PRACTICAL CONSIDERATIONS : THE FOOT-JOINTS. 453 



accidental compression of the branches of the external plantar nerve. R. Jones 

 thinks that it is often a communicating branch between the fourth division of the 

 internal plantar and the external plantar that is compressed between the bone and the 

 ground as it passes beneath the head of the fourth metatarsal. A transverse section 

 of the foot through the heads of the metatarsals shows that the first and fourth bear 

 the most pressure (Fig. 467). The situation of the plantar digital nerves, superficial 

 to and not between the bones, and the collapse of the transverse arch in most cases of 

 metatarsalgia, broadening the intervals between the bones, but increasing pressure on 

 the structures beneath them, support the latter view. 



Flat-foot is so closely associated in its anatomical deformities with talipes valg*us 

 that it will be considered in relation with the latter, which, with the other \arieties of 

 club-foot, can best be understood after the muscles and fasciae of the leg and foot 

 have been described. 



Disease of the tarsal joints, like that of the bones, is most frequently tuberculous 

 in character, and is more apt to remain localized when it is situated in the posterior 

 pillar of the main arch, — i.e., in the posterior half of the calcaneo-astragaloid joint. 

 If in front of the interosseous ligament dividing that articulation, or if in either of the 

 mid-tarsal joints (with which it communicates), or in any of the remaining four 

 synovial cavities, it is apt to extend much beyond its original limits. The circum- 

 stances that favor the origin (page 437) and influence unfavorably the course of bone 

 disease in this region apply in the main to disease of the joints. In whichever tissue 

 — bony or synovial — it originates, it is apt to spread to the other. The astragalo- 

 scaphoid joint, on account of its superficial position and its range of motion (which is 

 greater than that of any of the joints below the ankle), is most apt to be affected. 

 The situation of the swelling and tenderness will usually differentiate it from ankle- 

 joint disease (page 451 ). Probably on account of the diffuse infection of the abundant 

 cancellous tissue of the tarsal bones (either primary or secondary to joint disease), 

 remote tuberculous infection — phthisis — follows or accompanies disease of the ankle 

 and tarsus more frequently than it does disease of any other part except possibly the 

 wrist (Cheyne). 



Gout affects peculiarly the metatarso-phalangeal joint of the great toe. In 516 

 cases of gout, 341 were of one or both of the great toes alone and 373 of the great 

 toe with some other part (Scudamore). This is due to (a) the abundance in that 

 region of dense fibrous tissue of little vascularity ; {b~) its remoteness from the heart, 

 the force of the circulation being at its minimum ; (r) the large share of the body 

 weight which it sustains, as the anterior extremity of the main arch of the foot ; (^) 

 the frequency of traumatism ; (<?) the constant exposure to cold and damp ; (/) its 

 dependent position. 



LandmarkSc — The ankle-joint (g.v.) lies about half an inch above the tip of 

 the inner malleolus. Syme's amputation is done through this joint, the incision 

 being made from the tip of one malleolus to the tip of the other, and at right angles 

 to the long axis of the foot. 



The mid-tarsal joint (through which Chopart's amputation is done) runs out- 

 ward from a point just back of the scaphoid tuberosity, and passes directly over the 

 dorsum of the foot to a point a little in advance of the middle of a line between the 

 tip of the external malleolus and the tuberosity of the fifth metatarsal. 



The tarso-metatarsal joint begins at a point about one and a half inches in front 

 of the tubercle of the scaphoid, — i.e., just back of the base of the first metatarsal, — 

 passes at first directly outward, then passes irregularly around the three sides of the 

 mortise between the internal and external cuneiforms in which the base of the second 

 metatarsal rests, and then slopes slightly backward to its easily recognized termination 

 on the outer side of the foot, just behind the base of the fifth metatarsal. 



Hey's amputation begins and ends at the two extremities of this joint-line, but 

 the projection of the internal cuneiform is sawn across. In Lisfranc's amputation the 

 joint-line is followed throughout. The metatarso-phalangeal joints lie an inch behind 

 the interdigital web. 



