Wednesday, September 16, 2009

Dynamic Stabilization, The New, New Thing!

Instability in the lumbar spine associated with mechanical pain is poorly understood. Despite several years of research, no clear relationship exists between low back pain and abnormal movement. Over the years, it has become evident that no one can agree on what magnitude of motion is needed to preserve the "Neutral Zone." Since the Almighty made us in all different shapes and sizes how does the surgeon determine each individual's range of motion?

If instability or abnormal movement is the root cause of back pain, then, spinal fusion would always be successful in relieving back pain. So where does that bring us? It has become quite evident with the rash of recent articles that Dynamic Stabilization is the "New, New Thing!"

It seems that Stem Cells and Dynamic Stabilization are first and foremost on the agenda of our industry. Yet, many surgeons are the first to admit that when it comes to consensus, everyone agrees to disagree on biomechanics when it comes to Dynamic Stabilization.

So the Spine Blogger needed to pose the following questions;
  • How much control of motion is desirable?
  • How much load should be shared by a system to unload a damaged disc?
Short-term results are not a barometer of an implants efficacy. Long-term concern is about the implant failing in view of constant motion of the stabilized segment, witness by failure in the Dynesys a few years ago. A load-sharing device should be uniform during the entire ROM. A discrepancy in the kinematics between the implant and the motion segment will lead to variability of load-sharing.

So where does that leave us? It leaves us with a host of old and new products that are attempting to answer questions and create a niche market so that surgeons can stage a patient's modality of treatment. Yet, why all the publicity? In all likelihood because there are many early-growth stage companies that have IP on different designs for DSS and they need CAPITAL to execute. The Spine Blogger wants to know what its readers believe?


  1. The primary purpose of almost all Dynamic systems is not to unload/repair/rehydrate a damaged disc. In other words if a patient presents with DDD, implanting any dynamic system and failing to address the disc is just nuts. There isn't a company out there promoting that approach.

    Interesting discussion but most of your assumptions are flawed. Dynamic systems do not presume to "figure out" a neutral zone, but rather to support/splint the spine in the state the spine wants to rest. In other words the construct works with the spine rather than the spine being forced into the construct (like almost all rigid systems).

    Dynesys is the pioneering system in this field. There are good and bad studies (plenty of each that are flawed), but Dynesys is still on the market. There needs to be much much more USA based research (much more rigorous standards than in Europe).

    Interesting that Globus and Danek have brought more than one system to the market, only to pull them off because of the high number of failures (Globus --ProTex, Accuflex rods & Danek -- Equation, Agile).

    Pedicle screw based systems are not foolproof. Screws break for a variety of reasons. No system will or can escape this. There are just to many variables from surgeon technique to patient compliance.

    The reason for the "hype" around DSS is experienced spine surgeons realize that once you impose a rigid fusion construct on a motion segment, there is no going back. If you can buy the patient a little time with a soft fusion or non-fusion ... who knows what disc regeneration product is coming down the line a few years from now? I do agree that every VC firm out there is throwing cash at a lot of truly awful "dynamic" systems . . . just walk around NASS this year and I'm sure it will be much worse than last year.

    IMHO the biologics segment is the holy grail of spine . . . if you can figure out disc hydration/regeneration, nucleus replacement/regrowth and annular repair . . . good grief, you couldn't make enough of the stuff.

    Just found your blog tonight . . . Good Stuff. Please don't take my comments personally ... it's just business talk.

  2. Thanks for the commentary! It's great to have our readers respond providing for stimulating dialogue. Hopefully, others will chime in! PS: It's never personal, it's business!

  3. Besides Dynesys, what other DSS are approved by FDA?
    Isn't Dynesys only APPROVED for fusion?

  4. Dynamic stabilization systems will come and go once each company that has invested in the technology achieves it's ROI. IMHO, No one will ever show it is any better then fusion and more than likely not quite as good. Complications will pile up over time. So may other technologies have followed this path, e.g. BAK cages as stand-alone and IDET.