Tracing Transcranials in Gelb 4/7

	The transcranial is taken in relation to Optic Horizontal. Views are taken in clinch, rest and open. The view that is traced is the clinched view for both the left and the right side.
	The first parallel is drawn at the top of the fossa maintaining a parallel to the top edge of the film window.
	The second parallel is drawn at the bottom of the fossa parallel to the top edge of the film window.
	The third parallel is formed by dividing the distance between the top and bottom of the fossa and drawing a line parallel to the film window
	The first perpendicular extend from the top edge of the fossa. This should also be parallel to the edge of the film window.
	Trace the second perpendicular from the intersection of the slope of the fossa and the middle parallel line.
	Trace a second view of the film edges and the head of the condyle on a second sheet of acetate paper.
	Overlay the second acetate to the first and move the condyle so the bulk of it is in the Gelb 4/7 position while maintaining the parallels established by the film edge. On deep fossa cases, it is advisable to allow an extra 1 mm below the half way point to allow the condyle room to clear the slope of the eminence easier in translation. There must also be a 1.8 to 2.0 mm space left for the joint as measured by a perpendicular line from the condyle head to the slope of the fossa.

	Deep Space and Deep Fossa Clearance
	Gelb 4/7 numbers