176 



THE ARTICULATIONS OF THE UPPER LIMB. 



THE METACARPO-PHALANGEAL AND INTERPHALANGEAL ARTICULATIONS. 



The rounded head of each metacarpal bone is received into the slight hollow in 

 the base of the first phalanx, and the bones are maintained in position by two lateral 

 ligaments and an anterior ligament. 



The lateral ligaments are strong bands springing from the tubercle and 

 depression on each side of the head of the metacarpal bone, and passing down- 

 wards and forwards to the contiguous margin of the phalanx. The anterior fibres 

 are directed almost horizontally forwards and join the palmar ligament of the 

 articulation. 



The anterior or palmar ligament, or rather fibrous plate, occupies the 

 interval between the lateral ligaments on the palmar aspect of each joint ; it is a 



Fig. 203. SAGITTAL SECTION THROUGH THE LOWER PART OP THE RADIUS, 



LUNAR BONE, OS MAGNUM, METACARPAL BONE AND PHALANGES OP THE 

 MIDDLE FINGER, TO SHOW THE SHAPE OP THE ARTICULAR SURFACES 

 AND THE SYNOVIAL CAVITIES BETWEEN THESE SEVERAL BONES. (Allen 



Thomson.) 3 



1, synovial cavity of the wrist-joint ; 2, intercarpal cavity ; 3, carpo- 

 metacarpal cavity ; 4, metacarpo-phalangeal cavity ; 5 and 6, interphalangeal 

 cavities ; 4', 5', and 6', the palmar fibrous plates which are attached to the 

 bases of the several phalanges ; 7, indicates the place of the tendons of the 

 long flexor muscles ; 8, section of the anterior annular ligament ; 9, and 10, 

 transverse retinacula. or vaginal ligaments of the flexor tendons on the first 

 and second phalanges. 



thick and dense fibrous structure, which is firmly united to 

 the phalanx but loosely adherent to the metacarpal bone. It 

 is continuous at each side with the lateral ligament, so that 

 the three form one undivided structure which covers the joint, 

 except on the dorsal aspect. Its palmar surface is grooved for 

 the flexor tendon, the sheath of which is connected to it at 

 each side ; the other surface, looking to the interior of the 

 joint, is lined by synovial membrane, and supports the head 

 of the metacarpal bone. In the joint of the thumb there are 

 two sesamoid bones, one situated at each side, which are con- 

 nected with its ligaments. 



A synovial membrane is present in each joint, and 

 invests the surface of the ligaments which connect the 

 bones. 



The interphalangeal articulations differ from the foregoing only in the shape 

 of the articular surfaces (see p. 105). 



Movements of the -wrist and fingers. The movements taking- place at the wrist have 

 their seat partly in the radio-carpal, partly in the transverse carpal articulation. Flexion is 

 the freest movement, but a considerable degree of over-extension is also permitted. The hand 

 can also be moved laterally, and to a greater extent inwards (adduction or ulnar flexion) than 

 outwards (abduction or radial flexion). According to Henke and Langer both radio-carpal 

 and transverse carpal articulations are essentially hinge-joints, the axes of which are oblique 

 in opposite directions, that of the first joint extending from the styloid process of the radius 

 to the pisiform bone, and that of the transverse carpal joint from the tuberosity of the 

 scaphoid to the dorsum of the pyramidal bone. Flexion and extension are accordingly the 

 result of simultaneous movements in the two joints in the same direction, while abduction is 

 produced by flexion in the radio-carpal joint combined with extension in the transverse carpal 

 joint, and adduction by extension in the radio-carpal joint with flexion in the transverse 

 carpal joint. Side to side movement is permitted only to a very slight extent in the radio- 

 carpal joint. (Henke, "Handbuch der Anatomic und Mechanik der Gelenke," 1863 ; Langer, 

 " Lehrbuch der Anatomic.") 



