UBC Theses and Dissertations

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UBC Theses and Dissertations

LaserGauge : development of a device for automatic measurement of bore depth in bone during surgery Demsey, Daniel


Purpose: This thesis comprised two main phases. Initial work focused on clarifying the need and use case for a novel device to measure drilled bore depth in bone during osteosynthesis surgery. Next, I demonstrated the feasibility and reliability of an optical sensing device for automatic measurement of drilled bore depth in bone during surgery compared with conventional methods. Methods: I completed a structured Needs Assessment followed by an Engineering Design process to develop a series of prototypes using laser displacement sensors mounted on a surgical drill to determine drilled bore depth in bone. In all versions of the prototypes bore depth was computed based on a characteristic pattern of drilling velocity in bicortical bone. Prototypes consisted of one or more laser displacement sensors sending displacement and time data to a microprocessor and then a personal computer. After data filtering with a second order Butterworth filter velocity and acceleration were calculated using differentiation and double differentiation. Characteristic spikes in velocity and acceleration indicated cortical breach and allowed identification of bore depth. Exploratory experiments were done with multiple sensor arrangement concepts in porcine long bones, and more rigorous final evaluation experiments were done with the lead designs in pig hind limbs with comparison to CT scan as ‘gold standard’. Results: In exploratory experiments a design involving two laser displacement sensors angled towards the drilling axis measuring distance from a mock drill guide performed better than alternative designs. This design in final evaluation experiments showed superior performance to the conventional depth gauge under three clinically relevant drilling conditions (standard deviation 0.70 mm vs. 1.38 mm, 0.86 mm vs. 3.79 mm, 0.80 mm vs. 3.19 mm). A positive bias was present in all drilling conditions. Conclusions: An optical sensing device can be used to measure bore depth in bone during surgery.

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