MECHANICAL PROPERTIES OF ANTIBIOTIC-LOADED ACRYLIC BONE CEMENT

Abstract

Introduction: Infections with multiresistant bacteria have become a serious problem in joint arthroplasty. Vancomycin and teicoplanin showed high effectiveness against multiresistant bacteria as methicillin-resistant S.epidermidis (MRSE) and methicillin-resistant S.aureus (MRSA).

Objective: The purpose of the present study was to determine the mechanical properties of Palacos R+G cement (containing gentamicin) mixed with:

1. i) powdered vancomycin or teicoplanin,

2. ii) aqueous solution of vancomycin or teicoplanin.

Material and methods: Five groups of ten cements specimens were prepared. Group I (control group) consisting of Palacos-R+G cement samples (contained 0.5g of gentamicin sulphate). Group II consisting of Palacos-R+G cement mixed with 1g of finely powdered vancomycin. Group III contained 400mg powdered teicoplanin. Group IV cement samples contained aqueous solution of vancomycin (2mL water for injection plus 1g vancomycin) and Group V contained aqueous solution of teicoplanin (2mL water for injection plus 400mg teicoplanin). All cement specimens were prepared using vacuum mixing technique. In order to examine the mechanical properties of the specimens (25mm diameter × 20mm height), impact and compression tests were applied. The impact test is a well-established method for the characterization of materials’ fatigue properties, as well as of creep behavior determination in case of porous materials. The size of the produced impression after a certain number of impacts reveals the material strength. Furthermore, the compression resistance, i.e. the Young’s modulus and the yield strength are properties that can be calculated by the compression tests.

Results: The compression tests showed that the specimens from Group III (containing 400mg of teicoplanin) had overall better mechanical properties, having approximately 10% higher Young’s modulus in comparison with specimens from Group II (containing van-comycin) and specimens from Group III (control group). Yield strength had no significant difference between the three groups. The impact test revealed a corresponding tendency, with the specimens containing 400mg of teicoplanin having the smaller impression (increased fatigue strength) when compared with specimens from the other groups.

With regards to samples from Groups IV and V (aqueous solutions of antibiotics) mechanical properties were significant deteriorated in comparison with cement samples from the other groups.

Conclusions: The experimental data showed that the addition of 400mg teicoplanin in Palacos R+G bone cement had better mechanical properties compared with addition of 1g vancomycin or than Palacos R+G cement with gentamicin as a single drug.

Aqueous solutions of antibiotics must not be added to the bone cement because they dramatically impair mechanical properties of the cement.