396 On the Angle oi" the Elbow 



of flexion was determined by the chord of the arc which would be de- 

 scribed by moving the styloid process from maximum flexion to the 

 long axis of the humerus with the axis of the elbow as the center. The 

 degree of extension was determined by the chord of the arc described 

 by the styloid process between maximum extension and the projected 

 axis of the humerus. Accordingly when the elbow joint did not extend 

 to a straight line or when it hyperextended this amount was respectively 

 subtracted from or added to 180 degrees. The amount of deflection was 

 determined for three positions measuring from the styloid process with 

 the elbow flexed, extended and at 90 degrees. The degree is determined 

 by the chord of the arc described by the styloid process intersecting the 

 sagittal plane at right angles in these three positions named above. In 

 case the deflection is out it is marked plus and in case it is in it is 

 marked minus. 



In the appended tables the first column gives the number of the cadaver. 

 The second column gives the length of the ulna from the styloid process 

 to the axis of the elbow joint. Next the angles of the humerus and the 

 ulna with the axis of the arm are given. These, together with the degree 

 of deflection of the forearm with the elbow joint extended to its maxi- 

 mum, always equal 180 degrees. Then follow the columns with the 

 degree of motion, from maximum flexion to maximum extension, 180 

 degrees being a straight line. The lateral angle is next given in three 

 positions and when it is marked minus it indicates that the arm turns in. 

 This takes place frequently when the elbow is flexed to its maximum, 

 occasionally when at right angles, and not at all when it is extended. In 

 other words, when the arm is extended and supinated the whole wrist 

 including the styloid process lies to the outward of a line drawn through 

 the middle of the upper third of the shaft of the humerus and the 

 coronoid process of the ulna. All arms are deflected laterally. 



Braune and Kyrklund have shown conclusively that the elbow joint 

 is a pretty perfect hinge joint and that there is practically no screw 

 motion in it. As it flexes the ulna shifts a little, first outward then 

 inward, which motion causes the shaft of the humerus to rotate outward 

 nearly 6 degrees in case the forearm is flexed. For all practical purposes 

 the joint is a hinge joint, the axis being set obliquely at nearly 8-t de- 

 grees to both humerus and ulna. In all cases the styloid process of the 

 ulna deflects about 12 degrees when the arm is extended and when flexed 

 because the angles of the humerus and ulna are about equal, the ulna 

 lies in the sagittal plane of the humerus, i. e., the ulna comes to lie 

 directly upon the humerus and not upon the chest as is claimed by 

 Langer. In case the angle of the axis of the ulna is less than that of 



