UBC Theses and Dissertations

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UBC Theses and Dissertations

Tool bracing for performance improvement in simulated femoral head-neck osteochondroplasty Kooyman, Jeremy James Robert


Bracing is defined as a parallel mechanical link between a tool user, the environment, and/or the workpiece that alters the mechanical impedance between the tool and workpiece with the goal of improving task performance. Bracing is used in a variety of settings including robotics/automation and more recently in medicine/dentistry, however it remains relatively understudied in formal ways. This thesis explored whether bracing could be beneficial in a current orthopaedic problem. We selected a candidate orthopaedic procedure based on selection criteria that included three degrees of freedom, and the ability to abstract/simulate the surgical task using phantom tests. Femoral head-neck osteochondroplasty is used to treat a deformity of the anterosuperior femoral head-neck region called cam-type femoroacetabular impingement. During this procedure a surgeon uses a spherical burr to remove the cam lesion and restore the normal contour of the femoral head-neck. The goal of this thesis was to evaluate whether a proposed bracing technique could enable a user to perform a cam resection more accurately and quickly than a currently employed arthroscopic technique. We first performed a pilot study with 4 subjects to examine the impact of bracing on simulated bone milling and found that bracing could reduce errors on the order of 7-14% and procedure length on the order of 30-50% but these findings were limited by a small sample and effect size. Workspace issues with the brace indicated the need for a redesign, which we combined with the creation of a higher fidelity surgical simulation. We showed that the most effective brace design projected a remote center of motion combined with a spring for axial stiffness. This improved brace design was tested using 20 non-surgeons and 5 surgeons. While bracing had no detectable effect on the surgeon population, bracing reduced procedure length and error by 37% and 27% respectively in the non-surgeon population when compared to the unbraced condition. Unfortunately, when compared to the surgical simulation condition, there was no detectable effect of bracing. This finding suggests that an optimal level of bracing may exist but how to experimentally determine this level remains a topic for future study.

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