Horizontal condylar growth cannot be accurately measured when related to a vertical base line (perpendicular to SN-6°); and it is highly improbable that vertical condylar growth can be completely accurately measured from a vertical base line perpendicular to S-N-6°. This is because condylion is so difficult to locate accurately.

It is important to separate condylar growth into its component parts, vertical and horizontal, because they have different functions. Vertical condylar growth has the function of moving the gonion angle down and the chin forward. While horizontal growth only moves the chin forward.

In order to measure horizontal and vertical growth accurately, they must be measured from the mandible itself. The technique for this measuring is as follows: The two tracings are superimposed on SN, registered on the center of sella turcica, and a pinhole is punched through both tracings in the region of the condyle. Then the tracings are superimposed on the mandibular plane and registered on the lingual aspect of the symphysis. The pinhole movement is then measured both vertically and horizontally. Please see Figs. 1 and 2.
Fig. 1: This is a nine year growth study of a male. Vertical condylar growth (30 mm) is measured vertically perpendicular to sella horizontal, and anterior horizontal condylar growth (5 mm) is measured perpendicular to the great divide. See Article 24 of the Schudy Chronicles.


Fig. 2: This is an eight year growth study of a male. Vertical condylar growth (25 mm) is measured perpendicular to sella horizontal, and posterior horizontal condylar growth (11 mm) is measured perpendicular to the great divide. See Article 24 of the Schudy Chronicles.

The reason it is essential that condylar growth be measured in this way, is that any rotation of the mandible is automatically captured; while measuring from a vertical base line, the rotation is missed. Measuring from a vertical base line drawn downward from sella assumes that the entire mandible moves as the condyle moves-translates with the condyle movement. That is why measurement from a vertical base line shows anterior condylar growth, that really has not happened. In effect, it is separating the condyle from the rest of the mandible, because it is measuring the condyle from one landmark and the rest of the mandible from another landmark-the condyle from the cranial base and the rest of the mandible from the mandible itself.

In the period from 1964 to 1977 four American1,2,3,4 investigative groups published studies in which condylar growth was broken down into its components, vertical and horizontal. Only recently has the literature contained reports of studies where other investigators5 have also studied vertical and horizontal mandibular growth. Personally, I am delighted that colleagues are now showing appreciation for the refinement of the study of the growth of the mandible.


Bibliography ^1. Creekmore, T.D., Inhibition and Stimulation of Vertical Growth of the Facial Complex, Angle Orthod. 1967; 37: 285-97.

^2. Schudy, George F., A. Longitudinal Cephalometric Study of Post Treatment Growth; Its Implications in Orthodontic Treatment, Am. J. Of Orthod. 1974; 65:39.

^3. Robert L Isaacson, D.D.S., Ph.D., Richard L Zappel, D.D.S., M.S., Frank Worms, D.D.S., M.S.D., Richard R. Bevis, D.D.S., Ph.D., and T. Michael Speidel, D.D.S,, M.S.D., The Effects of Mandibular Growth on the Dental Occlusion and Profile, Angle Orthodontist April 1977.

^4. Schudy, Fred F., Vertical Growth Versus Anteroposterior Growth as Related to Function and Treatment, Angle Orthodontist vol.34, April 1964.

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