@CSWright: the tailbone shows just fine on a high resolution MRI with full spinal imaging slices and contrast.

The problem is that there is no coding for sacral spine imaging so it typical it gets done as a general pelvic MRI. The image field is far too large and the slices aren't tight enough to see the spine well. It's like taking a photo of something you want to see up close from afar.

It's not a limitation of the MRI equipment, if you find a place with a (3T) high resolution MRI. Request the pelvic MRI be ordered as for full spinal imaging of the sacrum to coccyx, then they should include MRI imaging protocols for the spine that include up close imaging and the axial slices of the spine. There are also specialized protocols to view the pelvic levator and other pelvic muscle and nerve issues. It's how Tarlov cysts are best detected as well as other neuropathic pelvic anomalies like pudendal neuralgia.

Another option is to request an MR neurography be done at the same time so that the spinal nerves can be better viewed.