Biomechanical Analysis of a Radial Expansion Mechanism of Intestinal Robot Coupling with Hyperelastic Intestinal Wall

This paper proposes a new type of radial expansion mechanism by adopting the scissor type telescopic design for intestinal robot to meet the requirements of the intestinal robot’s movement and residence in the intestinal tract.The robot’s maximum expansion radius is up to 25mm,which can well adapt to the intestinal tract with different diameters.At first,the mathematical model of the scissors-type telescopic mechanism(STM)is established to further study its dynamics characteristics by theoretical analysis and simulation.Then,in order to study the coupling effect between the STM and intestinal wall,the strain-energy function of Fung-type is used to establish the constitutive model of intestinal wall.Moreover,aimed at solving the non-convergence problem caused by the selection of material parameters in general Fung-type model,the restrictions for selecting material parameters were given by using positive definite matrix theory.Furthermore,the motion coupling characteristics between the mechanism and intestinal wall were analyzed by using the finite element method.The result shows that if the expansion radius of the STM exceeds a certain value,the intestinal wall may reach its deformation limit,which means that the maximum rotating angle of the three-claw butterfly disc of STM can be decided based on the maximum deformation stress of the intestinal wall.Therefore,it provides a design basis for formulating a reasonable expansion radius in mechanism control to avoid damage to the intestinal wall.

Biomechanical Analysis of Personalised 3D-Printed Clavicle Plates of Different Materials to Treat Midshaft Clavicle Fractures

This study was aimed at comparing the biomechanical performance of personalised 3D-printed clavicle plates of different materials to treat midshaft clavicle fractures with the finite element(FE)method.The FE model of a fractured clavicle with a personalised 3D-printed clavicle plate and screws was constructed.Three types of materials were simulated,including stainless steel,titanium alloy,and magnesium alloy.Two loading conditions(axial compression and inferior bending)were applied at the distal end of the clavicle to simulate arm abduction.Plate stiffness,peak stress,and bone strain at the clavicle fracture site were measured and compared.The stiffness of the stainless steel clavicle plate was significantly greater than that of the titanium alloy clavicle plate.The stiffness of the magnesium alloy clavicle plate was similar to that of the intact clavicle;peak stress of the magnesium alloy clavicle plate was the lowest;thus,it had less stress-shielding effects on bone formation.The magnesium alloy clavicle plate was more likely to form bone by distributing proper strain at the clavicle fracture site.According to the influence of different materials on the tensile strength,magnesium alloy clavicle plates might be preferred owing to their bionic stiffness in the treatment of patients with a low risk of falling.For patients who engage in contact sports,a titanium alloy clavicle plate might be more suitable.

Evaluation of biodegradable electric conductive tube-guides and mesenchymal stem cells

AIM: To study the therapeutic effect of three tubeguides with electrical conductivity associated to mesenchymal stem cells(MSCs) on neuro-muscular regeneration after neurotmesis.METHODS: Rats with 10-mm gap nerve injury were tested using polyvinyl alcohol(PVA), PVA-carbon nanotubes(CNTs) and MSCs, and PVA-polypyrrole(PPy). The regenerated nerves and tibialis anterior muscles were processed for stereological studies after 20 wk. The functional recovery was assessed serially for gait biomechanical analysis, by extensor postural thrust, sciatic functional index and static sciatic functionalindex(SSI), and by withdrawal reflex latency(WRL). In vitro studies included cytocompatibility, flow cytometry, reverse transcriptase polymerase chain reaction and karyotype analysis of the MSCs. Histopathology of lung, liver, kidneys, and regional lymph nodes ensured the biomaterials biocompatibility. RESULTS: SSI remained negative throughout and independently from treatment. Differences between treted groups in the severity of changes in WRL existed, showing a faster regeneration for PVA-CNTs-MSCs(P < 0.05). At toe-off, less acute ankle joint angles were seen for PVA-CNTs-MSCs group(P = 0.051) suggesting improved ankle muscles function during the push off phase of the gait cycle. In PVA-PPy and PVA-CNTs groups, there was a 25% and 42% increase of average fiber area and a 13% and 21% increase of the "minimal Feret's diameter" respectively. Stereological analysis disclosed a significantly(P < 0.05) increased myelin thickness(M), ratio myelin thickness/axon diameter(M/d) and ratio axon diameter/fiber diameter(d/D; g-ratio) in PVA-CNT-MSCs group(P < 0.05). CONCLUSION: Results revealed that treatment with MSCs and PVA-CNTs tube-guides induced better nerve fiber regeneration. Functional and kinematics analysis revealed positive synergistic effects brought by MSCs and PVA-CNTs. The PVA-CNTs and PVA-PPy are promising scaffolds with electric conductive properties, bio- and cytocompatible that might prevent the secondary neurogenic muscular atrophy by improving the reestablishment of the neuro-muscular junction.

Fibula pro-tibia vs standard locking plate fixation in an ankle fracture saw bone model

BACKGROUND Locking plate fixation in osteoporotic ankle fractures may fail due to cut-out or metalwork failure.Fibula pro-tibia fixation was a technique prior to the advent of locking plates that was used to enhance stability in ankle fractures by achieving tri or tetra-cortical fixation.With locking plates,the strength of this fixation construct can be further enhanced.There is lack of evidence currently on the merits of tibiapro-fibula augmented locking plate fixation of unstable ankle fractures.AIM To assess if there is increased strength to failure,in an ankle fracture saw bone model,with a fibula pro-tibia construct when compared with standard locking plate fixation.METHODS Ten osteoporotic saw bones with simulated supination external rotation injuries were used.Five saw bones were fixed with standard locking plates whilst the other 5 saw bones were fixed with locking plates in a fibula pro-tibia construct.The fibula pro-tibia construct involved fixation with 3 consecutive locking screws applied across 3 cortices proximally from the level of the syndesmosis.All fixations were tested in axial external rotation to failure on an electromagnetic test frame(MTS 858 Mini-Bionix test machine,MTS Corp,Eden Praire,MN,United States).Torque at 30 degrees external rotation,failure torque,and external rotation angle at failure were compared between both groups and statistically analyzed.RESULTS The fibula pro-tibia construct demonstrated a statistically higher torque at 30 degrees external rotation(4.421±0.796 N/m vs 1.451±0.467 N/m;t-test P=0.000),as well as maximum torque at failure(5.079±0.694N/m vs 2.299±0.931 N/m;t-test P=0.001)compared to the standard locking plate construct.The fibula pro-tibia construct also had a lower external rotation angle at failure(54.7±14.5 vs 67.7±22.9).CONCLUSION The fibula pro-tibia locking plate construct demonstrates biomechanical superiority to standard locking plates in fixation of unstable ankle fractures in this saw bone model.There is merit in the use of this construct in patients with unstable osteoporotic ankle fractures as it may aid improved clinical outcomes.

Clinical Application and Exploration on Steps Progressively Corrections and Gradual Shortening Combined with Total Spinal Osteotomy for Angular Kyphosis—Basic Research and Clinical Application

Introduction: This study is designed to explore the biomechanical principles of posterior bilateral pedicle screw on steps progressively and tight closure on every step for severe angular kyphosis and the indication conditions and clinical pathways of above new technique. Materials and Methods: A total of 90 patients have severe angular kyphosis, 37 males and 53 females, with an average age of 47 years. All patients were treated with posterior bilateral pedicle screw and step tight closure for gradual shortening and orthopedic technology. Results: Average intraoperative blood loss was 2089 ml. Average operation time was 326 minutes. Kyphotic angle changed from 90.1° averagely preoperatively to 41.6° averagely postoperatively with an improvement rate of 65%. The distance from C7 plumb line to posterior upper edge of the S1 vertebral body was averagely 5.2 mm postoperatively, with a correction rate of 73%. Neurological complications occurred in 2 cases, accounting for 6%. Non-neurological complications occurred in 2 cases, accounting for 6%. Anatomical parameters were significantly improved postoperatively (P < 0.05). All patients were averagely followed up for 28 months. Segments undergoing osteotomy achieved bone fusion, without loss of orthopedic angle. Conclusions: The orthopedic technology of bilateral pedicle screw and step tight closure designed by human physiology and biomechanical principles can protect spinal cord cells from injury to the utmost. To choose an appropriate osteotomy plane during pre-surgical planning can make the repair results closer to the normal function of the spine. Intraoperative nerve root protection, full release and bone graft fusion are effective safeguards to ensure kyphosis correction and to avoid spine lateral offset.

A new computational approach for modeling diffusion tractography in the brain

Computational models provide additional tools for studying the brain,however,many techniques are currently disconnected from each other.There is a need for new computational approaches that span the range of physics operating in the brain.In this review paper,we offer some new perspectives on how the embedded element method can fill this gap and has the potential to connect a myriad of modeling genre.The embedded element method is a mesh superposition technique used within finite element analysis.This method allows for the incorporation of axonal fiber tracts to be explicitly represented.Here,we explore the use of the approach beyond its original goal of predicting axonal strain in brain injury.We explore the potential application of the embedded element method in areas of electrophysiology,neurodegeneration,neuropharmacology and mechanobiology.We conclude that this method has the potential to provide us with an integrated computational framework that can assist in developing improved diagnostic tools and regeneration technologies.