PALMAR INTEROSSEI: ANATOMY, CLINICAL CONSIDERATIONS - ANATOMY AND PHYSIOLOGY - 2025

The palmar interossei are three paired muscles located in the hand, specifically between the metacarpal bones. They are numbered II, IV and V and are part of the intrinsic muscles of the hand.

They originate at the base of the metacarpal bones of the second, fourth, and fifth fingers. A first toe interosseus can be found in some people, but it is a fickle muscle.

From Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See "Book" section below) Bartleby.com: Gray's Anatomy, Plate 429, Public Domain, https://commons.wikimedia.org/w/index. php? curid = 552363

Its main function is to adduct the fingers, that is, to bring the fingers closer to the center. Additionally, they contribute to the flexion of the metacarpal joint with the phalanges of the fingers and to the extension of the interphalangeal joints.

The blood supply to these muscles is provided by the palmar arteries of the metacarpus that come from the palmar arterial deep arch. The palmar interossei are innervated by the deep branch of the ulnar nerve, which has mainly motor functions.

Intrinsic muscles of the hand

34 muscles act in the hand that work synergistically to achieve coordinated movements.

The extrinsic muscles are those that have their origin in the forearm while the intrinsic muscles originate in the bones and aponeurosis of the carpus and metacarpus.

By User: James Bedford - File: Gray418.png, Public Domain, The interosseous muscles are part of the intrinsic muscle group of the hand. There are dorsal interossei and palmar interossei.

The dorsal interossei are responsible for separating the fingers, that is, they act in the abduction movement. On the contrary, the palmar interossei are responsible for bringing the fingers closer to the center, a movement known as adduction.

The intrinsic muscles of the hand receive their blood supply from a complex vascular network formed by arches that are formed by the junction between branches of the radial and ulnar arteries.

Palmar interosseous muscles: anatomy

The palmar interossei are four muscles that are located between the bones of the palm of the hand called metatarsals.

The first muscle, associated with the thumb, is rudimentary and is present in approximately 85% of the population. The rest of the muscles are responsible for the mobility of the index, ring and little fingers.

Each of the muscles originates from the base of the respective metacarpal bone, which means that the fourth muscle attaches to the base of the metacarpus of the fourth toe, the second to the second toe, and the fifth to the fifth toe.

By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See «Book» section below) Bartleby.com: Gray's Anatomy, Plate 219, Public Domain, https://commons.wikimedia.org/w/index. php? curid = 108245

They make a short route that occupies the entire bone and ends in the proximal phalanx of the finger that corresponds to mobilize them.

Features

The palmar interosseous muscles are responsible for the adduction of the respective fingers. This movement implies the approach or closing of the fingers towards the center.

In addition, they are muscles that contribute to flexion movements of the metacarpophalangeal joint, between the hand and fingers, and the extension of the distal interphalangeal joint, the distal finger joint.

Irrigation and innervation

The blood vessels that are responsible for supplying the blood requirement of the palmar interosseous muscles come from the ulnar or ulnar artery.

In the palm of the hand, the radial and ulnar arteries create an intricate vascular network that forms arterial arches by the union of different collateral branches of both.

By Rhcastilhos - Gray1237.png, Public Domain, These arches ensure adequate vascularization of the palmar interosseous muscles through specific collaterals for them.

As for the neurological part, this is given by the deep branch of the ulnar nerve, also called ulnar, which gives specific neurological branches for each of these muscle segments.

Clinical considerations

The ulnar or ulnar nerve, through its deep branch, is in charge of supplying the specific neurological branches for each interosseous muscle, ensuring its proper functioning.

When there is any injury to this nerve, whether from impingement, trauma or compression, the palmar interosseous muscles can be seriously affected.

Ulnar nerve entrapment

Ulnar nerve entrapment is a condition caused by compression of the ulnar nerve in any part of its path.

The brachial plexus is a neurological structure that arises from the C8-T1 medullary roots. Its medial fascicle gives rise to the ulnar nerve.

By Brachial_plexus_2.svg: * Brachial_plexus.jpg: Original uploader was Mattopaedia at en.wikipediaderivative work: Captain-n00dle (talk), MissMJderivative work: Ninovolador (talk) - Brachial_plexus_2.svg, Public Domain, https: //commons.wikimedia. org / w / index.php? curid = 11770485

The ulnar is a nerve that arises at the shoulder joint, is located medially and accompanies the brachial artery throughout its entire course and continues with its ulnar division.

The ulnar nerve reaches the hand where it divides into superficial and deep branches that supply innervation to the regional muscles.

Ulnar nerve entrapment can occur at any point along its path, whether from direct trauma, fractures, or dislocations.

By Gray, Henry, 1825-1861; Pick, T. Pickering (Thomas Pickering), 1841-1919, ed; Keen, William W. (William Williams), b. 1837 - https://www.flickr.com/photos/internetarchivebookimages/14763598044/Source book page: https://archive.org/stream/anatomydescripti1887gray/anatomydescripti1887gray#page/n765/mode/1up, No restrictions, https: / /commons.wikimedia.org/w/index.php?curid=44027332

Another mechanism by which this pathology can be observed is by fibrosis of the points, in which the nerve passes through fibrous and bone structures.

At the elbow, the ulnar nerve passes medially through the epicondyle of the humerus through an aponeurotic tunnel.

In people who overload this joint with repetitive flexion and extension movements, inflammation of this structure can occur causing pressure on the nerve.

In the chronic stage of this condition, the so-called ulnar claw can be seen, which is a deformity of the hand caused by compression of the nerve and the paralysis of the muscles innervated by it.

By Mcstrother - Own work, CC BY 3.0,

Cubital tunnel syndrome

The ulnar nerve continues its journey through the forearm and when it reaches the wrist joint it passes, together with the ulnar artery, through a semi-rigid fibrous canal approximately 4 centimeters long, called the ulnar canal or Guyon's canal.

By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See «Book» section below) Bartleby.com: Gray's Anatomy, Plate 815, Public Domain, https://commons.wikimedia.org/w/index. php? curid = 541671

Cubital tunnel syndrome is, after carpal tunnel syndrome, the most common cause of neuropathies of the hand.

It is a condition that can be seen in cyclists, bikers, office workers, and anyone who performs repetitive flexion and extension movements of the wrist for long periods of time.

Symptoms consist of paraesthetic sensations of the hand, the patient experiencing the sensation of the hand asleep at times or even pricks or pressure.

In the chronic stages of this syndrome, atrophy of the muscles innervated by the ulnar nerve, including the palmar interossei, can be observed, even causing paralysis of the hand.

At this stage, the only treatment option for the patient is surgical resolution.

References

1. Valenzuela, M; Bordoni, B. (2019). Anatomy, Shoulder and Upper Limb, Hand Palmar Interosseous Muscle. StatPearls; Treasure Island (FL). Taken from: ncbi.nlm.nih.gov
2. Okwumabua, E; Bordoni, B. (2019). Anatomy, Shoulder and Upper Limb, Hand Muscles. StatPearls; Treasure Island (FL). Taken from: ncbi.nlm.nih.gov
3. Chauhan, MM; Das, J. (2019). Ulnar Tunnel Syndrome. StatPearls; Treasure Island (FL). Taken from: ncbi.nlm.nih.gov
4. Dy, C. J; Mackinnon, SE (2016). Ulnar neuropathy: evaluation and management. Current reviews in musculoskeletal medicine, 9 (2), 178–184. Taken from: ncbi.nlm.nih.gov
5. Lane, R; Nallamothu, SV. (2019). Claw Hand. StatPearls; Treasure Island (FL). Taken from: ncbi.nlm.nih.gov
6. Olave, E; del Sol, M. (2008). Ulnar Nerve Distribution: Innervation of the Interosseous, Lumbrical and Adductor Thumb Muscles. International Journal of Morphology, 26 (4), 959-962. Taken from: scielo.conicyt.cl