Grant: Discovery Grants Program - Individual

There have been numerous engineering-based biomechanical studies examining various factors related to the human joint, many focused on implant reconstruction. Essentially all of these investigations have employed static or cyclic loading at the articulation. However, very little has been established with regard to the effect of dynamic loading, where the time-dependent (i.e. viscoelastic) properties of the construct, and in particular bone and the interfaces are significant. It is logical to postulate that the introduction of loading in the dynamic range, due to high-velocity or impact related events, will change the load transfer mechanics relative to the static or quasi-static loading case. As individuals following joint reconstruction are becoming more active, it is important to ascertain the influence of dynamic loading for implant design and testing protocols down the road. This research program is designed to establish the importance of dynamic loading on the load transfer mechanics and stress state in the implant-bone construct of the shoulder. To date, experimental shoulder testing employs static loading protocols on cadaver specimens or surrogate foam models. Some recent systems have produced arm motion using simplified muscle controlling protocols and/or robotics. However, these approaches do not accommodate for high velocity and inertial effects. Furthermore, computational finite-element modeling has not typically included dynamic loading. Hence, optimizing our understanding and evaluation of this joint necessitates the development and application of advanced comprehensive testing and modeling approaches that incorporate dynamic loading. The short-term objectives of this research program are to employ both experimental and computational approaches to: (i) determine the effect of dynamic activity on joint loads; (ii) determine the effect of dynamic joint loading on the implant-bone interface. The long-term objective of this program is to produce a state-of-the-art testing program that will permit a wide range of advanced research-based studies on the shoulder, with special interest in simulating joint loading for activities from low-demand to high-velocity(impact) activities. The work proposed herein will certainly revolutionize the understanding of the influence of dynamic loading. These studies will also establish the threshold velocities of motion where inertial effects become relevant. These advances will set the stage for testing methodologies and standards for the assessment of these implants. Ideally, this will lead to the re-drafting of the ASTM standards for implant testing. Furthermore, the general findings related to dynamic loading will have implications for the testing of all other implant reconstructed joints.