Meaning of "their side for certain cervical levels"?

[size=150]Could you please help with the meaning of the bold texts in the following sentence:

The injection is performed using fluoroscopy guidance (weak x-ray) with the patient lying on their stomach or [color=blue]their side for certain cervical levels.[/size]

If the woman’s cervix is in an awkward place to reach when she is lying on her back, then the doctor may instruct her to lie on her side instead. In many cases, the cervix can be reached easier with the woman in this position.

Thanks for your quick answer!

I believe the sentence is talking about a person’s neck, not a woman’s cervix.
There are seven cervical vertebrae. At some cervical levels the injection is done with the patient lying on their stomach, and at other levels the injection is done with the patient lying on their side. The choice is made on the basis of ease and safety.