Which risk factor was statistically significant for SSI after knee arthroplasty based on the reported odds ratios?

• A. Pre-operative hair removal
• B. Inadequate preparation
• C. Inadequate glucose control
• D. Contaminated/dirty surgery

Answer: (A)

Understanding how to read odds ratios and statistical significance in infection risk studies helps you see which factors truly affect SSI after knee replacement. When a risk factor shows an odds ratio above 1 with a p-value below 0.05 (and a confidence interval that does not include 1), it’s considered significantly associated with higher odds of infection.

In the data you’re looking at, pre-operative hair removal had an odds ratio greater than 1 and was statistically significant. This means patients who underwent hair removal before surgery had higher odds of developing a surgical site infection compared with those who did not have hair removal, and this finding is unlikely due to chance. A plausible reason is that shaving hair can create microabrasions on the skin, compromising the barrier and providing an entry point for bacteria.

The other factors—inadequate preparation, inadequate glucose control, and contaminated/dirty surgery—did not show a statistically significant association in this analysis. Their odds ratios either did not exceed 1 with statistical significance or their confidence intervals included 1, so they weren’t identified as independent risk factors in this study.