Figure 5.

Mean disc compression–distraction deformation in the anterior annulus (A), nucleus (B) and posterior annulus (C) during flexion–extension in asymptomatic control subjects (n = 20). Disc compression-distraction, expressed as a percentage of disc height in the static neutral position, is plotted on the vertical axis. Intervertebral flexion–extension angle, normalized to the static neutral position, is plotted on the horizontal axis. Error bars indicate inter-subject variability (i.e., 95% confidence interval at each disc level) and averaged 3.9% across all disc levels, disc regions and intervertebral flexion–extension angles. Note that statistical tests for differences among disc levels were performed using within-subject analysis.