Plane Joint Research Articles

The role of the planar joints without bolts on the structural behaviour of coupled segmental tunnels built in soft soils

This paper aims to evaluate the role of planar joints without bolts on the structural behaviour of segmental tunnels. Segmental tunnels could be vulnerable to deformation problems due to the presence of the joints, such as segment cracking, joint damage and its opening. As a result, the lining presents a limitation of its load capacity and stiffness loss that can jeopardize its safety and durability. Thus, in this paper the joint influence was evaluated on the lining behaviour with different structural parameters. These parameters were relative height of joints, slenderness ratio and pressure ratio of the lining. The lining behaviour was estimated by numerical models that included the nonlinearity of joints and materials using a 3D finite element model. The joint influence was studied through the stiffness, the load capacity and the failure mechanism of the lining. It is concluded that the joints have a main influence on the structural behaviour of the lining. For example, in the bending domain due to the joint opening and the damage by the coupling effects, as the diametral deformation of the lining increases, the stiffness decrements. This stiffness loss reached without the reinforcement yields. On the other hand, in the compression domain, the stiffness loss begins with the joint failure by concrete bursting. The joint losses its capacity to transfer load. It develops a failure mechanism of lining at lower deformation. Thus, the design lining should be based on a suitable role of their joints.

Potential applications of deep learning in automatic rock joint trace mapping in a rock mass

In blasted rock slopes and underground openings, rock joints are visible in different forms. Rock joints are often exposed as planes confining rock blocks and visible as traces on a well-blasted, smooth rock mass surface. A realistic rock joint model should include both visual forms of joints in a rock mass: i.e., both joint traces and joint planes. Imaged-based 2D semantic segmentation using deep learning via the Convolutional Neural Network (CNN) has shown promising results in extracting joint traces in a rock mass. In 3D analysis, research studies using deep learning have demonstrated outperforming results in automatically extracting joint planes from an unstructured 3D point cloud compared to state-of-the-art methods. We discuss a pilot study using 3D true colour point cloud and their source and derived 2D images in this paper. In the study, we aim to implement and compare various CNN-based networks found in the literature for automatic extraction of joint traces from laser scanning and photogrammetry data. Extracted joint traces can then be clustered and connected to potential joint planes as joint objects in a discrete joint model. This can contribute to a more accurate estimation of rock joint persistence. The goal of the study is to compare the efficiency and accuracy between using 2D images and 3D point cloud as input data. Data are collected from two infrastructure projects with blasted rock slopes and tunnels in Norway.

ОЦЕНКА МЕХАНИЧЕСКИХ ХАРАКТЕРИСТИК КАМЕННОЙ КЛАДКИ СУЩЕСТВУЮЩИХ ЗДАНИЙ

An analysis of known methods for evaluation the compressive strength and modulus of elasticity of existing masonry structures have been carried out. A method for determining the mechanical characteristics of masonry, based on tests of the specimens cutted from the body of the masonry in the form of triangular prisms have been given. Comparison of compressive strength, initial shear strength and angle of internal friction, obtained from the results of tests of prism specimens, with the results of tests of masonry specimens in accordance with the standards STB EN 1052-1 and STB EN 1052-3 has been carried out. Satisfactory agreement between the values of the compressive strength of the masonry and the secant modulus of elasticity obtained by testing the prisms with a compressive load acting perpendicular to the plane of the horizontal mortar joints with the test results according to the STB EN 1052-1 method has been shown. The initial shear strength of masonry, obtained from the results of tests according to STB EN 1052-3, differed downward from the strength established from the results of tests of prism specimens for compression, while the values of the angle of internal friction determined by the two methods were close.

EFFICIENCY OF COMPUTER NAVIGATION TECHNOLOGY IN TOTAL KNEE REPLACEMENT

We studied the treatment outcomes in 124 patients (102 women and 22 men) aged 51 to 83 years (median 69 [65; 76] years) on 124 knee joints. Patients were divided into 2 groups: the study group – 62 people aged 51 to 83 years (median – 69.1 [64;74] years), who used computer navigation, and the comparison group – 62 people aged 56 to 83 years (median 69 [65;78] years), in which surgical in-tervention was performed according to the standard technique. Long-term results were studied in terms of 3 to 36 months. During the examination, the deformity variant was determined, radiometric parameters of the knee joints were measured using the Knee Society Score (KSS), Functional Knee Society Score (FKSS), and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) scales. Also, functional stress tests were performed to assess the stability of the knee joint in the frontal plane and functional indicators of the range of motion. After surgery, in the study group, the WOMAC values decreased by 5.90 times and the median value to 11 [8;15] points (p < 0.001), in the comparison group they decreased by 4.81 times to 13.5 [8;16] points (p < 0.001), KSS in-creased by 3.88 times. Median KSS in the study group increased 3.91 times and reached 86 [84;95] points (p < 0.001), in the comparison group it increased 3.86 times only to 85 [77;95] points (p < 0.001). FKSS data increased by 1.75 times. The median FKSS in the study group increased 2.08 times and reached 94 [85;99] points (p < 0.001), in the comparison group it increased 1.60 times only to 93 [83;95] points (p < 0.001).

Selective surgical reinnervationn of the axillary nerve due to supraclavicular brachial plexus injury: outcomes of 42 consecutive cases, causes of inefficacy

Objective: retrospective analysis of the outcomes of selective surgical reinnervation (SSR) of the axillary nerve (Ax) in patients with supraclavicular brachial plexus injury (SBPI). Materials and methods. Forty-two patients (mean age 31.2 years) received 25 SSR with extraplexus donor nerves (e-ND) – 9 cases of subtotal SBPI and 16 cases of complete SBPI. In 17 cases of subtotal SBPI exclusively intraplexus donor nerve (i-ND) were utilized. Twenty-nine (69%) patients received SSR in terms up to 6 months, 13 patients (31%) – in terms more than 6 months. All patients at the time of inclusion were examined neurologically, electophisilogically and in 6, 9, 15 and 17 months. Recovery of the deltoid (D) muscle was assessed on Medical Research Council Scale (MRC Scale) – effective power (Еp). Recovery of effective function (Ef) has been assessed on the basis of flexion angle in glenohumeral joint in sagittal plane. Results. Ер of D recovered in 12 patients (28%), in terms up to 6 months - in 31%, more than 6 months – in 23%. Ep of D recovered after SSR with i-ND in 9 patients (52%), in terms up to than 6 months - in 60%, more than 6 months – in 43%. Ep of D recovered after SSR with e-ND in 3 patients (12%), in terms up to 6 months- in 16%, no recovery of Ep has been observed in terms more than 6months.Ef of D recovered in 11 patients (26%), in terms up to 6months - in 31%, more than 6months – in 15%. Ef of D recovered after SSR with i-ND in 8 patients (53%), in terms up to 6 months - in 60%, more than 6 months – in 29%. Ep of D recovered after SSR with e-ND in 3 cases (12%), in terms up to 6months - in 16%, no recovery of Ep has been observed in terms more than 6months. Recovery of Ef of D at subtotal SBPI occurred in 10 cases (38%), regardless of whether i-ND or e-ND have been utilized. SSR with e-ND at subtotal SBPI allowed restoring Ef of D in 2 cases (22%). SSR with i-ND at subtotal SBPI allowed restoring Ef of D in 8 cases (47%). SSR at complete SBPI allowed restoring Ef of D in 1 case (6%). Conclusions. e-ND can be utilized at complete SBPI in order to provide stability to glenohumeral joint in terms up to 6 months; i-ND should be utilized in all cases of subtotal SBPI in order to provide Ef to D in terms up to 6 months.

Between-day reliability and minimum detectable change of the Conventional Gait Model 2 and Plug-in Gait Model during running

BackgroundThe Plug-in Gait model (PiG) is commonly used in 3D motion analysis but has limited reliability. Although an improved version of PiG has been developed, called the Conventional Gait Model 2 (CGM2), there is limited evidence on its between-day reliability for running. Research questionWhat is the between-day intraclass correlation coefficient (ICC3,k) and minimum detectable change (MDC) of lower limb kinematics and kinetics for CGM2 during running and does reliability differ between CGM2 and PiG. MethodsTwenty-three healthy participants performed running at a comfortable speed in two identical test sessions at least 5 days apart. Lower limb kinematic and kinetic data in the three planes of motion were calculated using CGM2 and PiG. The ICC and MDC were calculated for the kinematic and kinetic parameters at initial contact and peak during the stance phase of running. ResultsCGM2 kinematics showed good-to-excellent reliability (ICC: 0.75–0.93), except for hip extension and ankle internal rotation, and less than 5° MDC (1.8°−4.9°) of the coronal and sagittal planes, except for hip extension. PiG showed poor-to-moderate reliability (ICC: −0.15 to 0.72) in the coronal and transverse planes and greater than 5° MDC (5.0°−21.8°), except for knee extension, adduction, and ankle dorsiflexion. CGM2 showed good-to-excellent reliability for peak kinetics (ICC: 0.75–0.97), except for hip internal rotation and knee extension. The ICC and MDC were higher for CGM2 than PiG, with significant differences in the coronal plane of the hip and knee joints and transverse plane of the hip joint in kinematics and in the sagittal and coronal plane of the hip and knee joints in kinetics. SignificanceThe between-day reliability of CGM2 was mostly good to excellent for lower limb kinematics and kinetics during running. We believe that CGM2 can more accurately assess kinematic differences between the coronal and transverse planes than the PiG.

A Dynamic Loading Mechanism for a Morphing Winglet

Abstract A loading mechanism for a variable cant angle morphing winglet is proposed in this paper. The mechanism provides a method of loading a morphing winglet with the simulated aerodynamic lift force by maintaining its application direction always orthogonal to the surface of the winglet throughout the range of motion. The loading mechanism is developed by type synthesis of four-bar linkages through enumeration of prismatic and revolute joints. The final design is a R-P-R-P four-bar linkage modified by merging the middle P-R joint together to form a planar joint named Shark-fin. The shape of Shark-fin is optimized to minimize its weight effect on the overall loading system. A half-scale prototype was built as a reference to address several implementation issues including the neutral loading condition. Afterwards, a full-size dynamic loading mechanism was successfully constructed and implemented to load test a full-size morphing winglet.

Effect of dynamic cyclic shear on frictional strength weakening of a plane joint

Understanding and predicting the frictional behavior of rock joints subject to dynamic cyclic loading is essential for the seismic safety of many rock engineering problems. In this paper, cyclic shear experiments were conducted based on a shaking table apparatus. A series of cyclic friction tests covering various earthquake-relevant frequencies was conducted on dry planar joints of granitic rock. The friction behavior especially the dynamic evolution of the frictional strength under cyclic loading was investigated, with the influence of loading frequency on the frictional strength weakening and energy dissipation quantified. Based on the experimental results, we propose a phenomenological model characterizing the dynamic frictional behavior of planar granite joints under cyclic loading. This empirical formulation relates the evolution of joint frictional strength to the number of cycles of dynamic loading. As the frequency increases, the frictional strength and dissipated energy density both show a pronounced reduction, while the strength weakening ratio and the critical number of cycles (at which the residual strength is reached) increase in a logarithmic fashion. The frictional strength evolution is described by the product of the peak frictional strength and a damage function, which is further related to the number of cycles and the frequency. In addition, a close inspection of fracture surface morphology after the cyclic loading was conducted to understand the role of surface wear and gouge formation in the frequency-enhanced dynamic friction weakening of rock joints.

Investigation of spatial plane joint characteristic for dynamic analysis of VSV mechanism based on similarity scaling technique

The Variable Stator Vane (VSV) mechanism is utilized to adjust the stator vane angles so as to delay the compressor stall. Establishing the dynamic model of the system, which is the basis to obtain different joint characteristics more in line with the real case, is worth analyzing. In this work, a comprehensive dynamic model of the scaled system of VSV mechanism’s single kinematic chain by the Lagrange multiplier method is built, thus the spatial plane joint characteristic’s effects on the behavior of the scaled system are investigated. Since a full-scale facility is unavailable for testing sometimes, the technique of similarity scaling is resorted to establishing the scaled principle-level model which has a certain relationship with the prototype in structure and material and so on. Then an example of the dynamic modeling procedure of the spatial RSSR mechanism included in the scaled model is presented with the aim of establishing a guide to model the whole system. Therefore, the equation of motion of the scale system is expediently established using some systematic method. Finally, inertial navigation sensors are used to measure the corresponding displacement for evaluation with accuracy of the established dynamic model.

Design and Analysis of 6-DoFs Upper Limb Assistant Rehabilitation Robot

This paper presents an assisted upper limb rehabilitation robot (ULRR) for patients who have experienced stroke who are in the middle and late stages of rehabilitation and have certain muscle strength. The ULRR can complete adduction and abduction motion of the shoulder joint (SJ) in the frontal plane in one step, which can save time and improve the efficiency of rehabilitation training. Based on the principles of ergonomics and rehabilitation medicine, the freedom degree of the upper limb and the motion range of each joint are determined, and the structure of the shoulder, the elbow, and the wrist joint of ULRR are designed. The kinematics model of the robot is established, and the kinematics equations are derived. Meanwhile, the simulation analysis and the workspace analysis of the robot are carried out, and the different movement forms of SJ adduction and abduction are compared and analyzed. Then, the trajectory of the robot is planned to complete the act of drinking water. Finally, an experimental platform is built to complete the ULRR to help participants complete the experiments of drinking water and active training. The experiments verify that the robot is suitable for rehabilitation tasks.

Effect of boundary conditions on a high-performance isolation hexapod platform

Isolation of spacecraft microvibrations is essential for the successful deployment of instruments relying on high-precision pointing. Hexapod platforms represent a promising solution, but the difficulties associated with attaining desirable 3D dynamics within acceptable mass and complexity budgets have led to a minimal practical adoption. This paper addresses the influence of strut boundary conditions (BCs) on system-level mechanical disturbance suppression. Inherent limitations of the traditional all-rotational joint configuration are highlighted and shown to originate in link mass and rotational inertia. A pin-slider BC alternative is proposed and analytically proven to alleviate them in both 2D and 3D. The advantages of the new BC hold for arbitrary parallel manipulators and are demonstrated for several hexapod geometries through numerical tests. A configuration with favourable performance is suggested. Finally, a novel planar joint that allows the physical realisation of the proposed BC is described and validated. Consequently, this work enables the development of platforms for microvibration attenuation that do not require active control.

Numerical Investigation of Hydraulic Fracture Network Formation of Jointed Shale with Oriented Perforation

This paper aims at exploring the fracture evolution as well as capturing the fracture network formation of jointed shale during hydraulic fracturing process by numerical simulation using the Rock Failure Process Analysis System of Flow (RFPA—Flow). The simulations were successfully completed following two stages. In the first stage, a series of simulations are performed to investigate the influence of different angle-oriented perforations on fracture initiation and propagation. The simulation results agreed well with the experimental results confirming the validity of the RFPA-Flow code in the application. In the second stage, extensive hydraulic fracturing simulations on jointed shale with different angled-joint planes and different angle-oriented perforations were performed. The simulation results demonstrated that the fracture evolution changes significantly as the magnitude of α (the angle between perforation and the joint plane) increased. It was found that a large α value could lead to a larger the tensile stress region around the fracture tip resulting in more joint planes pulled apart. It could also induce more secondary fractures and hence a more complex fracture could be formed. As a result, the α value of 60° to 90° were found to aid in the fracture network generation. On the other hand, the angle β being the angle between the parallel joints and the maximum stress direction was another important factor in fracture evolution. Its influence on fracturing performance was similar to angle α. It was found that the initiation and breakdown pressure of jointed shale were in proportional to the magnitude of angle β. Therefore, this paper introduced an efficient approach to promote the formation of a complex fracture network in jointed shale with the presence of oriented perforation, which could offer valuable guidance for the design of unconventional reservoir reconstruction.

Knee joint prototype based on cam mechanism – design and video analysis

The paper is focused on a design of mechanism accurately reproducing a complex motion in the sagittal plane of a human knee joint. The desired movement is modelled by applying specially designed shapes of cooperating cam elements based on the fixed and moving centroids of knee joint’s instantaneous centre of rotation. The mechanism’s CAD model and prototype are built using 3D printed elements, providing the possibility of interchanging the elements with cam profiles and adjusting the mechanism’s movement to individual needs. The mechanism movement is measured by analysing a video in Matlab and tracking colour markers on the prototype.

Arthroscopic Evaluation of Subtle Syndesmotic Instability: Are We Pulling Correctly in the Coronal Plane?

Category: Ankle; Sports; Trauma Introduction/Purpose: While the lateral hook test (LHT) has been widely used to arthroscopically evaluate syndesmotic instability in the coronal plane, it is unclear whether the angulation of the applied force has any impact on the degree of instability. The aim of this study was to determine if changing the direction of the force applied while performing the LHT impacts the amount of coronal diastasis observed in purely ligamentous syndesmotic injuries. Methods: In 10 cadaveric specimens, arthroscopic evaluation of the distal tibiofibular joint in the coronal plane was performed. Anterior and posterior third coronal plane diastasis were assessed in the intact state and repeated after sequential transection of the, 1) anterior inferior tibiofibular ligament (AITFL), 2) the interosseous ligament (IOL) and the 3) posterior inferior tibiofibular ligament (PITFL). In all scenarios, the lateral hook test (LHT) was performed under 100N of laterally directed force. Additionally, LHT was also performed under 1) anterior inclination of 15 degrees and 2) posterior inclination of 15 degrees in the intact and AITFL+IOL deficient state. One-way ANOVA with post hoc Tukey HSD was used to test for significant differences in coronal plane measurements between each stage of ligament transection, and to determine the effect of different directions of force application on coronal space measurements in the intact and AITFL+IOL transected states. Results: Compared to the intact state, the distal tibiofibular joint remained stable after transection of AITFL under laterally directed force with no angulation. However, after additional transection of the IOL, the syndesmosis became unstable in the coronal plane (p = 0.029 and 0.025 for anterior and posterior third diastasis, respectively). This instability worsened further with subsequent transection of the PITFL (p = <0.001). Moreover, there was no statistical difference in anterior and posterior-third coronal diastasis in both intact and AITFL+IOL deficient states under neutral, anterior, and posteriorly directed force(p-values ranging from 0.816-0.993 and 0.396-0.80,respectively). However, in AITFL+IOL transected state, posteriorly directed forces resulted in greater diastasis than neutral or anteriorly directed forces. Conclusion: Angulation of the applied force ranging from 15 degrees anteriorly to 15 degrees posteriorly during intraoperative LHT has no effect on coronal plane measurements in patients with subtle syndesmotic instability. On the other hand, posteriorly directed forces result in more sizable diastasis, potentially increasing their sensitivity. When arthroscopically evaluating subtle syndesmotic instability, clinicians should assess coronal diastasis with the hook angled 15 degrees posteriorly.

Metatarsophalangeal Joint Dynamic Stiffness During Toe Rocker Changes With Walking Speed.

Dynamic joint stiffness (or simply "stiffness") is a customization criteria used to tune mechanical properties of orthotic and prosthetic devices. This study examines metatarsophalangeal (MTP) joint stiffness during the toe-rocker phase of barefoot walking and establishes baseline characteristics of MTP joint stiffness. Ten healthy individuals walked at 4 speeds (0.4, 0.6, 0.8, and 1.0statures·s-1) over level ground. MTP sagittal plane joint angles and moments were calculated during the toe-rocker phase of stance. Least-squares linear regressions were conducted on the MTP moment versus angle curve to determine joint stiffness during early toe rocker and late toe rocker. Multilevel linear models were used to test for statistically significant differences between conditions. Early toe rocker stiffness was positive, while late toe rocker was negative. Both early toe rocker and late toe rocker stiffness increased in magnitude significantly with speed. This study establishes baseline characteristics of MTP joint stiffness in healthy walking, which previously had not been examined through a range of controlled walking speeds. This information can be used in the future as design criteria for orthotic and prosthetic ankle and ankle-foot devices that can imitate, support, and facilitate natural human foot motion during walking better than existing devices.

Validity of an artificial intelligence, human pose estimation model for measuring single-leg squat kinematics

Few studies have investigated the validity of 2D pose estimation models to evaluate kinematics throughout a motion and none have included adolescents. Adolescent athletes completed single-leg squats while 3D kinematic data and 2D sagittal and frontal plane videos were recorded. Sagittal and frontal plane joint motion throughout the single-leg squats and angles at peak knee flexion were compared among 2D pose estimation, 3D motion analysis, and traditional 2D motion analysis techniques. Statistical parametric mapping compared waveforms while Pearson’s correlation compared the relationships of joint angles at peak knee flexion among techniques, respectively. We observed significant waveform differences between 2D pose estimation and 3D motion analysis at the beginning and end of the squat for sagittal plane hip and knee motion, for most of the squat for frontal plane hip motion, and throughout the entire squat for sagittal plane ankle motion and frontal plane pelvic motion. We observed moderate-to-strong relationships (r = 0.68-0.94) for sagittal plane joint angles between 2D pose estimation and 3D techniques. We observed fair correlations (r = 0.53-0.54) for frontal plane pelvic and hip joint angles between 2D pose estimation and 3D motion analysis. We observed poor relationships for the frontal plane knee angle between 3D motion analysis with 2D pose estimation (r = 0.20) and traditional 2D motion analysis (r = 0.05), respectively, but observed a strong relationship (r = 0.95) between the 2D techniques. 2D pose estimation is a valid alternative to 3D motion analysis and traditional 2D motion analysis for evaluating most sagittal and frontal plane angles during a single-leg squatting task.

Czynniki ograniczające zgięcie stawu kolanowego podczas chodu u dziecka z mózgowym porażeniem

Introduction: A child with cerebral palsy has multiple coexisting deficits that limit functional abilities such as walking. Their interaction shapes the kinematic gait pattern by modulating both the range and shape of the knee flexion movement during the swing phase. The significance of the effect of specific impairments on knee joint flexion range-of-motion is not clear. Aim: The aim of this study is to comprehensively analyse the effect of coexisting deficits on the range and speed of flexion at the knee joint in the sagittal plane in a child with cerebral palsy. Material and methods: In 132 patients (M = 76; F = 56; age: 11 ± 4) with spastic cerebral palsy, lower limb joint range-of-motion, selective motor control, strength and spasticity were assessed during the clinical examination. The range of knee flexion in the terminal stance phase, pre-swing and initial swing (TSt-ISw) was assessed during the laboratory three-dimensional gait analysis. Results: The TSt-ISw knee flexion movement was most strongly (RS = –0.28) dependent on knee extensor hypertonia, similarly as in the KSt stance phase (RS = –0.22) and in the KSw swing phase (RS = –0.22). The velocity of flexion (V) was most strongly correlated with knee extensor muscle hypertonia (RS = –0.32) and successively with selective control of hip flexor movement (RS = –0.28), knee extensor strength (RS = –0.23) and plantar flexor hypertonia (RS = –0.21). Conclusions: The range-of-motion of knee flexion in the sagittal plane depends on the hypertonia of the knee extensor muscles in both the TSt-ISw and KSt and KSw phases. Velocity increase depends on the occurrence of knee extensor muscle hypertonia, selective control of hip flexor movement, knee extensor strength and plantar flexor hypertonia.

Relationship of Clubhead Speed With Explosive Power and Muscle Strength of the Hip and Trunk Joints of Elite Golfers.

Suhara, H, Nariai, M, Takagi, T, Akiyama, K, Nagashima, J, and Shiraki, H. Relationship of clubhead speed with explosive power and muscle strength of the hip and trunk joints of elite golfers. J Strength Cond Res 37(4): 859-865, 2023-In golf, the driving distance of the ball is affected by the clubhead speed (CHS) on impact. We aimed to clarify the relationship between CHS and explosive power and muscle strength of the hip and trunk muscles in elite golfers (male age: 19.6 ± 1.9 years, male handicap: 4.4 ± 0.9, female age: 17.7 ± 1.4 years, and female handicap: 6.2 ± 0.7). A correlational design was used to assess the relationships between CHS and strength (hip extension-flexion and trunk rotation of peak torque at an isokinetic 60 and 180°·s -1 angular velocity) and CHS and power (countermovement jump [CMJ]; peak power and jump height; backward overhead medicine ball [BOMB] throw). Fourteen each of male and female elite golfers were included. The CHS during the golf swing was measured using a Doppler radar measurement device (Trackman). A correlation analysis between each measurement and CHS ( p ≤ 0.05) was conducted. We found that the peak torque of right hip extension at an angular velocity of 180°/s (male, r = 0.67; female, r = 0.61), peak CMJ power (male: r = 0.63, female: r = 0.75), and BOMB throw distance (male, r = 0.6; female, 0.6) were positively correlated with CHS in both male and female golfers. These results suggest that the extensor strength of the lower extremities and trunk, centered on the hip joint in the sagittal plane, is important for physical fitness and muscle strength measurement related to CHS. Conversely, concentric trunk rotator strength and CHS were not correlated, suggesting that concentric trunk rotator strength may not be actively involved in CHS.

Research on Mechanical Properties and Macroscopic Fracture Evolution of Rock with Different Joint Plane Features

To analyze the safety of geological engineering, experimental research on the mechanical properties of the rock joint plane is critical. In this paper, triaxial compression tests are carried out on rock specimens with the different prefabricated joint planes, including different dip angles, roughness, confining pressure and surrounding rock strength, and the strength characteristics, failure modes, stress evolution laws, and crack propagation laws are revealed. The test results show that when the specimen is damaged, the strain, peak stress, and residual strength all increase with the increase of roughness, confining pressure, and strength of surrounding rock but decrease significantly with the increase of joint plane angle. With the increase of stress, the stress-strain curve shows multiple fluctuations, indicating that the specimen occurs multiple slip-stable phenomena during the loading process. With the increase of the angle, the multiple cracks of the specimen gradually merge, and the cracks are always vertical to the joint plane, showing splitting failure. As the roughness of the joint plane increases, the possibility of the joint plane sliding becomes smaller, and the splitting mode of the specimen develops from multiple fractures to a single fracture. As the strength of the surrounding rock increases, the slope of the stress-strain curve gradually increases, and the splitting mode develops from a small number of single splits to multiple splitting penetration failures. The increase of the confining pressure significantly improves the failure strength of the specimen, and the crack number of the damaged specimen also increases significantly. The research results provide theoretical support for scientific analysis of the stability of underground engineering under the disturbance of fissures or faults.

Letter to the Editor Regarding Comments on "The Correlation Between Facet Tropism and Intervertebral Disk Herniation in the Subaxial Cervical Spine" by Wang et al.

TO THE EDITOR: Letter to the Editor Regarding Comments on “The Correlation Between Facet Tropism and Intervertebral Disk Herniation in the Subaxial Cervical Spine” by Wang et al The article entitled “The correlation between facet tropism and intervertebral disk herniation in the subaxial cervical spine” written by Wang et al1 caught us with great interest. The authors performed a retrospective case-control study and found that the facet tropism on the sagittal, axial, and coronal planes are all associated with cervical disk herniation in the subaxial cervical spine. In addition, the side of greater facet angle did not affect the side of herniation. The manuscript is well organized. We appreciate their contribution to this important topic while we would like to communicate with the authors to address some concerns related to the methodology. The cervical facet joints play important roles in the spine motion and load transmission with complex anatomical structure.2 The shape and inclination of the facet joints are not regular and the surfaces are not genuinely planar.3,4 Thus, it may be difficult to describe the three-dimensional orientation of the facet joint planes accurately by drawing lines on two-dimensional images, especially considering the oblique position of the cervical facet joints.5 For all participants, the authors measured the facet angles on axial, sagittal, and coronal planes of computed tomography images. The facet angle was defined as the angle downward between the facet line and midsagittal line in the axial or coronal plane and the closed angle between the facet line and the endplate line in the sagittal plane. According to the definition, the two lines of the facet angle in the coronal and sagittal planes are in two different planes. Although this method is simple, it could be inaccurate. Given the anatomical feature of the facet joints, the orientation would be different if measured on different positions.4 As shown in Figure 1 (Supplemental Digital Content 1, https://links.lww.com/BRS/B916), the measurements are taken from three different positions on the reconstructed computed tomography scan images of the same facet joints. In the sagittal plane, the facet orientation is 58.63° (Figure 1B, Supplemental Digital Content 1, https://links.lww.com/BRS/B916), 51.74° (Figure 1C, Supplemental Digital Content 1, https://links.lww.com/BRS/B916), and 47.65° (Figure 1D, Supplemental Digital Content 1, https://links.lww.com/BRS/B916) in three consecutive images; in the axial plane, the facet orientation is 101.05° (Figure 1F, Supplemental Digital Content 1, https://links.lww.com/BRS/B916), 102.33° (Figure 1G, Supplemental Digital Content 1, https://links.lww.com/BRS/B916), and 100.35° (Figure 1H, Supplemental Digital Content 1, https://links.lww.com/BRS/B916) in three consecutive images; in the coronal plane, the facet orientation is 73.08° (Figure 1J, Supplemental Digital Content 1, https://links.lww.com/BRS/B916), 78.78° (Figure 1K, Supplemental Digital Content 1, https://links.lww.com/BRS/B916), and 80.25° (Figure 1L, Supplemental Digital Content 1, https://links.lww.com/BRS/B916) in three consecutive images. Our previous study4 adopted a three-dimensional method to calculate the facet orientation. The space vector was obtained after the reconstruction the three-dimensional model. Then, the facet angle was calculated by the formula of vector and cosine function. Accurately measuring the facet joint angle is clinically significant in elucidating the relationship between facet orientation and cervical spine degeneration. Hence, a more precise and comprehensive measurement is needed to avoid possible measurement bias. We analyzed the data from a cohort of 100 patients with cervical spondylosis.6 The preliminary results showed no significant relationship between facet tropism and cervical disk degeneration. Many factors might contribute to the degeneration of the intervertebral disk. We suspect the facet tropism might play a role in disk degeneration, but not in a significant way. A prospective cohort study might be a better way to elucidate the cause-and-effect relationship between facet tropism and disk degeneration. We are expecting to further interesting and instructive research about the cervical facet joints from the authors in the future.