Ultrasonographic Predictors of Adductor Canal Block Effectiveness in Total Knee Arthroplasty

Konya City Hospital623 enrolled

Overview

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.

Study Type

OBSERVATIONAL

Enrollment

623

Conditions

Arthroplasty, Replacement, Knee Nerve Block Assessment Pain, Postoperative Arthroscopy

Interventions

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

Inclusion Criteria: * Age ≥18 years * Scheduled for elective primary unilateral total knee arthroplasty under spinal anesthesia * American Society of Anesthesiologists (ASA) physical status I-III Exclusion Criteria: * Daily opioid use or chronic pain syndrome * Diabetic or other clinically diagnosed peripheral neuropathy * Coagulopathy * Infection at the injection site * Known allergy or hypersensitivity to local anesthetics * Revision total knee arthroplasty * Conversion from spinal anesthesia to general anesthesia during surgery * General anesthesia as the planned anesthetic technique

Outcomes

Primary Outcomes

ACB Failure

ACB analgesic failure will be defined as the requirement for rescue analgesia during the first 24 hours after block administration, with intravenous tramadol (1 mg/kg) administered to patients with an NRS pain score ≥4.

Time frame: 0-24 hours

Secondary Outcomes

Secondary outcome

1\. Numeric Rating Scale (NRS) Pain Scores NRS pain scores at rest and during a standardized movement (active 90° knee flexion) will be recorded at postoperative 1, 6, 12, and 24 hours.

Time frame: 0-24 hour

Tramadol Consumption

2\. Total Tramadol Consumption Total tramadol consumption (mg) during the first 24 hours following ACB administration will be recorded.

Time frame: 0-24 Hours