Definition

By: Gregory R. Waryasz, MD

The extensor pollicis longus muscle of the musculoskeletal system is characterized by passing through extensor compartment three.

It is part of the forearm.  It consists of skeletal muscle fibers.

Its unique structural features include its tendon passing through the third extensor compartment in the tendinous sheath of the extensor pollicis longus.  The extensor pollicis longus is larger than the extensor pollicis brevis.  The extensor pollicis longus tendon is the marker for the posterior border of the anatomic snuff box.

The origin is the posterior surface of the middle third of the ulna and interosseous membrane.

The insertion is the base of the dorsal aspect of the distal phalanx of the thumb.

The blood supply is from the radial artery and venous drainage is from the accompanying veins.

The innervation is from the posterior interosseous nerve.

The extensor pollicis longus 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 extensor pollicis longus is to extend the distal phalanx of the thumb at the interphalangeal joint.  It also extends the metacarpophalangeal and carpometacarpal joints. The extensor pollicis longus helps to adduct the extended thumb and rotate it laterally.

Common diseases include tendon rupture.

Tendon rupture can occur from trauma or from rheumatoid arthritis.

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

It is usually treated with surgery to reconstruct the tendon.

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: Extensor Pollicis Longus (http://www.wheelessonline.com/ortho/extensor_pollicis_longus)