| Summary: | 碩士 === 長庚大學 === 醫療機電工程研究所 === 98 === Antibiotic-loaded acrylic bone cement is a well-established tool in the treatment of orthopedic infections. Numerous studies about its pharmacokinetic properties have demonstrated that only a small part of the incorporated antibiotic amounts can be released. Therefore, in the past 10 years, several attempts have been made for enhancement of the drug elution from bone cement. The precise mechanism by which antibiotics is released from cement is unknown. However, all literatures have demonstrated that elution process appears that the antibiotic is released from the superficial regions of the cement. Studies that tested the elution of antibiotic from pieces of cement have indicated that residual antibiotic is present in increasing concentrations from the outer surface of the cement to the center. To improve the efficiency of antibiotic elution, the increase of the superficial regions of the cement was thought to be an effective method.
Based on the above concept, the traditional use of antibiotic-loaded cement is made with beads shape for local antibiotic therapy during the interval between the first and second stag. Although cement beads have proven to be effective in curing the infection, however, the compromising result is the loss of mechanical strength during the interval between the first and second stage. Studies has shown that more voids would present at the surface with a cooler environment temperature when cement cures with a temperature gradient, which implies that cement cures at a lower environment temperature might cause a rough surface and might be beneficial for the release of antibiotic. However, literatures addressing the influence of environment temperature during cement curing on the elution characteristic of antibiotic-loaded cement are lacking. Besides, the process of manufacture of the antibiotic-loaded cement is performed intraoperatively based on patients’ specific condition. It often causes an inconvenient situation due to the limit of operation time. It will be beneficial for surgeon at operation if the antibiotic-loaded cement can be stored and utilized without loss of antibiotic elution. However, there are little literatures exploring the effect of storage duration on the elution characteristic of antibiotic-loaded cement.
Based on the above-mentioned background, this study used vancomycin and surgical grade PMMA bone cement to investigate the following two factors which were concerned to influence the elution characteristic of the vancomycin-loaded cement: (1). the environment temperature during cement curing; and (2). the storage duration of the antibiotic-loaded cement. For investigation of factor regarding the environment temperature, vancomycin-loaded cements were divided into three groups according to different levels of environment temperature: high- (50℃), medium- (25℃) and low- （0℃） environment temperature. Each vancomycin-loaded cement made from specific environment temperature was immersed in a glass tube containing sterile phosphate buffer solution and kept at 37℃ until the designed sampling times. Samples were taken at 1, 3, 6, 10, 24, 48, 72, 168 and 336 hours for vancomycin elution test. For investigation of the factor regarding the storage duration, vancomycin-loaded cements were divided into three groups, 1, 3, 5, 8 and 12 weeks, according to different storage durations. Samples were stored in a glass tube and kept at room temperature until the designed storage durations. Following the storage of designed durations, samples were taken for vancomycin elution test.
Microscopic observation revealed that highest concentration of voids was found for cement curing with low environment temperature. The result from elution test also indicated that the group with low environment temperature exhibited the highest amount of released vancomycin as compared to the other two groups; whereas no significant difference was found between medium- and high- environment temperature groups. Furthermore, for the investigation of the effect of storage duration, the result indicated that the group with shortest storage duration exhibited the highest amount of released vancomycin, which implied that the increase of storage duration might cause a loss of vancomycin elution.
We concluded that vancomycin-loaded cement curing with a low environment temperature enhances vancomycin elution. However, long storage duration of vancomycin-loaded cement cause a degradation of vancomycin elution.
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