Condyle laterotrusive mediotrusive movements

[Silverback]

When the mandible performs a laterotrusive movement, the laterotrusive-side condyle moves primarily about which of the following axes?

A Vertical
B Sagittal
C Horizontal
D Transverse


When the mandible performs a laterotrusive movement, the mediotrusive-side condyle moves primarily about which of the following axes?


A Vertical
B Sagittal
C Horizontal
D Transverse


First one is A, is the second one C?

Its strange for the first one, since I figure because the working side condyle (laterotrusive) is rotating it would be in the horizontal axis, but the answer is A for the first one, is the second answer still A?

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[D.D.S.]

From Okeson's book on TMD...

Horizontal Axis of Rotation

Mandibular movement around the horizontal axis is an opening and closing motion. It is referred to as a hinge movement, and the horizontal axis around which it occurs is therefore referred to as the hinge axis (Fig. 4-2). The hinge movement is probably the only example of mandibular activity in which a "pure" rotational movement occurs. In all other movements, rotation around the axis is accompanied by translation of the axis.

When the condyles are in their most superior position in the articular fossae and the mouth is purely rotated open, the axis around which movement occurs is called the terminal hinge axis. Rotational movement around the terminal hinge can be readily demonstrated but rarely occurs during normal function.

Frontal (Vertical) Axis of Rotation

Mandibular movement around the frontal axis occurs when one condyle moves anteriorly out of the terminal hinge position while the vertical axis of the opposite condyle remains in the terminal hinge position (Fig. 4-3). Because of the inclination of the articular eminence, which dictates that the frontal axis tilt as the moving or orbiting condyle travels anteriorly, this type of isolated movement does not occur naturally.

Sagittal Axis of Rotation

Mandibular movement around the sagittal axis occurs when one condyle moves inferiorly while the other remains in the terminal hinge position (Fig. 4-4). Because the ligaments and musculature of the TMJ prevent an inferior displacement of the condyle (dislocation), this type of isolated movement does not occur naturally. It does occur in conjunction with other movements, however, when the orbiting condyle moves downward and forward across the articular eminence.

Let me know if this helps...

 

[Silverback]

Thank you! I had it backwards, I was thinking of the hinge movement (opening and closing the jaw) as being in the "vertical axis" since the path it travels is in the vertical axis. This helped a lot.