Towards the Improvement of Orthopaedic Treatments: Addressing Cartilage Transplantations and Talar Replacement Surgeries

Articular cartilage plays a vital role in smooth joint motion and load distribution but has a limited capacity for self -repair following injury. Osteochondral allograft transplantation s are treatment procedures for focal cartilage injuries where the damaged cartilage is replaced with donor tissue. For degenerative articular cartilage diseases or bone fractures, particularly those of the talus bone in the human ankle joint, talar replacement surgeries are performed. Both osteochondral allograft transplantations and talar replacement surgeries present clinical challenges that this research aimed to address . The primary goal was to mechanically evaluate cartilage stored under different conditions for use in osteochondral transplantations and to develop enhanced implants for talus bone replacement surgeries. Osteochondral allograft transplantations have challenges related to the availability of fresh donor tissue and the limited storage time of allografts. The extended storage time offered by vitrified allografts presents a promising solution. However, the effect of vitrification on the mechanical properties of articular cartilage, which are crucial for cartilage functionality, had not been previously investigated. This research addressed this knowledge gap by conducting mechanical evaluations of fresh, frozen, and vitrified articular cartilage through ex -vivo and in -vivo experiments. By comparing the mechanical properties of articular cartilage under these different storage conditions, valuable insights were gained regarding the suitability of vitrification protocols for osteochondral allograft transplantations. The results demonstrated that vitrified allografts have mechanical properties that are similar to , and in some cases superior to, those of fresh allografts which degraded overtime as they were stored. T herefore, vitrified allografts can be used in osteochondral allograft transplantations to potentially expand the availability of donor grafts. For talar replacement surgeries, several issues exist that can affect patient experience and outcomes. The lengthy surgical planning process associated with the use of customized implants leads to delayed treatment which prolongs patient discomfort. Additionally, the articulation of the metal talus prosthesis against adjacent cartilage in the ankle joint can result in cartilage wear, leading to complications and compromised joint health. This research aimed to address these issues by developing a universal talus implant with a soft polycarbonate urethane (PCU) coating that can minimize cartilage wear. Finite element simulations of the ankle joint with PCU -coated talus implants were conducted and compared with non-PCU coated implants. Results indicated that the PCU-coated implants had contact characteristics that are similar to the biological models. Following this, different PCU-implant interfaces that can be used for attaching a layer of PCU to the implant were designed and manufactured. The diamond lattice interface with a 4×4×4 cell size was identified as the most suitable design, as it demonstrated the highest bonding strength during mechanical shear testing. Finally, the wear behavior of PCU when articulating against articular cartilage was evaluated and compared with other implant biomaterials (cobalt chrome alloy, titanium alloy, ultra-high molecular weight polyethylene , and polyether ether ketone ), demonstrating superior performance. These results sugge st that PCU may be an appropriate material coating for talar implants. The use of universal PCU-coated talus implants has the potential to improve patient experiences and enhance the long-term outcomes of talar replacement surgeries. To conclude, this research presents a comprehensive and novel approach to addressing the challenges faced in osteochondral allograft transplantations and talar replacement surgeries. By conducting mechanical evaluations and exploring new materials for implant design, this research aimed to advance orthopaedic treatments and improve patient outcomes.