Schematic drawing of antero-posterior elbow radiograph showing the alternative measurement of the trochlear angle. This method employs a line drawn through the redial head growth plate and coronoid which is parallel to the trochlear line. O- humeral axis; A- trochlear angle; B- capitellar angle; a- trochlear line; b- capitellar line; c- a line drawn through the radial head growth plate and coronoid which is parallel to the trochlear line.