Abstract:

Objective　To investigate the relationship between the facet tropism and the severity of degeneration of facet joints in degenerative lumbar spondylolisthesis(DLS), and explore its clinical significance. Methods　60 from 102 patients with DLS，treated in our hospital during May 2004 to August 2009，were randomly selected. 60 age- and sex- matched people free from spinal diseases were selected as control group from a group of 300 coming for routine physical examination. The facet angles at L3/4, L4/5 and L5/S1 level on axial MRI were measured，then facet tropism was calculated. The severity of degeneration of facet joints was evaluated by using a 4-grade scale. The relativity analysis of obtained parameters was performed.　Results　The left facet joints were sagittally oriented than the right facet joints, but the difference was statistically significant only at L3/4 (P=0.003) and L4/5 (P=0.000) in the DLS group. The facet tropism at L4/5 was more significant than that at L3/4 and L5/S1 in both groups. The facet tropism, the degeneration of facet joints in the DLS group were more significant than those in the control group. The facet tropism increased with the severity of degeneration of facet joints in both groups.　Conclusions　(1)Facet tropism is quite common in lower lumbar level. (2)There is a positive correlation between the facet tropism and the severity of degeneration of facet joints. (3)Facet tropism is not simply due to secondary osteoarthritic remodeling but also part of the pre-existing morphologic abnormality. (4)The facet tropism increases the risk in the development of DLS. The facet tropism and the severity of degeneration of facet joints have an important etiologic meaning in the occurrence of DLS.

Key words: Lumbar, Degenerative lumbar spondylolisthesis, Dacet joints, Facet tropism