ACB Versus IA Analgesia in Knee Arthroscopy

Reconstruction of the anterior cruciate ligament (ACL) of the knee is a painful procedure, with postoperative analgesia providing patient comfort, early mobilization, and discharge within 24 hours.

Various methods for postoperative analgesia management are available, such as systemic opioids, epidural local anesthetic, peripheral nerve block and local anesthetic infiltration analgesia. Use of systemic opioids can cause adverse effects that may affect functional rehabilitation, such as nausea, vomiting, pruritus, sedation and respiratory depression. Hypotension, urinary retention, and pruritus are more common in patients with epidural analgesia. In addition, use of long-acting intrathecal opioids causes adverse effects such as bilateral motor block, tremor and hypotension. Systemic and intrathecal methods for postoperative analgesia are gradually being abandoned because of these negative effects.

The saphenous nerve is the largest contributor to sensory perception around the knee, while the adductor canal contains the nerve to the vastus medialis, the medial femoral cutaneous nerve, the medial retinacular nerve, articular branches from the posterior division of the obturator nerve and occasionally the anterior branch of the obturator nerve. Although adductor canal block (ACB) can contribute towards motor blockade of the periarticular musculature, its effect on functional weakness of the quadriceps has been reported to be minimal, compared with femoral nerve block (FNB).

Intra-articular (IA) local anesthetic agents have been used either alone or in combination with other agent. However, it was observed that use of combination of drug is better than single drug for prevention of postoperative pain, providing synergistic effect and reducing side effects compared to high dose of single drug.

Dexamethasone is a potent and highly selective glucocorticoid with minimal mineralocorticoid effect. It blocks the nociceptive impulse transmission along the myelinated C fibers. Dexamethasone prolongs the duration of regional blocks, when combined with local anesthetics.

Inclusion criteria

• Patients undergoing elective arthroscopic reconstruction of the anterior cruciate ligament (ACL) under spinal anesthesia, aged from 18 to 65 years old

Exclusion criteria

• Contraindications to peripheral nerve block (e.g. allergy to local anesthetics, coagulopathy, infection in the area)
• History of cardiovascular, cerebrovascular, and respiratory diseases
• Preexisting neuropathies
• Chronic pain syndrome
• Opioid dependence
• Patients with diabetes mellitus, sever hypertension, hepatic or renal dysfunction
• Pregnancy
• Not willingness to participate.