ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

Fig. 2: The relative overall organ strength improvement OSI as a function of the
injected cement volume (left figure) and the cement type (right figure). A larger
injection volume has a strong positive effect whereas the variation of the cement
stiffness has only a marginal positive effect on the overall strength.
5. DISCUSSION AND CONCLUSIONS
The aim of this study was to combine computational simulation techniques to model the
mechanical effect of vertebroplasty and to assess the efficacy of the procedure using
quantitative measures. The results presented support our hypothesis, that the efficacy is
strongly related to the location of the injection site within the vertebral body. This
statement is supported by the SAI-distributions in Figure 1. For treatment position 2,
only 3 mL of cement injection is required to achieve approximately the same strength
improvement that follows the treatment at position 1 with 6 mL cement. An important
aspect is that the OSI-indicator, for some of the injection locations, indicates a negative
procedure outcome, which should be avoided. The results in Figure 2 suggest that the
injected volume should be as large as possible. This finding might be true from a
mechanical point of view. However, a larger injection volume is also associated with a
higher treatment risk (cement leakage, embolism etc.) and consequently shouldn’t be
the optimization path to follow.
Our findings fit within the conclusions drawn from the randomized controlled trials that
support or question the efficacy of vertebroplasty. Critics would say that an
improvement by vertebroplasty can only achieved by chance whereas the optimist
argues that the uncertainty can be eliminated by optimization techniques. The
computational model presented in this study is a first attempt to solve this optimization
problem by considering the patient’s condition prior the treatment and sampling the
(highly dimensional) solution space at uniformly distributed points. Besides the optimal
treatment parameters, the presented measures allow to quantitatively judge the efficacy
of the vertebroplasty according to the patient’s condition individually.
At the moment, this model is limited to one spine level, and there is no evidence on the
accuracy of the overall computational model. While there is an ongoing effort to
experimentally validate the model and improve its accuracy, an extension towards a
multi-level or full-body diagnosis tool can be achieved by incorporating it into a
musculoskeletal simulation system.