This is a subject I've given a lot of thought to, and have had some significant results exploring.
Please forgive the long post, and any factual errors. This is all just based on my imperfect understanding, from what I have learned or misunderstood along the way.
Let me say first off, I think these procedures will likely only work for discs that are still relatively healthy--have good height and relatively intact annulus. So, it may not be of interest to ADR candidates. On the other hand, it may be a way to address levels still responsive to such therapies, thus limiting the number of levels needing ADR, and/or eliminating sources of pain that are not considered appropriate for ADR.
My understanding is, discogenic pain--low back pain originating from the disc--is probably coming from tears in the annulus. Only the outer third of the annulus is innervated, so that is the only part of the disc that could be generating pain.
So how to heal an annular tear?
IDET
One approach is IDET (or similar procedures, like Dr Yeung's SED), in which the tear is heated, causing the collagen fibers of the annulus to seal up (I am probably describing it badly). That procedure had uneven results, and is not something I personally would pursue.
DISC INJECTION
Prolo solution
This is an injection procedure that I have tried, with significant results For want of a better name, the procedure is sometimes called "prolotherapy to the disc." If you have never heard of prolotherapy, it is the injection of a dextrose solution near an injured ligament, to strengthen and tighten it. The dextrose acts an irritant, causing a localized injury that stimulates the body's normal physiological healing response, resulting in the formation of scar tissue. I have had prolotherapy done, and it does do what it says it does, you can feel it. (Whether prolotherapy can help back pain is another subject.) I credit prolo for correcting some wobbliness from too much chiropractic.
Here are links to two published studies of disc prolo.
one study other study
A disc is made of collagen fibers, virtually the same as ligament tissue. So, the reasoning behind disc prolo goes, why not inject the prolo solution (dextrose) into the disc, to induce healing of the annular tear? I have had this procedure done, and I truly think it works. The improvement is not as dramatic as an ADR or fusion, but for me it was significant and much appreciated.
The theory of induced healing may sound far-fetched, but the improvement I got came on over a three month period, consistent with organic healing. It lasted a long time, until I started putzing around with other procedures. Unfortunately, while the first two disc prolo injections had positive results, additional injections (I had the fourth about a year ago) have brought on a side effect that has worsened my situation, namely, that my back is now sensitive to pressure, as a result of which I am unable to tolerate my previously comfortable back chair.
Growth hormone/stem cells, etc.
Somewhat similar to the disc prolo is injection of other materials designed to kickstart healing. Stem cell therapy seems the obvious, likely future direction here. The Microspine clinic recently tried injections of "precursor" stem cells (hematopoietic cells), but reported no positive results. It's not clear if the intended target in the Microspine study was annulus or nucleus tissue or both.
There is now a study in Los Angeles looking into intradiscal injections of growth hormone. I think it's worth checking out, free if you participate in the study. And despite my mixed experience with a similar therapy, I think it's relatively risk free.
Can therapies aimed at the nucleus help?
There are also a number of therapies aimed at the nucleus. So what is the role of the nucleus in discogenic back pain?
The nucleus is not innervated, so is not itself a pain source. Its material is caustic, and can cause chemical (as opposed to mechanical) back pain, if leaked out through an annular tear onto the nerve root or other innervated tissue. Perhaps replacing the nucleus with a prosthetic works by eliminating the caustic matter. But, would nucleus replacement have any value for mechanical back pain?
Given that the outer one-third of the annulus is the only innervated part of the disc, I continue to believe the annular tear must be the source of the pain. What role does the nucleus play in this pathology? For we do know that nuclear degeneration is a common feature of DDD: Just as we can see the annular tears on the CT scan, we see the black disc--degenerated nucleus--on the MRI.
My guess, degeneration of the nucleus may be responsible for annular tears not healing by themselves. The annulus does not have a blood supply; it gets its moisture and nutrients by diffusion from the vertebral endplates through the nucleus. (Not surprising that the disc, with such poor prospects for self-healing, is a common source of chronic pain.) So, is there a therapy or prosthesis that can make the nucleus serve more effectively as a transporter of nutrients to the injury?
Nuclear replacement
According to an exhaustive report of new spine devices coming to the market
spine industry report , some new nuclear replacements devices are indeed designed to mimic the nucleus' function of transmitting nutrients to the disc. The Raymedica PDN-Solo, for example, is designed to "restore physiological function of the nucleus by osmotically absorbing and emitting fluids, allowing a fluid transfer between the vertebral bodies." Another device employing a hydrogel, the Neudisc, claims "The hydrogel's ability to rehydrate itself mimics an important characteristic of an intact nucleus pulposus [namely, pumping up at night, and pumping fluid out during the day]... The "pumping action" of the hydrogel closely mimics the nutrient cycle that is constantly ongoing in a natural disc." "The value of the Neudisc and PDN hydrogel technology is the ability to mimic the intact nuclear material's ability to "uptake" water, continuing the nutrient cycle through the vertebral endplates."
Raymedica claims patients report as much as 70% pain/function improvement, with 80% reporting improvement. (Manufacturers' stats, of course)
By contrast, non-hydrogel devices (e.g., the DASCOR, a polymer that is injected and expands to fill the patient's disc space, curing in place), seem to only mimic the loading and flexibility properties of the nucleus, not its permeability. "[The DASCOR is] designed to treat DDD by simulating the physical structures in the nucleus and restoring disc height."
The hydrogel PNDs sound very encouraging to me, perhaps paired with therapies directed at the annular tissue, discussed above.
Autologous chondrocyte transplantation
In this therapy, cells are taken from the patient's nucleus and cultured in a lab, then re-injected. This therapy can be done in conjunction with a discectomy (to correct a herniation), and is also being studied as a low back pain therapy. Perhaps the procedure reverses degeneration in the nucleus, restoring function.
study
There does seem to be a limit to the effectiveness of this therapy, at least in theory. In one brief article I read, researchers elected not to pursue this therapy, due to the "senescence" of the cells used for culture. If I understand this correctly, this means the cultured cells would be effective to restore nuclear function, but would have a limited life span. Still I say, if the therapy gave you two or three good years, it would be well worth it.
Here again, it would seem that stem cells may be the future. Senescence should not be a problem with stem cells.
Endplate abrasion
Alphaklinik does a procedure where they abrade the endplates, on the theory that it is calcification, etc. on the endplate that stops the flow of nutrients to the disc. Other than AK's website, I have read nothing about the efficacy of this procedure.
So
What do you think?