Intraosseous pneumatocysts of the ilium. Findings on radiographs and CT scans.

Abstract

CT scans demonstrated a localized collection of gas adjacent to a normal sacroiliac joint in 5 patients. In each case the lesion was sharply demarcated by a thin sclerotic rim. A benign bone cyst was confirmed histologically in 2 cases. The radiologist should be aware of this appearance so as to avoid invasive procedures based on a misdiagnosis of infection or neoplasm.

Intraosseous pneumatocyst of the ilium: CT findings in two cases and literature review

“…Intraosseous pneumatocyst of the ilium is a benign lesion first described by Ramirez et al [2]. An accurate review of the literature identified 16 cases of this unusual entity, whose principal features are listed in Table 1.…”

“…In the series from Ramirez et al [2] two pneumatocysts were excised: since a nonspecific fibrous capsule was present in both, associated in one with microscopic foci of myxoid tissue, the lesions were defined as intraosseous ganglia.…”

“…Intraosseous air formation has been reported in several abnormalities: spontaneous or postoperative osteomyelitis, focal ischemia and osteonecrosis, solitary bone cysts, arthroplasty, vertebral myelomatosis, spondylitis neoformans, collapsed vertebral bodies, and Schmorl nodules [1,2]. In these conditions the gas is produced by bacteria or by the vacuum phenomenon [1].…”

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IntroductionIntraosseous air formation has been reported in several abnormalities: spontaneous or postoperative osteomyelitis, focal ischemia and osteonecrosis, solitary bone cysts, arthroplasty, vertebral myelomatosis, spondylitis neoformans, collapsed vertebral bodies, and Schmorl nodules [1,2]. In these conditions the gas is produced by bacteria or by the vacuum phenomenon [1].

An unusual form of intraosseous gas (nitrogen) collection has been described at the level of the ilium, in proximity of the sacroiliac joints, and variably denominated as intraosseous pneumatocyst of the ilium [1±6], intraosseous pneumatocele [7,8], or gas-filled subchondral cyst [9].

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‘Abnormal’ cervical imaging?: Cervical pneumatocysts – A case report of a cervical spine pneumatocyst

“…It has been postulated that the gas develops spontaneously, 17 that the gas accumulates within a pre-existing simple fluid-filled cyst or ganglion or that nitrogen relapses from adjacent joints. 11 In addition, it has been proposed that extension of intervertebral disc gas through a degenerate endplate may cause pneumatocysts, with trauma facilitating its passage.…”