Natural Joint Research Articles

Quantitative description of the joint surface roughness considering the influence of shear direction

The joint surface roughness in consideration of the influence of shear direction is quantitatively described. A natural joint produced by Brazilian splitting test is scanned, a digital elevation model that represents the morphological features of the joint is established. The two-dimensional roughness of joint profiles along the shear direction is analysed according to the parameters of root mean square (Z2), joint roughness coefficient (JRC) and the statistical characteristics of dip angles, respectively. It is proved that the standard deviation of dip angles is linearly correlated with the value of JRC2D. Further, the probability distribution of apparent dip angles along the shear direction is introduced to describe the shear-related three-dimensional joint roughness. Based on the scanning images of the joint morphology, the probability distribution of apparent dip angle varies with different shear directions.

Method for calculating the shear strength of rock masses with different combined structural planes based on the 3D printing technology

The mechanical behavior of rock masses with different combined structural planes is poorly understood because of the difficulties associated with the performance of rock observations and analyses from the surface, collection of samples during field investigations, specimen preparation, and laboratory tests. The combination of rock mass structural planes has a significant effect on the rock mass mechanical properties. The three-dimensional (3D) printing technology can conveniently create 3D entities with complex structures, thereby providing an unprecedented opportunity to break through this bottleneck. In this study, model samples of structural surface models with different combinations are printed using the 3D printing technology, and a cement slurry with 3:1 water–cement ratio is used as the structural body to produce rock masses with different combined structural planes. The method replicates well the morphological features of natural joints. Moreover, the shear properties and the failure characteristics are stable and consistent. Direct shear tests are also performed on the rock masses of different combined structural planes from the intersection line parallel and perpendicular to the structural planes to obtain the relevant mechanical parameters and rock mass failure modes. The results prove the feasibility of the 3D printing technology in the experimental study of rock mass mechanics and show that the strength and failure modes of rock masses with different combined structural planes are different. A calculation method for the shear strength of rock masses with different combined structural planes is proposed herein based on the experimental data and the Mohr–Coulomb theory, and the method’s feasibility is verified by several examples.

Kinematics after Syndesmotic Injury: Assessing the Magnitude of Talus and Fibula Rotation and Displacement

Category:Ankle; Sports; OtherIntroduction/Purpose:High ankle sprains, or injuries to the distal tibiofibular syndesmosis, are predictive of long-term ankle dysfunction. Our objectives were to evaluate ankle mortise stability, radiographically, and kinematically, using a cadaveric model with a simulated syndesmotic injury. We also measured the ability of a suture-button system to restore natural joint motion.Methods:Eight cadaveric specimens underwent serial sectioning of the anterior-inferior tibiofibular (AITFL), interosseous (IOL), posterior-inferior tibiofibular (PITFL), and deltoid ligaments. Specimens underwent external rotation and lateral translation testing after ligament release to obtain kinematic data (using a validated infrared LED motion capture system) and radiographic measurements. We then repeated external rotation and lateral translation testing after implementing a suture-button system. Repeated measures ANOVA with a Bonferroni/Dunn post-hoc test calculated the interspecimen comparisons.Results:Sectioning of each ligament, beginning with the AITFL, significantly increased talar external rotation. After releasing the AITFL and IOL, fibular external rotation increased significantly. Posterior displacement of the fibula began following the release of AITFL. Significant radiographic widening of the medial clear space and the syndesmosis occurred only after the release of the deltoid ligament. Syndesmotic and medial clear space widening was not significantly different from the intact state under lateral translation until after the release of the deltoid ligament. Placement of the suture-button system successfully reduced the medial clear space but was unable to restore the native stability of the ankle joint.Conclusion:This project addresses rotational and kinematic changes in the ankle after syndesmotic injury by quantifying the effect of ligamentous disruption on the tibiotalar articulation. The change in joint kinematics may explain why patients with moderate-to-severe syndesmosis injuries take longer to heal and develop long-term dysfunction. Significant talar rotation and posterior fibular displacement occur during external rotation, even with moderate syndesmosis injury, and before the disruption of the deltoid ligament. Stress radiography does not appear to be a reliable indicator of mild or moderate syndesmosis injuries.

MotioNet

We introduce MotioNet , a deep neural network that directly reconstructs the motion of a 3D human skeleton from a monocular video. While previous methods rely on either rigging or inverse kinematics (IK) to associate a consistent skeleton with temporally coherent joint rotations, our method is the first data-driven approach that directly outputs a kinematic skeleton, which is a complete, commonly used motion representation. At the crux of our approach lies a deep neural network with embedded kinematic priors, which decomposes sequences of 2D joint positions into two separate attributes: a single, symmetric skeleton encoded by bone lengths, and a sequence of 3D joint rotations associated with global root positions and foot contact labels. These attributes are fed into an integrated forward kinematics (FK) layer that outputs 3D positions, which are compared to a ground truth. In addition, an adversarial loss is applied to the velocities of the recovered rotations to ensure that they lie on the manifold of natural joint rotations. The key advantage of our approach is that it learns to infer natural joint rotations directly from the training data rather than assuming an underlying model, or inferring them from joint positions using a data-agnostic IK solver. We show that enforcing a single consistent skeleton along with temporally coherent joint rotations constrains the solution space, leading to a more robust handling of self-occlusions and depth ambiguities.

Model Test Study on Seepage of Jointed Loess

This paper focuses on the influence of joints on seepage capacity of a soil mass, the water infiltration range, the area of the wet zone, and water content distributions. Tests were performed using a self-designed seepage device to determine the hydraulic conductivity of loess samples with natural joints. The test results indicate that joints greatly improve the seepage capacity of a soil mass; the depth and quantity of infiltration for the jointed sample are larger than those for the intact sample. The infiltration depths of the jointed sample are about 2.6 times that of intact specimens, and the measured areas of wet zones of the jointed sample are about 2.2 times that of an intact sample. Due to the existence of the joint, higher water content is observed at the joint location. In comparison, the water content distributions are relatively horizontal for the intact sample.

Preliminary Results From a US Clinical Trial of a Novel Synthetic Polymer Meniscal Implant.

Background:At least 760,000 outpatient meniscectomies are performed in the United States each year, making this the most common musculoskeletal procedure. However, meniscal resection can alter the joint biomechanics and overload the articular cartilage, which may contribute to degenerative changes and the need for knee replacement. Avoiding or delaying knee replacement is particularly important in younger or more active patients. Synthetic meniscal implants have been developed in an attempt to restore the natural joint biomechanics, alleviate pain and disability, and potentially minimize degenerative changes in patients who require meniscectomy.PurposeTo evaluate the preliminary results from 2 ongoing trials that are evaluating the safety and effectiveness of a synthetic polymer meniscal implant (NUsurface; Active Implants, LLC).Study Design:Cohort study; Level of evidence, 2.Methods:This was a preliminary analysis of the first 100 patients enrolled across 2 studies for 12 months: a single-arm, intervention-only study and a randomized controlled trial comparing the investigational meniscal implant with nonsurgical therapy. There were 65 patients in the implant group (30 randomized) and 35 in the control group. Outcomes included Knee injury and Osteoarthritis Outcome Score (KOOS) and adverse events (AEs) collected at baseline and follow-up visits of 6 weeks, 6 months, and 12 months.Results:No statistically significant differences were found in baseline characteristics between the implant and control groups. At 12 months, follow-up KOOS data were available for 87% of the 100 included patients. Significantly greater improvements from baseline were observed in the implant group compared with controls in all KOOS subcomponents, except for symptoms (119%-177% greater improvement at 12 months). AEs were reported at similar rates between the 2 groups, with 12 AEs among 11 patients in the implant group (16.9%) versus 5 AEs among 5 patients (14.3%) in the control group (P = .99).Conclusion:These preliminary results suggest significant improvements in pain and function scores with the implant over nonsurgical therapy and a similar adverse event rate.

Good long-term outcomes for Direct Anterior Approach Total Hip Arthroplasty in South Africa

This study aims to assess long-term outcomes of Total Hip Arthroplasty (THA) through Direct Anterior Approach (DAA) in a developing country using traditional and novel Patient-Reported Outcomes. There were 522 patients (mean age, 56.5 years; 66.3% female) after mean follow-up 7.35 years. There were 13 revisions. Overall 5-year implant survival rate was 97.5%. Patient Joint Perception scores of 65.5% perceived a completely natural joint. Mean Hip Disability and Osteoarthritis Score was 89.1. Median Forgotten Joint Score-12 was 90 and modified Harris Hip Score was 88. Primary DAA THA in sub-Saharan Africa allows good clinical outcomes at minimum 5 years follow-up.

Scale Dependence of Waviness and Unevenness of Natural Rock Joints through Fractal Analysis

The scale dependence of surface roughness is critical in characterising the hydromechanical properties of field-scale rock joints but is still not well understood, particularly when different orders of roughness are considered. We experimentally reveal the scale dependence of two-order roughness, i.e., waviness and unevenness through fractal parameters using the triangular prism surface area method (TPM). The surfaces of three natural joints of granite with the same dimension of 1000 mm×1000 mm are digitised using a 3D laser scanner at three different measurement resolutions. Waviness and unevenness are quantitatively separated by considering the area variation of joint surface as grid size changes. The corresponding fractal dimensions of waviness and unevenness in sampling window sizes ranging from 100 mm×100 mm to 1000 mm×1000 mm at an interval of 100 mm×100 mm are determined. We find that both the fractal dimensions of waviness and unevenness vary as the window size increases. No obvious stationarity threshold has been found for the three rock joint samples, indicating the surface roughness of natural rock joints should be quantified at the scale of the rock mass in the field.

Bio-inspired surface modification of PEEK through the dual cross-linked hydrogel layers

The biocompatible high-performance material PEEK (polyetheretherketone) is an attractive implant material, however, its hydrophobicity and high friction coefficients severely hinder its biomedical applications. Thus, it is inferred from the recent advances in surface modification technology, achieving the biomimetic natural joint lubrication systems on PEEK still remains a challenge. In view of the above, herein we proposed a novel two-step strategy to fabricate a “soft (dual cross-linked hydrogel) layer-hard (PEEK) substrate” texture that mimics the structure and function of soft cartilage on the hard basal bone in joints. At first, a layer of acrylic acid-co-acryl amide (AA-AM) hydrogel is anchored to the PEEK substrate through UV-initiated polymerization. In the second step, hydrogel coated PEEK substrate is immersed in ferric nitrate solution to create the secondary cross-linkage between Fe3+ and –COOH groups in the hydrogel. As a result, the consequential top-coat hydrogel layer not only transforms the surface wettability (hydrophobic to hydrophilic) but also provides scratch resistance to the underlying PEEK substrate. The modified specimens display low friction coefficients in water under different load conditions. In addition, the obtained surface exhibits a certain self-repairing ability due to its unique physically reversible network structure. Therefore, this work provides a promising strategy for broadening the use of PEEK in orthopedic implants.

Research on Shear Behavior and Crack Evolution of Symmetrical Discontinuous Rock Joints Based on FEM-CZM

The discontinuous joints are an essential type of natural joints. The normal force, joint persistency, and distribution exert great influences on the shear resistance of the rock joints. By simulating the uniaxial compression experiment and Brazilian test, the material parameters and the basic size standard for meshing were determined. The symmetrical discontinuous joint distribution of three types were established, the cohesive elements were inserted between the solid elements, and the numerical simulation of the shear test was conducted. The effects of joint distribution, joint continuity, and normal stress on the shear resistance of joint rock were investigated, and the law of crack evolution was analyzed. The results showed that the shear process of discontinuous joints can be divided into four stages: elastic stage, strengthening stage, plastic stage, and residual stress stage. For the scattered joint distribution, the rock bridge can provide more reinforcement for the joints, which enhances the shear resistance of the joints, the stress concentration point at the end of the joint is easy to accumulate more fracture energy, which induces the initiation of the cracks, and under the influence of unbalanced torque, the both-sided joint distribution is more likely to produce tension damage.

A new joint morphology parameter considering the effects of micro-slope distribution of joint surface

An accurate description of the morphology of a joint surface is necessary to interpret its shear behavior. Accurately distinguishing the shear behavior differences may be difficult if the defined morphology parameter ignores the micro-slope distribution of the joint surface. The initial climbing angle was therefore defined and used to characterize the micro-slope distribution of the ascent section of joint profile, and a new method was proposed for calculating the morphology parameter, M. The parameter M embodies anisotropy, and the values of M for all profile lines, which are selected on the same joint at equal intervals in one direction, are log-normally distributed. To study the mechanical effects of M, joint replicas with three different strengths were 3D-printed using the scanned point cloud information of the natural joint. An anisotropic direct shear test was conducted to obtain the joint shear parameters in eight directions. The results indicated that the new morphology parameter accurately reflects the anisotropic shear behavior of the joint, and displayed tangential, positive linear, and power relations with shear strength, apparent cohesion, and friction angle, respectively. Furthermore, an index for evaluating the shear failure characteristics, established by using the new morphology parameter, can effectively distinguish the differences between the climbing and shear-off behavior on the joint. The parameter M, which considers the micro-slope distribution, can thus correctly represent the physical and mechanical properties of a joint, and its application is conducive to the precise quantification of joint shear behavior.

Rationale of kinematic alignment

Kinematic alignment is aphilosophy for individual knee prosthesis implantation in athree-dimensional view. The key of the concept is to understand the femoral flexion-extension axis as the centre of acylinder within the posterior condyles. This axis defines the knee in three dimensions over the entire range of motion. The tibia follows the femur, is balanced on the knee in extension and flexion, and shows individual laxities in flexion and deep flexion. As aconsequence, limbs will be reconstructed along their constitutional leg axis, which in most patients is different to astraight hip-knee-ankle centre axis. The method aims at perfectly reconstructing the natural joint lines, which in many patients leads to the natural oblique joint lines. This results in considerable advantages, as the natural stability of the knee is restored, and native patella kinematics are maintained. From astatic view, polyethylene and the implant-bone interface may be vulnerable to mechanical overloading due to altered adductor moments. However, agrowing body of evidence shows that naturally oriented knee joints show a more balanced loading pattern. Moreover, dynamic gait patterns actually show the mechanism of even reduced knee adductor moments, explaining the clinical results of up to 10years follow up.

A New Representative Sampling Method for Series Size Rock Joint Surfaces

The greatest variability in both shear strength and roughness exists for joint samples with smaller size, which underscores the necessity of performing representative sampling. This study aims to provide a representative sampling method for series size joint surfaces. The progressive coverage statistical method is introduced to provide the sufficient sample capacity for series sampling sizes by setting different propulsion spaces. The statistical law of the joint surface morphology at different sampling sizes is measured by the 3D roughness parameter with {{theta }}_{max }^{ast }/({C}+1). Through an application in nine natural large-scale rock joints, nine consecutive sampling sizes from 100 mm × 100 mm to 900 mm × 900 mm are selected and 121 samples are successfully acquired from each sampling size. According to the frequency distribution of roughness statistics, a new sampling method combining the layering principle and K-medoids clustering algorithm is proposed to screen representative joint samples for each sampling size. The sampling results that meet the test accuracy requirements suggest the possibility of realizing an intelligent sampling method. In addition, the representative of the interlayer cluster center is validated. Finally, the comparison results with the traditional stratified sampling method prove that the proposed method has better stability.

Tribological properties of hierarchical structure artificial joints with poly acrylic acid (AA) - poly acrylamide (AAm) hydrogel and Ti6Al4V substrate

Natural joints have the hierarchical structure of bone and cartilage, providing excellent lubrication and load-carrying capacity. In our research, the hierarchical structure artificial joints of Poly Acrylic Acid (PAA)- Poly Acrylamide (PAAm) hydrogel coating and Ti6Al4V substrate were formed using a simple yet versatile method by mimicking the hierarchical structure of natural joints. The efficient lubrication at friction interfaces was achieved. The composition and microstructure were confirmed by Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM). The hydrogel coatings were successfully prepared on the surface of Ti6Al4V substrate through the adsorption of the charged group. This hierarchical structure material exhibits the lower dynamic friction, approximately 0.085, which is much lower than bare Ti6Al4V, about 0.429. The wear on the surfaces after the tribological experiment is super-shallow and has no significant fracture area around the scratch. The PAA-PAAm hydrogel has a more uniform and compact cross-linked network porous structure, and the porous size is much smaller than PAA hydrogel. The cross-linked network porous structure is the main factor accounting for the low dynamic friction. This hierarchical structure of soft and hard improve the load-carrying ability and has the potential uses in artificial joints.

A Novel Pantographic Exoskeleton Based Collocated Joint Design With Application for Early Stroke Rehabilitation

Motivated by the need to develop safe exoskeletons for collocated joint rehabilitation during the early stage of stroke recovery, this article presents a pantographic exoskeleton (PGE) capable of multi-degree-of-freedom motions in a single-joint collocated with the impaired joint. With minimum internal joint reactions in the presence of misalignment, the PGE “traces” the natural joint motion “like a pantograph” in the sagittal plane while performing in-bed rehabilitation, from which the joint parameters can be estimated for subsequent patient-specific motion training. An analytical model is presented to provide a rational basis for designing a collocated human-ankle/PGE mechanism, which has been numerically illustrated. The findings demonstrate that because the PGE joint do not restrict human ankle nature motion within the motion range of a typical ankle, it is less sensitive to joint misalignment as compared to conventional multijoint serial mechanisms that form a closed chain with the human limbs/joint. A prototype PGE has been designed; and its effectiveness for collocated ankle-joint manipulation has been experimentally investigated. Unlike conventional imaging methods that are prone to skin-marker errors and dependent on lumped-parameter approximations, the PGE directly measures the talus trajectory of the ankle-joint for characterizing its roll/slide motion and internal parameters.

Optimalisasi Leadership dan Sarana Belajar Sebagai Pilar Pendidikan Sekolah Alam Melalui Inisiasi Outbound di Sekolah Alam Rumbai Pekanbaru

One of the shortcomings in the implementation of education in schools is the lack of a forum that can facilitate student leadership which is integrated with learning in the Classroom. In general, Leadership is carried out in extracurricular activities in schools. The implementation of Leadership training has limited time in its implementation and is felt to be less than optimal. Leadership is separate from student learning activities. UMRI has experts in the field of Science (IPA) and Education under the auspices of the Faculty of Teacher Training and Education and the field of Technology Design under the auspices of the Faculty of Computer Science who can contribute their knowledge to the Leadership optimization program and the means of learning together with nature through outbound initiation at the Rumbai Nature School. The main activity that would be carried out in this program is to design and create an integrated outbound facility with the Natural Joint Learning facilities in the Sekolah Alam Rumbai environment. The output that is expected to be generated from this activity is the availability of integrated outbound facilities to support Leadership through outbound and scientific logic through Student Learning Together Nature can be optimized.

The Effect of Working Parameters upon Elastohydrodynamic Film Thickness Under Periodic Load Variation

There are a number of widely used machine components, such as rolling element bearings, gears and cams, which operate in the lubrication regime known as Elastohydrodynamics (EHD), where lubricant film thickness is governed by hydrodynamic action of convergent geometry, elastic deformation between non-conformal contacting surfaces, and the increase of lubricant viscosity with pressure. Variable loading conditions occur not only in all the machine components mentioned above, but also in natural joints such as hip or knee joints of humans or many vertebrates. Experimental studies of the behaviour of EHD films under variable loading are scarce and to authors’ knowledge systematic studies of the evolution of lubricant film thickness in EHD contacts subjected to forced harmonic variation of load are even less common. The aim of the present study is to explore the effect of load amplitude on the EHD film behaviour. This is done in alternating cycles with the load varying about a fixed, preset value at various amplitudes. Experimental results are compared with a simple theoretical analysis based on the speed of change of contact’s dimensions, a semi-analytical solution which includes both speed variation and squeeze effect, and finally with a full numerical solution.

Compliant Mechanism as a Motion-Preserving Artificial Spinal Disc: A Novel Concept

Abstract Investigations of spinal disc replacement options have been conducted for several decades but, as yet, the suggested solutions have not been proven to correctly preserve the natural joint motion. This paper focuses on a new structure of an artificial intervertebral disc joint that closely supports a close-to-natural three-dimensional motion of two adjacent vertebrae. The disc design is based on a passive parallel mechanism, with different stiffnesses for each link. Optimization of the artificial disc dimensions and link stiffnesses enabled convergence of the finite screw axis (FSA) of the artificial disc joint with that of a natural disc. As a result, the natural motion of the spine vertebrae was maintained and the loads on the facet joints minimized. The mechanism design was optimized, built, tested, and proven to be a feasible artificial disc with natural motion preservation characteristics.

Cartilage matrix-inspired biomimetic superlubricated nanospheres for treatment of osteoarthritis

The superlubrication of natural joint has been attributed to hydration lubrication of articular cartilage. Here, inspired by the structure of phosphatidylcholine lipid (a typical cartilage matrix) with the presence of zwitterionic charges, we developed superlubricated nanospheres, namely poly (2-methacryloyloxyethyl phosphorylcholine)-grafted mesoporous silica nanospheres (MSNs-NH2@PMPC), via photopolymerization. The biomimetic nanospheres could enhance lubrication due to the formation of a tenacious hydration layer surrounding the zwitterionic charges of polymer brushes (PMPC), and achieve local delivery of an anti-inflammatory drug employing the nanocarriers (MSNs). The tribological and drug release tests showed improved lubrication and sustained drug release of the nanospheres. Additionally, the in vitro and in vivo tests revealed that the superlubricated drug-loaded nanospheres inhibited the development of osteoarthritis by up-regulating cartilage anabolic components and down-regulating catabolic proteases and pain-related gene. The nanospheres, with an integrated feature of both enhanced lubrication and sustained drug delivery, can be an efficient intra-articular nanomedicine for the treatment of osteoarthritis.

Compliant-poroelastic lubrication in cartilage-on-cartilage line contacts

ABSTRACT The mechanisms of friction in natural joints are still relatively unknown and attempts at modelling cartilage-cartilage interfaces are rare despite the huge promise they offer in understanding bio-friction. This article derives a model combining finite strain, porous and thin-film flow theories to describe the lubrication of cartilage-on-cartilage line contacts. The material is modelled as compliant and poroelastic in which the micro-scale fibrous structure is interstitially filled with synovial fluid. This fluid flows over the interface between the bodies and is coupled to pressure generated by relative motion in the thin-film region formed under load. A Stribeck analysis demonstrated that this type of contact is determinable to conventional elastic lubrication but that the friction performance is improved by this interfacial flow. Moreover, the inclusion of periodic flow conditions when contact is onset is a specific novelty which elucidates new observations in the lubrication mechanisms pertaining to natural joints.