While the primary difference between the DePuy ASR hip implant and the DePuy Pinnacle hip implant lies in the fact that the ASR was recalled on August 26, 2010, there are significant design differences between the two implants. Both implants have labored under adverse reports from recipients. An article in the British Medical Journal profiled some of the problems associated with the DePuy Pinnacle; the design was altered to increase the size of the femoral head and shorten the stem. These changes were made without benefit of clinical trials therefore it was unknown whether the changes would be either safe or effective. Further, no post-market studies were conducted which would have detected potential long-term problems with such a change in design.
Unlike the Stryker Rejuvenate, both the ASR and Pinnacle are considered monoblock designs although the ASR is more of a hybrid monoblock, allowing the surgeon to fit the recipient with the proper size acetabular cup and ball. Once those dimensions are determined, the ball is placed on the ASR stem and implanted into the patient. Modular systems such as the Stryker Rejuvenate go a step further and offer various sizes and angles of stem, neck, ball and cup. The Pinnacle design is similar to the ASR, however there is a choice of the type of liner used: plastic, metal or ceramic. The metal liner used in the Pinnacle is called an Ultamet, and, just like the recalled ASR, the FDA never specifically approved the Pinnacle hip system for use with a metal liner.
Soon after DePuy launched the Pinnacle hip implants failure reports began coming in. In 2004, DePuy responded (somewhat) to the adverse reports by shortening the taper to allow a few degrees of greater motion, adding grooves to allow surgeons to use them with ceramic or metal heads. These changes, coupled with bigger femoral heads caused increased wear and higher rates of implant failure, proving that even a minor design change can cause major problems. Generally, regarding the Pinnacle, when the metal liner has rubbed against the metal ball, causing metal ions to shear away and enter into surrounding tissues or the bloodstream, problems occur which require a revision surgery. This revision surgery is relatively mild compared to other implant revisions in that the hip area is opened up and the metal liner is replaced with a ceramic or plastic liner. The surgery takes less than half an hour and is considered fairly safe, allowing patients to recover quickly.
The ASR, by contrast, spent barely more than 5 years on the American market prior to recall during which over 90,000 ASR hip implants were sold. After hundreds of failure reports, warnings regarding metal debris and a growing number of lawsuits filed against DePuy and its parent company Johnson & Johnson, the ASR was finally recalled. The ASR gained FDA approval based on the 510(k) process in which it claimed to be substantially equivalent to the Pinnacle device. Revision surgery for the ASR is more difficult than that of the Pinnacle; the patient is opened up, the acetabular cup removed and replaced with a ceramic or plastic cup. Should the surrounding bone have grown into the cup, it will have to be ground out prior to replacement.
Another crucial distinction between the two hip implants lies in the external fixation design. The Pinnacle is fastened to the bone via screws however the ASR’s only means of fixation is to allow the femur to grown into the device. This design flaw is likely responsible for the great number of ASR cups which have loosened and failed. While both the Pinnacle and the ASR were designed to accommodate more active lifestyles of younger patient through greater range-of-motion and flexibility, the high failure rate has left these younger patients with no choice but to undergo revision surgery. In fact, a mere five years following implantation of the DePuy ASR hip systems at least 12 percent of recipients required revision surgery to correct problems with the device.
Those who have undergone hip implant surgery with either a DePuy Pinnacle or a recalled DePuy ASR should speak to their physician regarding their health.