Relationships Among Stability, Bony Ingrowth, and Remodeling for a Porous Coated Hip Endoprosthesis

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URL: https://repository.upenn.edu/dissertations/AAI9308548

Abstract

The objective of this research was to uncover the interdependence between stability, remodeling, and bony ingrowth based on the design of our prosthesis. Three independent experiments were performed: 1) the determination of stability, in which the relative motion was measured between the implant and the cortex was measured at four different time periods up to one year; 2) "histomorphometric analyses" was performed to measure the remodeling (i.e. cortical thickness and trabecular density) and bony ingrowth after three months and one year of implantation; and 3) finite element analyses were used to determine the stress distribution as a function of bone tissue remodeling at the four distinct time periods. Additional analyses were performed to determine the stress concentration effect in cancellous bone in its natural state, and at the interface with the porous coating.

Extensive bony ingrowth was apparent at 3 months, and increased at 1 year. The trabecular bone adjacent to the prosthesis increased in density, at three months, while at one year there was marked proximal antero-medial cortical resorption.

Although all the prostheses were stable, a different factor was found to dominate the results at each of the time periods. At three weeks there was a statistically significant negative correlation with the endosteal canal fill; at 12 weeks there was a statistically significant negative correlation with bony ingrowth; and at one year there was a statistically significant correlation with proximal cortical bone loss.

The finite element analyses calculated a 75 % reduction in the stress intensity in the area of the most pronounced cortical resorption. A similar stress reduction was calculated by the models from three weeks and twelve weeks. The model from one year calculated an increase of stress in the antero-medial cortex as a result of the severe resorption.

The discrete models of trabecular bone calculate high peak stresses on the surface of the trabecula tissue. These peak stresses are much higher than predicted by the continuum assumption and approach the peak stresses in the cortex. These calculations support a single law governing stress induced remodeling.

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Cited By (1)

Year	Entry
1995	Marcolongo MS. Bioactive Glass Fiber/polymeric Composite as a Bone Bonding Biomaterial [PhD thesis]. Philadelphia, PA: University of Pennsylvania; 1995.