Part 13

118. =Tendons behind inner ankle.=--Above and behind the malleolus internus we can feel the broad flat tendon of the tibialis posticus and upon it that of the flexor longus digitorum. The tendon of the tibialis posticus lies nearest to the bone and comes well up in relief in adduction of the foot. It lies close to, and parallel with, the inner edge of the tibia, so that this edge is the best guide to it. Therefore in tenotomy the knife should be introduced first perpendicularly between the tendon and the bone, and then turned at right angles to cut the tendon. The tendon has a separate sheath and synovial membrane, which commences about one inch and a half above the apex of the malleolus, and is continued to its insertion into the tubercle of the scaphoid bone. The proper place, then, for division of the tendon, is about two inches above the end of the malleolus.

In a young and fat child, where the inner edge of the tibia cannot be distinctly felt, the best guide to the tendon is a point midway between the front and the back of the ankle. An incision in front of this point might injure the internal saphena vein; behind this point, the posterior tibial artery.

119. =Tendons behind outer ankle.=--Behind the malleolus externus we feel the two peroneal (long and short) tendons. They lie close to the edge of the fibula, the short one nearer to the bone. In dividing these tendons, the knife should be introduced perpendicularly to the surface, and about two inches above the apex of the ankle, so as to be above the synovial sheaths of the tendons.

=Tendons in front of ankle.=--Over the front of the ankle, when the muscles are in action, we can see and feel, beginning on the inner side, the tendons of the tibialis anticus, the extensor longus pollicis, the extensor longus digitorum, and the peroneus tertius. They start up like cords when the foot is raised, and are kept in their proper relative position by strong pulleys formed by the anterior annular ligament. Of these pulleys the strongest is that of the extensor communis digitorum. When the ankle is sprained, the pain and swelling arise from a stretching of these pulleys and effusion into their synovial sheaths. A laceration of one of the pulleys and escape of the tendon is extremely rare.

The place for the division of the tendon of the tibialis anticus, so as to divide it below its synovial sheath, is about one inch before its insertion into the cuneiform bone. The knife should be introduced on the outer side, so as to avoid the dorsal artery of the foot.

Now trace the lines of the arteries, and the landmarks near which they divide.

120. =Popliteal artery.=--About one inch and a quarter below the head of the fibula, or say one inch below the tubercle of the tibia, the popliteal artery divides into the anterior and posterior tibial. The peroneal comes off from the posterior tibial about three inches below the head of the fibula.

Consequently we may lay down, as a general rule, that, in amputations one inch below the head of the fibula, only one main artery, the popliteal, is divided. In amputations two inches below the head of the fibula, two main arteries, the anterior and posterior tibial, are divided. In amputations three inches below the head, three main arteries, the two tibials and the peroneal, are divided.

121. =Anterior tibial artery.=--The anterior tibial artery comes in front of the interosseous membrane, one inch and a quarter below the head of the fibula, and here lies close to this bone. Its subsequent course is defined by a line drawn from the front of the head of the fibula to the middle of the front of the ankle. This line corresponds pretty nearly with the outer border of the tibialis anticus all the way down. If this muscle be put in action, its outer border (the intermuscular line) is plainly seen, and the incision for the ligature of the artery in any part of its course may be defined with the greatest precision. The artery can be felt beating and can be compressed where it crosses the front of the tibia and ankle.

122. =Posterior tibial artery.=--The posterior tibial commences about one inch and a quarter below the head of the fibula. Its subsequent course corresponds with a line drawn from the middle of the upper part of the calf to the hollow behind the inner ankle, where it can be felt beating distinctly about half an inch behind the edge of the tibia. A vertical incision down the middle of the calf would reach the artery under cover of the gastrocnemius and soleus. A vertical incision along the middle third of the leg, about half an inch from the inner edge of the tibia, would enable the operator to reach the artery sideways, by detaching from the bone the tibial origin of the soleus.

123. =Saphena veins.=--The subcutaneous veins on the dorsum of the foot form an arch convex towards the toes (as on the back of the hand), from which issue the two main subcutaneous trunks of the lower limb, the internal and external saphena veins. The internal saphena vein can be always plainly seen over the front of the inner ankle. Its further course up the inner side of the leg, knee, and thigh to its termination in the femoral is not in all persons manifest.

The external saphena vein runs behind the outer ankle and up the middle of the calf to empty itself (generally) into the popliteal vein.

THE FOOT.

What are the bony landmarks which guide us in the surgery of the foot?

124. =Points of bone.=--Along the inner side of the foot, beginning from behind, we can feel--1, the tuberosity of the os calcis; 2, the projection of the internal malleolus; 3, the projection of the os calcis, termed ‘sustentaculum tali,’ about one full inch below the malleolus; 4, about one inch in front of the malleolus internus, and a little lower, is the tubercle of the scaphoid bone; the gap between it and the sustentaculum tali being filled by the calcaneo-scaphoid ligament and the tendon of the tibialis posticus, in which there is often a sesamoid bone; 5, the internal cuneiform bone; 6, the projection of the first metatarsal bone; 7, the sesamoid bones of the great toe.

Along the outer side of the foot we can feel--1, the external tuberosity of the os calcis; 2, the external malleolus; 3, the peroneal tubercle of the os calcis, one inch below the malleolus, with the long peroneal tendon below it, and the short one above it; 4, the projection of the base of the fifth metatarsal bone.

125. =Lines of joints.=--In fat persons the following rules for finding the joints may be of service as regards the surgery of the foot:--

The level of the ankle joint lies about half an inch above the end of the inner malleolus. This is worth remembering in performing ‘Syme’s’ amputation.

The tubercle of the scaphoid bone is the best guide to the astragalo-scaphoid joint which lies immediately behind it; and the plane of this joint is in the same line as that of the calcaneo-cuboid. Thus a line drawn transversely over the dorsum of the foot, behind the tubercle of the scaphoid, would strike both the joints opened in ‘Chopart’s’ operation.

Place your thumb on the tubercle of the scaphoid, and measure about one inch and a half in front: here you find the joint between the internal cuneiform bone and the metatarsal bone of the great toe. This point is useful in Lisfranc’s operation, which consists in the removal of the metatarsal bones.

The line of the calcaneo-cuboid joint lies midway between the external malleolus and the (tarsal) end of the metatarsal bone of the little toe.

The projection of the fifth metatarsal bone is the guide to the joint between it and the cuboid.

Notice that the line of the joints between the metatarsal bones and the first phalanges lies a full inch farther back than the interdigital folds of the skin. This is a point to be remembered in amputating the toes.

126. =Dorsal artery.=--The line of the dorsal artery of the foot is from the middle of the ankle to the interval between the first and second metatarsal bones. The artery can be felt beating over the bones along the outer side of the extensor longus pollicis, which is the best guide to it.

127. =Bursa.=--The synovial sheath of the extensor longus pollicis extends from the front of the ankle, over the instep (apex of the internal cuneiform bone) as far as the metatarsal bone of the great toe. There is generally a bursa over the instep, above, or it may be, below, the tendon.

There is often a large irregular bursa between the tendons of the extensor longus digitorum, and the projecting end of the astragalus, 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 astragalus.

128. =Plantar arteries.=--The course of the external plantar artery corresponds with a line drawn from the hollow behind the inner ankle obliquely across the sole nearly to the base of the fifth metatarsal bone; from thence the artery turns transversely across the foot, lying (deeply) near the bases of the metatarsal bones, till it inosculates with the dorsal artery of the foot in the first interosseous space.

The course of the internal plantar corresponds with a line drawn from the inner side of the os calcis to the middle of the great toe.