This study employs a randomized controlled trial to investigate whether bupivacaine liposome injection for adductor canal block can effectively improve lower limb muscle strength after total knee arthroplasty.
Total knee arthroplasty (TKA) involves significant trauma, and postoperative patients often experience moderate to severe pain, which limits early knee joint functional exercise and affects functional recovery. Peripheral nerve blocks can effectively relieve pain, but while providing adequate analgesia, they may also affect the motor nerves of the lower limbs, increasing the risk of falls when patients begin ambulation. Some studies have found that the incidence of falls in patients using nerve blocks during the early postoperative period, especially during hospitalization, can be as high as 2% . The actual incidence in clinical practice may be even higher. The period of highest risk is when the nerve block effect has not completely subsided and patients begin attempting to ambulate, typically within 24 to 48 hours after surgery. The loss of muscle strength caused by motor nerve blockade is the most direct cause of postoperative falls, primarily due to severe weakness in key stabilizing muscle groups such as the quadriceps.The adductor canal block has clear advantages. However, traditional local anesthetics, represented by ropivacaine or bupivacaine, typically provide effective analgesia for only 12-24 hours after a single injection, making it difficult to fully cover the peak pain period of 48-72 hours postoperatively. Continuous femoral nerve block with ropivacaine can provide prolonged analgesia. When combined with a sciatic nerve block, it can achieve nearly complete analgesia coverage for the knee. Its drawback is its association with quadriceps impairment, which may increase the risk of falls. Continuous adductor canal block also provides prolonged analgesia and has a lesser impact on postoperative muscle strength, but it faces challenges such as catheter placement difficulty and inconvenience for postoperative mobility. In contrast, bupivacaine liposome can provide analgesia for up to 72 hours. If, while offering high-quality analgesia, bupivacaine liposome indeed causes significant weakening of quadriceps strength during the critical first 2-3 days after surgery, the safety and effectiveness of early patient ambulation would be greatly compromised, potentially even increasing the risk of falls. This would contradict the original intent of using the adductor canal block to preserve muscle strength. Conversely, if it is proven to have a lesser impact on muscle strength compared to continuous femoral nerve block, it could become an almost ideal analgesic option.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
80
An ultrasound-guided adductor canal block is performed via the conventional adductor canal approach. Under ultrasound guidance, 20 milliliters of 1.33% bupivacaine liposome is injected into the adductor canal.
An ultrasound-guided perineural sheath block of the femoral nerve is performed via the conventional femoral nerve approach. A femoral nerve catheter is then placed and connected to an analgesia pump containing 150 milliliters of 0.20% ropivacaine.
General hospital of Ningxia medical university
Yinchuan, Ningxia, China
Quadriceps Muscle Strength
The Maximum Voluntary Isometric Contraction (MVIC) test is used to assess quadriceps strength. The tester holds a handheld dynamometer. The patient sits on the bed with legs hanging naturally, and the knee is flexed to 60°. The patient is instructed to slowly exert force to extend the knee forward. As the patient exerts force, the tester applies an equal and opposite counterforce with the dynamometer to maintain the position and angle of the lower leg. The patient sustains maximum effort for 3-5 seconds, and the peak value displayed on the dynamometer is recorded as the result for that trial. Each leg is tested 2-3 times, with a 60-90 second rest between trials to prevent muscle fatigue from affecting the results. The average value is recorded as the final outcome. The unit of measurement is Newtons (N).
Time frame: 24 hours after surgery
Quadriceps muscle strength at other time points
The Maximum Voluntary Isometric Contraction (MVIC) test is used to assess quadriceps strength. The tester holds a handheld dynamometer. The patient sits on the bed with legs hanging naturally, and the knee is flexed to 60°. The patient is instructed to slowly exert force to extend the knee forward. As the patient exerts force, the tester applies an equal and opposite counterforce with the dynamometer to maintain the position and angle of the lower leg. The patient sustains maximum effort for 3-5 seconds, and the peak value displayed on the dynamometer is recorded as the result for that trial. Each leg is tested 2-3 times, with a 60-90 second rest between trials to prevent muscle fatigue from affecting the results. The average value is recorded as the final outcome. The unit of measurement is Newtons (N).
Time frame: 48 hours after surgery
Numeric Rating Scale (NRS) Score
Using a scale from 0 to 10 to indicate pain intensity, where 0 represents no pain and 10 represents the worst possible pain.
Time frame: 24 and 48 hours after surgery
Quadriceps muscle strength grade
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Perform a Manual Muscle Test (MMT). The patient is placed in the supine position, with a soft pillow under the knee to provide slight flexion, or sits on the edge of the bed with legs hanging naturally. The examiner stabilizes the patient's thigh with one hand to prevent hip compensation and applies downward resistance with the other hand just above the patient's ankle. Instruct the patient to forcefully extend the knee against the resistance. Observe muscle contraction and joint range of motion, and assess according to the 0-5 grade muscle strength scale.
Time frame: 24 and 48 hours after surgery
Knee Joint Range of Motion
Using a goniometer, accurately measure the patient's knee joint flexion and extension range of motion. During measurement, the patient is in the supine position. The axis of the goniometer is aligned with the lateral femoral condyle, the stationary arm is parallel to the long axis of the femur, and the movable arm is parallel to the long axis of the tibia. Record the angles at full knee extension (0°) and maximum flexion separately.
Time frame: 24 and 48 hours after surgery
Total Opioid Consumption
Total postoperative consumption of opioids.
Time frame: From the end of the surgery until 72 hours postoperatively
Postoperative Adverse Reactions
Including nausea and vomiting, urinary retention, constipation, puncture site ecchymosis and infection, as well as local anesthetic systemic toxicity.
Time frame: From the end of the surgery until 72 hours postoperatively