Background. Smoking has been associated with poor tissue oxygenation and vascularisation, predisposing smokers to a higher risk for postsurgical infections. The aim of this study was to estimate and compare the incidence of prosthetic joint infection (PJI) following primary total joint arthroplasty (TJA) according to smoking status. Methods. A prospective hospital-registry based cohort was used including all primary total knee and hip arthroplasties performed between 03/1996 and 12/2013 and following them until 06/2014. Smoking status at time of surgery was classified in never, former and current smoker. Incidence rates and incidence rate ratios (IRR) for PJI according to smoking status were assessed within the first year and over the whole study period. Adjusted IRRs were obtained using cox regression model. Adjustment was performed for the following baseline characteristics: age, sex, BMI, ASA score, diabetes, arthroplasty site (knee or hip) and surgery duration. Results. We included 8,559 TJAs, 3,361 knee and 5,198 hip arthroplasties. Mean age was 70 years, 61% were women, mean follow-up time was 77 months. 5,722 were never (group 1), 1,315 former (group 2) and 1,522 current (group 3) smokers. Over the study period, 108 PJI occurred. Incidence rates of infection within one year were for group 1, 2 and 3, respectively: 4.7, 10.1 and 10.9 cases/1000 person-year. Comparing ever- vs. never-smokers, the adjusted IRR was 1.84 (95% CI 1.05–3.2). Incidence rates for infection over the whole study period were 1.5, 3.1 and 2.7 cases/1000 person-years for group 1, 2 and 3, respectively. Adjusted IRR for ever- vs. never-smokers was 1.46 (95% CI 0.97–2.19). Conclusions. Smoking was associated with an about 1.5 times higher incidence rate of PJI following TJA. The difference was established already in the first year after surgery and remained thereafter. Level of Evidence. prospective registry based comparative cohort study (level II)

Previous research has shown an increase in chromosomal aberrations in patients with worn implants. The type of aberration depended on the type of metal alloy in the prosthesis. We have investigated the metal-specific difference in the level of DNA damage (DNA stand breaks and alkali labile sites) induced by culturing human fibroblasts in synovial fluid retrieved at revision arthroplasty.

All six samples from revision cobalt-chromium metal-on-metal and four of six samples from cobalt-chromium metal-on-polyethylene prostheses caused DNA damage. By contrast, none of six samples from revision stainless-steel metal-on-polyethylene prostheses caused significant damage. Samples of cobalt-chromium alloy left to corrode in phosphate-buffered saline also caused DNA damage and this depended on a synergistic effect between the cobalt and chromium ions.

Our results further emphasise that epidemiological studies of orthopaedic implants should take account of the type of metal alloy used.