[Translated article] In vitro elution of local anaesthetics from PMMA bone cement

Background and aim Currently, we do not have a gold standard for pain management after total knee arthroplasty. We may use one of more drug delivery systems, none of which are ideal. An ideal depot delivery system would provide therapeutic, nontoxic, doses of drug at the surgical side, especially during 72 h postoperatively. The bone cement used in arthroplasties has been used as a drug delivery system, especially antibiotics, since 1970. Based on this principle, we developed this study with the aim to characterize the elution profile of two local anaesthetics (lidocaine hydrochloride and bupivacaine hydrochloride) from PMMA (polymethilmethacrylate) bone cement. Material and methods Palacos® R + G bone cement and lidocaine hydrochloride or bupivacaine hydrochloride specimens were obtained depending on the study group. These specimens were immersed in PBS (phosphate buffered saline) and removed from the solution at different set times. Subsequently, the concentration of local anesthetic in the liquid was analyzed by liquid chromatography. Results The percentage of lidocaine eluted from PMMA bone cement in this study was 9.74% of the total lidocaine content per specimen at 72 h and 18.73% at 336 h (14 days). In case of bupivacaine, the elution percentage was 2.71% of the total bupivacaine content per specimen at 72 h and 2.70% at 336 h (14 days). Conclusions Local anesthetics elute in vitro from PMMA bone cement, reaching doses at 72 h close to the doses used in anesthetic blocks.