subject: Heavy Metal Poisoning, A Potential For Defective Depuy Metal-on-metal Hip Implants [print this page] One of the many complications reported after DePuy Orthopaedics Inc. recalled its Articular Surface Replacement (ASR) hip systems was the hip implant metallosis. The several lawsuits that were filed against Johnson & Johnson, DePuys mother company, contained among its several allegations, metallosis. Several of these lawsuits have been consolidated into a multidistrict litigation under Judge David A. Katz of the U.S. District Court for the Northern District of Ohio who called for a status conference ofthe DePuy hip replacement lawsuit this month .
A patient could suffer from pain and potentially dangerous side effects if he has the hip implant metallosis which is the metal poisoning of cobalt and chromium in the soft tissue. The heavy metal build-up, particularly of chromium and cobalt, in the tissue is allegedly caused by the defective design of the metal-on-metal (MoM) ASR hip implants. Several orthopedic specialists said that they believed that the design of the ASR cup, which is shallower than some similar devices, was at the heart of the implants problems, according to an article published in the New York Times.
DePuy had intended a wider range of motion for patients by designing a shallower cup and removing the plastic liner from the inside of the implant. The friction of the ball portion of the hip implant against the socket instead wears away cobalt and chromium particles from the device and into the soft tissue around the area leading to metallosis.
The DePuy ASR hip implants use heavy metals cobalt and chromium because of their strength and anti-corrosion properties. The presence of these heavy metals at a low level in the body is considered safe, however, elevated levels could be toxic for patients as it could lead to both cobalt and chromium poisoning. In cobalt poisoning, experts consider any blood serum concentration at or above seven micrograms per millilitre to be dangerous.
Symptoms of cobalt poisoning are:
Cardiomyopathy
Neuropathy
Kidney failure
Thyroid problems
Gastrointestinal problems
Haemorrhages
Optic nerve / vision problems
Deafness
Experts at the Mayo Clinic Medical Laboratories believe that even low levels are concerning--"blood serum concentrations greater than 1ng/ML in a patient with Cr-based implant suggest significant prosthesis wear," although no concentrations have been established to be considered as dangerous levels for chromium poisoning.
Symptoms of chromium poisoning may include:
Acute renal failure
GI haemorrhage
Impaired liver function
Increased risk of cancers
The two complications could be diagnosed via a regular blood test. Affected patients would need to undergo a revision surgery to remove the defective implants which is causing the poisoning. In the face of the grave danger that the defective implants pose to a patients health, the ASR hip replacement recall seemed inadequate.
