The Effect of Various Weight-bearing Activity on the Motion of the Lumbar Facet Joints in Vivo

Background: Lumbar facet joints (LFJ) are usually related to the pathogenesis of the spine, but the quantification of normal FJ motion is still limited to in vitro studies, animal models, and imaging analysis. Few people report the in vivo kinematics of facet joints. There has always been a debate about whether it can induce biomechanical changes in the motion pattern of the facet joints after weight-bearing, resulting in the degeneration of the facet joints and osteoarthritis.Methods: A total of 10 healthy volunteers, 5 males , and 5 females, aged 21≤39 years, with an average age of 32±5 years, were recruited. Using the combination of DFIS and CT, the sagittal images of L3-S1 segments scanned by CT were transformed into three-dimensional reconstruction models and then matched to the instantaneous images of lumbar spine motion taken by a double fluorescent X-ray system under different loads. To reproduce the instantaneous motion state of lumbar vertebrae in different positions (supine position, standing position, flexion-extension position, left-right bending, left-right rotation) under different loads(0kg,10kg), assisted by computer-related software, in vivo human LFJ 6-DOF kinematics were obtained.Result: In flexion and extension exercises: there is no statistical difference in the horizontal rotation angle (α, β, r) of each segment after weight-bearing. The coupling translations are significantly reduced in the left and right direction of the L34 segment (P<0.05). In the L45 segment, the articular process was significantly reduced in the anteroposterior direction (left P<0.05). In lateral bending: the main rotation axis rotation range was different after weight-bearing, L45 decreased (P=0.023), and L5S1 decreased significantly (P=0.021), there is no difference in the coupling rotation range, the coupling translations only decreases in the left and right direction of the L34 segment (P<0.05); in the rotation movement: the horizontal rotation angle of each segment after the load (α, β, r) There was no statistical difference. The coupling translation was only in the L5/S1 segment and decreased in the craniocaudal direction (P<0.05). In the three movements, the asymmetric movement of the left and right articular processes occurred in the L34 segment (P<0.05), and the maximum translations after weight-bearing were found at L5/S1.Conclusion: Increased weight-bearing will affect the motion pattern of lumbar facet joints. The asymmetric movement of the left and right sides of the L34 segment is related to the asymmetry of the facet. The increase in translation of L5/S1 after weight-bearing compared with other segments may be related to the anatomical structure of the facet joint morphology deviated to the coronal position and frontal plane. Through the analysis of the body motion data of the lumbar facet joints before and after the weight-bearing, the relationship with the lumbar spine-related diseases is obtained. And it can provide a reference for guiding healthy lifestyles, clinical surgical procedures, and new spinal implants.