PRACTICAL CONSIDERATIONS : THE ELBOW-JOINT. 307 



locking of its bony constituents, preserving its ginglymoid character and preventing 

 the injurious effect of side strains, partly to the similar protective effect of its strong- 

 lateral ligaments, and somewhat to the laxity of its capsule, permitting of moderate 

 distention without undue tension. It is easily and often spontaneously immobilized 

 in the early stages of disease ; it then bears no weight and is but little exposed to 

 harmful increase of intra-articular pressure from muscular spasm ; and finally, as its 

 fixation does not, as in the joints of the lower extremity, interfere greatly with 

 moderate out-door exercise, the general resistant power is not so easily lowered. 

 Swelling first shows itself posteriorly on either side of the olecranon process, and 

 extends to the fossa over the head of the radius. In these directions the capsule is 

 thinnest and most lax and the synovial cavity is nearest the skin. As distention 

 continues there may be a bulging beneath the anconeus to the outer side of the 

 olecranon, or on the front of the elbow beneath the brachialis anticus and extending 

 towards the outer side, as it is limited internally by the thickening of the capsule 

 constituting the internal lateral ligament. 



Pus is apt to follow the same lines of least resistance, and discharge upon the 

 back of the arm on either side of the triceps, but especially on the outer side on 

 account of the attachment of the dense intermuscular fascia above the internal con- 

 dyle ; over the head of the radius beneath the external -condyle ; or in front to the 

 outer side of the tendon of the biceps, a position determined by the I'esistance of the 

 bicipital aponeurosis on the inner side. 



The radio-ulnar joint, which is part of the articulation, is often involved, affecting 

 the motions of pronation and supination. 



The upper radial epiphysis and most of the lower humeral epiphysis are within 

 the limits of the capsule, and may either be the starting-point of joint disease or 

 become secondarily involved. 



The position of semiflexion which gives the greatest ease, and is therefore 

 voluntarily assumed, is that which affords most room for synovial distention and 

 relaxes the muscles most immediately in relation with the joint. Distention of 

 the joint is easily distinguished from disease of the neighboring bursae. The 

 bursa over the olecranon, when enlarged, constitutes a single rounded superficial 

 prominence ; that beneath the triceps tendon, while it causes swelling on either 

 side of that structure, does not extend to or obliterate the fossa over the head 

 of the radius, nor does it cause a '"puffiness between the inner condyle and the 

 olecranon process when the arm is bent at a right angle" (Barwell). The bursae 

 beneath the brachialis anticus and between the tubercle of the radius and the biceps 

 tendon, if enlarged, cause a vague fulness over those regions, but none of the charac- 

 teristic appearances of synovitis. Chronic enlargement of the latter bursa, in a case 

 of Agnew, caused pressure paralysis of the muscles supplied by the median and 

 posterior interosseous nerves. 



The obliquity of the line of the elbow-joint (page 268) should be remembered 

 in the treatment of fractures involving the articulation. In obscure injuries about 

 the joint the position of acute flexion, with the hand upon the front of the chest, is 

 the one least likely to be followed by serious ankylosis, as in that position the full 

 functional value of this obliquity is more apt to be preserved than when the forearm 

 is at a right angle. The position is also the one in which it is easiest to retain in 

 place many fractures in the region of the elbow. Especially in fractures of the lower 

 end of the humerus, if the fragments are at once replaced, the coronoid process in 

 front and the muscular and tendinous structures behind hold them firmly and prevent 

 recurrence of deformity. If the fracture is intercondylar, or IJ -shaped, the acutely 

 flexed position not only holds the condyles in position, but tends to prevent by 

 pressure the involvement of the joint line by callus, which later would prove 

 obstructive. If either the coronoid or olecranon fossa, or both, be involved, it is 

 more important to prevent the filling up of the former than of the latter, as full flexion 

 is of far greater functional importance than full extension. If the condyles — espe- 

 cially the inner — be split off, the position relaxes the muscles that cause displacement. 

 It is also, of course, the most useful position of the limb in case ankylosis does occur. 



In excision of the elbow-joint the following anatomical points should be remem- 

 bered - (i) The lines of the various epiphyses. (2) The position of the ulnar nerve 



