PRACTICAL CONSIDERATIONS : WRIST AND HAND. 



617 



Head of 

 metacarpal bone 



Abductor poll. 



Flexor 

 brevispoU. 



Tendon of flex, longus poll. 



Adductor poll., obi. portion 



Dissection of metacarpo-phalangeal dislocation of thumb. 



by vessels which penetrate the sheath to supply the tendons. Over the last phalanx 

 the fibro-fatty subcutaneous layer — the ' ' pulp' ' of the finger — lies directly upon the 

 periosteum. 



Infection of the dorsum of a finger often originates near or about the root of a nail 

 (onychia) and may involve the matrix of the latter. It is not under much pressure, 

 and is therefore not usually 



serious, although through the Fig. 593. 



veins and lymphatics it may 

 exceptionally extend rapidly 

 up the arm. 



Infection of the palmar 

 surface of a finger ( panaritium, 

 paronychia, whitlow, felon ) is 

 of two chief varieties : (a) 

 subcutaneous, in \\-hich the 

 symptoms are at first limited 

 to the seat of infection and are 

 superficial, although, as it is a 

 true cellulitis, they may ex- 

 tend to the dorsum or towards 

 the palm ; and (b) thecal, with 

 more severe pain, greater lim- 

 itation of flexion, and more 

 rapid extension upward. 



If the felon involves the 

 distal portion of the finger, the close relation of the ' ' pulp' ' and the periosteum ol 

 the last phalanx makes necrosis of that bone frequent, although its upper part usually 

 escapes because {a) it is an epiphysis ; {b) the insertion of the tendon of the deep 

 flexor probably keeps up its blood-supply (Treves). 



The absence of the tendon-sheath over the body and tip of the last phalanx pre- 

 vents the conversion of the subcutaneous into the thecal variety, unless the infection 

 extends upward as far as the base of the phalanx. 



Elsewhere the thecal variety often results from extension from a subcutaneous 

 focus by the vertical connective-tissue fibres and the vessels already mentioned. The 

 interphalangeal joints are often affected because it is opposite them that {a) the 



tendon-sheaths are thinnest and 

 Fig. 594. {b) the vessels enter. In infection 



of the tendon-sheaths of the index, 

 middle, and ring fingers the upward 

 extension is arrested, at least for 

 a time, about opposite the necks 

 of the metacarpal bones. If the 

 thumb or little finger is involved, 

 the infection is likely to spread to 

 a higher level (page 615).  



The so-called * ' subcuticular' ' 

 felon is a superficial pustule, while 

 the ' ' subperiosteal' ' felon may 

 either result from extension of the 

 foregoing varieties or may be origi- 

 nally an infective osteo-periostitis 

 or osteo-myelitis. 



In relation to amputation of 

 the finger it may be noted that the 

 insertion of the flexor sublimis tendon into the sides of the second phalanx renders 

 amputation at the metacarpo-phalangeal joint often more satisfactory in its results 

 than one done through the first phalanx or first interphalangeal joint. 



Dislocation of the first phalanx of the thumb upon the dorsum of its metacarpal 

 bone requires special mention on account of the difficulty of reduction. It has been 



/ 



Dissection showing position of bones in dislocation of thumVi. 



