The extensor retinaculum (dorsal carpal ligament, or posterior annular ligament) is an anatomical term for the thickened part of the

antebrachial fascia The antebrachial fascia (antibrachial fascia or deep fascia of forearm) 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 olec ...

that holds the

tendons A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

of the

extensor muscles In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extendin ...

in place. It is located on the back of the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anat ...

, just

proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

to the

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "h ...

. It is continuous with the

palmar carpal ligament The palmar carpal ligament (also volar carpal ligament or ''Guyon's Tunnel'') is the thickened portion of antebrachial fascia on the anterior of the wrist. It is officially unnamed.Moore, Keith L., Arthur F. Dalley II: ''Clinically Oriented Anatom ...

, which is located on the anterior side of the forearm.

Structure

The extensor retinaculum is a strong, fibrous band, extending obliquely downward and medialward across the back of the

wrist In human anatomy, the wrist is variously defined as (1) the Carpal bones, carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known ...

. It consists of part of the

deep fascia Deep fascia (or investing fascia) is a fascia, a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments. This fibrous connective tissue interpenetrates and surrounds the m ...

of the back of the

, strengthened by the addition of some transverse fibers. The extensor retinaculum is attached laterally to the lateral margin of the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

. However, it is not attached to the

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

, as the distance between these two bones varies with

supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

and

pronation Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

of the

. Instead the medial attachment is to the

pisiform bone The pisiform bone ( or ), also spelled pisiforme (from the Latin ''pisifomis'', pea-shaped), is a small knobbly, sesamoid bone that is found in the wrist. It forms the ulnar border of the carpal tunnel. Structure The pisiform is a sesamoid bone, ...

and

triquetral bone The triquetral bone (; also called triquetrum, pyramidal, three-faced, and formerly cuneiform bone) is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones. It is on the ulnar side of the ...

. Other authors may state the medial attachment of extensor retinaculum with the

fifth metacarpal bone The fifth metacarpal bone (metacarpal bone of the little finger or pinky finger) is the most medial and second-shortest of the metacarpal bones. Surfaces It presents on its base one facet on its superior surface, which is concavo-convex and artic ...

and the

pisometacarpal ligament The pisometacarpal ligament joins the pisiform to the base of the fifth metacarpal bone. It is a continuation of the tendon of the flexor carpi ulnaris The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist ...

. The retinaculum is also attached in its passage across the wrist, to the ridges on the dorsal surface of the radius. There are six separate synovial sheaths run beneath the extensor retinaculum: opponens pollicis tendon, abductor pollicis tendon, extensor pollicis longus, extensor digitorum longus, extensor digiti minimi, and extensor carpi ulnaris.

Histology

Structurally, the retinaculum consists of three layers. The deepest layer, the gliding layer, consists of hyaluronic acid-secreting cells. The thick middle layer consists of interspersed elastin fibers, collagen bundles, and fibroblasts. The most superficial layer is made up of loose connective tissue which contains vascular channels. Combined these three layers create a smooth gliding surface as well as mechanically strong tissue which prevents tendon bowstringing. The extensor retinaculum of the foot has similar structure.

Clinical significance

Studies conducted on the retinaculum have exhibited it to have several possible surgical treatments uses. A graft of the extensor retinaculum was shown to be useful in treating boxer's knuckle when direct repair of the damaged capsule is not possible. Because of their similarities in histological structure, studies also show the extensor retinaculum to be a reasonable biological replacement for reconstruction of a deficient annular pulley.

Additional images

File:Gray421.png, Transverse section across distal ends of radius and ulna. File:Slide2val.JPG, Extensor retinaculum of the hand.Deep dissection.

References

External links

* {{Authority control Human anatomy