Back Pain and Degenerative Disc Disease: Are Artificial Discs the Solution?
There has been considerable excitement among surgeons as well as patients following the recent FDA (Food and Drug Administration) release of the Charité Artificial Disc (DePuy Spine, Inc.). The excitement among patients with degenerative disc disease stems from the impression that there is now a safe way to eliminate pain from degenerative discs while at the same time maintaining normal motion. Many of these patients have heard about others with similar problems undergoing fusion procedures in the past, who still continue with persistent pain or had more than one attempt at fusion without success or have developed additional levels of disc degeneration requiring an additional fusion procedure. They have also heard of the successful results following disc arthroplasty in Europe which has been highly publicized by the media in the United States.
Early Detection and Lumbar Fusions
This is definitely an exciting new addition to our armamentarium for the treatment of degenerative disc disease. When we look at how the evaluation and treatment for degenerative disc disease has developed over the past few years an almost unbelievable amount of progress has been made. We now are better able to identify disc disease early on with MRI and pain generators with discography and facet blocks. Where only a decade ago, lumbar fusions were being performed through large posterior incisions, now they can be performed percutaneously through incisions that are barely visible either anteriorly through the abdomen or through the back. With the use of presently available instrumentation, success rates for one level fusions approach 90-95%. Unfortunately, not every patient who has degenerative disc disease and has a successful fusion has a successful clinical result. There is still a group of patients for whom fusion does not effectively alleviate pain.
Disc Replacement: Risks
Disc replacement arthroplasty has the potential for the treatment of many of the spinal motion segment disorders that are currently being treated both successfully and not so successfully by one of the many fusion techniques. At this relatively early stage of disc replacement development, we do not know all of the problems that may be encountered following these procedures. Because the surgical approach is through the abdomen either retroperitoneal or transperitoneal (around/through the stomach), there are some predictable complications including vascular injury, thrombophlebitis (vein inflammation accompanied by blood clot formation), nerve root injuries, injury to the ureter, and retrograde ejaculation in males.
We also know that a number of disc replacements have failed and have been converted to a fusion with variable clinical outcomes. The removal of artificial discs, especially at the L4-5 level, is fraught with a significant risk of vascular injury because of scarring around the prosthesis. We do not know at the present time how long these prostheses will last and how well they will function. Will they provide enough motion to prevent adjacent segment degeneration, and will the patient with multilevel disease be a candidate for this procedure? Certainly we know that artificial joints produce wear debris and an inflammatory response which escalates over time where this is obviously not a problem with fusion.
Optimism and Early Results
Spine surgeons in general are very optimistic and excited about total disc arthroplasty and appropriately so. There also will be a learning curve by both the spine surgeon as well as the access surgeons who provide the exposure. Appropriate training via courses and cadaveric labs will help to minimize the learning curve and potential complications. There will no doubt be many improvements and modifications in the prosthetic designs.
Early results are certainly encouraging in the hands of the investigational surgeons but are fraught with the many problems common to the development of a new procedure. Total disc arthroplasty is likely to be a better solution than fusion for many degenerative disorders of the lumbar spine as design improvements continue to be made and as further experience defines the indications for its use.