Zimmer Hip Failure: What is Wrong with the Device?
In April 2008, Dr. Lawrence Dorr of the Dorr Arthritis Institute wrote an open letter to US orthopedic surgeons warning about dangers posed by the Zimmer Durom Acetabular Component (Durom Cup) – a popular hip replacement part that had been on the US market since 2006. In July 2008, Zimmer suspended sales of the device, which had been implanted into more than 12,000 US hip replacement patients.
What was wrong with the Zimmer hip device?
First, some background. The Durom Cup is an acetabular component – one of two components that make up a hip replacement system. The acetabular component fits into the cup-like depression of the hip bone and holds the femoral component of a hip replacement system in place.
In most Durom Cup hip replacement systems, a Zimmer Matasul Metal-on-Metal Tribological Solution Large Diameter Head (LDH) is used as the femoral component. There have not been any widely reported problems with the femoral component used with the Durom Cup.
But according to Dr. Dorr, the Durom Cup does not properly fuse to the hipbone. “When we hit the edge, it would just pop free,” he wrote of a Durom Cup implanted into a hip recipient who experienced Zimmer hip failure. The problems with the component appear to originate with the Durom Cup’s fixation surface – a coating made of plasma-sprayed titanium designed to noninvasively fuse the device to bone.
Zimmer Hip Failure – Defective Fixative
“The fixative doesn’t do its job,” Dorr said. The coating on the Durom Cup failed to properly hold the device in place, resulting in “radiolucent lines” – space between the bone and the device visible by X-ray. In at least one case examined by Dorr, the Durom Cup migrated within its hipbone seat, changing the angle by which the femoral component of the hip replacement system can move.
In the study of 165 Durom Cup recipients, Dr. Dorr found an alarmingly high rate of Zimmer hip failure. 14 patients required hip revision surgery – a second hip replacement – within 2 years. The Durom Cup is supposed to last 15 years or more.
In healthy hip replacement recipients, the acetabular component of the system stays fixed to the hipbone, allowing patients to live with reduced pain and greater mobility than they had before hip replacement surgery.
For Durom Cup recipients who have experienced Zimmer hip failure, revision surgery is little consolation. The procedure is more complicated than the original surgery and recovery time is usually longer.
Today, Zimmer hip litigation is consolidated in a New Jersey federal court, where hundreds of plaintiffs may receive millions of dollars in compensation for Zimmer hip failure.