Fusion vs Disc Replacement for Discogenic Pain: Part 3

There is a complex nature of back pain in its relationship to surgery and less than ideal outcomes are often related to poor indications, rather than the technology or techniques themselves. There are many designs and concepts for spine arthroplasty, but most of the current world experience is with the Link SB III Charité (Link Inc.) and the ProDisc Modular Total Disc (Spine Solutions Inc.) [Figure 4]. From a biomechanical point of view, preservation of motion is considered to be more important than load distribution and damping effect. Each of these implants is characterized by a three-component modular design consisting of two metallic endplates and a polyethylene insert. Both of the implants have a primary goal of obtaining and maintaining distraction of the motion segment. An estimated 3,000 implantations have been described in the two designs. The reported clinical results have been promising and future prospective clinical trials will be available in the near future.

Figure 4
Artificial disc (ProDisc Modular Total Disc, Spine Solutions, Inc.)

Further scientific research will be needed to assist in many areas to include:

•Morphological Factors influencing outcome?

•Disease of the posterior column of the motion segment?

•Behavior of the implants at 5, 10, and 20 years?

•Adjacent level disease with motion preserving implants?

•Influence of the center of rotation?

•Revision Strategies of Arthroplasty?

•Contraindications for Arthroplasty?

Summary
There will always be a role for spinal arthrodesis in deformities or unstable conditions. However, spinal fusion for the management of degenerative disc disease in the absence of instability and deformity, though performed quite frequently, is not universally accepted by our patients or society. Despite extensive research, engineering, and pre-clinical testing, the ultimate safety and efficacy in spine arthroplasty can only be determined by performing clinical studies. Strict regulations and the unfortunate litigious environment of the United States creating increased costs will slow the development of this technology and its ability to treat many suffering patients.

Indeed, many unanswered questions about the precise indications, techniques, survivorship, and revision strategies of spinal arthroplasty need to be further clarified. But, this is a result of general deficiencies in understanding the axial/discogenic pain mechanisms and precise methods of diagnosing pain generators. Progress in implant development, the acceptance of, and clinical routine in less invasive surgical approaches, as well as the result of lumbar spinal procedures have initiated a willingness for scientific discussion, and clinical acceptance of new ideas and technology.

We are at the beginning of another period of technology explosion in the field of spine surgery, which can be compared to the "Charnley era" in the development of hip arthroplasty. There are many obstacles to overcome, but the clinical need is compelling and the potential for spine arthroplasty is great. It is therefore, reasonable to apply this advancing technology to the spine pathologies and create a new gold standard, allowing our patients to preserve motion and function with symptomatic degenerative diseases.