Antibiotic prophylaxis in allo-arthroplastic hip joint surgery. Concentration assays in the wound exudate after parenteral administration of gentamicin

Prophylaxis of acute osteomyelitis with absorbable ofloxacin-impregnated beads

We investigated the use of an ofloxacin-impregnated bioabsorbable composite for the prevention of acute Staphylococcus aureus osteomyelitis. New Zealand White rabbits were anesthetized, the femur was exposed, and a cortical hole was drilled. Animals were randomly given drug-free composites or ofloxacin-impregnated composites; the composites were placed at the site of injury, and the incision was closed. One hour later, all animals were intravenously inoculated with 5 x 10(4) CFU of S. aureus and observed for 28 days. Bone culture data revealed that S. aureus was isolated from 3 of 12 rabbits in the ofloxacin composite group and 9 of 11 animals in the control group (P = 0.02). Radiographic evaluation revealed that the drug-free group had a significantly (P = 0.01) greater degree of radiographic evidence of infection than the group given ofloxacin composites. Although a limited number of histologic samples were available, these data also paralleled the radiographic and culture data. This study demonstrates the effectiveness of the implantable ofloxacin bioabsorbable composites to prevent the development of acute osteomyelitis.

Pharmacokinetics of topical gentamicin in total hip arthroplasty

Two different ways of administering topical gentamicin were examined in patients undergoing total hip arthroplasty. 160 mg gentamicin, dissolved in isotonic saline, was instilled into the wounds of five out of ten patients. In the other five patients, the components of the prostheses were inserted by means of gentamicin-containing cement, 0.5 g per 40 g powder. Both the serum concentrations and the wound concentrations of gentamicin were determined constantly during the postoperative period. The average half-lives of gentamicin in the surgical wounds of the two groups of patients were found to be 3 1/2 and 25h, respectively. The average wound concentration was found to be higher than the minimum inhibitory concentration for staphylococci and aerobic Gram-negative rods for 18 and 11 h, respectively, in the group of patients treated with gentamicin solution compared with 160 and 67 h, respectively, in the group treated with the gentamicin-containing cement.

Antibiotics and bone cements. Experimental and clinical long-term observations

Comparing several antibiotics and different bone cements, the mixture of Palacos R (polymethylmethacrylate, PMMA) with gentamicin proved to be the most suitable one as far as a high and sustained release of the antibiotic from the artificial resin is concerned. A continuous leaching of gentamicin was observed for more than 5 years. Gentamicin proved to be stable in Palacos R for the whole period of time. The release of 12 antibiotics from Palacos R was evaluated in vitro. Four other bone cements were included in this study as well, in order to evaluate the leaching of gentamicin from these materials. The combination Gentamicin-Palacos R (GP) showed a 2--3 fold higher and much more prolonged release than did the other mixtures. From this investigation, which also included studies of commercially available antibiotic bone cement mixtures, it is quite obvious that there exist distinct differences in the various bone cements as well as in the various antibiotics as regards their qualification for use in alloarthroplasty. Pharmacokinetic studies in patients after implantation of GP showed low gentamicin concentrations in serum (on average 1.8 microgram/ml) and urine. However, in wound exudate, derived directly from the vicinity of the implanted cement, gentamicin concentrations up to 150 micrograms/ml were observed. Also in tissue samples from the vicinity of the implant, high concentrations were measurable for a long period of time (up to 5 1/2 years).