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Reliability of spinal displacement analysis of plain X-rays: a review of commonly accepted facts and fallacies with implications for chiropractic education and technique.

BACKGROUND
Current medical, biomechanical, and chiropractic literature indicates that X-ray line drawing analysis for spinal displacement is reliable, with high Interclass Correlation Coefficients (ICCs) found in most studies. Normal sagittal spinal curvatures are being accepted as important clinical outcomes of care; however, just the opposite is taught in many chiropractic college radiology courses.


OBJECTIVE
To review the current literature on X-ray line drawing reliability and abnormal static lateral positions.


DATA SOURCES
Searches were performed on Medline, Chiro-LARS, MANTIS, and CINAHL on X-ray reliability, normal spinal position, and sagittal spinal curvatures as clinical outcomes.


RESULTS
X-ray line drawing analysis for spinal displacement was found to have high reliability with a majority of ICCs in the .8-.9 range. The reliability for determining X-ray pathology was found to be only fair to good by both medical doctors and chiropractors and by both chiropractic and medical radiologists, with a majority of ICCs in the range .40-.75. Muscle spasms, facet hyperplasia, short pedicles and patient positioning errors have not been shown to alter sagittal plane alignment. The sagittal spinal curves are desirable clinical outcomes of care in surgery, physical therapy, rehabilitation and chiropractic. These results contradict common claims found in the indexed literature.


CONCLUSION
X-ray line drawing is reliable. Normal values for the sagittal spinal curvatures exist in the literature. The normal sagittal spinal curvatures are important clinical outcomes of care. Patient positioning and postural radiographs are highly reproducible. When these standardized procedures are used, the pre-to-post alignment changes are a result of treatment procedures applied. Chiropractic radiology education and publications should reflect the recent literature, provide more support for X-ray line drawing analyses and applications of line drawing analyses for measuring spinal displacement on plain radiographs.