New multifunctional anti-osteolytic releasing bioabsorbable implant

Bioabsorbable devices are a good alternative to metals for bone fixation because of their temporary presence in the body. However, bioabsorbable implants elicit a local foreign-body reaction that may lead to osteolysis. The aim of the current study was to develop and characterize a bioabsorbable implant with anti-osteolytic properties. Poly(lactide-co-glycolide) (PLGA) 80/20, was compounded with clodronic acid disodium salt (CS) to produce rods that were subsequently self-reinforced (SR) and gamma-sterilized. Four different implant types were investigated: 1) PLGA+CS, 2) SR-PLGA+CS, 3) sterilized (s)SR-PLGA+CS, and 4) sSR-PLGA. Drug release was determined using ultraviolet spectrophotometry. Shear strength, bending strength, and Young's modulus in bending were studied for 12 weeks in vitro, and changes in pH of the solution were also evaluated. A burst drug release was detected at the start. Approximately 70% of the drug was released during 10 weeks from SR rods and only 3% from the compounded rods during 12 weeks. gamma-sterilization also accelerated drug release. During the first 6 weeks, CS releasing rods had lower initial mechanical properties than plain rods, whereas they had higher values at 12 weeks because of the more steady and linear strength loss of CS rods. The pH of plain rods leads to a fall in pH at 8 to 12 weeks. A very slight drop in pH was seen with CS rods. In conclusion, it is feasible to develop clodronate-releasing, bioabsorbable PLGA implants that have acceptable mechanical properties. Rods retained suitable mechanical properties for fixation for 6 weeks in vitro. CS rods also prevent a drop in pH in vitro. In vivo studies are needed to evaluate their functionality with the view of clinical application in future.