Definition
By: Gregory R. Waryasz, MD
The extensor carpi radialis brevis muscle of the musculoskeletal system is characterized by being shorter than the extensor carpi radialis longus.
It is part of the forearm. It consists of skeletal muscle fibers.
Its unique structural features include its arising more distally than the extensor carpi radialis longus. This makes the muscle smaller in size. As it progresses to its insertion, it is covered by the extensor carpi radialis longus. The two muscles pass under the extensor retinaculum together in the tendinous sheath of the extensor carpi radials.
The origin is the lateral epicondyle of the humerus at the common extensor origin.
The insertion is the base of the 3rd 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 deep branch of the radial nerve.
The extensor carpi radialis brevis 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 brevis is to extend and abduct the hand at the wrist joint. It is the prime dorsiflexor of the hand. The synergists are the extensor carpi radialis longus and the extensor carpi ulnaris.
Common diseases include tendinitis, lateral epicondylitis, 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.
Lateral epicondylitis or tennis elbow is pain and inflammation on the lateral aspect of the elbow typically due to injury to the extensor carpi radialis brevis. It is a common orthopaedic condition that occurs in patients who are recreational athletes or those that engage in repetitive daily activities. Patients do not have to play tennis to have the condition.
Tendon rupture can occur due to trauma.
Commonly used diagnostic procedures include clinical history, physical exam, and MRI.
It is usually treated with physical therapy, steroid injections, and NSAIDs for tendinitis and lateral epicondylitis. Surgery may be required for lateral epicondylitis and tendinitis that does not respond to conservative measures. Surgery may be required to repair tendon ruptures.
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 Brevis (http://www.wheelessonline.com/ortho/extensor_carpi_radialis_brevis)