A Tactile Trans-Flexor Carpi Radialis Surface Landmark Technique for Median Nerve Local Injection: A Cadaveric Study

Area of Science:

• Anatomy
• Surgical Techniques
• Regional Anesthesia

Background:

• Median nerve (MN) blocks are common for wrist anesthesia but face challenges due to anatomical variations like absent palmaris longus tendon.
• The palmaris longus tendon is often used as a landmark, but its absence in some individuals complicates standard MN block procedures.

Purpose of the Study:

• To investigate a novel trans-flexor carpi radialis (trans-FCR) technique for median nerve anesthesia.
• To evaluate the trans-FCR technique as a reliable alternative landmark for MN blocks, independent of the palmaris longus tendon.

Main Methods:

• Utilized 14 fresh frozen upper extremity cadaver specimens.
• Employed a 25-gauge needle inserted through the flexor carpi radialis (FCR) sheath, approximately 4 cm proximal to the wrist crease.
• Compared the trans-FCR technique against two established surface landmark techniques.

Main Results:

• The trans-FCR technique successfully avoided critical structures, including the median nerve (3.5 mm), radial artery (8.5 mm), and the palmar cutaneous branch of the MN (3.8 mm).
• No instances of median nerve penetration occurred with the trans-FCR approach.
• The technique's safety was consistent regardless of palmaris longus tendon presence, with no difference in injury rates to surrounding structures.

Conclusions:

• The trans-FCR technique provides an anatomically sound method for MN blocks under local anesthesia.
• This novel technique relies on a consistent tactile landmark (FCR tendon) and does not depend on the palmaris longus tendon.
• Further clinical studies are warranted to validate the efficacy of the trans-FCR technique in vivo.