Abstract/Details

The consequences of collagen degradation on bone mechanical properties

Wynnyckyj, Chrystia.   University of Toronto (Canada) ProQuest Dissertations & Theses,  2010. NR72345.

Abstract (summary)

The mechanisms underlying the effect of alterations in Type I collagen on bone mechanical properties are not well defined. Clinical tools for evaluating fracture risk, such as dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS) focus on bone mineral and cannot detect changes in the collagen matrix. The mechanical response tissue analyzer (MRTA) is a potential tool for evaluating fracture risk. Thus, the focus of this work was to investigate the effects of collagen degradation on bone mechanical properties and examine whether clinical tools can detect these changes.

Female and male emu tibiae were endocortically treated with 1 M potassium hydroxide (KOH) solution for 1-14 days and then either mechanically tested in three-point bending, fatigued to failure or fatigued to induce stiffness loss. Computed Tomography scans, DXA, QUS, MRTA and three-point bend testing in the elastic region were performed on emu tibiae before and after either KOH treatment or fatigue to induce stiffness loss. Fracture surfaces were examined to determine failure mechanisms. Bone mineral and bone collagen were characterized using appropriate techniques. Bone mineral-collagen interface was investigated using Raman spectroscopy and atomic force microscopy (AFM).

Endocortical KOH treatment does not affect bone mineral however, it causes in situ collagen degradation, rather than removal and may be weakening the mineral-collagen interface. These changes result in significantly compromised mechanical properties. Emu tibiae show significant decreases in failure stress and increased failure strain and toughness, with increasing KOH treatment time. The significant increase in toughness of KOH treated bones is due to structural alterations that enhance the ability of the microstructure to dissipate energy during the failure process, thereby slowing crack propagation, as shown by fracture surface analysis. KOH treated samples exhibit a lower fatigue resistance compared to untreated samples at high stresses only for both sexes. Partial fatigue testing results in similar decreases in modulus for all groups and sexes. The MRTA detected these changes whereas DXA and QUS did not. MRTA detects changes in bone mechanical properties induced by changes in collagen quality and fatigue and could be a more effective tool for predicting fracture risk.

Indexing (details)


Subject
Biomechanics;
Materials science
Classification
0648: Biomechanics
0794: Materials science
Identifier / keyword
Applied sciences; Biological sciences; Bone mechanical properties; Collagen degradation; Fracture risk; Potassium hydroxide
Title
The consequences of collagen degradation on bone mechanical properties
Author
Wynnyckyj, Chrystia
Number of pages
245
Degree date
2010
School code
0779
Source
DAI-B 72/07, Dissertation Abstracts International
ISBN
978-0-494-72345-6
University/institution
University of Toronto (Canada)
University location
Canada -- Ontario, CA
Degree
Ph.D.
Source type
Dissertation or Thesis
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
NR72345
ProQuest document ID
869990177
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
https://www.proquest.com/docview/869990177