Palmaris longus muscle
Encyclopedia
The palmaris longus is seen as a small tendon between the flexor carpi radialis and the flexor carpi ulnaris, although it is not always present. The muscle is absent in about 14 percent of the population, however this varies greatly with ethnicity. Absence of palmaris does not have any known effect on grip strength.
Palmaris longus can be palpated by touching the pads of the fifth and first fingers and flexing the wrist. The tendon, if present, will be very visible.
It arises from the medial epicondyle
of the humerus
by the common flexor tendon
, from the intermuscular septa between it and the adjacent muscles, and from the antebrachial fascia
.
It ends in a slender, flattened tendon, which passes over the upper part of the flexor retinaculum, and is inserted into the central part of the flexor retinaculum and lower part of the palmar aponeurosis
, frequently sending a tendinous slip to the short muscles of the thumb
.
The palmaris longus tendon is responsible for exposing the claws in other mammals.
The muscle may be double.
Slips of origin from the coronoid process
or from the radius have been seen.
Partial or complete insertion into the fascia of the forearm, into the tendon of the Flexor carpi ulnaris and pisiform bone
, into the scaphoid, and into the muscles of the little finger
have been observed.
and grafted to take the place of the ruptured tendon. The tendons most commonly replaced or supplemented by the palmaris longus tendon when ruptured are the long flexors of the fingers and the flexor pollicis longus tendon.
The palmaris longus muscle itself is a weak flexor, and provides no substantial flexing force that would inhibit movement in the wrist if its tendon was cut and moved elsewhere. If the palmaris longus muscle is not available for harvesting in an individual, the anatomically analogous plantaris muscle in the leg may be taken instead. Using the patient’s own tendon is advantageous, as it does not introduce foreign material into the body.
Palmaris longus can be palpated by touching the pads of the fifth and first fingers and flexing the wrist. The tendon, if present, will be very visible.
Course
It is a slender, fusiform muscle, lying on the medial side of the flexor carpi radialis.It arises from the medial epicondyle
Medial epicondyle
Medial epicondyle can refer to:* Medial epicondyle of the humerus * Medial epicondyle of the femur...
of the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
by the common flexor tendon
Common flexor tendon
The common flexor tendon is a tendon shared by a number of superficial flexor muscles in the forearm. It attaches to the medial epicondyle of the humerus....
, from the intermuscular septa between it and the adjacent muscles, and from the antebrachial fascia
Antebrachial fascia
The antebrachial fascia continuous above with the brachial fascia, is a dense, membranous investment, which forms a general sheath for the muscles in this region; it is attached, behind, to the olecranon and dorsal border of the ulna, and gives off from its deep surface numerous intermuscular...
.
It ends in a slender, flattened tendon, which passes over the upper part of the flexor retinaculum, and is inserted into the central part of the flexor retinaculum and lower part of the palmar aponeurosis
Palmar aponeurosis
The palmar aponeurosis invests the muscles of the palm, and consists of central, lateral, and medial portions.-Central portion:The central portion occupies the middle of the palm, is triangular in shape, and of great strength and thickness....
, frequently sending a tendinous slip to the short muscles of the thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
.
The palmaris longus tendon is responsible for exposing the claws in other mammals.
Variation
The palmaris longus is a variable muscle, absent in about 16 percent of Caucasians, and less frequently absent in other populations. It may be tendinous above and muscular below; or it may be muscular in the center with a tendon above and below; or it may present two muscular bundles with a central tendon; or finally it may consist solely of a tendinous band.The muscle may be double.
Slips of origin from the coronoid process
Coronoid process
The Coronoid process can refer to:* The coronoid process of the mandible, part of the ramus mandibulae of the mandible...
or from the radius have been seen.
Partial or complete insertion into the fascia of the forearm, into the tendon of the Flexor carpi ulnaris and pisiform bone
Pisiform bone
The pisiform bone is a small knobbly, pea-shaped wrist bone.The pisiform bone is found in the proximal row of the carpus. It is located where the ulna joins the carpus...
, into the scaphoid, and into the muscles of the little finger
Little finger
The little finger, often called the pinky in American English, pinkie in Scottish English , or small finger in medicine, is the most ulnar and usually smallest finger of the human hand, opposite the thumb, next to the ring finger.-Muscles:There are four muscles that...
have been observed.
Use in tendon grafts
The palmaris longus muscle is the most popular for use in tendon grafts for the wrist due to the length and diameter of the palmaris longus tendon, and the fact that it can be used without producing any functional deformities. When a tendon becomes ruptured in the wrist, the palmaris longus tendon may be removed from the flexor retinaculumFlexor retinaculum
Flexor retinaculum may be:* Flexor retinaculum of the hand, the retinaculum flexorum manus* Flexor retinaculum of the foot, the retinaculum musculorum flexorum pedis...
and grafted to take the place of the ruptured tendon. The tendons most commonly replaced or supplemented by the palmaris longus tendon when ruptured are the long flexors of the fingers and the flexor pollicis longus tendon.
The palmaris longus muscle itself is a weak flexor, and provides no substantial flexing force that would inhibit movement in the wrist if its tendon was cut and moved elsewhere. If the palmaris longus muscle is not available for harvesting in an individual, the anatomically analogous plantaris muscle in the leg may be taken instead. Using the patient’s own tendon is advantageous, as it does not introduce foreign material into the body.