What is the difference between the design of the DePuy ASR and DePuy Pinnacle hip implants?
DePuy ASR and DePuy Pinnacle are both prosthetic systems were designed and manufactured by DePuy Orthopaedics (which is a subsidiary of the pharmaceutical giant Johnson & Johnson) with younger, more active hip replacement candidates in mind because they were perceived as being more resilient and having greater longevity. The Pinnacle was the predecessor to the ASR and was intended to provide increased mobility and to reduce pain in those with damaged hip joints. Apart from the fact that DePuy has issued a worldwide recall of all ASR components, whereas Pinnacle systems are still notionally in circulation (albeit that DePuy discontinued their manufacture in 2013), the main design difference between the two implants is that the ASR cup is made up of one solid piece of metal while the Pinnacle cup comprises a liner. These liners are available in different types of materials, allowing for three different contact combinations of metal-on-metal, metal-on-polyethylene, or ceramic-on-polyethylene. The metal liner used in the Pinnacle is called the Ultamet.
While the Pinnacle system has not been formally recalled, as stated above, its manufacturing has been discontinued and it has been the subject of a very large number of personal injuries cases, in the US in particular, where these product defect claims have been consolidated in multidistrict litigation in the Northern District of Texas.
What are the implants’ similarities?
Both the Pinnacle and the ASR have suffered extremely high failure rates—at least 12 percent of recipients were required to undergo revision surgery within five years. While, as mentioned above, the ASR and the Pinnacle have differences in design, they both have many of the same problems, principal of which is a tendency for grinding of the metal components of the femoral head and the acetabular cup, which gives rise to the release of microscopic metallic debris into the surrounding tissue and blood stream resulting in swelling, pain and metallosis.
Metallosis occurs when the cobalt and chromium ions of these metals leach into the soft tissue, bones or bloodstream of the hip transplant recipient. While the long-term effects of metallosis are not yet clear (with some evidence tentatively showing that it can result in damage to the lymph nodes, spleen, liver, kidneys, heart and nervous system) the immediate effects have been observed to include necrosis of tissue and bone in the immediate vicinity of the implant site. If a malfunctioning device is left in situ for long enough the accumulation of fluids and the development of pseudotumours around the implant are other know complications, as is the loosening of the ball-and-socket components, which can result in dislocation of the hip implant. Bone fracturing near the implant site may also occur.
Are the revision surgeries the same for ASR and Pinnacle devices?
Pinnacle revision surgeries tend to be more straightforward than ASR revisions due to the fact that, assuming that metallosis in the vicinity of the implant is not too severe, the metal liner can simply be replaced with a polythene one. The ASR revision surgery, on the other hand, requires the complete replacement of the metal acetabular cup with a ceramic or plastic cup. If the surrounding bone has not grown into the cup, the revision procedure tends to be relatively uncomplicated. However, bony ingrowth will mean that the surgeon will need to grind the bone away from the cup in order to remove it, making the surgery more complex and potentially dangerous.
What symptoms are associated with Pinnacle failures?
Common complications experienced by Pinnacle hip replacement patients include:
- pain in the groin, hip or leg regions;
- swelling and inflammation; and
- limping.
Over the short term, the cobalt and chromium particles that are released can cause inflammation in the joint, resulting in pain and difficulty of movement. In the longer term, possible adverse side effects include cobalt poisoning, which could cause cognitive and cardiac damage.
What should I do if I suspect that I have been injured by a Pinnacle implant?
If you have been encountering difficulties with your hip which your GP or orthopaedic consultant believe may be down to the fact that you have received a Pinnacle implant you should seek advice from solicitors specialising in defective medical product liability without delay. This is because there are very onerous and strict limitation periods in place regarding the commencing of the appropriate compensation claims.
