I'm looking into the possibility of having a disc replacement at L45. I know there are two basic implants available. Is there any great advantage of one over the other?
Total disc replacement (TDR) for disc disease degeneration (DDD) is a fairly new treatment method available. We have only just begun to scratch the surface in understanding how well these implants work and how one compares to the other.
There are two metal-on-polymer implants: the ProDisc II and the CHARITÃ. The most important factor in outcome is probably the surgeon's familiarity with the procedure and surgical technique. Most surgeons choose one implant device to become familiar with and gain experience using the one selected.
Having said this much, let's look at the known differences between these two implants. The ProDisc II is a constrained device. This means it is implanted into the bone with very little movement of the implant allowed inside the disc space. Despite front-to-back and side-to-side forces, the implant stays in one place. It is necessary to distract the two vertebral bodies more to insert the implant than with the CHARITÃ.
The CHARITÃ model is unconstrained. This gives the patient greater spinal range of motion but also puts the person at risk of an implant dislocation. It depends on the facet joint to maintain stability. But that puts more potential stress and strain on these joints.
Both the ProDisc II and the CHARITÃ allow axial rotation (twisting) motions. There is some concern that this feature can cause further facet joint damage. Some early studies suggest that changes in the facet joints are likely at the level of the implant. Researchers will be following patients to see if anything comes of this as more time passes.