Evaluation of facet joints and segmental motion in patients with different grades of L5/S1 intervertebral disc degeneration: a kinematic MRI study

Exploring the Influence of Facet Orientation and Tropism on Neutral Zone Properties

Lumbar spine pathologies have been linked independently to both neutral zone (NZ) properties and facet joint anatomical characteristics; however, the effect of facet joint orientation (FO) and tropism (FT) on NZ properties remains unclear. The aim of the present study was to investigate how axial plane FO and FT relate to NZ range and stiffness in the human lumbar spine and porcine cervical spine. Seven human lumbar functional spine units (FSUs) and 94 porcine cervical FSUs were examined. FO and FT were measured, and in vitro mechanical testing was used to determine anterior-posterior (AP) and flexion-extension (FE) NZ range and stiffness. FO and FT were found to have no significant relationship with AP and FE NZ range. Increases in FT were associated with greater FE and AP NZ stiffness in human FSUs, with no FT-NZ stiffness relationship observed in porcine specimens. A significant relationship (p < 0.001) between FO and FE NZ stiffness was observed for both porcine and human FSUs, with a more sagittal orientation of the facet joints being associated with decreased FE NZ stiffness. Given the link between NZ stiffness and pathological states of the lumbar spine, further research is warranted to determine the practical significance of the observed facet joint anatomical characteristic-NZ property relationship.

Three Stages on Magnetic Resonance Imaging of Lumbar Degenerative Spine

PURPOSES

To propose a new lumbar degenerative staging system using the current radiological classification system.

METHODS

A cross-sectional analysis of retrospective databases between January 2018 and December 2022 was performed. Total of 410 patients for Modic changes, paravertebral muscle fat infiltration, disc degeneration, articular process degeneration, vertebral endplate degeneration and other structures, and disc displacement, Spondylolisthesis, and stenosis, and grouped patients according to stage were assessed. Visual analog scale, Japanese Orthopaedic Association, and Oswestry Disability Index scores were used to assess low back pain strength, neurological function, and quality of life, respectively.

RESULTS

The lumbar degeneration staging system consists of 8 variables, which can be divided into 3 steps: early, middle and late, and the correlation between each variable is strong (P < 0.05). The later the staging, the worse the Japanese Orthopaedic Association, visual analog scale, and Oswestry Disability Index scores.

CONCLUSIONS

Patients with later stages have worse clinical scores. This staging system recommends a uniform classification to assess lumbar degeneration.

Influence of the facet joint angle on facet joint degeneration following pedicle screw fixation without fusion in thoracolumbar fractures

BACKGROUND

Posterior approach pedicle screw fixation without fusion is widely used in the treatment of neurologically intact type A3 thoracolumbar fractures.

OBJECTIVE

To analyze the influence of the facet joint (FJ) angle on FJ degeneration following posterior approach pedicle screw fixation without fusion in neurologically intact type A3 thoracolumbar fractures.

METHODS

Fifty-eight patients who underwent pedicle screw fixation via the traditional posterior approach (n= 28) or the Wiltse approach (n= 30) were enrolled. A CT scan was performed before fixation and before fixation removal (Within 1.5 to 2 years after fixation) to evaluate the FJs parameters, including FJ inclination (FJI), FJ tropism (FJT), FJ violation, and FJ degeneration grade (FJDG), of three fixed segments and the adjacent segment below the fixed segments.

RESULTS

There was no significant difference in FJ violation rate, FJDG deterioration, or FJ angle between the two groups (P> 0.05). FJDG deterioration showed a weak positive correlation with FJI and FJT before fixation, and the angular change in FJI (P< 0.05); and FJT before fixation and the angular change in FJI were risk factors for FJDG deterioration (P< 0.01).

CONCLUSION

The Wiltse approach did not increase the rate of FJDG deterioration and FJs angle changes. However, the FJT before fixation and the angular change in FJI were risk factors for FJDG deterioration.

3D kinematic characteristics of lumbar facet joints in sitting position

BACKGROUND

Recognizing the kinematic characteristics of lumbar facet joints is important for the prevention and treatment of lumbar degenerative diseases. Previous studies have been conducted in either the supine or standing position, and there are no measurements regarding the kinematic characteristics of the lumbar facet joints while sitting. The aim of this study was to measure and analyze lumbar facet joint motion characteristics while sitting.

METHODS

Ten subjects (5 males and 5 females) performed the movements of flexion-extension, left bending-right bending, and left rotation-right rotation in a sitting position. Dual Fluoroscopic Image System and computed tomography technique were used to measure the displacement and rotation angle of the lumbar facet joints of the subjects for analysis. The movement characteristics of L3-S1 were measured.

RESULTS

When the subjects were in sitting position, the lumbar vertebra mainly changed in Z-axis and α, β angle when they performed flexion-extension activities. The displacement of the left facet joint was 4.65 ± 1.99 mm at L3-4, 1.89 ± 2.99 mm at L4-5, and 0.80 ± 2.27 mm at L5-S1 in the Z-axis, and the displacement of the right facet joint was 3.20 ± 2.61 mm at L3-4, 1.71 ± 3.00 mm at L4-5, and 0.31 ± 1.69 mm at L5-S1 in the Z-axis. The rotation in the α angle was 6.00 ± 4.49° at L3-4, 3.51 ± 5.24° at L4-5, and 0.97 ± 4.13° at L5-S1, which was significant different. The rotation in the β angle was 2.30 ± 2.94°at L3-4, 0.16 ± 2.06° at L4-5, and 0.35 ± 1.74°at L5-S1, which was significant different. When the lumbar spine performed the activity of left bending-right bending, there were changes in rotation mainly in the Z-axis and β angle. The displacement of left facet joint in the Z-axis was 1.34 ± 2.84 mm at L3-4, 2.11 ± 0.88 mm at L4-5, and 0.72 ± 0.81 mm at L5-S1; the rotation in the β angle was 5.66 ± 2.70°at L3-4, 7.89 ± 2.59° at L4-5, and 1.28 ± 2.07° at L5-S1; when the lumbar spine performed the activity of left rotation-right rotation, there were changes in the β angle. The rotation of β angle was 4.09 ± 2.86° at L3-4, 2.14 ± 3.38° at L4-5, and 0.63 ± 1.85° at L5-S1.

CONCLUSION

The lumbar facet joint motion in sitting position is different in each mode of motion. The horizontal displacement and rotation are predominant during flexion and extension activities, while there are different rotation in bending and rotation. The study shows the coupled motion of the lumbar facet joints while sitting, providing a new perspective on the kinematics of the lumbar spine and the etiology of lumbar degenerative diseases.