Tourniquet use in total knee arthroplasty and systemic inflammation: a retrospective cohort study

BACKGROUND: Pneumatic tourniquet use during total knee arthroplasty (TKA) remains controversial. Although it reduces intraoperative blood loss, tourniquet-induced ischemia-reperfusion may amplify systemic inflammation. Hematologic immune-inflammatory indices such as the Systemic Immune-Inflammation Index (SII) and Systemic Inflammation Response Index (SIRI) provide simple and cost-effective measures of systemic inflammation. This study aimed to investigate the independent effect of tourniquet use on early postoperative SII and SIRI following primary TKA. METHODS: In this retrospective cohort study, 120 patients (60 tourniquet, 60 non-tourniquet) undergoing primary TKA for Kellgren-Lawrence grade IV osteoarthritis were analyzed. Preoperative and 24-hour postoperative complete blood counts were used to calculate SII and SIRI values. Between-group comparisons, within-group time-dependent analyses, correlation testing, and multivariable linear regression modeling were performed to determine independent predictors of percentage increases in SII and SIRI. Effect sizes were reported alongside statistical significance. RESULTS: Baseline demographic characteristics and preoperative SII/SIRI values were comparable between groups. Tourniquet use was associated with significantly lower postoperative hemoglobin decline (2.64 ± 0.99 vs. 3.53 ± 0.75 g/dL, p = 0.001). However, postoperative inflammatory activation was markedly higher in the tourniquet group. Postoperative SII (2387.0 ± 1009.2 vs. 1900.8 ± 928.6, p = 0.003) and SIRI (8.54 ± 2.53 vs. 5.29 ± 2.38, p = 0.001) were significantly elevated. Percentage increases in SII and SIRI were substantially greater in the tourniquet group, with large effect sizes. In multivariable regression analyses, tourniquet use independently predicted both SII increase (β = 91.8, p = 0.001, R²=0.34) and SIRI increase (β = 272.8, p = 0.001, R²=0.35). CONCLUSIONS: Tourniquet application during primary TKA is independently associated with a significantly greater early systemic inflammation, despite reduced perioperative hemoglobin loss. These findings suggest that tourniquet use is associated with higher early postoperative systemic inflammatory marker levels beyond local tissue effects. Prospective studies are warranted to determine whether minimizing tourniquet exposure can improve postoperative recovery and clinical outcomes. LEVEL OF EVIDENCE: Level IV, retrospective cohort study.