Distal Radio-Ulnar Joint

Palmer A.K. and Werner F.W. 1984. Biomechanics of the distal radio-ulnar joint. Clin. Orthop. 187 26. 

The distal radio-ulnar joint articulates the rounded head of the ulna with the ulnar notch of the distal... 

Fig. 10.1. Schematic drawing of a coronal view through the wrist outlines the relation among carpal bones and wrist joint spaces. Distal to the radius (R) and ulna fLl),the proximal row of carpal bones includes the scaphoid (S), lunate (L), triquetrum (T) and pisiform (P), whereas the distal row is formed by the trapezium fTzj, trapezoid (Tdj, capitate (C) and hamate (H). The distal radio-ulnar joint (1) is separated from the radiocarpal joint (2) by the triangular fibrocartilage (curved arrow). The scapholunate (straight arrow) and lunotriquetral (arrowhead) ligaments separate the radiocarpal from the mid-carpal fSj joint. The carpometacarpal joint spaces (4) lie ahead of the distal carpal row...

Fig.l0.19a,b. Extensor tendons fifth compartment, a Transverse 15-7 MHz US image obtained at the distal radio-ulnar joint level reveals the extensor digiti quinti (arrow) tendon located medial to the extensor digitorum (EDQ. Observe the lack of an osseous support for the tunnel of the fifth compartment, which is elevated from the bony surface of the radius and ulna. At the distal radio-ulnar joint level, the ulnar head is covered by articular cartilage (rhombi). b Probe positioning and field-of-view of the US image relative to the dorsal wrist structures... 

Fig. 10.66a,b. Distal radio-ulnar joint synovitis, a Distal and b proximal transverse 12-5 MHz US images obtained over the dorsal aspect of the distal radio-ulnar joint at the levels horizontal black bars) indicated in the diagram on the left show the proximal recess distended by fluid (arrows). No effusion is seen at the level of the articular cartilages. The inserts at the upper right sides of the figure indicate probe positioning... 

Fig. 10.71. Caput ulnae syndrome in rheumatoid arthritis. Schematic drawing of a transverse view through the distal radioulnar joint outlines the rupture of the triangular fibrocartilage (arrowheads) and marginal erosions at the distal radio-ulnar joint level due to intra-articular pannus (asterisks). As a result, the ulna subluxes dorsally (gray arrow). Pannus (star) inside the extensor carpi ulnaris tendon (open arrow) sheath leads to cortical erosions, tear of the retinaculum and tendon thinning and splitting. St, styloid of the ulna Rad, radius...

Fig. 10.72a,b. Caput ulnae syndrome in rheumatoid arthritis, a Longitudinal and b transverse 12-5 MHz US images over the extensor carpi ulnaris tendon (straight arrows) reveal synovial pannus inside the distal radio-ulnar joint (asterisk) and the extensor carpi ulnaris tendon sheath (arrowheads). The tendon is dislocated (curved arrow) out of its ulnar groove due to the tear of the retinaculum. See Fig. 10.20b for comparison with normal findings... 

Figure 25. Cross section of the forearm through distal end of the proximal radio-ulnar joint.

The bone structures about the elbow joint include the proximal ends of the ulna and radius and the distal end of the humerus (Fig. 8.1). The radial head articulates with the humeral capitellum in a pivotal mode and the ulna with the humeral trochlea in a hinge mode. The proximal radio-ulnar articulation is composed of the radial head which revolves within the sigmoid (radial) notch of the ulna allowing pronation-supination movements. These articulations cooperate during complex joint movements allowing a wide degree of flexion, extension and axial... 

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