Joint Orientation Research Articles

Decade-Wise Computed Tomography-Based Morphometric Measurements of a Single Lumbar Spinal Motion Segment L4-5.

A spinal motion segment comprises facet joints and intervertebral disc. A complex interplay of biomechanical factors occurs between them with degeneration giving rise to numerous pathological conditions. We conducted a study to find a correlation between facet joint orientation and intervertebral discs with age. A cross-sectional study of 203 consecutive subjects undergoing a computed tomography scan of abdomen and pelvis were included. Subjects were divided into 5 groups based on age (group I: 18-30 years; group II: 31-40 years; group III: 41-50 years; group IV: 51-60 years; group V: 61-70 years). Using 3-dimensional reconstruction images, orientation of lumbar facet joints at the L4-5 level was measured. Similarly, adjacent disc heights at L3-4 and L4-5 were measured and their ratio was documented. The study included 106 males and 97 females. A positive correlation was noted between age and sagittal facet orientation until age 60 years. However, after age 60 years, a negative correlation with age was seen, which was statistically significant. Similarly, the disc height ratios show a progressive decline in their values with age. However, this decline was statistically significant only after age 60 years. The gradual change of facet joint orientation from sagittal to coronal as the age crosses from 30 to 60, to beyond 60, with a simultaneous and parallel diminishing in the disc height probably is one of the attributes of the phenomenon of autostabilization of a motion segment.

Is Transoral Surgery Still a Relevant Procedure in Atlantoaxial Instability?

The treatment of atlantoaxial instability (AAI) involves stable fixation and fusion with adequate decompression of spinal cord. After the advent of the Goel posterior joint manipulation technique, most of the once irreducible atlantoaxial dislocations (AAD) could be reduced and the need for transoral odontoidectomy became almost nil. Here we tried to iterate the indications of anterior transoral odontoid surgery for AAI in the current scenario. A retrospective study compiling the clinical, radiological, and surgical characteristics of 6 cases (5 scenarios). These patients underwent anterior transoral surgery alone or in combination with a posterior approach. Two patients had a well-formed occipito-cervical fusion mass, with a displaced odontoid and unreduced C1-C2 joint causing cervical myelopathy. A middle-aged woman presented with unreduced AAD following failed C1-C2 joint distraction technique. A displaced dystopic os odontoideum ossicle was found in an adolescent boy, prohibiting the reduction of AAD. A young man had displacement of the fractured odontoid segment with intact transverse alar ligament and C1-C2 joint complex. One patient had a rare scenario of abnormal orientation of the C1-C2 joint. All 6 patients were successfully treated with adequate spinal cord decompression achieved by the anterior transoral route and stabilization by either the anterior approach itself or in combination with posterior surgery. All had significantly better postoperative outcomes except for 1 patient who expired due to poor respiratory reserve. We tried to emphasize the indications for using transoral anterior odontoid surgery over the posterior approach in the management of AAI. This will prevent the surgical technique of anterior odontoidectomy from becoming an obsolete procedure in the current practice.

Preoperative Planning for the Foot and Ankle: A Technique Tip

Category:Other; Ankle; Midfoot/ForefootIntroduction/Purpose:Computed tomography (CT) advanced imaging techniques are a valuable tool for orthopedic surgeons when evaluating complex foot and ankle pathology. With advances in CT data processing, surgeons can create custom reformation of the imaging data in real time using postprocessing imaging tools. This article presents a technique describing how to manipulate CT data using two of these tools, multiplanar reformation (MPR) and maximal intensity projection (MIP), to better visualize pathology and allow a more definitive diagnosis preoperatively. Despite their availability on most modern picture archiving and communication systems, most surgeons across orthopaedics disciplines fail to utilize these powerful tools.Methods:Patients with complex midfoot deformities underwent CT scans for diagnosis and preoperative planning. Case 1 underwent percutaneous pinning of multiple metatarsal fractures. Post-operatively she had severe pain localized to the second and third metatarsals. A CT scan obtained in standard axes failed to interpret the multiplanar deformities when viewed initially on PACS. Using MPR/MIP, the axes were rotated to generate a detailed view of the deformities and subsequently template osteotomies. Case two underwent arthrodesis of the second and third tarsometatarsal (TMT) joints for an unstable Lisfranc injury. Post-operatively she presented with severe midfoot pain prohibiting her return to athletics. Radiographs demonstrated normal alignment with hardware obscuring the joints. Standard CT axes were difficult to interpret due to metal artifact and oblique planes of the TMT joints. MPR/MIP reformatting allowed metal artifact reduction through axes adjustment, improving visualization and facilitating diagnosis of nonunion of the second and third TMT fusions.Results:Case One:MIP/MPR allowed manipulation of the CT scan in the axial and coronal planes provided a sagittal reformat of the entire second and third metatarsals. The second metatarsal had a gradual plantarflexion malunion of the diaphysis. The third metatarsal had an acute plantarflexed deformity of the metatarsal neck. Reformatting provided an accurate preoperative template for planned dorsiflexion osteotomies. Case Two: Metal artifact and the oblique orientation of the TMT joints prevented evaluation of previous fusions. MIP/MPR reformatting provided axes which were perpendicular to the TMT joints decreased metal artifact and demonstrated nonunion of the previous fusions. Use of MIP/MPR in this case provided valuable diagnostic information regarding the source of pain and a plan for removal of hardware and revision TMT fusions.Conclusion:The MPR/MIP function is available in most PACS systems and allows customizable CT reformats. The technique is easy to learn and can be done quickly in the office or pre-operative setting. The technology has facilitated streamlined pre- operative planning and improvements in injury visualization numerous times, particularly in complex deformities and trauma. Using MIP/MPR reformats, the authors have been able to identify critical fracture lines and relationships between anatomic structures which may otherwise have been missed or less precisely understood. The authors hope that this article will enhance awareness and encourage others to utilize this powerful technology.

A shear strength model for anisotropic blocky rock masses with persistent joints

The Mohr-Coulomb (MC) shear strength parameters, cohesion c and angle of friction φ, are required in numerical models. Currently, the geological strength index (GSI) system has been widely used for estimating shear strength of blocky rock masses in rock engineering. However, the GSI system does not include the effect of joint orientation β on the mechanical properties of a rock mass, which means that the shear strength model cannot reflect anisotropic rock mass strength behavior caused by joint orientation. In this research, UDEC-based synthetic rock mass models, which are calibrated by experimental data, are adopted to study the effect of joint orientation on the shear strength of blocky rock masses with two perpendicular joint sets. The values of cohesion c and angle of friction φ estimated from the numerical simulation are compared with those calculated from the empirical shear strength models based on the GSI system. Comparison of the results shows that the existing empirical model overestimates the shear strength of rock mass when 10° <β < 45°, which may impose a risk on engineering design. To rectify the problem, based on the analysis of shear strength parameters of rock masses with various joint orientations, anisotropic weighting factors are proposed to modify the existing model. The proposed modified model is capable of providing conservative but more accurate estimation of the shear strength of rock mass, which is important for safe engineering designs.

Transverse jointing in foreland fold-and-thrust belts: a remote sensing analysis in the eastern Pyrenees

Abstract. Joint systems in the eastern portion of the Ebro Basin of the eastern Pyrenees enjoy near continuous exposure from the frontal portion of the belt up to the external portion of its associated foredeep. Utilizing orthophoto mosaics of these world-class exposures, we have manually digitized over 30 000 joints within a 16 km×50 km study area. The mapped traces exhibit orientations that are dominantly perpendicular to the trend of the belt (transverse) and, subordinately, parallel to the belt (longitudinal). In particular, joints systematically orient perpendicular to the trend of the belt both in the frontal folds and in the inner and central portion of the foredeep basin. Longitudinal joints occur rarely with a disordered spatial distribution, exhibiting null difference in abundance between the belt and the foredeep. Joint orientations in the external portion of the foredeep become less clustered, with adjacent areas dominated by either transverse or oblique joints. Our data indicate that joints in the studied area formed in the foredeep in response to a foredeep-parallel stretching, which becomes progressively less intense within the external portion of the foredeep. There, the minimum stress direction becomes more variable, providing evidence of the poor contribution of the forebulge-perpendicular stretching on stress organization.

Indexing the engineering properties of residual soils in the southern slopes of Mashhad, NE Iran

Residual soils are weathering products of rocks that are commonly found under unsaturated conditions. The properties of residual soils are a function of the degree of weathering. A series of index properties, engineering properties and geophysics survey examinations were performed on residual soils from two major geological formations in Iran. In the present research, the index properties of residual soils in the south of Mashhad city in Iran are investigated. Natural and artificial trenches were analyzed for evaluating the weathering profiles and collecting soil samples. Disturbed and undisturbed samples were obtained from each of the soil profile horizons resulting from weathering of different parent rocks. Subsequently, physical properties and mechanical properties of the soil samples were determined in accordance with ASTM standards. Also, the mineralogical composition, chemistry, and texture of the soil were evaluated in 51 profiles. The field observations showed the difference in the weathering profile of residual soils deposited on various rocks (igneous, sedimentary, and metamorphic). These profiles mainly consisted of two horizons including residual soil on top and saprolite at the bottom. The results of laboratory tests and geotechnical data showed that the properties of residual soil samples change by depth. Moreover, depending on the type of origin rock, the properties are different in various types of residual soils. In most of the samples, the moisture content of soil horizons was also increased by depth. Based on the unified soil classification (USCS), the soils of the upper horizons appeared to be classified as ML (Lean silt) and CL (Lean clay) while the soils of the lower horizons (saprolite zone) fall in SC (clayey sand), SM (silty sand), and SW (well-graded sand) classes. Moreover, the results demonstrated that the particle size of the soil was increased by depth. Comparison of results of the geotechnical tests showed that properties of residual soils are changed by variations of depth, weathering level, and type of parent rock. Considering the concentration of the number of lines and the concentration of the points of intersection, the length and dimension fractal of lineaments in the southeastern part of the study area, it is evident that this zone possesses weathering severity and soil thickness. Fieldwork data from this zone have also verified the severity of weathering conditions. The analysis of lineaments trends in different parts of the study area indicated that the lineaments with the NW-SE trend have a strong effect on weathering development. The weathering depth depends on the orientation of bedding joints with respect to the slope in the study area. Slope inclination and soil thickness are controlled by weathering and erosion processes.

Pathomechanisms and Predisposing Factors for Degenerative Lumbar Spondylolisthesis: A Narrative Review.

The pathomechanism of degenerative lumbar spondylolisthesis (DLS) is not fully understood and is likely to be multifactorial. The primary cause of DLS likely is age-related degeneration of all of the components of the segments and their surroundings. Subsequently, additional factors, such as anatomical, hormonal, and mechanical stress factors, may drive the spinal segments to DLS. Reported predisposing factors that have shown a consistent association with DLS include older age, female sex, sagittal facet joint orientation, and high pelvic incidence. Future prospective epidemiological studies that include large groups of subjects and use multivariate analyses of the possible predisposing factors are needed.

Correction of severe valgus osteoarthritis by total knee arthroplasty is associated with increased postoperative ankle symptoms

PurposeThe aim of this study was to assess the mid-term clinical outcome of the ankle joint after total knee arthroplasty (TKA) in high-grade valgus osteoarthritis.MethodsIn this case–control study, n = 36 patients with a preoperative mechanical tibiofemoral angle (mTFA) ≥ 15° who underwent TKA between December 2002 and December 2012 were included. The control group (mTFA < 15°) of n = 60 patients was created using case matching. Radiological [mechanical tibiofemoral angle (mTFA) and ankle joint orientation to the ground (G-AJLO)] and clinical parameters [Foot Function Index (FFI), Knee Society Score, Forgotten Joint Score, and Range of Motion (ROM)] were analysed. The mean follow-up time was 59 months (IQR [56, 62]).ResultsThe degree of correcting the mTFA by TKA significantly correlated with the postoperative FFI (R = 0.95, p < 0.05), although the knee and ankle joint lines were corrected to neutral orientations. A cut-off value of 16.5° [AUC 0.912 (0.85–0.975 95% CI), sensitivity = 0.8, specificity = 0.895] was calculated, above which the odds ratio (OR) for developing ankle symptoms increased vastly [OR 34.0 (9.10–127.02 95% CI)]. ROM restrictions of the subtalar joint displayed a strong significant correlation with the FFI (R = 0.74, p < 0.05), demonstrating that decreased ROM of the subtalar joint was associated with aggravated outcomes of the ankle joint.ConclusionsIn this study, higher degrees of leg axis correction in TKA were associated with increased postoperative ankle symptoms. When TKA is performed in excessive valgus knee osteoarthritis, surgeons should be aware that this might trigger the onset or progression of ankle symptoms, particularly in cases of a stiff subtalar joint.Level of evidenceIII.

Quantifying shortening across the central Appalachian fold-thrust belt, Virginia and West Virginia, USA: Reconciling grain-, outcrop-, and map-scale shortening

AbstractWe present a kinematic model for the evolution of the central Appalachian fold-thrust belt (eastern United States) along a transect through the western flank of the Pennsylvania salient. New map and strain data are used to construct a balanced geologic cross section spanning 274 km from the western Great Valley of Virginia northwest across the Burning Spring anticline to the undeformed foreland of the Appalachian Plateau of West Virginia. Forty (40) oriented samples and measurements of &amp;gt;300 joint orientations were collected from the Appalachian Plateau and Valley and Ridge province for grain-scale bulk finite strain analysis and paleo-stress reconstruction, respectively. The central Appalachian fold-thrust belt is characterized by a passive-roof duplex, and as such, the total shortening accommodated by the sequence above the roof thrust must equal the shortening accommodated within duplexes. Earlier attempts at balancing geologic cross sections through the central Appalachians have relied upon unquantified layer-parallel shortening (LPS) to reconcile the discrepancy in restored line lengths of the imbricated carbonate sequence and mainly folded cover strata. Independent measurement of grain-scale bulk finite strain on 40 oriented samples obtained along the transect yield a transect-wide average of 10% LPS with province-wide mean values of 12% and 9% LPS for the Appalachian Plateau and Valley and Ridge, respectively. These values are used to evaluate a balanced cross section, which shows a total shortening of 56 km (18%). Measured magnitudes of LPS are highly variable, as high as 17% in the Valley and Ridge and 23% on the Appalachian Plateau. In the Valley and Ridge province, the structures that accommodate shortening vary through the stratigraphic package. In the lower Paleozoic carbonate sequences, shortening is accommodated by fault repetition (duplexing) of stratigraphic layers. In the interval between the duplex (which repeats Cambrian through Upper Ordovician strata) and Middle Devonian and younger (Permian) strata that shortened through folding and LPS, there is a zone that is both folded and faulted. Across the Appalachian Plateau, slip is transferred from the Valley and Ridge passive-roof duplex to the Appalachian Plateau along the Wills Mountain thrust. This shortening is accommodated through faulting of Upper Ordovician to Lower Devonian strata and LPS and folding within the overlying Middle Devonian through Permian rocks. The significant difference between LPS strain (10%–12%) and cross section shortening estimates (18% shortening) highlights that shortening from major subsurface faults within the central Appalachians of West Virginia is not easily linked to shortening in surface folds. Depending on length scale over which the variability in LPS can be applied, LPS can accommodate 50% to 90% of the observed shortening; other mechanisms, such as outcrop-scale shortening, are required to balance the proposed model.

HYBRID GEOREFERENCING, ENHANCEMENT AND CLASSIFICATION OF ULTRA-HIGH RESOLUTION UAV LIDAR AND IMAGE POINT CLOUDS FOR MONITORING APPLICATIONS

Abstract. This paper presents a study on the potential of ultra-high accurate UAV-based 3D data capture by combining both imagery and LiDAR data. Our work is motivated by a project aiming at the monitoring of subsidence in an area of mixed use. Thus, it covers built-up regions in a village with a ship lock as the main object of interest as well as regions of agricultural use. In order to monitor potential subsidence in the order of 10 mm/year, we aim at sub-centimeter accuracies of the respective 3D point clouds. We show that hybrid georeferencing helps to increase the accuracy of the adjusted LiDAR point cloud by integrating results from photogrammetric block adjustment to improve the time-dependent trajectory corrections. As our main contribution, we demonstrate that joint orientation of laser scans and images in a hybrid adjustment framework significantly improves the relative and absolute height accuracies. By these means, accuracies corresponding to the GSD of the integrated imagery can be achieved. Image data can also help to enhance the LiDAR point clouds. As an example, integrating results from Multi-View Stereo potentially increases the point density from airborne LiDAR. Furthermore, image texture can support 3D point cloud classification. This semantic segmentation discussed in the final part of the paper is a prerequisite for further enhancement and analysis of the captured point cloud.

Distal Tibial Tuberosity Focal Dome Osteotomy Combined With Intra-Articular Condylar Osteotomy (Focal Dome Condylar Osteotomy) for Medial Osteoarthritis of the Knee Joint

High tibial osteotomy for medial-compartment knee osteoarthritis (OA) is an established biological knee reconstruction surgical procedure. In open- and closed-wedge high tibial osteotomy, the angulation correction axes are away from the center of rotation and angulation. This results in translation deformity, which alters the orientation of the adjacent joint and the length of the limb. In the present study, we combined the distal tibial tuberosity focal dome osteotomy centered on the center of rotation and angulation with the longitudinal condylar osteotomy (focal dome condylar osteotomy) for knee OA. The advantages of this procedure are as follows: physiological orientation of adjacent joint is achieved; limb length is maintained; joint stabilization in the coronal plane is achieved; patella infra is prevented; sufficient bone contact between the medial and posterior cortex is achieved; early weight-bearing walking is possible; and fibular osteotomy is not required. This study describes the details of the surgical procedure, including our compass cutter for accurate dome osteotomy and the postoperative rehabilitation program for patients with knee OA and moderate-to-severe varus deformity.

Rebound phenomenon after hemiepiphysiodesis: Determination of risk factors after tension band plate removal in coronal plane deformities of lower extremities.

Risk factors for rebound phenomenon (ReP) have not been investigated in detail. Aim of this study is to investigate risk factors of ReP in lower extremity deformities after two-hole plate removal. Patients who underwent hemiepiphysiodes were retrospectively reviewed. Joint orientation angles of tibia and femur, deformity type, age of patient at initial surgery and plate removal, deformity correction rate, bone growth rate were noted. An increase of 5° or more in joint orientation angles in the direction of the initial deformity was considered ReP. A relationship between the patient parameters and ReP was evaluated. Ninety-four segments (55 femurs and 39 tibias) of 43 patients (15 males and 28 females) were included. ReP was observed in 56.2% of all valgus deformities (n = 73), and in 23.8% of varus deformities (n = 21). The ReP rate was 60% (n = 27) and 20% (n = 2) in femoral segments with preoperative valgus and varus deformities, respectively (P = 0.03). When gender, etiology, sides and age of implant application and removal were compared, there was no difference between ReP(+) and ReP(-) groups in femur and tibia. The correction rate of mechanical lateral distal femoral angle in ReP(-) and ReP(+) femurs was 0.7 ± 0.4°/month and 1.1 ± 0.3°/month, respectively (P = 0.01). Age at implant application and removal in the femoral valgus group was significantly lower in the ReP(+) group (P = 0.008 and P = 0.005, respectively). The ReP rate was higher in femoral segments with overcorrection (P = 0.008). The ReP rate was higher in femoral valgus deformities. Younger age at plate application and removal, higher correction rate in deformity and intentional overcorrection increased risk for ReP.

Rock slope kinematic instability controlled by large-scale variation of basalt column orientation

Field observations of columnar-jointed basalt lava flows at Organ Pipes National Park near Melbourne, Australia, show varying columnar cooling joint orientations. The valley-confined basalt lava flows have columnar joints forming a downward spreading fan as the joints adopt orientations perpendicular to the margins of the flow. The variation in the pattern of columnar joint orientations controls local slope failure mechanisms, including toppling and planar sliding. Manually collected field data and terrestrial laser scanning data for joint faces have been used to assess the kinematic stability of the rock slopes. The terrestrial laser scanning data obtained includes a greater number of joint face orientations than manually collected data, including data for otherwise inaccessible locations. However, the bulk data collected by TLS requires careful interpretation at sub-sites within the field of observation to enable variation in column orientation and the associated slope stability mechanisms, to be recognised. The collection of larger datasets by remote methods has the risk of smoothing out local variations. The data in this case study demonstrates that the commonly assumed simple parallel pattern of columnar joints cannot be assumed, even in large, thick lava flows such as the Organ Pipes National Park.

Slope failure mechanism assessment based on regional geological information in layered rocks

Regional geological mapping commonly records the dip and dip direction of dominant layering such as bedding and foliation but not the orientation of joints. It is common for joints to form an orthogonal pattern relative to the dominant layering. In that case, the three-dimensional possibilities can be extrapolated allowing inferences to be made about kinematically feasible structural failure mechanisms. The resulting planar sliding, wedge sliding and toppling kinematic assessment can be integrated on a stereograph. The analysis of extrapolated joint sets can be conducted in the initial desk-top stage of a site investigation. The method is demonstrated using field data from Devonian sandstones in eastern Victoria, Australia. The sandstones have joint sets and partings on axial cleavage orthogonal to bedding. The range of potential structural failure mechanisms is extrapolated from the known bedding orientation and slope face direction.

Radiographic determination of normal canine femoral alignment in the sagittal plane: A cadaveric pilot study.

To establish a reliable methodology for radiographic determination of alignment of the normal canine femur in the sagittal plane. Cadaveric pilot study. Twenty-nine cadaveric canine femurs. Femoral specimens were collected from the University of Missouri veterinary anatomy laboratory, and standardized sagittal plane radiographs were obtained. The anatomic and mechanical axes, joint orientation, lines and joint orientation angles were determined in the sagittal plane by using the center of rotation of angulation methodology. Landmarks were clearly described to allow repeatability and reliability of measurements. Three observers with various degrees of experience measured two centers of rotation of normal angulation, the anatomic caudoproximal femoral angle, and the mechanical caudodistal femoral angle for all femurs on three separate days. Interobserver and intraobserver reliability were measured by using two-way mixed intraclass correlation coefficients (ICC) with associated 95% CI. Twenty-nine medium to large breed canine femora were measured. A high degree of correlation was present both among and between observers for all measurements performed, as defined by an ICC >0.8 for each. The described methodology was reliable and repeatable for measurement of angulation of grossly normal canine femora in the sagittal plane when performed by observers with varying degrees of clinical experience, as evidenced by a high degree of correlation for all values measured. This methodology may be used for standardized evaluation of alignment of canine femora in the sagittal plane.

Experimental and Numerical Study of Behaviour of Reinforced Masonry Walls with NSM CFRP Strips Subjected to Combined Loads

Near surface mounted (NSM) carbon fibers reinforced polymer (CFRP) reinforcement is one of the techniques for reinforcing masonry structures and is considered to provide significant advantages. This paper is composed of two parts. The first part presents the experimental study of brick masonry walls reinforced with NSM CFRP strips under combined shear-compression loads. Masonry walls have been tested under vertical compression, with different bed joint orientations 90° and 45° relative to the loading direction. Different reinforcement orientations were used including vertical, horizontal, and a combination of both sides of the wall. The second part of this paper comprises a numerical analysis of unreinforced brick masonry (URM) walls using the detailed micro-modelling approach (DMM) by means of ABAQUS software. In this analysis, the non-linearity behavior of brick and mortar was simulated using the concrete damaged plasticity (CDP) constitutive laws. The results proved that the application of the NSM-CFRP strips on the masonry wall influences significantly strength, ductility, and post-peak behavior, as well as changing the failure modes. The adopted DMM model provides a good interface to predict the post peak behavior and failure mode of unreinforced brick masonry walls.

Modification of bedrock surfaces by glacial abrasion and quarrying: Evidence from North Wales

Abrasion and quarrying are significant processes of subglacial erosion for ice masses in direct contact with hard substrates, yet their relative efficacy and spatio-temporal variability is unclear. Here, we investigate the glacial impact of these processes on a 70 m by 60 m bedrock surface at Moel Ysgyfarnogod in the Rhinog Mountains, Wales, using a combination of high-resolution digital photographs, analysis of a Digital Terrain Model derived from an Unmanned Aerial Vehicle survey, and regional ice sheet modelling. We map and analyze the distribution of grooved and striated surfaces, abraded surfaces, quarried blocks and open fractures in addition to the orientation of pre-existing bedrock fractures and joints. The grooves and striations are orientated in a single, consistent direction across the bedrock surfaces related to regional ice flow during the Late Pleistocene. Abraded and smoothed bedrock dominates the proximal edges of the bedrock outcrop and quarrying prevails on the distal edges of the bedrock outcrop, which are dominated by detached and partially detached blocks. We propose these blocks were removed during the final stages of the last glacial cycle when subglacial meltwater was plentiful in this otherwise predominantly frozen subglacial setting. A minimum estimate of 2000 m3 displaced material at this site implies that subglacial quarrying would have been an important erosional process during final stages of deglaciation.

Single-event multilevel surgery, but not botulinum toxin injections normalize joint loading in cerebral palsy patients

BackgroundMany patients with cerebral palsy present a pathologic gait pattern, which presumably induces aberrant musculoskeletal loading that interferes with natural bone growth, causing bone deformations on the long term. Botulinum toxin interventions and single-event multilevel surgeries are used to restore the gait pattern, assuming that a normal gait pattern restores musculoskeletal loading and thus prevents further bone deformation. However, it is unknown if these interventions are able to restore musculoskeletal loading. Hence, we investigated the impact of botulinum toxin injections and single-event multilevel surgery on musculoskeletal loading. MethodsGait data collected in 93 children with bilateral cerebral palsy, which included pre- and post multi-level botulinum toxin (49 children) and single-event multilevel surgery (44 children) assessments, and 15 typically developing children were retrospectively processed using a musculoskeletal modelling workflow to calculate joint angles, moments, muscle and joint contact force magnitudes and orientations. Differences from the typically developing waveform were expressed by a root-mean square difference were compared using paired t-tests for each intervention separately (alpha <0.05). FindingsBotulinum toxin induced significant changes in the joint angles, but did not improve the muscle and joint contact forces. Single-event multilevel surgery induced significant kinematic and kinetic changes, which were associated with improved muscle and joint contact forces. InterpretationThe present results indicate that botulinum toxin injections were not able to restore normal gait kinematics nor musculoskeletal loading, whereas single-event multilevel surgery did successfully restore both. Therefore, single-event multilevel surgery might be protective against the re-occurrence of bone deformation on the longer term.

Experimental study of the mechanical performances of sandstone blocks healed with mortar taken from shotcrete basic mix

Shotcrete has been widely used in geotechnical engineering to support jointed rock masses. In spite of providing normal forces to enhance the resistance capability of rock masses, shotcrete materials were also capable of healing joints through penetration. In present study, to better verify the healing efficiency of the shotcrete method, a series of experimental investigations have been undertaken to check the mechanical performances of sandstone blocks which are healed with shotcrete mater0ials. To account for small joint gap, the mortar taken from shotcrete basic mix was firstly prepared by eliminating coarse aggregates with particle diameter larger than 3.0 mm. Then, the mortar materials were incorporated to prepare integrated sandstone samples through healing the joint between two opposite rock blocks. Afterwards, uniaxial compression tests were carried out on these integrated sandstone samples. The influences of joint orientation and joint roughness on the failure and strength behaviors of integrated sandstone samples were investigated. Test results showed that the mechanical performances of sandstone blocks healed with mortar taken from shotcrete basic mix were significantly dependent of the joint geometry. The motivation of intact rock strength to resist compression loads would increase the healing efficiency of the shotcrete materials, while the failure of the shotcrete materials would reduce this efficiency.

Effect of joint structure and slope direction on the development of collapsing gully in tuffaceous sandstone area in South China

This study focuses on the collapsing gullies in tuffaceous sandstone area and investigates the slope direction and morphological characteristics of the main and branch gullies. Furthermore, we assess the structural characteristics of the rock joints within this area, including their strike, dip direction and dip angle. The results show that there are 405 collapsing gullies in the study area. The slope directions associated with collapsing gullies and the directions of the main gullies largely fall within the ranges of NE20°-NE90°, SE90°-SE160°, SW240°-SW270°, and NW270°-NW290°. The collapsing gullies include 1103 branch gullies in total, most of which have directions that fall within the ranges of NE20°-NE40°, NE50°-NE70°, NW280°-NW300°, and NW330°-NW350°. The joints in the bedrock are directional and regional, and they can be divided into two main groups. The number of southward dip directions is greater than the number of northward dip directions, and most of the measured dip angles are greater than 60°. The mean dip angle is greatest for joints with measured strike values of NW280°-NW290°, with a value of 85.2°. The development of collapse gullies is affected by both the slope direction and joints. The slope direction determines the direction of the main gullies, with a correlation coefficient of 0.809 (P<0.01). The branch gullies are mainly affected by joints, with a correlation coefficient of 0.876 (P<0.01). The joint structure also influences the degree of development of the collapsing gullies, and the average depth of the gullies that parallel the dominant joint orientation is significantly larger than that of gullies with other directions. Moreover, the average depth of the gullies associated with the dip angle of 85.2° measured relative to the joint strike is 6.89 m, which is significantly greater than that associated with lower dip angles. The dip angles of joints have an important effect on the infiltration of water, and high dip angles accelerate the erosion associated with collapsing gullies.