Dr. Su’s Protocol for Metal Ion Testing
Metal Ion Testing The testing of metal ion levels after hip resurfacing is controversial,
to say the least. Because we are still learning about the metals used in
resurfacing, how they are released (and in what quantity), and how the body
reacts to these metals, there are no definitive guidelines for metal ion levels
in every patient.
There has been research done regarding the amount of metal ions that
expect to be produced and remain in the body after hip resurfacing.
what we don’t know is: "At what level do these metals pose a problem?"
seems that different patients will have different tolerances for the
metal in their body – some react to the metals at a very low
while others have no symptoms, even if their metal ion levels are high.
This is what makes it difficult, if not impossible, to produce
guidelines for metal ion testing.
Many surgeons believe that metal ion
only lead to more questions and concerns, since we don’t know exactly
what to do
with this information. There is no cutoff value for metal ion levels;
there is no level that would make a revision necessary, at this point.
British Orthopaedic Association has made recommendations that cobalt and
chromium levels be below 7 parts per billion, per hip; however, there
patients who have levels above this threshold who do not have problems.
United States FDA has not made specific recommendations regarding metal
testing; in their Safety Communication dated January 17, 2013, they
FDA does not believe there is a clear need to routinely check metal ion
in the blood if the orthopaedic surgeon feels the hip is functioning
and the patient is asymptomatic.; and "At this time, the FDA is not
recommending a specific metal ion level as a trigger for revision or
I believe that metal ion testing gives information about what is
happening in the joint with regard to wear. With conventional
bearings, we can measure wear on an x-ray; with metal-on-metal, this is
possible, since the ball and socket are the same material. Therefore, I
find the use of metal ion testing to be informative as to what is
inside the joint. Perhaps if I identify metal ion levels elevated above a
I Believe to be normal, I can help guide a patient into modifying
activity to reduce the amount of wear. In addition, I believe it
provides a check
to make sure that a patient’s kidneys are functioning properly to filter
body of excess metals.
My current protocol is to test the metal levels yearly, in all
patients. Once I have gathered enough information that a joint is
functioning well, then
Decrease the frequency to every 2 years.