Migration Rate for Continuous Adductor Canal Block Catheters After Primary Total Knee Arthroplasty Surgery: a Comparison Between the Interfascial Plane Between SArtorious Muscle and FEmoral Artery (ISAFE) and the Out Of Plane Parallel to Saphenous Nerve (OOPS) Techniques: The ISAFE x OOPS Trial

Joint replacement surgeries are often followed by significant early postoperative pain, necessitating effective pain management with minimal side effect. Over the years, various analgesic modalities have been employed, but each comes with its own limitations. Opioids are a commonly used class of oral and intravenous/intramuscular pain medications that provide excellent analgesic control, yet are associated with side effects, such as nausea, vomiting, sedation, constipation and respiratory depression. Non-steroidal anti-inflammatory drugs (NSAIDs) are frequently used as adjuvants alongside acetaminophen, but use is contraindicated in patients with bleeding disorders, gastric ulcers, or renal or liver impairment.

Peripheral nerve blocks have emerged as a highly effective pain management option with minimal side effects. Historically, femoral nerve blocks were used to control pain after knee replacement surgeries; however, the associated motor block delayed patient mobilization and hospital discharge. In contrast, adductor canal blocks (ACB) have demonstrated effective pain relief without causing important quadriceps weakness. While ACB is generally safer, it can be associated with complications such as vascular puncture, nerve injury, and, in rare cases, local anesthetic systemic toxicity (LAST). The use of ultrasound guidance, along with proper technique, significantly reduces the likelihood of these complications.

One limitation of any single-shot nerve block is the variability in the duration of its effect, depending on the local anesthetic used. CACBs address this issue by providing prolonged length for ACB and longer pain control. However, the insertion of CACB catheters carries similar risks to those of single-shot nerve blocks, in addition to the potential for catheter migration outside the adductor canal, which leads to loss of effectiveness. With proper techniques to increase safety and effectiveness, CACB holds great potential as a mainstay of postoperative analgesia for knee arthroplasty patients.

At Mount Sinai Hospital - Sinai Health System, CACB has become standard practice for knee arthroplasty patients. The catheter tip is placed near the saphenous nerve in the mid-thigh region under ultrasound guidance. The ISAFE (Interfascial plane between the SArtorius muscle and FEmoral artery) approach is used for catheter insertion, which has been shown to reduce catheter dislodgement by 26.3% compared to the conventional technique. Another technique for CACB catheter insertion, named OOPS (Out Of Plane parallel to Saphenous nerve), has demonstrated a lower incidence of catheter migration outside the adductor canal when compared to the conventional insertion technique. In the OOPS technique, the catheter is inserted through an ultrasound guided out-of-plane manner, parallel to the saphenous nerve, ensuring that it remains securely within the adductor canal, reducing the likelihood of dislodgement with patient movement.

SIGNIFICANCE Currently, no published studies directly compare the migration rates of the ISAFE and OOPS techniques for CACB catheter insertion. Effective postoperative analgesia promotes early ambulation, accelerating recovery and potentially reducing hospital stays. Techniques that minimize catheter migration can lead to better outcomes, while inadequate pain control remains a significant factor contributing to prolonged hospital stays. Optimized inserted CACB catheters facilitate same-day discharge and may help reduce healthcare costs.