The spine is made up of, from top to bottom, cervical vertebrae - then thoracic - then lurabar - then sacral. Lurabar and sacral are at the lower back - and sacralization is when the last lurabar vertebrae appears fused to the sacrum. A pseudarthrosis can be a developmental failure or if post-op it can be an incomplete fusion.
However, even with all this information, the test results have to be compared with the patient's symptoms and findings on examination.
Many people, even without pain, could have an MRI and be found to have something similar, or herniated discs, etc - but they'd never know as they don't have any accompanying symptoms.
