Helical Plates Research Articles

Axillary nerve elongation in humeral fracture plating: A cadaveric study for comparison between straight and helical Philos plates

ObjectiveHelical plating is a known concept in humeral fracture treatment. Attention should be paid to the axillary nerve when inserting a plate underneath the deltoid muscle. The purpose of this cadaveric study was to estimate axillary nerve stretching when introducing the plate. Methods: On 42 fresh frozen human humeri, an 8-, 10- and 12-hole Philos plate in a straight and a helical shape were compared measuring the maximum plate-bone-distance. Results: For all three plate lengths, the helical plates had a significantly lower plate-bone-distance. Conclusion: Indirectly, this suggests a lower axillary nerve elongation and hence less chance of nerve damage.

Cyclic pullout behavior of helical anchors for offshore floating structures under inclined loading condition

Helical anchors are an effective option to support offshore floating structures with mooring and anchoring systems, where wave and tidal forces are the predominant load components leading to cyclic and inclined loading conditions. In this study, the cyclic and inclined pullout load carrying behavior of helical anchors was investigated. Large-deformation finite element (FE) analysis using the coupled Eulerian–Lagrangian (CEL) method was performed to simulate the cyclic pullout load response of helical anchors. Various configuration conditions of the helical anchor and loading direction, including the number and diameter of helical plate, plate arrangement and load inclination angle (θ), were considered in the analysis. Induced displacements were most significant during the first loading cycle, whereas those for subsequent loading cycles were relatively small. The geometry condition of the helical anchor less affected the pullout load carrying behavior as θ increased. The horizontal displacements (δh) were larger than the vertical displacements (δv) when θ was larger than 30°. When θ was smaller than 30°, δv was more dominant component. It was found that the configuration with top-down increasing diameter was more effective to enhance the pullout load carrying behavior than the conventional bottom-up increasing diameter configuration.

A practical guide for the use of contour locking plates for the repair of humeral diaphyseal fractures with proximal extension

IntroductionThe emergence of minimally invasive techniques has expanded the use of plates and improved their safety for the repair of humeral diaphyseal fractures with proximal extension. In this study, we aimed to determine the best contouring method for long locking plates in the repair of humeral fractures using this approach. Patients and methodsComparative observations were performed between helical and spiral modelling in plastic models to identify which shape best fits the contours of the humerus. To determine the best shape, we attempted to assess the torsion required for the plate to settle laterally in the greater tuberosity and anteriorly in the diaphyseal region of the humerus. After establishing the best approach, we transferred the method to two anatomical specimens and confirmed the viability of the method and pathways. Additionally, to confirm the clinical applicability of the method, we applied the method in ten patients. ResultsAfter placing the plates in the bone models, it was found that the helical plate was more distant from the bone. On the other hand, the spiral plate achieved better accommodation along the contours of the humerus. The amount of twist was tested at 50°, 70° and 90°. When the plate was twisted at 70°, it maintained contact with the greater tuberosity proximally and the anterior cortical diaphyseal region. Eight patients completed the follow-up. Radiographic consolidation and good functional outcomes were achieved in all patients. ConclusionsSpiral modelling at 70° allows anatomical accommodation at the greater tuberosity proximally and in the diaphyseal region.

Performance Assessment of Screw Piles Embedded in Soft Clay

Screw piles are widely used in a variety engineering applications supplying stability against compression, overturning moment, uplift tension, and horizontal loads. Screw pile is a famous solution for support light structures, roads and rail signs which have relatively low-capacity foundation. In this study, the behavior of circular (10) mm solid screw pile models embedded in a bed of soft clay soil covering a layer of sandy soil has been studied. The 200 mm thick sand layer was compacted in a steel container with a diameter of 300 mm into four sublayers. The sandy soil layer was compacted at a relative density of 70%. The 300 mm thick soft clay soil bed with Cu (30) kPa was compacted in six sub-layers on the sandy bottom layer. Model tests are carried out with screw piles with a length of 300 mm, 350 mm and 400 mm and a helix diameter of 30 mm. Also, single and double helix and different S/Dh ratio were used for these piles and a comparative study between screw piles and ordinary piles (without helices) is accomplished. This study revealed that introducing screw pile of double helix increases its bearing capacity in soft clay soil by up to a (4-8) % as compared to a single helix screw pile. The results showed that the behavior of screw pile essentially depends on the geometric properties of the pile. According to the achievements, compressive load capacity of screw piles depends on embedded length, spacing ratio (S/Dh) and number of helical plates.

Heat transfer characteristics of a short helical plate in a horizontal circular tube

Enhancement techniques based on artificial roughness are used in numerous applications of heat exchangers. Heat exchange devices are essential components in complex engineering systems, such as industrial energy generation and energy conversion. In this study, a short helical plate was used to enhance heat transfer in a horizontal circular annulus tube. Experiments and CFD were performed to study the heat transfer effect of the helical plate, and Teflon and brass materials were used for the helical plate. Uniform heat flux was considered, and particle image velocimetry (PIV) was used for comparisons. The Nusselt number profiles increased steeply around the Teflon helical plate and decreased suddenly to 1.0 along the test section.

Data Reduction and Dynamic p-y Curves of Helical Piles from Large-Scale Shake Table Tests

AbstractA helical pile is composed of a steel shaft and single or multiple helical plates welded to its shaft. This study investigated full-scale seismic soil reactions for helical piles embedded i...

Monotonic, cyclic and post-cyclic performances of single-helix anchor in residual soil of sandstone

Helical anchors are commonly used in Brazil for guyed transmission towers subjected to static and cyclic wind loads. In most cases, these anchors are installed in tropical residual soil, a micro-structured material in which the shear strength is provided by soil bonding. During installation of a helical anchor, as the helical plate moves downward into the ground, the soil penetrated is sheared and displaced. Consequently, in this type of soil, anchor installation affects the soil shear strength significantly associated with a bonded structure. However, the cyclic responses of helical anchors in this type of structured soils are rarely reported. To address this problem, tests were conducted in a Brazilian residual soil to investigate the monotonic, cyclic and post-cyclic performances of single-helix anchors. Field tests used two instrumented single-helix anchors installed in this typical residual soil of sandstone, which is frequently observed in large areas in the southern Brazil. The testing results indicate that the disturbance caused by the anchor installation affected the monotonic uplift performance markedly. The results of cyclic loading tests also show no significant degradation of helix bearing resistance and reduced displacement accumulation with increasing load cycles. This is perhaps due to the soil improvement caused by previous loading, which then increases the stiffness response of the anchor.

Investigation of pullout load capacity for helical anchors subjected to inclined loading conditions using coupled Eulerian-Lagrangian analyses

The pullout load carrying behavior of helical anchors for inclined loading conditions was investigated based on the coupled Eulerian-Lagrangian (CEL) analyses. Various types of helical anchors, specified as Types 1 to 6, were adopted in the analyses. Types 1, 2 and 3 represent those with one, two, and three equal-diameter helical plates and Type 4 was a helical anchor type with two helical plates of different diameters. Types 5 and 6 were both with three helical plates of different diameters in opposite diameter configurations. Inclined loading conditions affected the pullout capacity (Qu) of helical anchors producing lower Qu with increasing load inclination. The patterns of the Qu decrease with increasing load inclination were similar for all helical anchor types considered in this study. The values of Qu were approximately similar up to θ = 60° and then decreased continually with furthering increasing θ. Qu was lowest at θ = 90°. The top-down increasing diameter configuration of helical plates was more efficient than the bottom-up increasing diameter configuration. A normalized load capacity relationship was proposed, which can be used to evaluate Qu for inclined loading conditions. The pullout behavior of helical anchors was governed by helical plates with marked effects of helical plate configuration, which was however less pronounced with increasing θ.

Analysis of Helical Piles with Case Study in Medium Stiff Clay

Objectives: To study about the design and the ultimate load capacity of helical piles, this depends on various parameters of helices. Methods/Analysis: This project focuses on analytical study of the response and behaviour of Helical Piles in the medium stiff clay. The parameters to be analysed are: Diameter of helical piles, outer diameter of hollow pile shaft and spacing between the adjacent helical plates. An optimal pile configuration was chosen and is then modelled using Helix Pile software based on the provided soil properties and its results are verified against the analysis results. Further, a case study was also done by comparing the capacities, scheduling and economic feasibility of Helical Piles and conventional concrete piles. Findings: From the analytical study it can be concluded that the increase in diameter of the helical plates has positive effect on the uplift capacity and compression behaviour; on the other hand the increase in the outer diameter of pile shaft has negative impact on the same. The spacing between the helices also increases the uplift capacity and compression behaviour of helical piles. Also Helical Piles are cost effective; require less in number and faster erecting when compared to concrete piles. Keywords: Helical Piles, Helical Plates, Medium Stiff Clay

Pre-contouring long helical plate of proximal humerus internal locking system aided by 3D-printing technique in minimally invasive plate osteosynthesis for metadiaphyseal fractures of the proximal humerus: a cadaveric study and clinical experience

Objective To identify the anatomic advantages of pre-contouring long helical plate of proximal humerus internal locking system (PHILOS) aided by 3D-printing technique in minimally invasive plate oseoynthesis (MIPO) for metadiaphyseal fractures of the proximal humerus. Methods Firstly in a cadaveric study, 12 fresh frozen samples of upper extremity were divided into 2 equal groups: 6 in a Synbone group and 6 in a 3D-printing group. Long 10-hole PHILOS plates were pre-contoured helically according to Synbone humerus models in the Synbone group but according to 3D-printing humerus models in the 3D-printing group. All these helical plates were fixed onto the cadaveric humerus using MIPO technique respectively. The horizontal distances between the radial nerve and the lateral side of the plate were measured at the point where the radial nerve penetrates the muscular septum, at the 6th hole on the plate and at the distal end of the plate; the distance between the medial side of the distal plate and the upper arm neurovascular bundle was also measured. Finally, the full lengths of all these cadaveric humeri were measured. Secondly, on the basis of the anatomic study, 16 patients with metadiaphyseal fracture of the proximal humerus were treated at Department of Orthopedic Surgery, The Sixth People’s Hospital of Shanghai from February 2013 to March 2016, using the same MIPO technique and the same long 10-hole PHILOS plates pre-contoured helically on the 3D printing models which were mirrored on the humerus on the healthy side of the patients. They were 4 men and 12 women, aged from 59 to 87 years (mean, 71.0 years). By the AO/OTA classification, 10 cases were type B and 6 type C. The fracture line involved the proximal humerus in 7 cases. Postoperative complications were followed up. At the final follow-up, the shoulder function was assessed according to the Constant-Murley score and the elbow function according to the Mayo Elbow Performance Score (MEPS). Results By the anatomic measurement, the full length of cadaveric humerus averaged 30.17±1.93 cm in the Synbone group and 29.75±2.17cm in the 3D-printing group, showing no significant difference (P>0.05). The horizontal distances between the radial nerve and lateral side of the plate at the point where the radial nerve penetrates the muscular septum, at the 6th hole on the plate and at the distal end of the plate in the Synbone and 3D-printing groups were, respectively, 11.50±0.92 mm versus 17.87±1.88 mm, 6.90±1.78 mm versus 14.83±1.50 mm, and 5.14±1.14 mm versus 8.36±1.27 mm, all showing significant differences between the 2 groups (P 0.05). The clinical observation found no iatrogenic nerve injury. The 16 patients were followed up for an average of 25.3 months (range, from 24 to 38 months). All fractures got united uneventfully. At the final follow-up, their Constant-Murley scores averaged 77.6 points and their MEPS 96.5 points. Conclusion The risk of iatrogenic injury to the radial nerve can be lowered when 3D-print technique is applied for helical pre-contouring of long PHILOS plate in the MIPO for metadiaphyseal proximal humeral fractures, leading to satisfactory clinical results. Key words: Humeral fractures; Fracture fixation, internal; Anatomy; Clinical trial; 3D printing technology

Bearing capacity of helical pile foundation in peat soil from different, diameter and spacing of helical plates

In an area dominated by thick peat soil layers, driven piles foundation is often used. These piles are generally skin friction piles where the pile tips do not reach hard stratum. Since the bearing capacity of the piles rely on the resistance of their smooth skin, the bearing capacity of the piles are generally low. One way to increase the bearing capacity of the piles is by installing helical plates around the pile tips. Many research has been performed on helical pile foundation. However, literature on the use of helical pile foundation on peat soil is still hardly found. This research focus on the study of axial bearing capacity of helical pile foundation in peat soil, especially in Riau Province. These full-scale tests on helical pile foundation were performed in a rectangular box partially embedded into the ground. The box is filled with peat soil, which was taken from Rimbo Panjang area in the district of Kampar, Riau Province. Several helical piles with different number, diameter and spacing of the helical plates have been tested and analysed. The tests result show that helical pile with three helical plates of uniform diameter has better bearing capacity compared to other helical piles with varying diameter and different number of helical plates. The bearing capacity of helical pile foundation is affected by the spacing between helical plates. It is found that the effective helical plates spacing for helical pile foundation with diameter of 15cm to 35cm is between 20cm to 30cm. This behaviour may be considered to apply to other type of helical pile foundations in peat soil.

Axial and lateral performance of spun-cast ductile iron helical tapered piles in clay

A novel piling system is proposed to support solar energy panels: a spun-cast ductile iron (SCDI) tapered pile fitted with a single helical plate installed by mechanical torque. The proposed pile combines the efficiency of the tapered cross-section and the construction advantages of helical piles, as well as the competitive cost, effectiveness and durability of SCDI with a rough surface. This paper presents an investigation of its compressive, uplift and lateral performance in clay employing three-dimensional non-linear finite-element models. In addition, simulations of other pile shapes, including tapered and straight shafts, as well as conventional steel helical piles, were performed for comparison purposes. Effects of the pile length, installation technique and the presence of a top crust on the pile performance were investigated. The results demonstrated the feasibility of the proposed pile, especially for applications that impose high uplift and lateral loading. Moment–horizontal force interaction diagrams are provided to aid in design of the proposed pile when subjected to a combination of moment and horizontal loads.

Сравнительный анализ результатов использования трех способов остеосинтеза при переломах диафиза плечевой кости

Introduction The tactics of surgical treatment of patients with humeral shaft fractures have beenactively discussed in special scientific literature. The development of new osteosynthesis methods requires their careful comparative evaluation. Purpose To compare the treatment results in the three comparable clinical groups of patients with fractures of the humeral diaphysis in its upper and middle thirds after using a minimally invasive osteosynthesis with a helical plate (MIHPO), locked intramedullary osteosynthesis (LIO) and conventional plating osteosynthesis (CPO). Materials and methods 92 patients with fractures of the humeral diaphysis in its upper and middle thirds were divided into three groups, comparable in number, sex, age, mechanism of injury, location and nature of fractures, according to the osteosynthesis performed: MIHPO (33 patients), LIO (33 Patient) and CPO (26 patients). Terms prior to surgery, intervention time, image intensifier time (IIT), restoration of the humerus anatomy, functional results using DASH and Constant systems, and complications were compared. Control examinations were performed at 1, 6, 12, 18 and 24 weeks after the operation. Clinical, radiographic and statistical methods of study were used. Results Duration of the operation in all three groups did not differ significantly. The IIT was significantly less (p less 0.001) in the MIHPO group when compared to LIO. The lowest residual angulation and translation after the osteosynthesis was observed in the CPO group while in MIHPO and LIO groups these findings were not significantly different. The dynamics of restoring the functions of the damaged limb on the DASH and Constant scales did not differ significantly in three groups at all time-points of follow-ups. After 24 weeks, fracture consolidation was noted in all the patients in the MIHPO and CPO groups and in 31 (91.7 %) patients in the LIO group. Six events (18 %) of complications of two types were observed in four patients of MIHPO group (12 %). Ten patients in LIO group (30 %) had 15 complications (45 %) of 6 kinds and 9 complications (35 %) of three kinds were noted in eight CPO patients (30 %). Conclusion The MIHPO method is safe and effective. Its results are comparable with the techniques of LIO and CPO in frequency and timing, functional results. However, it results in a lower incidence of complications. Therefore, it can be recommended for a wider application on the appropriate indications.

Numerical modelling of pullout of helical soil nail

An investigation into the pullout response of helical soil nail using finite element subroutine Plaxis 2D is presented. The numerical modelling of actual pullout response is achieved by axisymmetric and horizontal loading condition. The effect of varying number of helical plates, helical plate spacing and helical plate diameter is studied to understand the pullout capacity behaviour. The failure surfaces for various helical soil nail configurations and their pullout mechanisms are also analysed and discussed. The pullout capacity is found to increase with increase in number of helical plates. The helical plate spacing ratio (s/Dh) and diameter ratio (Dh/Ds) are found to increase the pullout only up to a critical value. The response of helical soil nail using axisymmetric finite element simulation is found similar to the uplift behaviour of helical piles and helical soil anchors. In the absence of literature regarding numerical modelling of helical soil nail, simulation results are validated with uplift responses of helical piles and soil anchors. A good agreement in their comparative study for pullout response is also observed.

Large-diameter helical pile capacity – torque correlations

Large-diameter helical piles are utilized increasingly to support heavy structures. Both the magnitude of the required installation torque and the pile capacity can be directly attributed to the soil shearing resistance developed over the embedded area of the pile including the shaft and helical plates. Hence, the pile capacity can be correlated to installation torque. Such correlations are widely used in the helical pile industry as a means for quality control and quality assurance. In the current study, a total of 10 test piles were installed while monitoring the installation torque continuously with depth. The recorded installation torque profiles were demonstrated to be accurate and repeatable. Field pile load tests were conducted and their results were analyzed to determine the interpreted ultimate capacity of the test piles. The results demonstrate that the ultimate capacity of large-diameter helical piles can be interpreted from pile load test data employing the failure criteria proposed by Elkasabgy and El Naggar in 2015 and Fuller and Hoy in 1970. The measured installation torque and corresponding ultimate capacity values were employed to define torque–capacity correlation (Kt) based on embedded pile area. It was demonstrated that the proposed Kt is suitable for large-diameter helical piles.

Effects of vertical loading on lateral screw pile performance

The offshore wind energy sector faces new challenges as it moves into deeper water deployment. To meet these challenges, new and efficient foundation solutions are required. One potential solution is to upscale onshore screw piles but they require verification of performance for new geometries and demanding loading regimes. This paper presents a three-dimensional finite-element analysis investigation of screw pile behaviour when subjected to combined vertical and lateral loading in sand. In the investigation, the screw pile length and helical plate diameter were varied on piles with a fixed core diameter while subjecting the piles to combined axial and lateral loading. The results were compared with results from straight shafted piles with the same core diameter. The results of the analysis revealed that vertical compression loads increased the lateral capacity of the screw piles whereas vertical uplift loads marginally reduced the lateral capacity. The downside of this enhanced lateral capacity is that the screw piles experience higher bending moments. This suggests that, when using screw piles for offshore foundation applications, structures should be designed to maintain axial compressive loads on the piles and induced bending moments need to be adequately assessed when deciding on appropriate structural sections.

Axial Performance of Helical Tapered Piles in Sand

The axial capacity of novel spun-cast ductile iron (SCDI) tapered pile fitted with a lower helical plate is investigated. Seven instrumented piles, five SCDI tapered and two steel straight shafts, were installed in sand soil using mechanical torque. The piles were tested under axial compressive loading and their ultimate capacities were determined. To assess the cyclic loading effect on the piles performance, two load sequences were adopted: four piles were subjected to monotonic loading, and three were subjected to initial cyclic loading followed by monotonic loading. The installation torque was monitored and the resulting capacity-to-torque ratio was compared to the literature reported values. Tapered helical piles displayed a stiffer response and yielded higher capacities compared to the straight ones. Strain gauges were used to evaluate the piles load transfer mechanism, and demonstrated increased shaft resistance due to the pile taper. The taper helped compact the sand within the zone adjacent to the pile, originally disturbed by the helix penetration, hence increased the soil strength and stiffness. These effects were prominent for larger ratio of shaft/helix diameter. Finally, 3D finite element analyses were conducted to evaluate the axial performance of the system and demonstrated its enhanced frictional resistance. The experimental and numerical results confirmed the superior performance of the proposed system in sands.

Interaction Effect of Group of Helical Anchors in Cohesive Soil Using Finite Element Analysis

In this paper, the interaction effect of a group of two and four symmetrical as well as asymmetrical helical anchors resting in homogeneous cohesive soil deposit with different helix configurations is determined using finite element analysis. The anchors were pulled to its ultimate failure controlling the displacement. Eight different types of anchor configuration were considered in the analysis, where mainly the number of helical plates, the depth of upper- and lower-most helical plates and the ratio of spacing between the helical plates to the diameter of the plate were varied. The variation of load–displacement curve for each anchor in the group was obtained and subsequently, the ultimate uplift capacity of each anchor was determined. The soil was assumed to follow Mohr–Coulomb failure criteria. The present theoretical observations are generally found in good agreement with those theoretical and experimental results available in the literature for single isolated helical anchor.

Scale effect in centrifuge tests of helical anchors in sand

Centrifuge modelling is an advantageous technique to simulate the behaviour of helical anchors in sand. The uplift capacity of a single-helix anchor is the sum of the helix bearing resistance plus the shaft resistance; therefore, recommendations to avoid the grain-size effect of previous model tests on plate anchors and on regular piles appear to be reasonable for helical anchor model tests. However, there are two important differences between centrifuge models of plate anchors and helical anchors: the ratio of the helical plate to the shaft diameter and the plate installation procedure. Consequently, the shaft friction and the plate bearing resistance of helical anchors can be affected by the scaling effect in a different manner. To clarify this uncertainty, this study was proposed to investigate the grain-size effect on the results of uplift capacity of helical anchor models in sand. Anchor models with different scales were tested to simulate the same prototype in very dense dry sand in a centrifuge. These experiments have shown that no scale effect was found for models with the ratio of the effective helical radius to the average grain size >58. The findings obtained here could guide future centrifuge model studies on helical anchors.

Cyclic lateral performance of helical tapered piles in silty sand

A novel piling system, spun-cast ductile iron (SCDI) tapered pile fitted with a lower helical plate, is proposed in this study to support solar energy panels. The cyclic lateral performance of the ...