Palmaris longus muscle

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Palmaris longus muscle
Gray1231.png
Front of right upper extremity. (Palmaris longus labeled at bottom, second from left.)
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Transverse section across distal ends of radius and ulna. (Palmaris longus labeled at center top.)
Latin musculus palmaris longus
Gray's p.446
Origin medial epicondyle of humerus (common flexor tendon)
Insertion palmar aponeurosis
Artery ulnar artery
Nerve median nerve
Actions wrist flexor
Antagonist Extensor carpi radialis brevis, Extensor carpi radialis longus, Extensor carpi ulnaris
Anatomical terms of muscle

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 number varies greatly in African, Asian, and Native American populations.[1] Absence of this muscle does not have an effect on grip strength;[2] however, lack of the palmaris longus muscle is disadvantageous in that its tendon cannot be harvested as a graft if necessary. Some evolutionary scientists maintain that as it is no longer needed by humans, evolution is dispensing with the tendon.[citation needed]

The palmaris longus muscle can be palpated by touching the pads of the fifth finger and thumb whilst flexing the wrist. The tendon, if present, will be visible in the midline of the anterior wrist.

Structure[edit]

It is a slender, fusiform muscle, lying on the medial side of the flexor carpi radialis.[3]

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.[3]

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.[3]

Innervation[edit]

The palmaris longus is supplied by the median nerve.[4]

Variation[edit]

The palmaris longus muscle is a variable muscle. The most common variation is its absence. Several in vivo and in vitro studies have documented the prevalence of absence of the PL tendon in different ethnic groups. The overall prevalence of the absence of the PL tendon in Caucasian populations (European and North American) has been reported between 5.5 and 24% . On the other hand, the overall prevalence of absence of the PL tendon in Asian populations (Chinese, Japanese, Indian, Turkish, Malaysian) has been reported between 4.6 and 26.6%.[5]

There are also variations related to its form. 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, or missing entirely. 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.

Clinical significance[edit]

Use in tendon grafts[edit]

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.[6] When a tendon becomes ruptured in the wrist, the palmaris longus tendon may be removed from the flexor retinaculum 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.[7]

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.[8] Using the patient’s own tendon is advantageous, as it does not introduce foreign material into the body.

Additional images[edit]

Front of the left forearm: Superficial muscles 
Cross-section through the middle of the forearm 
Transverse section across the wrist and digits 
The palmar aponeurosis 
The muscles of the thumb 
The muscles of the left hand: Palmar surface 
The radial and ulnar arteries 
Palmaris Longus tendon visible on the anterior aspect of the wrist 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Palmaris longus muscle 
Muscles of upper limb.Cross section. 

See also[edit]

This article uses anatomical terminology; for an overview, see anatomical terminology.

References[edit]

This article incorporates text from a public domain edition of Gray's Anatomy.

  1. ^ Sebastin SJ, Puhaindran ME, Lim AY, Lim IJ, Bee WH (October 2005). "The prevalence of absence of the palmaris longus--a study in a Chinese population and a review of the literature". Journal of Hand Surgery 30 (5): 525–7. doi:10.1016/j.jhsb.2005.05.003. PMID 16006020. 
  2. ^ Sebastin SJ, Lim AY, Bee WH, Wong TC, Methil BV (August 2005). "Does the absence of the palmaris longus affect grip and pinch strength?". Journal of Hand Surgery 30 (4): 406–8. doi:10.1016/j.jhsb.2005.03.011. PMID 15935531. 
  3. ^ a b c Gray's Anatomy (1918), see infobox
  4. ^ Drake, Richard L.; Vogl, Wayne; Mitchell, Adam W. M. (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. p. 693. ISBN 978-0-8089-2306-0. 
  5. ^ Kose O, Adanir O, Cirpar M, Kurklu M, Komurcu M (May 2009). "The prevalence of absence of the palmaris longus: a study in Turkish population". Archives of Orthopaedic and Trauma Surgery 129 (5): 609–11. doi:10.1007/s00402-008-0631-9. PMID 18418616. 
  6. ^ Carroll, Will; Gorman, Thomas (June 2009). "Inside Tommy John Surgery". Baseball Prospectus. Retrieved February 2012. 
  7. ^ Thejodhar P, Potu BK, Vasavi RG (January 2008). "Unusual palmaris longus muscle". Indian Journal of Plastic Surgery 41 (1): 95–6. doi:10.4103/0970-0358.41125. PMC 2739544. PMID 19753215. 
  8. ^ Wheeless, Clifford R (1996. Web. 04 Dec. 2009). "Palmaris Longus Tendon Graft Harvest". Wheeless' Textbook of Orthopaedics. Retrieved February 2012. 

External links[edit]