Bone deterioration is associated with disease; soon, it may also be linked to the DePuy ASR XL Acetabular System. And for good reason.
Friday, March 23, 2012
|Why Bone Deterioration Causes Problems with Hip Revision Surgery
As we try to describe the reasons the DePuy ASR XL Acetabular System present such a danger to your health, we occasionally use terms you may be only vaguely familiar with. This is an ongoing series of articles on the medical terms related to the DePuy hip recall and hip revision surgeries.
When undergoing hip surgery, there are generally two options for a hip implant: cemented and uncemented. Cemented implants, which involve attaching the implant directly to the surrounding bone by means of a specially constructed bone cement, have been used since the 1960s. Uncemented implants were introduced in the 1980s. The ASR XL Acetabular System is an uncemented implant.
The idea behind an uncemented implant is that healthy bone can grow into its surface, thus holding the implant in place by means of the body's own materials instead of a foreign cement. Medical professionals hoped that this design would mean the patient could have a more active life since the concern of gradually wearing away the cement would be eliminated. Cementless total hip replacements are recommended for younger, more active patients and have shown, so far, better results in long-term studies.
Obviously, healthy bone is essential for an uncemented hip implant. Without healthy bone growth, the hip implant will not be secured into the rest of the skeleton and will not function as a replacement for the removed hip.
Evidence is showing that the DePuy ASR XL Acetabular System may cause serious bone deterioration in a number of ways. One of the most significant is osteolysis, which occurs when the body reabsorbs bone as part of an autoimmune response. Osteolysis has been noted as a side effect of many total hip replacement systems; the more debris that is released into the body, the more common osteolysis becomes. Metal-on-metal hip implants were thought to have less likelihood of debris because they are made of harder materials, but the ASR XL Acetabular System's poor design caused significant friction and a great deal of metal debris, raising the risk of osteolysis.
Another problem is the surgery itself. An uncemented implant requires the surgeon to insert the cup of the hip implant into the hip socket, called the acetabulum. This means some of the bone in the socket must be scraped away to make room for the implant. This is part of any hip implant surgery, but since the DePuy implants only lasted a few years before they were recalled, patients are now forced to undergo hip revision surgery before that bone has had enough time to recover from the initial surgery's trauma.
Hip revision surgery is much less likely than initial hip replacement surgery to succeed. With damaged bone mass, the chance of success is even lower.
In essence, the weaker the bone, the less likely it is that each successive hip replacement surgery will succed. With complications of metal poisoning, metallosis, and trauma to the surrounding bone and tissue, the circumstances for a revision surgery are far from optimal.
Hip Implant Risks May Include Premature Failure
How the ASR XL Acetabular System is Constructed
DePuy Asks Hip Implant Patients to Sign Away Their Legal Rights