Release of gentamicin from acrylic bone cement. Elution and diffusion studies

Area of Science:

• Biomaterials Science
• Drug Delivery Systems
• Orthopedic Surgery

Background:

• Antibiotic release from methylmethacrylate bone cement is crucial for preventing surgical site infections.
• Previous studies on antibiotic elution have yielded inconsistent results, suggesting a need to re-evaluate release mechanisms.

Purpose of the Study:

• To investigate the fundamental mechanism of gentamicin release from methylmethacrylate bone cement.
• To determine if the cement matrix is permeable to gentamicin and if release occurs via diffusion or through structural defects.

Main Methods:

• In vivo elution studies using sheep models with methylmethacrylate rods loaded with varying gentamicin concentrations (0.5g and 1.5g).
• In vitro diffusion studies using methylmethacrylate disks and gentamicin or methylene blue solutions.
• Bioassay of eluted gentamicin using the tube-diffusion technique.

Main Results:

• In vivo studies showed significantly greater gentamicin release from higher-loaded cement samples.
• The increased release was attributed to a higher number of defects, including voids and cracks, containing gentamicin.
• In vitro studies demonstrated permeability of methylmethacrylate to gentamicin and methylene blue.

Conclusions:

• Gentamicin release from methylmethacrylate bone cement primarily occurs through interconnected voids and cracks, not homogeneous diffusion.
• The structural integrity and defect density of the cement significantly influence antibiotic elution.
• Understanding these release pathways is critical for optimizing antibiotic delivery in orthopedic procedures.