330 SYNDESMOLOGY 



Movements. The articulation of the hand and wrist considered as a whole involves four 

 articular surfaces: (a) the inferior surfaces of the radius and articular disk; (b) the superior 

 surfaces of the navicular, lunate, and triangular, the pisiform having no essential part in the 

 movement of the hand; (c) the S-shaped surface formed by the inferior surfaces of the navicular, 

 lunate, and triangular; (d) the reciprocal surface formed by the upper surfaces of the bones of 

 the second row. These four surfaces form two joints: (1) a proximal, the wrist-joint proper; 

 and (2) a distal, the mid-carpal joint. 



1. The wrist-joint proper is a true condyloid articulation, and therefore all movements but 

 rotation are permitted. Flexion and extension are the most free, and of these a greater amount 

 of extension than of flexion is permitted, since the articulating surfaces extend farther on the dorsal 

 than on the volar surfaces of the carpal bones. In this movement the carpal bones rotate on a 

 transverse axis drawn between the tips of the styloid processes of the radius and ulna. A certain 

 amount of adduction (or ulnar flexion) and abduction (or radial flexion) is also permitted. The 

 former is considerably greater in extent than the latter on account of the shortness of the styloid 

 process of the ulna, abduction being soon limited by the contact of the styloid process of the 

 radius with the greater multangular. In this movement the carpus revolves upon an antero- 

 posterior axis drawn through the center of the wrist. 1 Finally, circumduction is permitted by 

 the combined and consecutive movements of adduction, extension, abduction, and flexion. No 

 rotation is possible, but the effect of rotation is obtained by the pronation and supination of the 

 radius on the ulna. The movement of flexion is performed by the Flexor carpi radialis, the Flexor 

 carpi ulnaris, and the Palmaris longus; extension by the Extensores carpi radiales longus and 

 brevis and the Extensor carpi ulnaris; adduction (ulnar flexion) by the Flexor carpi ulnaris and 

 the Extensor carpi ulnaris; and abduction (radial flexion) by the Abductor pollicis longus, the 

 Extensors of the thumb, and the Extensores carpi radiales longus and brevis and the Flexor carpi 

 radialis. When the fingers are extended, flexion of the wrist is performed by the Flexores carpi 

 radialis and ulnaris and extension is aided by the Extensor digitorum communis. When the 

 fingers are flexed, flexion of the wrist is aided by the Flexores digitorum sublimis and profundus, 

 and extension is performed by the Extensores carpi radiales and ulnaris. 



2. The chief movements permitted in the mid-carpal joint are flexion and extension and a 

 slight amount of rotation. In flexion and extension, which are the movements most freely enjoyed, 

 the greater and lesser multangulars oh the radial side and the hamate on the ulnar side glide 

 forward and backward on the navicular and triangular respectively, while the head of the capitate 

 and the superior surface of the hamate rotate in the cup-shaped cavity of the navicular and 

 lunate. Flexion at this joint is freer than extension. A very trifling amount of rotation is also 

 permitted, the head of the capitate rotating around a vertical axis drawn through its own center, 

 while at the same time a slight gliding movement takes place in the lateral and medial portions 

 of the joint. 



VIII. Carpometacarpal Articulations (Articulationes Carpometacarpeae). 



Carpometacarpal Articulation of the Thumb (articulatio carpometacarpea pollicis}. 

 This is a joint of reciprocal reception between the first metacarpal and the 

 greater multangular; it enjoys great freedom of movement on account of the 

 configuration of its articular surfaces, which are saddle-shaped. The joint is sur- 

 rounded by a capsule, which is thick but loose, and passes from the circumference 

 of the base of the metacarpal bone to the rough edge bounding the articular surface 

 of the greater multangular; it is thickest laterally and dorsally, and is lined by 

 synovial membrane. 



Movements. In this articulation the movements permitted are flexion and extension in the 

 plane of the palm of the hand, abduction and adduction in a plane at right angles to the palm, 

 circumduction, and opposition. It is by the movement of opposition that the tip of the thumb 

 is brought into contact with the volar surfaces of the slightly flexed fingers. This movement is 

 effected through the medium of a small sloping facet on the anterior lip of the saddle-shaped 

 articular surface of the greater multangular. The Flexor muscles pull the corresponding part 

 of the articular surface of the metacarpal bone on to this facet, and the movement of opposition 

 is then carried out by the Adductors. 



Flexion of this joint is produced by the Flexores pollicis longus and brevis, assisted by the 

 Opponens pollicis and the Adductor pollicis. Extension is effected mainly by the abductor 

 pollicis longus, assisted by the Extensores pollicis longus and brevis. Adduction is carried out 

 by the Adductor; abduction mainly by the Abductores pollicis longus and brevis, assisted by the 

 Extensors. 



1 H. M. Johnston (Journal of Anatomy and Physiology, vol. xli) maintains that n ulnar and radial flexion only 

 slight lateral movement occurs at the radiocarpal joint, and that in complete flexion and extension of the hand there 

 is a small degree of ulnar flexion at the radiocarpal joint. 



