The Wrist and Inferior Radio-Ulnar Joint

Question 1

Describe the articular surfaces of Scaphoid

Answer 1

• Prominent anterior tubercle
• Narrowed central waist

Articulates with radius proximally, lunate medially, with trapezium and trapezoid laterally and with capitate distally

Question 2

Describe the articular surfaces of lunate

Answer 2

smooth convex palmar surface

• square medial surface - articulates with triquetral
• crescent lateral surface - articulates with scaphoid
• distal concavity - articulates with capitate
• proximal convexity - articulates with radius and articular disc

Question 3

Describe the articular surfaces of triquetral

Answer 3

• lateral square surface - articulates with lunate

- circular medial surface - articulates with pisiform

Question 4

Describe the articular surfaces of pisiform

Answer 4

small round sesamoid bone in the flexor carpi ulnas tendon

• articulates with palmar surface of triquetral
• anterior surface projects distally and laterally - forms medial carpal tunnel

Question 5

Describe the articular surfaces of trapezium

Answer 5

irregular carpal bone

• tubercule and groove on medial anterior surface
• distally saddle shaped articular surface - for base of 1st metacarpal
• proximal articular surfaces for scaphoid and trapezoid

Question 6

Describe the articular surfaces of trapezoid

Answer 6

small and irregular bone

• articulates with 2nd metacarpal
• articulates with scaphoid, capitate and trapezium

Question 7

Describe the articular surfaces of capitate

Answer 7

largest carpal bone

• rounded head - articulates with concavities of hamate and scaphoid
• flat medial and lateral surfaces - articulate with hamate and trapezoid respectively
• flat dorsal surface
• roughened palmar surface
• distal articular surfaces for third metacarpal and narrow surface for 2nd and 4th metacarpals

Question 8

what is the structure of the interosseous membrane?

Answer 8

Strong fibrous sheet of fascia

• passes between interosseous borders of radius and ulna
• fibres pass obliquely downwards and medially

Question 9

what is the function of the interosseous membrane?

Answer 9

Transmission of forces from radius to ulna during WB of UL
- radius articulates with carpals receives forces - must be transmitted to ulna as radius has poor articulation with humerus

Minimises torsional stress on bones

Increases SA for attachment of muscles
- compartmentalises into anterior and posterior

Question 10

Classify the inferior radioulnar joint

Answer 10

synovial, complex, uniaxial pivot joint

Question 11

what is the nerve supply to the inferior radioulnar joint?

Answer 11

anterior and posterior interosseous nerves C7 and C8

Question 12

Describe the articular surfaces of the inferior radioulnar joint

Answer 12

• Convex, crescent shaped anterolateral head of ulna
• ulnar notch on medial lower end of radius - concave AP, slightly convex vertically
• lined in articular hyaline
• triangular fibrocartilagenous disc attaches to lateral side of root of ulnar styloid process by its apex
• also attaches to inferior edge of ulnar notch of radius by its base - uniting the two bones
• thicker peripherally than centrally.

Question 13

Describe the joint capsule of the inferior radioulnar joint

Answer 13

Relatively weak and loose

• formed by transverse bands of fibres
• attach to anterior and posterior margins of the ulnar notch of radius and the head of ulna
• inferior margins blend with edges of interarticular disc
• fibres remain separate superiorly

Question 14

Describe the synovial membrane in the inferior radioulnar joint

Answer 14

large in relation to the size of the joint

- extends upwards above margins of the JC - between radius and ulna - infront of interosseous membrane

Question 15

What are the stabilising factors of the inferior radioulnar joint?

Answer 15

intraairticular disc, interosseous membrane, pronator quadratus

Question 16

Describe the articular surfaces of the radoiocarpal joint

Answer 16

Distal surface of radius - ellipsoid surface - concave AP and transversely - shallower transversal, shorter AP
- covered in articular cartilage - divided by a low ridge - forms lateral triangular and medial quadrangular areas.

Distal intraairticular disc forms ellipsoid surface
- concave AP and transversely

Proximal carpal bone row

• continuous convex articular surface
• scaphoid, lunate and triquetral
• united by interosseous ligaments
• hyaline cartilage continuous across bone row

Question 17

Describe the joint capsule of the radoiocarpal joint

Answer 17

• Fibrous capsule
• Completely encloses the joint
• Attaches to :
  o the distal edges of radius and ulnar anteriorly and posteriorly
  o To the radial and ulnar styloid processes laterally and medially
  o Distally to the articular margins of the carpal bones
  o Medially passes to medial sides of triquetral
  o Laterally to lateral side of scaphoid
• Thickened and strengthened anteriorly and posteriorly
• Blends with the collateral carpal ligaments at the sides

Question 18

Describe the Synovial Membrane of the Radioulnar joint

Answer 18

• Lax synovial membrane
• Lines the joint capsule and attaches to all articular margins
• Has numerous folds- Particularly posteriorly

Question 19

Classify the radioulnar joint

Answer 19

synovial, complex, ellipsoid, biaxial joint

Question 20

state the nerve supply to the radioulnar joint

Answer 20

anterior interosseous ( median ) and posterior interosseous (radial) and ulna nerves (C7, C8)

Question 21

Classify the intercarpal joints

Answer 21

synovial plane joints

Question 22

what is the role of the inter carpal joints?

Answer 22

facilitate gliding movements to increase ROM at radiocarpal and midcarpal joints

Question 23

Classify the mid carpal joint

Answer 23

simple, multi axial, synovial, plane joint

Question 24

Describe the articular surface of the mid carpal joint

Answer 24

Divided into medial and lateral compartments

LATERAL

• rounded and convex distal pole of scaphoid proximally
• with concave surface formed by the plane surface of trapezium dn trapezoid

MEDIAL

• lunate and triquetrim are concave
• capitate and hamate are convex

OVERALL - proximal joint surface is concave, distal joint surface is convex

Question 25

Describe the joint capsule of the mid carpal joint

Answer 25

• Fibrous capsule
• Irregular bands of fibres
• Anteriorly and posteriorly the bands form the palmar and dorsal intercarpal ligaments
• Strengthened at the sides by collateral ligaments.

Question 26

Describe the synovial membrane of the mid carpal joint

Answer 26

• Lines the capsule and all non-articular parts

- Attaches to the margins of all joint surfaces

Question 27

what is the nerve supply of the mid carpal joint?

Answer 27

anterior and posterior interosseous and ulnar nerve (C7, 8)

Question 28

Describe the synovial membrane of the inter carpal joint?

Answer 28

lines the large and complex joint capsule between the carpal bones - does not communicate with the radiocapral, 1st carpometocarpal or priiform-triquetral joint spaces. Lines the non-articular joint surfaces, attaches to the margins of the bones.