THE FOOT 



1465 



side, to one just above the sustentaculum tali. In Syme's amputation through the ankle-joint, 

 the incision starts from the tip of the lateral malleolus, and is then carried, pointing a little back- 

 ward toward the heel, across the sole to a point 1.2 cm. (| in.) below the medial malleolus. 

 The chief supply to the heel-flap is from the medial calcaneal. Care should be taken to divide 

 the posterior tibial below its bifurcation and not to prick this vessel afterward. 



In PirogoflE's amputation the incision begins and ends at the same points, but is carried 

 straight across the sole. In each amputation the extremities of the above incision are joined 

 by one going directly across the ankle-joint, which lies about 1.2 cm. (2 in.) above the tip of the 

 internal malleolus. 



In Chopart's medio-tarsal amputation, which passes between the talus and the navicular 

 on the medial side, and the calcaneus and the cuboid on the lateral, the line of the joints to be 

 opened would be one drawn across the dorsum from a point just behind the tuberosity of the 

 navicular to a point corresponding to the calcaneo-cuboid joint, just midway between the tip 

 of the lateral malleolus and the base of the fifth metatarsal bone. The convexity of the plantar 

 flap should reach to a point 2.5 cm. (1 in.) behind the heads of the metatarsal bones. Owing 

 to the tendency of the unbalanced action of the calf muscles to tilt up the calcaneus and thus 

 throw the scar down into the line of pressure, the powerful tibialis anterior tendon and those of 

 the extensors should be carefully stitched into the tissues of the sole flap. 



In Lisfranc's, or Hay's, or the tarso -metatarsal amputation, the bases of the fifth and first 

 metatarsals must be defined. The first of these can always be detected, even in a stout or 

 swollen foot; on the medial side the joint between the first cuneiform and the first metatarsal 



Fig. 1179. — Vertical Section through the Cuneiform and Cuboid Bones. 

 Dorsalis pedis vessels and nerve 

 Extensor hallucis longus 

 First cuneiform 



(One-half.) 



Second cuneiform 



Tibialis anterior 



Third cuneiform 



Extensor digitonim brevis 

 Dorsal aponeiuosis 

 1 Cuboid 

 I Peroneus tertius 



Abductor hallucus 

 Medial plantar vessels and nerve 

 Abductor hallucis 



Flexor hallucis longus 

 Plantar fascia 

 Flexor digitorum longus 



Abductor digiti quinti 



Lateral plantar vessels and nerve 

 Tendon of peroneus longus 



Flexor digitorum brevis 



bone lies 3.7 cm. (I5 in.) in front of the navicular tuberosity. In opening the joint between the 

 second metatarsal and the middle cuneiform, its position (the base of the former bone projecting 

 upward on to a level 6 or 8 mm. (j or ^ in.) above the others), and the way in which it is locked 

 in between its fellows and the cuneiform bones, must be remembered. The convexity of the 

 plantar flap here reaches the heads of the metatarsal bones. 



In marking out the flaps for the amputation of the great toe, the large size of the head'of 

 the first metatarsal, and the importance of leaving this so as not to diminish its supporting 

 power and the treading width of the foot, and thus of marking out flaps sufficiently long and 

 large, must be borne in mind. The dorsal incision should begin 3.7 cm. (1^ in.) above the web. 

 The line of the joint is a little distal to the centre of the ball of the toe (fig. 1181). The sesa- 

 moid bones should be left, so as not to endanger the vitahty of the flaps. In amputation of 

 the other toes, the fine of their metatarso-phalangeal joints Hes a full inch above the web. 



Bursas and synovial membranes. — The synovial sheath of the extensor hal- 

 lucis longus extends from the front of the ankle, over the instep, as far as the meta- 

 tarsal bone of the great toe. There is generally a bursa over the instep, above, or 

 it may be below, the tendon. 



There is often an irregular bursa between the tendons of the extensor digitorum longus 

 and the projecting end of the talus over which the tendons play. There is much friction here. 

 It is well to be aware that this bursa sometimes communicates with the joint of the head of the 

 talus. (Holden.) There is a deep synovial bursa between the tendo Achillis and the cal- 

 caneus. Numerous other bursse may appear over any of the bony points in the foot, especially 

 when they are rendered over-prominent by morbid conditions. 



Synovial membranes. — In addition to that of the ankle-joint, there are six 

 synovial membranes in the tarsus, viz.: — (1) Talo-calcaneal, peculiar to these 



