Absorbable collagen implants localise delivery of gentamicin in uncemented primary total hip arthroplasty

Infection remains a major reason for revision arthroplasty. Localised antibiotic delivery can produce effective concentrations while minimising risks from systemic exposure. Gentamicin-impregnated collagen implants can reduce surgical site infection rates, but orthopaedic usage has been limited. As a preliminary test of appropriate dosage and safety, we measured local and systemic gentamicin levels after implanting collagen carriers during primary total hip arthroplasty (uncemented, anterior approach), in addition to routine intravenous cephalosporin prophylaxis. The day after surgery, blood samples were taken and wound fluid was sampled from an anaesthetic-infiltrating catheter. Median gentamicin levels were 54.7 mg/l in wound fluid (n=32) and 0.7 mg/l in serum (n=37). Serum levels were all below 2 mg/l; they showed a moderate negative correlation to time elapsed between surgery and sampling, but no significant correlation with local concentrations. No infections or adverse effects were detected over six weeks’ follow-up. These data suggest that delivery of gentamicin to the surgical site via collagen pads achieves high local antibiotic concentrations, with corresponding serum levels within an accepted low-risk range. A single pad produced levels likely to be effective against bacteria associated with infected joint prostheses. Gentamicin- collagen pads may thus provide a useful adjunct to systemic prophylaxis in primary arthroplasty