Degenerative changes following spinal fixation in a small animal model

Cramer GD, Fournier JT, Henderson CN, Wolcott CC., J Manipulative Physiol Ther. 2004 Mar-Apr;27(3):141-54.

This study was designed to evaluate changes occurring over time in the lumbar (low back) spinal joints following fixation (the lack of normal motion or alterations in proper biomechanics). This was an approved Institutional Animal Care and Use Committee ((IACUC) study and was conducted entirely in a universtity animal facility.

Researchers used 87 small animals (laboratory rats)of which 64 were fitted with a specially engineered vertebral fixation device applied at 3 contiguous lumbar segments (L4, L5, L6). 24 rats were reserved as a control group without fixation apparatus. These “fixation devices” were designed and used in this experiment to simulate the loss of normal mobility in the human spine which often occurs with age, injury, arthritis and spinal subluxation (see footnote).

The spinal segments (joints) of the control rats were compared with those of animals with 1, 4, or 8 weeks of fixation. Subgroups of these fixation animals subsequently had the fixation device removed for 1, 2, 4, 8, or 12 weeks to evaluate the effects of attempting to reestablish normal movement to the vertebral segments following hypomobility.

Results showed that when spinal joints were fixated and could not move normally, they degenerated. Notable alterations in the joints included calcification and spur formation. There was also noted dehydration of the intervertebral disc and degenerative changes in the vertebral bodies to a lesser extent. These changes were most pronounced in the zygapophysial joints where most spinal motion occurs. The degree of degenerative change in the joints was directly proportional to the amount of time the fixation had been present.

It may be postulated from this study that maintaining optimal joint function or motion, and correcting decreased function or fixation, should result in decreased degenerative joint disease or arthritis.

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