Abstract
Background: One difference in approved PMMA bone cement brands used in cemented arthroplasties is the powder sterilization method (most commonly, γ irradiation or ethylene oxide (EtO) gas). Each of the two literature studies on the influence of powder sterilization method on properties of approved bone cement brands involved determination of familiar mechanical properties (namely, tensile strength and fracture toughness) of one brand.
Purpose: To determine the influence of powder sterilization method for bone cement (and, hence, its reduced viscosity (a proxy for its molecular weight (MW)) on two cement quasi-static mechanical properties that are not well known in the biomaterials literature; namely, notch tensile strength (σNT) and specific fracture energy (Gf). 10 approved brands were used, in 4 of which the powder was γ- irradiated while, in the other 6, it was exposed to EtO gas.
Materials and Methods: A methodology comprising a combination of compact tension specimen and the wedge-splitting test method (“CTWST methodology”) was used to determine σNT and Gf. Also, reduced viscosity was determined for each of the brands. Statistical treatment of the results was conducted using regression analysis and a non-parametric test of significance.
Results: With increase in η, the increase in σNT was significant but moderate (for the best-fit relationship, adjusted R2 = 0.396; RMSE = 2.363), whereas the increase in Gf was significant and very marked (adjusted R2 = 0.901; RMSE = 1.221). This trend was confirmed by the intergroup difference in σNT (p = 0.003) and in Gf (p << 0.001).
Conclusion: Based on the results, we recommend that the CTWST methodology be added to the collection of methods used to characterize the quasi-static mechanical behavior of PMMA bone cement.
Keywords: EtO gas, mechanical properties, PMMA bone cement, powder sterilization, regression analysis, wedge-splitting test method.
Graphical Abstract
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