1420 



CLINICAL AND TOPOGRAPHICAL ANATOMY 



when the forearm is pronated, between the head of the ulna and lower end of the 

 radius. The recessus sacciformis here may be enlarged in rheumatic and other 

 affections. The interosseous membrane not only ties the bones together and 

 gives attachment to muscles, but in falls on the hand it enables the ulna to partici- 

 pate in the shock. 



The following are important points with regard to the bones. Common fractures. Ole- 

 cranon. — This usually takes place at the constricted centre of the semilunar (greater sigmoid) 

 notch or the junction of the olecranon with the shaft. A fall is here the usual cause, and 

 the heavier the fall, the more frequently is the fracture nearer the shaft, though displacement is 

 now likely to be slight, owing to the abundance of fibrous and muscular structures on both sides 



Fig 1138. — Diagram of the Anastomoses of the Brachial Artery. 

 (MacCormac and Anderson.) 



Anterior curcumflex — 

 Posterior circumflex 



Superior radial collateral (exces- 

 sively large) 



Profunda 



Middle collateral- 



Radial collateral 



Posterior interosseous 

 recurrent 



Radial recurrent 



Posterior interosseous 

 recurrent 



Superior ulnar collateral 



Thoraco -acromial ■ 



Long thoracic 



—Subscapular 

 Circumflex scapular 



Descending branch of 

 transversa colli 



Inferior ulnar collateral 



Transverse branch of inferior 



ulnar collateral 

 Anastomosis of anterior ulnar recurrent 

 with inferior ulnar collateral 



Anastomosis of posterior ulnar recurrent 

 with inferior ulnar collateral 



Anterior ulnar recurrent 

 Posterior ulnar recurrent 



Posterior interosseous from common interosseous of ulnar 



of the fracture. The shaft of one or both hones. Usual site, about the middle or a little below it, 

 fracture of the rarlius being more frequent from its connection with the hand. In these fractures 

 the chief muscular agencies are— (1) the extensors and flexors in drawing the lower fragment or 

 fragments upward, forward, or backward, according to the direction of the fracture; (2) the 

 biceps in drawing the upper fragment of the radius upward; (3) the influence of the pronator 

 teres, if the fracture is, as usual, below it, and (4) that of the quadratus in drawing the lower 

 fragments together. Thus the chief i)i'actical points are— (a) the reduction of displacement, 

 wliether antero-posterior or lateral; (h) the greater the number of fragments, the greater the 

 tendency to union acro.ss the interosseous space, with its embarrassing results, and the greater 

 the need of a su[)inated position in the setting; (r) the risk of gangrene here from the facility 

 with whi(;h the vessels are compres.sed against the contiguous bones, especially in flexion of 

 the forearm ; and the consequent need of attention to the width of the splints and the bandaging; 

 (d) Mie readiness with which ischa'mic paralysis may rapidly and insidiously be caused. Colles' 

 fracture. Jlere, after a fall on the hand, the radius gives way usually at its weakest part, about 



