How often do patients go into septic shock. From spinal surgery? And do you tell the patients family when this happens?

Unusual. It is unusual for a patient to have septic shock from spinal surgery, although it is one of the known complications. This is more likely to occur if there was concurrent multi-trauma or other metabolic issues such as diabetes mellitus. Family should be informed about problems and complications.
Not much and always. It is rare to get sepsis post surgery on the spine more likely to get meningitis but still rare. It is always unethical to withhold info from patients and family.