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Jueun Lee — 2009-10 Fellow

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The inhomogeneous structure of human bone, including a cortical (dense) portion at the outer part, followed by a cancellous (highly porous) portion and bone marrow, brings considerable complexities to application of bone drilling. The structure of bone varies between different bones (e.g., femur vs. vertebra), between person to person, and between different age groups. In parts of certain bones, a layer of cartilage is present on the top of the cortical bone.

Therefore, without careful attention to the aforementioned thermal and mechanical issues, bone and cartilage drilling can cause considerable damage to the musculoskeletal system, reducing effectiveness of the orthopedic surgery and increasing the post-operation recovery time. While some efforts have been spent on developing mechatronic tools for orthopedic surgery, and on empirical understanding of bone drilling, an experimentally-validated thermo-mechanical model of bone and cartilage drilling does not exist. Furthermore, only limited attention has been devoted to design of special drilling geometries for optimized bone drilling.

The fundamental hypothesis of this proposal is that a comprehensive investigation including analysis, modeling, and experimentation of thermo-mechanical aspects of bone drilling can bring significant improvements to orthopedic surgeries, reducing unwanted complications such as thermal (osteonecrosis) or mechanical damage (cracks and cell death) to the bones. As mentioned above, considering the number of orthopedic surgeries performed every year, the proposed work will have a far-reaching impact to a significant portion of American and world population.

In this work, we aim to develop a thermo-mechanical model of the bone/cartilage drilling process, and to validate the model through experimentation on bovine bones and cartilage. The model can be used to determine forces, vibrations, and temperatures during the drilling process, as a function of the drill geometry, bone structure, and drilling conditions. This understanding can then be used to optimize the bone drilling process for a particular bone with given extent of osteoporosis; or to design more effective drill geometries and drilling conditions that minimize the unwanted effects of bone drilling. The ultimate goal is to improve the outcome of surgical procedures by reducing iatrogenic trauma and invasiveness of the procedure. The specific research objectives of this project include;