Corpus: Opponens pollcis muscle
from latin: pollex - thumb; opponere - to oppose
Definition
The opponens pollicis muscle is a short, triangular muscle that belongs to the thenar musculature of the hand. It is located beneath the abductor pollicis brevis muscle.
Anatomy
Origin
The muscle originates from the tubercle of the trapezium bone and the ligament structures on the palmar side of the carpal (flexor retinaculum).
Insertion
The short tendon of the muscle runs obliquely to distal and lateral and attaches on the lateral or radial side of the first metacarpal bone (Os metacarpale I).
Innervation
The innervation of the opponens pollicis muscle is provided by the median nerve from the brachial plexus. The corresponding segments are inconsistently reported in the literature as C6 to C8 or C8 to Th1.
Function
Clinic
The function of the opponens pollicis muscle can be tested using the Schaeffer’s test (opposition and adduction of thumb and little finger). In this test, the patient is asked to press the pads of the thumb and little finger together. If the opposition is incorrect, the thumb will touch the radial side of the little finger.
Alternatively, the patient should touch the base of the little finger with the tip of the thumb, without bending it, while the examiner offers slight resistance to this movement at the first metacarpal bone.