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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, 2013-2015.)
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
1. Howard KI, Miller MA, Damron TA, Mann KA. The distribution of implant fixation for femoral components of TKA: A postmortem retrieval study. J Arthroplasty, 29(9): 1863-1870, 2014.
2. Miller MA, Terbush MJ, Goodheart JR, Izant TH, Mann KA. Increased initial cement-bone interlock correlates with reduced TKA micro-motion following in vivo service. J Biomechanics, 47:2460-2466, 2014.
3. Goodheart JR, Miller MA, Mann KA. In vivo loss of cement-bone interlock reduces fixation strength in total knee arthroplasties. J Orthop Res. 32(8): 1052-60, 2014.
4. Mann KA, Miller MA, Goodheart JR, Izant TH, Cleary RJ. Peri-implant bone strains and micro-motion following in vivo service: A postmortem retrieval study of 22 tibial components from totak knee replacements. J Orthop Res. 32(3): 355-61, 2014.
5. Oest ME, Miller MA, Howard KI, Mann KA. A novel in vitro loading system to produce supraphysiologic oscillatory fluid shear stress. J Biomech, 47(2):518-25, 2014.
6. Miller MA, Goodheart JR, Izant TH, Rimnac CM, Cleary RJ, Mann KA. Loss of cement-bone interlock in retrieved tibial components. Clin Orthop Rel Res, 472(1):304-13, 2014.
7. Mann KA, Miller MA. Fluid-structure interactions in micro-interlocked regions of the cement-bone interface. Computer Methods in Biomechanics and Biomedical Engineering, 17(16): 1809-20, 2014.
8. Gong B, Oest ME, Mann KA, Damron TA, Morris MD. Raman Spectroscopy demonstrates prolonged alteration of bone chemical composition following extremity localized irradiation. Bone, 57(1): 252-258, 2013.
9. Keenawinna L, Oest ME, Mann KA, Spadaro JA, Damron TA. Zoledronic Acid Prevents Loss of Trabecular Bone Following Focal Irradiation in Mice. Radiation Research, 180(1):89-99, 2013.
10. Murphy CT, Eberhardt WC, Calhoun BH, Mann KA, Mann DA. Effect of angle on flow-induced vibrations of pinniped vibrissae. PLOS One, 8(7), July 2013.