Femoral Triangle and Adductor Canal Blocks Versus Femoral Nerve Block for Total Knee Arthroplasty

The aim: to evaluate femoral triangle and adductor canal blocks and femoral nerve block regarding the postoperative analgesic efficacy, extent of motor blockade, ability of early ambulation in patients following primary total knee arthroplasty.

Primary Hypothesis: femoral triangle and adductor canal blocks and femoral nerve block provide similar postoperative pain relieving effect after primary total knee arthroplasty.

Secondary Effects: femoral triangle and adductor canal blocks provide better ability of early ambulation after primary total knee arthroplasty.

The objectives:

• To compare postoperative pain control effects between femoral triangle and adductor canal blocks and femoral nerve block groups of patients after primary total knee joint replacement surgery.
• To assess the ability of early ambulation and extent of motor blockade after primary total knee joint replacement surgery between the groups of patients.
• To estimate opioid consumption and its adverse effects in femoral triangle and adductor canal blocks and femoral nerve block groups of patients after primary total knee arthroplasty.
• To compare patients postoperative satisfaction rates between femoral triangle and adductor canal blocks and femoral nerve block groups of patients after primary total knee arthroplasty.

Methods:

The prospective, double-blinded study includes American Society of Anesthesiologists (ASA) physical status I-III in preoperative assessment, aged 18-90 years, admitted for primary total knee arthroplasty. Preoperatively patients will be blindly randomized into one of two groups: femoral triangle and adductor canal blocks group and femoral nerve block group. Group assignment will be concealed by opaque envelopes that will be opened only after the enrollment. The anesthesiologist performing the block will be aware of the treatment, but the participant and outcomes assessor will be blinded to the group assignment.

All blocks will be performed by the anesthesiologist under the guidance of a linear ultrasound transducer probe. Femoral nerve block will be performed at the proximal part of the femoral triangle by 20 mL of 0.125% bupivacaine injection. Femoral triangle and adductor canal blocks will be performed together. Femoral triangle block will be performed at the level where the medial border of the sartorius muscle intersects the medial border of the adductor longus muscle with injection of 10 mL of 0.125% bupivacaine. Local anesthetic will be injected laterally to the femoral artery. Adductor canal block will be performed at the level where the femoral vessels (artery and vein) dive deeper from the sartorius muscle with injection of 10 mL of 0.125% bupivacaine. Local anesthetic will be injected under the femoral artery.

During the perioperative period all patients from both groups will receive a standardized anesthetic and analgesic. Premedication of midazolam 2.5-5 mg and dexamethasone 4 mg will be given to all patients and a slow fluid infusion of crystalloids with 1 g of tranexamic acid and 10 mg of ketamine will be started once as an intravenous cannula will be placed. Spinal anesthesia after identification of the subarachnoid space will be performed with 15 mg of levobupivacaine. After that, femoral triangle and adductor canal blocks or femoral nerve block (depending on the group of patients) will be performed under the ultrasound guidance. Patients will be sedated with intravenously administered propofol during the surgery. The local infiltration analgesia will be performed by the surgeon at the end of surgery with combination of 30 mL of 0.5% bupivacaine, 0.3 mL of 0.1% adrenaline and 90 mL of 0.9% sodium chloride. After the surgery patients will be transferred to the post-anesthesia care unit (PACU).

During the postoperative period for analgesia NSAIDs will be available to both groups of patients. NSAIDs such as dexketoprofen 50 mg will be administered 2 times and acetaminophen 1 g will be administered 3 times per day. Opioids will also be available to patients as intramuscular boluses of pethidine 50 mg or morphine 10 mg without restriction and administered for moderate or severe pain (VAS pain score of 5 or greater out of 10).

Postoperative pain control efficacy will be assessed at 3, 6, 24 and 48 hours after surgery using visual analogue scale (VAS) from 0 to 10 (0 - no pain, 10 - worst imaginable pain) at rest, during active and passive 45 degree knee flexion. The requirement of additional analgesics and their adverse effects (if any) will be recorded.

The extent of motor blockade will be evaluated at 3, 6, 24, 48 hours after surgery. Patients will be asked to flex the foot, to flex the knee and to lift up the straight leg. The possible leg motion at 3, 6, 24 and 48 hours postoperatively will be assessed with Bromage scale grades: Grade I - free movement of legs and feet, Grade II - just able to flex knees with free movement of feet, Grade III - unable to flex knees, but with free movement of feet, Grade IV - unable to move legs or feet.

Patients ability of early ambulation will be evaluated using Timed Up and Go (TUG) test at 24 and 48 hours after surgery. To do the TUG test, patients will have to sit down on the bed, get up from the bed, walk 3 meters forward, turn, walk back 3 meters to the bed and sit down. The time taken by a patient to perform this test will be calculated with a chronometer.

After the conversation with each patient and assessment of postoperative pain control efficacy, extent of motor blockade, ability of early ambulation, the rate of patient satisfaction will be evaluated using a 10 point scale from 0 (completely unsatisfied) to 10 (totally satisfied) at 3, 6, 24, 48 hours after surgery.

The length of hospital stay and rate of complications (if any), including falls, local anesthetic toxicity or neurological complications, will be recorded in both groups of patients.

According to study protocol, both groups of patients will be compared in terms of postoperative pain control, opioid consumption, extent of motor blockade, ability of early ambulation, patients satisfaction rates over the time of clinical recovery and the length of hospitalization.

Inclusion criteria

• Patients undergoing primary unilateral total knee arthroplasty under the spinal anesthesia.
• Age 18 - 90 years.
• Patients conformed to American Society of Anesthesiologists (ASA) physical status I-III in preoperative assessment.
• Ability to follow the study protocol.

Exclusion criteria

• Inability or refusal to follow the study protocol.
• American Society of Anesthesiologists (ASA) physical status classification of IV or higher.
• Coagulopathy.
• Pre-existing lower extremity neuromuscular disorders.
• Local infection over the injection site.
• Allergy or contraindications to the drugs used in the study (local anesthetics, NSAIDs, opioids).
• Chronic opioid use.
• Other type of anesthesia.