Critical analysis on dynamic-mechanical performance of spongy bone: the effect of acrylic cement

Introduction Over the past years, in order to anchor a prosthetic component to bone, different cements based on selfpolymerizing poly (methyl methacrylate) (PMMA) have been widely used as commercial synthetic biomaterials. The aim of this study was to evaluate the influence of a PMMA-based bone cement (Palamed® G40) on the viscoelastic behaviour of spongy bone from proximal human tibial epiphyses, and the assessment of the dynamic-mechanical properties of the natural tissue. Materials and methods The effect of acrylic bone cement on the dynamic-mechanical performance of spongy bone was assessed by means of dynamic three-point bending tests. All the tests were performed in physiological solution at 37±0.5°C, scanning the frequency from 0.01 to 30 Hz. Samples from proximal human tibial epiphyses were cut along the medial-lateral and anterior-posterior directions considering different regions of the subchondral tibial plate. The dynamicmechanical properties of specimens infiltrated the PMMA-based bone cement were evaluated in the frequency range investigated. Results The results have highlighted that the viscoelastic properties of spongy bone vary with direction and region, and the PMMA-based bone cement increases the storage modulus (E’) of spongy bone of about 100%. However, for bone-cement system, the values of loss factor (tan d) are close to those of the natural structure. Moreover, micro-computed tomography (μCT) has allowed to study the architecture of bone and its interface with the cement. Conclusion The present study has evidenced that bone infiltration allows to enhance the mechanical performances of spongy bone. Furthermore, taking into account the analysis of the viscoelastic properties of the natural structure, future trends will be focused on the possibility to design a prosthetic implant, which emulates the biomechanical behaviour of the natural tissues, or a suitable cement, which improves the mechanical properties of spongy bone.