Aim. Smoking is known to impair wound healing and to increase the risk of peri-operative adverse events and is associated with orthopaedic infection and fracture non-union. Understanding the magnitude of the causal effect on orthopaedic infection recurrence may improve pre-operative patient counselling. Methods. Four prospectively-collected datasets including 1173 participants treated in European centres between 2003 and 2021, followed up to 12 months after surgery for clinically diagnosed orthopaedic infections, were included in logistic regression modelling with Inverse Probability of Treatment Weighting for current smoking status [1–3]. Host factors including age, gender and ASA score were included as potential confounding variables, interacting through surgical treatment as a collider variable in a pre-specified structural causal model informed by clinical experience. The definition of infection recurrence was identical and ascertained separately from baseline factors in three contributing cohorts. A subset of 669 participants with positive histology, microbiology or a sinus at the time of surgery, were analysed separately. Results. Participants were 64% male, with a median age of 60 years (range 18–95); 16% of participants experienced treatment failure by 12 months. 1171 of 1173 participants had current smoking status recorded. As expected for the European population, current smoking was less frequent in older participants (Table 1). There was no baseline association between Charlson score or ASA score and smoking status (p=0.9, p=1, Chi squared test). The estimated adjusted odds ratio for treatment failure at 12 months, resulting from current smoking at the time of surgery, was 1.37 for all participants (95% CI 0.75 to 2.50) and 1.53 for participants with recorded confirmatory criteria (95% CI 1.14 to 6.37). Conclusions. Smoking contributes to infection recurrence, particularly in people with unequivocal evidence of osteomyelitis or PJI. People awaiting surgery for orthopaedic infection should be supported to cease smoking, not only to reduce anaesthetic risk, but to improve treatment outcomes. Limitations of this study include unmeasured socioeconomic confounding and social desirability bias resulting in uncertainty in true smoking status, resulting in underestimated effect size

Background. Fracture-related infection (FRI) is treated by adequate debridement, lavage, fracture stabilization (if indicated), adequate soft tissue coverage and systemic antimicrobial therapy. Additional administration of local antibiotics (LA), placed directly in the surgical field, is thought to be beneficial for successful eradication of infection. Aims. 1) To evaluate the effect of local antibiotics on outcome in patients with FRI. 2) To evaluate whether bacterial resistance to the implanted local antibiotics influences its efficacy. Methods. A multinational cross-sectional study was performed in patients with FRI, diagnosed according to the FRI consensus definition, between January 2015 and December 2019. Patients who underwent surgical treatment for FRI at all time points after injury were considered for inclusion. Patients were followed-up for at least 12 months. The primary outcome was the recurrence rate of FRI at follow-up. Inverse Probability for Treatment Weighting (IPTW) modeling and multivariable regression analyses were used to assess the relationship between the application of LA and recurrence rate of FRI at 12 months, 24 months and final follow-up. Results. Overall, 433 FRIs in 429 patients were included. A total of 251 (58.0%) cases were treated with LA. Gentamicin was the most frequently used LA (247/251). Recurrence of infection after surgery occurred in 25/251 (10%) patients who received LA and in 34/182 (18.7%) patients who did not. The use of LA reduced the recurrence rate of FRI at 12 months (HR: 0.69; 95% CI [0.24–1.96]) and 24 months (HR: 0.55; 95% CI [0.22–1.35]). Resistance of cultured microorganisms to the LA was not associated with a higher risk of recurrence of FRI (HR: 0.75, 95% CI [0.32–1.74]). Conclusion. The application of LA in treatment of FRI is likely to reduce the risk of recurrence of FRI as the risk reduction was consistent and clinically relevant but it did not reach statistical significance. High local antibiotic concentrations eradicate most pathogens regardless of susceptibility test results