Diagramming the Condyles

1. Diagramming the Condyles What is a Convergence Angle anyway?

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4. Base Posterior

5. Measuring Like Points • Find like points on the x-ray. • Should match from right to left • Try to stay around the orbits for your points. • With a straight edge, line up the like points from right to left and draw lines from the dot to the outer edge of the skull.

6. Draw Lines Across Points • Line up a straight edge ruler and draw across the like points. • Draw the line from lateral edge of skull to lateral edge of skull through the like points.

7. Draw a line across the dots • Measure the distance from the dots to the outer edge of the skull. • There should be no more than ¼ inch distance between the 2 like point measurements from right to left

8. Anterior Point 1 • Find the most lateral darkest point away from the dens in the neural canal. • The point where the anterior lateral mass intersects the anterior arch. • Place a dot on the right and left side.

9. Posterior Point 1 • Place a dot on the right and left intersection of the posterior arch of atlas and the lateral mass/condyle articulation. • This is posterior point 1.

10. Outline the Condyle • Outline the lateral edge of the condyle with a dotted line. • Start at the most anterior and trace around to the transverse foramen (TF), then at point 2 and trace up to the TF.

11. Connect Anterior and Posterior Points • With a straight edge, connect the Anterior and posterior points. • Draw the line ONLY from Anterior point 1 to Posterior point 1.

12. Bisecting the Condyle • With the straight edge, draw a line from the point 1’s to the lateral edge of the condyles 90 degrees from the line connecting your anterior and posterior point 1’s. • Place a dot in the middle of all 4 new lines.

13. Creating the Convergence Angles • With a straight edge ruler, scribe a line through the lines on the anterior and posterior condyles. • This line should be drawn through the orbits • Slide the Parallel straight edge out to the end of the most lateral edge of each condyle and draw a line at the orbit

14. Ear Marker Line • With a straight edge ruler, draw a line across the skull connecting the ear markers. • Line up the straight edge with the end points of the ear markers specifically made for the Blair BP.

15. Scribing the Middle Line • The middle line is scribed perpendicular to the ear maker line. • This line runs from A to P all the way through the skull. • The line can be drawn anywhere along the ear marker line. Just make sure it intersects both convergence angles.

16. Measuring Convergence Angles • Measuring from the middle line, the right and left convergence angles are found. • The right convergence angle is to the right of the middle line posterior to the ear marker line and to the left of the ear marker line when measured anterior to the ear marker line.

17. Convergence Angles (cont.) • The left convergence angle is measured to the left of the ear middle line posterior to the ear marker line, and to the right of the middle line when measured anterior to the ear marker line.

18. Label Convergence Angles • With the convergence angles Labeled, divide the orbits into 4 equal segments. • A dot is marked on the patient in the segment the convergence angle runs through. This will mark the vertical central ray when taking the Blair Protracto View.

19. Digital X-ray