Later, I'll expand on this post and create a separate thread for 'posterior stabilization behind ADR'. I'll respond briefly now. This post is not specific about Justin's case, it's just a discussion of (my laypersons understanding) of the theory behind this sort of revision surgery.
My experience with this goes back 5 years as I've had 3 clients with Dynesys implanted behind ADR (2 Charite, one ProDisc). I've also been fortunate enough to attend the surgeons training for DSS and have observed many procedures involving DSS, Dynesys, Coflex and other posterior stabilization systems. I've also literally hundreds of sessions at the conferences on various posterior stabilization systems.
It should be kept in mind that when you get to revision surgeries, EVERY ONE IS DIFFERENT! Dynesys implanted behind prodisc that was done in spite of a pars defect has no relationship to Carmont's Dynesys implanted behind horribly tilted 2-level Charite that was a problem because of terrible placement by a less than careful surgeon, which has no relationship to Justin's anomalous bone defect behind a nicely implanted ProDisc.
I've successful and unsuccessful stabilization attempts. NONE were in cases even remotely similar to Justin's.
DSS is quite a bit different than Dynesys. A very important feature is the modular design that allows easy conversion of a dynamic segment to a fused segment, reusing the pedicle screws and associated hardware, simply swapping out the dynamic coupler with a fusion coupler.
DSS implantation with a modified Wiltse approach (developed by Bertagnoli) allows for a very low invasive surgery using muscle splitting techniques (separating the muscles along fascia layers) instead of more traumatic cutting of the great muscles in your back. It' very impressive when contrasted to the more invasive techniques.
DSS is solid hardware. The motion coupler has a calibrated, springlike motion segment that allows continued motion, while restricting it within a 'neutral zone'. Your pain and problem likely occur when you move out to extremes in your range of motion. Offloading the facets by restoring appropriate spacing in the posterior elements and allowing continued motion while restricting to a neutral zone, allows us to have motion preserved, while protecting the system with the additional support from the DSS hardware.
This additional support while restricting the range of motion to the neutral zone gives the surgeon license to do a wider decompression than she might have been comfortable doing in a patient without the extra support of the 'posterior stabilization' hardware. Without it, if they remove too much, they destabilize too much.
Justin's films are quite dramatic. Note that the axial slice (top right in original post starting this thread) is NOT a slice that reflects the biggest part of the defect. It's the lowest slice before the artifact from the prosthesis obliterates the image. A lower slice will reflect an even bigger defect. The reference line from the image on the left shows where the slice is... all the way to the edge of the keel.
I hope Justin will explain more about the origin of the defect. Is it related to the ADR or is it something unique in his history?
Again... more later in a different thread.
All the best,
Mark
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