Over the years, there has been a lot of focus on the height of the prosthesis and amount of disc height restored. Some discs are shorter than others. Some discs requre less 'over disctraction' to install.
As I began to focus on this more and more, I noticed something very significant. While we were all talking about the need for shorter prostheses, I kept watching surgery after surgery, in which the shortest height cores were not selected. The size and location of the prosthesis should match the best fit achieved with the most appropriated sized trial implant and very careful attention paid to getting it right. For devices with selectable core heights, like Charite', Activ-L, ProDisc... the height of the core selected will be determined by the tension on the system. The doctor will apply the appropriate amount of force to the distraction too and the disc space will be distracted to a distance that will be determined by the patients' anatomy.
If the surgeon would be focused on selecting the shortest core possible instead of selecting the most appropriate sized core for your anatomy, the result would be decreased stability and increased risk of migration, increased risk of facet degeneration and probably other complications as well. (I'd like to research and write more... but can't now.)
I've seen the TSMS surgery a few times... very interesting. This is not to be thought of as an opportunity to do a posterior implantation of an ADR. This is for people who's posterior elements are too far gone to be a candidate for ADR. (Maybe future systems will provide posterior ADR implantation as a first choice... but I don't think this is it.) From what I've heard, the facet replacements are going well because facet pain can be so pronounced and straightforward to confirm. Longevity of the implants and the entire system is something I look forward to seeing good results for, but remains to be seen. (Unfortunately, we are not typically in a position to wait a decade or two before we choose our poison.)
All the best,
Mark
|