LASER-ABLATION OF DYED ACRYLIC BONE-CEMENT

Revision surgery of cemented implants is indicated when mechanical fai lure causes severe pain and/or loss of function for the patient. Succe ssful revision arthroplasty of cemented implants requires complete rem oval of the existing cement. Removal of old cement is an arduous task often causing damage to the surrounding bone tissue. In this study, th e authors investigate the use of an Argon laser and the addition of dy es to enhance the laser ablation of bone cement. Methylene blue and re d 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 differe nt 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 u ndyed PMMA. However, the addition of either methylene blue or red dye #13 greatly improved cement ablation by altering the cements' absorpti on characteristics. Results of Student's t-tests show a statistical di fference between red and blue dyed PMMA mean ablation areas at all ene rgy levels tested (P < .0002). As expected, all red ablation areas wer e greater than blue ablation areas at each energy level tested since r ed dye absorbs more energy at 514 nm than methylene blue dye. The resu lts 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 v isible light energy at 514 nm, suggesting that bone cement may be remo ved with minimal damage to the surrounding bone tissue. (C) 1997 Wiley -Liss, Inc.