A Multi-physics Planning Paradigm for Robot Assisted Orthopaedic Surgery

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Johns Hopkins University
Osteoporosis or severe reduction in bone mineral density is a disease that primarily affects elderly people. Osteoporotic hip fracture rates increase exponentially with age in both men and women. In addition to the high mortality rate for those sustaining such fractures, less than half of the survivors return to their pre-fracture status concerning the quality of daily living. Augmentation of the proximal femur with Polymethylmethacrylate (PMMA) bone cement (femoroplasty) has been identified as a potential preventive approach to reduce the risk of fracture. Femoroplasty, however, is associated with a risk of thermal damage as well as the leakage of cement or blockage of blood supply when large volumes of PMMA are introduced inside the bone. Several recent studies have proposed injection strategies to reduce the injection volume in simulations. This thesis describes the methods and tools developed for multi-physics planning and the execution of femoroplasty. To this end, computational models are developed to simulate how bone augmentation affects the biomechanical properties of the bone. These models are used to plan femoropasty for cadaveric specimens and showed the superiority of planned-based augmentation over generic injection strategies. Experimental tests confirmed the findings of simulations and showed a significant increase in fracture-related biomechanical properties of the augmented compared to those left intact. In addition to biomechanical studies for femoroplasty, a heat-transfer model was developed to estimate bone temperatures during augmentation. Furthermore, a curved injection strategy was introduced and validated in simulations. These developments and modeling capabilities can be extended to various augmentation surgeries including vertebroplasty and core decompression.
pre-operative planning, femoroplasty, computer-assisted interventions. orthopaedic surgery