Extravertebral gas and fluid effusions associated with vertebral collapse containing a vacuum cleft possibly result from a pumping phenomenon: a new evidence of the dynamic hydro-pneumatical nature of the so-called vacuum phenomenon.

We report two very unusual observations in which gas and fluid effusions were transiently and unexpectedly found in the extravertebral spaces of patients presenting with painful necrotic vertebral collapse containing a vacuum cleft. We hypothesize that gas and/or fluid which progressively may replace vacuum in vertebral compression fractures could be secondarily pumped through extravertebral and retroperitoneal spaces. Although being rare, these observations may represent a potential missing link in the imaging snapshots of the cyclic and dynamic vacuum phenomenon.