Influence of Sagittal Lumbopelvic Morphotypes on the Range of Motion of Human Lumbar Spine: An In Vitro Cadaveric Study

Background: Although spinopelvic radiographs analysis is the standard for a pathological diagnosis, it cannot explain the activities of the spine in daily life. This study investigates the correlation between sagittal parameters and spinal range of motion (ROM) to find morphological parameters with kinetic implications. Methods: Six L1–S1 human lumbar specimens were tested with a robotic testing device. Eight sagittal parameters were measured in the three-dimensional model. Pure moments were applied to simulate the physiological activities in daily life. Results: The correlation between sagittal parameters and the ROM was moderate in flexion and extension, but weak in lateral bending and rotation. In flexion–extension, the ROM was moderately correlated with SS and LL. SS was the only parameter correlated with the ROM under all loading conditions. The intervertebral rotation distribution showed that the maximal ROM frequently occurred at the L5–S1 segment. The minimal ROM often appeared near the apex point of the lumbar. Conclusion: Sagittal alignment mainly affected the ROM of the lumbar in flexion and extension. SS and apex may have had kinetic significance. Our findings suggest that the effect of sagittal parameters on lumbar ROM is important information for assessing spinal activity.