Disc Replacement Will Soon Surpass Fusions as Surgical Solution

By Deborah Schenberger, Ph.D., Nerac Analyst

For years, patients’ only option to relieve chronic, debilitating lower back pain was spinal fusion. However, in the past 10 years, orthopedic manufacturers have introduced a broad range of artificial disc replacements that promise to eliminate pain and restore motion. Even so, opportunities are there for innovative companies to apply new materials and technologies to an expanding market.

In the United States alone, surgeons perform over 400,000 spinal fusion procedures each year, using metal instrumentation to fuse two vertebrae into one. The metal instrumentation, consisting of plates, rods, and screws, physically immobilizes the two vertebrae. The surgeon imbeds a bone growth factor to stimulate bone to fuse around the instrumentation. After about four months, the two vertebrae act as one, and the patient is free to return to normal activities.

Fusion Works, But There Are Side Effects
In the lower lumbar, where the spine has very little natural range of motion, fusing two vertebrae has only a minor effect on this range of motion. In most cases, pain is relieved and patients have better performance scores than before the surgery.

As with most medical procedures, however, spinal fusion has side effects. Because the two vertebrae are immobilized, the loading on the two vertebrae’s end plates is altered, and that can lead to the end plates failing at adjacent vertebrae. As a result, surgeons have been eager to find a solution that would not alter the loading. One solution comes from the development of the artificial disc replacement.

Artificial Discs Offer a Viable Alternative
An artificial disc replacement, or total disc replacement (TDR), removes the herniated or degenerated natural disc between two vertebrae and inserts one that either allows for some range of motion using a metal or polymer assembly or allows for cushioning and some range of motion using an elastomer.

Based on results from the past 10 years, TDR procedures show promise. More than 70 percent of patients experience pain relief similar to or much better than spinal fusion. Even more promising, these artificial disc implants more closely match the function of the natural intervertebral disc, and thus the loading on the adjacent vertebrae is much less altered. So far, it appears that the need for subsequent fusion of the adjacent vertebrae is significantly reduced, which constitutes a major benefit to patients.

New Materials Could Lead to Market Share
Artificial disc replacements are ideally suited to new materials. Ultra high molecular weight polyethylene, cobalt chrome, and titanium have been used for years in orthopedic implants, but early results on TDR have shown that some discs tend to spontaneously fuse at the site of the artificial disc replacement, defeating the purpose of allowing for some mobility. Other TDR discs have deteriorated in the spinal region or have fractured. Some new thinking on alternative materials is needed to overcome these problems to bring the TDR success rates up to 90 percent or higher.

With over $1.8 billion spent on spinal fixation and dynamic stabilization devices in the United States in 2006, and with a projected annual growth rate of over 10 percent, this market is expected to reach more than $3.2 billion by 2012.

Although orthopedics is an established market, artificial disc replacement is still very young and mobile. Entrepreneurial companies are vying for their share of this lucrative market, but plenty of room remains for innovative medical device companies to capitalize on this opportunity.