What's wrong with DePuy Orthopaedic's ASR Hip?

On August 24, 2010 DePuy recalled the ASRTM XL Acetabular System (hip implant) and ASRTM Hip Resurfacing System. If you have had hip replacement surgery between July 2003 and August 2010, you might be affected by this recall. If you are unsure about which artificial hip you have, contact your doctor for more information. Your medical records should contain operative information and surgical stickers that identify the hip that you received.

Studies and testing have revealed several likely flaws of ASRTM hip systems. An artificial hip, like a real hip, is a ball and socket joint. The socket of the joint generally is a cup that is fitted into the hip itself. In most modern hips this cup is then lined with another material, usually a plastic called polyethylene. The ball of the joint is an artificial head that is attached to the femur. The ball is placed in the cup where it can rotate relatively freely. The ASRTM is unlike the typical hips discussed above in several ways:

Mono-block Cup

First the ASRTM features a mono-block cup. It is a single piece cup without a separate liner. This simplified design was thought to result in less wear than the multi-piece cups because there is no risk of movement between the liner and the cup.

Shallow Cup

The cup of the ASRTM is shallower than the typical design. A shallow cup means that a smaller portion of the femoral ball is encompassed by the cup. The shallow cup of the ASRTM was designed to give patients a greater range of motion because the leg of the patient can rotate farther before hitting the sides of the cup. However this design also appears to cause excess wear. This means a shorter life-time for the replacement hip. The excess wear can also lead to serious conditions such as metallosis, which is the build up of metallic debris in the soft tissues of the body.

Metal-on-Metal Design

Another distinctive feature of the ASRTM is that it uses a metal-on-metal design. Both the mono-block cup and the femoral head (the ball) are made of chromium and cobalt. As a result of excess wear there can be an accumulation of metal in the body. The metal deposits around the implant itself may result in tissue damage. In addition, some people may have an increased sensitivity to metal that can result in increased pain and other symptoms. In large enough quantities the metal can be toxic and result in a variety of ailments including: blindness, trouble thinking, deafness, headaches, and others.

I think I have an ASRTM hip, now what?

If you think you have an ASRTM hip implant the first thing you should do is contact your doctor. Your doctor will have more information and should be able to confirm which implant you received. If you have an ASRTM hip implant, it is likely that your doctor will discuss with you the need for blood tests to measure the levels of chromium and cobalt in your bloodstream. The blood tests will determine if there is excess metal in your bloodstream which is an indicator of excessive wear of the ASRTM hip system. Your doctor may also discuss the need for revision surgery in order to replace the defective hip.

Your doctor may give you forms from DePuy or from Broadspire (the company working with DePuy to handle claims) requesting authorization to access your medical records and your explanted (removed) hip. These forms will say that DePuy is requesting this information so that it can process claims in order to compensate patients. However, these forms are vague and do not explicitly promise payment nor do they promise compensation for missed work or other expenses. It is important that you consult with an attorney before signing any of these documents. DePuy can use this information to deny your claim and impair your ability to collect money from DePuy.

Categories: Hip Implants