Shaft Axis Research Articles

Rigid multibody dynamic modeling for a semi-submersible wind turbine

This paper presents a rigid multibody dynamic model for a Floating Offshore Wind Turbine, and its dynamic responses are simulated. This system consists of four important mechanical rigid parts, referred to as platform, tower, nacelle, and rotor. The platform is constrained by three cables connected to the seabed, known as the mooring system. Buoyancy and hydrodynamic forces are also applied to the platform. The semi-submersible platform is investigated as one of the latest proposed designs for the platform, which plays an important role in the stability and minimization of applied forces to the whole structure. Turbine’s rotor is modeled as a rigid disk rotating about its shaft axis and under the influence of aerodynamic force and torque. Therefore, the platform with six, and rotor with one Degree of Freedom in combination with the tower and nacelle, form a seven Degree of Freedom holonomic system. Euler–Lagrange equations are utilized to formulate the system’s equations of motion. In numerical simulation section, dynamic responses under four load cases are presented and validated against “Fatigue, Aerodynamics, Structures and Turbulence” module outputs under the same conditions. The effects of considering pontoons and cross braces on dynamic responses are also investigated. Moreover, the effect of the rotor’s gyroscopic moment is examined.

ANALYSIS OF CRACKS AT THE TORSION VALLARS CAUSED WITHOUT LOADING

Nowadays, the hull suspension systems that use torsion shafts as elastic suspension elements are fitted to the majority of modern tracked vehicles. The main type of failure in such systems is the fracture of the torsion shafts due to the formation of fatigue cracks, which leads to failure of the suspension assemblies. This work presents an analysis of fracture toughness of torsion shafts of a standard tracked chassis used to develop a family of multipurpose transport vehicles GT-TM, GT-TMS, etc. The analysis is carried out under an operating load level for a crack located on the cylindrical part of the torsion shaft, the plane of which is at an angle to the torsion shaft axis and coincides with the position of the main areas of the stress state. The calculation of fracture toughness is based on Irwin fracture criterion. The calculations of the maximum stress intensity factor along the crack front are performed using the finite element method in the ANSYS software package. The results of the analysis of fracture toughness are presented in the form of dependences of the critical depth of the crack on the ratio of the fracture half-length to its depth. The data obtained can be used to determine the residual life of torsion shafts of the tracked vehicles based on the chassis under consideration. Keywords: suspension system, fracture toughness of torsion shafts, edge crack, stress intensity factor, finite element method, Irwin fracture criterion.

Hair diameter measurements for planning follicular unit extraction surgery (FUE): Is there a correlation between the micrometer caliper and scanning electron microscopy (SEM) findings?

Hair shaft diameter is one of the most important factors for the outcome of follicular unit extraction (FUE) surgery. In fact, the hair shaft is elliptical. Therefore, it has a long and short axis. Many hair transplantation surgeons use manual micrometer caliper for gauging hair diameter and use the results in the management of recipient and donor area. In this study, we aimed to identify the dependability of micrometer caliper and also the hair diameter diversity pattern in the donor area. Two hundred and seventy hairs were collected from three males with androgenetic alopecia. Hair samples were obtained from the 1cm2 boxes from superior to inferior at the mid-point of temporal, parietal, and occipital donor areas. The diameter of each hair was measured both with a micrometer caliper and scanning electron microscopy (SEM). Average diameter measured by scanning electron microscopy was 83.01µm for the long axis and 51.51µm for the short axis. The average value for the micrometer caliper measurement was 53.32µm. Comparison of micrometer caliper results with the short-axis measurements of SEM revealed a strong significant correlation. The hair diameters from superior, middle, and inferior boxes revealed a tendency to decrease toward the inferior regions. A manual micrometer caliper is a dependable tool for planning FUE surgery, and it measures the short axis of the elliptical hair shaft. Hair diameter tends to decrease toward the inferior regions of the donor area.

Retrospective Clinical and Radiological Outcomes of Total Hip Arthroplasty in 51 Patients After a Mean 8.2 Years Using the Nanos® Short-stem Prosthesis

Introduction: Over the past several years, femoral short-stem hip implants have become more popular as a treatment option in the field of primary hip arthroplasty for younger and more active patients. Current data on clinical outcomes and the implant survival rates in patients with short-stem implants cover a maximum of five to six years. The aim of this study was to assess the survival rates, as well as clinical and functional outcomes, in total hip arthroplasty (THA) using the Nanos® short-stem implant (Smith & Nephew, Marl, Germany) over a follow-up period exceeding 5 y. Materials and Methods: This single-center retrospective study included the first 100 patients who were treated at the Department of Orthopedics at the University Hospital Halle (Saale) between January 2008 and February 2009. Ultimately, the complete data of 51 patients (54 hips) were reviewed. The follow-up period was from May to November 2017. We evaluated patient satisfaction regarding pain and function using a grading system. The Harris Hip Score and Forgotten Joint Score were obtained to evaluate functional outcome after THA. Postoperative radiographic evaluation included the measurement of leg-length discrepancy, changes in the shaft axis, femoral offset and horizontal or vertical center of rotation. Potential postoperative shaft angulation or axial shaft migration was also determined. Radiographic images were checked for radiolucent lines and heterotopic ossification using the classification systems outlined by Green and Brooker. Results: The average follow-up was 97.8 months (8.2 y). The mean patient age at follow-up was 68 y and the body mass index was 28.2 kg/m2. The mean Harris hip score at follow-up was 92.0 and the Forgotten Joint Score was 91.7 %. Survey results showed that patient satisfaction and pain perception were rated very good. No significant change in leg length was observed (mean: 0.1 mm shortening). Overall, a rather varus stem positioning was detected postoperatively (mean: 3.1°). The femoral offset was slightly reduced on average in the entire patient group (mean: -1.8 mm). In the horizontal plane, lateralization of the center of rotation was detected overall (mean: 0.7 mm). In the vertical plane, cranialization was noted (mean: 1.4 mm). The CCD angle did not change. There was no further stem migration postoperatively. Radiolucent lines occurred in 10 cases in Gruen zones 1 and 7. Heterotopic ossification occurred in stages 1 to 3 according to the Brooker classification system. We found no cases of aseptic loosening or other reasons for revision. Conclusion: The outcomes after a mean follow-up of 97.8 months (8.2 y) showed that high levels of patient satisfaction and functional outcome can be achieved with the use of a short-stem endoprosthesis. Sufficient restoration of the patient's individual anatomy paired with high survival rates makes this short-stem prosthesis a reliable implant in total hip arthroplasty.

Study on Water Inflow Variation Law of No.1 Shaft Auxiliary Shaft in HighLiGongshan Based on Dual Medium Model

When the fracture is not developed and the connectivity is poor, the original single medium simulation cannot meet the accuracy requirements. Now, the seepage simulation of fractured rock mass has gradually developed from equivalent continuous medium to dual medium and multiple medium. However, it is still difficult to establish the connection between a discrete fracture network model and a continuous medium model, which makes it difficult to simulate the influence of fracture location on the seepage field of rock mass. As the excavation direction of the shaft is vertically downward, the surrounding strata are symmetrical around the plane of the shaft axis, which is different from the horizontal tunnel. Taking the auxiliary shaft of the No.1 Shaft in HighLiGongshan as the engineering background, combined with Monte Carlo methods and DFN generator built in FLAC3D5.01, a discrete fracture network is generated. Based on the dual medium theory, MIDAS is used to optimize the modeling of each fracture group. At the same time, the concept of “Fracture Weakening area” is introduced, and the simulation is carried out based on a fluid–solid coupling method. It is found that the simulation effect is close to the reality. The water inflow increases with the increase of shaft excavation depth, and the water inflow at the end of excavation is nearly three times larger than the initial value. Combined with Legendre equation, a new analytical formula of water inflow prediction is proposed. It is found that this analytical formula is more sensitive to permeability and has a greater safety reserve.

Inverse centripetal dissection: A rescue technique for mis-dissected lenticule during SMILE.

Management of mis-dissected lenticule during Small-incision lenticule extraction (SMILE) is technically challenging and might be experienced more by novice surgeons especially in eyes with low refractive errors and thin lenticules. Presently, we describe a rescue method of inverse centripetal dissection (ICD) to manage mis-dissected lenticules. In this technique, after inadvertent dissection of posterior plane prior to anterior plane, the double-ended SMILE dissector is rotated along its shaft axis clockwise from the left upper margin of the mis-dissected lenticule to form an inversely folded lenticule which is then subsequently dissected centripetally till midline. This is then extracted by performing lenticulorrhexis with a pair of microforceps. We performed this technique in 10 eyes of 10 patients and the lenticule extraction was accomplished successfully in all eyes. At six months follow-up, the uncorrected visual acuity was 20/20 with a clear interface in all eyes. The ICD approach might serve as a useful rescue technique for managing mis-dissected lenticules.

The study of the curvature of the axis of the processed shaft when based in the centers using a steady rest

This paper presents the analysis and results of the study of a two-stage shaft fixed in dead centers and a rest device. Cutting forces act on the shaft, causing a bending moment. The analysis of the curvature of the axis of the workpiece, processed on a lathe when based in the centers, using a rest device, is carried out. The formula of elastic displacement of the workpiece axis at the place of the resulting cutting force is obtained. Diagrams of the stresses of the shaft axis displacements are constructed and a conclusion is made. The analysis showed that the greatest deflection is at the point of the cutting forces acting on the shaft. The quality of the part obtained after processing is characterized by accuracy. The parts mating in the product and, as a result, the overall reliability depends on how accurately the size and shape of the part will be maintained during processing. Parts with length of 10 to 12 times larger than the diameter are bent under the action of their own weight and cutting forces, as a result of which they get a barrel-like shape. It is possible to eliminate this by applying special devices for the machine. When processing long nonrigid workpieces, the tools, jigs and fixtures must evenly distribute the clamping force over the surface of the part. These conditions are well provided by technological equipment with pneumatic, hydraulic clamping devices, as well as with various collet clamps, split bushings, diaphragm or cartridges. When processing long non-rigid shafts, rest devices are used. The rest device plays the role of the main or secondary support when working with workpieces; it creates support for large, long parts during processing. It helps to avoid the risk of damage and deformation of the workpiece or the cutting elements of the machine, by giving the workpiece additional stability

Failure analysis of a marine intermediate shaft

A bulk-ship was not working normally when anchoring to wait for entering port. Inspection in site found that the intermediate shaft fractured. The intermediate shaft had accumulatively serviced for 43,000 h before fractured. Fractographic investigation indicated that the multiple origins fatigue fracture was the dominant failure mechanism of the shaft. The cracking propagated on two fracture planes at approximately ± 45° with respect to the shaft axis. The material of failed shaft was found to be a low carbon steel of type ASTM 1020, rather than the specified the medium carbon steel of type ASTM 1035. The average values of yield strength and ultimate strength of shaft material were respectively 16% and 20% lower than the lower limit of technical specification due to low carbon content, as a result of the decreased fatigue strength of shaft material. The fracture occurred at the fillet root of flange connected to the propeller-shaft, where high stress concentration was caused by geometry design. Deep circumferential machining grooves were present on the fillet root of flange for additive stress concentration. The inhomogeneities acted as potential sites for fatigue crack initiation. The low fatigue strength of shaft material promoted initiation and propagation of fatigue cracks in the weaker region under the reversed torsion loading. The static strength analysis of intermediate shaft was performed to assess the design implications. The measured average ultimate strength of failed intermediate shaft was 12% lower than the lower limit in Rule for Classification of Sea-going Steel Ships issued by China Classification Society. The safety factor of the failed intermediate shaft is lower than the permitted one.

Rough Set Neural Network Feature Extraction and Pattern Recognition of Shaft Orbits Based on the Zernike Moment

In the shaft axis monitoring of hydrogenerating unit condition monitoring and fault diagnosis, the shaft orbit is intuitive and comprehensively reflects the unit operation state, and different shaft orbits correspond to different fault types, which can accurately indicate a system vibration fault. Shaft orbit identification has important significance for vibration fault diagnosis. In getting the feature extraction and pattern recognition of a shaft orbit, the Zernike moment is better than the Hu moment; it has the advantages of a small calculation error and a high recognition rate. A rough set neural network (RS-BP hybrid model) of shaft orbit recognition is established, which uses just 13 moment eigenvalues reserved by the rough set feature selection algorithm as input variables; it has the same calculation error and recognition rate and reduces the calculation time step. The simulation of the recognition of shaft orbits shows that the hybrid model has achieved good results in the identification of shaft orbits.

Measuring standing hindfoot alignment: reliability of different approaches in conventional x-ray and cone-beam CT

IntroductionCurrently there is no consensus how hindfoot alignment (HA) should be assessed in CBCT scans. The aim of this study is to investigate how the reliability is affected by the anatomical structures chosen for the measurement.Materials and methodsDatasets consisting of a Saltzman View (SV) and a CBCT of the same foot were acquired prospectively and independently assessed by five raters regarding HA. In SVs the HA was estimated as follows: transversal shift between tibial shaft axis and heel contact point (1); angle between tibial shaft axis and a tangent at the medial (2) or lateral (3) calcaneal wall. In CBCT the HA was estimated as follows: transversal shift between the centre of the talus and the heel contact point (4); angle between a perpendicular line and a tangent at the medial (5) or lateral (6) calcaneal wall; angle between the distal tibial surface and a tangent at the medial calcaneal wall (7). Intraclass correlation coefficients (ICC) were calculated to assess inter-rater reliability. A linear regression was performed to compare the different measurement regarding their correlation.Results32 patients were included in the study. The ICCs for the measurements 1–7 were as follows: (1) 0.924 [95% CI 0.876–0.959] (2) 0.533 [95% CI 0.377–0.692], (3) 0.553 [95% CI 0.399–0.708], (4) 0.930 [95% CI 0.866–0.962], (5) 0.00 [95% CI − 0.111 to 0.096], (6) 0.00 [95% CI − 0.103 to 0.111], (7) 0.152 [95% CI 0.027–0.330]. A linear regression between measurement 1 and 4 showed a correlation of 0.272 (p = 0.036).ConclusionsIt could be shown that reliability of measuring HA depends on the investigated anatomical structure. Placing a tangent along the calcaneus (2, 3, 5, 6, 7) was shown to be unreliable, whereas determining the weight-bearing heel point (1, 4) appeared to be a reliable approach. The correlation of the measurement workflows is significant (p = 0.036), but too weak (0.272) to be used clinically.

INFLUENCE OF AXIAL PRELOAD FORCES ON RESIDUAL STRESSES DURING TURNING

An analytical calculation of the values of the warping of the axis of a long shaft from the stresses created by the preload force of the rear center of the workpiece machine is carried out. Recommendations are given to reduce the effect of this factor on the amount of warping of the shaft. The material can be used by engineering and technical employees of enterprises.

Influence of selected plane on the evaluation of tibial tunnel locations using a three-dimensional bone model in double-bundle anterior cruciate ligament reconstruction

BackgroundThe purpose of this study was to investigate the influence of a selected plane on the evaluation of tibial tunnel locations following anterior cruciate ligament reconstruction (ACLR) between two planes: the plane parallel to the tibial plateau (Plane A) and the plane perpendicular to the proximal tibial shaft axis (Plane B). MethodsThirty-four patients who underwent double-bundle ACLR were included. Three-dimensional model of tibia was created using computed tomography images 2 weeks postoperatively, and tibial tunnels of the anteromedial bundle (AMB) and posterolateral bundle (PLB) were extracted. To evaluate tibial tunnel locations, two planes (Planes A and B) were created. The locations of the tibial tunnel apertures of each bundle were evaluated using a grid method and compared between Planes A and B. The difference in coronal alignment between Planes A and B were also assessed. ResultsThe AMB and PLB tunnel apertures in Plane A were significantly more laterally located than in Plane B (mean difference; AMB, 1.5%; PLB, 1.7%, P < 0.01). There were no significant differences in the anteroposterior direction between the planes. Coronal alignment difference between the planes was 16.8 ± 2.2°; Plane B was more valgus than Plane A. ConclusionAlthough tibial tunnel locations were not significantly influenced by the selected planes in the AP direction, subtle but statistically significant differences were found in the ML direction between the Planes A and B in double-bundle anterior cruciate ligament reconstruction. The findings suggest that both Planes A and B can be used in the assessment of tibial tunnel locations after anterior cruciate ligament reconstruction.

Misalignment Detection of a Rotating Machine Shaft Using a Support Vector Machine Learning Algorithm

Fault diagnosis for rotating machinery is important for reliability and safety, and shaft misalignment is one of the most common causes of mechanical vibration or shaft failure. In this study, we detected defects caused by misalignment of the shaft axis in rotating machinery using an artificial intelligence machine learning technique for fault recognition. Unlike other methods that focus on the time domain, we changed vibration data in the time domain to the power spectrum component value in the frequency domain. Then, the power spectrum values​ were classified using principle component analysis (PCA). Based on the results, defects are determined using a machine learning technique that uses a support vector machine (SVM). The results show that defects can be quickly determined from only vibration data about normal and abnormal states. By using the proposed pre-processing method, the machine learning framework based on vibration data can be effectively applied to diagnosis not only shaft defects but also faults of other rotating machines such as motors and engines

Primary total hip arthroplasty using a short bone-conserving stem in young adult osteoporotic patients with Dorr type C femoral bone

BackgroundDorr type C femoral bone exhibits a wide, stovepipe-shaped femoral canal, and thin cortices in the proximal femur. Dorr C bone combined with severe osteoporosis is an important challenge in primary hip arthroplasty. In this study, we assessed the effects of short metaphyseal fitting cementless stems on preformatted primary total hip arthroplasties in young adult osteoporotic patients with this femoral presentation.MethodsA total of 42 hip arthroplasties were performed in 35 young patients (range 20 to 36 years) using a short Tri-lock bone preservation metaphyseal-fitting cementless femoral component between 2012 and 2017. The mean age at surgery of the 27 male (33 hips) and 8 female (9 hips) patients was 27.5 years (range 20.3 to 35.8 years). The mean body mass index (BMI) was 20.2 kg/m2 (range, 16.8–23.2 kg/m2). According to Dorr’s criteria, all 42 femora were classified as type C bone and all femurs suffered from severe osteoporosis (Singh index ≤ 3).ResultsThe mean follow-up period was 5.5 years (range 3.0 to 8.0 years). The clinical and functional results improved for the Harris hip score, WOMAC, and UCLA activity scores. The Harris Hip score improved from 48.0 ± 8.0 (range 38.0 to 61.0) preoperatively to 87.0 ± 9.0 (range 77.0 to 92.0) at 12 months after surgery and 91.0 ± 8.0 (range 85.0 to 98.0) at final follow-up. The preoperative UCLA activity score was 3.0 ± 0.5 points (range, 1.0–4.0 points), which significantly improved to 7.5 ± 0.7 points (range 6.0 to 8.0 points) at the final follow-up. No patient exhibited thigh pain at the final follow-up. The mean stem-to-canal fill percentages were 97% ± 2.1% (anteroposterior view at midstem). For stem alignment, 40 hips (95.2%) of the femoral stem were positioned neutrally to 3° of varus with reference to the femoral shaft axis. The remaining two were positioned at 4° varus to 4° valgus. Radiographic evaluation showed good osteointegration of the implants in follow-up.ConclusionsBased on the tapered-wedge design and proximal porous coating, the shortened tapered conventional stem can achieve reliable stability through neck filling and metaphyseal fixation, which does not depend on the isthmus hoop stress. This stem was suitable in severe osteoporotic patients with type C bones in young adults who presented with a correspondingly straightened femoral canal with a wide isthmus and thin cortex.

Application of Threadless Screw to Precise Linear Positioning

This paper presents a mechanism for linear movement which could be called threadless screw, in which a roller is pushed toward a rotating plain shaft and rotates with it. The roller moves on a helical path when its axis is not parallel to the axis of the shaft. Therefore, the roller moves in direction of the shaft axis, just as linear movement of a nut on a screw. The lead of this mechanism is not only a function of diameter of the shaft, but also the angle between axes of the roller and the shaft which gives the possibility to change the lead continuously from very fine to very rough leads. On the other hand the accuracy of this mechanism depends on the accuracy of a plain cylindrical surface which can be fabricated very accurately compared with the threads of a screw. Two configurations of this mechanism were designed and fabricated to verify the idea. Coarse and fine positioning speeds are 10 and 0.1 mm/sec over an effective range of 200 mm, respectively. The experimental results show that the fast positioning over wide range of movement with resolution of 10 nm is possible by this mechanism. Further investigation shows that applying thrust loads have considerable effect on the lead of the mechanism.

Micro Hierarchical Structure and Mechanical Property of Sparrow Hawk (Accipiter nisus) Feather Shaf

In this study, the real 3D model of the feather shaft that is composed of medulla and cortex is characterized by X-ray computer tomography, and the structural features are quantitatively analyzed. Compression and tensile tests are conducted to evaluate the mechanical performance of the feather shaft and cortex at different regions. The analysis of the 3D model shows that the medulla accounts for ∼70% of the shaft volume and exhibits a closed-cell foam-like structure, with a porosity of 59%. The cells in the medulla show dodecahedron and decahedron morphology and have an equivalent diameter of ∼30 μm. In axial compression, the presence of medulla enhances the shaft stability. Especially, the combined effect of the medulla and cortex increases the buckling strength of the middle and distal shaft by 77% and 141%, respectively, compared to the calculated value of the shaft using linear mixed rule. The tensile properties of the cortex along the shaft axis are anisotropic because of the different fiber structures. As the fiber orientation gradually becomes uniform in the axial direction, the Young’s modulus and tensile strength of the cortex on the dorsal gradually increase from calamus to the distal shaft, and the fracture mode changes from tortuous fracture to V-shaped fracture. The cortex on the lateral shows the opposite trend, that is the distal shaft becomes weaker due to fiber tangles.

АНАЛІЗ МЕТОДІВ ОБРОБКИ ШАТУННИХ ШИЙОК КОЛІНЧАСТИХ ВАЛІВ ОРІЄНТОВАНИМ ІНСТРУМЕНТОМ

Crankshafts are quite common parts made in the automotive, shipbuilding, machine-building and other industries. They have a complex shape, also it is necessary to ensure high accuracy and productivity during processing. Analysis of crankshaftmachining methods is an urgent task.Analysis of known processing methods, identification of their advantages anddisadvantages will pay more attention to unresolved issues and further improve of the processing process.Known methods of processing connecting rod necks of crankshafts are considered. Nowadays grinding and milling are most often used. Milling can be a tool in which the cutting inserts are on the outside of the disk and on the inside. Many companies manufacture machines that are self-adjusting for processing, as well as flexible systems for processing various crankshafts. Most often, machines are designedto process the crankshaft for one institution.Lack of analysis of known methods of processing connecting rod necks of crankshafts.Analyze the known methods of processing connecting rod necks of crankshafts.This article is a review. Methods of crankshaft processing are considered. Processing of connecting rod necks takes more time, and is also more difficult in comparison with processing of radical necks as axes of these necks are not on a shaft axis. Processing of a cranked shaft for one fastening is more productive than for several fastenings. Processing of connecting rod necks of cranked shafts can take place with use of special devices or according to the program on CNC machines.The analysis of the known methods of grinding and milling of crankshaft necks was carried out in the article.

A new method for evaluation of patellar height and the position of the joint line before and after total knee arthroplasty

BackgroundThe measurement of patellar height and restoration of the natural position of the joint line are crucial to total knee arthroplasty (TKA). However, there remains a lack of consensus on an optimal measurement method to associate the patellar height with the joint line position. The objective of this study was to introduce a new method and validate the application in TKA both preoperatively and postoperatively.MethodsInstead of taking marginal landmarks as the tibial references, the tibial shaft axis was used to construct the new measurement method, which comprises the axis-patella (AP), joint axis-patella (jAP) indices and joint line height (JLH). Patellar heights were measured using the Insall-Salvati (IS), modified Insall-Salvati (mIS), Blackburne-Peel (BP), Caton-Deschamps (CD) indices, and the new method in 175 knees both preoperatively and postoperatively. Intraclass correlation coefficients and Pearson’s correlation analyses were respectively used to evaluate the reliabilities and correlations.ResultsThere were good correlations between the proposed method and the mIS, CD, and BP indices. High inter-observer reproducibility was found for AP (preoperative and postoperative 0.83), jAP (preoperative 0.82; postoperative 0.86) indices and JLH (preoperative 0.88; postoperative 0.95). High intra-observer repeatability was also found for AP (preoperative 0.85; postoperative 0.87), jAP (preoperative 0.83; postoperative 0.87) indices and JLH (preoperative 0.80; postoperative 0.92).ConclusionsThe new method is reliable for measuring patellar height before and after TKA, providing an alternative to distinguish between true and pseudo patella baja. Furthermore, JLH can be applied to assess and restore the joint line position in TKA.

Method of calculating the contact pressure of the cuff on the shaft

The calculation of the pressure in the connection "shaft — radial lip seal" with a seal in the form of a rubber reinforced cuff is proposed. An algorithm for calculating the contact pressure is obtained taking into account the properties of the material, thickness and angle of inclination to the shaft axis of the pressing section of the cuff, the tensile force of the spring, and the geometric parameters of the free section of the cuff. Keywords: lip seal, contact pressure, axisymmetric problem. B-Mikhael@yandex.ru, ommelnikov@mail.ru

Two reconstruction plates provide superior stability of displaced midshaft clavicle fractures in comparison to single plating – A biomechanical study

BackgroundDisplaced midshaft fractures are the most common surgically treated clavicle fractures. However, they are associated with high complication rates following plating due to fixation failure in terms of plate breakage, screw breakage and/or screw loosening. The aim of this study was to compare the biomechanical competence of three different plating techniques for fixation of displaced midshaft clavicle fractures. MethodsDisplaced midshaft fractures type 2B according to the Robinson classification were simulated by standardized osteotomy gap in 18 synthetic clavicles, assigned to three groups (n = 6) for plating with either superiorly placed Dynamic Compression Plate (width/thickness 11.0/4.0 mm), locked Superior Anterior Clavicle Locking Compression Plate (width/thickness 10.2/2.0 mm), or two non-locked Reconstruction Plates placed superiorly and anteriorly (width/thickness 10.0/2.8 mm). Each specimen was cyclically tested at 3 Hz under craniocaudal cantilever bending, superimposed with torsion around the shaft axis over 720′000 cycles or until failure occurred. The latter was defined by plate breakage, screw breakage or screw loosening. FindingsInitial construct stiffness (N/mm) and cycles to failure in group Reconstruction Plates (22.30 ± 4.07; 712′778 ± 17′691) were significantly higher compared with both groups Compression Plate (12.53 ± 2.09; 348′541 ± 212′941) and Locking Plate (4.19 ± 0.46; 19′536 ± 3′586), p ≤ 0.019. In addition, these two outcomes were significantly higher in group Compression Plate versus Locking Plate, p ≤ 0.029. InterpretationDouble plating of unstable midshaft clavicle fractures with reconstruction plates seems to provide superior fixation stability under dynamic loading, when compared to single compression or locked plating, whereas the latter is associated with inferior performance.