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Compressive mechanical properties and cytocompatibility of bone-compliant, linoleic acid-modified bone cement in a bovine model
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)ORCID iD: 0000-0001-7462-4236
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine)
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2014 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 32, 245-256 p.Article in journal (Refereed) Published
Abstract [en]

Adjacent 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 bone-cement 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 (cement-only 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 their relatively high bone volume fraction (BVF). Moreover, a significant positive correlation between the BVF and the 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 h. 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.

Place, publisher, year, edition, pages
2014. Vol. 32, 245-256 p.
Keyword [en]
adjacent vertebral fracture(s), low-modulus bone cement(s), vertebroplasty, linoleic acid, bone-cement composite(s)
National Category
Biomaterials Science Engineering and Technology
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-213224DOI: 10.1016/j.jmbbm.2014.01.002ISI: 000333488300024OAI: oai:DiVA.org:uu-213224DiVA: diva2:681322
Available from: 2013-12-19 Created: 2013-12-19 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Injectable Biomaterials for Spinal Applications
Open this publication in new window or tab >>Injectable Biomaterials for Spinal Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of injectable biomaterials is growing as the demands for minimally invasive procedures, and more easily applicable implants become higher, but their availability is still limited due to the difficulties associated to their design.

Each year, more than 700,000 vertebral compression fractures (VCF’s) are reported in the US and 500,000 VCF’s in Europe due to primary osteoporosis only. VCF’s can compromise the delicacy of the spinal canal and also cause back pain, which affects the patient’s quality of life. Vertebroplasty was developed in the 80’s, and has proven to be a safe minimally invasive procedure that can, quickly and sustainably, relieve the pain in patients experiencing VCF’s. However, biomaterials for vertebroplasty still have limitations. For instance, ceramic bone cements are difficult to distinguish from the bone using X-ray techniques. On the other hand, acrylic bone cements may cause adjacent vertebral fractures (AVF’s). Large clinical studies have indicated that 12 to 20% vertebroplasty recipients developed subsequent vertebral fractures, and that 41 to 67% of these, were AVF’s. This may be attributed to the load shifting and increased pressure on the adjacent endplates reached after vertebroplasty with stiff cements.

The primary aim of this thesis was to develop better injectable biomaterials for spinal applications, particularly, bone cements for vertebroplasty. Water-soluble radiopacifiers were first investigated to enhance the radiopacity of resorbable ceramic cements. Additionally, different strategies to produce materials that mechanically comply with the surrounding tissues (low-modulus bone cements) were investigated. When a suitable low-modulus cement was produced, its performance was evaluated in both bovine bone, and human vertebra ex vivo models.

In summary, strontium halides showed potential as water-soluble radiocontrast agents and could be used in resorbable calcium phosphates and other types of resorbable biomaterials. Conversely, linoleic acid-modified (low-modulus) cements appeared to be a promising alternative to currently available high-modulus cements. It was also shown that the influence of the cement properties on the strength and stiffness of a single vertebra depend upon the initial bone volume fraction, and that at low bone volume fractions, the initial mechanical properties of the vertebroplasty cement become more relevant. Finally, it was shown that vertebroplasty with low-modulus cements is biomechanically safe, and could become a recommended minimally invasive therapy in selected cases, especially for patients suffering from vertebral compression fractures due to osteoporosis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1114
Keyword
injectable, biomaterials, bone cement, vertebral compression fractures, spine, radiopacity, minimally invasive treatment, low-modulus cement, oligomer, PMMA, calcium phosphate, vertebroplasty, bone
National Category
Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-215606 (URN)978-91-554-8854-3 (ISBN)
Public defence
2014-02-28, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
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Supervisors
Available from: 2014-02-05 Created: 2014-01-15 Last updated: 2014-02-10

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López, AlejandroMestres, GemmaKarlsson Ott, MarjamEngqvist, HåkanPersson, Cecilia

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