Is lumbar facet joint tropism developmental or secondary to degeneration? An international, large-scale multicenter study by the AOSpine Asia Pacific Research Collaboration Consortium

Abstract

BackgroundFacet joint tropism is asymmetry in orientation of the bilateral facets. Some studies have shown that tropism may increase the risk of disc degeneration and herniations, as well as degenerative spondylolisthesis (DS). It remains controversial whether tropism is a pre-existing developmental phenomena or secondary to progressive remodeling of the joint structure due to degenerative changes. As such, the following study addressed the occurrence of tropism of the lower lumbar spine (i.e. L3–S1) in a degenerative spondylolisthesis patient model.MethodsAn international, multi-center cross-sectional study that consisted of 349 patients with single level DS recruited from 33 spine institutes in the Asia Pacific region was performed. Axial MRI/CT from L3–S1 were utilized to assess left and right facet joint sagittal angulation in relation to the coronal plane. The angulation difference between the bilateral facets was obtained. Tropism was noted if there was 8° or greater angulation difference between the facet joints. Tropism was noted at levels of DS and compared to immediate adjacent and distal non-DS levels, if applicable, to the index level. Age, sex-type and body mass index (BMI) were also noted and assessed in relation to tropism.ResultsOf the 349 subjects, there were 63.0 % females, the mean age was 61.8 years and the mean BMI was 25.6 kg/m2. Overall, 9.7, 76.5 and 13.8 % had L3–L4, L4–L5 and L5–S1 DS, respectively. Tropism was present in 47.1, 50.6 and 31.3 % of L3–L4, L4–L5 and L5–S1 of levels with DS, respectively. Tropism involved 33.3 to 50.0 % and 33.3 to 58.8 % of the immediate adjacent and most distal non-DS levels from the DS level, respectively. Patient demographics were not found to be significantly related to tropism at any level (p > 0.05).ConclusionsTo the authors’ knowledge, this is one of the largest studies conducted, in particular in an Asian population, addressing facet joint tropism. Although levels with DS were noted to have tropism, immediate adjacent and distal levels with no DS also exhibited tropism, and were not related to age and other patient demographics. This study suggests that facet joint tropism or perhaps subsets of facet joint orientation may have a pre-disposed orientation that may be developmental in origin or a combination with secondary changes due to degenerative/slip effects. The presence of tropism should be noted in all imaging assessments, which may have implications in treatment decision-making, prognostication of disease progression, and predictive modeling. Having a deeper understanding of such concepts may further elaborate on the precision phenotyping of the facets and their role in more personalized spine care. Additional prospective and controlled studies are needed to further validate the findings.

Multidimensional vertebral endplate defects are associated with disc degeneration, modic changes, facet joint abnormalities, and pain

“…The facet joints were found to be increasingly irregular, flat and significantly narrowed as the dimensions of the endplate defects increased. Facet joints are the point of contact between adjacent neural arches of the vertebral bodies and small changes in postural angle can lead to high stress concentration . It may be possible that endplate damage and resulting uneven stress distribution and disc degeneration cause much of the compressive stress to pass through the neural arch affecting the facet joints .…”

The association of lumbar curve magnitude and spinal range of motion in adolescent idiopathic scoliosis: a cross-sectional study

“…This finding can be explained by the effect of changes in the motion axis with regards to the facet joint and the disc [36, 37]. Curve progression affects the position of the vertebrae and disc in space and causes truncal imbalance with truncal shift or listing.…”

A case of marked bilateral asymmetry in the sacral alae of the Neandertal specimen Regourdou 1 (Périgord, France)

“…Normal variation of the facet angle is approximately between 30 and 70° (Mahato, ; Noren et al, ), and facet tropism occurs when one of the facets is oriented more mediolaterally. It is not clear how facet tropism originates (Samartzis et al, ), but it is a probable risk factor for degenerative diseases such as spondylolisthesis and disc herniation (Dai, ; Kim et al, ; Lai et al, in press; Noren et al, ; Schleich et al, ). Coronal orientation of one facet causes increased torsional stress because of abnormal rotation of the lumbar spine (Noren et al, ).…”