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The interosseous muscles of the hand are a group of muscles found near the metacarpal bones that help control the fingers. They consist of four short muscles that attach to the adjacent sides of metacarpals 1-4. The dorsal interossei muscles are responsible for abducting the digits 2-4, while the palmar interossei muscles adduct the digits towards the 3rd digit. These muscles are considered voluntary and play a key role in hand function, including grip and pinch. To examine the first dorsal interosseous muscle, a patient can be instructed to place their palm flat on a table and abduct their index finger against the examiner's resistance. This test allows for the observation and palpation of the muscle belly and is a reliable test for the ulnar nerve.
| Characteristics | Values |
|---|---|
| Location | Between the metacarpal bones |
| Function | Abducting the digits away from the third digit (axial line) |
| Number of Muscles | Four |
| Shape | Feather-like |
| Blood Supply | Dorsal metacarpal branches of the dorsal carpal anastomosis |
| Innervation | Deep ulnar branch of the ulnar nerve |
| Testing | Place the patient's palm flat on a table and ask them to abduct their index finger against the examiner's resistance |
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What You'll Learn
How to examine the first dorsal interosseous muscle
The first dorsal interosseous muscle is one of four interossei dorsales muscles, which occupy the intervals between the metacarpal bones. It is a bipenniform muscle, arising by two heads from the adjacent sides of the metacarpal bones. The first dorsal interosseous muscle is larger than the others.
To examine the first dorsal interosseous muscle, the following steps can be taken:
- Ask the patient to place their palm flat on a table.
- Instruct the patient to abduct their index finger against the examiner's resistance. This action will test the first dorsal interosseous muscle, which is responsible for abducting the proximal phalanx of the index finger (drawing it away from the longitudinal axial line of the middle finger) at the second metacarpophalangeal joint.
- During this action, the muscle belly can be seen and palpated, making it a reliable test for the ulnar nerve.
The first dorsal interosseous muscle can also be examined through an anatomical cadaver study, as seen in some research.
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How to examine the second dorsal interosseous muscle
The second dorsal interosseous muscle is located in the interosseous compartment of the hand and is involved in multiple actions. It is a short, bipennate skeletal muscle, which is located posterior to the first palmar interosseous and second lumbrical muscles of the hand.
To examine the second dorsal interosseous muscle, the patient's hand must be correctly positioned. The patient's palm should be placed flat on a table, with their middle finger outstretched. The patient should then be instructed to abduct the middle finger (i.e., draw it laterally away from the longitudinal axial line of the finger) at the second metacarpophalangeal joint against resistance. This movement will test the function of the second dorsal interosseous muscle.
The second dorsal interosseous muscle can also be visually examined. The muscle belly can be seen and palpated, and this examination is a reliable test for the ulnar nerve. The muscle fibres travel inferiorly to the middle finger and insert via a short tendon onto the lateral aspect of the base of the proximal phalanx of the middle finger.
The second dorsal interosseous muscle receives its blood supply from the second dorsal metacarpal artery, which arises from the dorsal carpal arch. This artery bifurcates into the dorsal digital artery and anastomoses with the common palmar digital arteries, forming a complex vascular network.
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How to examine the palmar interossei muscles
The palmar interossei muscles are a group of three or four short, unipennate muscles on the palmar surface of the hand. They occupy the spaces between the metacarpal bones and are attached to the index, ring, and little fingers.
To examine the palmar interossei muscles, you can instruct the patient to perform a Wartenberg's sign test. The patient is asked to adduct all fingers. A positive test, indicated by the abduction of the fifth finger relative to all other digits, implies weakness of the third palmar interosseous muscle and fourth lumbrical. Another way to examine the palmar interossei is to instruct the patient to hold a sheet of paper between any of the second through fifth digits. Dropping the piece of paper is indicative of palmar interossei weakness.
The first palmar interosseous muscle, also known as the pollical palmar interosseous, is often considered rudimentary and rarely functional on its own. It arises on the ulnar side of the base of the first metacarpal bone and inserts into a sesamoid bone on the ulnar side of the proximal phalanx of the thumb. The second palmar interosseous arises from the entire length of the second metacarpal bone and is inserted into the extensor expansion of the index finger. The third and fourth palmar interossei originate at the lateral aspect of the fourth and fifth metacarpals. The fourth palmar interosseous inserts into the base of the proximal phalanx of the little finger and its extensor expansion.
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How to examine the dorsal interossei muscles
The dorsal interossei muscles are a group of four paired intrinsic muscles of the hand located between the metacarpals. They are short, bipennate muscles that arise by two heads, which converge to attach onto a central tendon, giving them a feather-like shape. The first dorsal interosseous muscle is the largest and strongest of the dorsal interossei and can be easily felt in the web between the thumb and index finger.
To examine the dorsal interossei muscles, the patient's palm is placed flat on a table, and they are asked to abduct their index finger against the examiner's resistance. This test is for the ulnar nerve, and the muscle belly can be seen and palpated. The remaining three muscles can be palpated between the metacarpal bones and the tendon of the extensor digitorum muscle.
The dorsal interossei muscles function to abduct the index, middle, and ring fingers (digits 2-4) and assist in flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal (IP) joints. They receive their nerve supply from the deep branch of the ulnar nerve, derived from nerve roots C8 and T1, with T1 being the major innervating segment.
The dorsal interossei muscles are predominantly in the proximal group, making them more effective at the MCP joints than the palmar interossei. When the MCP joints are flexed, the position of the interossei moves away from the flexion-extension axes of the MCP joints, and the collateral ligaments of the MCP joints increase the force of flexion, resulting in a strong grip.
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How to examine the interosseous muscles of the hand
The interosseous muscles of the hand are intrinsic muscles that control the fingers and are found near the metacarpal bones. They consist of four or three palmar interossei and four dorsal interossei muscles.
Examining the Palmar Interossei Muscles
To examine the palmar interossei, a patient can be instructed to hold a sheet of paper between any of the second through fifth digits. If the patient drops the piece of paper, this indicates palmar interossei weakness.
Examining the Dorsal Interossei Muscles
The dorsal interossei muscles can be palpated in the dorsum of the hand on resisted abduction of the fingers between the metacarpals. The first dorsal interosseous muscle can be tested by placing the patient's palm flat on a table and asking the patient to abduct their index finger against the examiner's resistance. The muscle belly can be both seen and palpated and is a reliable test for the ulnar nerve.
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Frequently asked questions
The first dorsal interosseous muscle can be tested by placing the patient's palm flat on a table and asking the patient to abduct their index finger against the examiner's resistance. The muscle belly can be seen and palpated and is a reliable test for the ulnar nerve.
The dorsal interossei muscles consist of four short muscles that attach to the adjacent sides of metacarpals 1-4. Their function is to abduct the digits 2-4, as well as to assist in flexion of these fingers at the metacarpophalangeal (MCP) joints and in extension at the interphalangeal (IP) joints.
The palmar interossei muscles are strong adductors of fingers and assist in flexion of the metacarpophalangeal joints and extension of the interphalangeal joints.
