[Antibiotic-loaded orthopedic cements. Pharmacokinetics and bone level]

Abstract

A mechanical study in the laboratory of 10 types of cement has shown that the characteristics of low viscosity antibiotic-loaded cements are comparable with those of standard cement without antibiotic and of standard viscosity. A study of the release of Gentamycin in 26 patients treated by total hip replacement showed that the concentration of antibiotic in the drainage fluid was much greater than the minimum inhibitory concentration whereas the low blood concentration gave no risk of ototoxicity or nephrotoxicity. This method of administration achieved antibiotic concentrations in the tissues in contact with the prosthesis 10 times greater than those obtained by injection. In sheep, the intra-osseous concentration was studied in 32 femora after insertion of low viscosity Gentamycin-loaded cement. The levels remained raised to 4 times the minimum inhibitory concentration for up to one year after operation, even with cements with a low concentration of antibiotic of 0.6 g/dose. The concentrations obtained in the drainage fluid, in the peri-prosthetic tissues and especially in bone, confirm the effectiveness and the prolonged action of antibiotic therapy by cement and its value in the revision of infected prostheses and in prophylaxis in primary surgery. This justifies the further study of combinations of cement with new antibiotics with a broader spectrum than Gentamycin since there is no concern with the cements currently in use that the mechanical quality is less than that of standard cement.