Comparison of Systemic Inflammatory Markers in Total Knee Arthroplasty Under Spinal vs General Anesthesia: A Retrospective Study

Purpose In total knee arthroplasty (TKA), both surgical trauma and the type of anesthesia administered can significantly affect systemic inflammation, which may influence postoperative recovery. This retrospective study aimed to compare perioperative changes in blood-derived systemic inflammatory markers—specifically the systemic immune-inflammation index (SII) and the systemic inflammation response index (SIRI)—in patients undergoing TKA under general versus spinal anesthesia. Methods This retrospective analysis included 849 patients who underwent elective primary TKA between January 2020 and April 2025. Inclusion criteria were age 18–75 years and ASA physical status I–II. Patients with BMI ≥ 40 kg/m², ASA ≥ III, major comorbidities, active infection, revision surgery, or incomplete lab data were excluded. Patients were categorized into spinal anesthesia (Group S) and general anesthesia (Group G) groups. Pre- and postoperative hemograms were used to calculate SII and SIRI values; ΔSII and ΔSIRI were defined as absolute differences. Groups were compared in terms of inflammatory markers, total opioid requirement, postoperative complications, and hospital stay. Group comparability regarding age, ASA, and comorbidities was assessed, but no multivariate adjustment was performed due to the observational design. Results A total of 849 patients were included in the study. The median ΔSII value was significantly higher in the general anesthesia group [Group G: 1448.47 (IQR: 677.78–2670.86)] compared to the spinal anesthesia group [Group S: 1060.75 (IQR: 463.69–2093.28); p < 0.001]. Similarly, the ΔSIRI value was higher in Group G [4.56 (IQR: 2.31–9.23)] than in Group S [3.69 (IQR: 1.70–7.05); p = 0.002]. The total opioid requirement within the first 24 postoperative hours was also significantly greater in Group G (p < 0.001). No statistically significant differences were found between the groups in terms of postoperative complication rates (p = 0.48) or length of hospital stay (p = 0.18). Conclusion Compared to general anesthesia, spinal anesthesia was associated with a lower perioperative increase in systemic inflammatory blood markers in patients undergoing TKA. While no difference was observed in short-term clinical outcomes, these findings suggest that spinal anesthesia may offer an immunological advantage. Given the retrospective nature of the study, prospective research is warranted to determine whether these biomarker differences have meaningful clinical implications.