The Wallis® Implant

Rationale

There are two problems that cause back pain with moderate wear and tear in the lower back. Abnormal loads through the disc and facet joints can be painful. The affected segment also becomes a little loose and soft causing abnormal movements to occur.

The disc is often compared with a car tyre. Like a good, well inflated tyre the normal disc is firm but compliant, able to absorb stresses and allow some degree of movement. Degeneration causes the disc to become soft, like a deflated tyre. Bumps and stresses are not well absorbed, jarring the back, and the disc becomes rather 'wobbly' or unstable. This instability is experienced as the back 'going', often with quite trivial movements, and can cause further damage to the disc, with tears in the outer wall of the disc developing, much like splits in the wall of a flat tyre.

The Wallis® implant reduces the abnormal loads through the disc and facet joints. It also brings the movement of the affected segment back into the normal range, reducing the instability.

Advantages

1. Minimally invasive surgery. This means no damage to the important muscles of the back, minimal blood loss (no need for transfusions), quick recuperation and early return to function.
2. No need for rigid fixation to bone with screws. This avoids the potentially serious risks of damage to a nerve root from a screw. It also avoids the risks of screws loosening or breaking.
3. Conservative surgery. No important structures in the spine are damaged or removed. The procedure is completely reversible and preserves all options for the future.
4. Maintains movement. The spine is meant to move and the Wallis® technique preserves that movement. This avoids transferring stress to other parts of the spine.

The Wallis® Implant

The implant comprises a central spacer, which is positioned between the spinous processes of the affected segment of the spine, and two bands, which pass around the spinous processes and are secured back to the spacer. The spacer itself is made from PEEK, a biocompatible material which is similar in its “springiness” to bone and so more forgiving than metal would be. The bands are made from woven polyester, which has been used for many years in other surgical implants. They limit the unwanted excessive movement, or instability, that occurs in disc degeneration. The bands also help secure the implant in place.

How is the Wallis® Implant adapted to an individual?

The Wallis® implant is available in a range of sizes and during the operation a series of trials are used to determine the right fit for an individual. Instruments are used to tighten the bands to the correct tension

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