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Artificial Disc Replacements May Not Last a Lifetime

Despite 20 years of use in Europe, there are very few reports on the long-term results of lumbar artificial disc replacements (ADRs). This is the first study published on ADR failure from wear debris.

ADRs are made of plastic and metal component parts. Tiny pieces of those materials can flake off setting up an inflammatory response. The implant starts breaking down or causing nearby bone to dissolve, a process called osteolysis. The ADR loosens and must be removed and replaced.

In this report, four cases of ADR failure are analyzed and discussed.The patients had severe symptoms of pain and loss of function. Walking was difficult. Standing was impossible and sitting was very limited. Surgery was done to remove the ADRs. All implants showed signs of wear debris. The nearby tissue was tested for an immune response. The bone was checked for osteolysis.

They found inflamed tissue around the old and newly formed bone. There was extra blood supply and nerve fibers in the inflamed area. Many of the plastic (polyethylene or PE) particles were seen in the inflammatory tissue. Scar tissue had formed around the loose implant. PE particles were present in the scar tissue, too.

Once the ADRs were removed, the surgeon could see pitting, cracking, and brittle edges of the rim around the core of the implant. In one case, the core had fractured.

This report shows that long-term wear debris can be a problem with lumbar ADRs. Some, but not all problems were caused by the wrong size and/or position of the implant. Improved surgical technique may help eliminate some of these problems.

The authors suggest all patients receiving a disc replacement should be followed long-term to monitor the status of their implants.

References: André van Ooij, MD, PhD, et al. Polyethylene Wear Debris and Long-Term Clinical Failure of the Charité Disc Prosthesis. In Spine. January 15, 2007. Vol. 32. No. 2. Pp. 223-229.

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