[Water and electrolyte content of human intervertebral disks under varying load]

Spine biomechanical testing methodologies: The controversy of consensus vs scientific evidence

Biomechanical testing methodologies for the spine have developed over the past 50 years. During that time, there have been several paradigm shifts with respect to techniques. These techniques evolved by incorporating state-of-the-art engineering principles, in vivo measurements, anatomical structure-function relationships, and the scientific method. Multiple parametric studies have focused on the effects that the experimental technique has on outcomes. As a result, testing methodologies have evolved, but there are no standard testing protocols, which makes the comparison of findings between experiments difficult and conclusions about in vivo performance challenging. In 2019, the international spine research community was surveyed to determine the consensus on spine biomechanical testing and if the consensus opinion was consistent with the scientific evidence. More than 80 responses to the survey were received. The findings of this survey confirmed that while some methods have been commonly adopted, not all are consistent with the scientific evidence. This review summarizes the scientific literature, the current consensus, and the authors' recommendations on best practices based on the compendium of available evidence.

[State of the art of lumbar intervertebral disc replacement]

Lumbar intervertebral total disc replacement is becoming more commonly employed for patients with degenerative disc disease as an alternative to spinal arthrodesis. Postulated advantages for the patients are motion preservation and height restoration in the affected segment, preventing adjacent level degeneration. Although studies show short and mid-term results which are comparable to spinal fusion, to date the long-term outcome is not clear. The different types of artificial discs and the current status of lumbar disc replacement are described.

Degeneration model of the porcine lumbar motion segment: effects of various intradiscal procedures

In an experimental study with 18 minipigs, we have tried to establish a model for the standardized evaluation of mechanical, histological and radiological phenomena of degenerative and reparative processes within the lumbar motion segment. Comparing different operative techniques revealed that the intradiscal application of hyaluronic acid into the nuclear defect is likely to enhance the regeneration process. Using the measurement of disc compliance, a semiautomatic picture analyzer and a new semiquantitative disc score could make future studies more comparable. From this basis, the intradiscal application of hyaluronic acid deserves further evaluation.