We measured the mechanical properties of 16 fresh cadaver lumbar spine motion segments, both before and after saline injection, to gauge the influence of nuclear fluid content. Twelve specimens substantially retained the injected saline and four did not. The behaviors of these two groups were found to be quite different.

In the 12 fluid-retaining specimens, fluid injection uniformly reduced mean motion in response to given load levels;​ butless so in compression, extension and torsion than in flexion and lateral bending. Mean intradiscal pressure-increases upon loading after injection were smaller than before injection in flexion and torsion, nearly the same in compression, and larger in extension and lateral bending. The total pressures in every case were considerably larger, by as much as 83%.