Surfactant-stabilized emulsion increases gentamicin elution from bone cement

Background: Liquid antimicrobial use for antimicrobial-loaded bone cement is limited because of decreased strength and small volume that can be loaded. Emulsifying the liquid antimicrobial into the monomer may address both issues. Questions/purposes: We determined the effect of using a surfactant-stabilized emulsion on antimicrobial release, compressive strength, and porosity. Methods: We made 144 standardized test cylinders from emulsified antimicrobial-loaded bone cement (three batches, 72 cylinders) and control antimicrobial-loaded bone cement made with antimicrobial powder (three batches, 72 cylinders). For each formulation, five specimens per batch (n = 15) were eluted in infinite sink conditions over 30 days for gentamicin delivery; five specimens per batch were axially compressed to failure after elution of 0, 1, and 30 days (n = 45); and two noneluted specimens and two gentamicin delivery specimens from each batch (n = 12) were examined under scanning electron microscopy for porosity. Antimicrobial release and compressive strength were compared across cement type and time using repeated-measures ANOVA. Results: Emulsified antimicrobial-loaded bone cement released four times more antimicrobial than control. Compressive strength of emulsified antimicrobial-loaded bone cement was less than control before elution (58.1 versus 81.3 MPa) but did not decrease over time in elution. Compressive strength of control antimicrobial-loaded bone cement decreased over 30 days in elution (81.3 versus 73.9 MPa) but remained stronger than emulsified antimicrobial-loaded bone cement. Porosity was homogeneous, with pores ranging around 50 μm. Conclusions: Emulsified antimicrobial-loaded bone cement has homogeneous porosity with increased drug release but a large loss of strength. Clinical Relevance: Liquid antimicrobials are released from emulsified antimicrobial-loaded bone cement, but increased strength is needed before this method can be used for implant fixation.