Zimmer's New Augments: A Confirmation of NexGen Knee Failure?

Warsaw, INProblems with some components in the Zimmer Knee Replacement product line were highlighted indirectly May 17 when the Warsaw, Indiana-based manufacturer touted a new product line designed to aid doctors in revision surgery.

According to PR Newswire, the company has issued a series of Trabecular Metal Material augment shapes and cones designed to address defects identified as small to large cavitary bone defects often encountered during revision surgery. The augments, according to Zimmer, would also provide a structural foundation to existing bone and aid in supporting revision knee implants.

The irony, according to some legal experts, is that many revision surgeries are needed following the early and unexpected failure of some of Zimmer's products. Specifically, the Zimmer NexGen CR-Flex Porous Femoral component has been found to begin failing early within its normal window of life expectancy.

Revision surgeries are not unique, and are required when a prosthetic joint wears out over time. If, and when, a knee implant fails well before its time, revision surgery occurs much sooner.

Some, but not all, of the various "pieces" in the Zimmer NexGen product line have been the subject of a Zimmer knee replacement recall. The Zimmer NexGen CR-Flex Porous Femoral component has been particularly troublesome due to the fact cement is not used to fuse the replacement knee to the bone. Instead, it was anticipated that the prosthetic knee would bond through the ingrowth of bone with the porous material in those particular Zimmer knee implants.

The ingrowth, in some cases, has not proven to be either robust or permanent, and joints have begun to loosen or fail earlier than the anticipated 15-year life cycle of the knee implant.

Some legal observers see the May 17 release of products to augment revision surgery as a confirmation that some components in the Zimmer NexGen system are prone to early failure.

Zimmer's Trabecular Metal material is described by Zimmer as a highly porous biomaterial that resembles the structure, function and physiology of trabecular bone. Zimmer, in its release, lauds the material as being supported by a wealth of peer-reviewed, published clinical data. In the same paragraph, the company refers to the material as "novel."

The cemented versions of the Zimmer NexGen Knee, which bonds the device to the thighbone using cement, has not been associated with the same degree of failure as the NexGen Knee that relies on bone ingrowth in association with porous biomaterial.