Definition
By: Gregory R. Waryasz, MD
The extensor carpi ulnaris muscle of the musculoskeletal system is characterized by being the tendon that passes through the 6th extensor compartment on the dorsal wrist.
It is part of the forearm. It consists of skeletal muscle fibers.
Its unique structural features include its being long and fusiform. It has two heads; humeral and ulnar. The common tendon from the two heads passes through the extensor retinaculum in the tendinous sheath of the extensor carpi ulnaris. This is the 6th extensor compartment.
The origin of the humeral head is the lateral epicondyle of the humerus at the common extensor origin. The origin of the ulnar head is from the posterior border of the ulna through a shared aponeurosis.
The insertion is the dorsal aspect of the base of the 5th metacarpal.
The blood supply is from the ulnar artery and venous drainage is from the accompanying veins.
The innervation is from the posterior interosseous nerve.
The extensor carpi ulnaris 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 carpi ulnaris is to extend and adduct the hand at the wrist joint. The synergists are the extensor carpi radialis brevis and longus. Along with the extensor carpi radialis longus, the extensor carpi ulnaris is important for allowing a person to clench one?s fist.
Common diseases include tendon rupture, tenosynovitis, and dislocation.
Tendon rupture can occur due to trauma.
Tenosynovitis is a condition of inflammation of the tendon and the tendon?s synovial sheath. Extensor carpi ulnaris tenosynovitis can occur at the distal ulna.
Dislocation injury can occur with forearm rotation, rheumatoid arthritis, or following a fracture of the distal radius. Recurrent subluxation can cause a painful snapping sensation.
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, and MRI.
It is usually treated with NSAIDs, physical therapy, and bracing for tenosynovitis. Tendon rupture and dislocation may require surgery.
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 Carpi Ulnari (http://www.wheelessonline.com/ortho/extensor_carpi_ulnaris)