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Fryette's principles are fundamental concepts in osteopathic and chiropractic manipulative medicine that describe the mechanics of spinal motion. The movement of the C1-C2 vertebrae, which are the first and second cervical vertebrae, is best explained by Type II mechanics.

According to Fryette's principles, Type II mechanics pertain specifically to the movement of a single vertebral segment in isolation when that segment is in a neutral position. In this scenario, when the vertebra is side bent to one side, it will rotate to the same side. This is particularly relevant at the C1-C2 level due to the unique articulations and the relationship of these vertebrae to each other, allowing for significant rotation but limited lateral bending.

Type I mechanics, in contrast, describes a neutral position involving multiple segments, where side bending and rotation occur in opposite directions. Type III deals with the rotational and side bending mechanics across multiple levels, indicating that the motion occurs in all planes. Type IV is not typically a recognized principle in the context of Fryette's principles concerning vertebral motion.

Therefore, the movement of the C1-C2 vertebrae aligns with Type II mechanics due to their unique structural and functional characteristics, allowing for significant rotation and