Seasoning Polymethyl Methacrylate (PMMA) Bone Cements with Incorrect Mix Ratio

Abstract

Cemented joint prostheses are widely used in orthopaedic surgery; however, implants/bone bonds are known to be susceptible to aseptic loosening, particularly in the case of long-term performance. The exact mechanism of this failure is under constant examination. One of the critical factors to the final mechanical functionality of bone cement can be an incorrect mix ratio of a two-component material (powdered polymer and liquid monomer). It can result in the deterioration of the final mechanical strength properties. The paper presents the results from an experimental study on the effects of the deviation from the correct mix ratio on the moisture uptake and the compression strength of cement depending on the seasoning time in Ringer’s solution. The results were subjected to statistical analysis and a mathematical model was developed.

Effect of Physiological Fluids Contamination on Selected Mechanical Properties of Acrylate Bone Cement

“…It was resolved that the contaminants should be introduced into the cement mass at the material preparation stage, which was dictated by two factors: First, soaking the samples in blood or saline would only contaminate the periphery of the specimen and, secondly, an additional factor—time—would appear in the tests. The longer the soaking, the greater and the deeper the absorption (as shown in our former study: [22]). It is for these reasons that full-contamination testing was undertaken.…”

“…With a view to reducing the number of tests and simplifying the study, additional parameters that have a bearing on the cement strength and the inclusion of which would more closely reflect the actual conditions of the cement operation were also omitted. This includes the problem of cement aging over time, which could be incorporated in the future research plans [64,65], along with other factors such as the impact of the human body conditions on the strength characteristics of prosthetic materials, which could be simulated by means of seasoning in Ringer’s solution [22] or saline solution [66]. Finally, it must be highlighted that in the reported analyses, the cement samples were subject to testing at an ambient temperature lower than the average regular human body temperature, which determines a further area of experimental exploration in the field.…”

“…The basic strength properties, crack resistance or fatigue and creep strength are also strongly associated with the implantation process and factors pertaining to the human body environment, such as the admixture of blood and physiological fluids or the presence of bone tissue residues in the cement structure [17,18,19,20,21]. The cement preparation technique [22] and the conditions in the operative field have been also found to be of considerable importance. Despite their significance, several factors determine that the appropriate conditions are not ensured, thus facilitating bone contamination; these include substandard work organisation, hospital conditions, financial issues or the orthopaedist’s habits.…”

“…To establish a set of critical features of materials used in orthopaedic surgery, theoretical and experimental methods must be employed. Conducting experiments on humans is both a difficult and time-consuming process and should be limited for ethical reasons, which is why basic research works that involve the use of physical and numerical models could be used to provide an accurate representation of the actual operating conditions of the investigated objects [22,31,32,33]. Therefore, with the aim of broadening the perspective on the problem, the properties of bone cements and their changes should not be necessarily tested in surgery.…”

“…Far too little attention has been paid to the effect of contamination on the cement strength properties, in particular in the presence of human blood [34]. The focus of bone-cement studies is on admixtures of auxiliary agents, supplied to improve the material’s properties, including strength [22,26,33,35,36,37,38].…”