Background: Nonunion rates in hind or midfoot arthrodesis have been reported as high as 41%. The most notable and readily modifiable risk factor that has been identified is smoking. In 2018, 14.4% of the UK population were active smokers. We examined the effect of smoking status on union rates for a large cohort of patients undergoing hind- or midfoot arthrodesis. Methods: In total, 381 consecutive primary joint arthrodeses were identified from a single surgeon’s logbook (analysis performed on a per joint basis, with a triple fusion reported as 3 separate joints). Patients were divided based on self-reported smoking status. Primary outcome was clinical union. Delayed union, infection, and the need for ultrasound bone stimulation were secondary outcomes. Results: Smoking prevalence was 14.0%, and 32.2% were ex-smokers. Groups were comparable for sex, diabetes, and body mass index. Smokers were younger and had fewer comorbidities. Nonunion rates were higher in smokers (relative risk, 5.81; 95% CI, 2.54-13.29; P < .001) with no statistically significant difference between ex-smokers and nonsmokers. Smokers had higher rates of infection ( P = .05) and bone stimulator use ( P < .001). Among smokers, there was a trend toward slower union with heavier smoking ( P = .004). Conclusion: This large retrospective cohort study confirmed previous evidence that smoking has a considerable negative effect on union in arthrodesis. The 5.81 relative risk in a modifiable risk factor is extremely high. Arthrodesis surgery should be undertaken with extreme caution in smokers. Our study shows that after cessation of smoking, the risk returns to normal, but we were unable to quantify the time frame. Level of Evidence: Level III, retrospective cohort study.
