In vitro microbial inhibition and cellular response to novel biodegradable composite wound dressings with controlled release of antibiotics.

About 70% of all people with severe burns die from related infections, despite advances in treatment regimens and the best efforts of nurses and doctors. Although silver-eluting wound dressings are available for addressing this problem, there is growing evidence of the deleterious effects of such dressings in delaying the healing process owing to cellular toxicity. A new concept of antibiotic-eluting composite wound dressings is described here. These dressings are based on a polyglyconate mesh coated with a porous poly-(dl-lactic-co-glycolic acid) matrix loaded with antibiotic drugs. The effect of antibiotic release on bacterial inhibition was studied, and cell cytotoxicity was examined. The dressings resulted in a 99.99% decrease in the viable counts of Pseudomonas aeruginosa and Staphylococcus albus at very high initial inoculations of 107-108 CFU ml⁻¹ after only 1 day, while such a decrease in Staphylococcus aureus was obtained within 3 days. Bacterial inhibition zones around the dressing material were found to persist for 2 weeks, indicating a long-lasting antimicrobial effect. Despite severe toxicity to bacteria, the dressing material was found to have no toxic effect on cultured fibroblasts, indicating that the new antibiotic-eluting wound dressings represent an effective option for selective treatment of bacterial infections.

A novel quantitative approach for evaluating contact mechanics of meniscal replacements.

One of the functions of the meniscus is to distribute contact forces over the articular surfaces by increasing the joint contact areas. It is widely accepted that total/partial loss of the meniscus increases the risk of joint degeneration. A short-term method for evaluating whether degenerative arthritis can be prevented or not would be to determine if the peak pressure and contact area coverage of the tibial plateau (TP) in the knee are restored at the time of implantation. Although several published studies already utilized TP contact pressure measurements as an indicator for biomechanical performance of allograft menisci, there is a paucity of a quantitative method for evaluation of these parameters in situ with a single effective parameter. In the present study, we developed such a method and used it to assess the load distribution ability of various meniscal implant configurations in human cadaveric knees (n=3). Contact pressures under the intact meniscus were measured under compression (1200 N, 0 deg flexion). Next, total meniscectomy was performed and the protocol was repeated with meniscal implants. Resultant pressure maps were evaluated for the peak pressure value, total contact area, and its distribution pattern, all with respect to the natural meniscus output. Two other measures--implant-dislocation and implant-impingement on the ligaments--were also considered. If any of these occurred, the score was zeroed. The total implant score was based on an adjusted calculation of the aforementioned measures, where the natural meniscus score was always 100. Laboratory experiments demonstrated a good correlation between qualitative and quantitative evaluations of the same pressure map outputs, especially in cases where there were contradicting indications between different parameters. Overall, the proposed approach provides a novel, validated method for quantitative assessment of the biomechanical performance of meniscal implants, which can be used in various applications ranging from bench testing of design (geometry and material of an implant) to correct implant sizing.