Vacuum in the Body

The vacuum phenomenon is quite reliable when degenerative changes of the disk space need to be differentiated from infectious ones. But is it really a vacuum? Some researchers have sampled diskal "vacuums" with needles and reported a high content of nitrogen. See Figure 8.36b and c for proof that some sort of biomechanical phenomenon is at work: In b the spine is flexed forward—no pocket is seen. As the spine is flexed backward in c, the pocket appears out of nowhere.

Intervertebral joint osteoarthritis: Intervertebral or facet joint osteoarthritis can cause a narrowing of the spinal canal and the neuroforamina. As the integrity of the joints decreases, intervertebral misalignment may ensue that further encroaches on the spinal canal and the forami-na—the so called pseudospondylolisthesis or degenerative spondylolisthesis (Fig. 8.37).

Fig. 8.35 Is there anything abnormal on this radiograph of Will Walton's lumbar spine?

I Osteochondrosis

I Osteochondrosis

Vacuum Phenomenon

Fig. 8.36 a-c The lower lumbar spine (a) is affected by extensive degenerative disk disease and associated typical osseous changes. The uppermost visible intervertebral disk has normal height—all others are reduced in height. The disks are all but destroyed. Dark stripes are seen within the residual disk. This "vacuum phenomenon" is a sure indication of a degenerative process. The vertebral end plates are sclerotic. Their margins show osseous protuberances—spondylophytes. The deterioration of the disk decreases the strength of the spinal architecture,

Fig. 8.36 a-c The lower lumbar spine (a) is affected by extensive degenerative disk disease and associated typical osseous changes. The uppermost visible intervertebral disk has normal height—all others are reduced in height. The disks are all but destroyed. Dark stripes are seen within the residual disk. This "vacuum phenomenon" is a sure indication of a degenerative process. The vertebral end plates are sclerotic. Their margins show osseous protuberances—spondylophytes. The deterioration of the disk decreases the strength of the spinal architecture, leading to malalignments such as seen at the L5/S1 level on this radiograph. Note how the loss of disk height also diminishes the size of the neuroforamina (arrows). The foramen has a normal diameter at the L2/L3 level but at the L5/S1 level it is much smaller. A nerve root must squeeze through there! Functional radiographs of the lumbar spine bent forward (b) and backward (c) performed within seconds of each other prove that the phenomenon is indeed due to vacuum: the stripes develop out of nothing in (c).

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