Clinical Observation of Bupivacaine Liposome for Lower Extremity Nerve Block

Inclusion Criteria: * Adults aged 18 to 85 years * Scheduled for elective unilateral lower limb surgery * Unilateral ultrasound-guided femoral nerve block clinically indicated as part of routine perioperative anesthesia and analgesia management * Ability to clearly distinguish between the blocked (operated) limb and the contralateral (non-blocked) limb for sensory and pain assessments * Ability to understand the study procedures and provide written informed consent * Ability to cooperate with sensory and motor assessments, including visual analog scale (VAS) scoring and quadriceps muscle strength testing Exclusion Criteria: * Known allergy or hypersensitivity to bupivacaine, amide-type local anesthetics, or any component of liposomal bupivacaine * Infection at or near the planned injection site * Coagulopathy or clinically significant bleeding disorder, or anticoagulant/antiplatelet therapy incompatible with peripheral nerve block * Pre-existing neurological deficits, neuropathy, or motor weakness affecting either lower limb that could interfere with sensory or motor assessments * Severe hepatic dysfunction or other conditions that increase the risk of local anesthetic systemic toxicity * Pregnancy or breastfeeding * Emergency surgery * Inability to complete study assessments or comply with study procedures