Optimisation of a two-liquid component pre-filled acrylic bone cement system: a design of experiments approach to optimise cement final properties

The initial composition of acrylic bone cement along with the mixing and delivery technique used can influence its final properties and therefore its clinical success in vivo. The polymerisation of acrylic bone cement is complex with a number of processes happening simultaneously. Acrylic bone cement mixing and delivery systems have undergone several design changes in their advancement, although the cement constituents themselves have remained unchanged since they were first used. This study was conducted to determine the factors that had the greatest effect on the final properties of acrylic bone cement using a pre-filled bone cement mixing and delivery system. A design of experiments (DoE) approach was used to determine the impact of the factors associated with this mixing and delivery method on the final properties of the cement produced. The DoE illustrated that all factors present within this study had a significant impact on the final properties of the cement. An optimum cement composition was hypothesised and tested. This optimum recipe produced cement with final mechanical and thermal properties within the clinical guidelines and stated by ISO 5833 (International Standard Organisation (ISO), International standard 5833: implants for surgery-acrylic resin cements, 2002), however the low setting times observed would not be clinically viable and could result in complications during the surgical technique. As a result further development would be required to improve the setting time of the cement in order for it to be deemed suitable for use in total joint replacement surgery

Mechanical behaviour of gel-filled additively-manufactured lattice structures under quasi-static compressive loading

The worldwide incidence of traumatic brain injuries (TBIs) is on the rise. Helmets are one of the best technologies available to prevent TBIs from impacts to the head during recreational and occupational activities. The most commonly used material for helmet liners is expanded polystyrene (EPS) foam. However, while EPS can reduce linear accelerations from impacts, it does not perform as well at reducing rotational accelerations which are considered to be the most harmful to brain tissue. Recently, prismatic lattice structures have shown promise in reducing these harmful rotational accelerations. Here, a new structure for energy dissipation applications is presented that is hypothesised to improve the energy dissipation of the prismatic lattice by filling it with a gel. To test this hypothesis, 3D printed prismatic lattices fabricated from PLA, PET-G, and ABS were filled with 5 wt% and 10 wt% agar and tested to failure under quasi-static compression. Compared to the unfilled control group, it was found that PLA lattices filled with 10 wt% agar had the best performance demonstrating a 46.1% increase in energy absorbed and 57.4% increase in displacement to failure. These results demonstrate the superior energy dissipation properties of gel-filled prismatic lattices compared to unfilled prismatic lattices during quasi-static compression. </p