Biocompatible PUD/rGO composite cartilage pads for artificial hip joints: Mechanical characterization and numerical simulation

Background Wear and wear debris generated from the bearing components of artificial hip prostheses may contribute to osteolysis, implant loosening, and eventual prosthesis failure. To address these limitations, an elastic composite based on polyurethane dispersion (PUD) reinforced with reduced graphene oxide (rGO) was investigated as a potential elastic cartilage pad (ECP) material for artificial hip prostheses. Method PUD/rGO composite specimens with different formulations were fabricated using ultrasonic dispersion and freeze-drying. The cytocompatibility of PUD-based test articles was evaluated according to ISO 10993-5. Tensile and compression tests were performed to determine the mechanical properties of the composite, and pin-on-disc friction tests were conducted under dry and phosphate-buffered saline (PBS)-lubricated conditions. The experimentally determined material properties were subsequently incorporated into a three-dimensional finite element model to evaluate the stress and displacement responses of the artificial hip prosthesis under a simplified static loading condition. Result The PUD-based test articles satisfied the ISO 10993-5 acceptance criterion, providing preliminary evidence of the cytocompatibility of the PUD substrate; however, cytotoxicity was not independently evaluated for each PUD/rGO formulation. The simplified two-stage nominal tensile representation was derived from representative points of the experimental tensile load–displacement response. The transition point and ultimate tensile point corresponded to nominal tensile stresses of approximately 0.55 and 1.17 MPa, respectively. Based on the nominal initial specimen length of 16 mm, the first-stage nominal secant modulus ( E t1 ) and second-stage nominal slope ( E t2 ) were approximately 4.40 and 0.33 MPa, respectively. The friction tests demonstrated load- and lubrication-dependent frictional behavior. Finite element analysis showed distinct stress and displacement responses among the investigated material configurations. Under the simplified static loading condition, the PUD/rGO-containing model exhibited limited displacement and redistributed stress among the prosthetic components, supporting the feasibility of incorporating experimentally derived PUD/rGO material properties into an elastic cartilage-pad model. Conclusion The developed PUD/rGO composite demonstrated measurable mechanical and frictional properties relevant to its preliminary evaluation as an elastic cartilage-pad material, while the PUD-based cytotoxicity results provided preliminary evidence of substrate cytocompatibility. Integration of the experimentally determined material parameters with finite element analysis demonstrated the feasibility of the proposed material–numerical evaluation framework. However, the present findings should be interpreted as preliminary because the friction tests and finite element analyses were conducted under simplified experimental and loading conditions that do not fully reproduce physiological hip-joint conditions; further validation using independently fabricated specimens and physiologically relevant testing conditions is required.