Unmet NeedOver 2 million joint replacement surgeries are done per year in the United States. However, the biomechanic functionality of joint implants is often limited because of the large discrepancies between the native bone of the patient and the material and structural properties of the metallic implants. In addition to the material of the implant being greatly different from actual bone, each and every patient has unique bone properties, which can affect the way that an implant fits a patient’s body. In current medical practice, joint implants have standardized sizes, and there exists a belief that all implants will behave the same in every body. However, because of this over-standardization, there are significant limitations in geometry, material, and structural properties of these implants. Additionally, there are major limitations in the design of traditional implants which can limit their use in a variety of surgical applications. Thus, a way to create customized, proper structural models for joint replacements is needed.
Technology OverviewJohns Hopkins inventors have created a new approach to design structures for joint replacement surgeries. They are utilizing computer aided methods to generate structural models from CT scans for individual patients’ bones in a semi-automated fashion. They are coupling this method with topology optimization, which utilizes mathematical sensitivity information as the main driver for improving performance. Using this method, the inventors have been able to design implants such that the material layout within the defined implant geometry is based on regional demands rather than standardized sizes and material. Thus, the entire structure of the implant design can be optimized to satisfy a variety of design goals and to generate the most structurally optimal implants that are mechanically feasible.
The inventors have also been able to modulate implant stiffness throughout the domain to most optimally interact with patients’ local bone material properties, and to minimize adverse stress/strain distributions within the bone. Additionally, the outputs of this design method interface seamlessly with automated or additive manufacturing methods, such as 3D printing. As a result, the implants can be composed of different commonly used orthopedic materials such as titanium, cobalt chrome, or different polymers. Using these methods, the inventors’ technology enables the design to either be semi-hollow or fully trabecular, demonstrating a significant improvement of their implant over many commercially available implants.
Stage of DevelopmentThe inventors have currently employed their technique in a variety of total hip femoral implants and have built models for several different bone qualities. They will apply the same technology in future testing with total knee and ankle tibial implants.
