EPR study of free radicals in PMMA bone cement: a feasibility study

In order to determine the feasibility of using electron paramagnetic resonance (EPR) to monitor the molecular processes occurring in polymethylmethacrylate (PMMA) bone cement, a preliminary study has been conducted on the bone cement in vitro. It has been found that a sufficient concentration of free radicals is generated in the bone cement during the polymerization process so that both the polymerization and the curing can be monitored by EPR. The results of these measurements on both radiolucent and radiopaque Surgical SimplexR P bone cement are presented. It has also been found that free radicals are present in the radiopaque bone cement powder as received from the manufacturer. These radicals which apparently are produced in the radiation sterilization process have been found to be unaffected by the polymerization/curing process and to be stable for temperatures below about 100 degrees C. It has clearly been shown that EPR can used to monitor the molecular processes of bone cement in vitro. It is hoped that this technique can be utilized to monitor the in vivo ageing process of bone cement used to fix orthopedic implants.