The vacuum phenomenon in the lumbar spine is a common finding on radiographs and CT imaging. Its presence has been known for more than a century and has been increasing in spine literature during the past 20 years. Although once thought of as an incidental finding, further research
may yield important findings about the vacuum phenomenon, which may allow radiologists to understand its meaning more clearly when it is encountered.Learning Objective: The goal of this article is to present the reader with a better understanding of the vacuum phenomenon as it pertains
to the lumbar spine and with its history in radiology and surgery literature, its presence in recent literature, and how it may impact spine radiology and surgery moving forward.
Background: Lumbar vacuum phenomenon (VP) within the intervertebral disc has been classified based on CT imaging. We compared same-patient sagittal CT images and dynamic flexion-extension x-rays to determine if there is a difference in the amount of vertebral instability present between three VP morphologies on CT.Methods: Anterior subluxation measurements on x-ray were compared with same-segment VP on CT images from the same patient when both findings were present. VP were classified as spot, island, or linear. It was determined if there was a difference in the amount of anterior subluxation between the three morphologies. Secondary analysis looked at whether there was a difference in anterior subluxation between the three groups if patients had undergone a prior lumbar fusion surgery or not. Results: There was no difference in anterior subluxation between the three groups on dynamic flexion-extension x-rays. There was also no difference between the three groups on flexion-extension x-rays when patients were separated based on if they had received or not received a previous lumbar fusion surgery. Conclusion: IVD VP morphology is not a useful indicator in determining vertebral instability pre-operatively according to CT scan. Further fine-tuning of an IVD VP CT classification is needed to help radiologists and spine surgeons know when IVD VP presence is important.
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