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Insert stability
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Just like Leclercq14, Beaver5 and O'Brien19 we have noted polyethylene core movements in
relationship to the metal back cup, with some prosthesis
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Insert tipping
example
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Tradonski23 conducted a comparative study of the forces
required to separate the core from the cup, using 8
different acetabulum prostheses. He measured the forces used
to tear away and tip the core.
Core
rotation on its axis without tipping, that has sometimes
been mentioned, has never been described. Core tipping was
the usual dissociation mechanism. It occurred after extreme
movement.
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During such movements, the forces are no longer
applied to the centre of the core, but to its surrounding
section, hence the tipping. Collier 8 confirmed that analysis : he also showed that
complex fastening systems, blocks and catch rings were
likely to deteriorate due to stress concentration.
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Core tipping results from forces concentration around the
core during position changes (when changing from a sitting
to a standing position)
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That is why the polyethylene core holding
system of the cup should be simple and massive. The insert
should not be fully hemispherical, but should have a
cylindrical section around it, preventing
tipping.
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In order to prevent
tipping, the core should be cylindrical in its surrounding
section
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Since 1987, over 80
000 ATLAS®
fitted : no movement has been noted.
An explant survey
confirmed the excellent stability.
More
information
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Welcome - The
various Atlas -
Primary
stability -
Insert
stability -
Insert
thickness -
Secondary
stability -
Alumina/Alumina - Explant
analysis
Low-friction - Surgical
procedure -
Clinical
data - Quality
requirement -
The
inventor -
Contact - International
distribution
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