Background: Liquid gentamicin is approved by the Food and Drug
Administration, is readily available, and is much less costly than tobramycin,
the more commonly used antibiotic in cement spacers. The purpose of the
present study was to test the mechanical properties, elution characteristics,
and antibacterial activity of liquid gentamicin in an acrylic bone cement
Methods: Standardized specimens consisting of Palacos cement
combined with liquid gentamicin, powdered tobramycin, or no antibiotic were
fashioned, and the three groups were tested with regard to compressive and
tensile strength, elution characteristics (with use of radioimmunoassays), and
antibacterial activity (with use of bioassays).
Results: The ultimate compression strength decreased by 49% (from
64.65 ± 3.89 MPa to 32.96 ± 3.33 MPa) and the ultimate tension
strength decreased by 46% (from 35.85 ± 2.97 MPa to 19.20 ± 0.36
MPa) when the specimens containing 480 mg of liquid gentamicin were compared
with the controls. The addition of tobramycin had no significant effect
compared with the controls. The majority of gentamicin was released from the
cement during the initial twenty-four hours (mean concentration, 26.4 mcg/mL).
The mean concentrations at three and six weeks were 4.15 and 0.65 mcg/mL,
respectively. The bioassays confirmed the bactericidal activity of the
gentamicin released from the cement.
Conclusions: Liquid gentamicin in bone cement is potent and
bactericidal. Although the mechanical properties of the cement are
significantly diminished by the addition of liquid gentamicin, the temporary
nature of the cement spacer makes its use potentially worthwhile given the
substantial cost savings to the hospital and the patient.
Clinical Relevance: Substantial health-care dollars could be saved
by the use of liquid gentamicin in cement spacers that are employed for the
treatment of infection following total joint arthroplasty. Additional studies
are needed to determine the clinical efficacy and safety of such