Dec 3 – BME Seminar, Speakers: Jake McIvor & Mahkameh Lakzadeh

BME Seminar
Friday December 3, 8-9am
Blusson Pavilion Lecture Theatre

1st Speaker: Jake McIvor
Supervisor: Antony Hodgson

Title: Advanced Tools for Computer-Assisted Orthopedic Surgery:Towards Braced Surgical Instrumentation – Minimizing Penetration During Cortical Bone Drilling

The successful outcome of many orthopedic procedures relies on the accurate and timely machining of bone. Improper positioning can negatively affect implant placement or cause neurovascular injury. Achieving and maintaining the correct orientation is often difficult to achieve and time-consuming, particularly when the visual field is obstructed or when the anatomical structure being cut is not rigidly secured.  Large forces are required to cut efficiently, but cause stability which can affect accuracy.  Using smaller forces reduces the instability, but increases the time required to make the cut and generates excessive heat in the tissue which can cause ostenecrosis.

Navigation systems have been shown to improve accuracy when using mechanical guides attached to the bone, but these are relatively time-consuming to align and fix.  Freehand navigation is considerably faster, but less stable and less accurate.  We propose using a bracing strategy to achieve some of the accuracy benefits of pinned mechanical guides at a speed comparable to freehand drilling. We are currently applying the bracing concept to bicortical bone drilling, a common task in fracture repair.  The goal of this work is determine how well a bracing device can minimize the amount of penetration into soft tissue after cortical breakthrough.  We have developed a model of manual bicortical drilling in parallel with in vitro testing, and have extended the model to predict the behaviour with bracing.    In this talk, I will describe the findings of the in vitro pilot tests and the development of the manual and braced drilling models.

2nd Speaker: Mahkameh Lakzadeh
Supervisors:  Antony Hodgson and Dinesh K Pai

Title: A Geometrically Accurate, Tendon-Driven Eye Model for Evaluating Visuomotor Hypotheses

Our visual system does much more than just taking in visual information. Most importantly the eyes move towa therefore we only see what we want rather than the entire field of view, as a camera would. Eye movements are therefore a crucial part of human’s visual system. These movements are actuated by what appears to be a simple system of three agonist and antagonist muscle pairs. This implication of tractability has attracted many scientists and neurobiologists to the subject of eye movements over the years. We therefore know more about the neurology of eye movements than of any other human movements. However to realize whether our theories are plausible we must implement them on physical models. Here we present a novel, anatomically accurate model of the human eye. This is to be used as a test bed for implementing plausible scientific theories regarding the neural control of eye movements. This robotic eye rotates about 3 axes of rotation using flexible steel wires (representing extraocular tendons) driven by DC motors (representing muscle actuation). The globe’s natural orbital support i ion gimbal structure which supports the eye on the anteroposterior axis at the back of the globe, where there are no tendons passing. This model is appropriately scaled in accordance with the human eye dimensions and closely simulates the main mechanical behaviors of a biological eye.

In parallel with developing a 3D mechanical platform, we are developing the corresponding control algorithms required to control this 6 tendon redundant system. To date, we have implemented a controller  based on the forward kinematics of the system.

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