Imaging and pathologic study of intravertebral vacuum phenomenon in vertebral compression fracture

Objective: To investigate the features of intravertebral vacuum phenomenon (IVP) in vertebral compression fractures (VCFs). Methods: Two hundred and nine patients with VCFs underwent percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP). The biopsies and the images of X-ray, CT, MRI of VCFs were obtained. The consistency between IVP and osteonecrosis on histology and the positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity and Youden index of IVP for diagnosing local osteonecrosis in VCFs were analyzed. Fisher exact probability test was used to analyze the coherence between IVP and osteonecrosis in VCFs were analyzed. Fisher exact probability test was used to analyze the coherence between IVP and osteonecrosis. Results: Histological examination revealed 146(69.9%) osteoporoses, 10(4.8%) osteonecroses with osteoporoses, 53(25.4%) neoplasms. Prior to surgery, 10 cases of IVP were found. Plain radiograph showed horizontally oriented lucent cleft in the vertebral body; CT further confirmed the location of gas; T1-weighted MR image appeared hypointensity, while the signal intensity of T2-weighted MR image differed, depending on the duration of recumbency. Nine of 10 patients with IVP showed osteonecrosis on histology, while 9 of 10 patients with osteonecrosis contained IVP. The association of osteonecrosis on histology and the IVP was statistically significant (P<0.01). The PPV, NPV, sensitivity, specificity, and Youden index for diagnosing local osteonecrosis was 90%(9/10), 99.5%(198/199), 90.0%(9/10), 99.5%(198/199), and 0.9, respectively. Conclusion: The IVP is stongly suggestive of local osteonecrosis in vertebral compression fracture. (authors)