J Manipulative Physiol Ther. 1991 Jul-Aug; 14(6): 355-60.

Facet tropism: comparison of plain film and computed tomography examinations.

Cox JM, Aspegren DD, Trier KK.

Department of Sociology and Anthropology, Indiana University, Purdue University, Fort Wayne 46805.

This study compares the findings of plain film X-ray and computed CT examination in the diagnosis of facet orientation and the presence of tropism. Twenty consecutive patients having lumbar disc disease with sciatica were studied utilizing plain X-ray as well as CT scanning. A chiropractic radiologist read the films to determine if facet facings were sagittally, semi-sagittally or coronally oriented on both CT and plain X-ray study. CT was accepted as the most accurate method to determine the true facet orientation, and plain X-ray interpretation of facet orientation was compared to the CT reading. There was a statistically significant relationship in diagnosing tropism between plain film X-ray and CT readings, with a predictive accuracy that ranged from 58-84% across the three segmental levels. However, the exact concordance of plain film X-ray and CT readings for right and left facet facings was very low. This raises the question of how the profession defines diagnostic accuracy.