Periprosthetic fractures around polished collarless cemented stems: the effect of stem design on fracture pattern
Johannes Erhardt, Paul P Khoo, Karl K Stoffel & Piers J Yates
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abstract
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<sec
id="st1"><title>B<sc>ACKGROUND</sc>&l
t;/title>
Predictable patterns of periprosthetic fracture have been observed
around polished double tapered stems. Finite element studies have
suggested that triple-tapered stems cause less cement strain in
torsion compared to double-tapered stems. Hence, we hypothesised
that the in vitro behaviour of implanted double- and triple-tapered
polished stems, like the CPT (Zimmer, Warsaw, USA) or C-Stem (DePuy,
Leeds, UK) when subjected to pathological torsional loads may cause
different patterns of periprosthetic fractures. </sec><sec
id="st2"><title>M<sc>ETHODS</sc></
title>
Ten double-tapered stems (CPT) and ten triple-tapered stems (C-Stem)
were cemented into synthetic femur bones. A constant axial
compression load of 100 N and a torsional pre-load of 0.1 N.m were
applied using a biaxial testing machine. The distal femur was then
loaded in external rotation at 45 degrees until failure.
</sec><sec
id="st3"><title>R<sc>ESULTS</sc></
title>
Seven of the 10 CPT stems fractured at the level of the stem body
while fracturing the cement mantle at the same level. In three of
ten of the CPT stems and all ten C-Stems, the synthetic bone
fractured at the tip of the prosthesis while the cement mantle
remained intact. This was significant for the resulting fracture
pattern (P=0.001). There was no significant difference between the
groups for either torque (P=0.13) or angle at failure (P=0.49).
</sec><sec
id="st4"><title>I<sc>NTERPRETATION</sc&g
t;</title>
This biomechanical study indicates that the CPT and C-Stem create a
different fracture pattern under the same loading condition. The
C-Stem (a triple tapered stem) may produce lower strain in torsion
to the cement mantle of a cemented THA. However, fractures that do
occur may be more difficult to treat than those produced around a
stem like the CPT subjected to comparable loading. </sec>
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citation
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erhardt j, Khoo P P, Stoffel K K, Yates P J. Periprosthetic
fractures around polished collarless cemented stems: the effect of
stem design on fracture pattern. Hip Int 2013; 23:459-64.
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type
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journal paper/review (English)
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date of publishing
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10-5-2013
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journal title
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Hip Int (23/5)
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ISSN electronic
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1724-6067
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pages
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459-64
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PubMed
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23813164
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DOI
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10.5301/hipint.5000052
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