Finally, the greatest of all difficulties is the imperfect touch of the untrained palpater or the imperfect concentration of the trained. And this is always remediable.
ATLAS PALPATION
With patient in position A stand behind him and place the tips of the second fingers on the tips of the transverse processes of the Atlas, or first Cervical. It can be felt on each side just anterior and inferior to the mastoid process of the temporal bone. Let the first and third fingers rest respectively above and below the transverses and determine whether the Atlas is subluxated as a whole to the Right or to the Left.
Another convenient method is:
Place first fingers on mastoid processes, second on Atlas transverses, and third on angle of jaw. The three fingers of each hand then constitute the points of a triangle. Imagine the base line between the first and third fingers and measure the altitude as a line at right angles to this base line and reaching to the tip of the second finger as the apex of the triangle. The relation of the two altitudes determines the laterality of the Atlas. Thus, if the altitude of the right triangle is less than that of the left, the Atlas is laterally displaced to the Right.
The second matter to determine is the rotation of the Atlas. This is done by using the first and third fingers as probes to determine the amount of space between the transverse and the mandible in front or the mastoid behind. The intention is to compare the laterally prominent side with the other so that the letter A or P on the record will indicate the position of the prominent transverse compared with its fellow.
Next decide as to tipping. Still comparing the prominent transverse with the other, decide whether it is above or below the level of the other by the following method. Placing first three fingers one above the other with the second finger on the tip of the process, note which transverse is highest in the space beneath the ear. List the prominent side as S or Superior, I or Inferior.
Atlas palpation is rendered especially difficult by the special technic and by the interposing tendons of the sterno-cleido-mastoid muscle.