ANKLE, REGION OF THE, (surgical anatomy), ( region tibio-tarsienne, Velp.) The relative positions and other particulars con nected with the parts found in the region of the ankle, owing to the numerous accidents which occur here, are matters of great interest to the surgeon. The extent and boundaries of this re gion are by no means so distinctly defined as those of many others ; hence, in isolating it for special description, the surgical anatomist is obliged to assign to it arbitrary or imaginary limits. We propose to adopt the following boundaries for this region, viz. superiorly a hori zontal line drawn round the leg two inches above the malleoli, and inferiorly a line drawn across the dorsum and sides of the foot at the same distance from those bony prominences. In this space are comprised the ankle-joint and several important vessels, tendons, and other soft parts well worthy of attention.
In examining the external characters of this region we notice four well-marked prominences, one on either side, termed malleolus, (internus v. externus); a third posteriorly, which cor responds to the tendo Achillis; and a fourth in front, resulting from the projection of the astra galus. The malleoli do not accurately.corres pond either in situation or shape to each other : the internal lies upon a plane superior and anterior to the external, and in a well formed person is much less sharp and prominent,— a fact, the recollection of which is of great im portance in estimating deformity or dislocation of the joint. The cylindrical prominence be hind, as it depends upon the tendo Achillis, will of course vary in size and tension accord ing to the relaxation or contraction of the gastrocnemii muscles. Upon either side of the tendo Achillis, between it and the malleo lus we meet with a deep groove, called by some the calceo-malleolar furrow : that upon the outside is extremely well marked, and we may here distinctly feel through the integu ments two of the peronei tendons : the internal calceo-malleolar groove is broader and shal lower, but of much greater interest, for through it, in addition to certain tendons, we have transmitted the principalvessels and nerves des tined for the sole of the foot. The anterior prominence, named in popular language, " the instep," is rounded in the transverse direction, and in some individuals projects much more than in others. On throwing the foot and toes into action, as in walking, we can here dis tinctly recognize the tendons of the tibialis anticus, extensor pollicis, extensor digitorum longus, and peroneus tertius, and almost in the mesial line may be felt pulsating distinctly the anterior tibial artery.
Having thus examined the landmarks which are to guide us in our anatomical investigation of this region, we may next proceed to inquire into the nature and relations of its constituent parts. Besides the bones, cartilages, and liga ments which immediately constitute the joint, and form the basis of the region, we have like wise several other structures entering into its formation ; • integuments, muscles, vessels, nerves, and fasciae are here arranged in suc cessive layers beneath each other. We shall accordingly describe four layers,— namely, 1. the skin ; 2. the subcutaneous cellular tissue ; 3. the fasciae; and 4. the tendons, vessels, and nerves, which lie in immediate contact with the articulation.
1. The skin forms a. complete investment for the whole region, but its structure and properties differ considerably in different situ ations. Upon the inner ankle it is smooth and thin, and possessed of but little extensibility ; so that in operating here, if we look forward to union by the first intention, it becomes a matter of great moment to preserve as much of the skin as possible. Owing to the same peculiarities of the integuments in this situ ation, DO less perhaps than to the frequent motion of the part, wounds and ulcers occur ring upon the inner ankle are extremely tedious and troublesome, in many instances laying bare the bone, and finally even occasioning its destruction. Upon the outer ankle, the skin is more pliant and extensible; hence the greater facility of healing wounds and ulcers in this part; and hence, too, the more frequent occur rence of abscess and extravasation beneath the surface. At the posterior part of the region the skin acquires great strength and thickness, becoming as it passes downwards still more dense and unyielding, approximating in fact to the character of the plantar integument. Upon the instep it is also of tolerable thick ness, particularly in those individuals whose feet are usually uncovered. In this situation, however, it is soft and extensible: its natural pliancy being still further increased by the secretion of numerous sebaceous follicles thickly scattered throughout its substance. It is here, owing to the frequent motions of the joint, thrown into transverse rugm, and hence, in making an incision, to give exit to matter, it may be proper to prefer a transverse to a vertical direction.