Characterization and computational modelling of acrylic bone cement polymerisation


Briscoe, Adam (2006) Characterization and computational modelling of acrylic bone cement polymerisation. University of Southampton, School of Engineering Sciences, Doctoral Thesis , 274pp.

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Description/Abstract

Total joint replacement is one of the most successful surgical procedures and is a
proven treatment for arthritis. Despite low failure rates, the wide application of the
treatment means that large numbers of prostheses fail and must be revised. Improved
pre-clinical testing methods for these orthopaedic devices may assist in developing
new prostheses with improved clinical results. Computational modelling of biological
systems is becoming increasingly accurate and is a much quicker and cheaper
alternative to physical testing, but continued development is necessary to ensure
computational models produce accurate and reliable predictions of implant behaviour.
Acrylic bone cements have been used as a method of fixation for over 50 years but
despite improvements in cement handling techniques and numerous attempts to
improve the mechanical properties of the cement in other ways, the cement is often
highlighted as the weak link in the joint replacement system. Aseptic loosening is
cited as the cause for the majority of revision operations and cement degradation has
been shown to be a contributor to the loosening process. In-vivo, cement is subject to
cyclic loads and these are the primary cause of cement damage. Residual stresses
generated during the polymerisation of the cement are now thought to play a
significant role in cement failure.
This thesis examines the development of residual stresses as a result of thermal and
chemical changes during polymerisation of the cement. Experimental techniques for
characterising the evolution of materials properties during the polymerisation reaction
are discussed. Differential scanning calorimetry was used to measure the reaction
variables such as the activation energy of polymerisation. The development of an
ultrasonic rheometry technique for monitoring the mechanical property evolution
within a bone cement specimen is discussed. Computational models were generated to
predict the reaction behaviour of the cement in terms of the heat produced and the
evolution of the physical properties of the curing mass. Some advantages and
disadvantages of candidate mathematical models have been evaluated and are
discussed, along with applications in several implant fixation scenarios.. The model
compared well with experimental data and was used to predict thermal necrosis in the
bone surrounding both a hip resurfacing implant and a knee replacement. Using the
output reaction path produced by the thermal model a mechanical model was also
produced simulating the shrinkage and mechanical property evolution exhibited by
the polymerising cement. Two material models were compared with and without the
effects of plasticity. Residual stress magnitudes were assessed in comparison with
published values and showed better agreement when plasticity was included. Peak
stresses were observed to occur during polymerisation. The location of the peak
stresses were compared with experimental data on pre-load crack locations in the
literature and showed good agreement.

Item Type: Thesis (Doctoral)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
R Medicine > RC Internal medicine
Q Science > QP Physiology
Divisions: University Structure - Pre August 2011 > School of Engineering Sciences > Engineering Materials & Surface Engineering
ePrint ID: 64795
Date Deposited: 16 Jan 2009
Last Modified: 27 Mar 2014 18:46
URI: http://eprints.soton.ac.uk/id/eprint/64795

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