Tuesday, October 6, 2009

Dynamic Stabilization, An Adjunct to Fusion? So What's The Difference?

Recently, OTW completed a three-part series on Dynamic Stabilization (DS) which was highlighted by the contribution of three esteemed leaders in the study of spine biomechanics, Drs. Panjabi, Goel and Patwardhan. Dr. Panjabi is respected as the "guru" of spine biomechanics, and was the visionary behind the Applied Spine Stabilimaxx NZ, while Drs. Goel and Patwardhan have provided bio-mechanical guidance and contribution to the development of other companies DS products.

The theme behind this series was to "better define" the design rationale behind the development of DS products and how it may benefit the patient. These scientists believe that somewhere in evolution of spine treatment there is a place for Dynamic Stabilization in the surgeons armamentarium. Yet, the question must be posed; "Is there really a middle road between total disc arthroplasty and fusion?" It is difficult to dispute the bio-mechanical findings that these scientist have developed over the many years of their lives studying the spine. Yet, today, the industry has many believers some genuinely sincere with academic intent, some who have drunk the kool-aid purely for financial reasons, and some that are skeptics. For those of us that are on the outside looking in, there are many questions regarding DS that need to be answered.

If the reader looks at the indictions of the five companies that are featured in this series, they may seem clear to the writer, yet, they are not patient specific. Yes, the indications are the same, "Adjunct to fusion in the treatment of chronic instabilities or deformities of the spine." To the reader, the terminology belongs to the state-of-the art, yet, it is nebulous and runs the gamut from "A to Z." Therefore, what are the appropriate indications, so that the surgeon and patient can optimally benefit from the implantation of these products? It seems that everyone involved in the development of these products spends more time on differentiating their individual design's features and benefits, rather than focusing on the patient's indications. If the leaders in DS haven't clearly defined, nor agree upon the theoretical aspect and optimal design, how can surgeons make the appropriate decision when they themselves agree to disagree?

Retrospective data tells us that surgeons that have used some of these products ultimately have had fusion (Dynesys) along with screw breakage (Dynesys and AST). In addition, inventors have experienced an evolution in the design and manufacturing process of their implants, witness by discussion centering on HA or Ceramic coated screws and dual shot peen vs grit blasting finishing. Eight to Nine years ago Total Disc Arthroplasty (TDA) was the future, I can still hear Tony Viscogliosi's hypnotic voice, then, the industry realized that there were far too many clinical variables on an individual patient basis, the industry moved in a different direction, interspinous process devices became in vogue, PEEK exploded on the scene resulting in the commoditization of interbody devices, facet replacement surfaced, today, the industry is selling Dynamic Stabilization as the new frontier. Yet, if all these devices are an adjunct or supplement to fusion why can't the industry agree on how to effectively use these products? Unlike the patient, the laboratory can be predictable, whereas, each individuals clinical diagnosis changes on a case by case basis. If Dr. Panjabi believes that structural preservation of the spine is important, how do we justify some of the other posterior designs, i.e. Impliant and Facet Solutions?

In closing, the Spine Blogger remembers sitting next to a surgeon at an emerging technology meeting, as the surgeon speaker was finishing his presentation, this prominent surgeon leaned over to me and said, "maybe if we resect as much of the anterior and posterior elements of the spine and replace them with hardware, we will truly eliminate pain!" Sometimes, the reader and the audience gets the feeling that we are still looking for the right indications. The Spine Blogger wants to know what its readers think?


  1. The FDA updated the list of 522 Postmarket Surveillance Studies to include 16 DS systems on the market.


    Sort by "Date 522 Order" Date is 10/05/09

  2. How can one look for the right indication if nobody knows what for example "discogenic back pain" actually is? And having selected the wrong patients is the eternal excuse why the results of a given system are not as stellar as originally predicted. These two facts combined are the cause that the spine is being assaulted by an incredible number of contraptions, most only minor variations on a few themes. And almost all made by people who hope to make a killing when their "brainchild" gets picked up by one of the big companies. It is amazing how effective old procedures and technology still are in patients with clear anatomical abnormalities that can be directly correlated to their symptoms.

  3. Cerevertebral: Amen Brother! No need to say anymore!