Investigating the mechanical effect of the sagittal angle of the cervical facet joint on the cervical intervertebral disc.

Background: Facet tropism is defined as the asymmetry between the left and right facet joints relative to the sagittal plane. Published clinical studies have found that facet tropism is associated with cervical disc herniation. However, the relationship between the facet orientation and the side of cervical disc herniation remains controversial. Therefore, this study used the finite-element technique to investigate the biomechanical effects of the sagittal angle of the cervical facet joints on the cervical intervertebral disc. Objective: The biomechanical effects of the sagittal angle of the cervical facet joint on the cervical disc and facet joint were investigated using the finite-element technique. Methods: The finite-element model was constructed using computed tomography scans of a 26-year-old female volunteer. First, a cervical model was constructed from C3 to C7. The model was verified using data from previously published studies. Second, the facet orientation at the C5-C6 level was altered to simulate different sagittal angles of cervical facet joints. Five models, F70, F80, F90, F100, and F110, were simulated with different facet joint orientations (70°, 80°, 90°, 100°, and 110° facet joint angles at the left side, respectively, and 90° facet joint angles at the right side) at the C5-C6 facet joints. In each model, annular fibres stress and facet cartilage pressure were studied under six pure moments and two combined moments. Results: Comparing the stress of the annulus fibres in flexion combined with right axial rotation and in flexion combined with left axial rotation in the same model, no difference in the maximum stress of the annulus fibres was noted between these two different moments in the F90 model, whereas differences of 12.80%, 8.84%, 14.95% and 33.32% were noted in the F70, F80, F100 and F110 models, respectively. The same trend was observed when comparing the maximum stress of the annulus fibres in each model during left and right axial rotation. No differences in annular fibres stress and facet cartilage pressure were noted among the five models in flexion, extension, lateral bending, left axial rotation, and flexion combined with left axial rotation in this study. However, compared with the F70 model in flexion combined with right axial rotation, the annulus fibres stress of the F80, F90, F100, and F110 models increased by 5.53%, 13.03%, 35.04%, and 72.94%, respectively, and the pressure of the left facet joint of these models decreased by 5.65%, 12.10%, 18.41%, and 25.74%, respectively. The same trend was observed in the right axial moment. Conclusion: Facet tropism leads to unbalanced stress distribution on the annulus fibres at the cervical intervertebral disc. The greater the sagittal angle of the facet joint, the greater the annular fibres stress on this side. We hypothesised that the side with the larger sagittal angle of the facet joint exhibits a greater risk of disc herniation.

[Risk factors of hidden blood loss in percutaneous vertebral augmentation].

OBJECTIVE: To explore the risk factors of hidden blood loss in osteoporosis vertebral compression fractures during percutaneous vertebral augmentation. METHODS: From October 2018 to December 2019, 360 patients with osteoporosis vertebral compression fractures who received percutaneous vertebral augmentation were enrolled in this study. The factors analyzed included gender, age, surgical methods, disease course, height, weight, the operative segment, bone mineral density, amount of bone cement, operative time, percentage of height loss, percentage of vertebral height restoration, cement leakage, blood clotting function, preoperative and postoperative hemoglobin and hematocrit and other internal diseases. Total blood loss was calculated by Gross's formula, influential factors of the hidden blood loss were further analyzed by t-test, multivariate linear regression and one-way ANOVA analysis. RESULTS: Surgical methods, the operative segment, disease course, cement leakage, preoperative hemoglobin, cement leakage via the basivertebral and segmental vein were significantly correlated with hidden blood loss(P<0.05). CONCLUSION: Patients with percutaneous kyphoplasty, two-level and multi-level surgery, the course of the disease beyond 6 weeks, cement leakage via the basivertebral and segmental vein, and lower preoperative hemoglobin had more perioperative hidden blood loss.

[Risk factors for multiple level osteoporosis vertebral compression fractures].

OBJECTIVE: To identify risk factors associated with patients suffered multiple level osteoporosis vertebral compression fractures(OVCFs). METHODS: From March 2011 to March 2015, 199 patients suffered osteoporotic were classified into multiple level OVCFs group and single level OVCF group. Multivariate logistic regression analysis were performed to identify risks factors associated with multiple level OVCFs. RESULTS: All the patients underwent OVCF, including 71 multiple level OVCFs and 128 single level OVCF. There were no differences in the age, gender, BMI, hypertension and diabetes between two groups. While multiple level OVCFs were associated with spinal deformity index SDI[(2<=SDI<4, OR=2.587, 95% CI(1.148, 5.828);SDI>=-4, OR=7.775, 95% CI(3.272, 18.478)], BMD[(T<-4.5SD, OR=2.608, 95% CI(1.038, 6.551)]. CONCLUSIONS: SDI and BMD might be the risk factors for multiple level OVCFs.