cadera / hip - Active Congress.......

MARTES / TUESDAY
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only be used for the older patient of 65 years
or more. Some excellent long term results
have been obtained in patients who had some
other limiting factor from a young age that
prevented them attaining a high mileage each
year. We all know the problems of osteolysis
related to the polythene debris from a metal
on polythene joint. It is for these reasons
there is again a logical argument for using
a metal on metal articulation in the younger
and active patient.
The Outcome Centre at Oswestry has been
following 5000 patients now out to 9 years.
This is an independent review where information
is gathered directly from patients.
This has found a very high level of function
and activity in patients with metal on metal
resurfacing hip replacement. There is good
survival out to 9 years with 97% survival at a
minimum of 7 years. This group of patients is
from a combined series of several surgeons
across the world who are new to using this
technique.
Similarly, I have excellent results now out
to 10 years with the Metasul articulation on
a Thrust Plate. This is the shortest possible
uncemented stem with strong initial stability
and rigidity. These patients likewise have a
high level of activity and the 8 year follow up
was 98% survival.
What of the metal ions absorbed? Certainly
in a minority of patients these have a hypersensitivity
response which causes pain and
cyst formation. All patients absorb some
metal in the form of chromium and cobalt.
These levels are highest in the joint and
adjacent to the metal implants. Alterations
in circulating cells have been noted and this
causes concern. However, the observation
of a local sarcoma adjacent to a metal implant
is very rare indeed considering the numbers
implanted worldwide and this includes a
whole range of metal implants. The observation
therefore is that in practice and indeed
over many years it is unlikely that the risk of
a local cancer is signifi cant. Further observations
and studies are needed to identify and
quantify risks of leukaemia.
METAL-METAL BEARING
SURFACES: THE WAY
OF THE FUTURE?
S. J. MacDonald, MD, R. W. Mc-
Calden, MD, R. B. Bourne, M.D.,
C. H. Rorabeck, M.D., D. Chess, M.D.
Health Sciences Centre, Ontario, Canada
Objective: Polyethylene wear continues
to be the most signifi cant issue following
total hip arthroplasty (THA) leading to the
current increase in use of alternative bearing
surfaces. We performed a prospective,
randomized, blinded clinical trial comparing
metal versus polyethylene bearing surfaces
in patients receiving THA.
Method: Forty-one patients were randomized
to receive a metal (23) or a polyethylene
(18) insert with identical femoral and acetabular
components. Patients were evaluated
pre-operatively, at 3, 6, 12 months and annually
thereafter, including an evaluation of
erythrocyte and urine cobalt, chromium, and
titanium, outcome measures (WOMAC, SF-
12, Harris Hip Score) and radiographs.
Results: No patients were lost to follow-up.
At an average 7.2 (range 6.1 – 7.8) years
follow-up there were no differences in any
outcome measures or radiographic fi ndings.
Patients receiving metal liners had signifi -
cantly elevated metal ion measurements. At
most recent follow-up erythrocyte cobalt levels
were 7 times elevated (median 1.2 ∗g/L
(metal) vs 0.18 ∗g/L (poly), p