When fabricating an antibiotic-loaded cement spacer for two-stage revision of periprosthetic joint infection, vancomycin is frequently combined with an aminoglycoside such as gentamicin. The principal pharmacological reason for this combination is:

• A The combination reduces the elastic modulus allowing better spacer flexibility
• B Vancomycin lowers the peak curing temperature protecting the aminoglycoside
• C Aminoglycosides buffer the acidic environment inside the cement matrix
• D The two drugs synergistically increase each other's elution from the cured cement ✓

Explanation

Combining vancomycin with an aminoglycoside in polymethylmethacrylate produces synergistic elution: powder mixing creates additional channels as the different particle fractions pack together, increasing the release of both antibiotics compared with either drug alone. Both agents are also heat stable across the exothermic curing temperature of cement. The combination does not meaningfully alter curing temperature, cement pH, or mechanical properties at standard dosing, so the elution synergy is the decisive advantage.

Reference: Miller's Review of Orthopaedics, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.