INTERFACE STRENGTH STUDIES OF CALCIUM-PHOSPHATE CERAMIC COATED STRAIN-GAUGES

In vivo strain gauging has been used to understand physiological loadi ng and bone remodeling In early studies, a cyanoacrylate adhesive was used to bond gauges to bone, even though this adhesive is susceptible to biodegradation that results in rapid debonding. Calcium phosphate c eramic (CPC) coated gauges have been successfully bonded to bone for l ong periods. However, earlier studies noted occasional debonding of co atings from gauges. The goals of this project were to develop a techni que to securely bond particles to gauge backings and develop an in vit ro test and assess its accuracy in simulating in vivo degradation of t his interface. Gauges were heated for different time intervals, roughe ned with carbide papers, and prepared using layered coatings of polysu lfone and CPC particles that varied in size, shape, and crystallinity. They were soaked in solution or placed in muscle pouches of rats for up to 16 weeks. They were then epoxied to fixtures, mounted on an MTS machine, and loaded to failure. Heating and roughening gauge surfaces increased the interface strengths by up to 2000%. In vivo and irt vitr o testing showed an initial drop in the interface strength, which leve led off to approximately 7.0 +/- 2.0 MPa. (C) 1998 John Wiley & Sons, Inc.