Combined iPACK and adductor canal block versus two-level erector spinae plane block in elderly patients undergoing total knee arthroplasty: a randomized, triple-blinded clinical trial

Effective postoperative pain management after total knee arthroplasty (TKA) in elderly patients is challenging because of their increased susceptibility to opioid-related adverse events. Motor-sparing regional anesthesia techniques such as the adductor canal block (ACB), the interspace between the popliteal artery and the posterior capsule of the knee (iPACK) block, and the erector spinae plane block (ESPB) may improve analgesia while preserving quadriceps strength and modulating the systemic stress response. In this single-center, prospective, randomized, triple-blinded trial, 60 patients aged 65–100 years undergoing primary TKA under spinal anesthesia were allocated to receive either combined iPACK + ACB (20 mL of 0.2% ropivacaine for each block) or a two-level lumbar–sacral ESPB at L1 and S1 (20 mL of 0.2% ropivacaine at each level). The primary outcome was total opioid consumption within 48 h, expressed in morphine milligram equivalents (MME). Secondary outcomes included time to first rescue opioid, Numerical Rating Scale (NRS) pain scores, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and quadriceps strength (Medical Research Council scale). Compared with two-level ESPB, iPACK + ACB significantly reduced total opioid consumption (9.7 ± 5.4 vs 12.9 ± 6.9 mg MME; p = 0.0348) and prolonged the time to first rescue opioid (9.3 ± 4.3 vs 8.5 ± 3.4 h; p = 0.0263). NRS scores were lower at 8 h (2.6 ± 0.8 vs 3.3 ± 0.7; p = 0.0037), with no relevant differences thereafter. NLR at 24 h was significantly lower with iPACK + ACB (2.20 ± 0.41 vs 2.61 ± 0.45; p = 0.0015), whereas PLR did not differ. Quadriceps strength remained preserved (MRC 5) in both groups. In elderly patients with TKA, combined iPACK + ACB provides more effective, opioid-sparing analgesia and attenuates the early inflammatory response compared with two-level lumbar–sacral ESPB, without compromising quadriceps motor function. Trial registration: ClinicalTrials.gov Identifier: NCT06470542.