You raise a valid concern about intraobserver and interobserver reliability. Intraobserver reliability refers to how well one person can make the same measurement more than once. Interobserver reliability is the accuracy of those measurements when more than one person measures the same thing.
So, even if the same person makes the measurements, there’s room for error. Using the same method of measuring helps improve reliability of the studies when more than one person is making the measurements. The more advanced imaging technology with computerized radiograms (rather than the old standard X-ray films) is helping to improve the results, cutting down on errors.
Let the orthopedic surgeon who is following your daughter’s case know of your concerns. He or she can certainly do a review of all the films available from the beginning to the present. It’s even possible that although the films were taken by different radiology staff, your surgeon was the one reading them all anyway. Check it out and see what you find.