Biomechanical Assessment of Nucleus Replacement Devices

Globally, low back pain is the leading cause of disability with a lifetime risk of 75%. It is estimated to cost £500 million to the NHS annually, and there is a strong association between low back pain and degeneration of the intervertebral discs (IVDs) that lie between vertebra in the spine. In patients who have a degree of IVD degeneration that is not severe enough to warrant total disc replacement or fusion, but sufficient pain to warrant surgery, nucleus (partial IVD) replacement is an alternative, less invasive, treatment.

Currently nucleus replacement devices (usually a hydrogel), are surgically inserted into the IVD through the annulus fibrosus (AF) that surrounds the nucleus. A common complication with this approach is that over time, the device is squeezed back out through the hole made in the AF. It is hypothesised that changes in the surgical approach, materials used, and design of the nucleus replacement will enhance its biomechanical performance, however, there is currently no standardised method to scientifically assess the performance of different nucleus replacement designs.

This project aims to develop a rigorous testing protocol that allows the effect of changing the design of the nucleus replacement (for example materials, surgical approach, design concepts) on the response of a motion segment to be quantified and compared.