Targeted Nerve Injection to the Knee (Nerve to Vastus Medialis): Comparing Two Adductor Canal Block Approaches

Study of Targeted Injection of Nerves to the Knee-A Volunteer Trial Evaluating Nerve to Vastus Medialis

This randomized, double-blinded volunteer study compares two ways of performing the adductor canal (AC) nerve block at the mid-thigh to see which approach more reliably numbs the anteromedial knee. One approach is the traditional AC block placed near the saphenous nerve; the other separately targets the nerve to vastus medialis (NVM) in addition to the saphenous nerve. Healthy adult participants receive both blocks in one visit (one on each leg), with the order randomized. The primary outcome is change in quadriceps strength (a proxy for vastus medialis anesthesia) measured by load-cell dynamometry. Secondary outcomes include cutaneous sensory mapping (pinprick and cold) and the percentage of a standardized, marked knee-incision line covered by sensory block. The study uses ultrasound guidance and a standard dose of chloroprocaine, with routine monitoring to minimize risks.

Inclusion Criteria:

• Age ≥18 years
• Able to provide written informed consent
• Able and willing to comply with study procedures and ~6-hour visit
• American Society of Anesthesiologists (ASA) Physical Status 1 or 2
• Weight >70 kg

Exclusion Criteria:

• BMI >35 kg/m²
• Use of analgesics within 24 hours before the procedure
• History of thigh trauma or surgery
• Pregnant or planning pregnancy
• Lower extremity deformities/tattoos interfering with block performance
• Systemic neuromuscular disease
• Contraindications to regional anesthesia (e.g., infection, allergy, challenging sonoanatomy)
• Other health conditions that would affect safe participation