Analgesic effect of local anesthesia in total knee arthroplasty: protocol of a randomized controlled clinical trial

Postoperative pain management remains a critical determinant of functional recovery following total knee arthroplasty (TKA). While local infiltration analgesia (LIA) is commonly employed, its clinical utility is limited by inconsistent analgesic duration (median duration of 8-12 hours), technical variability among surgeons, and systemic toxicity risks associated with high-volume injections. This phase II randomized controlled trial evaluates a dual-optimization strategy combining anatomic mapping-guided periarticular cutaneous nerve (PCN) blockade with a sustained-release triamcinolone-ropivacaine formulation to address these limitations. In this single-center, assessor-blinded, 2 × 2 factorial design, 120 adults undergoing primary unilateral TKA were randomized to four intervention arms: Group 1: Conventional iPACK (interspace between the popliteal artery and posterior knee capsule) site + novel formulation (1% ropivacaine + 40 mg triamcinolone); Group 2: PCN block site + standard formulation (1% ropivacaine + 5 mg dexamethasone); Group 3: PCN block + novel formulation; Group 4: Control (iPACK + standard formulation). Triamcinolone acetonide replaces dexamethasone in the new formulation due to its prolonged anti-inflammatory effect and demonstrated efficacy in periarticular analgesia. Primary endpoints included: resting/movement-induced pain intensity (Visual Analog Scale) at 6, 24, and 48 h postoperatively, cumulative opioid consumption (morphine milligram equivalents), functional recovery metrics (knee flexion angle, Timed Up-and-Go test). Secondary outcomes assessed safety through adverse event rates (infection, neurologic symptoms, hemodynamic instability). Anatomic mapping-guided PCN blockade combined with triamcinolone-ropivacaine formulation significantly improves postoperative analgesia and functional outcomes compared to conventional LIA techniques. This dual-optimization approach may redefine periarticular infiltration standards in TKA, particularly for patients at high risk of opioid-related complications.