Muscle Test and Tendon Exam: Extensor Pollicis Longus (EPL)

Test, Exam and Signs

Origin:	Ulna (posterolateral surface of middle shaft) Interosseous membrane
Insertion:	Thumb (base of distal phalanx, dorsal side)
Innervation:	Cervical root(s): C7 and C8 Nerve: radial nerve (posterior interosseous branch)

Grading of muscle strength:

Grade	Strength	Description
5*	Normal	Normal strength
4*	Good	Movement against external resistance but less than normal
3	Fair	Movement against gravity but not against added resistance
2	Poor	Movement at the joint with gravity eliminated
1	Trace	Trace of contraction but no movement at the joint
0	Zero	No contraction or muscle movement
*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

Forearm in mid-position, wrist in neutral with ulnar side of hand resting on the table. Thumb in a flexion posture. Some suggest that for Grades 0–2, the patient places his/her forearm in pronation with wrist in neutral and thumb in relaxed position to start.

Examiner’s Actions

Use a table to support the ulnar side of the patient’s hand and stabilize the proximal phalanx of the thumb. Apply resistance over the dorsal surface of the distal phalanx of the thumb in the direction of flexion. Some suggest that for Grades 0–2, the examiner should stabilize the patient’s wrist over its dorsal surface and then stabilize the patient’s fingers by gently placing them on the other hand across the fingers just below the metacarpophalangeal (MP) joint.

Instructions for the patient

Presentation Photos and Related Diagrams

EPL Muscle Testing. Note EPL tendon visible and palpable
EPL Muscle Testing. Note thumb raised off plane of table.
EPL anatomy illustration
This illustration represents the anatomy of the muscle and tendon origin and insertion. Should an individual sustain a laceration as depicted, the observer can assume that the underlying tendon may be at risk for complete transection. A proper examination is needed to determine the integrity of the tendon.

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 zero.

Comments and Pearls

When a patient can demonstrate full normal resistance, the examiner usually cannot "break" the patient's effort.
Continued action by the EPL will extend the MP and carpometacarpal (CMC) joints
A quick way to assess the functional status of the long thumb extensor is to flick the distal phalanx into flexion. If the finger rebounds or snaps back, it is a useful muscle.
The extensor pollicis longus can rupture after a closed nondisplaced distal radius fracture. This fracture complication can occur even if the fracture was treated without surgery.

Diagnoses Associated with Tests, Exams and Signs

Video

Muscle Testing Extensor Pollicis Longus (EPL)

References

Hislop JH, Avers D, and 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.
Kendall FP, McCreary EK, and Provance PG. Muscles Testing and Function. 4^th ed. Baltimore, MD: Williams & Wilkins, 1993, pp. 235-298.