Effect of trabecular metal on the elution of gentamicin from Palacos cement.

Periprosthetic joint infections continues to be a common complication in total joint arthroplasty, resulting in significant morbidity, mortality, and additional cost. Trabecular metal implants with an internal cemented interface may be customizable drug delivery devices with an ingrowth interface. Thirty-six acetabular implants were assembled in vitro, half with a trabecular metal shell and half without. The antibiotic loaded bone cement was prepared via three different mixing techniques and at two different mixing times. Mixing time had a significant effect on the total amount of gentamicin eluted. The long mixing protocol eluted up to 126% (p = 0.001) more gentamicin than the short mixing protocol at 4 h and 192% (p < 0.001) more at 7 days. Hand or mechanical mixing technique had no significant effect on elution at 4 h. At 7 days, the mechanical mixing system under vacuum eluted over 50% (p = 0.031) more gentamicin than without a vacuum and nearly 60% (p = 0.040) more gentamicin than hand mixing. The use of a trabecular metal shell had no significant effect on the bulk elution of gentamicin at 4 h (p > 0.05) but significantly reduced total gentamicin elution under certain mixing protocols at 7 days. A possible optimization strategy to improve elution kinetics would be to use a long mixing time with a mechanical mixing system under vacuum. The establishment of trabecular metal as an effective delivery vehicle for antibiotics makes possible an entirely new class of drug eluting device designs.