A 73-yr-old white woman presented with complaints of lumbosacral and left leg pain radiation. The patient was identified as having restricted straight leg raising and an absent Achilles reflex on the left. A lumbar spine x-ray demonstrated degenerative disc disease with multilevel vacuum discs. The patient, recovering from a recent left knee arthroplasty, subsequently had a computed tomographic scan of the lumbar spine, which revealed the presence of low-grade multilevel spinal stenosis. Tiny air bubbles were also identified as leaking from the vacuum discs from L3-L4 through L5-S1.
As initially described by Magnusson1 and later by Knutsson,2 the vacuum disc is an accumulation of gas residing within the intervertebral disc. Although occurring most often in the lumbar region, it can be found at any spinal level. In all ages, it can be identified in 1%-3% of patients and in 20% of elderly patients.3
On imaging studies, a vacuum disc can be recognized as a lucency within either the intervertebral disc or a synovial joint as a direct product of the liberation of a gas consisting of 95% nitrogen and lesser amounts of oxygen and carbon dioxide into the disc as well as joint space.4 Distraction of the joint surfaces or extension of the spine producing negative pressure or both sucks nitrogen from the surrounding tissues. Within the intervertebral disc, the gas fills clefts created during the process of disc degeneration. Desiccation or dehydration of the nucleus pulposus that initiates this process or both is also recognized by the term "osteochondrosis." These clefts that initially develop within the central nucleus may eventually radiate to and then subsequently extend through the walls of the annulus fibrosis, permitting the contained gas to escape as bubbles into the spinal fluid (Fig. 1).
Intervertebral osteochondrosis can also occur secondarily as a consequence of direct trauma or in association with metabolic disease, i.e., pseudogout, or both. Although relatively rare, vacuum disc can be associated with a vertebral malignancy or infection or both when this pathology abuts the cartilaginous end plates interfering with disc nutrition.
1. Magnusson W: Über die bedingungen des hervortretens der wirklichen gelenkspalte auf dem röntgenbilde. Acta Radiol
2. Knutsson F: The vacuum phenomenon in the intervertebral discs. Acta Radiol
3. Resnick D, Niwayama G, Guerra J Jr, et al: Spinal vacuum phenomena: Anatomical study and review. Radiology
4. Sarli M, Perez Manghi FC, Gallo R, et al: The vacuum cleft sign: An uncommon radiological sign. Osteoporos Int