How often is it safe to have a nerve block with fluoroscopy?

3 per 6 months. I try to limit the steroid exposure to 3 injections per 6 months. Not all blocks require steroid and 3 per 6 months is not an absolute.
Wrong question! Fluoroscopic guidance helps quide the needle for accurate placement and injection. I do not agree with the "apin treatment" priciple that you need as course of three. If no benefit is achieved with the first injection, subsequent ones will not deliver. Keep in mind, old-time anesthiologists did nerve blocks without fluoroscopic guidance!