THE WRIST AND HAND 



1431 



at its attachment to the carpal ligament, spreads out fan-like below, and gives off four slips, 

 each of which bifurcates into two processes, which are attached to the sides of the first phalanx 

 of each finger and into the superficial transverse ligament of the web and the deeper one which 

 ties the heads of the metacarpal bones together. Transverse fibres pass between the processes 

 into which each of the four slips bifurcates, and thus form the beginning of the theca, which is 

 continued down the finger to the base of the last phalanx. It is the contraction of the palmar 

 aponeurosis, especiallj^ of the slip to the two medial fingers, which gives rise to Dupuytren's 

 contraction. The theca is strong opposite the first two phalanges (ligamentum vaginale), 

 weak and loose opposite the joints (ligamentum annulare). The density of this osseo-fibrous 

 tunnel and its close proximity to the digital nerves explain the pain in thecal inflammation. 

 Its tendency to gape widely after section is to be remembered in amputations through infected 

 parts. 



Synovial membranes. — Beneath the transverse carpal Hgament He two 

 synovial sacs, one for the flexor polHcis longus, and one for the superficial and 

 deep flexors of the fingers. Thej' extend above the transverse ligament for rather 

 more than 2.5 cm. (1 in.). The two sacs may communicate. A compound 

 palmar ganglion has an hour-glass outline, the transverse carpal ligament forming 

 the constriction. 



The creaking sensation in teno-synovitis and that of 'melon-seed' bodies often present in 

 tuberculosis here is well known. The sheath for the long flexor of the thumb reaches to the 

 base of the last phalanx. That for the finger-flexors gives off four processes. The one for the 

 little finger also reaches to the base of the last phalanx. Those for the index-, middle, and third 

 fingers end about the middle of the metacarpal bones. Traced from the insertions of the flexor 



Fig. 1150. — Section of Carpus through the Hamate Bone. (Two-thirds.) 



(Bellamy, after Henle.) 



Median nerve 

 Flexor pollicis longus Flexores sublimis and profundus 



Flexor carpi radialis 



Ulnar vessels and nerve 



Thenar muscles 

 Base of first metacarpal bone 



Abductor pollicis longus 



Greater multangular — \ 

 Extensor pollicis brevis- 

 Radial vessels 



Palmaris brevis 



Hypothenar muscles 



Extensor carpi radialis longus 



Lesser multangular 

 Extensor carpi radialis brevis 



Capita tum 



Extensor carpi ulnaris 



Extensor digiti quinti 

 Hamatum 

 Extensor digitorum communis 



Extensor indicis proprms 



profundus, the digital synovial sheaths extend upward into the palm as far as the bifiu-cation 

 of the palmar fascia (p. 1430), i. e., into a point about opposite to the necks of the metacarpal 

 bones, denoted on the surface by the crease which corresponds to the flexion of the fingers. 

 Thus, about 1 . 2 cm. (^in.) separates the sheaths of the lateral three fingers from the large syno- 

 vial sac beneath the transverse carpal ligament. There is no synovial sheath beneath the pulp 

 of the fingers or thumb, this part lying on the periosteum of the last phalanx. 



This has an important bearing on whitlow. Infection here may be merely subcuticular, 

 or deeper, in the latter case from the connection of the skin with the periosteum here existing 

 the bone is soon affected, and necrosis keeps up a tedious ulcer. As the two centres of the pha- 

 lanx do not unite till about the twentieth year, the distal one only requires removal; as the 

 flexor sheath only reaches to the insertion of the flexor, i. e., into the proximal, part of the bone, 

 both sheath and tendon ma^- '^f-qanp imr^'" -^ _,ion. Higher up along the fingers whitlow may be 

 cellulo-cutaneous or thecal. _ Whue the cf^XTinuity of the synovial sheath in the little finger and 

 thumb (fig. 1149) renders iilfCCtioif 'here more dangerous, the short gap between the digital 

 and the palmar sacs is readily traversed by acute infection, with all the grave results of 

 thecal suppuration. 



Suppuration in the hand owes much of its gravity to the possibility of infection of the syno- 

 vial tendon sheaths and consequent sloughing of the tendons. At the same time it is now 

 recognised that unless these sheaths are primarily infected pus collects at first in certain poten- 

 tial spaces, more or less well defined, in the looser connective tissue of the hand. One of these, 

 known as the middle palmar space (Kanavel*) is situated on the front of the metacarpals of 

 the middle and ring fingers, and lies deeply between the flexor tendons and the interosseous 

 muscles. Continuations of this potential space extend downward along the lumbrical muscles 



* Kanavel, A. B.: Infections of the Hand, 1912. 



