Re-Equilibration not Arthrodesis. Contribution to the Functional Treatment of Lumbar Vertebral Instability

Vertebral instability is a clinical condition not yet satisfactorily defined in its multiple aspects: functional, morphological, anatomopathological and pathophysiological. The term "vertebral instability" is used in a non-rigorous manner by exponents of highly invasive spinal surgery and arthrodesis is still considered the most effective therapy. However, attitudes may be beginning to change. We tackled the problem of vertebral lumbar instability from a functional point of view, correlating the morphological alterations with the functional ones and considering them not as "excessive" but as anomalous movements. We assessed this condition in 26 patients by conventional methods and by biomechanical study "in vivo" with axial-loaded computed tomography (ALCT). The instability was associated with various conditions of disc degeneration, stenosis and spondylolisthesis. All patients underwent dynamic neutralization with the DynesysTM system; 13 patients also underwent microsurgical decompression. At follow-up (average 24 months), lumbar pain was found to have ceased in 20 patients (77%) and decreased in six (23%). In all cases, neurological symptoms diminished markedly and root pain disappeared. Spondylolisthesis disappeared in nine cases out of 14 and was reduced in five; in another four cases it was visible only by ALCT and disappeared at follow-up. In all cases, postoperative X-ray showed that the disc plates of the stabilized vertebrae were parallel, with slight widening of the disc spaces above and below, and there was also improvement in lumbar lordosis. Post-operative ALCT, carried out in eight cases, demonstrated neutralization of the anomalous movement and restoration of biomechanics similar to normal.