Thursday, May 10, 2012

A Study of Metal-On-Metal Hip Replacement Implants: Part Two: Cobalt Poisoning Examined

What are the Symptoms of Cobalt Poisoning?

Cobalt poisoning as a result of industrial exposure or medical treatment is fairly well known, however those who were fitted with a metal-on-metal hip implant were not expecting to be subjected to dangerous levels of cobalt. Cobalt poisoning can lead to ringing in the ears, dizziness, deafness, blindness or atrophy of the optic nerve, severe headaches, declining cognitive abilities, heart failure, limb weakness, cardiomyopathy, hypothyroidism and convulsions.

When the heart enlarges, becomes “floppy,” and has problems properly pumping blood cardiomyopathy occurs. The blood in the body can also thicken due to excessive exposure to cobalt. Those patients who have undergone a metal-on-metal hip replacement surgery, then experienced severe negative health effects as a result can have a lower chance of success when undergoing a revision surgery. Excessive amounts of cobalt in the bloodstream can in turn lead to extreme metal sensitivity which not only damages the surrounding tissue, but dictates that a second implant will be much less likely to have positive results.

Case One

A case report written by Steven S. Tower, MD, details two specific cases of toxic cobalt exposure in two men, both 49 years old, both in good physical condition, and both having undergone metal-on-metal hip replacement surgery using an ASR DePuy hip implant. In the first case the hip replacement surgery was indicated as a treatment for osteoarthritis. While this patient initially showed improvement in the few months following the surgery, he soon began experiencing hip pain during any type of physical activity. Three months following the surgery, the patient began developing rashes, although at that time skin tests to determine whether there were excessive levels of cobalt or chromium present were negative.

Nearly a year after the surgery, progressing levels of hip pain sent the patient back for more testing which showed large pockets of fluid collecting in region of the hip implant. Cobalt levels were re-tested and found to be at the extreme level of 50 µgl. Eighteen months found the patient suffering from severe headaches, exhaustion, ringing in the ears, loss of hearing as well as suffering from emotional issues such as extreme anxiety and irritability. At this point, however, the cobalt levels had reduced somewhat to 35µgl. By three years post-implant, the patient was suffering hip pain even while stationary, and added symptoms such as trouble with coordination, decline in cognitive abilities, visual changes, creaking in the hip joint and hand tremors.

At this point the patient’s serum cobalt levels had skyrocketed to 122µgl. Three and a half years after the original hip implant the patient underwent revision surgery. At this time the serum cobalt levels in the joint fluid was measured at 3200 µgl. The hip implant which was removed showed excessive wear, indicated by multiple “burnished” areas. A year following the revision surgery the patient was experiencing much less hip pain and noted his hearing, cognitive abilities and tolerance to exercise had all improved while the tremors were also lessening. The ringing in the ears and visual problems had not gone away, however they were not increasing in severity.

Case Two

The second case involved a patient who underwent revision surgery for a failed resurfacing attempt on the femoral head. A year following this revision surgery, the patient was experiencing pain in the groin area, decline in cognitive abilities, loss of hearing and external rashes. The patient’s serum cobalt levels at this time were 23 µgl. After the initial revision surgery, this patient then underwent a second revision surgery three and a half years after the first. When this second revision surgery was performed, the serum cobalt level in the joint fluids was measured at 3300 µgl and extreme metallosis was noted. In this instance hip implant which was removed showed scratching and scuffs and scars from wear. Seven months following the second revision surgery this particular patient reported an improvement in the negative symptoms.

Results of the Study

Both patients experienced significant relief from pain following their revision surgeries and both patients showed excessive wear on the removed hip implant devices. In patient one the excessive wear was almost a hundred times that of “typical” metal-on-metal hip implants. Upon examination of the removed hip implant in patient two, it was determined the implant suffered from inadequate bearing clearance. While a serum cobalt level of approximately 20 µgl is not uncommon in recipients of metal-on-metal hip implants, when testing was performed on 214 patients, ten had serum levels of cobalt higher than 20µgl while one had levels above 110µgl. The study noted that even well-positioned metal-on-metal hip implants can lead to higher than normal serum cobalt levels, potentially impairing renal functions. From October, 2005 through December, 2006 approximately one third of the hip replacement surgeries performed in the United States involved the use of a metal-on-metal device. In cases where the metal-on-metal hip implant bearings wear excessively patients are at a much higher risk of cobalt poisoning.

The majority of those patients who have had a metal-on-metal hip implant will have higher levels of serum cobalt than even industrial workers, putting them at a higher risk of both cognitive and cardiac issues. Those patients with metal-on-metal hip replacement implants who appear to be at the highest risk of cobalt poison are those who are experiencing progressively more pain in their hip area or those with renal impairment, or those who received an ASR hip implant. Revision surgery is recommended for patients whose serum cobalt levels are higher than expected or those who are experiencing any of the negative symptoms associated with toxic levels of cobalt.

Are Doctors Aware of the Risk?

The initial symptoms of cobalt toxicity can often go unnoticed or will be attributed to other issues with hip implant failure. Patients may experience declining cognitive abilities, depression or other mood disorders or dizziness, and if they are also experiencing significant levels of pain due to the hip implant both the doctor and the patient may assume the pain and other symptoms will disappear if revision surgery is performed. Even doctors who are recommending revision surgery to alleviate the pain may be unaware that the friction in the metal-on-metal hip implant could be releasing high levels of metal ions into the bloodstream which will render much more serious and potentially long-term health issues than the hip pain. Both patients and their doctors may be unaware that the patient could walk out of surgery with the start of heavy metal poisoning which could destroy their health and compromise their future.

Author: Sullo & Sullo Attorneys

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