surface of the os calcis, where it anastomoses with the external malleolar, tarsal, and anterior peroneal vessels. Internal Annular Ligament.-The connections of this thickened band of deep fascia should be carefully studied, and also the arrangement of the structures which pass under cover of it into the sole of the foot. It bridges across the hollow between the prominence of the os calcis and the internal malleolus, and it is attached to both. Above, it is chiefly connected with that layer of the deep 18 17 16 15 14 13 12 5 6 7 8 9 10 11 FIG. 60.-Dissection of the inner ankle. A. H. Abductor hallucis, thrown forwards from its origin. fascia which intervenes between the superficial and deep muscles on the back of the leg, but it is also continuous with the general aponeurotic investment of the limb. Inferiorly, its lower margin gives origin to the abductor hallucis, and is connected with the inner portion of the plantar fascia. Passing under cover of this ligament the dissector will observe (a) the posterior tibial vessels and nerve; (b) to the outer side of these, the tendon of the flexor longus hallucis; (c) to their inner side, the tendons of the flexor longus digitorum and tibialis posticus. From within outwards these structures lie in the following order :— 1. Tendon of tibialis posticus. 2. Tendon of flexor longus digitorum. 4. Posterior tibial nerve. 5. Tendon of flexor longus hallucis. The tendons are isolated from each other and from the vessels and nerve by septa, which pass from the deep surface of the ligament to ridges on the bones. These septa can be demonstrated by slitting up the ligament, for a short distance, in the line of each of the tendons: each of the three sheaths will then be seen to be lined by a glistening synovial membrane. Anastomosis around the Ankle-joint.—The dissector should next satisfy himself with regard to the anastomosis of arteries which takes place around the ankle-joint. On the outer aspect of the joint he will observe inosculations taking place between branches of the following arteries:(a) external malleolar; (b) anterior peroneal; (c) posterior peroneal; and (d) tarsal. On the inner aspect of the joint the internal malleolar branch of the anterior tibial anastomoses with small twigs from the internal calcanean branch of the posterior tibial. SOLE OF THE FOOT. In this dissection the dissector will meet with the following structures :— 1. Superficial fascia and cutaneous vessels and nerves. 2. Deep plantar fascia. 3. Superficial muscles, Abductor hallucis. 4. External and internal plantar vessels. 6. Tendons of flexor longus hallucis and flexor longus digitorum. 8. Flexor brevis hallucis, adductor obliquus hallucis, and adductor transversus hallucis. 9. Flexor brevis minimi digiti. 10. Plantar arterial arch. II. Arteria magna hallucis. 12. Tendons of peroneus longus and tibialis posticus. 13. Interosseous muscles. Reflection of Skin. The limb should be placed upon the table, with the sole of the foot facing the dissector, and the ankle supported by a good-sized block. Two incisions are required— (1) a longitudinal incision along the middle line of the sole, from the heel to the root of the middle toe; (2) a transverse cut, at the digital extremity of the mesial incision, across the sole at the roots of the toes. The skin should also be reflected from the plantar surface of each of the toes. be done by means of a longitudinal incision along its middle line. This can Superficial Fascia.-When the flaps of skin which are mapped out by the above incisions are reflected, the peculiar characters of the thick layer of superficial fascia become apparent. It is tough and granular, and in some respects resembles the superficial fascia which covers the tuber ischii. Traversing it are tough fibrous bands, which subdivide the fatty tissue into small lobules, and connect the thick skin of the sole with the plantar fascia. Dissection. The internal calcanean nerve, which has already been found piercing the internal annular ligament, should be traced to its distribution. It supplies the skin of the sole in the neighbourhood of the heel. The superficial fascia may now be removed. Divide it along the mid-lle line of the sole, and turn it outwards and inwards, cleaning at the same time the deep fascia. As the dissector approaches the outer and inner margins of the foot respectively, he will observe two furrows to extend forwards on each side of the central part of the deep fascia. Along the line of these a number of blood-vessels and some nerves will be seen piercing the deep fascia in order to reach the skin. Towards the heads of the metatarsal bones the digital vessels and nerves are unprotected by the deep fascia, and here the dissector must proceed cautiously. The nerves and vessels which go to the tibial side of the hallux and to the fibular side of the little toe are especially liable to injury, as they perforate the fascia further back than the others. A band of transverse fibres, which crosses the roots of the toes and lies over the digital vessels and nerves, should be noticed. It is the superficial transverse ligament of the toes. It is closely connected with the skin, where it forms the cutaneous webs between the toes. By forcibly separating the toes its connections will become evident. When the relations of this ligament have been studied it may be removed. Plantar Fascia.--The plantar fascia, which is now brought into view, will be noticed to consist of three portions (a) a central, and (b) two lateral parts. subdivision is indicated by a difference in the density of the three parts and by two shallow furrows which traverse the foot in a longitudinal direction, one upon either side of the strong central portion of fascia. Each of the three portions of fascia is in relation to a subjacent muscle. central portion covers the flexor brevis digitorum; the external lateral part clothes the abductor minimi digiti; and the internal lateral part covers the abductor hallucis. The The central portion of the plantar fascia stands out in marked contrast to the lateral portions in point of strength and density. Behind, where it is attached to the internal tuberosity of the os calcis, it is narrow, but it expands as it passes forwards, and, near the heads of the metatarsal bones, splits into five processes, which are bound together by transverse fibres. In the intervals between the digital slips the digital vessels and nerves and the lumbrical muscles appear. Trace these processes forwards. One goes to the root of each toe, and there divides into two slips, which embrace the flexor tendons and become fixed VOL. I.-19 to the flexor sheaths and to the transverse metatarsal ligament on either side of the toe. In its arrangement, therefore, this portion of the plantar fascia closely resembles the central part of the palmar fascia. The lateral parts of the plantar fascia are weak in comparison with the central portion. They simply constitute aponeurotic coverings for the muscles which lie subjacent. A strong band is to be noted in connection with the outer part. It stretches between the prominence formed by the base of the fifth metatarsal bone and the external tuberosity of the os calcis. In connection with the plantar fascia two intermuscular septa have also to be studied. These pass upwards into the sole, along the longitudinal furrows which mark off the central portion of the fascia from the lateral parts. They consequently lie one upon either side of the flexor brevis digitorum, and form partitions which separate it from the abductor hallucis on the one side, and the abductor minimi digiti on the other. Dissection.—To demonstrate these septa, make a transverse incision through the central portion of the plantar fascia about an inch in front of the internal tuberosity of the os calcis, and also a longitudinal cut through the same piece of fascia, extending from the first incision along the middle line of the foot. Now raise the divided fascia and throw it outwards and inwards, Some difficulty will be experienced in effecting this, owing to its affording a surface of origin in its upper part to the subjacent flexor brevis digitorum. As we approach the margins of this muscle the septa are brought into view. Muscles and Tendons of the Sole. It is customary to look upon the muscles and tendons which we find in the dissection of the sole as being disposed in four strata, viz. First layer. Abductor hallucis. Tendon of flexor longus digitorum. Lumbrical muscles. Second layer. Tendon of flexor longus hallucis. |