The distal radioulnar articulation (also known as the distal radioulnar joint, or inferior radioulnar joint) is a synovial

pivot Pivot may refer to: *Pivot, the point of rotation in a lever system *More generally, the center point of any rotational system *Pivot joint, a kind of joint between bones in the body *Pivot turn, a dance move Companies *Incitec Pivot, an Austra ...

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

between the two 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 ...

; 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 ...

and

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 ...

. It is one of two joints between the radius and ulna, the other being the proximal radioulnar articulation. The joint features an

articular disc The articular disk (or disc) is a thin, oval plate of fibrocartilage present in several joints which separates synovial cavities. This separation of the cavity space allows for separate movements to occur in each space. The presence of an articula ...

, and is reinforced by the palmar and dorsal radioulnar ligaments.

Structure

The distal radioulnar articulation is formed by the

head of 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 ...

, and the ulnar notch of the distal

Articular disc

The joint features a triangular

that is attached to the inferior margin of the ulnar notch by its base, and to a fossa at the base of the styloid process of the ulna by its apex. The articular disc acts to firmly bind the distal extremities of the two bones together.

Ligaments

The articulation is reinforced by the palmar radioulnar ligament, and dorsal radioulnar ligament.

Function

The function of the radioulnar joint is to lift and maneuver weight load from the distal radioulnar joint to be distributed across the forearm’s

and

as a load-bearing joint. Supination of the radioulnar joint can move from 0 degrees neutral to approximately 80-90 degrees where pronation of the radioulnar joint can move from 0 degrees neutral to approximately 70-90 degrees. Supination (palms facing up) vs. pronation (palms facing down). Muscles that contribute to function are all supinator ( biceps brachii,

brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by ...

, and supinator) and pronator muscles (

, pronator quadratus, and pronator peres).

Clinical significance

Injuries to the distal radioulnar articulation often result from falls onto an outstretched hand. Injury can occur with concurrent fracture of the distal radius, the ulna, or can be isolated. For the upper limit of the distal radioulnar distance, sources vary between 2 mm and 5 mm. A classification system has been proposed by Estaminet and colleagues.Estaminet et al. Estaminet-Klassifikation von distal radioulnar Aussprache-Trauma. 20. Jahresversammlung der europäischen Orthopädischen Forschungsgesellschaft (EORS 2012), am 26–28 September, Amsterdam, Die Niederlande

Estaminet Classification

Estaminet classified injuries of the distal radioulnar articulation into four categories with two subclasses: purely ligamentous (subclass A) and those with associated boney injury (subclass B). * Estaminet I - Attenuation on MRI only * Estaminet II - Volar distal radioulnar ligament is involved. Unstable in supination. Fixation should be in pronation. * Estaminet III - Dorsal distal radioulnar ligament is involved. Unstable in pronation. Fixation should be in supination. * Estaminet IV - Both ligaments are involved. Unstable in both supination and pronation. Fixation is in neutral.

Additional images

Image:RightHumanPosteriorDistalRadiusUlnaCarpals.jpg, Distal ends of radius and ulna along with the bones of the wrist and hand Image:Gray421.png, Transverse section across distal ends of radius and ulna.

References

External links

Dartmouth Anatomy
{{Authority control Upper limb anatomy Joints