The association between cement type and the subsequent risk of revision surgery in primary total hip replacement.

Background and purpose - To further improve the success of joint replacement surgery, attention needs to be paid to variations associated with improved or worsened outcomes. We investigated the association between the type of bone cement used and the risk of revision surgery after primary total hip replacement. Methods - We conducted a prospective study of data from the National Joint Registry for England and Wales between April 1, 2003 and December 31, 2013. 199,205 primary total hip replacements performed for osteoarthritis where bone cement was used were included. A multilevel over-dispersed piecewise Poisson model was used to estimate differences in the rate of revision by bone cement type adjusted for implant type, head size, age, sex, ASA grade, and surgical approach. Results - The rate of revision was higher in DePuy CMW3 medium viscosity with gentamicin (IRR 2.0, 95% CI 1.5-2.7) and DePuy SmartSet high viscosity plain (IRR 2.7, 95% CI 1.1-5.5), and lower in DePuy CMW1 high viscosity plain (IRR 0.44, 95% CI 0.19-0.89) bone cements compared with Heraeus Palacos high viscosity with gentamicin. Revision rates were similar between plain and antibiotic-loaded bone cement. Interpretation - The majority of bone cements performed similarly well, excluding DePuy SmartSet high viscosity and CMW3 high viscosity with gentamicin, which both had higher revision rates. We found no clear differences by viscosity or antibiotic content.

Characterisation of in vivo release of gentamicin from polymethyl methacrylate cement using a novel method.

PURPOSE: The purpose of this study was to investigate the in vivo elution kinetics of gentamicin from bone cement by assessing antibiotic levels in the urine. METHODS: Urinary samples of 35 patients who had undergone primary total hip arthroplasty were collected post-operatively. Gentamicin concentrations were analysed using the fluorescence polarisation immunoassay technique. RESULTS: The mean duration of urinary gentamicin release in all cases was 43 days (range 13-95). There was still detectable gentamicin at the final collection in 20% (7/35) of cases, and in these cases, the mean gentamicin release was 71 days. CONCLUSIONS: From the assessment of urinary gentamicin, we were able to demonstrate the biphasic gentamicin elution from bone cement. In addition, there were detectable concentrations of the antibiotic from the urinary samples for prolonged periods of up to two to six months. Our study indicates that the assessment of urinary antibiotics can offer a non-invasive method of monitoring the in vivo release kinetics of antibiotics from bone cement.