Determination of the Optimal Volume of Liposomal Bupivacaine in Adductor Canal Block for Knee Joint Surgery

The maximum voluntary isometric contraction (MVIC) of the quadriceps femoris muscle is measured using a handheld dynamometer (HHD) and then re - measured 30 minutes after the block. A decrease in muscle strength of ≥ 25% is defined as a significant impact on motor function.

Sensory block at 30 minutes after surgery (pinprick test at several sites in the area innervated by the saphenous nerve) and a resting NRS score ≤ 3 points. The sensory block is evaluated using a pinprick test for sensation. This test is performed before the adductor canal block (baseline) and every 5 minutes after the nerve block until 30 minutes have elapsed or the surgery begins. The sensory test is carried out in the distribution area of the saphenous nerve (medial side of the lower leg), as well as on the anterior, medial, lateral, and posteromedial sides of the surgical knee joint, and above the patella. A sensory score of 2 indicates normal sensation, 1 indicates hypoesthesia, and 0 indicates no sensation. We define a successful adductor canal block as the occurrence of sensory block in the surgical knee joint within 30 minutes after the nerve block, that is, the loss of sensation to the pinprick (sensory score of 1 or lower).

The NRS (Numeric Rating Scale) scores range from 0 to 10 in total. A score of 0 represents no pain, while a score of 10 indicates severe pain. A score of 0 to 3 indicates mild pain, which is tolerable and does not affect sleep. A score of 4 to 6 indicates moderate pain, which is more obvious and will somewhat interfere with the patient's daily life and sleep, but is still bearable. A score of 7 to 10 indicates severe pain, which is intense and difficult to endure, seriously affecting the patient's daily life and sleep. The lower the score, the better the analgesic effect of the adductor canal block performed with liposomal bupivacaine.

converted into morphine equivalent, mg. After performing the adductor canal block with liposomal bupivacaine, the lower the consumption of opioid drugs, the better the effect of nerve block and the more prolonged the blocking duration.

The time from the completion of the block to the first need for rescue analgesia.

Observe the impact of adductor canal block on the patient's motor function. If the patient can get out of bed and move for the first time within a relatively short and reasonable period, it usually indicates that the nerve block has a good effect. It can effectively relieve pain without excessively affecting the patient's motor function, enabling the patient to regain a certain degree of activity ability at an earlier stage.

Total score of 10 points (0 points: extremely dissatisfied, 10 points: extremely satisfied). Higher scores indicate greater patient satisfaction and better efficacy of nerve block.

The patient's self-evaluated recovery experience (Likert 5-point scale). The Likert five-point scale employs an odd-numbered grading system (5-point scale), with each item corresponding to five options representing an intensity gradient of attitudes or experiences. Common expressions include:

Strongly Disagree / Very Poor (1 point) Disagree / Poor (2 points) Neutral / Average (3 points) Agree / Good (4 points) Strongly Agree / Very Good (5 points) The total score is calculated by summing the scores of all items, reflecting the overall positivity of the evaluated experience (e.g., recovery experience).

The percentage change in muscle strength 30 minutes after the block compared to the baseline level.

Pay attention to avoiding blood vessels. Aspirating during drug injection can reduce the toxic reaction of local anesthetics caused by the entry of local anesthetics into the bloodstream.

Observe whether there is nerve injury. Muscle Strength Grading Standards (0-5 Scale) Assessment Method: To assess for neurological complications, inquire whether the patient experiences pain and if numbness is present in the saphenous nerve distribution area.

Assess muscle strength levels through resistance-based grading. Grade 0 : No muscle contraction (complete paralysis) Limbs show no movement or tension.

Grade 1 : Slight muscle contraction without joint movement Muscle twitching visible, no limb motion.

Grade 2: Joint movement possible horizontally but cannot resist gravity Leg slides on bed but cannot lift.

Grade 3 : Can complete motions against gravity but cannot resist external resistance Lifts leg off the bed but collapses under light pressure.

Grade 4: Can resist partial external force but weaker than normal Holds position against mild resistance but fatigues quickly.

Grade 5: Normal strength, fully resists resistance.

Examine whether the sensory and motor function of the sciatic nerve is impaired

he incidence of falls can reflect the impact of nerve block on quadriceps muscle strength; a higher incidence indicates a greater effect on motor function.