Artificial disc replacements (ADRs) were first sold on the market in 1987. The Charité ADR was the first one approved for use in the United States. Research is ongoing to test the long-term results of this device.
In this study, engineers from DePuy Spine (Johnson & Johnson) test how well the Charité ADR holds up with repeated cycles of movement. The moveable parts of this ADR increase the risk of tiny particles of metal debris. When the debris comes in contact with the bone, changes in the bone can lead to loosening of the implant.
All testing was done mechanically in a lab. Machines were used to simulate motion. Six disc devices were subjected to 10 million test cycles. Normal motion was mimicked as much as possible. But the authors say there may be many combinations of spinal motion that weren’t tested.
After testing, implants were weighed and measurements were taken of the height. Type and size of wear particles were also measured and studied every one-million test cycles. The results showed a very small wear rate. This is consistent with clinical reports. Symptoms from wear are not a problem typically reported by patients who have this type of ADR.
Joint wear and fatigue failure are two important safety issues with any implant. The amount of wear and debris produced by the Charité ADR is equal to (or less than) other ADRs. Wear rates were much lower than with other joint implants (for example, hip or knee replacements). Future tests will be done on the Charité device under different amounts of load and speed during movement.