The effect of lumbar flexion and extension on disc contour abnormality measured quantitatively on magnetic resonance imaging

Study Design. Experimental study with subjects as their own control. Objective. To determine if lumbar disc contour abnormality dimensions, measured quantitatively, differ in flexed, neutral or extended positions. Summary of Background Data. MRIs obtained lying supine are used to determine the degree of lumbar disc contour abnormality (bulging or herniation). Variations in positioning are suspected to influence this assessment. Methods. Lumbar MR images for 26 male volunteers (24-74 years of age), with or without low back pain, were obtained with the subjects lying in neutral, maximal flexion, and maximal extension positions allowable within a conventional 1.5T MR scanner. Quantitative measures of anterior and posterior disc contour abnormality were obtained for each position. Results. Statistically significant differences in disc angles were obtained between positions (2-5) for all levels. Posterior contour abnormality was significantly smaller in flexion and extension than in the neutral position (9.5%-30.1%). Posterior contour abnormality in extension was similar or smaller than in flexion. Anterior contour abnormality was significantly smaller in extension than flexion and smaller in the neutral position than flexion. Conclusion. Spine position should be standardized when assessing disc contour abnormality with MRI. The largest measured disc contour abnormalities when lying supine in a standard MR scanner are observed in the neutral position, as opposed to flexion or extension.