Facet Joint Experiment

Introduction

AS the only synovial joint of the spine[1], facet joint plays a significant role in maintaining the stability of the spine for resistance to shear and rotational forces[2] and bearing 33% of the dynamic load and 35% of the static load of the spine as biomechanical studies have pointed out[3] .Therefore, guiding and restricting the motion of the spine is the main function of facet joint. Some features of facet joints such as sagittal facet joint angles（FJA）and tropism (the asymmetries of facet joint) have been reported in previous literature being associated with the occurrence of degenerative lumbar spondylolisthesis(DLS) [4,5]、degenerative disc disease(DDD) [6,7]、facet joint osteoarthritis[8]

So far, many articles have pointed

According to Grobler etl[5], selected a cut level of CT through the superior vertebral end-plate of the lower vertebra and parallel to the inferior vertebral end-plate of the superior vertebra , then three lines (line a,b,c)were marked ,among them, line a is the tangent through trailing edge of the vertebral body and line a,b through anteromedial and posterolateral point of the corresponding facet joint respectively. Angle ab and angle ac(Figure 1) as the corresponding facet joint angle were recoded.

Tropism

The definition of tropism is first proposed by Brailsford JF[12] .It refers to the asymmetry of bilateral facet joint, the absolute value of the angle difference of bilateral articular facet joint as the tropism quantitative value

Pfirrmann grading Intervertebral disc was classified into gradeⅠ- Ⅴ (图2) by Pfirrmann et al [13] based on image of sagittal MRI T2-weighted images（图3）

The angle of the facet joint was measured by two independent individuals. If the difference between the two data does not exceed 2 degrees, the average of the two measurements is taken as the angle of the corresponding facet joint. If, on the contrary, the two measured values differ by more than 2 degrees, repeat the measurement until the standard is

Etiology of Spondylolisthesis: Assessment of the Role Played by Lumbar Facet Joint Morphology[J]. Spine, 1993, 18(1): 80-91.

[6]Karacan I, Aydin T, Sahin Z, et al. Facet angles in lumbar disc herniation: their relation to anthropometric features[J]. Spine, 2004, 29(10): 1132-1136.

[7]Witchate Pichaisak M D, Chotiyarnwong C, Pojchong Chotiyarnwong M D. Facet Joint Orientation and Tropism in Lumbar Degenerative Disc Disease and Spondylolisthesis[J]. J Med Assoc Thai, 2015, 98(4): 373-9.

[8] Linov L, Klindukhov A, Li L, et al. Lumbar facet joint orientation and osteoarthritis: a cross-sectional study[J]. Journal of back and musculoskeletal rehabilitation, 2013, 26(4): 421-426.

[9]DeVine J G, Schenk-Kisser J M, Skelly A C. Risk factors for degenerative spondylolisthesis: a systematic review[J]. Evidence-based spine-care journal, 2012, 3(02): 25-34.

[10]Schleich C, Müller-Lutz A, Blum K, et al. Facet tropism and facet joint orientation: risk factors for the development of early biochemical alterations of lumbar intervertebral discs[J]. Osteoarthritis and Cartilage, 2016.

[11]Kong M H, He W, Tsai Y D, et al. Relationship of facet tropism with degeneration and stability of functional spinal unit[J]. Yonsei medical journal, 2009, 50(5):