Adding vancomycin to bone cement: research on its influence on mechanical and fixation strength using rabbit femoral prostheses.

OBJECTIVE

To compare the influence of different methods of adding vancomycin on the strength of bone cement used for fixing rabbits' femoral prostheses.

METHODS

Eighteen New Zealand white rabbits (36 femora) were allocated to three groups of six rabbits (12 femora) each: a control group, an experimental group 1 and experimental group 2. The bone cement used in the control group was mixed manually without vancomycin; in experimental group 1 it was mixed manually with 5% (2 g/40 g) vancomycin; and in experimental group 2 it was mixed in a vacuum with 5% (2 g/40 g) vancomycin. The cement combinations were then used to fill the marrow cavity of rabbit femurs to fix prostheses. An electronic universal testing machine (EUTM) was used to test the pullout force of the prostheses with bone cement 48 hours later. Student's paired t-test was used for statistical analysis.

RESULTS

It was found that the maximum load of pullout force was 559.3 ± 82.3 N in the control group; 523.6 ± 86.5 N in experimental group 1; and 645.1 ± 105.9 N in experimental group 2. Statistical analysis showed there was no significant difference between the control group and experimental group 1 (P > 0.05). However, there were significant differences between the control group and experimental group 2 (P < 0.05); and between experimental group 1 and experimental group 2 (P < 0.05).

CONCLUSION

When bone cement and vancomycin were mixed manually in a low concentration (<5%) vancomycin had no influence on the strength of the bone cement. However, bone cement and vancomycin mixed at the same concentrations in a vacuum did have a statistically significant effect on the strength of the bone cement.