THE POPLITEAL ARTERY. 833 



the artery and similarly influenced. Ultimately there is apt to be oedema of the leg 

 from interference with the venous circulation, or erosion of the posterior lower sur- 

 face of the femur, or great pain with weakness of the leg from pressure on the inter- 

 nal popliteal nerve, or even moist gangrene if the aneurism has leaked or burst and 

 the venous current has been cut off by the pressure of the effused blood confined for 

 a time within narrow limits and under great pressure by the fascia of the region 

 (page 646). 



Compression of the popliteal may be effected directly at its upper end by pres- 

 sure forward, so that it is flattened out against the femur, only a little fatty connecti\e 

 tissue intervening. It is almost impossible, however, to avoid including the thick- 

 walled vein which is nearer the surface and very closely attached to the artery. 

 Compression is therefore almost invariably applied to the common femoral (page 

 824). On account of the shortness of the popliteal — and the consequent proximity 

 of a ligature to the diseased portion, if the vessel itself is tied — the superficial femoral 

 at the point of election — the apex of Scarpa's triangle — is usually selected for liga- 

 tion when that becomes necessary. 



Ligation of the popliteal artery is effected at either : (i) its upper, or (2) its 

 lower third, the depth of the middle portion and the density of the lateral fascial 

 border of the space in which it lies rendering it unsuitable for operation. 



1. The patient being prone with the leg extended, an incision is made along the 

 external border of the semimembranosus muscle, beginning at the junction of the 

 middle and lower thirds of the thigh. The skin and fascia and some fatty tissue 

 having been divided, the muscle is drawn inward, and the vessel will be found with 

 the internal popliteal nerve external to it and much more superficial, and the vein 

 external and behind it, — i.e., nearer the surface of the popliteal space — and closely 

 adherent. The needle is passed from without inward. 



2. An incision is made beginning opposite the line of the articulation a little 

 external to the middle of the popliteal space, the inner head of the gastrocnemius 

 being slightly larger than the outer head. The external saphenous vein lying in the 

 superficial fascia is drawn to one side, the fascia is divided, and the two heads of the 

 gastrocnemius are exposed and separated with the finger, the knee being a little 

 flexed so as to relax them. At the bottom of the interval between them will be found 

 the nerve and vein lying to the inner side of the artery and somewhat superficial to it. 

 The needle is passed from within outward. 



The collateral circulation is carried on from above the ligature by means of (a) 

 the superior articulars ; (^b) the anastomotica magna ; (r) the descending branch of 

 the external circumflex and the terminal portion of the profunda anastomosing 

 respectively with («) the inferior articulars ; {b) the tibial recurrent ; and (if) the 

 superior fibular and branches of the popliteal. The rete patellae takes part in this 

 anastomosis. 



1. The Muscular Branches. — These (Fig. 736) are arranged in two groups, 

 and are supplied to the muscles which bound the popliteal space. The superior group 

 consists of a variable number of small vessels which pass to the biceps, semimembra- 

 nosus, and semitendinosus, while the inferior group is composed of some small 

 branches which pass to the popliteus muscle, and two larger vessels, the largest of all 

 the vessels which arise from the popliteal, which pass respectively to the inner and 

 outer heads of the gastrocnemius, and are termed the sural arteries (aa. surales). 

 They arise just as the popliteal is passing beneath the inner head of the gastrocnemius. 



2. The Articular Branches. — These (Fig. 736) are five in number, four 

 being arranged in pairs, two above and two below, while the fifth is unpaired or 

 azygos. The paired branches wind around the femur and the capsule of the knee- 

 joint towards the front, where they anastomose with one another, and with adjacent 

 vessels to form a rich circumpatellar anastomosis. They give off branches to the 

 capsule of the knee-joint and also to the neighboring muscles. 



(a and b^ The internal and external superior articular branches (aa. genu superior medialis 

 ct lateralis) arise opposite each other and pass transversely above the correspondino; heads of the 

 gastrocnemius. The external one then passes beneath the biceps and winds around the femur 



53 



