Adductor Canal Block With Periarticular Injection and IPACK (ACB/PAI/IPACK) Versus Periarticular Injection (PAI)

Total knee arthroplasties (TKA) are severely painful surgeries that require optimal pain control to ensure expeditious recovery and discharge. Nerve blocks, such as the femoral and sciatic nerves, are instrumental in effectively providing pain relief and improving patient satisfaction. However, though pain scores notably decreased with the introduction of nerve blocks, motor blockade rendered these patients immobile and may pose a fall risk early in the post-operative period. The advent of ultrasound introduces newer block techniques with adequate analgesia without the cost of motor blockade.

The adductor canal block serves as an alternative to the femoral or sciatic nerve blocks in providing anterior knee analgesia without significantly compromising quadriceps strength. However, patients' posterior knee compartment remains an issue for pain control. Sciatic and posterior tibial nerve blocks were implemented but again, results in motor blockade. A small percentage of sciatic nerve block cases also exhibit foot drop due to peroneal nerve injury. Alternatively, as a sensory block, the periarticular injection (PAI) proves to hasten ambulation and recovery after TKA. The PAI blind injection into the posterior capsule seems to aid in pain control of the posterior compartment and reduces the total number physical therapy sessions.

Injection in the interspace between the Popliteal Artery and Capsule of the posterior Knee (IPACK) provides an alternative to the PAI blind technique for analgesia in the posterior compartment. The IPACK block is not a nerve block, but rather infiltrates the area between the popliteal artery and femur. This area is rich with sensory nerve fibers from the posterior capsule of the knee, which originates from the sciatic and posterior tibial nerve. In this prospective study, we will compare pain scores between the three groups: ACB/PAI/IPACK, ACB/IPACK and PAI only. We will determine whether there is a difference between groups in NRS pain score with ambulation 24 hours post block administration.

Inclusion criteria

• Patients with osteoarthritis scheduled for a primary either partial or total knee arthroplasty with a participating surgeon
• Age 18 to 80 years
• Planned use of regional anesthesia
• Ability to follow study protocol
• English speaking (secondary outcomes include questionnaires validated in English only)
• Patients of participating surgeons

Exclusion criteria

• Hepatic or renal insufficiency
• Younger than 18 years old and older than 80
• Patients undergoing general anesthesia
• Allergy or intolerance to one of the study medications
• BMI > 40
• Diabetes
• ASA of IV
• Chronic gabapentin/pregabalin use (regular use for longer than 3 months)
• Chronic opioid use (taking opioids for longer than 3 months, or daily oral morphine equivalent of >5mg/day for one month)
• Patients with severe valgus deformity and flexion contracture