaking is a common accompaniment.

Pinhole scintigraphy likewise shows symmetrical, club-shaped, or round areas of intense tracer uptake in the lower halves of both ilia along the sacroiliac joints (Figs. 7.1B and 7.2B). The shapes vary according to the sacral inclination. When the coronal plane of the sacrum is relatively flat the lesion looks like a spinnaker and when horizontally tilted the lesion appears round. In occasional cases, tracer uptake is asymmetrical and inhomogeneous, probably due to involutional change with age. It is well known that bilateral and more or less symmetrical tracer uptake may also occur in the lower sacroiliac joints in ankylosing spondylitis, but this is usually ill defined (see Ankylosing Spondylitis in Chapter 11) and mostly attended by the associated stigmata in the spine and other skeleton. It is to be remembered for differential diagnosis that unilateral sacroiliac joint uptake can occur in infection, trauma, metastasis, or seronegative spondyloarthropathies. Using pinhole scanning a more likely or specific diagnosis can frequently be indicated and the value of the tangential view in this situation cannot be overemphasized (Fig. 7.3).

Iliac Condensans
Fig. 7.1A, B Osteitis condensans ilii with the classic "spinnaker" sign. A AP radiograph of the left sacroiliac joint in a 32-year-old female shows long triangular bony condensation in the iliac side of the lower sacroiliac joint

(arrows). Note preserved articular space. B Anterior pinhole scan reveals intense spinnaker uptake exactly corresponding to the radiographic condensation (arrows)

Sacrum Acutum

Fig. 7.2A, B Osteitis condensans ilii with modified round uptake in sacrum acutum. A AP radiograph of the pelvis with bilateral condensans ilii in posterocranially tilted sacrum in a 25-year-old female shows symmetrical roundish condensation (arrows). B Anterior pinhole scan shows well-matched round uptake (arrows). This finding is due to end-on (axial) viewing of the spinnaker

Fig. 7.2A, B Osteitis condensans ilii with modified round uptake in sacrum acutum. A AP radiograph of the pelvis with bilateral condensans ilii in posterocranially tilted sacrum in a 25-year-old female shows symmetrical roundish condensation (arrows). B Anterior pinhole scan shows well-matched round uptake (arrows). This finding is due to end-on (axial) viewing of the spinnaker

Tilted Sacrum

Fig. 7.3A, B Usefulness of pinhole scintigraphy in the study of the sacroiliac joints. A Posterior spot scintigraph shows a suspicious lesion in the right sacroiliac joint (arrow). B Tangential pinhole scan shows the intense tracer uptake to be localized in the mid-sacrum, a metastasis from lung cancer (arrowheads). Note the normal iliac tracer uptake (arrows)

Fig. 7.3A, B Usefulness of pinhole scintigraphy in the study of the sacroiliac joints. A Posterior spot scintigraph shows a suspicious lesion in the right sacroiliac joint (arrow). B Tangential pinhole scan shows the intense tracer uptake to be localized in the mid-sacrum, a metastasis from lung cancer (arrowheads). Note the normal iliac tracer uptake (arrows)

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Responses

  • Eugene Downs
    What is osteitis condensans ilii?
    6 years ago
  • Johannes
    Can osteitis condensans ilii involve sacrum?
    1 month ago

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