scholarly journals Modelling changes in modular taper micromechanics due to surgeon assembly technique in total hip arthroplasty

2020 ◽  
Vol 102-B (7_Supple_B) ◽  
pp. 33-40
Author(s):  
Jonathan A. Gustafson ◽  
Robin Pourzal ◽  
Brett R. Levine ◽  
Joshua J. Jacobs ◽  
Hannah J. Lundberg
Keyword(s):  
Contact Mechanics ◽  
Permanent Deformation ◽  
Implant Design ◽  
Cobalt Chromium ◽  
Stem Taper ◽  
Assembly Technique ◽  
Dynamic Assembly ◽  
Titanium Stem ◽  
Contact Pressures

Aims The aim of this study was to develop a novel computational model for estimating head/stem taper mechanics during different simulated assembly conditions. Methods Finite element models of generic cobalt-chromium (CoCr) heads on a titanium stem taper were developed and driven using dynamic assembly loads collected from clinicians. To verify contact mechanics at the taper interface, comparisons of deformed microgroove characteristics (height and width of microgrooves) were made between model estimates with those measured from five retrieved implants. Additionally, these models were used to assess the role of assembly technique—one-hit versus three-hits—on the taper interlock mechanical behaviour. Results The model compared well to deformed microgrooves from the retrieved implants, predicting changes in microgroove height (mean 1.1 μm (0.2 to 1.3)) and width (mean 7.5 μm (1.0 to 18.5)) within the range of measured changes in height (mean 1.4 μm (0.4 to 2.3); p = 0.109) and width (mean 12.0 μm (1.5 to 25.4); p = 0.470). Consistent with benchtop studies, our model found that increasing assembly load magnitude led to increased taper engagement, contact pressure, and permanent deformation of the stem taper microgrooves. Interestingly, our model found assemblies using three hits at low loads (4 kN) led to decreased taper engagement, contact pressures and microgroove deformations throughout the stem taper compared with tapers assembled with one hit at the same magnitude. Conclusion These findings suggest additional assembly hits at low loads lead to inferior taper interlock strength compared with one firm hit, which may be influenced by loading rate or material strain hardening. These unique models can estimate microgroove deformations representative of real contact mechanics seen on retrievals, which will enable us to better understand how both surgeon assembly techniques and implant design affect taper interlock strength. Cite this article: Bone Joint J 2020;102-B(7 Supple B):33–40.

scholarly journals The role of VPS4 in ESCRT-III polymer remodeling

2019 ◽  
Vol 47 (1) ◽  
pp. 441-448 ◽  
Author(s):  
Christophe Caillat ◽  
Sourav Maity ◽  
Nolwenn Miguet ◽  
Wouter H. Roos ◽  
Winfried Weissenhorn
Keyword(s):  
Active Role ◽  
Mechanistic Models ◽  
Membrane Remodeling ◽  
Filament Formation ◽  
Enveloped Viruses ◽  
Endosomal Sorting ◽  
Membrane Fission ◽  
Dynamic Assembly ◽  
Inside Out

Abstract The endosomal sorting complex required for transport-III (ESCRT-III) and VPS4 catalyze a variety of membrane-remodeling processes in eukaryotes and archaea. Common to these processes is the dynamic recruitment of ESCRT-III proteins from the cytosol to the inner face of a membrane neck structure, their activation and filament formation inside or at the membrane neck and the subsequent or concomitant recruitment of the AAA-type ATPase VPS4. The dynamic assembly of ESCRT-III filaments and VPS4 on cellular membranes induces constriction of membrane necks with large diameters such as the cytokinetic midbody and necks with small diameters such as those of intraluminal vesicles or enveloped viruses. The two processes seem to use different sets of ESCRT-III filaments. Constriction is then thought to set the stage for membrane fission. Here, we review recent progress in understanding the structural transitions of ESCRT-III proteins required for filament formation, the functional role of VPS4 in dynamic ESCRT-III assembly and its active role in filament constriction. The recent data will be discussed in the context of different mechanistic models for inside-out membrane fission.

scholarly journals Evaluation of the behavior system locator associated with a removable partial denture, finite element analysis

2018 ◽  
Vol 25 (2) ◽  
pp. 10
Author(s):  
Medardo Alexander Arenas-Chavarria ◽  
Samuel David Giraldo-Gómez ◽  
Federico Latorre-Correa ◽  
Junes Abdul Villarraga-Ossa
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Permanent Deformation ◽  
Vertical Direction ◽  
Cobalt Chromium ◽  
Removable Partial Denture ◽  
Element Analysis ◽  
Partial Denture ◽  
Solid Works ◽  
Von Mises

Aim: The purpose of this research was to evaluate the behavior of the system locator settings associated with distal extension removable partial denture lower (PPR) by finite element analysis (FEA). Materials and Methods: A Class II Kennedy 3D model using a CAD software Solid Works 2010 (SolidWorks Corp., Concord, MA, USA), and subsequently processed and analyzed by ANSYS Software version Model 14. One (1) was designed implant Tapered Screw -Vent® (ref TSVB10 Zimmer Dental-Carlsbad,CA,USA.) length x 10mm diameter 3.7mm with a 3.5mm platform, internal hexagon with its respective screw fixation; this was located at the tooth 37 as a rear pillar of a PPR, whose major connector was a lingual bar casting (alloy cobalt chromium), based combined (metal/ acrylic) with teeth to replace (37, 36 and 35). Efforts were evaluated von Mises in a 400N load. This analysis allowed assessing the performance of various prosthetic structures modeled and generated effects on bone-implant interface. Results: Differences between the values von Mises in all structures and loads were observed before there was no permanent deformation in any of them. Structures such as bone showed in normal values microstrain. Conclusions: The behavior of the PPRimplant connection, showed a favorable distribution efforts by using a PPR, subjecting it to load in the vertical direction.

Contact patterns in the ankle joint after lateral ligamentous injury during internal rotation: A computational study

2020 ◽  
Vol 235 (1) ◽  
pp. 82-88
Author(s):  
G Marta ◽  
C Quental ◽  
J Folgado ◽  
F Guerra-Pinto
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Internal Rotation ◽  
Ankle Joint ◽  
Ankle Instability ◽  
Computational Study ◽  
Rotational Instability ◽  
Anterior Talofibular Ligament ◽  
Maximum Contact ◽  
Contact Pressures

Lateral ankle instability, resulting from the inability of ankle ligaments to heal after injury, is believed to cause a change in the articular contact mechanics that may promote cartilage degeneration. Considering that lateral ligaments’ insufficiency has been related to rotational instability of the talus, and that few studies have addressed the contact mechanics under this condition, the aim of this work was to evaluate if a purely rotational ankle instability could cause non-physiological changes in contact pressures in the ankle joint cartilages using the finite element method. A finite element model of a healthy ankle joint, including bones, cartilages and nine ligaments, was developed. Pure internal talus rotations of 3.67°, 9.6° and 13.43°, measured experimentally for three ligamentous configurations, were applied. The ligamentous configurations consisted in a healthy condition, an injured condition in which the anterior talofibular ligament was cut, and an injured condition in which the anterior talofibular and calcaneofibular ligaments were cut. For all simulations, the contact areas and maximum contact pressures were evaluated for each cartilage. The results showed not only an increase of the maximum contact pressures in the ankle cartilages, but also novel contact regions at the anteromedial and posterolateral sections of the talar cartilage with increasing internal rotation. The anteromedial and posterolateral contact regions observed due to pathological internal rotations of the talus are a computational evidence that supports the link between a pure rotational instability and the pattern of pathological cartilaginous load seen in patients with long-term lateral chronic ankle instability.

scholarly journals Enhanced Poly(propylene carbonate) with Thermoplastic Networks: A Cross-Linking Role of Maleic Anhydride Oligomer in CO2/PO Copolymerization

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1467 ◽  
Author(s):  
Lijun Gao ◽  
Meiying Huang ◽  
Qifeng Wu ◽  
Xiaodan Wan ◽  
Xiaodi Chen ◽  
...  
Keyword(s):  
Weight Loss ◽  
Maleic Anhydride ◽  
Propylene Carbonate ◽  
Permanent Deformation ◽  
Cross Linking ◽  
Biodegradable Poly ◽  
One Step ◽  
Ft Ir ◽  
Poly Propylene

Cross-linking is an effective way to enhance biodegradable poly(propylene carbonate) (PPC) from CO2 and propylene oxide (PO). Cross-linked PPC can be prepared by one-step terpolymerization of multifunctional third monomers with CO2 and PO. However, few such third monomers are available. Each molecule of maleic anhydride oligomer (MAO) contains more than two cyclic anhydride groups. Here, we use it to synthesize PPC with cross-linked networks by adding a small quantity of MAO (0.625–5 wt% of PO) in CO2/PO copolymerization that was catalyzed by zinc glutarate. The formation of networks in the prepared copolymers was confirmed by the presence of gel in copolymers combined Fourier transform infrared spectroscopy (FT-IR), 1H NMR, and the improved mechanical properties. The 5% weight-loss degradation temperatures and maximum weight-loss degradation temperatures greatly increase up to 289.8 °C and 308.8 °C, respectively, which are remarkably high when compared to those of PPC. The minimum permanent deformation of the copolymers closes to 0, while that of PPC is 173%. The maximum tensile strength of the copolymers is 25.5 MPa higher than that of PPC, reaching 38.4 MPa, and it still has some toughness with the elongation at break of 25%. The above phenomena indicate that MAO that was inserted in PPC chains play a cross-linking role, which results in enhanced thermal stability, dimensional stability, and mechanical strength, comprehensively.

Effects of Quadriceps and Hamstrings Ratio on ACL Strain During Landing Activities

2012 ◽  
Author(s):  
Carmen E. Quatman ◽  
Ata M. Kiapour ◽  
Ali Kiapour ◽  
Jason W. Levine ◽  
Samuel C. Wordeman ◽  
...  
Keyword(s):  
Knee Joint ◽  
Cruciate Ligament ◽  
Acl Injury ◽  
The United States ◽  
Implant Design ◽  
Reconstruction Technique ◽  
Fe Model ◽  
Acl Injuries

Over 100,000 anterior cruciate ligament (ACL) injuries occur annually in the United States [1]. Of these, 70% are classified as non-contact, many of which occur subsequent to a landing from a jump [2]. While most agree that quadriceps (Q) and hamstrings (H) have a significant contribution in knee biomechanics, the role of quadriceps and hamstrings muscle loads and their ratio (Q/H) in ACL injury remains controversial. Understanding muscle recruitment in high risk activities may improve our knowledge of ACL injury mechanisms. Such insight may improve current prevention strategies to decrease the risk of ACL injury and damage to secondary anatomical structures, all of which may in turn minimize associated posttraumatic knee osteoarthritis. As in vivo quantification of muscle loads remains challenging, especially under dynamic conditions, validated finite element (FE) models of the knee can be used to characterize the role of muscle loads in ACL injury. FE analysis has provided considerable insight into knee joint biomechanics, including ligament function, ligament reconstruction technique and implant design. This study utilized a validated FE model of the knee joint to study the effects of quadriceps to hamstrings ratio (Q/H) on ACL strain during a simulated landing from a jump. We hypothesized that both the ratio and magnitude of muscle loads are critical determinants of ACL loading. Further, a threshold may be reached as the magnitude of quadriceps load exceeds hamstrings load.

The impact of capitellar arthroplasty on elbow contact mechanics: Implications for implant design

2011 ◽  
Vol 26 (5) ◽  
pp. 458-463 ◽  
Author(s):  
M.T. Sabo ◽  
H. Shannon ◽  
J. Ng ◽  
L.M. Ferreira ◽  
J.A. Johnson ◽  
...  
Keyword(s):  
Contact Mechanics ◽  
Implant Design ◽  
The Impact

The Role of Implant Design and Soft Tissue Structures on CCK Knee Joint Stability

2010 ◽  
Vol 25 (3) ◽  
pp. e80
Author(s):  
Aamer Malik ◽  
Xiaonan Wang ◽  
Douglas E. Padgett ◽  
Timothy M. Wright
Keyword(s):  
Soft Tissue ◽  
Knee Joint ◽  
Implant Design ◽  
Joint Stability ◽  
Tissue Structures

Effects of Inserting a Pressensor Film Into Articular Joints on the Actual Contact Mechanics

1998 ◽  
Vol 120 (5) ◽  
pp. 655-659 ◽  
Author(s):  
J. Z. Wu ◽  
W. Herzog ◽  
M. Epstein
Keyword(s):  
Contact Mechanics ◽  
Solid Phase ◽  
Elastic Solid ◽  
Fluid Phase ◽  
Measurement Precision ◽  
Inviscid Fluid ◽  
Articular Joint ◽  
Joint Contact ◽  
Contact Pressures ◽  
Fuji Film

Fuji film has been widely used in studies aimed at obtaining the contact mechanics of articular joints. Once sealed for practical use in biological joints, Fuji Pressensor film has a total effective thickness of 0.30 mm, which is comparable to the cartilage thickness in the joints of many small animals. The average effective elastic modulus of Fuji film is approximately 100 MPa in compression, which is larger by a factor of 100–300 compared to that of normal articular cartilage. Therefore, inserting a Pressensor film into an articular joint will change the contact mechanics of the joint. The measurement precision of the Pressensor film has been determined systematically; however, the changes in contact mechanics associated with inserting the film into joints have not been investigated. This study was aimed at quantifying the changes in the contact mechanics associated with inserting sealed Fuji Pressensor film into joints. Spherical and cylindrical articular joint contact mechanics with and without Pressensor film and for varying degrees of surface congruency were analyzed and compared by using finite element models. The Pressensor film was taken as linearly elastic and the cartilage was assumed to be biphasic, composed of a linear elastic solid phase and an inviscid fluid phase. The present analyses showed that measurements of the joint contact pressures with Fuji Pressensor film will change the maximum true contact pressures by 10–26 percent depending on the loading, geometry of the joints, and the mechanical properties of cartilage. Considering this effect plus the measurement precision of the film (approximately 10 percent), the measured joint contact pressures in a joint may contain errors as large as 14–28 percent.

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