510 



ABNORMAL CONDITIONS OF THE HAND. 



as well as the close manner in which the carpal 

 extremities of the metacarpal bones are im- 

 pacted together, render lateral motion impos- 

 sible ; in the fifth joint the forward or back- 

 ward motion is somewhat more extensive, but 

 this joint is equally limited with the others in 

 lateral movement. 



The carpo-metacarpal joint of the thumb 

 enjoys motion forwards, backwards, inwards, 

 and outwards, producing the movements of 

 flexion and extension, abduction and ad- 

 duction. The power of opposing the thumb 

 to any of the fingers is due to the oblique 

 direction of flexion in this joint : the bone 

 moves forwards and inwards, passing through 

 a line which would be concave inwards. This 

 is by far the most extensive motion of the 

 thumb, and it is by an excess of this motion 

 that the dislocation of the metacarpal bone 

 backwards is generally occasioned. Cru veil- 

 bier observes that the weakness of the posterior 

 ligament favours the occurrence of this lux- 

 ation. I cannot, however, admit the weakness 

 of this ligament ; on the contrary, it appears 

 to me to be the strongest of all the ligaments 

 of this joint ; which opinion, I find, is that of 

 the accurate Weitbrecht. 



The motion of adduction is, on the other 

 hand, the most limited, in consequence of the 

 proximity of the second metacarpal bone ; that 

 of abduction is very extensive, and when car- 

 ried too far may occasion luxation inwards. 



JOINTS OF THE FINGERS. 



1. Metacarpo-phalangeal joints. The first 

 phalanges are articulated by an oval concave 

 surface, with the rounded oblong heads of the 

 inferior extremities of the metacarpal bones : 

 it is remarkable that the long axis of the oval 

 concavity of the phalanx has a transverse di- 

 rection, while the long axis of the head of the 

 metacarpal bone is directed from before back- 

 wards, and consequently at right angles with 

 the former ; whence the great extent of lateral 

 motion enjoyed by these joints. 



Each of these joints is strengthened by two 

 lateral ligaments, of considerable strength, 

 inserted into the tubercle behind the depression 

 on each side of the head of the metacarpal 

 bone ; the point of insertion into the phalanx 

 is anterior to this, and consequently the direc- 

 tion of the lateral ligaments is downwards and 

 forwards; as they descend, these ligaments 

 spread out, and their anterior fibres become 

 identified with the anterior ligament. 



A third ligament, the anterior ligament, or 

 glenoid ligament of Cruveilhier, seems des- 

 tined more to increase the extent of the pha- 

 langeal articular concavity anteriorly, than to 

 maintain the integrity of the joint or limit its 

 motions. This ligament is, as Bichat expresses 

 it, a thick and dense fibrous bundle, in shape 

 half a ring, placed in front of the palmar sur- 

 face of the head of the metacarpal bone, com- 

 posed of transverse fibres which adhere in- 

 feriorly to the anterior edge of the concavity 

 on the phalanx, and on each side are identified 

 with the lateral ligaments and the transverse 

 ligaments by which the metacarpal bones are 

 connected. If the ligaments and synovial 



membrane of this joint be cut all round close 

 to their attachment to the head of the meta- 

 carpal bone, and that bone be removed, the 

 synovial capsule and ligaments remaining at- 

 tached to the phalanx, a very clear idea of the 

 relative positions of the ligaments may be 

 formed. The synovial membrane will then 

 appear protected on three sides by ligament ; 

 on the radial and ulnar side by the lateral 

 ligaments, and in front the anterior ligaments, 

 whilst posteriorly it is unprotected save by the 

 sheath of the extensor tendon. 



In the metacarpo-phalangeal articulation of 

 the thumb two sesarnoid bones, developed in 

 the substance of the anterior ligament, protect 

 the joint in front. 



2. Phalangcal joints. These joints are all 

 ginglymoid, the articular surfaces being pul- 

 ley-like ; they are provided with lateral liga- 

 ments similar to those of the metacarpo-pha- 

 langeal joints, and also with anterior ligaments 

 similarly disposed. 



Motions of the joints of the fingers. In 

 the phalangeal joints these motions are only 

 flexion and extension; the former are con- 

 siderably more extensive, and are favoured by 

 the inferior insertion of the lateral ligaments 

 being on a plane anterior to their superior 

 insertion. In addition to flexion and exten- 

 sion the metacarpo-phalangeal joints enjoy con- 

 siderable lateral motion, which is due to the 

 glenoid form of the phalangeal articular sur- 

 face, and to the enarthrodial form which the 

 joint derives from the extension of that arti- 

 cular surface by the anterior ligament. 



(R. B. Todd.) 



HAND,ABNORMAL CONDITIONS OF 

 THE. Deviations from the normal condition 

 of the different structures which enter into the 

 composition of the hand are very numerous, 

 and may be classed into those which are the 

 result of, first, accident; second, disease; 

 third, congenital malformation. 



I. ABNORMAL CONDITIONS, THE RESULT OF 

 ACCIDENT. 



Fractures and luxations. Simple frac- 

 tures of the bones of the hand are seldom 

 followed by any notable deformity ; but lux- 

 ations of these bones require from us some 

 attention here. 



Luxation of the bones of the carpus. The 

 bones of the carpus are united to each other so 

 solidly, and their movements seem so limited, 

 that, without experience, we should be dis- 

 posed to pronounce luxation of any of these 

 bones impossible ; nevertheless, the head of 

 the os magnum may be dislocated from the 

 cavity formed for it by the scaphoid and semi- 

 lunar bones. The first range of the bones of 

 the carpus is articulated with the bones of the 

 second range in such a manner that slight 

 gliding movements of flexion and extension of 

 the hand are permitted, which augment a little 

 the movements of flexion and extension of 

 the hand upon the forearm, and add some- 

 what, as Cruveilhier says, to the grace of the 

 movements of this portion of the upper ex- 



