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Abductor Digiti Minimi (ADM)

OVERVIEW
Other Name:
Abductor digiti quinti (ADQ).
 
Key Points:
• Abducts the small finger.
• Hypothenar eminence muscle (an intrinsic hand muscle).

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EXAMINATION
Muscle Function:
Primary:
• Abducts metacarpal-phalangeal and carpal-metacarpal joints of small finger.
• Assists in opposition of small finger.
Secondary:
• Metacarpal phalangeal joint flexion of small finger.
• Interphalangeal joint extension of small finger.
Palpation: Palpate ulnar aspect of hypothenar muscles while resisting small finger abduction. 
 
Strength Testing: Position – the palmar side up. Stabilize – the hand. Resist – the small finger abduction (in the direction of adduction).
 
Possible Substitutions:  Extensor digiti minimi – keep the small finger in neutral to prevent substitution and in respect to flexion and extension. Avoid small finger extension.
 
Relevant Anatomy:
Innervation:
• Roots: C8, T1.
• Nerve: Ulnar nerve; deep motor branch.
• Innervation Route:  C8, T1 → ulnar nerve → deep motor branch → abductor digiti minimi branch.
Origin: Distal pisiform, flexor carpi ulnaris tendon, and connective tissue lying between hook of hamate and pisiform.
 
Insertion: Splits into two tendon slips going to proximal phalanx base (at ulnar tubercle) of small finger, and ulnar aspect of extensor hood of small finger.