Introduction: Osteoporosis is one of the major diseases worldwide, affecting millions of elderly people, with severe economical and medical consequences. The most commonly used method for the determination of decreased bone quality is the assessment of Bone Mineral Density, measured by dual X-ray absorptiometry (DXA). However DXA is quantitative and not qualitative index of the bone structure.

The purpose of this study was to correlate the bone mineral density measured by DXA with the mechanical properties of the femoral neck.

Materials and Methods: Bone mineral density of the proximal femur of 30 patients (27 women, 3 men) undergoing total hip displacement was estimated by DXA. The average age of these patients was 63.7 years. Patients with sort femoral neck or previous surgeries in proximal femur were excluded from the study. After hip replacement bone samples (femoral head and neck) were frozen and stored at −60 °C.

A plane bone slice with 6mm thickness was sawed of femoral neck using a double cutting saw. The exact specimen dimensions were measured using a sliding calliper with high accuracy.

All bone specimens were destructively tested on a material testing machine, in order to determine the material properties (Young’s modulus and yield stress) of the samples. The maximum available compression load was 100 kN with a load rate of 10 kN/min. The operational parameters and experimental data were fully controlled and handled by a graphical software package. Finally all data were evaluated and statistically analyzed.

Results: A strong linear correlation of bone mineral density (T-score) with maximum failure load of samples was noted (R2=0.852). No significant differences in Young’s modulus values, was found between bone samples.

Conclusions: Bone mineral density measured by DXA, although has limitations, remain a strong predictor of bone strength in the femoral neck region.

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:

i) powdered 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.