Extensor Carpi Radialis Brevis: Anatomy, Functions, Lateral Epicondylitis

The extensor carpi radialis brevis is a muscle located in the forearm that has the main function of extending and abducting the hand. It is part of a group of seven superficial extensor muscles found in the forearm. Four of these seven muscles have the same origin, in the lower portion of the humerus.

This muscle shares the same synovial sheath with the extensor carpi radialis longus. The synovial sheath is a fluid-forming structure that lines the tendons and cushions their movement against the bones.

The injury to your tendon, called  lateral epicondylitis  or popularly as tennis elbow, is one of the main reasons for consultation in trauma, since it causes a lot of pain and inflammation in the external part of the elbow.

Anatomy

The elbow is a joint that joins the arm with the forearm and allows the mobility of the upper limb.

It is made up of three bones, the humerus in the upper part, and the radius and ulna in the lower part; This is why it is also known as the  humerus-radio-ulnar joint .

In the proximal elbow, the humerus has two protrusions called the medial and lateral epicondyles. Several of the muscles that handle flexion and extension movements of the wrist are inserted into these protrusions.

The extensor carpi radialis brevis originates from the lateral epicondyle. It shares this insertion site with three other extensor muscles: the extensor carpi ulnaris, the extensor digiti minimi, and the extensor digitorum.

Together with these muscles it is part of the seven superficial extensor muscles of the forearm.

Completing the group of extensor muscles are the brachioradialis, the extensor carpi radialis longus, and the anconeus, which do not share the insertion point of the extensor carpi radialis brevis, but do share their functions.

Along its path, it accompanies the extensor carpi radialis longus, being partially covered by it and complementing its functions.

Both muscles share the same synovial sheath, which is a fluid-forming fibrous sheet that protects the tendons from continuous friction against the bone surface.

The distal insertion of the extensor carpi radialis brevis is lateral to the third metacarpal bone.

Regarding the blood supply, this muscle receives its supply directly from the radial artery and, indirectly, from some of its collateral branches, mainly from the recurrent radial artery.

For its part, the neurological supply is ensured by direct branches of the radial nerve, which runs lateral to it.

Features

The extensor carpi radialis brevis is primarily concerned with extension and adduction movements of the wrist joint.

The extension of the wrist can reach an amplitude of up to approximately 85 °. For its part, the adduction of the wrist is the movement of the hand in the direction of the first finger or thumb.

The adduction movement can reach up to 55 °, when done forcibly.

Both extension and adduction movements are performed by the extensor carpi radialis brevis, supported by the extensor carpi radialis longus.

Lateral epicondylitis

– What is it?

Inflammation of the extensor carpi radialis brevis insertion tendon is known as lateral epicondylitis. It is the most frequent inflammatory pathology of the elbow.

Despite being colloquially called  tennis elbow , only 5% of patients with this condition are practitioners of that sport. Lateral epicondylitis can be found in anyone who performs activities that strain the elbow joint, especially with continuous flexion and extension movements.

It can be observed both in tennis players and in other types of athletes such as baseball players, javelin throwers, golfers, among others.

It can also be due to bone degeneration due to age or overuse of the joint due to the work that is done. Bricklayers, typists, and mechanics are some of the workers who are exposed to this injury.

– Pathophysiology

The process by which a chronic inflammation is formed in the tendon of the extensor carpi brevis is a mechanism that has been studied in detail, given the high rate of consultations for this condition.

When there is an overload due to the excessive use of the wrist joint, especially in the movements of extension and flexion, the tendon of the extensor carpi brevis begins to have minimal tears.

These small lesions are triggering the inflammatory process. When there is no rest and there is no rest of the joint, the inflammation causes fibrous tissue to form with few blood vessels, similar to scar tissue.

All this prevents there from being a true remodeling and complete healing of the tendon, whereby severe pain and chronic inflammation begins.

Once the clinical picture is fully established, symptoms do not improve unless treatment is administered.

– Treatment

Most lateral epicondylitis, in its initial stages, improve with clinical therapy, without the need for invasive techniques. However, in some cases, surgery is the only treatment that gives a definitive cure.

Non-surgical treatment

Non-invasive treatment consists of the administration of topical analgesics, rest, partial immobilization with a sling, rehabilitation with special physical therapy exercises, thermal radiofrequency, and shock wave therapy.

If the patient does not improve or the symptoms increase after three weeks of non-invasive treatment, a second phase should be passed, which is non-surgical invasive treatment.

This stage consists of injections for steroid infiltration at the tendon insertion site, to improve inflammation.

Botulinum toxin injection is another treatment used to prevent continued tendon damage. This toxin is a neurotoxin that works by causing temporary paralysis of the muscles.

Biological therapies, with infiltration of platelet-rich plasma or the patient’s own whole blood, are being widely used today, showing a significant improvement in the pathology.

Surgical treatment

This type of treatment is reserved for those cases in which conservative therapies have been tried without observing any type of improvement.

The goal of the surgery is to remove the fibrous scar tissue that has formed at the insertion point of the tendon, to promote its improvement with new healthy tissue.

The results of the surgery are very good in the long term and the patient can return to his activities around four weeks after the procedure.

References

  1. Walkowski, AD; Goldman, EM. (2019). Anatomy, Shoulder and Upper Limb, Forearm Extensor Carpi Radialis Brevis Muscle. StatPearls. Taken from: ncbi.nlm.nih.gov
  2. Álvarez Reya, G; Álvarez Reyb, I; Álvarez Bustos, G. (2006). Tennis elbow (external epicondylar tendinosis): ultrasound-guided sclerosing treatment with polidocanol. About two cases. Apunts. Sports medicine. Taken from: apunts.org
  3. Lai, W. C; Erickson, B. J; Mlynarek, R. A; Wang, D. (2018). Chronic lateral epicondylitis: challenges and solutions. Open access journal of sports medicine. Taken from: ncbi.nlm.nih.gov
  4. Cowboy-Picado, A; Barco, R; Antuña, SA (2017). Lateral epicondylitis of the elbow. EFORT open reviews. Taken from: ncbi.nlm.nih.gov
  5. Buchanan BK, Varacallo M. (2019). Tennis Elbow (Lateral Epicondylitis). StatPearls. Taken from: ncbi.nlm.nih.gov

Add a Comment

Your email address will not be published. Required fields are marked *