A bone filling composition includes a bone filler. The bone filler includes microparticles of at least one elastomeric material. The at least one elastomeric material includes a poly(glycerol sebacate)-based thermoset. The poly(glycerol sebacate)-based thermoset may be porous thermoset poly(glycerol sebacate) flour, thermoset poly(glycerol sebacate) microspheres, or a combination thereof. In some embodiments, the bone filling composition is a bone filling composite that further includes a carrier material including a poly(glycerol sebacate) resin. A method of forming a bone filling composite includes selecting a bone filler and mixing the bone filler with a carrier material to form the bone filling composite. A method of treating a bony defect includes molding a bone filling composite and placing the bone filling composite in the bony defect. The bone filling composite includes a bone filler mixed with a carrier material.