The superficial superior internal articular artery, a branch of the femoral, is given off by the artery immediately before its termination ; it arises from the front of the vessel, descends nearly in the course of it, escapes from the femoral canal in company with the saphenus nerve, and, holding generally the same relation to that nerve which the femoral itself does, may hence be mistaken for that artery at the inferior putt of its course.
Thus the relations of the vessel are here in several particulars the reverse of those in its former stages, and the methods most eligible for adoption in operation ought to be varied accordingly. Operation in its last stage is seldom required, but it may be necessary, as in wounds of the artery at that part, in which case the mode of proceeding with regard to the sartorius and to the artery should be the reverse of that recommended for the upper stage, the muscle being to be displaced inward in order to expose the artery, and the separation of the latter from the vein to be effected in the same direction.
At the termination of its third stage the artery passes into the ham and there receives the name of popliteal: it enters the popliteal region through an elliptical aperture situate to the inside of the femur at the junction of its middle and inferior thirds, and upon a plane with its posterior face, the longer diameter of which corresponds to the course of the artery, and which is circumscribed by the lower mar gin of the united tendons of the adductor longus and the adductor magnus above, by the connection between the tendon of the adductor magnus and that of the vase's internus below ; by the tendon of the adductor magnus inter nally, and by that of the vastus internus exter nally : in passing through, the artery carries with it a prolongation of the femoral sheath, by which the poplitcal vessels become invested and connected.
Varicties.—The superficial femoral artery sel dom presents a variation from its accustomed d is position,so much so that it may almost be held to be uniform in this respect: however two forms of deviation have been observed, rare in occur rence, but of great importance in a practical point of view. Two instances of the first ab normal arrangement are recorded, one of which occurred to Sir Charles Bell, and has been pub lished by him in Anderson's Quarterly Journal for the year 1826 : the second is preserved in the Museum of the College of Surgeons, and has been described in the fourth volume of the Dublin Hospital Reports by Dr. Houston,
Conservator to the Museum. In these cases the femoral artery divided into two vessels of nearly equal size, which pursued the usual course of the artery side by side and very close together, not, however, in contact, but contained in distinct compartments of the sheath and separated by a septum : hence the existence of the second artery might in operation easily pass unobserved, it not being brought into view by opening the sheath of the other. One was also larger than the other, and situate internal and on a plane posterior to it. In Bell's case the discovery was the consequence of the un fortunate event of an operation for popliteal aneurism ; the operation was performed in the middle third of the thigh. The pulsation of the aneurism, which was arrested on the appli cation of the ligature, returned after an interval of some seconds, and became nearly as distinct as before : it ceased again upon the third day, but the patient was carried off on the sixth day by an erysipelatous inflammation of the thigh. On examination after death, it was ascertained that the disposition, which has been described, was present, and that but one of the two vessels had been tied.
The second form of deviation is a high bifurcation into the posterior tibial and peroneal arteries: of this an instance* has been recorded by Sandifort, in which the division took place immediately below Poupart's ligament ; and Portalf states that the crural artery has been seen to divide into two large branches shortly after Its escape from the abdomen, and then there were two popliteal arteries: he further states that among individuals, in which the brachial artery was bifurcated higher than usual, the crural artery was so also in a remarkable proportion.* A division of the femoral artery into two trunks of equal size, running parallel and so near together, that they might be conveniently included in one ligature, is recorded by Gooch in the Philosophical Transactions for the year 1775, it being the third instance in amputations of the thigh, in which he had observed such a Items natant in the arterial system ; but it is not mentioned whether they were instances of the first or of the second kind of variety : he himself, whether from examination or from in ference, appears to have concluded that both trunks were prolonged into the lower part of the limb.