UBC Theses and Dissertations

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UBC Theses and Dissertations

Effect of bracing and navigation display design on targeting accuracy and plunge depth during surgical drilling McIvor, Jacob Donald


The success of many orthopaedic procedures relies on the accurate and timely machining of bone, which can be difficult to achieve. Errors during machining can negatively affect implant placement or cause neurovascular injury. Bracing can improve the performance of both humans and machines during a variety of interactive tasks such as writing and grinding. The purpose of this thesis was to assess the feasibility of braced computer assisted orthopaedic surgery by testing the influence of bracing on the performance of a surgically relevant task. We developed a computer assisted orthopaedic surgery research system and experimental bracing devices for two surgical drilling tasks: navigated targeting and cortical drilling. The performance of each device was tested in a user study with 25 (13 male, 12 female) non-expert subjects. In the navigated targeting task, subjects aligned a drill bit with a randomly generated trajectory while using a rigid brace to support the forearm and two different versions of guidance displays to provide visual feedback: a 2D axial display and a 3D-perspective display. Bracing reduced variation within- and between-trials, but did not affect final accuracy or targeting speed. There was a significant increase in final radial (170 %, 95% CI: 140–210 %) and angular error (350 %, 95% CI: 300–400 %) with the 3D-perspective display. In the cortical drilling task, subjects attempted to minimize plunge of the drill bit after breakthrough. An experimental damper-based bracing device was designed by developing a numerical model to predict drill plunge, extending the model to predict the behaviour with bracing, and estimating an optimal brace damping range. Subjects drilled through oak workpieces using a standard high speed steel drill bit and a brad point drill bit at 4 damping levels. At a level of 10Ns/mm, there was a significant decrease in plunge depth of 74% (95% CI: 71–76 %) and no significant difference in drilling duration. This thesis provides experimental evidence that a simple bracing strategy can improve the performance of a clinically relevant task; Applying bracing to computer assisted orthopaedic surgery may be an effective way to improve performance and warrants further investigation.

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