Nutritional and Inflammatory Indices and the Risk of Surgical Site Infection After Fragility Hip Fractures: Can Routine Blood Test Point to Patients at Risk?

Background: Surgical site infection (SSI) after fragility hip fracture (FHF) surgery is associated with increased morbidity and mortality. We aim to utilize several established nutritional and inflammatory indices to characterize patients at risk. Patients and Methods: A retrospective cohort study of patients 65 years and older, who underwent surgery following FHFs between January 2012 and June 2020. Those patients who presented with post-operative infection in the year after surgery were compared with patients who did not. The primary outcomes were serum albumin, protein energy malnutrition (PEM), albumin to globulin ratio, prognostic nutritional index (PNI), the systemic immune inflammation index, platelet to lymphocyte ratio, neutrophil to lymphocyte ratio, and body mass index. Results: A total of 1,546 patients, ages 82.4 - 7.7, were included; 55 of whom presented with SSI. Demographics and comorbidities were similar. Anticoagulation treatment was more prevalent in the infected group (32.7% vs. 13.9%, p < 0.001) as were intra-capsular fractures (60% vs. 42.9%, respectively; p = 0.012). Of all indices estimated, only the PNI and the PEM were found to differ significantly (44.7 - 9.6 and 26.1% vs. 49.4 - 17.3 and 13.6% for the study and control groups respectively; p = 0.002 and 0.027). A logistic regression model was calculated to evaluate the contribution of fracture type and anticoagulation treatment as possible confounders. Both indices were found to be significant for infection after regression odds ratio, 2.25 for PEM; (95% confidence interval [CI], 1.089-4.344) and odds ratio, 0.97 for PNI (95% CI, 0.937-0.996). Conclusions: The PNI and the PEM were found to correlate with infection risk after FHF surgery. As both can be easily calculated from an accessible blood test, we recommend their routine use as a screening tool for tailored management of patients at risk for SSI.