Compressive mechanical properties and cytocompatibility of bone-compliant, linoleic acid-modified bone cement in a bovine model

Abstract

PostprintThis is the accepted version of a paper published in Journal of The Mechanical Behavior of Biomedical Materials. This paper has been peer-reviewed but does not include the final publisher proofcorrections or journal pagination. Citation for the original published paper (version of record):López, A., Mestres, G., Karlsson Ott, M., Engqvist, H., Ferguson, S. et al. (2014) Compressive mechanical properties and cytocompatibility of bone-compliant, linoleic acidmodified bone cement in a bovine model. Journal of The Mechanical AbstractAdjacent vertebral fractures are a common complication experienced by osteoporosis patients shortly after vertebroplasty. Whether these fractures are due to the bone cement properties, the cement filling characteristics or to the natural course of the disease is still unclear. However, some data suggests that such fractures might occur because of an imbalance in the load distribution due to a mismatch between the elastic modulus (E) of the bonecement composite, and that of the vertebral cancellous bone. In this study, the properties of bone-compliant linoleic acid-modified bone cements were assessed using a bovine vertebroplasty model. Two groups of specimens (cementonly and bone-cement composites), and four subgroups comprising bone cements with elastic moduli in the range of 870-3500 MPa were tested to failure in uniaxial compression. In addition, monomer release as well as time and concentration-dependent cytocompatibility was assessed through the cement extracts using a Saos-2 cell model.Composites augmented with bone-compliant cements exhibited a reduction in E despite of their relatively high bone volume fraction (BVF). Moreover, a significant positive correlation between the BVF and E for the composites augmented with 870 MPa modulus cements was found. This was attributed to the increased relative contribution of the bone to the mechanical properties of the composites with a decrease in E of the bone cement. The use of linoleic acid reduced monomer conversion resulting in six times more monomer released after 24 hours. However, the cytocompatibility of the bone-compliant cements was comparable to that of the unmodified cements after the extracts were diluted four times. This study represents an important step towards introducing viable bone-compliant bone cements into vertebroplasty practice.

Mechanical Properties and Cytocompatibility Improvement of Vertebroplasty PMMA Bone Cements by Incorporating Mineralized Collagen

“…For example, N -methyl-pyrrolidone monomer and linoleic acid were, respectively, used to partially replace the MMA monomer in the polymerization of the PMMA bone cement. However, with the down-regulation of the compressive modulus, the compressive strength also decreased to be much lower than the requirement of ISO 5833-2002 [28,29]. …”

In Vitro and In Vivo Response to Low-Modulus PMMA-Based Bone Cement

“…We have previously shown that fatty acids and triglyceride oils are able to substantially improve the mechanical properties of acrylic bone cements in terms of lowering their elastic modulus [ 17 ]. However, the effect of their addition on surrounding cells and tissues has not yet been investigated.…”

“…The results showed that whereas undiluted extracts of OP were harmless, undiluted extracts prepared with additive-containing cement reduced the number of cells alive ( Figure 1(a) ). This could be associated with either the LA or CO itself or with a delayed reaction of PMMA cement in presence of these additives, causing a higher release of monomer into the extract, as discussed elsewhere [ 17 ]. The reduction in cells observed was similar regardless which additive, LA or CO, was added to the cement, even though the amount added (1.5 and 12.3 wt%, resp.)…”

“…1.5 wt% 9-cis,12-cis-linoleic acid (LA, ≥99%, Sigma-Aldrich, reference number W338001) was used, corresponding to 226 μ L LA for 10.0 g of powder and 3620 μ L liquid. These formulations were found to be advantageous to the in vitro biocompatibility in preliminary studies [ 17 , 18 ]. Each batch of bone cement was prepared by adding the modified monomer phase to the (unaltered) powder phase in a glass mortar and mixing it by hand with a metal spatula for 1 minute.…”

“…The authors have also showed that, using only small amounts (≤1.5 wt%) of linoleic acid, it was possible to decrease the compressive strength and Young's modulus of a commercial bone cement by 76% and 83%, respectively, with initial cytotoxicity tests showing promising results. While promising mechanical data is available for these modified cements, their in vitro and in vivo biocompatibility remain to be confirmed [ 17 ]. In fact, to the authors knowledge, no in vivo study is currently available for any low-modulus acrylic cement.…”