First Dorsal Interosseous Muscle of Hand

Origin

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

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

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

Insertion

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

- lateral aspect of the base of the proximal phalanx of index finger;

- extensor expansion of index finger.

Key Features & Anatomical Relations

The first 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 adductor pollicis muscle and first lumbrical muscle of hand;

- medial to the first metacarpal bone;

- lateral to the second metacarpal bone.

The radial artery travels between the two heads of the first dorsal interosseous muscle of hand.

Actions & Testing

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

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

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

The first dorsal interosseous muscle of hand can be tested by abducting the proximal phalanx of index finger at the second 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.