Third Dorsal Interosseous Muscle of Hand

Origin

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

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

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

Insertion

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

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

- extensor expansion of middle finger.

Key Features & Anatomical Relations

The third 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 second palmar interosseous and third lumbrical muscles of hand;

- Medial to the third metacarpal bone;

- lateral to the fourth 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 third dorsal interosseous muscle of hand is involved in multiple actions:

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

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

Because the second and third dorsal interossei muscles insert on opposite sides of the proximal phalanx of the middle finger, their simultaneous contraction will cancel each other’s movements, resulting in the middle finger remaining in the anatomical position.

The third dorsal interosseous muscle of hand can be tested by medially abducting the proximal phalanx of middle finger at the second metacarpophalangeal joint against resistance (Standring, 2016).

References

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