Ten years ago I saw a program on artificial disc replacements. Seems like they are finally coming on the market. What's the hold up?
Researchers have faced many challenges with disc implants. They have to find a material that is biologically compatible with the body. It has to be able to withstand the forces of time and activity. Scientists are trying to develop an implant to last 40 or more years. They figure that adds up to 100 million cycles of movement just based on how far the average adult walks in one year.
The implant can't fracture or fail due to fatigue. It must fit into the disc space easily without sliding around or sinking into the bone.
Each implant type is tested on human cadavers, animals, and then live humans. Complete disc replacements are being used now.
The latest designs are trying to just replace the center of the disc. This is called the nucleus pulposus. The goal is to develop an implant that mimics the human disc's ability to change shape or size. Most discs absorb water when the body is at rest. The water helps the disc keep its height and hold up against loads and forces. As the human stands up and moves around, the excess fluid leaks out of the disc.
This type of device is implanted in a dehydrated state. A much smaller incision and less invasive operation is possible. Once the device is in place, then it can absorb fluid to restore its height. Studies have been done on rabbits but not humans.