Memo sent from Dr. Dorr to the American Association of Hip and Knee Surgeons that deals with what he feels is the cause for the hip implant failures:MEMO DATE: 4/22/08 TO: American Association of Hip and Knee Surgeons
FROM: Larry Dorr, M.D.
RE: This NOTICE is to inform you that we have had ten revisions in 165 hips and have four more that need to be revised using the Durom cup (Zimmer, Inc)This failure rate has occurred within the first two years. In the first year the x-rays looked perfect. We have revised four that did not have any radiolucent lines or migration (and John Moreland revised one). These early cups fooled us, but the symptoms were so classic for a loose implant that we operated the patients. When we hit on the edge of the cup it would just pop free. As time goes by the cups begin developing radiolucent lines. We now have one cup at two years that has actually migrated a short distance. It has tilted into varus. We do not believe the fixation surface is good on these cups. Also there is a circular cutting surface on the periphery of the cup that we believe prevents the cup from fully seating. We stopped using the cup after the first revisions.We have notified Zimmer. The FDA has been notified and we will notify them of our continued revisions. The company does not believe it should pull the cup from the market so I am notifying all of my colleagues of our failure rate with this cup. I went through a similar scenario with the Sulzer cup failures where I was the only one experiencing revisions at the beginning and basically it was assumed that it was our technique. I can assure you that this goes beyond technique. I learned my lesson in not informing everyone about this magnitude of failures with the Sulzer cup problem, so it is my obligation to do so with this cup.Dr. Dorr is a world renown orthopedic surgeon and Director of the Dorr Institute for Arthritis Research and Education.