Abstract
BackgroundAntibiotic-loaded bone cement, or antibiotic-impregnated polymethylmethacrylate (PMMA), were developed to prevent and treat bone and joint infections. Gentamicin is an antibiotic that is commonly used in combination with PMMA; however, gentamicin powder is hard to obtain in many countries. This study aimed to evaluate the elution characteristics of gentamicin-impregnated PMMA made with lyophilized liquid gentamicin, compared with PMMA; which is made from commercial gentamicin powder.MethodsThe experimental sample was divided into 2 groups: the gentamicin power group (PG-PMMA) and the lyophilized liquid gentamicin group (LG-PMMA). Ten cement spacers were prepared in each group. These were produced by mixing gentamicin powder, or lyophilized liquid gentamicin, with a powder polymer before adding the liquid monomer (2 g of gentamicin and 40 g of PMMA). The volume and surface area of the antibiotic-impregnated cement spacers were 50 cm3 and 110 cm2, respectively. Each spacer was immersed in phosphate-buffered saline, which was changed daily under sterile conditions. The solutions were collected to measure the level of gentamicin using the enzyme multiplied immunoassay technique (EMIT), at days 1, 2, 3, 4, 5, 6, 7, 14, 21, 28, 35 and 42.ResultsThe collections from both groups had high concentrations of gentamicin on day 1 (113.63 ± 23.42 mg/dL in LG-PMMA and 61.7 ±8.37 mg/dL in PG-PMMA), but experienced a continuous decrease over time. The PMMA spacers from both groups could release gentamicin for up to 6 weeks (3.28 ± 1.17 mg/dL in LG-PMMA and 1.21 ± 0.28 mg/dL in PG-PMMA). However, there were significantly higher levels of gentamicin concentrations in the LG-PMMA group compared to the PG-PMMA group at all time points (P< 0.05).ConclusionGentamicin-impregnated PMMA made with lyophilized liquid gentamicin had approximately a two times higher rate of antibiotic elution in preliminary in vitro studies, as compared with PMMA made with premixed gentamicin powder.
Highlights
Antibiotic-loaded bone cement, or antibiotic-impregnated polymethylmethacrylate (PMMA), were developed to prevent and treat bone and joint infections
The aim of this study was to evaluate the elution characteristics of gentamicin-impregnated PMMA made with lyophilized liquid gentamicin, as compared to that of PMMA made with commercial gentamicin powder; using the enzyme multiplied immunoassay technique (EMIT) [9]
The authors conducted this research to evaluate the elution characteristics of gentamicin-impregnated PMMA made with lyophilized liquid gentamicin, as compared with PMMA made with commercial gentamicin powder
Summary
Antibiotic-loaded bone cement, or antibiotic-impregnated polymethylmethacrylate (PMMA), were developed to prevent and treat bone and joint infections. If physicians require higher concentrations of gentamicin; when preparing handmade PMMA beads or articulating spacers, gentamicin in powder form is normally used for mixing with PMMA. The reason for this is that most of the available, commercial gentamicin-impregnated PMMA, contains only 0.5–1 g of gentamicin in batches of bone cement (40 g) [5]. As an example; if a physician wanted to add 2 g of gentamicin to 40 g of PMMA, the procedure requires 50 ml of liquid gentamicin [Gentamicin 80 mg/2 ml], so not all of the liquid gentamicin can be mixed with the liquid monomer and cement powder This is because the high volume of normal saline, which is solvent in liquid gentamicin, will dilute the liquid monomer and prevent the hardening of PMMA. This means that liquid gentamicin cannot be realistically used to produce highconcentrations gentamicin PMMA
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