Tennis Elbow, Extensor Carpi Radialis Brevis, Everything You Need To Know - Dr. Nabil Ebraheim

Dr. Ebraheim’s educational animated video describes Extensor Carpi Radialis Brevis muscle ECRB - tennis elbow.
The muscle that is involved in the condition of tennis elbow is the extensor carpi radialis brevis muscle. The name of this muscle suggests it is small, however it is an important muscle that is involved in multiple unique conditions.
The ECRB muscle originates from the lateral epicondyle of the humerus (common extensor tendon). The ECRB muscle is inserted into the base of the dorsal aspect of the 3rd metacarpal. The ECRL muscle is inserted into the base of the 2nd metacarpal bone.
The ECRB muscle gets its nerve supply from the radial nerve.
The function of the ECRB is to extend and abduct the hand at the wrist joint.
The ECRB is located in the 2nd dorsal compartment on the radial side of the lister’s tubercle.
There are several conditions that are associated with ECRB muscle.
1-Tennis elbow (lateral epicondylitis)
It is an overuse injury that causes inflammation, tendinosis and lateral elbow pain at the origin of the ECRB tendon. Tennis elbow affects about 50% of all tennis players. It is the most common cause of elbow symptoms in patients that complain of elbow pain.
Tennis elbow involves the ECRB tendon origin. The pathology of the ECRB tendon in tennis elbow shows disorganized collagen, vascular hyperplasia and fibroblast hypertrophy. The condition usually starts by micro-tears of the origin of the ECRB which is precipitated and aggravated by repetitive wrist extension and forearm pronation.
About 5% of patients may have associated radial tunnel syndrome. In tennis elbow, the patient will complain of point tenderness around the lateral epicondyle. In radial tunnel syndrome, the point of tenderness will be about 3-4 cm distal and anterior to the lateral epicondyle. This should be in the differential diagnosis of tennis elbow.
Treatment of tennis elbow
•Activity modififcatin
•Anti-inflamatory medications
•Physical therapy especially eccentric exercise.
•Injection: steroid injection or may use PRP. Ultrasound guidance may be helpful.
•Surgery is the last resort. Release and debridement of the ECRB origin.
2-Intersection syndrome
Inflammation at the crossing of the first dorsal compartment and the second dorsal compartment that contains the ECRB. It occurs due to repetitive wrist extension. The tenderness is on the dorsoradial aspect of the forearm approximately 5 cm proximal to the wrist joint. This is the area of inflammation of the ECRL/ECRB as they intersect with APL and the EPB.
Treatment
•Rest
•Splinting
•Steroid injection
•Rarely surgery
3-The ECRB muscle is important in dorsal approach to the radius. The Thompson dorsal approach to the proximal radius may be used for exposure of the posterior aspect of the radial shaft. The incision is made in between the two muscles of the ECRB and the extensor digitorum.
4-In tennis elbow surgery, excessive release of the ECRB tendon (origin) during tennis elbow surgery can cause injury to the ulnar humeral ligament and cause posterolateral elbow instability. Note the proximity of the origin of the ECRB tendon to the ulnar humeral collateral ligament. The ligament is close to the tendon and can be injured due to excessive release of the origin of the ECRB tendon.
5-Tendon transfer in high radial nerve palsy. In high radial nerve palsy, injury to the radial nerve results in wrist drop due to paralysis of the wrist extensors. The pronator teres transfer to the ECRB is a very popular tendon transfer in high radial nerve palsy used to restore wrist extension.
High radila nerve palsy - pronator teres transfer to the ECRB to restore wrist extension.

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