Keel slot process

[mmglobal]

Michelle, I should probably answer your specific question.

Explanting the device is a pretty extreme measure. In the first few years I was researching ADR, it was cavalierly said, "you can try ADR and if it doesn't work, you can always do a fustion!"

As more and more people got disc replacements and we started to see revisions, it became clear that the cavalier, "just pop-em out and do a fusion" is a little understated. If you need revision surgery, whether it's from fusion, ADR or any other spine surgery, you are in trouble. However, as we learn more revisability becomes more paramount.

Even for the ADR's that can be removed obliquely, like the Charite', there is high motivation not to explant the prosthesis. For most failure modes, fusion will mean adding posterior instrumentation - pedicle screws and rods... leaving the ADR as an interbody spacer. More and more, we are talking about adding motion preserving posterior hardware, instead of just fusing... but the jury is still out on this as experience is very limited. Also, each case is something of a one-of-a-kind surgery.

If the prosthesis must be removed, then there is a big difference from one device to the next. As mentioned above, an all metal device with a tall keel will be difficult or impossible to explant without destroying a vertebral body. Next most invasive will be a keeled device with a tall keel and a poly core. If the keel is short enough to clear the keel without too much distraction, the keel is not an issue. Then, short keel devices... then no-keel devices.

Revisions without fusion may be possible... but as I said above... each surgery is a one-off.

Mark