13. radio ulnar joints

joints of upper extremity

1. Radio-ulnar joints Dr.K.Iyer Professor-Anatomy

2. Classification Synovial Uniaxial Pivot joint. There are 2 joints between radius & ulna. Superior & Middle

3. Superior R U joint Articulating surfaces— Medial surface of head of radius & Radial notch of ulna. Head of radius is held by annular ligament .

4. Annular ligament Annular ligament— It is attached to the margins of radial notch of ulna. It is NOT attached to radius. Its lower margin is narrower than the upper. So it holds the neck of radius. Superiorly,It is attached to lower border of elbow joint capsule & lateral collateral ligament.

5. Capsule Proximal border of annular ligament blends with elbow joint capsule. Posteriorly , it broadens, divides into 2-3 bands & are attached to posterior margin of radial notch. Inferiorly, it loosely holds the neck of radius.

6. Accessory ligaments Quadrate ligament— Extends from lower margin of ulnar notch to neck of radius. It closes the joint inferiorly.

7. Oblique cord Extends from ulnar to radial tuberosities. Fibers are at right angles to interosseous membrane fibers. Its functions are unknown.

8. Synovial membrane Annular ligament is lined by synovial membrane of elbow joint. It protrudes deep to annular ligament & reaches the neck of radius. A crescentic fold of the same also protrudes posteriorly between radius & ulna. The fibrous layer of the joint capsule encloses the joint and is continuous with that of the elbow joint. The synovial membrane lines the deep surface of the fibrous layer and non-articulating aspects of the bones. The synovial membrane is an inferior prolongation of the synovial membrane of the elbow joint.

9. Relations The external surface of the annular ligament blends with the radial collateral ligament . It provides an attachment for part of supinator. Posterior --anconeus and the interosseous recurrent artery. Internally the ligament is thinly covered by cartilage where it is in contact with the radial head.

10. Inferior R U Joint Synovial Uniaxial Pivot type Articulating surfaces— Lateral surface of head of ulna & ulnar notch of lower end of radius.

11. Inferior radioulnar joint

12. Articular disc-inf. R U joint Is triangular in shape. Is fibrocartilaginous. Is on the lower surface of head of ulna to radial notch. This is a very strong band holding the bones together. Its apex is attached to lateral depression of ulnar styloid process. Base is attached to radial notch & margins to carpal ligament.

13. Articular disc

14. Inferior radio ulnar joint Capsule: The capsule encloses the joint (articular surfaces) but is lax superiorly. It is thicker anteriorly & posteriorly. Ligaments: Weak anterior and posterior ligaments strengthen the capsule. Articular disc: This is triangular and composed of fibrocartilage. It shuts off the distal radioulnar joint from the wrist and strongly unites the radius to the ulna .

15. Inferior radio ulnar joint The synovial membrane extends superiorly between the radius and the ulna to form a recess of the distal radioulnar joint . This redundancy of the synovial capsule accommodates the twisting of the capsule that occurs when the distal end of the radius travels around the relatively fixed distal end of the ulna during pronation of the forearm. Ligaments of the Distal Radioulnar Joint Anterior and posterior ligaments strengthen the fibrous layer of the joint capsule of the distal radioulnar joint. These relatively weak transverse bands extend from the radius to the ulna across the anterior and posterior surfaces of the joint.

16. Inferior radio-ulnar joint A fibrocartilaginous articular disc called triangular ligament. It binds the ends of the ulna and radius together and is the main uniting structure of the joint . The proximal surface of this triangular disc articulates with the distal aspect of the head of the ulna. Hence, the joint cavity is L-shaped in a coronal section; the vertical bar of the L is between the radius and the ulna, and the horizontal bar is between the ulna and the articular disc . The articular disc separates the cavity of the distal radioulnar joint from the cavity of the wrist joint.

17. Relations

18. Nerve supply Superior radio-ulnar joint– median, ulnar musculo cutaneous, radial nerves. Inferior radio-ulnar joint—anterior & posterior inter-osseous nerves. Blood supply—superior joint gets branches from anastomosis around elbow joint.(radial & ulnar collateral arteries)

19. Movements Definition- Since it is an uniaxial joint, only rotation occurs. Is called pronation-supination. Pronation- hand rotating medially in such a manner that the palm comes to face posteriorly. supination is a reversal of this process so that the hand returns to the anatomic position and the palm faces anteriorly. The axis— passes through the head of the radius above and the attachment of the apex of the triangular articular disc below.

20. Pronation-supination Pronation and supination of the hand occur entirely in the forearm It involve rotation of the radius and movement of the distal end of the radius over the ulna . The superior articular surface of the radial head spins on the capitulum . At the same time, the articular surface on the side of the head slides against the radial notch of the ulna and areas of the joint capsule and annular ligament of radius. At the distal radio-ulnar joint, the ulnar notch of the radius slides anteriorly over the convex surface of the head of the ulna

21. Axis Axis of pronation & supination is not fixed. The axis normally stated is when forearm is resting on a surface & ulna is stationary & the forearm is supinated. ‘ In- space’ pronation is more important & is required for all movements of ‘working’ hand . This happens when ulnar movement is marked. . In ‘In- space’ pronation, conventional axis keeps shifting laterally till it passes between radius & ulna at both radioulnar joints. When prolonged through the digits, it passes through ring & middle finger

22. Pronation-supination Supination is a more powerful & anti- gravity movement. Used in tightening nuts, bolts & screws, closing taps, picking up objects for inspection & manipulation. After completion of movement, bones of forearm lie side by side, parallel to each other. Pronation is a primary positional movement. Is aided by gravity. At the end of the movement, radius lies on medial side of ulna with its dorsal surface on anterior aspect of forearm. Radius lies across the front of ulna. Head of radius spins on capitulum, & rotates in ulnar notch. Radial lower end swing around head of ulna. Head of Ulna itself moves posterolaterally in pronation & anteromedially in supination.

23. Pronation-supination It is a rotatory movement. Axis passes through the centre of the radial head to lateral surface of ulnar styloid process. it is 140-150 degrees With the elbow extended, it is 360 degrees due to humeral rotation & scapular movements.

24. Distal Radioulnar Joint Movements During pronation— the distal end of the radius moves (rotates) anteriorly and medially, crossing over the ulna anteriorly & comes to lie on medial side of ulna with its dorsal surface facing anteriorly. During supination— the radius uncrosses from the ulna, its distal end moving (rotating) laterally and posteriorly so the bones become parallel.

25. Inferior radio ulnar joint The inferior end of the radius moves around the relatively fixed end of the ulna during supination and pronation of the hand.

26. Movements During rotation, the radius moves around the ulnar head. Ulna moves laterally (abduction)

27. Ulnar movement In pronation, the head of the radius rotates within the annular ligament, The distal end of the radius with the hand moves bodily forward. The ulnar notch of the radius moving around the circumference of the head of the ulna In addition, the distal end of the ulna moves laterally so that the hand remains in line with the upper limb and is not displaced medially This movement of the ulna is important when using an instrument such as a screwdriver because it prevents side-to-side movement of the hand during the repetitive movements of hand.

28. Muscles- Proximal & distal Radioulnar Joint Supination is by the supinator and biceps brachii ( stronger in fast movements in flexion & in flexed elbow position .) Assisted by extensor carpi radialis longus Pronation is by the pronator quadratus (primarily) and pronator teres (secondarily), & against resistence. Assisted by The flexor carpi radialis, palmaris longus, and brachioradialis ( when the forearm is in the midpronated position).

29. Accessory movements These include anterior and posterior translation of the radial head on the ulnar radial notch, and of the ulnar head likewise on the radial ulnar notch. Accessory movements Body_ID: HC053070 Accessory movements include anterior and posterior translation of the radial head on the ulnar radial notch, and of the ulnar head likewise on the radial ulnar notch. Accessory movements Body_ID: HC053070 Accessory movements include anterior and posterior translation of the radial head on the ulnar radial notch, and of the ulnar head likewise on the radial ulnar notch.

30. Interosseous membrane Inter-osseous borders of radius & ulna face each other & give attachment to inter-osseous membrane. Fibers pass obliquely downwards from radius to ulna. They transmit forces from wrist joint to radius to ulna & then to elbow joint. It holds the 2 bones together yet separate. It restricts the movements to a certain extent. Gives attachment to muscles. Is taut in midprone position

31. Integrity of the joints The integrity and functions of the humeroradial joint proximal radioulnar joint complex ,depends primarily on the combined radial collateral and anular ligaments. The combined synovial proximal and distal radioulnar joints plus the interosseous membrane enable pronation and supination of the forearm. The anular ligament of the proximal joint, articular disc of the distal joint, and interosseous membrane not only hold the two bones together while permitting the necessary motion between them, but they (especially the membrane) also transmit forces received from the hand by the radius to the ulna for subsequent transmission to the humerus and pectoral girdle.

32. Working position of hand In mid prone position the wrist joint can be abducted & adducted to manipulate instruments. Supination is used in tightening screws.

33. Dislocation of radius

34. Dislocation of Radial Head Preschool children, particularly girls, are vulnerable to incomplete temporary dislocation of the head of the radius (also called nursemaid's elbow and pulled elbow). The history of these cases is typical. The child is suddenly lifted (jerked) by the upper limb while the forearm is pronated (e.g., lifting a child into a bus) The child may cry out, refuse to use the limb, protects the limb by holding it with the elbow flexed and the forearm pronated. The sudden pulling of the upper limb tears the distal attachment of the annular ligament, where it is loosely attached to the neck of the radius. The radial head then moves distally, partially out of the anular ligament. The proximal part of the torn ligament may become trapped between the head of the radius and the capitulum of the humerus. The source of pain is the pinched anular ligament. Treatment of the subluxation consists of supination of the child's forearm while the elbow is flexed . The tear in the anular ligament soon heals when the limb is placed in a sling for 2 weeks .

35. Radioulnar Joint Disease 1. Infection of the elbow joint invariably involves the proximal radioulnar joint as these two joint communicate with each other. 2. The strength of the proximal radioulnar joint depends on the integrity of the strong annular ligament. 3. Rupture of this ligament occurs in cases of anterior dislocation of the head of the radius on the capitulum of the humerus. 4. In young children, in whom the head of the radius is still small and undeveloped, a sudden jerk on the arm can pull the radial head down through the annular ligament.

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