THE LEG AND ANKLE.
115.Bony points.—The tubercle of the tibia (for the attachment of the ligamentum patellæ), the sharp front edge called the shin, and the broad flat subcutaneous surface of the bone can be felt all the way down. The inner edge can be felt too, but not so plainly. The lower third is the narrowest part of the bone and the most frequent seat of fracture.
The head of the fibula is a good landmark on the outer side of the leg, about one inch below the top of the tibia and nearly on a level with the tubercle. Observe that it is placed well back, and that it forms no part of the knee-joint, and takes no share in supporting the weight.
The shaft of the fibula arches backwards, the reverse of the shaft of the tibia. The fact of the bones not being on the same plane should be remembered in flap amputations. The shaft of the fibula is so buried amongst the muscles, that the only part to be distinctly felt is the lower fourth. Here there is a flat triangular subcutaneous surface, between the peroneus tertius in front, and the two peronei (longus and brevis) behind. Here is the most frequent seat of fracture.
116.Malleoli.—The shape and relative position of the malleoli should be carefully studied, as the great landmarks of the ankle. The inner malleolus does not descend so low as the outer, and advances more to the front: at the same time, owing to its greater antero-posterior depth, it is on the same plane as the outer behind. The lower border of the inner malleolus is somewhat rounded, and the slight notch in it for the attachment of the lateral ligament can be felt. The outer malleolus descends lower than the inner, thus effectually locking the joint on the outer side. Its shape is not unlike the head of a serpent. Viewed in profile, it lies just in the middle of the joint.
In Syme’s amputation of the foot at the ankle, the line of the incision should run from the apex of the outer malleolus, under the sole to the centre of the inner.
In a well-formed leg, the inner edge of the patella, the inner ankle, and the inner side of the great toe, should be in the same vertical plane. Look to these landmarks in adjusting a fracture or dislocation, keeping at the same time an eye upon the conformation of the opposite limb.
There are several strong tendons to be seen and felt about the ankle.
117.Tendo Achillis.—Behind is the tendo Achillis. It forms a high relief, with a shallow gutter on each side of it. The narrowest part of the tendon, where it should bedivided in tenotomy, is about the level of the inner ankle; below this it expands again to be attached to the lower and back part of the os calcis. Seen in profile, the tendon is not straight, but slightly concave—being drawn in by an aponeurosis which forms a sort of girdle round it. This girdle proceeds from the posterior ligament of the ankle; and, though most of its fibres encircle the tendon, some of them adhere to and draw in its sides. All this disappears when the tendon is laid bare by dissection.
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, beginningon 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 ligatureof 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.