New method for antibiotic release from bone cement (polymethylmethacrylate): Redefining boundaries. / Nuevo método de liberación de antibióticos del cemento óseo (polimetilmetacrilato): redefiniendo los límites.

INTRODUCTION: The increasing antimicrobial resistance is promoting the addition of antibiotics with high antistaphylococcal activity to polymethylmethacrylate (PMMA), for use in cement spacers in periprosthetic joint infection. Linezolid and levofloxacin have already been used in in-vitro studies, however, rifampicin has been shown to have a deleterious effect on the mechanical properties of PMMA, because it inhibits PMMA polymerization. The objective of our study was to isolate the rifampicin during the polymerization process using microencapsulation techniques, in order to obtain a PMMA suitable for manufacturing bone cement spacers. MATERIAL AND METHOD: Microcapsules of rifampicin were synthesized with alginate and PHBV, using Rifaldin®. The concentration levels of rifampicin were studied by UV-visible spectrophotometry. Compression, hardness and setting time tests were performed with CMW®1 cement samples alone, with non-encapsulated rifampicin and with alginate or PHBV microcapsules. RESULTS: The production yield, efficiency and microencapsulation yield were greater with alginate (P = .0001). The cement with microcapsules demonstrated greater resistance to compression than the cement with rifampicin (91.26±5.13, 91.35±6.29 and 74.04±3.57 MPa in alginate, PHBV and rifampicin, respectively) (P = .0001). The setting time reduced, and the hardness curve of the cement with alginate microcapsules was similar to that of the control. DISCUSSION AND CONCLUSIONS: Microencapsulation with alginate is an appropriate technique for introducing rifampicin into PMMA, preserving compression properties and setting time. This could allow intraoperative manufacturing of bone cement spacers that release rifampicin for the treatment of periprosthetic joint infection.

Experimental tracheal revascularization with omentum.

We assessed omental revascularization of heterotopic tracheal implants in rats, and investigated the influence of factors that can enhance revascularization. The trachea of the donor animal was excised in two parts, and each tracheal allograft was implanted in the omentum of two recipients. The influence of mechanical factors was evaluated by applying traction at both ends of the graft with and without drainage of the tracheal lumen, and the influence of pharmacologic factors by giving cefonicid, hydrocortisone, cefonicid plus hydrocortisone, or cyclosporine and azathioprine during the postoperative period. Revascularization of the graft from the omentum with preservation of the tracheal structure was established. Graft viability showed significant differences between the tracheal implants to which no traction had been applied and those with traction at both ends. Tracheal allografts from animals receiving immunosuppressants were completely viable and no significant differences were found between the controls and animals in this group.