During left lateral deviation, what is the movement of the condylar heads?

During left lateral deviation, the movement of the condylar heads involves a complex interplay of rotational and translational movements. The left condylar head, which is the one on the side of the deviation, does not move significantly; instead, it generally spins posteriorly.

This spinning motion allows for the appropriate adjustment of the jaw position as the right side of the mandible moves laterally to the left. As the left condylar head spins, the right condylar head moves anteriorly and inferiorly to allow the jaw to shift over to the left side. Therefore, the spinning of the left condylar head is essential in facilitating the lateral deviation while maintaining contact with the articular disc.

Other movements described in the options do not accurately represent the biomechanics involved in left lateral deviation. The right condylar head's movement is significant, but it is the posterior spin of the left condylar head that most clearly defines this lateral movement.