Adductor Canal Block and IPACK Block vs Adductor Canal Block and the Gastrosoleus Interfascial Block After Total Knee Arthroplasty

Total knee arthroplasty (TKA) is a surgical procedure commonly known for its association with sever postoperative pain. This pain can affect quality of recovery by restricting patient's ability to mobilize early and participate effectively in rehabilitation, which eventually will prolong hospital stays and increase healthcare costs. Also chronic postsurgical pain may complicate inadequately managed postsurgical pain.

Hence the need for exploring different analgesic modalities has evolved involving different techniques either regional anesthesia or systemic analgesics.

Peripheral nerve blockade was found to achieve adequate postoperative pain relief, and techniques such as sciatic nerve block, femoral nerve block and adductor canal block have been introduced.

Adductor canal block (ACB) has been shown to decrease pain significantly and thereby opioid consumption with minimal effect on quadriceps function.

Though ACB provides analgesia to the peripatellar and intra-articular aspect of knee joint, it does not relieve posterior knee pain which may compromise satisfactory pain relief.

Infiltration of the interspace between popliteal artery and the capsule of posterior knee (IPACK) by local anesthetics has been achieved by ultrasound and was found to provide significant posterior knee analgesia. Its technique was described by Elliott et al.

Recently the gastrosoleus interfascial plane block (GIP) was introduced in 2023 by Abraham et al which targets the fascial plane between the soleus muscle and the medial belly of the gastrocnemius muscle.

All patients will be preoperatively assessed then connected to basic monitors (ECG, NIBP and SpO2) IV line will be inserted and crystalloid fluid infusion will be started Patients will be premedicated by midazolam (1-2 mg), and they will be pre oxygenated 3-5 minutes before induction of anesthesia. General anesthesia will be given using propofol 2-3mg/kg intravenous (IV), fentanyl 1-2µg/kg IV and atracurium 0.5 mg/kg IV as a muscle relaxant to facilitate intubation. Anesthesia will be maintained by isoflurane and atracurium 0.1-0.2 mg/kg every 20-30 minutes. Patients will be mechanically ventilated with 50% O2 and 50% air keeping end-tidal CO2 between 30 - 35 mmHg. Fentanyl bolus doses of 0.5-1 mcg/kg will be given according to the changes of hemodynamic variables (more than 20% base line).

Adductor canal block will be given to both groups. In supine position, the leg will be externally rotated and the probe will be positioned at the midpoint of the thigh on its medial aspect. The adductor canal (AC) will be located anterolaterally to the superficial femoral artery deep to the sartorius muscle. The needle (size) will be advanced and a particular "pop" will be felt when the tip pierced the vastoadductor membrane, which is the roof of the adductor canal. A single dose of (20 ml of 0.25% bupivacaine) will be injected.

The patients in group A will receive gastrosoleus interfascial plane block. The patients in Group B will receive IPACK with the patient placed in a supine position and knee placed in position of 90° flexion At PACU, all patients will receive paracetamol 1gm to be repeated every 8 hours.

Patients' pain will be assessed using VAS score (12) in the PACU and every 4 hours thereafter for two days. Patient with VAS score ≥4 will recieve a rescue dose of morphine 3-5 mg.

Vital signs including heart rate, systolic and diastolic BP, and oxygen saturation will be recorded intra operatively every 15 min and postoperatively every 4 hours while assessing pain intensity.

• Time to first morphine analgesic dose and total rescue doses of morphine. [Time frame: time needed for patient to use morphine in hours after end of surgery]
• cumulative doses of morphine [Time frame: cumulative doses of morphine in mg in the first 24 hours after operation]
• Range of motion by assessing degree of knee extension 24 hours after surgery. [Time frame: Assessing degree of knee extension 24 hours after surgery.]
• Time of first postoperative ambulation and how many feets the patient will be able to walk. [Time frame: Time of first postoperative ambulation and how many feets the patient will be able to walk in the 24 hours after operation]
• Duration of postoperative hospital stay. [Time frame: Duration of postoperative hospital stay in days]
• complications of the block [Time frame: complications of the block (vascular injury, nerve injury, allergic reaction) in the 24 hours after surgery]