High Versus Low Adductor Canal Block

The investigators will be comparing the efficacy of two different techniques for performing an adductor canal block to the saphenous nerve as a part of the multimodal pain control regimen for total knee arthroplasty. The investigators will be comparing a "low adductor canal block" in which the surgeon administers local anesthetic to the distal aspect of the nerve from the operative site to a "high adductor canal block" in which the anesthesiologist administers the local anesthetic more proximally along the thigh using ultrasound guidance. The investigators will power the study for non-inferiority to compare the newer "low" block to the more commonly performed and more widely studied "high" block.

Study Design: Prospective RCT

Study Question- Does a surgeon administered intra-operative adductor canal block ("Low-ACB") provide non-inferior post-operative pain relief relative to anesthesia administered, ultrasound guided adductor canal block ("High-ACB").

Hypothesis- Surgeon administered Low-ACB provides non-inferior pain relief relative to anesthesia administered High-ACB.

Study Groups-

1. US Guided, Anesthesia Administered Adductor Canal Block ("High ACB")
2. Intra-Operative, Surgeon Administered Adductor Canal Block ("Low ACB")

Randomization- Cluster Randomization There will be two surgeons collecting data for this study; Surgeon A (principal investigator) \& Surgeon B. Each surgeon will begin collecting data on opposite arms of the study. Surgeon A will perform 35 consecutive High-ACB knees while Surgeon B performs 35 Low-ACB knees. After performing 35 knees under either the High-ACB or Low-ACB protocol, Surgeon A and Surgeon B will switch arms and perform an additional 35 consecutive knees in the opposite arm. At trial's end, each surgeon will have performed 35 TKAs using the High-ACB and Low-ACB protocol yielding a total of 70 patients in each arm.

Participant Timeline:

The investigators will interact with patients and collect specific data at a limited number of office visits as outlined below. All office appointments will take place at the Carilion Clinic Institute for Orthopaedics and Neurosciences.

1. Pre-Op Appointment- Thorough informed consent will be obtained at this visit. Patient will be sent home with consent form to review further and discuss with family.
2. Day of Surgery- Prior to surgery, operative team will go over consent one final time and obtain signature if patient consents.
3. Post-Op Admission- Standard post-op protocol will be followed. Data will be collected from this admission from the Epic EMR as above.
4. Discharge Home- Patient will keep pill journal for opioid narcotics taken each day as well as a recording their daily pain score prior to bed.
5. 2 Week F/U Appointment- PROMIS, KOOS Jr. and VAS scores as well as physical exam data recorded. This requires no additional time as this is part of routine post TKA follow up.
6. Home 2-6 Weeks- Patient will keep pill journal for opioid narcotics taken each day as well as a recording their daily pain score prior to bed.
7. 6 Week F/U Appointment- PROMIS, KOOS Jr. and VAS scores as well as physical exam data recorded. This requires no additional time as this is part of routine post TKA follow up.

At this point, the patient has completed their participation in the study and will continue follow up as scheduled without further data collection.

Technical Details:

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 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.\[3\] 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.

Anesthesia Administered Group 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.

Eligibility Criteria:
Inclusion Criteria:

* All patients undergoing unilateral primary TKA for primary osteoarthritis
* Age over 18

Exclusion Criteria:

* Pre-operative narcotic use
* Bilateral procedure
* Non-Primary arthroplasty
* Workman's comp
* Inability to have spinal anesthesia (blood thinners)
* Unsuccessful spinal anesthesia
* Inflammatory or Post Traumatic arthritis
* ASA score of 4
* Pregnancy