But studies are ongoing to evaluate their function and outcomes. There has always been some concern about increased wear and tear at adjacent levels with spinal fusion. That's one of the reasons ADRs are used instead of fusion. Fusion stops motion at one level. The result is that there is an increased load to the next (adjacent) level.
At least in theory, restoring normal motion at the degenerated spinal level(s) should help take the load off the levels above and below. To help prove this, a special measuring device has been used to measure spinal motion before and after spinal surgery.
The device is called a six-degree-of-freedom simulator. It can be used for patients who have ADRs, fusion, or spinal implants such as the titanium cages. Measurements of spinal flexion, extension, sidebending, and rotation have been shown to be accurate and reliable. Sidebending and rotation can be measured to both the right and the left.
Preliminary studies show that a one-level ADR restores near normal spinal motion at that level and at the level above and below the ADR. It remains to be seen what the effects will be at the adjacent levels over time. The hope is that with normal motion, the load on the next level above and below will be less, too.