US Guided GNB vs Saline Injection for TKA

Do ultrasound-guided genicular nerve blocks with 0.5% bupivacaine provide improved knee analgesia for patients recovering from total knee replacement surgery compared to saline injection?

Hypotheses:

The investigators hypothesize that the combination of ultrasound-guided adductor canal block (ACB) and genicular nerve block will achieve lower opioid consumption and therefore lead to decreased systemic side effects and improved overall satisfaction compared to ultrasound-guided saline injection for patients undergoing minimally invasive elective total knee arthroplasty (TKA).

The study medication and protocol will consist of Group 1 (Active) - ultrasound-guided adductor canal blockade with 10 ml of 0.25% bupivacaine and ultrasound-guided genicular nerve blocks with 6 ml of 0.5% bupivacaine, and Group 2 (Control) - ultrasound-guided adductor canal block with 10 ml of 0.25% bupivacaine and ultrasound-guided genicular nerve blocks with 6 ml of normal saline. The surgeon will be blinded to the subjects study arm assignment.

An ultrasound-guided ACB will be performed at the level of the mid-thigh of the leg halfway between the superior anterior iliac spine and the patella. The femoral artery, femoral vein, saphenous nerve will be visualized by ultrasonography and the expansion of the adductor canal will be recorded. Sensory assessment of the saphenous distribution will be performed at 30 minutes. The ultrasound-guided genicular nerve block will be performed at the site of the superior lateral, the superior medial, and the inferior medial genicular nerves. The superior lateral genicular nerve is located at the confluence of the lateral femoral shaft and the lateral femoral condyle (in the anteroposterior plane) and at the midpoint of the femur (in the lateral plane). The superior medial genicular nerve site is located at the confluence of the medial femoral shaft and the medial femoral condyle (in the anteroposterior plane) and at the midpoint of the femur (in the lateral plane). The inferior medial genicular nerve site is located at the confluence of the medial tibial shaft and the tibial flare (in the anteroposterior plane) and the midpoint of the tibia (in the lateral plane). Color Doppler will be used to identify the arterial structures which serve as landmarks for the corresponding nerves. All nerve blocks will be performed by a study team physician.

Postoperative follow-up will be done by study team member blinded to the group allocation. The dosing of oxycodone/hydrocodone-acetaminophen will be as needed with management goal of a Visual Analog Scale (VAS) score of ≤ 4. Patients with pain not managed by oral agents will receive IV medication. Patients will be visited during their hospital stay every six hours until discharge to record pain scores, opioid consumption, and patient satisfaction. In addition, patients will be given a pain diary to record (VAS) pain scores every six hours until hospital discharge.

A study team member will follow up patients by telephone (if discharged prior to) at 48 hours, 72 hours.

Eligibility Criteria:
Inclusion Criteria:

* Participants 40 to 85 years old who are presenting for minimally invasive total knee arthroplasty under spinal anesthesia and are candidates for peripheral nerve blocks.
* Minimally invasive is defined as custom modified instrumentation, a quadriceps sparing arthrotomy that does not extend beyond 1cm proximal to the patella and surgical techniques that focus on soft tissue protection.

Exclusion Criteria:

* Patient refusal
* American Society of Anesthesiologists physical status classification of 4 or higher
* Pre-existing neuropathy in the femoral or sciatic distribution
* Coagulopathy
* Infection at the site
* Chronic opioid use (greater than 3 months)
* Pregnancy
* Medical conditions limiting physical therapy participation
* Any other contra-indication to regional anesthesia