Modulation of postoperative inflammatory response in total knee arthroplasty: Impact of iPACK block on neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios in a randomized controlled trial

Abstract

Background

The neutrophil-to-lymphocyte ratio (NLR) is a marker of systemic inflammation and surgical stress. This randomized controlled trial (RCT) evaluated the effect of the infiltration between the popliteal artery and the capsule of the knee (iPACK) block with ropivacaine on postoperative NLR and analgesic outcomes in total knee arthroplasty (TKA) under spinal anesthesia.

Methods

Sixty TKA patients were randomized to receive either a sham block (control, n = 30) or an iPACK block with 20 mL of 0.2 % ropivacaine (n = 30). The primary outcome was NLR at 12 h postoperatively. Secondary outcomes included NLR at 24 and 48 h, platelet-to-lymphocyte ratio (PLR), opioid consumption, time to first rescue analgesia, and numeric rating scale (NRS) pain scores at multiple postoperative time points.

Results

The iPACK group had significantly lower NLR at 12 h (16.87 ± 4.41 vs. 23.95 ± 8.03, p < 0.0001), 24 h (2.27 ± 0.83 vs. 4.22 ± 0.59, p < 0.0001), and 48 h (1.80 ± 0.78 vs. 2.81 ± 1.16, p = 0.0002). PLR was lower at all time points (p < 0.0001), opioid use was reduced (4.6 ± 1.0 mg/kg vs. 14.2 ± 1.9 mg/kg, p < 0.0001), and time to first rescue analgesia was prolonged (7.0 ± 1.6 vs. 3.6 ± 0.7 h, p < 0.0001). NRS scores were significantly lower up to 24 h (p < 0.0001), with the greatest difference at 12 h (−1.8 ± 0.2, 95 % CI -2.1 to −1.4, p < 0.0001).

Conclusions

The iPACK block with 0.2 % ropivacaine significantly reduces postoperative inflammation, improves pain control, and decreases opioid consumption in TKA. These findings support its inclusion in multimodal analgesia protocols to enhance recovery and reduce systemic inflammation.

Trial registration

Registered at ClinicalTrials.gov (NCT06304298)