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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. 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).
Damage evolution of musculoskeletal systems: Repetitive loading of implant systems can result in early loosening. In fact, early motion (stability) of implant systems is an excellent predictor of long term viability of implants. We have been studying damage evolution to PMMA cement that is used to fix implants to bone. Through a combination of experimental work and companion modeling efforts, we are developing improved computational tools to predict long term success of joint replacements. (NIH funded).
Biomechanical assays to investigate skeletal tumor burden and development of surrogates of bone strength: Bone is a common site for metastases of primary tumors such as breast, prostate, ovarian, lung, and colon cancer. A collaborator (M Allen) has developed a model of breast cancer to bone in a murine model. We have been using this model to directly assess biomechanical strength and relate this to existing paradigms used in clinical medicine. In addition we are developing indirect biomechanical assays or surrogates of bone strength using voxel-based finite element modeling approaches coupled with in vivo imaging. This work has the potential to improve our ability to predict which clinical patients require surgical reconstruction and also to monitor how patients are responding to radiation and anti-resorptive or anabolic drug therapies. (Funding from Baldwin Foundation.)
Role of therapeutic radiation in increasing fracture risk of bone: Using a murine model of radiation damage to the femur we are investigating the implications of bony remodeling in terms of structure and fundamental changes to bone material fracture resistance. We are using nano-indentation to quantify elastic and inelastic behavior of trabecular and cortical bone. 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. (Funding by: Baldwin Foundation)
Recent Representative Publication
1. 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, 2013.
2. 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, 2013.
3. 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.
4. 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.
5. 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.
6. 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.
7. Mann KA, Miller MA. Fluid-structure interactions in micro-interlocked regions of the cement-bone interface. Computer Methods in Biomechanics and Biomedical Engineering, In press, March 2013.
8. Waanders D, Janssen D, Berahmani S, Miller MA, Mann KA, Verdonschot N. Interface micromechanics of transverse sections from retrieved cemented hip reconstructions: an experimental and finite element comparison. J Mater Sci Mater Med. 23(8): 2023-35, 2012.
9. Mann KA, Miller MA, Pray CL, Verdonschot N, Janssen D. A new approach to quantify trabecular resorption adjacent to cemented knee arthroplasty. Journal of Biomechanics, 45: 711-715, 2012
10. Mann KA, Miller MA, Khorasani, M, Townsend KL, Allen MJ. The dog as a preclinical model to evaluate interface morphology and micro-motion in total knee replacement. Vet Comp Orthop Traumatol, 25(1):1-10, 2012.