Hand Surgery Source

Muscle Test and Tendon Exam: Extensor Carpi Radialis Brevis (ECRB)

Test, Exam and Signs
Origin: Humerus (lateral epicondyle via common forearm extensor tendon
Radial collateral ligament of elbow joint
Aponeurosis of muscle
Insertion: 3rd metacarpal bone (base of dorsal surface on radial side)
2nd metacarpal (occasionally)
Innervation: Cervical root(s):  C7 and C8
Nerve: radial nerve (posterior interosseous branch)

 

Grading of muscle strength:

Grade

Strength

Description

  5*

Normal

Completes full range of motion against maximal finger resistance

  4*

Good

Tolerates moderate resistance

3

Fair

Completes full range of motion with no resistance

2

Poor

Completes partial range of motion

1

Trace

Slight contractile activity

0

Zero

No contractile activity

*The distinction between Grades 4 and 5 is based on comparison with the normal hand and, barring that, extensive experience in testing the hand.

Position of patient's hand and upper extremity

  • Sitting with elbow flexed, the forearm is fully pronated, and both are supported on a table. Some suggest that the forearm be supported on a table in neutral position for Grade 2, and that for Grades 0 and 1, the forearm supported on a table with hand fully pronated.

Examiner’s Actions

  • Sitting or standing at a diagonal in front of patient, support the patient’s forearm. Place the hand used for resistance over the dorsal (extensor) surface of metacarpals. Some suggest that for Grade 2, the examiner support the patient’s wrists for testing and for Grades 0 and 1, the examiner support both the patient’s wrist in extension. For these Grades, the examiner palpates the tendon on the dorsal surface of the wrist in line with the third metacarpal bone.

Instructions for the patient

  • “Bring your wrist up. Hold it. Don’t let me push it down.” Some suggest “bend your wrist back” for Grade 2, and “Try to bring your wrist back” for Grades 0 and 1.
Presentation Photos and Related Diagrams
  • ECRB Muscle Test. Tendon palpated at RC join level while patient extends wrist against resistance.
    ECRB Muscle Test. Tendon palpated at RC join level while patient extends wrist against resistance.
  • ECRB anatomy illustration
    ECRB anatomy illustration
  • ECRB anatomy illustration
    ECRB anatomy illustration
Definition of Positive Result
  • In muscle testing, a normal result is a positive one. During a normal muscle test, the examiner should observe a normal muscle contraction that can move the joint or tendon against full resistance.
Definition of Negative Result
  • In muscle testing, an abnormal result is a negative one. During an abnormal muscle test, the examiner should observe an abnormal muscle contraction that can move the joint or tendon. In a complete denervation injury, such as a complete nerve laceration, there will be no evidence of any muscle function and the muscle testing grade will be 0.
Comments and Pearls
  • The ECRB is considerably stronger than the extensor carpi ulnaris (ECU)
  • A patient with complete quadriplegia at C5–C6 will have only radial wrist extensors remaining; radial deviation during extension is therefore the prevailing extensor motion at the wrist.
Diagnoses Associated with Tests, Exams and Signs
References
  1. Hislop JH, Avers D, Brown M. Daniels and Worthingham's Muscle Testing, Techniques of Manual Examination and Performance Testing. 9th ed. St. Louis, Missouri: Elsevier Saunders, 2014, pp. 138–202.
  2. Kendall FP, McCreary EK, Provance PG. Muscles Testing and Function. 4th ed. Baltimore, MD: Williams & Wilkins, 1993, pp. 235–298.