THE FOOT. 



575 



Tarsometatarsal (Lisfranc's) Amputation. The guide to this joint is 

 the tuberosity of the fifth metatarsal bone on the outer side and the ridge on the base 

 of the first metatarsal on the inner side. This latter is about 4 cm. (i^ in. ) in front 

 of the highest point of the tubercle of the scaphoid. 



The joint is best entered from the outer side. The knife is to be passed first 

 forward and then carried inward. Trouble is usually experienced when the base of 

 the second metatarsal is to be disarticulated. It lies behind the others and some 

 surgeons advise skipping it and opening the first metatarsal joint and then com- 

 pleting the disarticulation by opening the second last. The sawing off of the pro- 

 jecting internal cuneiform bone as proposed by Hey is objected to on account of 

 weakening the attachment of the tibialis anterior tendon. The same precaution is 

 to be taken of making the plantar flap longer on its inner side, as was advised in 

 Chopart's amputation, on account of the greater depth of the foot on this side. The 

 line of the joint is best understood by reference to the position of the bones (Fig. 

 578). Tenotomy of the tendo calcaneus (Achillis) is not so often resorted to in this 

 amputation as in that through the midtarsal joint (Fig. 593). 



PLANTAR ABSCESS. 



Abscesses of the sole of the foot are usually caused by infected punctured 

 wounds, or by the extension of infection from wounds of the toes, etc. 



The plantar fascia lies on the flexor brevis digitorum while the long flexor 

 tendons lie beneath it. A punctured 

 wound may perforate the plantar fascia 

 and penetrate the flexor brevis which 

 arises from its under surface, yet if this 

 muscle is not entirely traversed by the 

 wound the tendons of the long flexors 

 beneath escape infection and the pus 

 accumulates beneath the plantar fascia. 



Superficial Plantar Abscess. 

 In the superficial form of plantar abscess 

 the pus tends to point in four directions: 

 (i) it may come directly up through gaps 

 between the fibres of the plantar fascia 

 and make an hour-glass abscess, a small 

 amount of pus being above the plantar 

 fascia, between it and the skin, while a 

 larger collection is beneath the fascia in 

 the substance of the muscle; (2) it may 

 burrow its way forward showing between 

 the tendons in the direction of the webs 

 of the toes; (3) it may appear in the 

 groove on the outer side of the foot be- 

 tween the flexor brevis and abductor 

 minimi digiti; (4) it may appear on the 

 inner side of the foot between the abduc- 

 tor hallucis and flexor brevis (Fig. 594). 



Deep Plantar Abscess. In deep 

 infection the pus accumulates around the 

 deep flexor tendons and beneath the 

 flexor brevis muscle. Its greatest ten- 

 dency is to extend up the leg by following 

 the flexor tendons behind the internal malleolus. It may also show itself in the grooves 

 on either side of the flexor brevis, or between the tendons at the webs of the toes. 



Incision of Plantar Abscess. The safest way to open these abscesses is 

 by the method of Hilton. The skin is first incised and the abscess opened by insert- 

 ing a pointed haemostatic forceps and opening its blades, or using some similar blunt 

 instrument. This is done to avoid wounding the arteries. If necessary the whole 



Following the flexor 

 tendons up behind the 

 internal malleolus 



Between the flexor 



brevis and abductor 



hallucis 



Between flexor brevis 



and abductor minimi 



digiti 



Coming through gaps 

 in the fascia 



Anteriorly between 

 the tendons at the 

 webs of the toes 



FIG. 594.- Diagram showing the points of exit of suppu- 

 ration beneath the plantar fascia. 



