Towards a functional treatment of lumbar vertebral instability. Restoration of the biomechanics with Dynesys

It is not necessary to resort to metasciences to observe that ambiguous interpretation of some medical concepts leads to disparate and even paradoxical surgical approaches. Vertebral instability is a clinical entity which can only be defined in terms of its many functional and morphological effects and anatomopathological and pathophysiological aspects. Because vertebral instability involves proteiform features and evolves in a cyclic way, it is difficult to treat and diagnose and its course is hard to predict. Furthermore, possible iatrogenic consequences should be considered. The term "vertebral instability" has been used in an inadequate manner by exponents of highly invasive spinal surgery, and arthrodesis is still considered the most effective therapy. We disagree with the principles and practice of vertebral fusion and immobilization of functional spinal units (FSUs). In our opinion spinal structures should be allowed the possibility of self-repair and we favour minimal decompression when useful and restoration of biomechanics when necessary. Although segmental instability evolves towards stenosis and hypomobility, demolition and immobilization cannot be regarded as therapeutic.