Test: Thumb MP Extension Tests (Extensor pollicis brevis)

Video Link

Background/Purpose

The Extensor pollicis brevis is an inconstant muscle that often blends with the Extensor pollicis longus, in which event it is not possible to separate the brevis from the longus by clinical tests, and the test for the longus prevails.

Procedure

Grade 5 (Normal) to Grade 0 (Zero)
Position of patient: Forearm in midposition and wrist in neutral; CMC and IP points of the thumb are relaxed and in slight flexion. The MP joint of the thumb is in abduction and flexion.
Position of examiner: Stabilize the first metacarpal firmly, allowing motion to occur only at the MP joint. Resistance is provided with the other hand on the dorsal surface of the proximal phalanx in the direction of flexion. This normally is not a strong muscle.


Performed: Unilaterally

Dialog

Test: Patient extends the MP joint of the thumb while keeping the IP joint slightly flexed. Instructions to patient: “Bring your thumb up so it points toward the ceiling; don’t move the end joint. Hold it. Don’t let me push it down.”

Criteria

• Grade 5 (Normal) and Grade 4 (Good): Only the experienced examiner can accurately distinguish between Grades 5 and 4. Resistance should be applied carefully and slowly because this usually is a weak muscle.
• Grade 3 (Fair): Patient moves proximal phalanx of the thumb through full range of extension with little or no resistance.
• Grade 2 (Poor): Patient moves proximal phalanx through partial range of motion.
• Grade 1 (Trace): The tendon of the Flexor pollicis brevis is palpated at the base of the 1st metacarpal where it lies between the tendons of the Abductor pollicis and the Extensor pollicis longus.

Measurement

LOINC Code

0

Scale/Grading

Pass/Fail