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MARTES / TUESDAY
68
THE INCIDENCE AND
VOLUME OF OSTEOLYSIS
AT A MINIMUM 5-
YEAR FOLLOW-UP WITH
HIGHLY CROSSLINKED
AND NON CROSSLINKED
POLYETHYLENE
C. A. Engh, MD
Anderson Orthopaedic Research
Institute, Alexandria, USA
Introduction:
In both laboratory and clinical studies, crosslinked
polyethylene has shown decreased
wear rates, but the effect on osteolysis still
needs to be examined. This study sought to
determine if the incidence and volume of osteolysis
decreased with use of a crosslinked
polyethylene. CT was used in this study
since it more accurately measures volume
than radiographs and can detect small lesions,
making it useful for the early detection
of osteolysis.
Materials and methods:
230 hips were randomized to a Marathon
crosslinked (Depuy) or Enduron non crosslinked
(Depuy) 4-mm lateralized polyethylene
between 1999 and 2000 in an IRB-approved
prospective study separate from this study.
76 study hips received a computed tomography
(CT) scan as part of routine clinical
follow-up. CT scans were analyzed using a
validated post-processing software package
(Muscular-Skeleton Analysis Software) that
allowed a blinded observer to defi ne osteolysis
and determine osteolysis volume.
Results:
The average length of follow-up was 6.1 ± 0.4
years. 40 hips had a Marathon polyethylene
and 36 had an Enduron polyethylene. There
were 12 (30.0%) Enduron and 6 (16.7%)
Marathon cases with at least one osteolytic
lesion. There was no signifi cant difference (p
= 0.19) in the incidence of osteolysis between
the two groups. The average lesion volume
for Enduron cases was 7.0 ± 6.7 cm 3 , which
was signifi cantly larger (p = 0.001) than the
average lesion volume for Marathon cases
of 1.2 ± 0.7 cm 3 .
Discussion:
At this short follow-up interval, Marathon
crosslinked polyethylene has shown to have
a decreased volume of osteolysis over Enduron
non crosslinked polyethylene. Longer
follow-up is necessary to determine if Marathon
crosslinked polyethylene will continue to
demonstrate the encouraging improved wear
and osteolysis characteristics found in both
the literature and the current study.
METAL-METAL COUPLE –
SCIENTIFIC BASES
E. Robinson, T. Singh Aulakh, M. Khan,
J. Herman Kuiper, J. Richardson
The Robert Jones & Agnes Hunt
Orthopaedic Hospital, UK
Science is based on observation. Any hypothesis
should then fi t those observations
and be open to testing. Metal on metal hip
replacement was very successful with a
design by Ring some 30 years ago. There
were diffi culties however with initial fi xation to
bone. John Charnley solved that problem by
the development of bone cement. His second
solution was a metal on polythene articulating
surface which had demonstrable lower friction
and would never squeak. Even at that time
there was much debate on what was best and
John Charnley used the threat and concern
of cancer to help swing opinion towards his
own design of hip replacement.
The metal on polythene hip has stood the test
of time but John Charnley himself insisted it