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Several news sources, among them the New York Times, have already commented on the mounting data that more women than men are reporting problems with the ASR XL Acetabular System. We'd like to explain exactly why that is.
Problem: Hip Implant Not Designed Ideally for Wider Hip Sockets
Women, as you may have heard, are structured differently anatomically than men. The differences aren't merely on the surface, however; they extend into the skeletal structure and particularly in the pelvis region. Women have wider hips with bigger hip sockets to accommodate the process of giving birth, which means they often have more problems in hip implant surgery because those large hip sockets allow the implant to dislocate more easily.
In the DePuy ASR XL Acetabular System, however, the problems go beyond the norm. One of the reasons is that the hip implant was designed to be extremely shallow, exacerbating the problems women already have with hip implants.
Problem: Women More Likely to Require Hip Implants
Women are more prone to osteopenia, osteoporosis, and often have weaker bones overall than men, particularly as they age. The onset of menopause, and the subsequent drop in estrogen, have been linked to rapid bone deterioration. Because of all of these factors, women are more likely than men overall to require a hip implant because of a hip fracture.
Problem: Small, Shallow Hip Implant
The DePuy ASR XL Acetabular System was designed to give patients a greater range of motion. If you'll recall, the design of the hip implant included two parts: an implant inserted into the femur bone with a rounded top that fit into a cup placed in the hip bone.
In the design of the ASR XL Acetabular System, the cup was made very shallow, which meant that the patient could move their leg in a wider arc before the other part of the implant might dislocate.
Good in theory. And if DePuy had tested their product properly, it might have worked quite well. In real life, it went a little differently.
The shallow hip implants meant that all of the friction caused by everyday movement was focused on a much smaller area. There was more force on a smaller amount of material. The hip implant was under more stress and was more prone to the friction that caused small metal ions to break off into the bloodstream. It was also more likely to break altogether.
Especially in women. Their smaller, shallower hip implants meant there was even more strain on the material. Women who have an ASR XL Acetabular System are reporting problems in greater numbers than men in part because their hip implants are simply breaking down faster. They have the same problems, forced upon a smaller area.
Our consulting doctor offered some sobering statistics for smaller hip implants in general: the risk of a hip revision surgery for a hip implant with a head size of 44 mm is five times that of a hip implant with a head size of 55 mm.
Problem: Bone Deterioration Exacerbated in Women's Hip Implants
Because women are more prone to bone deterioration in general and have less bone density than men, the problems caused by the ASR XL Acetabular System are multiplied. We've explained the problem of bone deterioration at length, but here's the issue in a nutshell:
For a non-cemented hip implant like the ASR XL Acetabular System to work properly, the surrounding hip bone needs to be healthy and growing. DePuy's hip implant design caused an inordinate number of metal ions to be released into the bloodstream, causing problems with metallosis, heavy metal poisoning, and metal sensitivity - all of which adversely affect the bone.
One reason why women may be reporting problems with their hip implants sooner than men is because they have less bone to sacrifice to the effects of the metal ions floating in their bloodstream. The symptoms become painful more quickly, and more women are going to their doctor with concerns about the hip implant.
Handicapped with less dense, weaker bones, women now face the additional problem of attempting a hip revision with severely damaged hip bones from the previous DePuy hip implant.
It is already more difficult for a woman to have a successful hip replacement surgery than a man. DePuy's ASR XL Acetabular System made it even more difficult - not to say dangerous.
Recommended Readings:
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
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