The Value of Preoperative Systemic Immune-Inflammation Index as a Predictor of Prolonged Hospital Stay in Orthopedic Surgery: A Retrospective Study

PURPOSE: Many risk factors, such as the duration of surgery and higher ASA scores, are associated with longer hospitalization in patients undergoing orthopedic surgery. However, no studies have evaluated the relationship between the preoperative systemic immune-inflammation index (SII) and length of hospital stay in orthopedic surgical patients. Therefore, this study aimed to investigate whether the SII is associated with the length of hospital stay in orthopedic surgery in adults. PATIENTS AND METHODS: This was a retrospective cohort study, and data were extracted from electronic health records. Patients were included if they were older than 18 years and had undergone orthopedic surgery between [2016–2021]. The patients were divided into two groups according to the median duration of hospitalization and according to SII cut-off value (high-SII group: ≥799.86, low-SII group: <799.86). Univariate and multivariate linear regression analyses were used to identify the association between SII and length of hospitalization. RESULTS: A total of 196 patients who underwent orthopedic surgery were included, and 62 were hospitalized for >21 days. There were significant differences in terms of ASA score (P = 0.041). Patients who required a longer hospitalization of >21 days had significantly lower hemoglobin level (P < 0.001), higher duration of surgery (P = 0.015), and increased requirement of ICU admission (P < 0.001). The optimal cut-off value for preoperative SII of 799.86 stratified the patients into high-SII and low-SII groups. Patients in high-SII group had higher median LOHS (22 days) compared to low-SII group (17 days; P = 0.006). In the multivariable linear regression analysis, the SII was significantly related to the length of hospital stay (β = 0.246, 95% confidence interval [CI] 0.000–0.005, P = 0.031). CONCLUSION: A high-SII value is associated with an increased risk of longer hospitalization after orthopedic surgery.