THE HAND. 



369 



Metacarpophalangeal Amputation. Lateral flaps are usually used. They 

 are often made too short because the joint is thought to be higher than it really is. 

 By flexing the thumb to a right angle the joint can be felt on the dorsum about 

 8 mm. ( YZ in. ) below the top of the knuckle. The flaps must be cut as far forward as 

 the middle of the phalanx. The two digital arteries on the palmar surface will 

 require torsion or ligation. If the base of the phalanx can be retained the attach- 

 ments of the short muscles of the thumb are preserved and additional control is given 

 to the stump. 



Carpometacarpal Amputation. The upper limit of the metacarpal bone 

 may often be difficult to recognize. The best way to locate it is to feel for the snuff- 

 box and then feel for the joint a centi- 

 metre (say a half inch) in front Of it. The ^x Extensor communis digitorum 



dorsalis pollicis artery running on the dor- 

 sum of the bone and the princeps pollicis 



on its palmar aspect may require ligation. /t^^^JjS^ F ' ex r sublimis di ^ itorum 

 In disarticulating, it should be remembered If^^^^j^U- Digital artery 

 that the joint is curved with its convexity 

 toward the wrist. 



Digital nerve 



AMPUTATIONS OF THE FINGERS. 



Flexor profundus digitorum 



FIG. 383. A transverse section of the proximal 

 phalanx. 



In amputating the fingers, although it 

 is easier to amputate through the joints, 

 it is better to cut through the bone and save part of the phalanx, because much 

 better control over the movements is obtained on account of the insertion of the 

 tendons into the base and sides of the phalanges. Into the base of the distal 

 phalanx is inserted the common extensor and flexor profundus digitorum. Into the 

 base of the middle phalanx on its dorsal surface is inserted the extensor communis 

 digitorum, which is reinforced by the lumbricales and interossei ; on its palmar 

 surface is inserted the flexor sublimis digitorum. Into the bases of the proximal 



FIG. 384. Lines of incision for amputations at the Carpometacarpal joint of the thumb, the metacarpophalangea! 

 joint of the index finger and between the proximal and middle phalanges of the middle finger. 



phalanges are inserted the interossei muscles. The lines of the joints are to be recog- 

 nized by remembering that the distal phalanx always flexes beneath the proximal 

 one, therefore the prominence is always formed by the head of the proximal bone. 



The joint is to be opened by an incision across its anterior surface when flexed, 

 and not on its dorsal surface. Anterior or palmar flaps are always used, except 

 at the metacarpal joints. The digital arteries lie on the lateral palmar surface on 

 each side of the flexor tendons and may require torsion or ligation. The finger- 

 joints have lateral ligaments and a palmar or glenoid ligament. On the dorsal 

 surface there is no ligament, its place being filled by the extensor tendon (Fig. 383). 



Metacarpophalangeal Amputations. Lateral flaps are used in disarticu- 

 lating at the metacarpal joints. In a well-developed hand the line of the joint will 

 be 1.25 cm. (^2 in.) below the dorsal surface of the metacarpal bone (Fig. 384). 



In consequence of not first recognizing the position of the joint the flaps are 

 often cut too short. The incision must not involve the webs of the fingers but 

 should reach as far forward as the middle of the phalanx. If this is not done it will 

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