Microencapsulation of rifampicin: A technique to preserve the mechanical properties of bone cement.

Two-stage exchange with antibiotic-loaded bone cement spacers remains the gold standard for chronic periprosthetic joint infection (PJI). Rifampicin is highly efficient on stationary-phase staphylococci in biofilm; however, its addition to PMMA to manufacture spacers prevents polymerization and reduces mechanical properties. Isolation of rifampicin during polymerization by microencapsulation could allow manufacturing rifampicin-loaded bone cement maintaining elution and mechanical properties. Microcapsules of rifampicin with alginate, polyhydroxybutyratehydroxyvalerate (PHBV), ethylcellulose and stearic acid (SA) were synthesized. Alginate and PHBV microcapsules were added to bone cement and elution, compression, bending, hardness, setting time and microbiological tests were performed. Repeated measures ANOVA and Bonferroni post-hoc test were performed, considering a p < 0.05 as statistical significance. Bone cement specimens containing alginate microcapsules eluted more rifampicin than PHBV microcapsules or non-encapsulated rifampicin over time (p < 0.012). Microencapsulation of rifampicin allowed PMMA to preserve mechanical properties in compression and bending tests. Cement with alginate microcapsules showed similar behavior in hardness tests to control cement over the study period (73 ± 1.68HD ). PMMA with alginate microcapsules exhibited the largest zones of inhibition in microbiological tests. Statistically significant differences in mean diameters of zones of inhibition between PMMA loaded with alginate-rifampicin (p = 0.0001) and alginate-PHBV microcapsules (p = 0.0001) were detected. Rifampicin microencapsulation with alginate is the best choice to introduce rifampicin in PMMA preserving mechanical properties, setting time, elution, and antimicrobial properties. The main applicability of this study is the opportunity for obtaining rifampicin-loaded PMMA by microencapsulation of rifampicin in alginate microparticles, achieving high doses of rifampicin in infected tissues, increasing the successful of PJI treatment. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:459-466, 2018.

Pilares de zirconia sobre implantes: comportamiento biomecánico / Zirconia implant abutments: biomechanical behaviour

La cerámica de óxido de aluminio (alúmina) se introdujo en 1993, pero el primer pilar totalmente cerámico fue introducido un año más tarde, en 1994, y consistía en alúmina altamente sinterizada (CerAdapt de Nobel Biocare). Sin embargo, el problema que presentaba este pilar fue su fragilidad. Con la introducción de los pilares de óxido de circonio (zirconia), se mejoraron las propiedades mecánicas y se ofrecieron nuevas oportunidades para las restauraciones. La zirconia desempeña un papel vital dentro de la biotecnología moderna debido a su carácter inerte y a sus excelentes propiedades mecánicas, como resistencia y dureza. Este pilar cerámico se fabrica a partir de zirconia estabilizada con itria (y-TZP), un material que está siendo utilizado en cirugía ortopé- dica desde hace más de 20 años. Sin embargo, la zirconia aún no lleva mucho tiempo en el campo de la odontología, por lo que no hay estudios a largo plazo de su comportamiento mecánico en boca. El objetivo general del trabajo, es estudiar la resistencia estática y a fatiga mediante ensayos in vitro de una muestra de probetas de pilares rectos de zirconia de diámetro estándar sobre implantes, confeccionadas según la normativa uNE-EN ISO 14801. Las conclusiones más destacadas del presente trabajo son las siguientes: todos los pilares fracturan por el cuello; todos los pilares se pueden usar en el sector anterior maxilar incluso a largo plazo; y, por último es necesario, que los estudios sobre aditamentos protésicos, se realicen mediante un protocolo establecido (norma uNE-EN ISO 14801), para que sea más fácil la comparativa entre ellos (AU)

The ceramic of aluminum oxide (Alumina) was first introduced in 1993, however, the first all-ceramic abutment was developed one year later in 1994, this abutment was made of alumina highly synthesized (CerAdapt by Nobel Biocare). however, the problem discovered on these abutments was its fragility. With the introduction of zirconium oxide abutments (zirconium), the mechanical properties were improved and new opportunities for restorations were developed. Zirconium plays an important role within modern biotechnology because of its inertness. In addition, it has excellent mechanical properties, such as strength and hardness. This ceramic abutment is made of yttria stabilized zirconia (yTZP), material that is being used in orthopaedic surgery for over 20 years. however, zirconium hasn´t been tested properly in the field of dentistry, so there is no long-term studies of their mechanical behaviour in the mouth. The aim of this work is to study the static and fatigue strength in vitro of zirconia straight abutments of standard diameter implants, according to uNE-EN ISO 14801. The main results extracted are the following: all abutments fractured by their neck; all abutments can be used in the anterior part of maxilla; and, it is necessary that studies of prosthetic attachments are made using an established protocol (uNE-EN ISO 14801), to make easier the comparison between them (AU)

Biomechanical analysis of acromioclavicular joint dislocation repair using coracoclavicular suspension devices in two different configurations.

BACKGROUND: The best treatment option for some acromioclavicular (AC) joint dislocations is controversial. For this reason, the aim of this study was to evaluate the vertical biomechanical behavior of two techniques for the anatomic repair of coracoclavicular (CC) ligaments after an AC injury. MATERIALS AND METHODS: Eighteen human cadaveric shoulders in which repair using a coracoclavicular suspension device was initiated after injury to the acromioclavicular joint were included in the study. Three groups were formed; group I (n = 6): control; group II (n = 6): repair with a double tunnel in the clavicle and in the coracoid (with two CC suspension devices); group III (n = 6): repair in a "V" configuration with two tunnels in the clavicle and one in the coracoid (with one CC suspension device). The biomechanical study was performed with a universal testing machine (Electro Puls 3000, Instron, Boulder, MA, USA), with the clamping jaws set in a vertical position. The force required for acromioclavicular reconstruction system failure was analyzed for each cadaveric piece. RESULTS: Group I reached a maximum force to failure of 635.59 N (mean 444.0 N). The corresponding force was 939.37 N (mean 495.6 N) for group II and 533.11 N (mean 343.9 N) for group III. A comparison of the three groups did not find any significant difference despite the loss of resistance presented by group III. CONCLUSION: Anatomic repair of coracoclavicular ligaments with a double system (double tunnel in the clavicle and in the coracoid) permits vertical translation that is more like that of the acromioclavicular joint. Acromioclavicular repair in a "V" configuration does not seem to be biomechanically sufficient.