Definition
By: Gregory R. Waryasz, MD
The extensor carpi radialis longus muscle of the musculoskeletal system is characterized by its importance to allow a person to clench one’s fist.
It is part of the forearm. It consists of skeletal muscle fibers.
Its unique structural features include its fusiform shape. It is partially covered by the brachioradialis and oftens blends with this muscle.
The origin is the lateral supraepicondylar ridge of the humerus.
The insertion is the base of the 2nd metacarpal on the dorsal side.
The blood supply is from the radial artery and venous drainage is from the accompanying veins.
The innervation is from the radial nerve.
The extensor carpi radialis 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 carpi radialis longus is to extend and abduct the hand at the wrist joint. The extensor carpi radialis longus is active during fist clenching. The synergists are the extensor carpi radialis brevis and the extensor carpi ulnaris.
Common diseases include tendinitis, avulsion, and tendon rupture.
Tendinitis is an overuse injury. The extensor carpi radialis longus and extensor carpi radialis brevis can have tendinitis due to an osteophyte that lies deep to the tendons.
The extensor carpi radialis longus tendon can avulse from the base of the 2nd metacarpal.
Tendon rupture can occur due to trauma.
The tendon portion of the muscle can be used for tendon transplants.
Commonly used diagnostic procedures include clinical history, physical exam, and MRI.
It is usually treated with physical therapy and NSAIDs for tendinitis. Avulsion injuries and tendon ruptures may or may not require surgical intervention.
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 Radialis Longus (http://www.wheelessonline.com/ortho/extensor_carpi_radialis_longus)