Composites of poly(DL‐lactide‐co‐glycolide) and calcium carbonate: In vitro evaluation for use in orthopedic applications

Abstract

Biodegradable materials utilized in current orthopedic sports medicine fixation devices are required to maintain mechanical properties for at least 12 weeks to facilitate tissue healing and then ideally degrade with eventual replacement by surrounding tissue (bone). Current materials exhibit excessive longevity, which limit the potential for bone replacement, an ideal outcome in clinical procedures where revisions are a possibility. This study investigates material property modification of poly(DL-lactide-co-glycolide) (PLGA) by calcium carbonate. Modification of the degradation rate of PLGA by calcium carbonate (16, 36, 51% w/w) was demonstrated and the percentage of calcium carbonate within the polymer optimized at 36% (w/w). The optimized formulation was molded into a fixation screw and in vitro degradation demonstrated a gradual loss in molecular weight but with a pull-out strength retention beyond 12 weeks. Significant mass loss then occurred after 26 weeks. Physical testing, insertion torque, and failure torque indicated that this composite also had sufficient initial mechanical properties required for screw in type fixation devices. The combination of mechanical properties and degradation behavior suggests that this material may have potential to be utilized in orthopedic fixation devices that are placed in bone.