Thumb Opposition

Electrode Placement
Application Instruction by Dr. Lucinda Baker

Electrode placement for thumb opposition. Although the thumb opponens is a medial muscle, it is easily accessed off the lateral border of the first metacarpal. The positive electrode is placed over the extensor surface.

Thumb Opposition

Video Instruction
Audio Transcript:

Electrode placement for thumb opposition. Although the thumb opponens is a medial muscle, it is easily accessed off the lateral border of the first metacarpal. The positive electrode is placed over the extensor surface.

Activation of the stimulation causes thumb opposition. This subject demonstrates some voluntary finger flexion. This stimulated thumb opposition would be graded three minus out of five.

Thumb Opposition

Muscle Anatomy

Muscles involved in thumb opposition:

Opponens Pollicis
Origin: Trapezium and transverse carpal ligament
Insertion: Metacarpal bone of the thumb on its radial side

Related muscle for troubleshooting:

Abductor Pollicis Brevis
Origin: Transverse carpal ligament, the scaphoid and the trapezium
Insertion: Radial base of proximal 1st phalanx and the radial sesamoid

be Abductor Pollicis Longus
Origin: Posterior side of ulna, radius and interosseous membrane
Insertion: Base of first metacarpal

Thumb Opposition

Nerve Anatomy

Nerves involved in thumb opposition:

Opponens Pollicis
Nerve innervation: Recurrent branch of the median nerve
Nerve root: The median nerve originates from the lateral and medial cords of the brachial plexus and has contributions from ventral roots of C5, C6,C7 (lateral cord) and C8, T1 (medial cord)

note: The median nerve passes through the carpal tunnel and its compression there is the cause of carpal tunnel syndrome.