High & Low Adductor Canal BlockHigh Versus Low Adductor Canal Block

In the pre-operative cohort, the adductor canal block is administered by anesthesia staff immediately prior to patient transport to the operating room. The thigh is prepped with cholorhexidine at the midpoint between the anterior superior iliac spine and the patella and sterile drapes are applied. An ultrasound probe is then used to localize the adductor canal and confirm that the femoral artery, femoral vein and saphenous nerve can be visualized deep to the sartorious. The probe is moved proximally or distally until the neurovascular bundle is centered under the sartorius. A 20cc syringe with a blunt tip 1.5in 18ga needle is then used to inject 15cc of 0.5% ropivocaine. Following this, the wound is prepped and draped in usual sterile fashion for the arthroplasty procedure.

Surgeon Administered Group In the intra-operative cohort, the block will be administered after the final components are in place and cement debris is removed. The knee joint is irrigated with dilute hibiclens or betadine followed by pulsatile lavage per institutional protocol. A blunt tip 1.5in 18ga needle was then used to administer 15cc of 0.5% ropivocaine.. The location of the saphenous nerve as it exits the adductor canal will be estimated to be 1.5x the TEA proximal to the medial epicondyle in men and 1.3x the TEA proximal in women as described by Kavolus et al. The 60cc of the anesthetic will then injected through the vastus medialis musculature in a field extending from 1cm proximal to one cm distal to the assumed location of the nerve with the needle directed in from 20° to 45° medial. The wound is then irrigated pulsatile lavage one final time and closed in layered fashion.

The drug will be administered in the same dosage in both arms. The location of the injection will vary by arm.