Femoral Versus Adductor Canal Continuous Peripheral Nerve Blocks for Knee Arthroplasty

Study Summary

Patients typically experience moderate-to-severe pain following knee arthroplasty that is usually treated with a combination of oral and intravenous analgesics and enhanced by continuous peripheral nerve blocks. There are currently two locations to place a perineural catheter to provide analgesia following knee arthroplasty: a femoral nerve catheter and an adductor canal catheter. Both have been demonstrated to be effective following knee arthroplasty. However, it remains unknown if one location is superior to the other; or, more accurately, what the relative benefits are to each technique. While femoral CPNB has many benefits, one of the challenges of using this technique is that there is a decrease in quadriceps muscle strength which can be a limiting factor for rehabilitation. In contrast, the adductor canal catheter affects only the vastus medialis. This block may lessen block-induced quadriceps weakness following knee arthroplasty compared with a femoral infusion. The investigators hypothesize that compared with femoral perineural local anesthetic infusion, an adductor canal infusion is associated with a shorter time until four discharge criteria are met: (1) adequate analgesia; (2) independence from intravenous analgesics; (3) ability to ambulate 30 m; and (4) ability to stand, walk 3 m, and return to a sitting position without another's assistance.

Primary Outcome

Discharge readiness is the number of hours until meeting the following 4 criteria: (1) adequate analgesia (defined as pain less than 4 on a NRS of 0-10); (2) independence from intravenous analgesics; (3) ability to ambulate 30 m and (4) ability to stand, walk 3 m, and return to a sitting position without another's assistance.

Interventions

• DRUG Control: Femoral perineural local anesthetic infusion
• DRUG Experimental: Adductor Canal perineural local anesthetic infusion