Fourth Dorsal Interosseous Muscle of Hand

Origin

The fourth dorsal interosseous muscle of hand consists of two heads:

- the lateral head, which originates from the medial aspect of the body of fourth metacarpal bone;

- the medial head, which originates from the lateral aspect of the body of fifth metacarpal bone.

Insertion

The fibers of the fourth dorsal interosseous muscle of hand travel inferiorly to the ring finger and insert, via a short tendon, onto the:

- medial aspect of the base of the proximal phalanx of ring finger;

- extensor expansion of ring finger.

Key Features & Anatomical Relations

The fourth dorsal interosseous muscle of hand is found in the interosseous compartment of the hand. It is a short, bipennate skeletal muscle.

It is located:

- posterior to the third palmar interosseous and fourth lumbrical muscles of hand;

- medial to the fourth metacarpal bone;

- lateral to the fifth metacarpal bone.

One of the perforating branches of deep palmar arch travels between the two heads of the third dorsal interosseous muscle of hand.

Actions & Testing

The fourth dorsal interosseous muscle of hand is involved in multiple actions:

- abducts the proximal phalanx of the ring finger (i.e., draws it away from the longitudinal axial line of the middle finger) at the fourth metacarpophalangeal joint;

- simultaneously flexes the fourth metacarpophalangeal joint and extends the interphalangeal joints of the ring finger, which occurs when the third lumbrical and second palmar interosseous muscles of hand contract simultaneously with it.

The fourth dorsal interosseous muscle of hand can be tested by abducting the proximal phalanx of the ring finger at the fourth metacarpophalangeal joint against resistance, during which it can be seen and palpated (Standring, 2016).

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.