A gas-density cleft within a transverse separation of the vertebral body, appearing in extension and disappearing in flexion, was observed in 10 cases of vertebral collapse at the thoraco-lumbar junction. The patients were 55 to 83 years old (mean, 68) and 7 of them were on chronic corticosteroid therapy. Such an intravertebral cleft has not been found by the authors in vertebral collapse of tumoral, inflammatory, or traumatic origin and is thought to represent ischemic vertebral fracture. This sign could be helpful in the differential diagnosis of vertebral collapse in elderly patients.

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Objectives: To determine the range of normal radiographic joint space width (JSW) values and the shape of the normal hip, and the influence of age, sex, dysplasia, coxa profunda, and acetabular roof curve abnormalities on these values. Methods: On routine conventional pelvic radiographs taken in the supine position in patients with no history of hip or lumbar pain, JSW was measured at three points (superolateral, apical, superomedial), together with the VCE, HTE, and neck shaft angles; acetabular depth; and femoral head diameter. Results: 223 radiographs (446 hips) from 127 women and 96 men (mean age 51.3 years) were examined. Interindividual variations in JSW were large (apical site: 4.19 (0.92) mm; range 2-7). Mean JSW values were higher at the superolateral site than at the apical and superomedial sites in nearly 80% of cases. Women had lower JSW values than men. JSW values did not fall with age. Marked right/left JSW asymmetry was seen in 13/221 (5.9%) subjects. Eight cases of acetabular dysplasia (7 unilateral) and 16 cases of coxa profunda were found, but no cases of acetabular protrusion. The JSW was thicker in dysplastic hips, and thinner in hips with coxa profunda. A roof curve abnormality was found in 96/446 (21.5%) hips. Conclusions: Normal JSW values vary widely; the JSW is commonly narrower at the superomedial site than at the apical site, and is sometimes asymmetric. The roof curve is dysmorphic in about 20% of patients. These findings may have important implications for epidemiological studies and early diagnosis of osteoarthritis of the hip.

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Sequential radiographic and magnetic resonance (MR) imaging examinations were performed in nine patients with an intravertebral vacuum cleft indicative of avascular necrosis. Progressive changes in the content of the cleft occurred within an hour after the patients were placed in a supine position. Initially, the cleft showed a gaslike pattern during extension of the spine, with a radiolucent band on radiographs and a signal void on MR images. Later, the vacuum phenomenon disappeared on radiographs, and a fluidlike high-signal-intensity pattern appeared on T2- or T2*-weighted MR images, suggestive of a slow fluid inflow within the intravertebral cleft. Because the recognition of a vacuum cleft in a collapsed vertebral body helps avoid confusion with malignancy or infection, it is important to search for this in examinations performed immediately after supine positioning.