Micro-mechanics of implant interfaces; damage evolution of joint replacements and biomaterials; in vivo models of tumor osteolysis and prediction of fracture risk; general orthopedic biomechanics.
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Micromechanics and micro-mechanical modeling of bone-implant interfaces: Implant fixation is vital to long-term success of mechanically loaded implant systems. Surprisingly little is known about the load transfer mechanisms and motion at the length scales of trabeculae (~1mm) and below. In addition, there are often dramatic changes in bone remodeling around implants with in vivo use. For cemented implants, the loss of interlock between trabeculae and cement can be dramatic. We have been performing in vitro experiments on small components of bone-implant interfaces in which small (micron scale) loading is applied in tension, compression, and shear. We incorporate digital image correlation techniques to map local strain fields subjected to loading. The long-term goal here is to improve our understanding of local motions at the interface and how motion is related to bony response. Both experimental and computational models are performed on laboratory prepared and post-mortem retrieved specimens. (NIH funded: 2012-2017).
Predicting bone fracture in patients with metastatic disease. Primary tumors, such as breast and prostate cancer, can metastasize to bone cause bone destruction and bone fracture. Predicting whether a bone with metastatic disease will fracture remains a clinical challenge. Clinical scoring systems based on X-ray and patient pain levels are not good predictors for determining which bones require surgical stabilization. We are using Finite Element (FE) modeling of clinical CT scan sets in collaboration with Dr. Timothy Damron to determine activities of daily living that are predictive of fracture.The long term goal is to use FE as a tool to help surgeons decide which patients to stabilize from those that are not at risk of fracture. (Funding from Baldwin Foundation, 2016-2018.)
Role of therapeutic radiation in increasing fracture risk of bone: Using a murine model of radiation damage to the extremities (PI: T Damron, Co-inv: M Oest-Upstate, M Morris-U Michigan) we are investigating the implications of bony remodeling in terms of structure and fundamental changes to bone material fracture resistance and chemical changes to the bone. We are using biomechanical strength tests and fracture toughness tests to monitor changes in bone structure and material properties with time, radiation dose, and anabolic, antiresorptive and radioprotection treatments. We are also using a combination of voxel-based finite element modeling with material damage models and comparing these to experiments to gain a better understanding of bone ‘brittle’ behavior. (NIH funded: 2014-2019)
Recent Representative Publications