The pericapsular nerve block is a regional anesthetic technique described in 2018, developed primarily in total hip arthroplasties for postoperative analgesia with motor sparing benefits. The block is thought to provide more complete analgesia to the hip by depositing local anesthetic within the myofascial plane of the psoas muscle and superior pubic ramus.The indications for total hip arthroplasties often include degenerative hip disease and traumatic hip fractures. These indications for surgery are relatively common in the elderly population and are associated with significant morbidity and mortality.Operative intervention, such as total hip arthroplasties has also been associated with significant pain. Historically, the most commonly performed peripheral nerve blocks include lumbar plexus block, a femoral nerve block, or a fascia iliaca compartment block to manage post-operative analgesia. With the understanding that additional articular branches these blocks will provide incomplete analgesia to the hip and may also predispose the patient to fall due to weakness of the quadriceps muscles.Therefore the ideal block technique should provide complete analgesia of the hip joint and without muscle weakness. The ultrasound-guided pericapsular nerve block block allows for coverage of the hip joint, targeting the proximal articular branches that innervate the joint capsule. This proximal approach via ultrasound guidance can confer several advantages over a femoral nerve block by providing more complete analgesia to the hip joint. Additionally, the motor function of the involved extremity should be spared. The pericapsular nerve block block can be used alone as a primary analgesic or in conjunction with other forms of anesthesia during surgery or in the perioperative period. For lateral surgical incisions, a supplemental lateral femoral cutaneous nerve block provides additional coverage.The femoral nerve is among the largest branches of the lumbar plexus. The femoral nerve arises from the ventral rami of the Lumeber 2, Lumber 3, and Lumber 4 spinal nerves, and enters the femoral triangle inferior to the inguinal ligament. The femoral nerve is the most lateral of the structures within the triangle, which also contains the femoral artery and femoral vein at its medial end. The femoral nerve splits into anterior and posterior divisions that originate near the level of the circumflex artery. The anterior division gives rise to the medial femoral cutaneous nerve and innervates the sartorius muscle. The posterior division gives rise to the saphenous nerve and provides innervation to quadriceps femoris muscle. In addition to motor innervation, the femoral nerve provides sensation to the anterior thigh and knee and the medial lower extremity below the knee. The saphenous nerve is a femoral nerve branch that is directly responsible for sensation to the medial lower leg and foot. The saphenous nerve can be blocked separately at the level of the adductor canal, and several more distal sites. The adductor canal is a musculoaponeurotic tunnel found in the mid-thigh and extends from the femoral triangle to the adductor magnus.Due to the anatomical connection, the femoral nerve within the femoral triage may potentially be affected by proximal or high-volume adductor canal blocks.
