Simulated large joint fluid model for evaluating intra-articular antibiotic delivery systems: initial evaluation using antibiotic-loaded calcium sulfate beads

Authors

Edward J. McPherson, Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Santa Monica, 90404, USA.
Jessica A. Jennings, Department of Biomedical Engineering, University of Memphis, Memphis, 38152, USA.Follow
Omar Yunis, Department of Biomedical Engineering, University of Memphis, Memphis, 38152, USA.
Michael A. Harris, Department of Biomedical Engineering, University of Memphis, Memphis, 38152, USA.
Matthew V. Dipane, Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Santa Monica, 90404, USA.
Nora L. Curtin, Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Santa Monica, 90404, USA.
Madhav Chowdhry, Nuffield Department of Primary Care Health Sciences, Kellogg College, University of Oxford, Oxford, OX1 2JD, UK​​​​​​​.
Andrew J. Wassef, Long Beach Lakewood Orthopedic Institute, Long Beach, 90808, USA​​​​​​​.
Joel D. Bumgardner, Department of Biomedical Engineering, University of Memphis, Memphis, 38152, USA.
Scott P. Noel, Austin Medical Ventures, Germantown, 38138, USA.

Abstract

: Local antimicrobial delivery via calcium sulfate (CaSO ) beads is used as an adjunctive treatment for periprosthetic joint infection. There is limited clinical information describing the performance of antimicrobial-loaded CaSO (ALCS) in large-scale applications. We developed a simulated large joint model to study properties of eluting ALCS. : The in vitro testing platform was an adapted standardized model for tribological testing of prosthetic total hips and total knees (ASTM F732). The model was 70 mL total fluid volume, 25 % bovine serum, and 75 % phosphate-buffered saline, using ISO standard 14242-1 for human synovial fluid simulation. Four brands of CaSO were evaluated. Each 10 mL of CaSO was loaded with 1.2 grams (g) of tobramycin and 1 g of vancomycin powders. A 35 mL bead volume, equaling 175 beads, of each product was placed in incubated flasks. The test period was 6 weeks with scheduled interval fluid exchanges. Fluid samples were tested for antibiotic and calcium concentrations and pH. : Antibiotic elution showed an initial burst on Day 1, followed by a logarithmic reduction over 1 week. Tobramycin fully eluted within 2.5 weeks. Vancomycin showed sustained release over 6 weeks. Calcium ion concentrations were high, with gradual decrease after 3 weeks. All four CaSO products were inherently acidic. Fluid became more acidic with the addition of antibiotics primarily driven by vancomycin. : Clinicians should be cognizant of tobramycin elution burst with ALCS in large loads. The main driver of acidic pH levels was vancomycin. We propose that joint complications may result from lowered fluid acidity, and we suggest clinical study of synovial pH.

Publication Title

Journal of bone and joint infection

Recommended Citation

McPherson, E. J., Jennings, J. A., Yunis, O., Harris, M. A., Dipane, M. V., Curtin, N. L., Chowdhry, M., Wassef, A. J., Bumgardner, J. D., & Noel, S. P. (2022). Simulated large joint fluid model for evaluating intra-articular antibiotic delivery systems: initial evaluation using antibiotic-loaded calcium sulfate beads. Journal of bone and joint infection, 7 (3), 117-125. https://doi.org/10.5194/jbji-7-117-2022