A Possible Correlation between Facet Orientation and Development of Degenerative Cervical Spinal Stenosis

Background Previous studies have demonstrated the relationship between sagittal facet orientation and cervical degenerative spondylolisthesis. However, the associations between facet orientation and cervical spinal stenosis (CSS) have rarely been studied. Methods One hundred and twenty patients with CSS (CSS group) and 120 healthy participants (control group) were consecutively enrolled. The cervical facet angles and anteroposterior diameter (A-P diameter) of spinal canal at each subaxial cervical levels were measured using axial magnetic resonance imaging. The intersection angle of the midsagittal line of the vertebra to the facet line represents the orientation of the facet joint. Results The facet angles on the right side at C2- C3 and C3-C4 in CSS group and at C2- C3 in control group had significantly higher values than those of the other sides. Besides, the facet angles and A-P diameter of spinal canal in CSS group were significantly smaller than those in control group at all levels (p < 0.05). Conclusions Our study demonstrated that patients with CSS have smaller axial cervical facet joint angles compared to the healthy individuals. Further studies are needed to elicit the specific underlying mechanism between sagittalization of the cervical facet joints and the pathology of CSS.

The Correlation Between Facet Joint Parameters and the Location of Lumbar Disc Herniation in the Young Population

Background: Facet joint parameters have been discussed as substantial factors in the development of LDH. However, the correlation between facet joint parameters and the location of LDH in the corresponding segment is still unclear. The objective of this study was to demonstrate a clearly relationship between facet orientation (FO), facet tropism (FT) and lumbar disc herniation (LDH) in young individuals.Methods: Between June 2017 and December 2019, 529 patients having single-level LDH (L4-5 or L5-S1) between 18 and 35 years old with a less than 2 years clinical history were included. Another 122 age-matched patients with no LDH were enrolled as the control group (N-LDH group). Based on the location of herniation, cases in LDH group were divided into three groups (LDHL, LDHR, and LDHM). We investigated the correlation between facet joint parameters and the location of LDH.Results: The FOA in L4-5 and L5-S1 level were significantly lower while FT were higher in LDH group than N-LDH group respectively. In terms of the correlation between the facet joint parameters and the location of LDH, the level of LDH, the FOL, FOR, and FT were significantly varied among the three groups. There is a significant association between the different location of LDH and different FO of bilateral facet joints in L4-5 while not in L5-S1 level.Conclusion: The facet joint parameters abnormality have an significant association with the development of LDH. Young individuals with higher FT and/or lower FO should be paid more attention to preventing the occurrence of LDH. There was more location of IVD herniated on the ipsilateral location with lower FO of facet joint when FT existed in L4-5 level.

Experimental and model-based investigation of the links between snow bidirectional reflectance and snow microstructure

Snow stands out from materials at the Earth’s surface owing to its unique optical properties. Snow optical properties are sensitive to the snow microstructure, triggering potent climate feedbacks. The impacts of snow microstructure on its optical properties such as reflectance are, to date, only partially understood. However, precise modelling of snow reflectance, particularly bidirectional reflectance, are required in many problems, e.g. to correctly process satellite data over snow-covered areas. This study presents a dataset that combines bidirectional reflectance measurements over 500–2500 nm and the X-ray tomography of the snow microstructure for three snow samples of two different morphological types. The dataset is used to evaluate the stereological approach from Malinka (2014) that relates snow optical properties to the chord length distribution in the snow microstructure. The mean chord length and specific surface area (SSA) retrieved with this approach from the albedo spectrum and those measured by the X-ray tomography are in excellent agreement. The analysis of the 3D images has shown that the random chords of the ice phase obey the gamma distribution with the shape parameter m taking the value approximately equal to or a little greater than 2. For weak and intermediate absorption (high and medium albedo), the simulated bidirectional reflectances reproduce the measured ones accurately but tend to slightly overestimate the anisotropy of the radiation. For such absorptions the use of the exponential law for the ice chord length distribution instead of the one measured with the X-ray tomography does not affect the simulated reflectance. In contrast, under high absorption (albedo of a few percent), snow microstructure and especially facet orientation at the surface play a significant role in the reflectance, particularly at oblique viewing and incidence.

Are Facet Orientation and Tropism Risk Factors for Cervical Spondylotic Radiculopathy? A Retrospective Study in a Chinese Population

Background Facet parameters, such as facet orientation (FO) and tropism (FT) are thought to be predisposing factors for pathological changes in the lumbar spine. This study aimed to explore the association between facet parameters and cervical spondylotic radiculopathy (CSR) on 3-dimentional views. Methods A total of 226 patients with single-level CSR and 182 normal control participants were included. FO, FT and the incidence of FT (defined as FT ≥ 7) based on reconstructed CT images were measured. Univariate and multiple logistic regression analysis were used to investigate the association between facet joint parameters and the incidence of CSR. The Pearson Chi-square test was used to find out the relationship between the side of herniation and facet joint parameters in CSR patients. Results Axial FT of CSR group was significantly larger compared to control group at each spinal level, while sagittal except C5/6 and coronal FT shown not. The differences of incidence of axial FT at all levels between groups were statistically significant, as well as incidence of sagittal FT at C4/5 and C5/6. Incidence of axial FT with respect to all levels was significantly associated with CSR, and incidence of sagittal FT only at C4/5 and C5/6 was associated with CSR. The proportion between the left and right side of greater FO was significantly different on axial view. Conclusion Axial and sagittal FT but not FO were associated with CSR, and axial FT might exert more dominant function on the development of CSR. Moreover, CSR might be more vulnerable to more severe axial FT, which should be paid more attention. The side of herniation might prefer the side of greater axial FO.

Facet Violation With Percutaneous Pedicle Screw Placement: Impact of 3D Navigation and Facet Orientation

Background: The gold standard for percutaneous pedicle screw placement is 2-dimensional (2D) fluoroscopy. Data are sparse on the accuracy of 3-dimensional (3D) navigation percutaneous screw placement in minimally invasive spine procedures. Objective: We sought to compare a single surgeon’s percutaneous pedicle screw placement accuracy using 2D fluoroscopy versus 3D navigation, as well as to investigate the effect of facet orientation on facet violation when using 2D fluoroscopy. Methods: We conducted a retrospective radiographic study of consecutive cohort of patients who underwent percutaneous lumbar instrumentation using either 2D fluoroscopy or 3D navigation. All procedures were performed by a single surgeon at 2 academic institutions between 2011 and 2018. Radiographic measurement of screw accuracy was assessed using a postoperative computed tomographic scan. The primary outcome was facet violation, and secondary outcomes were endplate/tip breaches, the Gertzbein-Robbins classification for cortical breaches, and the Simplified Screw Accuracy grade. Statistical comparisons were made between screws placed using 2D fluoroscopy versus 3D navigation. Axial facet angles were also measured to correlate with facet violation rates. Results: In the 138 patients included, 376 screws were placed with fluoroscopy and 193 with navigation. Superior (unfused) level facet violation was higher with 2D fluoroscopy than with 3D navigation (9% vs 0.5%), which comprises the main cause for poor screw placement. Axial facet angles exceeding 45° at L4 and 60° at L5 were correlated with facet violations. Conclusion: This retrospective study found that 3D navigation is associated with lower facet violation rates in percutaneous lumbar pedicle screw placement when compared with 2D fluoroscopy. These findings suggest that 3D navigation may be of particular value when facet joints are coronally oriented.

Degenerative spondylolisthesis L4/ L5 radiological parameters in patient with L5 Sacralization

Background: L5 Sacralization is normal variation in lumbar anatomy, but many authors believed this condition because of concentration of pressure in L4/ L5 level can speed up degenerative process (disk degeneration or listhesis…). However no study was compare spondylolisthesis radiological parameters in patient with and without sacralization of L5, our purpose is evaluation of radiological parameters in spondylolistesisL4/L5 in patient with and without L5 sacralization. Methods: In cross sectional study we divided 78 patient with spondylolisthesis of L4/L5 in two group with (n=24) and without (n=54) L5 sacralization and evaluated facet osteoarthritis, degree of listhesis (%), disk degeneration, and facet orientation in two group and result was compared, Results: There was no significant difference in the degree of anterior slippage of L4 on L5 (17.02±6.21 versus 16.65±4.87, p=0.809), facet orientation (54.99±12.18 versus 56.23±4.35, p=0.642), facet osteoarthritis (3.43±0.59 versus 3.53±0.37, p=0.527), or disc degeneration (4.50±0.51 versus 4.35±0.61, p=0.340) between the two groups Conclusion: There is no significant relation between radiological parameters in two group and we thought influence of L5 sacralization on degenerative process of L4/L5 less significant than previously expected, but future study with large number of patient need to clarify the role of fixed L5 on degenerative process in lumbar spine.

Experimental and model-based investigation of the links between snow bidirectional reflectance and snow microstructure

Snow stands out from materials at the Earth's surface owing to its unique optical properties. Snow optical properties are sensitive to the snow microstructure, triggering potent climate feedbacks. The impacts of snow microstructure on its optical properties such as reflectance are, to date, only partially understood. However, precise modelling of snow reflectance, particularly bidirectional one, are required in many problems, e.g. to process correctly satellite data over snow-covered areas. This study presents a dataset that combines bidirectional reflectance measurements over 500–2500 nm and the X-ray tomography of the snow microstructure for three snow samples of two different morphological types. The dataset is used to evaluate the stereological approach from Malinka (2014) that relates snow optical properties to the chord length distribution in the snow microstructure. The mean chord length and SSA retrieved with this approach from the albedo spectrum and those measured by the X-ray tomography are in excellent agreement. The analysis of the 3D images has shown that the random chords of the ice phase obey the gamma distribution with the shape parameter m taking the value approximately equal or a little greater than 2. For weak and intermediate absorption (high and medium albedo), the simulated bidirectional reflectances reproduce the measured ones accurately but tend to slightly overestimate the anisotropy of the radiation. For such absorptions the use of the exponential law for the ice chord length distribution instead of the one measured with the X-ray tomography does not affect the simulated reflectance. In contrast, under high absorption (albedo of a few percent), snow microstructure and especially facet orientation at the surface, plays a significant role for the reflectance, particularly at oblique viewing and incidence.