Bone bonding ability of a new biodegradable composite for internal fixation of bone fractures

Hydroxyapatite particles and poly(L-lactide) composites for internal fixati on of bone fractures have been developed based on the hypothesis that incor poration of hydroxyapatite particles in a poly(L-lactide) matrix might enha nce bone bonding. This study evaluated the bone bonding ability of these bi odegradable composites. Two types of hydroxyapatite and poly(L-lactide) com posite were used in this study: calcined hydroxyapatite/poly(L-lactide) and uncalcined hydroxyapatite/poly(L-lactide),Rectangular plates (2 x 10 X 15 mm) of each composite or poly(L-lactide) were implanted into the metaphysis of the tibiae of 33 male rabbits, and the failure load was measured by con ducting a detaching test 8, 16, and 25 weeks after implantation. The failur e loads of calcined hydroxyapatite/poly(L-lactide), uncalcined hydroxyapati te/poly(L-lactide), and poly(L-lactide), respectively, were 13.60, 13.95, a nd 0.46 N at 8 weeks; 29.84, 24.09, and 2.86 N at 16 weeks; and 25.50, 29.6 7, and 2.43 N at 25 weeks. Histologic observation revealed that the composi tes formed direct contact with the bone. The results in this study indicate that the composites improved the strength of the interface between bone an d plate. This improved interfacial strength lead to a substantial decrease in the frequency of implant loosening in the treatment of fractured bones b y internal fixation.