Experimental study on the orientation of lumbar facet joints induced by high stress in rabbits

English Keywords:Lumbar facet joints  Stress  Degeneration  Orientation  Rabbit

English Abstract:

  【Abstract】 Objectives: To investigate the orientation of lumbar facet joints induced by experimental stress in rabbits, and to explore the associated mechanism of these changes. Methods: Forty-two New Zealand white rabbits were randomly divided into 4 groups(A, B, C, D) which were assigned into different treatments. Group A received sham operation with intact lumbar spine structures. In group B, nucleus pulposus was aspirated to produce disc degeneration at L3/4 and L5/6. In group C, springs were put on the adjacent facets of L3/4 and L5/6 6 weeks later to stress the facet joints. Group D received the both treatments of group B and C. Lumbar spines were harvested after 4 months or 8 months respectively and then scanned by MicroCT. The morphology of facet joints was observed. Lumbar facet joint angles at level L3/4 and L5/6 were measured on the axial MicroCT images in group B, C, D, and the data were combined for analysis. The angles were measured at level L3/4, L4/5, L5/6 and L6/7 in group A, the data at 4 levels were combined. The angles measured were defined as midsagittal line through the disc and intersecting lines formed by connecting the two end points of each facet. The smaller the angle was, the more sagittally oriented the facet joint. Results: In each group, facet joints at the 8th month were more sagittally oriented than those at the 4th month(P＜0.05). Facet joint angles between group A and B or group C and D did not show significantly treatment-associated difference(P＞0.05). While facet joints in group D, which was loaded with additional stress on facet joints, were more sagittally oriented than those in group B(P＜0.05), and facet joints in group C were more sagittally oriented than those in group A(P＜0.05). Facet joints in group C and D, which sustained additional stress, presented with more degeneration than those in group B. Degeneration aggravated with time. While the structure of facet joints was clear in group A at two time points. Conclusions: High stress on facet joints induces lumbar facet joint degeneration in rabbits. A more sagittal orientation of facet joints is due to secondary remodeling of degenerative facet joints.