Fig. 1

Measurement technique of lumbar instability [12]. Angulation: Two straight lines are draw along the inferior endplate of the upper vertebra and the superior endplate of the lower vertebra. The intersection of these two lines is angulation in flexion (Ɵ⁻) and in extension (Ɵ⁺). The difference of intervertebral angles between Ɵ⁻ and Ɵ⁺ is amount of rotational instability. Translation: The straight line is drawn bisect the angulation in flexion (Ɵ⁻) and in extension (Ɵ⁺). The difference between the two distances from flexion (A) and extension (B) is amount of translation