Normal axial relationships of the major joints.

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AN appreciation of the range of normal variation remains the continuing problem of the radiologist. Our recent attempts to establish from the literature the normal values for the axial relationships of the major joints of the body were met with a disturbing lack of data with documentation of sampling. Furthermore, some of the stated measurements in anatomic and radiologic anatomy texts are not easily reproducible in conventional roentgenograms and are therefore of little value to the radiologist. To overcome this deficiency and to provide a comprehensive single source for this information, we have undertaken a study of these axial relationships with a report of normal values. The Shoulder (Fig. 1) The axes derived anatomically for determination of the relationships of the humeral shaft to the head are difficult to determine roentgenographically. We have, therefore, derived a new relationship with more easily definable end points. Measurement is made with the arm in external rotation (anatomic position) (Fig. 1). The axis of the shaft (AB) is drawn between 2 points, each measured to lie in the midline of the diaphysis. The axis of the head (CD) is drawn between the apex of the greater tuberosity to the junction of the shaft with distal extremity of the articular surface of the head. This latter point is easily determined as that where the medial cortex changes from a band to a line. The acute angle at the junction of these lines was measured in 25 normal males ranging in age from seventeen to sixty-five years and 25 normal females aged nineteen to seventy-two years. Values obtained in the males ranged from 52° to 70° and in the females from 50 ° to 70 °. The average value for the males was 60°, for the females 62 °, and for the entire group 61°. There is apparently no significant sex viariation in this axial relationship. The Elbow (Fig. 2) The carrying angle of the elbow (CA) is the obtuse angle of intersection of the axes of the shafts of the humerus (AB) and the ulna (CD) measured on the radial side. The humeral angle (HA) is formed by the intersection of the line of axis of the humerus with a transverse line drawn tangentially to the most distal points of the articular surfaces of the trochlea and capitellum (EF). The ulnar angle (UA) is the corresponding angle of intersection of the line of axis of the ulna and the transverse line. These angles were measured in anteroposterior films of the elbow in 25 normal males ranging in age from twenty-one to sixty-six years and 25 normal females aged twenty-one to sixty-two years. Films were made with the arm fully extended, with the 2 epicondyles perfectly flat with respect to the film. Both the distal humerus and the proximal forearm must be in good contact with the film.