This dissertation presents contact force sensors that are based on an emerging fibre-optic
sensing technology, the in-fibre Bragg grating (FBG), for contact force measurements
between cartilage surfaces in the human hip. There are two main motivations for force
measurement in hips (and other joints). First, there is clinical evidence that suggests
excessive force magnitude and duration can cause painful degeneration of joints. Second,
insights from ex vivo force measurements during simulated physiologic loading are the
basis of the rationale for corrective surgeries meant to halt degeneration and restore
proper joint function by restoring natural joint mechanics. The current standard tools for
force measurements in joints are force/stress sensitive films.
There are problems associated with inserting these films into joints that affect the
force/stress measurements. To insert the films, the joint must be dissected of surrounding
soft tissues and, ultimately, the joint must be taken apart (disarticulated). Following
disarticulation, films are fixed to cartilage surfaces, and the joint is re-assembled so that
physiologic loads can be applied. The negative consequence of dissection and
disarticulation is that the natural mechanics of the intact joint are permanently lost and,
therefore, film measurements do not indicate the actual joint mechanics. Moreover,
covering cartilage surfaces with rigid films alters the natural contact mechanics of the
joint.
The force sensors presented in this dissertation are designed for local force
measurement over the region of the optical fibre containing the FBG and address
limitations of force/stress sensitive films. The FBG force sensors are extremely small
(major diameters ranging from 0.165 mm to 0.24 mm) and can be inserted into joint
spaces without dissection of soft tissues and disarticulation thereby allowing the joint to
remain intact. Theoretical and experimental results indicate that FBG sensor
measurements are less affected by the mechanical properties of cartilage than are film
sensors.
The sensors presented in this dissertation also address limitations with previous
FBG based force sensors and are the first application of FBGs in intact human hips. The
sensors are smaller, and therefore less invasive, and insensitive to orientation, axial strain
and temperature, unlike other FBG sensors presented in the literature. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3635 |
| Date | 19 October 2011 |
| Creators | Dennison, Christopher Raymond Stuart |
| Contributors | Wild, Peter Martin |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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