Controlled laser ablation of polymethyl methacrylate bone cement

The increasing numbers of re-operations carried out on total hip replacement patients causes considerable difficulty for orthopaedic surgeons. One particular problem lies in the removal of the bone cement inserted during the primary operation without causing damage to the bone. In order to develop a method for differentiating between polymethyl methacrylate (PMMA) bone cement and bone during laser ablation, the laser-induced fluorescence from PMMA has been studied and compared to that from the bone. An Oriel multispec spectrometer was used to analyse and record the radiation emitted during 248-nm excimer laser ablation. There was high-intensity fluorescence from bone relative to that from PMMA and several peaks occurred in the spectrum of bone which were absent from that of PMMA. Monitoring of this emission has enabled controlled laser ablation of bone cement in contact with bone to be achieved in vitro with no damage to the naked eye.