An internal fixation device and a bioerodible implantable material useful therefor comprise a bioerodible polymer that produces acidic products or low molecular weight resorbable fragments upon hydrolytic degradation, and a buffering or neutralizing agent in sufficiently high concentration to moderate the rate of change of pH of said bioerodible material during bioerosion. The buffering or neutralizing agent acts to reduce the inflammatory foreign body response generated by the acidic products and reduces the sterile abscess condition that occurs at the site of the bioerodible implant materials of the prior art. Internal fixation devices (IFDs) according to the invention are useful, for example, for the repair, replacement or reconstruction of damaged bone in any area of the body.