The extensor retinaculum (dorsal carpal ligament, or posterior annular ligament) is a thickened portion 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 ole ...

that holds the

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

s of the extensor muscles 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 used to describe the entire appendage of the upper limb, but which in anatomy, techn ...

, just

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

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#Characteristics, koala (which has two thumb#O ...

. It is continuous with the

palmar carpal ligament The palmar carpal ligament (also volar carpal ligament or ''Guyon's Tunnel'') is a thickened portion of antebrachial fascia on anterior/palmar side of the wrist which - together with the flexor retinaculum of the hand - retains the tendons of most ...

(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 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 as the carpal ...

. 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.

Relations

There are six separate synovial sheaths run beneath the extensor retinaculum: (1st) abductor pollicis longus and extensor pollicis brevis tendons, (2nd) extensor carpi radialis longus and brevis tendons, (3rd) extensor pollicis longus tendon, (4th) extensor digitorium communis and extensor indicis proprius tendons, (5th) extensor digiti minimi tendon and (6th) extensor carpi ulnaris tendon. On the dorsal side of the hand, the

corresponds in location and structure to the extensor retinaculum, both being formations of the antebrachial fascia and therefore continuous. Consequently, the flexor retinaculum is commonly referred to as the ''transverse carpal ligament'' to avoid confusion.

Histology

Structurally, the retinaculum consists of three layers. The deepest layer, the gliding layer, consists of

hyaluronic acid Hyaluronic acid (; abbreviated HA; conjugate base hyaluronate), also called hyaluronan, is an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues. It is unique among glycosaminog ...

-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