Palmar Interossei Muscles
By : Omar M. Subhi Altaie• NAME
The name indicates that these muscles can be seen from palmer side, which is anterior side of the hand in the anatomical position, the Latin word " interossei " means between the bones of metacarpals.
• GENERAL
This muscle group is one of four muscle groups of the Central Compartment Group of the hand, they are three muscles named one, two and three from lateral to medial (radial to ulnar) sides .they are deep between the bones as the name indicates.
Palmar interossei muscles are on the palmar surfaces of the metacarpal bones, in the interosseous compartment of the hand. the three palmar interossei adduct the fingers, whereas the first one pulls the index toward the middle finger (medially) and the other two pull the ring and little finger toward the middle finger (Laterally).
The first palmar interosseus muscle crosses the Metacarpophalgeal joint of the index finger on the medial side thus the first palmar interosseus adducts the index finger at the metacarpo-phalangeal joint.
The palmar interossei of the ring and little fingers cross the Metacarpophalangeal joints on the lateral side thus adducting them toward the midline (middle finger).
They also have other actions, they can flex the proximal phalanx at the same metacarpophalangeal joints. These muscles cross the proximal and distal interphalangeal joints of the index, ring and little fingers to apply their flexion and extension actions on them.
Palmar interossei muscles are on the palmar surfaces of the metacarpal bones, in the interosseous compartment of the hand. the three palmar interossei adduct the fingers, whereas the first one pulls the index toward the middle finger (medially) and the other two pull the ring and little finger toward the middle finger (Laterally).
The first palmar interosseus muscle crosses the Metacarpophalgeal joint of the index finger on the medial side thus the first palmar interosseus adducts the index finger at the metacarpo-phalangeal joint.
The palmar interossei of the ring and little fingers cross the Metacarpophalangeal joints on the lateral side thus adducting them toward the midline (middle finger).
They also have other actions, they can flex the proximal phalanx at the same metacarpophalangeal joints. These muscles cross the proximal and distal interphalangeal joints of the index, ring and little fingers to apply their flexion and extension actions on them.
• SUPPLY
• The nerve supply of the dorsal interossei manus is by the deep branches of the Ulanr nerve (C8, T1) which is one of the terminal branches of the brachial plexus.
• The blood supply of Palmar interossei muscles is from branches of the deep palmar arch and they are :
• princeps pollicis artery
• radialis indicis artery
• palmar metacarpal arteries
• proximal and distal perforating arteries
• common and proper palmar arteries.
• The blood supply of Palmar interossei muscles is from branches of the deep palmar arch and they are :
• princeps pollicis artery
• radialis indicis artery
• palmar metacarpal arteries
• proximal and distal perforating arteries
• common and proper palmar arteries.
• ORIGIN AND INSERTION
◇ ORIGIN
Three or four unipennate muscles whiches can be seen from the
• The first palmar interosseous (also known as pollical palmar interosseous muscle), originate from the spot near and above the fist metacarpo-phalangeal joint, at the medial side of the base of the 1st metacarpal bone. This particular muscle is often considered rudimentary.
• Second palmar interosseous arises from the medial side of the whole shaft of the second metacarpal bone of the index finger.
• The third palmar interosseous muscle simply originates from the lateral side of the shaft fourth metacarpal bone.
• 4th palmar interosseous simply originate from the lateral side of the shaft to the fifth metacarpal bone.
Three or four unipennate muscles whiches can be seen from the
• The first palmar interosseous (also known as pollical palmar interosseous muscle), originate from the spot near and above the fist metacarpo-phalangeal joint, at the medial side of the base of the 1st metacarpal bone. This particular muscle is often considered rudimentary.
• Second palmar interosseous arises from the medial side of the whole shaft of the second metacarpal bone of the index finger.
• The third palmar interosseous muscle simply originates from the lateral side of the shaft fourth metacarpal bone.
• 4th palmar interosseous simply originate from the lateral side of the shaft to the fifth metacarpal bone.
◇ INSERTION
• The first palmar interosseus muscle inserts into a sesamoid bone (near the thumb) on the medial and palmar side of the proximal phalanx of the thumb, as well as on its extensor expansion. Some triangular tissues connect the muscles to the bones .as mentioned, this muscle is not as functional as other interossei so we cannot see it very often.
• The second palmar interosseous muscle inserts into the lateral same side extensor expansion of the index finger at the base of the proximal phalanx.
• The third palmar interosseous muscle inserts together with the third lumbrical into the lateral base of the proximal phalanx of the fourth (ring) finger and on the extensor expansion on the lateral side of it.
• The fourth palmar interosseous muscle inserts with the fourth lumbrical into the base of the proximal phalanx of the little finger and on the extensor expansion on the lateral side of it.
• The first palmar interosseus muscle inserts into a sesamoid bone (near the thumb) on the medial and palmar side of the proximal phalanx of the thumb, as well as on its extensor expansion. Some triangular tissues connect the muscles to the bones .as mentioned, this muscle is not as functional as other interossei so we cannot see it very often.
• The second palmar interosseous muscle inserts into the lateral same side extensor expansion of the index finger at the base of the proximal phalanx.
• The third palmar interosseous muscle inserts together with the third lumbrical into the lateral base of the proximal phalanx of the fourth (ring) finger and on the extensor expansion on the lateral side of it.
• The fourth palmar interosseous muscle inserts with the fourth lumbrical into the base of the proximal phalanx of the little finger and on the extensor expansion on the lateral side of it.
• MOVEMENT & ACTION
The palmar interossei are always attached to the surfaces that face the middle finger of the metacarpals and phalanges; therefore a palmar interosseus muscle pulls the finger toward the middle finger which is considered as the midlineof the hand. This action is called the adduction of the fingers.
The first one of the palmar interosseus muscles crosses the Metacarpophalgeal joint of the index finger and pulls the proximal phalanx of this finger medially, because of the Location of the index finger lateral to the middle finger(midline of the hand) Therefore the first palmar interosseus adducts the index finger at the joint crossed by its fibres.
The other second and third palmar interossei cross the metacarpophalangeal joint of the ring and little fingers respectively on the other lateral side and pull these fingers laterally, toward the midline of the hand (middle finger). Therefore the second and third palmar interossei adduct the ring finger and the little finger at the joint has been mentioned.
It also crosses the proximal phalanx anteriorly, so when the muscle is contracted, it pulls the metacarpal of these fingers from the anterior aspect and that is called flexion of these fingers at the same metacarpophalangeal joints.
The palmar interossei can also extend the middle phalanx at its proximal interphalangeal joint and extend the distal phalanx at its distal interphalangeal joint, the reason behind this is because its fibres travel distally to cross these joints of the fingers two, four, and five respectively from the posterior side of them.
The first one of the palmar interosseus muscles crosses the Metacarpophalgeal joint of the index finger and pulls the proximal phalanx of this finger medially, because of the Location of the index finger lateral to the middle finger(midline of the hand) Therefore the first palmar interosseus adducts the index finger at the joint crossed by its fibres.
The other second and third palmar interossei cross the metacarpophalangeal joint of the ring and little fingers respectively on the other lateral side and pull these fingers laterally, toward the midline of the hand (middle finger). Therefore the second and third palmar interossei adduct the ring finger and the little finger at the joint has been mentioned.
It also crosses the proximal phalanx anteriorly, so when the muscle is contracted, it pulls the metacarpal of these fingers from the anterior aspect and that is called flexion of these fingers at the same metacarpophalangeal joints.
The palmar interossei can also extend the middle phalanx at its proximal interphalangeal joint and extend the distal phalanx at its distal interphalangeal joint, the reason behind this is because its fibres travel distally to cross these joints of the fingers two, four, and five respectively from the posterior side of them.
• REVERSE ACTION
As we know the normal action of any muscle is when the proximal attachment of the origin of that muscle is fixed and the distal attachment which is the insertion is the movable portion, but when the opposite of that happens we call it Reverse action
The distal attachments of these muscles are fixed for some particular reason. the reverse action of them occurs when the metacarpal of these fingers moves slightly to the proximal phalanx of the finger, at the metacarpophalangeal joint.
Extending the more proximal phalanges at the interphalangeal joints refers to extending the proximal phalanx at the Proximal interphalangeal joint and extension of the middle phalanx occurs at the distal interphalangeal joint.
The distal attachments of these muscles are fixed for some particular reason. the reverse action of them occurs when the metacarpal of these fingers moves slightly to the proximal phalanx of the finger, at the metacarpophalangeal joint.
Extending the more proximal phalanges at the interphalangeal joints refers to extending the proximal phalanx at the Proximal interphalangeal joint and extension of the middle phalanx occurs at the distal interphalangeal joint.
• ANTAGONIST FUNCTIONS
The palmar interossei slow and control abduction and extension of fingers two, four, and five at the Metacarpophalgeal joints and stabilize the joints.
They also slow flexion of the phalanges of the fingers two, four, and five at the proximal and distal interphalangeal joints.
They also slow flexion of the phalanges of the fingers two, four, and five at the proximal and distal interphalangeal joints.
• EXAMINATION
Testing the palmar interossei, by putting a sheet of paper between two fingers in a row, and asking the patient to prevent the examiner from pulling it toward him.
• CLINICAL NOTES
As known, these muscles are innervated by the deep branch of the Ulnar nerve; thus any injury or atrophy that might occur to the nerve in any area along its course will cause paralysis to the muscles that innervate.
Ulnar nerve compression is one of the most common neuropathies that occurs in people.
Furthermore, after that injury, a deformity called ulnar claw hand deformity when the affected fingers are flexed at the interphalangeal joints and extended at the Carpometacarpal joints.
That deformity is caused by a weakness in the interossei manus muscles, as well as third and fourth lumbricals. The other two fingers, the index and middle fingers are not very affected by the ulnar claw deformity; because their two lumbricals innervated by the median nerve which is intact in this case.
Ulnar nerve compression is one of the most common neuropathies that occurs in people.
Furthermore, after that injury, a deformity called ulnar claw hand deformity when the affected fingers are flexed at the interphalangeal joints and extended at the Carpometacarpal joints.
That deformity is caused by a weakness in the interossei manus muscles, as well as third and fourth lumbricals. The other two fingers, the index and middle fingers are not very affected by the ulnar claw deformity; because their two lumbricals innervated by the median nerve which is intact in this case.
• RELATIONS
These muscles are a little bit smaller than the dorsal interossei we can see them from the middle palmar surface deep between the bones.
The 1st palmar interosseous is located between the oblique head of the adductor pollicis muscle and from the posterior surface it faces the first dorsal interosseus manus.
The 2nd palmar interosseous is also covered by the oblique head of adductor pollicis, the tendons of the flexor digitorum profundus pass over the 3rd and 4th palmar interossei muscles whiches continue to reach the distal phalanges of the fourth and fifth fingers.
The 1st palmar interosseous is located between the oblique head of the adductor pollicis muscle and from the posterior surface it faces the first dorsal interosseus manus.
The 2nd palmar interosseous is also covered by the oblique head of adductor pollicis, the tendons of the flexor digitorum profundus pass over the 3rd and 4th palmar interossei muscles whiches continue to reach the distal phalanges of the fourth and fifth fingers.
● REFERENCES
• JOSEPH E. MUSCOLINO THE MUSCULAR SYSTEM MANUAL The Skeletal Muscles of the Human Body FOURTH EDITION 420-421, 431-434
• Keith L. Moore, Arthur F. Dalley, Anne M. R Clinically Oriented Anatomy (7th Edition) page779
• Snell's clinical anatomy by Region's (10th edition) page 321
• Palmar interossei , physiopedia https://www.physio-pedia.com/Palmar_Interossei#:~:text=The%20palmar%20interossei%20or%20volar,dorsal%20interossei%20of%20the%20hand.
• Keith L. Moore, Arthur F. Dalley, Anne M. R Clinically Oriented Anatomy (7th Edition) page779
• Snell's clinical anatomy by Region's (10th edition) page 321
• Palmar interossei , physiopedia https://www.physio-pedia.com/Palmar_Interossei#:~:text=The%20palmar%20interossei%20or%20volar,dorsal%20interossei%20of%20the%20hand.
● IMAGES REFERENCES
• cover image by https://www.alamy.com/illustration-of-the-muscles-of-the-hand-this-is-a-dorsal-superficial-view-of-the-muscles-of-the-hand-illustration-from-asklepios-atlas-of-the-human-image334945461.html
• Fig1 JOSEPH E. MUSCOLINO THE MUSCULAR SYSTEM MANUAL The Skeletal Muscles of the Human Body FOURTH EDITION page 432
• Fig2 Frank H. Netter, Atlas of Human Anatomy (7th edition) plate 455
• Fig3 Prosection 3 – The interossei and adductor pollicis of the hand. All in One Anatomy Review - Volume 1: Back and Upper Limb teach me anatomy website, https://teachmeanatomy.info/upper-limb/muscles/hand/
• Fig5 (A) Testing palmar interossei (ulnar nerve FIGURE 6.80. Testing interossei (ulnar nerve). Palmar interossei, Keith L. Moore, Arthur F. Dalley, Anne M. R Clinically Oriented page 779
• Fig1 JOSEPH E. MUSCOLINO THE MUSCULAR SYSTEM MANUAL The Skeletal Muscles of the Human Body FOURTH EDITION page 432
• Fig2 Frank H. Netter, Atlas of Human Anatomy (7th edition) plate 455
• Fig3 Prosection 3 – The interossei and adductor pollicis of the hand. All in One Anatomy Review - Volume 1: Back and Upper Limb teach me anatomy website, https://teachmeanatomy.info/upper-limb/muscles/hand/
• Fig5 (A) Testing palmar interossei (ulnar nerve FIGURE 6.80. Testing interossei (ulnar nerve). Palmar interossei, Keith L. Moore, Arthur F. Dalley, Anne M. R Clinically Oriented page 779
