The Effect of Femoral Nerve Block on the Neutrophil-to Lymphocyte Ratio in Total Knee Arthroplasty

This study investigated whether femoral nerve block (FNB) reduces postoperative systemic inflammation, as measured by the neutrophil-to-lymphocyte ratio (NLR), in patients undergoing total knee arthroplasty (TKA) under spinal anesthesia. It was hypothesized that FNB would mitigate the inflammatory response by alleviating pain and surgical stress. In this retrospective cohort study, data from 199 patients who underwent unilateral TKA between January 1 and December 1, 2024, were analyzed. Patients were divided into two groups: Group F (n=97), who received spinal anesthesia combined with femoral nerve block (FNB), and Group C (n=102), who received spinal anesthesia with standard analgesia only. Preoperative and 24-hour postoperative NLR values were obtained from complete blood counts. Statistical analysis was performed using IBM SPSS Statistics 26.0. The independent samples t-test or Mann-Whitney U test was used, depending on data distribution. Baseline NLR values were similar between groups (Group C: 1.85, Group F: 2.08; p=0.255). Postoperatively, NLR increased significantly in both groups; however, the increase was significantly lower in Group F (Group C: 9.15 vs. Group F: 5.58; p<0.001). The percentage increase in NLR was 356.58% in Group C and 170.99% in Group F (p<0.001), indicating a markedly attenuated inflammatory response in patients receiving FNB. FNB significantly reduces the postoperative rise in NLR in patients undergoing TKA under spinal anesthesia. This effect may result from both superior pain control and the anti-inflammatory properties of local anesthetics. These findings suggest that FNB may enhance recovery beyond analgesia by modulating the surgical stress response.