Pins composed of poly(L-lactic acid)/poly(3- hydroxybutyrate-co-hydroxyvalerate) PLLA/PHBV blends: Degradation in vitro.

Bioabsorbable polymers have shown good clinical success in the fixation and stabilization of bone fractures. Understanding and controlling polymer prosthetic degradation and the effect of the degradation products in vivo are crucial for successful implant developments. In this study, pins made from blends of PLLA/PHBV of varying compositions were degraded in phosphate buffer and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). The PLLA/PHBV blends were found to be immiscible. PLLA began to degrade after approximately 12 weeks, whereas PHBV showed some degradation only after 53 weeks. The crystallinity of the blends increased with degradation. In conclusion, PHBV improved the thermal properties of PLLA and reduced the brittleness of the blends tested. The 40/60 PLLA/PHBV blend had the best properties for use in orthopedics since it degraded quicker than pure PHBV, and yet maintained its crystallinity for longer than PLLA; in addition, this blend did not have the brittleness of PLLA. (Journal of Applied Biomaterials and Biomechanics 2005; 3: 50-60).