A gentamicin-releasing coating for cementless hip prostheses—Longitudinal evaluation of efficacy using in vitro bio-optical imaging and its wide-spectrum antibacterial efficacy^†

Cementless prostheses are increasingly popular in total hip arthroplasties. Therewith, common prophylactic measures to reduce the risk of postoperative infection like the use of antibiotic-loaded bone cements, will no longer be available. Alternative prophylactic measures may include the use of antibiotic-releasing coatings. Previously, we developed a gentamicin-releasing coating for cementless titanium hip prostheses and derived an appropriate dosing of this coating by adjusting the amount of gentamicin in the coating to match the antibacterial efficacy of clinically employed gentamicin-loaded bone cement. In this manuscript, we investigated two important issues regarding the prophylactic use of this 1 mg cm⁻² bioactive gentamicin-releasing coating in cementless total hip arthroplasty: (1) its ability to prevent bacterial growth in a geometrically relevant set-up and (2) its antibacterial spectrum. A geometrically relevant set-up was developed in which miniature titanium stems were surrounded by agar, contaminated with bioluminescent Staphylococcus aureus. Novel, bio-optical imaging was performed allowing noninvasive, longitudinal monitoring of staphylococcal growth around miniature stems with and without the gentamicin-releasing coating. Furthermore, the antibacterial efficacy of the gentamicin-releasing coating was determined against a wide variety of clinical isolates, including bioluminescent Staphylococcus aureus strains, using traditional zone of inhibition measurements. The gentamicin-releasing coating demonstrated a wide-spectrum of antibacterial efficacy and successfully prevented growth of bioluminescent staphylococci around a miniature stem mounted in bacterially contaminated agar for at least 60 h. This implies that the gentamicin-releasing coating has potential to contribute to the improvement of infection prophylaxis in cementless total hip arthroplasty. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A:3220–3226, 2012.