Increased Associated Risk of SSI
Moderate strength evidence supports that patients meeting one or more of the following criteria are at an increased risk of infection after hip and knee arthroplasty:

• Chronic Kidney Disease
• Diabetes (conflicting evidence)
• Tobacco Use/Smoking (conflicting evidence)
• Malnutrition (conflicting evidence)

Rationale
Chronic Kidney Disease
The risk of SSI in patients with chronic kidney disease (CKD) correlates positively with the severity of renal disease. Five high quality studies revealed using multivariate analysis and to identify the increased risk of SSI in patients with CKD. The severity of CKD and the description of dialysis and transplant patients were not identifiable within the studies.

Diabetes
26 high quality studies were reviewed. 13 of the studies showed a correlation between diabetes and the risk of SSI. 13 studies showed no correlation between diabetes and the risk of SSI. The strength of the recommendation was classified as “moderate” due to the divergence between the study findings. The impact of quality diabetic control could not be determined on the outcomes of the studies.

Tobacco Use
22 high quality studies were reviewed. 9 studies showed an association between tobacco use and increased risk of SSI. 12 studies showed no statistically significant differences between smokers and nonsmokers regarding associated risk of SSI. Many of the studies do not define the amount of tobacco
used, description of current versus former smokers, or the length of time for use of tobacco. While tobacco use is widely accepted as a risk factor for increasing the risk of SSI, of 22 HQ studies, 9 confirmed the correlation and 12 failed to confirm the correlation, and one showed a negative association with smoking and risk of SSI. This may be due to the definition of magnitude, effect size, heterogeneity of populations between studies.

Malnutrition
Malnutrition is a known risk factor for patients undergoing surgical procedures. Patients with malnutrition can suffer from a range of poor outcomes including increased risk of death, sepsis and poor wound healing. Six high quality articles were reviewed. Of these, three articles identified a correlation with increased risk of SSI. Bohl et al 2016 identified significantly increased risks of SSI associated with hypoalbuminemia. Grammatico et al 2015 also showed higher risks of SSI due to malnutrition.