Abstract
Introduction
Hip and knee arthroplasty present surgeons with difficult bone loss. In these cases the use of morselized allograft is a well established way of optimizing early implant fixation. In revisions, the surgical field is potentially infected. The use of allograft bone creates a “dead space” in which the immune system has impaired access, and even a small amount of bacteria may therefore theoretically increase the risk of infection.
In vivo studies have shown that allograft bone is suitable as a vehicle of local antibiotic delivery.
We hypothesized that the allograft bone could be used as a local antibiotic delivery vehicle without impairing the implant fixation, tested by mechanical push-out.
Material and Methods
Following approval of the Institutional Animal Care and use Committee we implanted a cylindrical (10×6 mm) porous-coated Ti implant in each distal femur of 12 dogs observed for 4 weeks. The implants were surrounded by a circumferential gap of 2.5 mm impacted with a standardized volume of morselized allograft. In the two intervention groups, 0.2ml tobramycin solution of high (800mg/ml) and low (200mg/ml) concentration was added to the allograft, respectively. In the control group 0.2ml saline was added to the allograft.
ANOVA-test was applied followed by paired t-test where appropriate. A p-value < 0,05 was considered statistically significant.
Results
The impregnation of allograft bone revealed a relative decrease in biomechanical fixation. The decrease was higher in the high dose group than in the low dose group. The most extreme difference was a decrease in strength by 18% (P = 0,511), stiffness 15% (P = 0,135) and energy absorption 27% (P = 0,784).
Conclusion
The result shows a trend towards a decrease in implant fixation correlating with the antibiotic concentration. Although the results are not statistically significant the use of antibiotic impregnation should be used with caution until further reaserch has been conducted.
