3D orientation and kinematic characteristics of zygapophyseal joints while sitting

Abstract

Background: Orientation of the lumbar facet joints (FJs) in the transverse plane is associated with degenerative lumbar spine disease. However, there is a lack of measurements of the sagittal and coronal facet angles, and the effect of 3D facet angles on joint motion in the sitting position is unknown. The present study was to investigate the 3D orientation and in vivo motion characteristics of the FJ in the sitting position.

Methods: Dual fluoroscopic imaging system and computed tomography (CT) were used to determine the 3D orientation and kinematic characteristics of FJs. L3-S1 segments were studied in 10 asymptomatic participants (5 male and 5 female, age: 25-35 years, body mass index: 22.4±1.8). Angles of the facet in the sagittal, coronal, and axial planes, and the range of motion of the FJs in seated flexion and extension movements were measured.

Results: The difference in sagittal facet angles between the 2 sides of the L3-S1 facet joints was not significant. The superior coronal facet angle on the left side of L5 was significantly smaller than that on the right side by 6.4° (P=0.01). The inferior transverse facet angle on the left side of L5 was greater than that on the right side by 7.1; the results were not statistically significantly different. In the sitting position, the range of motion of the left and right sides of L5-S1 differed significantly, with the right side being 5.5° (P=0.004) and 11.7° (P=0.026) greater than the left side in the sagittal and coronal planes, respectively. There was a correlation between mobility and the 3D orientation angle of the FJs in each segment.

Conclusions: Quantification of the 3D orientation of the lumbar spine FJs provides new perspectives to study the kinematics of the lumbar spine and the etiology of lumbar degenerative diseases. In sitting flexion and extension movements, there is a significant difference in the left-right lateral mobility of the FJs of the L5-S1 segments. With the exception of the transverse facet angle of the lumbar spine FJs, the sagittal and coronal facet angles also have an effect on lumbar spine mobility.

Keywords: 3D orientation; Zygapophyseal joint; facet tropism (FT); sitting.

Figure 1

3D reconstruction of L3-S1 segments based on computed tomography using MIMICS (Materialise’s interactive medical image control system) software. Different colors of the lumbar vertebrae represent different lumbar segments.

Figure 2

Experimental setup of the dual fluoroscopic imaging system. Participant subject sits in a height-adjustable seat, maintains body stability, and performs maximal forward flexion (A) and backward extension (B) movements.

Figure 3

Each 3D vertebral model was separately translated and rotated until their contours matched the corresponding vertebral bony outline captured on the 2 fluoroscopic images.

Figure 4

Establishment of the superior (A) and inferior (B) articular surface coordinate system. Four reference points are selected at the uppermost, lowermost, innermost, and outermost sides of the facet joints. Center of mass of the articular surface, defined as the origin to establish the Cartesian coordinate system, was selected through the area formed by the 4 reference points. X, Y, Z represents X axis, Y axis, Z axis of Cartesian coordinate system, respectively.

Figure 5

Definition of facet joint 3D orientation. (A) Sagittal facet angle (α), (B) coronal facet angle (β), (C) transverse facet angle (γ). α_S and β_S, α_I, and β_I indicate the superior and inferior articular surface angles, respectively.

Figure 6

With the superior articular surface as a reference, the range of rotation of the inferior articular surface was measured in the seated position. RX, rotation along the X-axis; RY, rotation along the Y-axis; RZ, rotation along the Z-axis. X, Y, Z represents X axis, Y axis, Z axis of Cartesian coordinate system, respectively.

Figure 7

The range of rotation of the L3-S1 facet joint in F-E, RB-LB, and LT-RT, respectively (A,D,G). The overall flexion-extension motion was further divided into two subgroups of neutral-anterior flexion and neutral-posterior extension. (B,E,H) and (C,F,I) are the ranges of rotation of the FJ in F-E, RB-LB, and LT-RT in each segment in the neutral-anterior flexion and neutral-posterior extension motion, respectively. *, P<0.05. The unit of all the Y-axis of the figures were degree. F-E, flexion-extension; RB-LB, left-right lateral bending; LT-RT, left-right rotation.

Figure 8

Bilateral facet angles of L3-S1 measured in our study compared with those of Chowdhury et al. (12). L3I, L4I, L5I, and L4S, L5S, and S S represent the inferior and superior articular facets of each segment, respectively. The unit of all the Y-axis of the figures were degree.