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14/04/2006
BLOOD LEVELS OF METALS EQUALLY HIGH IN SURFACE REPLACEMENT
AND TOTAL HIP REPLACEMENT PATIENTS
The modern surface hip replacement devices are always of the
type metal-on-metal type. Their bearing surfaces are
considerably greater (diameter 52 – 56 mm) then the bearing
surfaces of the “conventional” metal-on-metal total hip
joints (diameter 28- 32 mm).
There has been concern that the large surface area of
surface replacement devices produce larger numbers of
metallic wear particles than total hip joints. On the other
hand, some experiments in laboratory indicated that the
friction of large surface replacement devices is lower and
that these devices produce less wear particles than the
total hip joints.
The known British hip surgeon doctor McMinn, who now has his
own institute (The McMinns Centre, Birmingham, England, UK)
studied this important question (Daniel and McMinn 2006).
They followed the blood levels and urine excretion levels of
chrome and cobalt in two groups of patients: one group of
patients had the Birmingham surface replacement device; the
other group had a total hip replacement device. The patients
were followed up for two years. There was no “normal” or
“control” group.
Measurement two years after surgery showed that the blood
levels and urine excretion levels were similar in both
studied groups.
The authors studied also another groups of patients who had
another types of surface replacement and total hip
replacement devices for five years. Neither in these two
latter groups was there any difference in blood and urine
levels of cobalt and chrome between the two studied groups
five years after the surgery.
Information for you: According to this study, the blood
levels of cobalt and chrome are practically equally high in
patients with total hip replacement as in patients with
surface hip replacement.
Because there were no normal individuals in this study you
would not know, however, how much higher than normal these
values are. This might be important. The recently published
study by Hart (see the previous NEWS, April 2006)
demonstrated that patients with high blood levels of chrome
and cobalt have impairment in their body defense system.
If you believe that there is a risk to live with high blood
levels of chrome and cobalt, you would be at equally high
risk either you will have a surface replacement or a total
hip replacement device. You will, however, not find
information how high the risk might be in the present study.
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References:
J. Daniel, W. McMinn: The effect of the diameter of
metal-on-metal bearings on systemic exposure to cobalt and
chromium. Journal of Bone and Joint Surgery - British
Volume, 2006; Vol 88-B: 443-448.
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