Experimental Study on Influence of Joint Surface Morphology on Strength and Deformation of Nonthrough Jointed Rock Masses under Direct Shear

Direct shear tests were carried out on nonthrough jointed rock masses (NTJRM) with three types of joints under five normal stresses. The strength characteristics of shear strength, initial crack strength, and residual strength and the deformation characteristics of tangential displacement and dilatancy displacement as well as the transformation of failure mode and the variation of shear parameters of rock mass with different joint morphology are studied. Under the same normal stress, with the increase of joint undulation, the shear strength of NTJRM increases, and the corresponding tangential displacement of NTJRM increases. Two typical failure modes are observed: TTTS mode and TSSS mode. TTTS model indicates that the initial failure, extension failure, and final failure of rock mass are caused by tensile action, while the failure mode of through plane is formed by shear action. The initial failure of TSSS mode rock mass is caused by tensile action, while the expansion and final failure are caused by shear action, and the failure mode of through plane is formed under shear action. When the joint undulation is small and the normal stress is small, NTJRM will fail in TTTS mode; when the joint undulation is large and the normal stress is large, NTJRM will fail in TSSS mode. The results show that the shear parameters of NTJRM are related to the joint morphology, the bond force increases with the increase of joint undulation, and the internal friction angle increases with the increase of joint undulation. The research results of direct shear test of nonthrough jointed rock mass can provide reference for related research.

The Short-Term Effect of Active Skeletonized Sutural Distractor Appliance on Temporomandibular Joint Morphology of Class III Malocclusion Subjects

Objectives The purpose of this study was to evaluate the short-term effect of active skeletonized sutural distractor (ASSD) appliance on temporomandibular joint morphology of class III malocclusion subjects. Materials and Methods This was a prospective interventional study. Cone-beam computerized tomography (CBCT) images of 22 patients were taken before and after treatment by using Planmeca Promax 3D CBCT machine version 2.9.2 (Planmeca OY Helsinki, Finland). The condylar width, height, length, roof of glenoid fossa thickness, and all joint spaces were measured. The condylar position was determined based on Pullinger and Hollander formula. The condylar shape was determined as per Kinzinger et al. The condylar volume was calculated by using Mimics software (Materialize, Belgium). Statistical Analysis Data analysis was performed by using SPSS software version 24. Wilcoxon paired signed-rank test was used to compare the difference in temporomandibular joint morphology and condylar volume between pre- and post-treatment measurements. Chi-square test was used to compare the condylar position and shape. Results The superior (p = 0.000 on the right side, p = 0.005 on the left side) and posterior joint spaces (p = 0.000 on both sides) were decreased after the treatment, respectively. The condyles were rotated upward and backward, thereby increasing the anterior joint spaces (p = 0.000 on both sides) after the treatment. The condylar volume increases after treatment, but no significant differences were observed (p = 0.903 on the right side, p = 0.062 on the left side). Conclusion The significant changes were observed in joint spaces. The condyles were more anteriorly placed before treatment. Condylar position and shape alter in response to ASSD treatment. The condylar volume did not show any significant change.

Implications of the Overlapping Degree Between Proximal Fibula and Tibia for Placing the Optimal Syndesmotic Screw: A Virtual Cadaveric Study

Background: To determine the optimal direction of the syndesmotic screw and introduce a consistent landmark for practical application by analyzing three-dimensional (3D) modeling and virtual implantation.Methods: A total of 102 cadaveric lower legs (50 males and 55 females, average height of 160.6 ± 7.1cm) were used to reconstruct a 3D model by using the Mimics® software and the joint morphology was evaluated. Syndesmotic cylinders (Ø3.5 mm/Length 100 mm) were transversely placed in the proximal end of the incisura fibularis for simulating screw fixation. The tibial proximal cylinder, which was tangent to the posterior tibial condyles, was traced and the angle between the two cylinders was measured as the tibial torsion angle (TTA). After rotating the syndesmotic cylinder parallel to the ground, the overlapping degree between the proximal fibula and tibia were assessed as a radiologic indicator. Results: Concerning tibial torsion, the TTA was an average of 36.7° (range, 17.2°–54.4°, SD 8.78) When the syndesmotic cylinder was rotated to be parallel to the ground, the proximal fibula had non- or linear overlap with the lateral border of the tibia, regardless of the joint morphology. In this nonoverlapping view, compared to the mortise view, the three criteria for normal fibular length could be better visualized. Conclusion: The syndesmotic cylinder in the proximal end of the incisura fibularis could be consistently placed parallel to the ground by internally rotating the tibia until there was a non- or linear overlap between the proximal fibula and the tibia, regardless of the joint morphology.

Bilateral Sacroiliac Joint Fusion: A Case Report

Sacroiliac (SI) joint is the articulation which forms the part of the bony pelvis. It plays an important role in locomotor activity, and childbirth during labour. It helps in the transmission and distribution of axial body weight from the spine to the pelvis. This synovial joint exhibit limited gliding movements within the joint cavity. About 15-30% of low backache aetiologies are attributed to SI joint dysfunction. People who are overweight, have co-morbid conditions, and pregnant women are at higher risk of developing vertebral joint deformities called spondylarthropathies. They are group of inflammatory disorders which are involving the vertebral spines and peripheral joints, where the symptom of stiffness is prominently seen. The anatomical variations in the SI joint morphology like accessory SI joint, iliosacral complex and sacral defect, dismorphic joint, are of compelling interest concerning SI joint pathologies from the orthopaedic viewpoint. This case report presents a bilateral fusion of SI joint, found in a skeleton in the museum of medical college.

Endocranial morphology of the petalichthyid placoderm Ellopetalichthys scheii from the Middle Devonian of Arctic Canada, with remarks on the inner ear and neck joint morphology of placoderms

Petalichthyid and “acanthothoracid” placoderms have taken pivotal positions in the debate on placoderm — and, by extension, jawed vertebrate — relationships owing to perceived similarities with certain jawless vertebrates. Neurocranial characters are integral to current hypotheses of early gnathostome relationships. Here, we describe the three-dimensionally preserved neurocranial anatomy of the petalichthyid placoderm Ellopetalichthys scheii (Kiær, 1915), from the Middle Devonian (early Eifelian) of Ellesmere Island, Canada. Using X-ray computed microtomography, we generated three-dimensional reconstructions of the endocranial surfaces, orbital walls, and cranial endocavity. These reconstructions verify the absence of a crus commune of the skeletal labyrinth and the complex shape of the petalichthyid endolympathic duct. Details of the craniothoracic joint and occipital musculature fossae help resolve the problematic comparative anatomy of the occipital surface of petalichthyids. These new data highlight similarities with arthrodire placoderms, consistent with older hypotheses of a sister-group relationship between petalichthyids and that clade.

Characterization of rock joint surface anisotropy considering the contribution ratios of undulations in different directions

Anisotropy in rock joint is strongly dependent on undulating surface morphology. Recent research of the morphology showed the parameter can express the different types of anisotropic characteristics of the joint surface separately. This report aims to analyze the common characteristic of the anisotropic distribution and exhibit the anisotropic variation trend. The joint morphology function consists of two morphology functions of regular plane in orthogonal directions, and the anisotropic variation determined by the contribution ratios of the two morphology. The roughness weight ratio in orthogonal direction of joint surface is used as an index to describe the anisotropic variation behavior, which proposes the anisotropic variation coefficient (AVC). On this basis, it is divided into 5 levels from strong anisotropic to isotropic. According to the assumption of anisotropic arc distribution, the anisotropic analytic function is derived and the agreement between the deduced curves and measured data therefore suggests the possibility of defining the morphology anisotropy through the index AVC. Finally, we verify the characteristic of three natural rock joints, and prove the proposed function can reflect the anisotropic distribution trend. The new index can be used to describe the anisotropic variation behaviour of rock joint surfaces.