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Insert
stability
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Just
like Leclercq 14,
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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Tradonski 23
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
Esop® fitted : no movement has been
noted.
An explant survey confirmed
the excellent stability.
More
information
WARNING : Except in
North America, Esop®-cup
is distributed under the mark ATLAS®
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Welcome
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