uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Publications (7 of 7) Show all publications
Robo, C. (2018). Bone-compliant cements for vertebral augmentation. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Bone-compliant cements for vertebral augmentation
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Acrylic bone cement based on poly(methyl methacrylate) (PMMA) is commonly used during vertebral augmentation procedures for the treatment of osteoporosis-induced vertebral compression fractures. However, the high stiffness of the cement compared to that of the surrounding trabecular bone is presumed to facilitate the formation of new fractures shortly after surgery. The aim of the thesis was to develop and evaluate a PMMA-based bone cement that better matches the mechanical properties of vertebral trabecular bone. To fulfill this objective, different compounds were added to the initial formulation of bone cement to modify its functional properties. Linoleic acid (LA) was found to give the best combination of strength and stiffness without negative effects on the handling properties and its use was therefore further investigated. In particular, different application-specific mechanical properties of LA-modified cement as well as itsin vivoperformance in an ovine model were assessed. 

In summary, LA-modified cement exhibited bone-compliant mechanical properties immediately after incorporation of the additive, as well as adequate handling properties, in particular a lower polymerization temperature and appropriate setting time. The screw pullout strength from low-modulus cement was substantially reduced compared to regular PMMA cement, but comparable to some calcium phosphate based cements. The fatigue limit of LA-modified cement was considerably lower compared to regular PMMA bone cement when tested in physiological solution, but still higher than stresses measured in the spine during daily activities. The modified cement displayed similar inflammatory response in vivoto conventional cement, with no evidence of additional cytotoxicity due to the presence of LA. Finally, it was possible to sterilize the additive without significantly compromising its function in the PMMA cement.

The results from this thesis support further evaluation of the material towards the intended clinical application. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 92
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1676
Keywords
bone cement, low modulus, vertebroplasty
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-349028 (URN)978-91-513-0351-2 (ISBN)
Public defence
2018-06-07, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2018-05-16 Created: 2018-04-20 Last updated: 2018-10-08
Robo, C., Öhman, C. & Persson, C. (2018). Compressive fatigue properties of commercially available standard and low-modulus acrylic bone cements intended for vertebroplasty. Journal of The Mechanical Behavior of Biomedical Materials, 82, 70-76
Open this publication in new window or tab >>Compressive fatigue properties of commercially available standard and low-modulus acrylic bone cements intended for vertebroplasty
2018 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 82, p. 70-76Article in journal (Refereed) Published
Abstract [en]

Vertebroplasty (VP) is a minimally invasive surgical procedure commonly used to relieve severe back pain associated with vertebral compression fractures. The poly(methyl methacrylate) bone cement used during this procedure is however presumed to facilitate the occurrence of additional fractures next to the treated vertebrae. A reason for this is believed to be the difference in stiffness between the bone cement and the surrounding trabecular bone. The use of bone cements with lower mechanical properties could therefore reduce the risk of complications post-surgery. While intensive research has been performed on the quasi-static mechanical properties of these cements, there is no data on their long-term mechanical properties. In the present study, the in vitrocompressive fatigue performance as well as quasi-static mechanical properties of two commercially available acrylic bone cements - a low-modulus cement (Resilience®) and a standard cement (F20) from the same manufacturer - were determined. The quasi-static mechanical properties of the low-modulus and standard cements after 24h of setting were in the range of other vertebroplastic cements (σ=70-75 MPa; E=1600-1900 MPa). F20 displayed similar mechanical properties over time in 37˚C phosphate buffered saline solution, while the mechanical properties of the Resilience®cement decreased gradually due to an increased porosity in the polymeric matrix. The standard cement exhibited a fatigue limit of approx. 47 MPa, whereas the low-modulus cement showed a fatigue limit of approx. 31 MPa. 

In summary, the low-modulus bone cement had a lower fatigue limit than the standard cement, as expected. However, this fatigue limit is still substantially higher than the stresses experienced by vertebral trabecular bone.  

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Acrylic bone cement, low-modulus, elastic modulus, compression, fatigue, vertebroplasty
National Category
Other Materials Engineering Biomaterials Science Medical Materials
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-349032 (URN)10.1016/j.jmbbm.2018.03.001 (DOI)000432508800009 ()
Funder
The Royal Swedish Academy of Sciences, FOA13H-141
Available from: 2018-04-20 Created: 2018-04-20 Last updated: 2018-12-05
Robo, C., Hulsart Billström, G., Nilsson, M. & Persson, C. (2018). In vivo response to a low-modulus PMMA bone cement in an ovine model. Acta Biomaterialia, 72, 362-370
Open this publication in new window or tab >>In vivo response to a low-modulus PMMA bone cement in an ovine model
2018 (English)In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 72, p. 362-370Article in journal (Refereed) Published
Abstract [en]

Poly(methyl methacrylate) (PMMA) is the most commonly used material for the treatment of osteoporosis-induced vertebral compression fractures. However, its high stiffness may introduce an increased risk of adjacent vertebral fractures post-surgery. One alternative in overcoming this concern is the use of additives. This presents its own challenge in maintaining an adequate biocompatibility when modifying the base cement. The aim of this study was to evaluate the in vivobiocompatibility of linoleic acid (LA)-modified acrylic bone cement using a large animal model for the first time, in order to further advance towards clinical use. A worst-case approach was used, choosing a slow-setting base cement. The in vitro monomer release from the cements was also assessed. Additional material characterization, including mechanical tests, are summarized in Appendix A. Unmodified and LA-modified cements were injected into a total of 56 bone defects created in the femur and humerus of sheep. Histopathologic and histomorphometric analysis indicated that LA-modified cement showed a harmless tissue response similar to that of the unmodified cement. Adjacent bone remodeling was observed microscopically 4 weeks after implantation, suggesting a normal healing process of the bone tissues surrounding the implant. LA-modified cement exhibited lower mechanical properties, with a reduction in the elastic modulus of up to 65%. The handling properties were slightly modified without negatively affecting the injectability of the base cement. LA-modified bone cement showed good biocompatibility as well as bone compliant mechanical properties and may therefore be a promising material for the treatment of osteoporotic vertebral fractures. 

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Poly (methyl methacrylate), bone cement, low-modulus, In vivo, linoleic acid
National Category
Other Materials Engineering Medical Materials Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-349033 (URN)10.1016/j.actbio.2018.03.014 (DOI)000432766900031 ()29559365 (PubMedID)
Funder
VINNOVA, 2010-02073
Available from: 2018-04-20 Created: 2018-04-20 Last updated: 2018-12-05
Pujari-Palmer, M., Robo, C., Persson, C., Procter, P. & Engqvist, H. (2018). Influence of cement compressive strength and porosity on augmentation performance in a model of orthopedic screw pull-out. Journal of The Mechanical Behavior of Biomedical Materials, 77, 624-633
Open this publication in new window or tab >>Influence of cement compressive strength and porosity on augmentation performance in a model of orthopedic screw pull-out
Show others...
2018 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 77, p. 624-633Article in journal (Refereed) Published
Abstract [en]

Disease and injuries that affect the skeletal system may require surgical intervention and internal fixation, i.e. orthopedic plate and screw insertion, to stabilize the injury and facilitate tissue repair. If the surrounding bone quality is poor the screws may migrate, or the bone may fail, resulting in screw pull-out. Though numerous studies have shown that cement augmentation of the interface between bone and implant can increase screw holding strength in bone, the physical properties of cement that influence pull-out force have not been investigated. The present study sought to determine how the physical properties of calcium phosphate cements (CPCs), and the strength of the biological or synthetic material surrounding the augmented screw, affected the corresponding orthopedic screw pull-out force in urethane foam models of healthy and osteoporotic bone (Sawbones). In the simplest model, where only the bond strength between screw thread and cement (without Sawbone) was tested, the correlation between pull-out force and cement compressive strength (R2 = 0.79) was weaker than correlation with total cement porosity (R2 = 0.89). In open pore Sawbone that mimics “healthy” cancellous bone density the stronger cements produced higher pull-out force (50-60% increase). Higher strength, lower porosity, cements also produced higher pull-out forces (50-190% increase) in Sawbones with cortical fixation if the failure strength of the cortical material was similar to (bovine tibial bone), or greater than (metal shell), actual cortical bone. This result is of particular clinical relevance where fixation with a metal plate implant is indicated, as the nearby metal can simulate a thicker cortical shell and, thereby, increase the pull-out force of screws augmented with stronger cements. The improvement in pull-out force was apparent even at low augmentation volumes of 0.5 ml (50% increase), which suggest that in clinical situations where augmentation volume is limited the stronger, lower porosity CPCs may still produce a significant improvement in screw holding strength. When correlations of all the tested models were compared both cement porosity and compressive strength accurately predicted pull-out force (R2=1.00, R2=0.808), though prediction accuracy depended upon the strength of the material surrounding the Sawbone. The correlations strength was low for bone with no, or weak, cortical fixation. Higher strength and lower porosity CPCs also produced greater pull-out force (1-1.5 kN) than commercial CPC (0.2-0.5kN), but lower pull-out force than PMMA (2-3 kN). The results of this study suggest that the likelihood of screw fixation failure may be reduced by selecting calcium phosphate cements with lower porosity and higher bulk strength, in patients with healthy bone mineral density and/or sufficient cortical thickness. This is of particular clinical relevance when fixation with metal plates is indicated, or where the augmentation volume is limited.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Screw pull-out, Orthopedic screw augmentation, Calcium phosphate cement, Bioceramic, Bone biomechanics, Sawbones, Cortical fixation
National Category
Medical Materials Ceramics Applied Mechanics Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-320157 (URN)10.1016/j.jmbbm.2017.10.016 (DOI)000418309500073 ()29100205 (PubMedID)
Funder
Swedish Research Council, 621–2011-3399EU, FP7, Seventh Framework Programme, 262948
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2018-02-16Bibliographically approved
Persson, C., Robert, E., Carlsson, E., Robo, C., Lopez, A., Godoy-Gallardo, M., . . . Engqvist, H. (2015). The effect of unsaturated fatty acid and triglyceride oil addition on the mechanical and antibacterial properties of acrylic bone cements. Journal of biomaterials applications, 30(3), 279-289
Open this publication in new window or tab >>The effect of unsaturated fatty acid and triglyceride oil addition on the mechanical and antibacterial properties of acrylic bone cements
Show others...
2015 (English)In: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022, Vol. 30, no 3, p. 279-289Article in journal (Refereed) Published
National Category
Textile, Rubber and Polymeric Materials Other Materials Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-251353 (URN)10.1177/0885328215581316 (DOI)000361767300003 ()
Funder
EU, FP7, Seventh Framework Programme, FP7-PEOPLE-2010-268134VINNOVA, 2010-02073The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG2011-2047
Available from: 2015-04-16 Created: 2015-04-16 Last updated: 2018-04-20Bibliographically approved
Robo, C. Functional properties of low-modulus PMMA bone cements containing linoleic acid.
Open this publication in new window or tab >>Functional properties of low-modulus PMMA bone cements containing linoleic acid
(English)In: Article in journal (Other (popular science, discussion, etc.)) In press
Abstract [en]

Spinal augmentation using rigid acrylic bone cement may facilitate the formation of additional vertebral compression fractures (VCFs) in the vicinity of the collapsed vertebrae. It has been hypothesized that the use of less stiff bone cement could reduce the occurrence of adjacent VCFs. Acrylic bone cement modified with linoleic acid (LA) has been reported as a promising low-modulus alternative. However, several key properties remain unexplored. In this study, the flexural properties and screw augmentation capacity of the LA-modified cement were evaluated. The effect of sterilization through autoclaving was assessed in terms of LA composition and cement handling properties, glass transition temperature (Tg) and quasi-static compressive mechanical properties. 

The bending modulus, bending strength and pull-out force were, as with the compressive properties, significantly affected by the addition of LA, giving mechanical properties closer to those of vertebral trabecular bone. The maximum polymerization temperature was significantly lower for LA-modified cement (28.2 ± 0.4 °C for non-sterile and 31.1 ± 1.1 °C for sterile material) than the control cement (66.8 ± 3 °C). The setting time of the cements remained comparable, at between 20-25 minutes, but LA-modified cements could be injected over a longer period than the regular cement. Sterilized and non-sterilized LA-modified cements displayed similar injectability and mechanical properties over time. The Tgof sterilized LA-cement (78.0 ± 3.2 °C) was not statistically different from the Tgof non-sterilized LA-cement (74.7 ± 4.8 °C) but both were significantly lower than the Tgof the control cement (102.8 ± 1.3 °C). 

In summary, a sterilization process could be used without significantly affecting the functional properties of LA-modified cement. These cements displayed excellent handling and mechanical properties that more closely match those of osteoporotic vertebral bone. They exhibited a pullout strength comparable to some ceramic bone cements, demonstrating potential for use in applications where hardware needs to be applied. 

Keywords
Acrylic bone cement, low-modulus, mechanical properties, bending, vertebroplasty, screw, pullout, sterilization
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-349057 (URN)
Available from: 2018-04-20 Created: 2018-04-20 Last updated: 2018-04-20
Robo, C. Long-term mechanical properties of a low-modulus bone cement for the treatment of vertebral compression fractures.
Open this publication in new window or tab >>Long-term mechanical properties of a low-modulus bone cement for the treatment of vertebral compression fractures
(English)In: Article in journal (Other (popular science, discussion, etc.)) In press
Keywords
Acrylic bone cement, low-modulus, elastic modulus, compression, fatigue, vertebroplasty
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-349059 (URN)
Available from: 2018-04-20 Created: 2018-04-20 Last updated: 2018-04-20
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4139-6913

Search in DiVA

Show all publications