In vitro and in vivo studies on devices of poly(l-co-d,l lactic acid)-co-TMC for bone repair

Abstract

The use of polymeric bioresorbable type devices as fracture repairs is becoming increasingly common, in part due to the great advantages that they present compared with metal implants in not requiring a second surgery for removal. Pins of poly(l-co-d,l lactide-co-trimethylene carbonate acid), PLDLA-TMC containing 30% TMC were obtained and characterized by in vitro and in vivo study, targeting them for use as fracture devices. Pins 2.5 mm in diameter were obtained by melting the polymer and immersing it in phosphate buffer, pH 7.4 at 37 °C to study the in vitro degradation, in addition to being implanted in the tibia of Wistar rats to assess the bone formation after 15, 60, 90, 120, and 150 days. The results from this study showed that for PLDLA-TMC pins, the thermal, mechanical, and morphological properties remained essentially unchanged after 90 days, particularly the glass transition temperature, Young’s modulus, maximum stress in stretching, and mass loss, in spite of the sharp change in molar mass at the beginning of the degradation process. These results corroborate the in vivo study, which showed the occurrence of bone formation in the early days, especially at 60 and 90 days, and the implant group, in general, presented a more mature and organized bone formation, with less fibrosis than the control group. This set of results indicates that the material has the potential to be applied as a device for the recovery of bone lesions in situations where the permanence of the implant over a long period is essential.