5.3- Upper limb (bones & joints)

Joints of the Hand

8 carpal bones and 5 metacarpal bones Intercarpal joints between the bones of each row (proximal and distal row of 4) The mid carpal joint between the proximal and distal rows of carpal bones The carpometacarpal joints include the saddle type and plane type synovial joints.

What structure unites the shaft of the radius to that of the ulna and how does it function?

Interosseous membrane; located between the proximal and distal radioulnar joints. The interosseous membrane is attached between the medial surface of the shaft of the radius and the interosseous border of the ulna. It binds the radius to the ulna, ensuring they remain a fixed distance apart. Tension changes occur in the interosseous membrane during movements of the forearm. It relaxes allowing the radius to rotate across the ulna (in pronation) and tightens as the limb returns to the anatomical position (in supination). Fibres of the interosseous membrane run obliquely downwards from the radius to the ulna and are capable of transferring force between the two bones of the forearm (weight bearing on the pre-axial bone is transferred to the post-axial bone).

Joints of the Fingers

Metacarpophalangeal joints include hinge joints (flexesion/extension) and condyloid. Interphalangeal joints

Proximal Radioulna Joint

Pivot type synovial joint between the head of the radius articulates with the radial notch of the ulna. The radial head is held in place by the anular ligament of the radius. The fibrous layer of the joint capsule encloses the joint and is continuous with that of the elbow joint. Movements: pronation and supination (ulna stays relatively immobile whilst the radius rotates/pivots around it)

Wrist Joint

Radiocarpal joint A condyloid type synovial joint (biaxial: flexion/extension and abduction/adduction) Between the distal radius and carpal bones (scaphoid and lunate) An articular disc is present on the ulnar side (separates ulnar from carpal bone)

What structure is primarily responsible got stability go the proximal radioulnar joint?

The annular ligament, attaching to the radial notch of the ulna with its fibres encircling the head and neck of the radius, is also an articular surface. It is lined by cartilage directed to it from the radial notch of the ulna. The annular ligament has no direct attachment to the radius, allowing the radial head to rotate freely within the ligament. The annular ligament is cone-shaped, with the tightest part of the cone encircling the radial head.

What movements of the radius and ulna occur at the radioulnar joints?

The radius rotates within the confines of the annular ligament and radial notch during pronation and supination. In pronation the radius swings across the ulna, and returns to its normal position in supination. Simultaneously, the head of the radius spins on the capitulum of the humerus during both pronation and supination.

Wrist Fracture

distal radius (Colles fracture) pushed up

Distal Radio-ulna Joint

pivot type of synovial joint. The radius moves around the relatively fixed distal end of the ulna.

Elbow Joint

uni-axial synovial hinge joint. It is also a compound joint (with more than one set of articulations) The spool-shaped trochlea and spheroidal capitulum of the humerus articulate with the trochlear notch of the ulna and the slightly concave superior aspect of the head of radius, respectively; therefore, there are humero-ulnar and humero- radial articulations. The collateral ligaments of the elbow joint are strong triangular bands that reinforce the capsule