Development and validation of a nomogram to predict the risk of residual low back pain after tubular microdiskectomy of lumbar disk herniation.

OBJECTIVE: Tubular microdiskectomy (tMD) is one of the most commonly used for treating lumbar disk herniation. However, there still patients still complain of persistent postoperative residual low back pain (rLBP) postoperatively. This study attempts to develop a nomogram to predict the risk of rLBP after tMD. METHODS: The patients were divided into non-rLBP (LBP VAS score < 2) and rLBP (LBP VAS score ≥ 2) group. The correlation between rLBP and these factors were analyzed by multivariate logistic analysis. Then, a nomogram prediction model of rLBP was developed based on the risk factors screened by multivariate analysis. The samples in the model are randomly divided into training and validation sets in a 7:3 ratio. The Receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA) were used to evaluate the diskrimination, calibration and clinical value of the model, respectively. RESULTS: A total of 14.3% (47/329) of patients have persistent rLBP. The multivariate analysis suggests that higher preoperative LBP visual analog scale (VAS) score, lower facet orientation (FO), grade 2-3 facet joint degeneration (FJD) and moderate-severe multifidus fat atrophy (MFA) are risk factors for postoperative rLBP. In the training and validation sets, the ROC curves, calibration curves, and DCAs suggested the good diskrimination, predictive accuracy between the predicted probability and actual probability, and clinical value of the model, respectively. CONCLUSION: This nomogram including preoperative LBP VAS score, FO, FJD and MFA can serve a promising prediction model, which will provide a reference for clinicians to predict the rLBP after tMD.

Sacralization may be associated with facet orientation and tropism but not degenerative changes of the lumbar vertebrae.

PURPOSE: In this retrospective study, we aimed to investigate the possible effects of transitional vertebra anatomy on facet joint tropism and orientation by evaluating lumbar magnetic resonance imaging (MRI) studies performed at our institution. MATERIAL AND METHODS: We included 84 patients with sacralization of the L5 vertebra and an equal number of patients with a radiology report within normal limits as the control group in our study. We compared facet tropism (FT) and orientation between both groups. RESULTS: In both the sacralization group and the control group, the facet orientation angle showed a significant increasing trend from the L1-L2 level to the L5-S1 level (p < 0.001). The orientation angle of the L5-S1 level was higher in the sacralization group compared to the control group (p < 0.01). In the evaluation of FJ orientation between the sacralization and control groups, we found that coronal orientation was significantly more frequent at the L5-S1 level in the sacralization group. When the 2 groups were compared with regard to tropism at each spinal level, the sacralization group had a significantly higher FT frequency at the L5-S1 level (p < 0.001). CONCLUSIONS: To our knowledge, this is the first study to evaluate the relationship between sacralization and facet joint tropism. However, there were no relationships between facet degeneration, disc degeneration/herniation, and sacralization. Our results indicate that, although patients with sacralization and controls had similar characteristics in most assessments, they demonstrated significant differences at the L5-S1 level in terms of orientation and tropism.

A case of marked bilateral asymmetry in the sacral alae of the Neandertal specimen Regourdou 1 (Périgord, France).

OBJECTIVES: A marked asymmetry was previously reported in the sacral alae and S1-L5 facets orientation of the Neandertal individual Regourdou 1. Here, we provide a detailed description and quantification of the morphology and degree of asymmetry of this sacrum. MATERIAL AND METHODS: Regourdou 1 was compared to a modern human sample composed of 24 females and 17 males, and to other Neandertal individuals. Both traditional and geometric morphometric analyses were used in order to quantify the degree of sacral asymmetry of Regourdou 1. RESULTS: The asymmetry of both sacral alae and facets orientation substantially exceeds directional and absolute asymmetry of the healthy modern sample. Regourdou 1 shows a considerably shorter right ala, which is absolutely and relatively outside of the modern and Neandertal variations. CONCLUSION: Regourdou 1 shows marked sacral asymmetry that probably originated in early ontogenetic development. An asymmetric sacrum reflects asymmetric load dissipation and could relate to other morphological abnormalities observed in the skeleton, especially the mild scoliosis of the spine and the asymmetry of the femoral diaphyses. Further investigation is necessary to elucidate the relationship between those morphologies as well as a potential impact on the life of the individual.

Association of facet tropism and orientation with lumbar disc herniation in young patients.

Facet tropism and orientation are thought to be associated with lumbar disc herniation (LDH), but the relationship is not well established. Moreover, the effect of facet joint on LDH has not been outlined in young patients. The objective of this study was to investigate the associations of facet joint tropism and orientation with LDH in young patients (18-35 years) by computed tomography (CT). Fifty-three patients with LDH and 129 with neither LDH nor low back pain (18-35 years) were included in this study. The facet joint angles were measured for each facet joint by CT as per the method described by Noren et al. We defined facet tropism as a bilateral angle difference > 5°. Young cases with neither LDH nor low back pain were used as the control group. The results showed that LDH was significantly associated with more coronal facet joint orientation at L1-2 (p = 0.009), L2-3 (p = 0.004), and L3-4 (p = 0.004). No association was established between facet tropism and LDH. This study revealed that facet joint orientation was associated with LDH in young patients (18-35 years); they were more of coronal facing at upper levels. Also, the facet tropism was not associated with LDH.

Lumbar Facet Joint Kinematics and Load Effects During Dynamic Lifting.

OBJECTIVE: To examine the lumbar facet joint kinematics in vivo during dynamic lifting and the effects of the load lifted. BACKGROUND: Although extensive efforts have been dedicated to investigating the risk factors of low back pain (LBP) associated with load handling in the workplace, the biomechanics of lumbar facet joints during such activities is not well understood. METHOD: Fourteen healthy participants performed a load-lifting task while a dynamic stereo-radiography system captured their lumbar motion continuously. Data from 11 participants were included for subsequent analysis. A randomized block design was employed to study the load effect (4.5 kg, 9.0 kg, and 13.5 kg) on bilateral facet joint motions at approximately 60°, 40°, 20°, and 0° trunk-flexion postures. The facet orientations were also examined. RESULTS: Significant load effects were found for the flexion and lateral bending and superior-inferior translation of the facet joints. The L5-S1 displayed greater lateral bending and twisting, which was due to its more posterolateral orientation than the L2-L3, L3-L4, and L4-L5 facet joints. The left-right asymmetry in facet orientation was observed, most prominently at L3-L4 and L5-S1 facet joints. CONCLUSION: The lumbar facet joint kinematics are affected by the magnitude of the lifted load and are dependent on the orientations of articulating adjacent facets. APPLICATION: This study provided new insights into the role of lumbar facet joints in vivo during lifting. Alterations in the facet joint kinematics due to vigorous functional demand can be one of the primary but overlooked mechanical factors in the causation of LBP.

Facet tropism and facet joint orientation: risk factors for the development of early biochemical alterations of lumbar intervertebral discs.

OBJECTIVE: To assess the glycosaminoglycan (GAG) content of lumbar intervertebral discs (IVD) in healthy volunteers with facet tropism (FT) and sagittal facet joint (FJ) orientation using glycosaminoglycan chemical exchange saturation transfer imaging (gagCEST). METHOD: Seventy-five lumbar IVDs of twenty-five young, healthy volunteers without any history of lumbar spine pathologies (13 female; 12 male; mean age: 28.0 ± 4.4 years; range: 21-35 years) were examined with a 3T MRI scanner. Orientation of FT and FJ were assessed for L3/4, L4/5 and L5/S1 using standard T2 weighted images. Biochemical gagCEST imaging was used to determine the GAG content of each nucleus pulposus (NP) and annulus fibrosus (AF). RESULTS: Significantly higher gagCEST values of NP were found in volunteers without FT and normal FJ orientation compared to volunteers with FT and sagittal FJ orientation >45° (P < 0.0001). GagCEST values were significantly higher in volunteers without FT compared to volunteers with moderate or severe FT (moderate FT: P < 0.0001; severe FT: P = 0.0033). Volunteers with normal FJ orientation showed significantly higher gagCEST values compared to those with sagittal FJ orientation >45° (P < 0.001). We found a significant, negative correlation between gagCEST values and higher angels in sagittal FJ orientation (rho = -0.459; P < 0.0001). CONCLUSION: GagCEST analysis indicated lower GAG values of NP in young volunteers with FT and sagittal orientated FJ, indicating that FT and sagittal orientation of the FJ represent risk factors for the development of early biochemical alterations of lumbar IVDs.

Recent Advances in Structural Optimization and Surface Modification on Current Collectors for High-Performance Zinc Anode: Principles, Strategies, and Challenges.

The last several years have witnessed the prosperous development of zinc-ion batteries (ZIBs), which are considered as a promising competitor of energy storage systems thanks to their low cost and high safety. However, the reversibility and availability of this system are blighted by problems such as uncontrollable dendritic growth, hydrogen evolution, and corrosion passivation on anode side. A functionally and structurally well-designed anode current collectors (CCs) is believed as a viable solution for those problems, with a lack of summarization according to its working mechanisms. Herein, this review focuses on the challenges of zinc anode and the mechanisms of modified anode CCs, which can be divided into zincophilic modification, structural design, and steering the preferred crystal facet orientation. The possible prospects and directions on zinc anode research and design are proposed at the end to hopefully promote the practical application of ZIBs.

Are there correlations between facet joint parameters and lumbar disk herniation laterality in young adults?

OBJECTIVE: We aimed to determine whether there is an association, in young adults, between the occurrence of lumbar disk herniation (LDH) at a given segment and the segment's facet joint parameters [facet orientation (FO) and tropism (FT)]. In addition, associations between facet joint parameters in the corresponding segment and LDH laterality were also investigated. METHODS: We retrospectively analyzed data from 529 patients who were between 18 and 35 years old, who had experienced single-level LDH (L4-5 or L5-S1) between June 2017 and December 2019, and with<2 years of clinical history. We included an additional 122 patients with no history of LDH as an age-matched control group. LDH were classified by laterality (left-sided, right-sided, or central herniation). At each level, we investigated the relationship between facet joint parameters and herniation laterality. RESULTS: FOA values at the L4-L5 level and the L5-S1 level were significantly lower and FT was higher for the LDH group compared with those for the control group. The level at which LDH occurred, FOL, FOR, and FT differed significantly among the three groups. There was a significant association between herniationlaterality and FO at the L4-L5 level but not at the L5-S1 level. CONCLUSIONS: Abnormal facet joint parameters are significantly associated with LDH. Young adults with higher FT should be paid more attention, to prevent the occurrence of LDH. Compared with L5-S1 level, intervertebral disk herniation at the L4-L5 level tended to occur ipsilateral to the side with a lower facet joint angle when FT was present.

The biomechanical influence of facet joint parameters on corresponding segment in the lumbar spine: a new visualization method.

BACKGROUND CONTEXT: Facet joints have been discussed as influential factors in the development of lumbar degeneration, which includes disc herniation and degenerative lumbar spondylolisthesis. Facet orientation (FO) and facet tropism (FT) are two important structural parameters of the lumbar facet joints. Many previous studies have focused on single parameter analysis of the lumbar spine. Owing to the correlation between independent variables, single-factor analysis cannot reflect the interaction between variables; however, there has been no corresponding biomechanical method developed to address this problem. PURPOSE: To investigate the complex biomechanical influences on the lumbar spine when vertebral FO and FT are varied using finite element analysis (FEA) and contour maps visualization, and analyze the biomechanical role of facet joint structural parameters in the process of lumbar degenerative diseases. STUDY DESIGN: A biomechanical modelling, analysis, and verification study was performed. METHODS: A three-dimensional non-linear FEA model of 3 denucleated intervertebral discs (L2-3, L3-4, L4-5) with adjacent vertebral bodies (L2-L5) was created. Previously performed in vitro experiments provided experimental data for the range of motion in each load direction that was used for calibration. For 12 lumbar models, different facet joint angles relative to the sagittal plane at both L3-4 facet joints were simulated for 35°≤FO≤50° and 0°≤FT≤15°. By modifying different values of FO and FT, FEA simulation of different lumbar spine models was performed. Contour maps were used to visualize the FO- and FT-relevant data. RESULTS: Under flexion, extension, and torsion moments, facet joint contact force and intradiscal stress increased with increasing FT. In the condition where FT remained 0° and increasing FO values, facet joint contact force and intradiscal stress remained low with no apparent increasing or decreasing trend when the model was under flexion, extension, and torsion moments. In the condition where FO and the FT values were varied at the same time, the highest force and stress regions in the contour maps were observed when all three types of moments were applied. Stress distributions of the L3-4 disc with different FT and FO values showed disc stress increased significantly with increases of FT and was concentrated on the ipsilateral region of the facet joint with the more sagittal orientation. CONCLUSIONS: The combination of FO and FT has an important impact on the corresponding disc and facet joints, but FT played a more significant role. Moreover, disc stress was concentrated on the ipsilateral region of facet joint with greater sagittal orientation when FT existed. FT with high sagittal orientation may increase risk of recurrent LDH due to increase ipsilateral disc pressure. CLINICAL SIGNIFICANCE: These biomechanical findings may help clinicians to understand the prognosis of some lumbar degenerative conditions.

ß-Alanine-Anchored SnO2 Inducing Facet Orientation for High-Efficiency Perovskite Solar Cells.

SnO2 films as a promising electron transport layer (ETL) have been widely used in planar-type perovskite solar cells to achieve an impressive improvement in the conversion efficiency. However, compared with a mesoporous ETL, the interfacial charge carrier transfer of the SnO2 ETL is severely limited due to the issues of oxygen vacancy defects and crystal lattice mismatch between SnO2 and the perovskite, which generally leads to the growth of randomly stacked and porous perovskite layers and subsequently impacts the charge transport and transfer properties. In this work, we developed a facile approach by inducing a bifunctional molecule, ß-alanine, into the SnO2 ETL, which can serve as a bridge to modulate the interfacial charge transfer and the perovskite crystallization kinetics. Benefited by the interfacial ß-alanine, we grew a highly orientational perovskite layer that exhibited superior charge transport properties. Meanwhile, the ß-alanine caused an intimate connection between the perovskite and SnO2 to enhance the interfacial charge transfer. As a result, the power conversion efficiency (PCE) of the ß-alanine-modified device achieved a much-improved value of 19.67% and showed high reproducibility. This work provides a way for developing a high-performance ETL toward the scalable fabrication of highly efficient PSCs.

Sex- and age-related morphological variations in the talar articular surfaces of the calcaneus.

BACKGROUND: The prevalence of foot pathologies, such as flatfoot deformity and hallux valgus, is higher in women and increases with age. It has been reported that these types of foot disorders may also be linked to excessive mobility of the subtalar joint to the eversion direction during weight bearing. Given that the mobility of the joint is determined by its articular morphology, sex- and age-related variations in the subtalar articular surface morphology are possible. The purpose of this study was to investigate the orientation and the curvature radii of the talar articular facets of the calcaneus in relation to age and sex using three-dimensional computer tomography. METHODS: Fifty-six feet without subtalar injuries or disorders were included in this study. The orientations of the talar articular surfaces of the calcaneus were quantified in the sagittal and coronal planes. The curvature radii of the articular surfaces of the calcaneus were also assessed based on the approximations of the sphere surfaces. RESULTS: The talar articular surface was oriented more anteriorly and medially in the females than in the males. The curvature radius of the calcaneal posterior facet in the females exhibited a positive correlation with age, indicative of increased articular surface flattening. CONCLUSIONS: The morphological features of the female calcaneus could induce excessive eversion and could lead to a higher prevalence of foot disorders, including flatfoot and hallux valgus, in elderly females. This study contributes to an understanding of the sexual dimorphism of the articular surfaces of the calcaneus and provides insight into the mechanisms that underline various foot disorders.

Facet joint parameters which may act as risk factors for chronic low back pain.

BACKGROUND: Facet orientation (FO) and facet tropism (FT) are two important structural parameters of lumbar facet joint. The purpose of this study was to evaluate the association between facet joint parameters and chronic low back pain (LBP). METHODS: From June 2017 to January 2019, a total of 542 cases were enrolled in this study. There were 237 males and 305 females with a mean age of 35.8 years (range 18~59 years). All the cases were divided into a LBP group (LBP group) and a non-LBP group (N-LBP group) in this study. We compared their clinical parameters and facet joint parameters between two groups. RESULTS: The LBP group was composed of 190 male and 252 female, whose ages ranged from 17 to 59 years (35.6 ±7.9 y). The N- LBP group was composed of 47 male and 53 female, whose ages ranged from 18 to 59 years (35.9 ± 7.5 y). Of these parameters, BMI (P = 0.008) and FT (P = 0.003) at all three levels were found to be significantly associated with incidence of chronic LBP (P < 0.05), but FO were only found to be significant at L3-L4 level and L5-S1 level (P < 0.05). Logistic regression analysis showed that high BMI and large FT were significant risk factors for chronic LBP (P < 0.05), and FT were found to might be independent risk factors for chronic LBP. CONCLUSION: FT may play a more important role in the pathogenesis of chronic LBP.

Are facet joint parameters risk factors for recurrent lumbar disc herniation? A pilot study in a Chinese population.

Recurrent lumbar disc herniation (rLDH) is one of the major problems when surgically treating patients with LDH. Data on previous studies investigated the associations between facet joint parameters and rLDH appear only rarely in the literature. This study's objective was to evaluate the association between facet joint parameters [facet orientation (FO) and facet tropism (FT)] and rLDH. From June 2005 to January 2014, 346 patients having single-level lumbar disc herniation (LDH), who underwent surgery, were included in this study. We divided the patients into the recurrent group (R group) and the nonrecurrent group (N group). According to 25%, 50% and 75% quantiles of FO, all the cases were divided into 4 subgroups (＜42°, 42～45°, 46～49°, and ＞49°). Cases were divided into 3 groups according to different range of FT (＜3°, 3～4° and ＞4°). The relationships between the facet joint parameters and rLDH were evaluated. All cases in the study were followed up for more than 5 years postoperatively. The recurrence rates of different FO groups were statistically significant (P < 0.001). With the decrease of FO, the risk of rLDH increases continuously. Also, there were statistically significant recurrence rates in different FT groups (P < 0.001), which showed the incidence of rLDH increases gradually with the increase of FT. Facet joint parameters significantly influence the biomechanics of the corresponding segment. Facet joint parameters may play a more important role in the pathogenesis of rLDH.

A Radiological Study of the Association of Facet Joint Tropism and Facet Angulation With Degenerative Spondylolisthesis.

OBJECTIVE: To study the association of facet joint angulation and joint tropism with degenerative spondylolisthesis (DS) through a comparison with a matched control group. METHODS: This radiographic study was carried out in 2 groups of 45 patients each. Group A contained patients with single-level DS, while group B (control) contained non-DS patients with similar age and degeneration who underwent surgery for disc prolapse or lumbar stenosis. DS was diagnosed based on translation of ≥ 3 mm on standing lateral radiography. Axial magnetic resonance imaging from L3 to S1 was utilized to assess the angulation of facet joints in relation to the coronal plane; a difference of ≥ 8° was considered to indicate tropism. RESULTS: Among 45 patients with DS, 15 were males and 30 females. Their mean age was 62.2 years. Facet tropism was identified in 20 of 45 patients at the level of DS, 12 patients at a level proximal to DS, and 15 patients at a level distal to DS. Facet tropism was found in 7 of the 45 patients in group B. At L3-4, facet tropism was observed in 13 patients (28.88%) in group A and 2 (4.44%) in group B. At L4-5, tropism was observed in 19 patients (42.22%) in group A and 5 (11.11%) in group B. At L5-S1, tropism was seen in 17 patients (37.77%) in group A and 2 (4.44%) in group B. Group A showed a significantly higher prevalence of multilevel facet tropism and tropism at levels adjacent to the DS level. A higher average angulation of facet joints was observed in the DS group, but the difference was not statistically significant at all levels. CONCLUSION: The present study documented a statistically significant relationship between facet tropism and DS. A higher prevalence of facet tropism was also found in DS patients at non-DS levels, which is a novel observation. This finding supports the argument that facet tropism is a pre-existing morphological variation contributing to the development of DS, not a result of secondary remodelling.

Association Between Irregular Alteration of Facet Orientation and Degenerative Lumbar Spondylolisthesis.

BACKGROUND: Numerous studies have reported that irregular alteration of facet orientation (IAFO) is associated with lumbar disc herniation (LDH) in adolescents. The present study investigated the association between IAFO and degenerative lumbar spondylolisthesis (DLS) at the L4-5 segment. METHODS: Forty-two adults with DLS were enrolled in this study. Facet angles were measured in the bone window of the computed tomography scan. Large-small-large (LSL) was defined as a type of IAFO that includes the angle of facet joints at L4-5, which is smaller than that in L3-4 and L5-S1 segments. Fifty subjects with LDH at L4-5 served as controls. Data were analyzed using logistic regression analysis. RESULTS: In the 42 patients and 50 controls, the facet angle was measured at 276 levers from L3-4 to L5-S1. The mean included angles of L3-4, L4-5, and L5-S1 were 71.5 ± 19.97°, 51.79 ± 21.43°, and 102.89 ± 20.37°, respectively, in the DLS group and 77.48 ± 17.24°, 91.00 ± 17.24, and 102.94 ± 19.75°, respectively, in the control group. LSL was detected in 38 of 42 subjects (90.5%) in the DLS group, compared with 9 of 50 (18.0%) in the controls. The sagittal orientation facet joint in L4-5 was associated with DLS (odds ratio [OR], 26.24; 95% confidence interval [CI], 13.30-155.35; P = 0.000). The facet in L3-4 with a more coronal orientation than that in L4-5 was also correlated with DLS (OR, 33.68; 95% CI, 9.86-115.06; P = 0.000). There was no correlation between the facet in L5-S1 and DLS in L4-5 (P = 0.999), but there was a strong relationship between LSL in L3-5 and DLS in L4-5 (OR, 43.278; 95% CI, 12.303-152.232; P = 0.000). CONCLUSIONS: The data presented here demonstrate that LSL, which is an irregular alteration of facet joint orientation, is associated with the degenerative lumbar spondylolisthesis at L4-5.

Changes in the axial orientation of the zygapophyseal joint in the subaxial cervical spine from childhood to middle-age, and the biomechanical implications of these changes.

The objective of this study was to investigate the effect of age on facet orientation (FO) of the cervical spine during development, maturation, and degeneration. Computed tomography (CT) data of the cervical spine of 131 subjects without pathology of the cervical spine were analyzed. Subjects were categorized as: pediatric (n=36, 8-16years old), young adult (n=33, 18-24years old), and middle-age (n=62, 40-59years old). Serial CT scans were reconstructed by image processing. The FO in the axial plane was measured bilaterally at each vertebral level from C3/4 to C6/7. Differences in FO were analyzed between the 3 groups. The degree of external rotation of FO significantly decreased at C3/4 and C4/5 with increasing in age, and maximum external rotation was observed at C5/6. The external rotation at C6/7 increased from pediatric to young adulthood, but decreased from young adults to middle-aged adults. The dominant external rotation was seen in C4/5 and C5/6 in the pediatric age group, C5/6 and C6/7 in young adults, and C4/5 and C5/6 in middle-aged adults. These results lead us to conclude that FO in the axial plane exhibits significant differences with age. The degree of external rotation with respect to FO at each vertebral level is comparable to changes in cervical spinal dynamics with age. Hence, FO in the axial plane is a biomechanical parameter that can be used to assess changes in the cervical spinal during maturation and degeneration.

Controlling Surface Termination and Facet Orientation in Cu2O Nanoparticles for High Photocatalytic Activity: A Combined Experimental and Density Functional Theory Study.

Cu2O nanoparticles with controllable facets are of great significance for photocatalysis. In this work, the surface termination and facet orientation of Cu2O nanoparticles are accurately tuned by adjusting the amount of hydroxylamine hydrochloride and surfactant. It is found that Cu2O nanoparticles with Cu-terminated (110) or (111) surfaces show high photocatalytic activity, while other exposed facets show poor reactivity. Density functional theory simulations confirm that sodium dodecyl sulfate surfactant can lower the surface free energy of Cu-terminated surfaces, increase the density of exposed Cu atoms at the surfaces and thus benefit the photocatalytic activity. It also shows that the poor reactivity of the Cu-terminated Cu2O (100) surface is due to the high energy barrier of holes at the surface region.

Analysis of the Relationship between Ligamentum Flavum Thickening and Lumbar Segmental Instability, Disc Degeneration, and Facet Joint Osteoarthritis in Lumbar Spinal Stenosis.

STUDY DESIGN: Cross-sectional study. PURPOSE: To investigate the relationship between ligamentum flavum (LF) thickening and lumbar segmental instability and disc degeneration and facet joint osteoarthritis. OVERVIEW OF LITERATURE: Posterior spinal structures, including LF thickness, play a major role in lumbar spinal canal stenosis pathogenesis. The cause of LF thickening is multifactorial and includes activity level, age, and mechanical stress. LF thickening pathogenesis is unknown. METHODS: We examined 419 patients who underwent computed tomography (CT) myelography and magnetic resonance imaging after complaints of clinical symptoms. To investigate LF hypertrophy, 57 patients whose lumbar vertebra had normal disc heights at L4-5 were selected to exclude LF buckling as a hypertrophy component. LF thickness, disc space widening angulation in flexion, segmental angulation, presence of a vacuum phenomenon, and lumbar lordosis at T12-S1 were investigated. Disc and facet degeneration were also evaluated. Facet joint orientation was measured via an axial CT scan. RESULTS: The mean LF thickness in all patients was 4.4±1.0 mm at L4-5. There was a significant correlation between LF thickness and disc degeneration; LF thickness significantly increased with severe disc degeneration and facet joint osteoarthritis. There was a tendency toward increased LF thickness in more sagittalized facet joints than in coronalized facet joints. Logistic regression analysis showed that LF thickening was influenced by segmental angulation and facet joint osteoarthritis. Patient age was associated with LF thickening. CONCLUSIONS: LF hypertrophy development was associated with segmental instability and severe disc degeneration, severe facet joint osteoarthritis, and a sagittalized facet joint orientation.

Facet orientation and tropism: Associations with asymmetric lumbar paraspinal and psoas muscle parameters in patients with chronic low back pain.

BACKGROUND: Many studies have explored the relationship between facet tropism and facet joint osteoarthritis, disc degeneration and degenerative spondylolisthesis. However, the associations between facet orientation and tropism, and paraspinal muscles have not been studied. OBJECTIVE: To analyze the associations between facet orientation and tropism, and parameters of paraspinal muscles in patients with chronic low back pain. METHODS: Ninety-five patients with chronic low back pain were consecutively enrolled. Their facet joint angles were measured on computed tomography (CT) while gross cross-sectional area (GCSA), functional cross-sectional area (FCSA) and T2 signal intensity of lumbar paraspinal and psoas muscle were evaluated on magnetic resonance imaging (MRI). RESULTS: The GCSA and FCSA were significantly smaller for multifidus muscle (P< 0.001), but significantly larger for erector spinae and psoas muscles (P< 0.001), in coronally-orientated group than those in sagittally-orientated group. The differences of bilateral GCSA and FCSA of multifidus muscle were significantly larger in facet tropism group than those in no facet tropism group (P= 0.009 and P= 0.019). CONCLUSIONS: Muscular asymmetries may develop in the lumbar region of the spine, which are associated with facet asymmetry in patients with chronic low back pain. Longitudinal studies are needed to understand the causal relationship between facet orientation and tropism and muscular asymmetry in future.

The influence of facet joint orientation and tropism on the stress at the adjacent segment after lumbar fusion surgery: a biomechanical analysis.

BACKGROUND CONTEXT: Facet joint orientation and tropism influence the biomechanics of the corresponding segment. Therefore, the sagittal orientation or tropism of the facet joint adjacent to the fusion segment seems a potential risk factor for adjacent segment degeneration. However, there have been no biomechanical studies regarding this issue. PURPOSE: To investigate the association between adjacent facet orientation and facet tropism and stress in adjacent disc/facet joints using finite element (FE) analysis. STUDY DESIGN: An FE analysis. METHODS: Four intact (F50, F55, F60, and FT [facet tropism]) and matched L3-L4 fusion (F50, F55, F60, and FT fusion) models with different facet joint orientation (50°, 55°, 60° relative to the coronal plane, and facet tropism, respectively) at both L2-L3 facet joints were simulated. In each model, intradiscal pressures and facet contact force at the L2-L3 segment were investigated under pure moments and anterior shear force. RESULTS: Compared with the matched-intact model, the F60 fusion model yielded the highest and largest percentage increase of intradiscal pressure at the L2-L3 segment under flexion, torsion moment, and anterior shear force among the F50, F55, and F60 fusion models. F60 fusion model also demonstrated the largest facet contact force under torsion moment among the F50, F55, and F60 fusion models. In all conditions tested, the FT fusion model demonstrated the highest intradiscal pressure and facet contact force of all the models. CONCLUSIONS: Facet joint orientation and tropism at the adjacent segment influences the overstress of the adjacent segment, especially under the clinical circumstance of increased anterior shear force.