Bioactive Glass Fiber/polymeric Composite as a Bone Bonding Biomaterial

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URL: https://repository.upenn.edu/dissertations/AAI9543118

Abstract

We investigated the concept of a bioactive composite as a femoral hip implant material with the objective of providing both early and long-lasting fixation between the implant and bone tissue. Glass fibers were designed specifically for the application as a fixation vehicle for the composite femoral hip prosthesis. The flexible fibers were amorphous and the tensile strength of the glass fibers was ten times stronger than that of bulk bioactive glass.

In vitro surface reactions of the glass fibers resulted in the formation of hydroxycarbonate apatite, indicative of bioactivity in vno. When the fibers were combined with a polysulfone matrix to form a composite, the composite developed a calcium phosphate surface layer after immersion in a protein-free simulated body fluid. In a protein-containing simulated blood plasma solution, the kinetics of reaction layer formation were slowed, however, eventual formation of a calcium phosphate surface layer was achieved.

Bioactive glass fiber/polysulfone composites were implanted in the femoral cortex ofthe rabbit for six weeks. The interfacial bond strength between the implants and bone was significantly higher than that of all-polysulfone control implants and in the range of coatings which are used clinically. Histologically, bioactive glass fibers at the composite/bone tissue interface resorbed to varying degrees and were replaced by calcified tissue.

Finite element models of a femoral hip component in a femur were used to numerically analyze the contribution of degree of fixation and material modulus on cortical bone strains in the proximal medial region of the femur. Strain transfer to the proximal medial cortex was optimized using a low modulus composite material in combination with a proximal third, circumferential bond between the implant and bone. These results were consistent for the case of primary as well as revision hip arthroplasty.

We have shown that a bioactive glass fiber composite can provide fixation to bone tissue in a non-load bearing situation for early periods ofimplantation. Further, the strain patterns which could be achieved by combining a low modulus material with optimized degree of fixation may reduce the severity of adverse bone tissue remodeling about a femoral hip prosthesis.

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