The goal of this clinical trial is to compare the effects of femoral triangle block (FTB) and adductor canal block (ACB) on early quadriceps function after total knee arthroplasty (TKA).
The main question it aims to answer is whether FTB causes more early quadriceps functional impairment than ACB under a standardized multimodal analgesia protocol.
Researchers will compare FTB and ACB using a composite binary functional outcome measured 6 hours after block completion. Quadriceps functional impairment is defined as the inability to perform a structured straight leg raise or quadriceps muscle strength \<50% of the preoperative baseline.
Participants will be randomly assigned to receive ultrasound-guided FTB or ACB. All participants will also receive a popliteal plexus block and standardized multimodal analgesia.
Adult patients (≥ 20 years of age) are scheduled to undergo primary unilateral TKA.
American Society of Anesthesiologists (ASA) physical status I-III.
Ability to ambulate independently prior to surgery.
Ability to understand the study procedures and provide written informed consent.
Known allergy or contraindication to local anesthetic agents used in this study.
Pre-existing neurological or neuromuscular disorders affect lower limb strength or motor control.
Severe cognitive impairment or psychiatric conditions interfere with study participation or assessment.
History of revision knee arthroplasty on the operative side.
Parallel
Femoral Triangle Block (FTB) Group
Procedure/SurgeryUltrasound-guided femoral triangle block performed as part of a standardized multimodal analgesia protocol for total knee arthroplasty. A total of 10 mL of 0.25% levobupivacaine is injected in the femoral triangle to achieve sensory blockade of the saphenous nerve, the nerve to vastus medialis, and surrounding structures. The injection is performed at the distal femoral triangle under ultrasound guidance, targeting the perineural space adjacent to the relevant nerve branches. In all participants, a popliteal plexus block using 15 mL of 0.25% levobupivacaine is additionally performed to standardize posterior knee analgesia.
Adductor Canal Block (ACB) Group
Procedure/SurgeryUltrasound-guided adductor canal block performed as part of a standardized multimodal analgesia protocol for total knee arthroplasty. A total of 10 mL of 0.25% levobupivacaine is administered in a divided manner within the proximal adductor canal, targeting both the saphenous nerve within the canal and the nerve to vastus medialis running adjacent to the canal. The injection is performed under ultrasound guidance to achieve selective sensory blockade while minimizing motor involvement. In all participants, a popliteal plexus block using 15 mL of 0.25% levobupivacaine is additionally performed to standardize posterior knee analgesia.
Participants with quadriceps functional impairment at 6 hours after block completion
Composite binary functional outcome defined as the inability to perform a structured straight leg raise (SLR) or normalized isometric quadriceps muscle strength \<50% of the preoperative baseline. The outcome will be reported as the percentage of participants with quadriceps functional impairment.
Participants with quadriceps functional impairment at 24 hours after block completion
Composite binary functional outcome defined as the inability to perform a structured SLR or normalized isometric quadriceps muscle strength \<50% of the preoperative baseline. The outcome will be reported as the percentage of participants with quadriceps functional impairment.
Participants able to perform a structured straight leg raise at 6 and 24 hours after block completion
Ability to perform a structured straight leg raise (SLR), assessed using the predefined study procedure. The outcome will be reported as the percentage of participants able to perform the structured SLR.
Normalized isometric quadriceps muscle strength at 6 and 24 hours after block completion
Normalized isometric quadriceps muscle strength, expressed as a percentage of the preoperative baseline (%MVIC). Higher values indicate greater preservation of quadriceps strength.
Postoperative pain intensity at rest on the Numeric Rating Scale
Pain intensity at rest assessed using the Numeric Rating Scale (NRS), ranging from 0 to 10, where 0 indicates no pain and 10 indicates the worst pain imaginable; higher scores indicate worse pain. Pain will be assessed postoperatively after patient awakening.
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