Biocompatibility of polyoxymethylene (Delrin) in bone

The bone tissue reaction to bulk polyoxymethylene (Delrin) was studied in eight adult albino rabbits followed for up to 5 months after insertion of implants into the tibial metaphyses. Each animal received two implants, one of pure Delrin, the other a 'mosaic' plug with alternating areas of commercially pure titanium and Delrin. At the passage through the cortex, a direct bone-Delrin contact was seen in more than half of the cases, but the contact was usually limited in extent. At the same time, in virtually all sections, a foreign-body reaction with macrophages and giant cells was prominent. It was concluded that bulk Delrin has inferior biocompatibility to titanium, and the advisability of using Delrin as a biomaterial for bone anchorage is questionable.