bone cements are materials used as adhesives to fix bone prostheses (hip, knee, shoulder…) when the quality of the patient’s bone is insufficient. However, during its component assembly and placement process, elevated temperatures are generated, which can lead to necrosis in the surrounding tissues of patients.
Adding highly reduced graphene oxide helps to avoid this problem and also improves the mechanical and thermal properties of materials, according to a study carried out by researchers from the Polytechnic University Madrid (UPM) . The results, published in the journals Polymers and Biomedical Journal of Scientific & Technical Research , are of interest in the insertion surgeries of prostheses fixed with bone cements, more common in older people.
Adding highly reduced graphene oxide to bone cements improves their mechanical and thermal properties
The implantation of prostheses is an increasingly common practice throughout the world, due to causes such as the increase and aging of the population, and due to a higher incidence of pathologies such as obesity or osteoarthritis. Bone cements serve to adhere and fix prostheses to damaged bone when the bone does not have sufficient mechanical strength and is unable to grow over the prosthesis and stabilize it, in addition to distributing loads and helping to cushion the stresses in the prosthesis-bone junction.
However, this material has some limitations. The maximum life of this bone cement is 20 years, and statistically it is too risky to operate on people older than 85 years, so that from that age it would no longer be advisable to repair a prosthesis whose materials have deteriorated. Therefore, a 65-year-old patient who is implanted with a hip prosthesis fixed to the bone with a bone cement will be exposed to the bone cement to degrade or break, due to cracks that grow slowly over time, which it would generate discomfort for the rest of his life because a new surgery was not feasible.
Improve the quality of life of the elderly
“Improving the durability of these bone cements is essential to improve the quality of life of our elderly. In other words, avoid them having to endure an existence with chronic pain due to the broken prosthesis ”, points out José Ygnacio Pastor , a researcher at the UPM who participated in the study.
In the research carried out by members of the Center for Research in Structural Materials ( CIME ) of this university, various materials have been developed with potentially interesting results, such as reducing the maximum curing temperature that damages adjacent tissues.
There are only a few minutes to place the cement between the bone and the prosthesis, and during this reaction a lot of energy is released that reaches and heats the surrounding tissues. The addition of graphene slows down and lowers the temperature of the reaction
Regarding mechanical properties, researchers have found that adding an excess of graphene is harmful and worsens them, but small amounts (between 0.01% and 0.1% by weight) could also produce improvements in the mechanical properties while maintaining the thermal benefit.
“Until now we have mainly talked about the mechanical strength and durability of bone cement; however, there are more problems associated with the use of these cements in the human body ”, points out co-author Jaime Orellana.
Common cements are made up of two components that, once they come together, begin to react and harden. During this reaction the material solidifies rapidly, and there are few minutes to place it between the bone and the prosthesis. In addition, a lot of energy is released during this reaction that reaches the surrounding tissues.
Since proteins are denatured from 42⁰C, if the bone is heated too much, the cells die and there is necrosis of the tissue surrounding the prosthesis. Thus, “it is essential to prevent the bone from heating up , a result that we have achieved by slowing down the reaction thanks to the addition of highly reduced graphene,” continues Orellana.
According to the researchers, the expectations of these new materials are very promising, as there are also indications that graphene has antibacterial properties , which is ideal for reducing infection problems after surgery. “However, there is much work ahead, because not only the amount of graphene to be introduced must be optimized, but also the chemical treatments that allow graphene better adhesion and dispersion in the bone cement must be studied,” they conclude.
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