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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Holographic interferometry in the biomechanical analysis of loading patterns in the human femur

Author: KATZ, David

Year: 1992

Supervisor(s): Julia Shelton

The technique of holographic interferometry was applied in the evaluation of loading patterns in the human femur both in the natural form and after the introduction of various femoral components of total hip replacement.
A loading frame was designed and constructed and its stiffness was chosen to minimise the susceptibility of holographic interferometry to the influence of rigid body motions. Reproducibility of fringe patterns was investigated and maintained by averaging the fringe deflections obtained on consecutive interferograms. Quantification of the fringe patterns was performed by recording the deflecting shape of the femur along its long axis, as viewed from each of the anterior, posterior, medial and lateral aspects. After subtracting the effects of rigid body motion, the deflection curves were differentiated twice to investigate the curvature of the femur, and the curvature was shown to be related to the longitudinal strain pattern. Results showed that the curvature of the femur, and changes in the curvature as a result of the introduction of a femoral prosthesis, compared well with previous strain gauge and finite element studies.

The study made use of a composite model of the femur which proved to be a useful substitute for the cadaveric femur. In addition, results supported the use of the whole femur in biomechanical analysis. Initial results of testing different implants showed that a reduction of curvature in the proximal femur, of between 45 and 90%, implying stress protection. There was no significant difference in the performance of the different implants. Results indicate that it may be possible to assess stability and micromotion of an implant/femur system using scatter biomechanical load data.