Abstract: A proximal humeral prosthesis that is particularly designed for treating a fractured humerus. The prosthesis comprises a head corresponding to the humeral head of a patient, and a stem having a proximal end to which the head is mounted. The prosthesis has a central plane coincident with the longitudinal axis of the stem about which it has a mirror axis of symmetry. One, or preferably pair of, projecting ribs are positioned at or near the proximal end of the stem adjacent the head. The projecting ribs are offset in opposite directions relative to the center plane at substantially identical offset angles (e.g., about 20.degree. to about 40.degree.) approximating the greater or lesser tuberosity of the humerus. Also disclosed is a method of treating a fractured humerus with this prosthesis.