ANALYSIS OF A BIODEGRADABLE COMPOSITE FOR BONE HEALING

A degradable L-PLA/calcium carbonate composite made of interconnecting phases was examined. This structure was used both to slow the degrada tion rate and to reduce the brittleness of the ceramic. Both in vitro and in vivo degradation studies were performed. Samples were incubated in buffered saline or placed in the dorsum of rats for 0, 1, or 4 wee ks. Mechanical testing was performed on both groups, volume fraction o f each component was determined for in vitro samples, and histology wa s performed on in vivo samples. Failure load, tensile strength, and el astic modulus significantly decreased during the Ist week for both gro ups. Continued decreases were seen at 4 weeks for in vitro samples but not for in vivo. Failure strain and tensile strength decreased only f or in vitro specimens. PLA fraction significantly decreased during the Ist week and then stabilized. Histology showed that tissue ingrowth o ccurred at 4 weeks. The decrease in mechanical properties was probably a result of the decreased PLA fraction. The stabilization and even a slight increase in tensile strength and failure strain in the in vivo samples was probably due to the tissue ingrowth forming an implant-tis sue composite. (C) 1996 John Wiley & Sons, inc.