Endoscopy Clinical Trials

Total knee arthroplasty (TKA) is associated with substantial postoperative pain and opioid requirements, making effective multimodal analgesia essential for early mobilization, functional recovery, and reduction of opioid-related adverse events \[1,2\]. Adductor canal block (ACB) has become a key component of enhanced recovery after surgery (ERAS) protocols because it provides effective anterior knee analgesia while largely preserving quadriceps muscle strength \[2-4\]. However, analgesic efficacy after ACB remains variable, and some patients require rescue opioid analgesia despite technically successful block placement \[5\]. Although ultrasound guidance improves block accuracy, factors such as tissue depth, anatomical variations, saphenous nerve visibility, and injectate spread pattern may influence clinical outcomes \[6,7\]. Prospective evidence regarding the predictive value of these ultrasound-derived parameters for ACB analgesic failure remains limited. Therefore, this study aims to evaluate whether preoperative ultrasound-derived tissue and target parameters-including skin-to-target depth, subcutaneous fat thickness, muscle thickness, saphenous nerve visibility, and injectate spread pattern-can predict ACB analgesic failure and early postoperative analgesic outcomes following TKA.