The oblique cord is a

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

between 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 ...

r and

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 ...

bones in 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 ...

near the

elbow The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the media ...

. It takes the form of a small, flattened band, extending downward and lateralward, from the lateral side of the

ulnar tuberosity The tuberosity of the ulna is a rough eminence on the proximal end of the ulna. It occurs at the junction of the antero-inferior surface of the coronoid process with the front of the body. It provides an insertion point to a tendon of the brachial ...

at the base of the coronoid process to the

a little below the

radial tuberosity Beneath the neck of the radius, on the medial side, is an eminence, the radial tuberosity; its surface is divided into: * a ''posterior, rough portion'', for the insertion of the tendon of the biceps brachii. * an ''anterior, smooth portion'', on w ...

. Its fibers run in the opposite direction to those of the

Interosseous membrane of the forearm The interosseous membrane of the forearm (rarely middle or intermediate radioulnar joint) is a fibrous sheet that connects the interosseous margins of the radius and the ulna. It is the main part of the radio-ulnar syndesmosis, a fibrous joint bet ...

. It is called by other names including oblique ligament, chorda obliqua, radio-ulnar ligament, chorda oblique antebrachii anterior, proximal interosseous band, dorsal oblique accessory cord, proximal band of the interosseous membrane, superior oblique ligament, oblique ligament proper, round ligament, and ligament of Weitbrecht. It has no known function and can be cut without apparent consequence.

Structure

A study upon the arms of 38 people found that its mean length is 3.4 cm (range 2.4 to 4.2 cm) and in most people it tapers from the ulna to the radius end, being at the ulna 9 mm, in its middle, 7mm and its radius end 4 mm.

Variation

The shape and form of the ligament have been found in humans

cadaver A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Stud ...

s to vary from a rounded cord to a flat membrane. Further, it is not found in all humans being variably found to be absent in half of arms,Tubbs RS, O'Neil JT Jr, Key CD, Zarzour JG, Fulghum SB, Kim EJ, Lyerly MJ, Shoja MM, George Salter E, Jerry Oakes W. (2007). The oblique cord of the forearm in man. Clin Anat. 20(4):411–5. and a third or 15% of people.Skahen JR 3rd, Palmer AK, Werner FW, Fortino MD. (1997). The interosseous membrane of the forearm: anatomy and function. J Hand Surg Am. 22(6):981–5. It is found in most

primates Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...

though not in the family of

New World monkey New World monkeys are the five families of primates that are found in the tropical regions of Mexico, Central and South America: Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae. The five families are ranked together as the Ceboidea ( ...

s that includes

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

and

woolly monkey The woolly monkeys are the genus ''Lagothrix'' of New World monkeys, usually placed in the family Atelidae. Both species in this genus originate from the rainforests of South America. They have prehensile tails and live in relatively large soci ...

s called

ateline The Atelinae are a subfamily of New World monkeys in the family Atelidae, and includes the various spider and woolly monkeys. The primary distinguishing feature of the atelines is their long prehensile tails, which can support their entire body w ...

Function

It has been suggested to strengthen the interosseus membrane proximally, provide restraint for the rotatory movements of the forearm, or that the ligament may stop bone bending and preventing buckling failure.Martin BF.(1958)
The oblique cord of the forearm.
J Anat. 92(4):609–15. However, due to the orientation of its fibers, the oblique cord is unlikely to transfer force due to limb loading from the radius to the ulna.Patel BA. (2005). Form and function of the oblique cord (chorda obliqua) in anthropoid primates.Primates. 46(1):47–57. One recent comparative study upon primates concluded:

The oblique cord does not limit supination, nor does it seem to have a role in preventing radial buckling failure or reducing bending strain. What, then, is the oblique cord for? The oblique cord may simply be an additional tie between the radius and ulna aiding other soft tissue structures such as the annular ligament and interosseous membrane. Additionally, the oblique cord may prevent anterior shearing of the proximal radius under extreme compressive loads.

A study on humans concluded that it "appears insignificant in stability of the proximal forearm." It has been suggested that its presence in modern humans may be a

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

body part for a

biped Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' a ...

that was important due to the load-bearing function of the upper limb in evolutionarily earlier

quadruped Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuor' ...

human ancestors.

Notes

External links

* {{Authority control Ligaments of the upper limb