Degradation behavior of composite pins made of tricalcium phosphate and poly(L,DL-lactide)

Combining a bioactive ceramic with a resorbable polymer may improve the bio compatibility and the osseointegration of degradable fracture fixation devi ces. This study reports on the mechanical properties and degradation behavi or of two composite pins made of poly(L,DL-lactide) and 10 and 30% beta -tr icalcium phosphate (TCP). respectively. The pins were compared to a pin mad e of 100% poly(L,DL-lactide). The failure force. bending strength. and mole cular weight were determined during in vitro degradation at 37 degreesC up to 78 weeks. The blending with 10 or 30% beta -TCP decreased the initial me chanical properties and led to an accelerated degradation rate. The pins wi th 30% TCP lost half of their strength after 16 weeks. i.e. faster than the unmodified pin (40 weeks). The pins with 10% TCP. however, showed a decrea sed initial strength (128 +/- 9 MPa) compared to the unmodified pin (152 +/ - 9 MPa) but very similar degradation characteristics. The drop of the mole cular weight was not significantly different between the three types of pin s. It was concluded that the mechanical requirements for a pin for the fixa tion of small bony fragments with improved biocompatibility were fulfilled by the composite pin with 10% TCP but not by the pin with 30% TCP.