I had a total disc replacement six months ago. I’m very pleased with the results. I can move pain free again. However, I’m concerned because my first set of X-rays showed everything was fine. On my latest X-rays, the disc height is less at the place where the implant is located. Is this serious? What could cause it?

Disc height increases dramatically from before to after implantation of a total disc replacement (TDR). That’s good because that is what the implant is supposed to do. Restoring normal disc height takes pressure off the nearby facet (spinal) joints, too.

At first, when the implant is inserted, there is a small space between the curved, upper endplate of the vertebra and the flat top of the disc replacement plate. The two shapes don’t match exactly. Over time, the bone settles down around the implant and there’s a slight loss of space.

But it’s also possible for the implant to sink down into the bone. This is called subsidence. Loss of disc height can occur from progressive subsidence. That’s why it’s important to keep your follow-up appointments and have periodic imaging tests. The surgeon will follow your progress and let you know if the changes are within normal limits or something to be concerned about.