Investigation of the degradation and mechanical properties of bioabsorbable polyesters and their blends

This study concerns the development of new bioabsorbable polymer blends and their properties. The ability of a bioabsorbable polymer to retain its strength for a specific period of time is critical for fixation devices such as screws, pins, tacks and anchors. Also being able to add possible osteoconductive materials such as hydroxyapetite (HA) without impairing the properties of the polymer is advantageous. The data presented in this study shows that it is possible to increase the strength retention of Polyglyconate B (Maxon B) by blending it with Poly L Lactic Acid (PLLA) which has a longer strength retention time. The resulting blends had similar mechanical strength values at time zero. The length of time they retained their strength during in vitro conditioning depended on the blend ratio with the strength retention time increasing with the percentage of PLLA in the blend. The data in this study also showed that hydroxyapetite can be successfully blended with PLLA without decreasing its initial strength. At higher loading levels and at increased in vitro degradation time points HA acts as a reinforcement, increasing the mechanical strength of the bioabsorbable device vs. unfilled PLLA. Star shaped Maxon B polymers were also tested, but did not show any significant improvement over linear Maxon B in mechanical strength.