Laser ablation of dyed acrylic bone cement

Revision surgery of cemented implants is indicated when mechanical failure causes severe pain and/or loss of function for the patient. Successful revision arthroplasty of cemented implants requires complete removal of the existing cement. Removal of old cement is an arduous task often causing damage to the surrounding bone tissue. In this study, the authors investigate the use of an Argon laser and the addition of dyes to enhance the laser ablation of bone cement. Methylene blue and red dye #13 were each added separately to polymethylmethacrylate (PMMA) bone cement powder. A continuous wave Argon ion laser (lambda = 514 nm) was used for cement ablation. Cement samples were ablated at different power levels (1.5, 2.3, and 3.0 W) and exposure times (30, 60, 90, 120 sec). The results show that the Argon laser was unable to ablate undyed PMMA. However, the addition of either methylene blue or red dye #13 greatly improved cement ablation by altering the cements' absorption characteristics. Results of Student's t-tests show a statistical difference between red and blue dyed PMMA mean ablation areas at all energy levels tested (P < .0002). As expected, all red ablation areas were greater than blue ablation areas at each energy level tested since red dye absorbs more energy at 514 nm than methylene blue dye. The results of this study suggest that by selectively altering the absorption characteristics of PMMA, laser removal of bone cement can be achieved. In addition, this study also shows that bone tissue does not absorb visible light energy at 514 nm, suggesting that bone cement may be removed with minimal damage to the surrounding bone tissue.