The Efficacy of Different Volumes for Ultrasound-Guided Adductor Canal Block for Postoperative Analgesia Management After Total Knee Arthroplasty Surgery

Knee arthroplasty is one of the most common orthopedic procedures. Patients may complain severe pain due to the surgical trauma and the prosthesis. Opioid agents are commonly used for analgesia management. However, opioids have adverse effects such as nausea, vomiting, sedation and respiratory depression. Peripheral nerve blocks such as femoral block, adductor canal block (ACB) may be performed to reduce opioid consumption and opioid-related side effects.

Selective blockade of the saphenous nerve in the adductor canal for knee surgery provides effective analgesia without quadriceps muscle weakness. This is an important advantage of ACB since it there is no motor blockade in the postoperative period. Blocking of the motor branches leads to delaying of the mobilization and it increases the patient's falling risk. ACB, targets the saphenous nerve and the vastus medialis branch which are the two largest sensorial nerves of the femoral nerve that innervates the knee. ACB blocks the articular branches of the obturator nerve at the same time. Since the ACB is performed at the distal site of thigh it does not target majority of the efferent branches of the quadriceps muscle, therefore the strength of this muscle may not be affected. ACB is usually performed with a volume of 10-30 ml and studies may be needed including different volumes to understand its effectiveness.

The aim of this study is to compare the different volumes (20 ml, 30 ml, and 40 ml) of US-guided ACB for postoperative analgesia management after total knee arthroplasty. The primary aim is to compare postoperative opioid consumption and the secondary aim is to evaluate postoperative pain scores (VAS), motor blockage, the first mobilization time, and adverse effects related with opioids (allergic reaction, nausea, vomiting).