132 THE UPPER EXTREMITY 



When the whitlow occurs more distally, in the pulp of the finger, the vitality 

 of the distal part of the ungual phalanx is endangered, but the flexor 

 tendons may be regarded as being tolerably safe. When the inflammation 

 occurs more proximally, and involves the flexor sheath, as it generally does, 

 sloughing of the tendons is to be apprehended, unless an immediate 

 opening is made. And no slight superficial incision will suffice. The 

 knife must be carried deep into the centre of the finger, so as to freely 

 lay open the sheath containing the tendons. Early interference in cases 

 of whitlow of the thumb and little finger is even more urgently required 

 than in the case of the other three digits, because the digital mucous 

 sheaths of the former are, as a rule, offshoots from the great common 

 mucous sheath of the flexor tendons, and offer a ready means for the 

 proximal extension of the inflammatory action. 



Every amputation of the fingers above the insertion of the tendons of 

 the flexor profundus involves the opening of the flexor sheaths, and this, no 

 doubt, explains the occasional occurrence of palmar trouble after operations 

 of this kind. The open tubes offer a ready passage, by means of which 

 septic material may travel proximally into the palm, and, in the case of 

 the thumb and little finger, into the carpal tunnel and distal part of the 

 forearm. 



DORSUM AND LATERAL BORDER OF THE FOREARM. 



The cutaneous nerves and vessels in this region have 

 already been studied (p. 65). The parts which still require 

 to be examined are : 



1. The deep fascia. 



2. The supinator and extensor muscles. 



3. The dorsal interosseous artery. 



4. The perforating or terminal branch of the volar interosseous artery. 



5. The dorsal interosseous nerve. 



Deep Fascia. The deep fascia on the dorsal aspect of the 

 forearm is stronger than that which clothes its volar surface. 

 At the elbow it is firmly attached to the epicondyles of the 

 humerus and the olecranon, and it receives a reinforcement 

 of fibres from the tendon of the triceps muscle. There also it 

 affords origin to the extensor muscles, and sends strong septa 

 between them. At the wrist a thickened band dorsal carpal 

 ligament is developed in connection with it. This can 

 readily be distinguished from the thinner portions of the 

 fascia, with which it is continuous proximally and distally, 

 and it will be observed to stretch obliquely from the styloid 

 process of the radius medially and distally across the wrist 

 to the medial side of the carpus. 



Dissection. The deep fascia should now be removed, but that portion 

 of it near the elbow, which gives origin to the subjacent muscles, should 

 be left in place. The dorsal carpal ligament should also be artificially 

 separated and retained in situ. 



