TIPS Block vs Dual Subsartorial Block

Introduction: Maximum pain control with regional analgesic techniques after total knee arthroplasty (TKA) is crucial for early rehabilitation after surgery. The ideal regional anesthetic technique should cover all the essential innervations of the knee joint involved in each surgical step without causing motor blockade.

The investigators hypothesize that local anesthetic injection superior to the sartorius at the level of the femoral triangle may block the intermediate femoral cutaneous nerve (IFCN) which is responsible for the innervation of the anterior thigh and the proximal part of the parapatellar incision used for TKA and provide superior analgesia when added to dual subsartorial blockade in cases of TKA.

Patients will be divided into 2 groups. Group TIPS; patients will receive double level subsartorial block and suprasartorial LA injection at the level of the distal FT after induction of general anesthesia (GA). Group Dual; patients will receive double level subsartorial canal block after induction of GA.

Upon arrival to the operating room (OR), a multichannel monitor will be attached to patients, followed by the administration of 2 mg midazolam IV after securing an IV cannula. Induction of anesthesia will be carried out with 2 mic/kg fentanyl, 2 mg/kg propofol and 25 mg atracurium followed by insertion of a proper size laryngeal mask airway (LMA). Patients will be randomly allocated into 2 groups by a computer generated program.

Group Dual: Patients will receive a combination of femoral triangle block and distal ACB. Femoral triangle block will be given just 1-2 cm proximal to the apex of the femoral tringle which is the point at which the medial border of the sartorius muscle (STM) meets the medial border of the adductor longus muscle (ALM). Ten ml of 0.25 % bupivacaine mixed with 2 mg dexamethasone will be injected just below the STM. Another 20 ml of 0.25 % bupivacaine mixed with 2 mg dexamethasone will be injected in the lower one-third of the adductor canal. At this level, femoral vessels dip into the opening of the adductor hiatus to become popliteal vessels. Sonoanatomy of this region shows the adductor magnus muscle (AMM) posteromedially, vastus medialis muscle (VMM) anterolaterally, and the STM medially.

Group TIPS: Patients will receive dual injection subsartorial block and a third injection of 10 ml of 0.25 % bupivacaine superficial to the sartorius under the facia lata.

Postoperatively, multimodal analgesia regimen will be continued in the form of paracetamol 1 g /8 hours and ketorolac 30 mg /8 hours intravenously for 24 hours. Intravenous morphine patient controlled analgesia will be started after induction of GA at a concentration of 0.5 mg/ml without a background infusion on demand dose of 1 mg with a lockout interval of 10 minutes. Resting and dynamic VAS assessment will be carried out every 4 hours during the 24 hour follow up period. Total postoperative morphine requirements will be measured during the postoperative follow up period. Postoperative functional outcome will be assessed using the Timed Up and Go (TUG) test and the 30-second Chair Stand Test (30s-CST).