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

improvements were seen in both groups with respect to pain at night and at rest,
physical functioning, quality of life, and perceived improvement”. The study of Kallmes
et al. [3] found similar results and showed that improved disability and pain scores were
noted immediately following both procedures, however a trend toward a higher rate of
clinically meaningful improvement in pain (30% decrease from the baseline) in the
vertebroplasty group was observable. These results have been met with some disbelief
among physicians treating VCF patients, and severe concerns were raised on the design
of both studies (ethical concerns, small sample size, crossover between the groups, i.e.
patients were able to guess they have been treated with the sham procedure, and the
sham procedure could itself have promoted pain relief). Conflicting with these results, a
more recent study [4] has been released showing the efficacy and value of
vertebroplasty.
Regardless of their final conclusion whether vertebroplasty is effective or not, none of
these studies investigated quantitatively the interdependence and sensitivity of the
treatment parameters on the resultant outcome. In preliminary analyses, we found and
concluded that a small deviation of the cannula position from the ideal location might
significantly impair the mechanical stabilization effect and thus the efficacy of the
procedure. Furthermore, until now, no evidence has been provided as to which extent
cement type, cement volume, cannula placement and other treatment parameters affect
the aforementioned loading pattern in the spine and the final outcome of the treatment.
Such indications could be helpful to complement the findings of the recent studies by
replacing the qualitative (effective yes/no) by absolute or relative quantitative measures
that might even incorporate the patient’s condition before the treatment.
The aim of this study was therefore threefold:
• Firstly, to investigate and introduce methods that allow to pre-compute realistic
cement distributions and perform a local bone strength assessment prior to and
after the vertebroplasty treatment.
• Secondly, to identify those treatment parameters and the implied cement
spreading pattern with the optimal trade-off between the mechanical
stabilization effect and the possible (negative) treatment side effects.
• Thirdly, to assess the efficacy of vertebroplasty by quantitative measures.
3. METHODS
3.1 Bone sample, scanning and morphology determination
A cadaveric human vertebral body (L1 level) was scanned using a high resolution
computed tomography scanner (µCT 40, Scanco Medical AG, Bassersdorf,
Switzerland) at the Department of Biomedical Engineering of the Eindhoven University
of Technology. The scan, performed in air, was taken at a nominal isotropic resolution
of 37 µm and segmented using a global threshold. Bone architecture parameters were
derived using a bone micro-architecture database lookup algorithm.
3.2 Constitutive material properties
The constitutive mechanical properties of each element in the Finite Element (FE)
model were computed using a combined lookup table mapping combined with an
extended rule of mixture that accounts for the bone volume fraction (BVTV), the