Definition

By: Gregory R. Waryasz, MD

The opponens pollicis muscle of the musculoskeletal system is characterized by its important role in opposing the thumb which is the most important thumb movement in the human.

It is part of the thenar muscles.  It consists of skeletal muscle fibers.

Its unique structural features include it being a quadrangular muscle that lies deep to the abductor pollicis brevis.  It is lateral to the flexor pollicis brevis.

The origin is the flexor retinaculum and tubercles of the scaphoid and trapezium.

The insertion is the lateral side of the 1st metacarpal.

The blood supply is from the arteries of the superficial palmar arch and venous drainage is from the accompanying veins.

The innervation is from the recurrent branch of the median nerve.

The opponens pollicis muscle as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.

The function of the opponens pollicis is to oppose the thumb by drawing the metacarpal medially to the center of the palm and also rotate the thumb medially. The opponens pollicis helps to pinch objects. The synergists are the abductor pollicis and the adductor pollicis.

Common diseases include carpal tunnel syndrome.

Carpal tunnel syndrome is a compressive neuropathy of the median nerve at the wrist.  It can lead to weakness in the hand and decreased sensation in the palm.  Patients often report numbness and tingling in the palm and distribution of the median nerve.  Long-standing carpal tunnel can lead to atrophy of the muscles innervated by the median nerve distal to the compressive neuropathy.

Commonly used diagnostic procedures include clinical history, physical exam, EMG, and MRI.

It is usually treated with bracing, NSAIDs, physical therapy, and corticosteroid injections for carpal tunnel syndrome.  A carpal tunnel surgical release procedure can often reduce the compressive neuropathy.

References

Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.

Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.

Wheeless’ Textbook of Orthopaedics: Opponens Pollicis (http://www.wheelessonline.com/ortho/opponens_pollicis)