Thursday, September 11, 2008

Sacral insufficiency fractures- C/F, diagnostic tests

Sacral insufficiency fractures occur due to osteopenia and they form a distinct subgroup of pathologic fractures. Sacral insufficiency fractures are an often unsuspected cause of low-back pain in elderly women with osteopenia who have sustained unknown or only minimal trauma. Usually the onset is acute LBA. Differential clinical and radiographic diagnosis of these fractures is often difficult as clinical presentation and plain radiograph findings can mimic metastatic disease, leading to unnecessary investigations and treatment.
Imaging aspects:
1. CT scan: In all cases the diagnosis was confirmed with computed tomography. However, the location, linearity, and appearance of these fractures on computed tomography is very characteristic and obviates the need for further evaluation.
2. Scintigraphic studies: Similarly; identifying characteristic scintigraphic patterns in sacral fractures, which are frequent in osteopenic patients, could avoid mistaken diagnoses and unnecessary tests or treatment.
Fracture location:
One of the striking feature of these sacral fractures is their invariable location. Bone scintigraphy is very sensitive for the detection of fractures in the sacrum, with demonstration of the H-shaped (or butterfly) sacral pattern or the combination of concomitant sacral and parasymphyseal uptake being considered as characteristic of insufficiency fractures. The characteristic butterfly shape is the because of the fracture line i.e. fractures extend vertically in the sacral alae, parallel to the sacroiliac joints. They are located just lateral to the margins of the lumbar spine.
This distribution suggests that such fractures could be partially caused by weight-bearing transmitted through the spine.

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