scholarly journals Study of the Polycarbonate-Urethane/Metal Contact in Different Positions during Gait Cycle

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Sergio Gabarre ◽  
Antonio Herrera ◽  
Jesús Mateo ◽  
Elena Ibarz ◽  
Antonio Lobo-Escolar ◽  
...  
Keyword(s):  
Body Weight ◽  
Young Patients ◽  
Element Model ◽  
Heel Strike ◽  
Virtual Surgery ◽  
Wear Rates ◽  
Polycarbonate Urethane ◽  
Value Range ◽  
Joint Contact ◽  
Contact Pressures

Nowadays, a growing number of young and more active patients receive hip replacement. More strenuous activities in such patients involve higher friction and wear rates, with friction on the bearing surface being crucial to ensure arthroplasty survival in the long term. Over the last years, the polycarbonate-urethane has offered a feasible alternative to conventional bearings. A finite element model of a healthy hip joint was developed and adjusted to three gait phases (heel strike, mid-stance, and toe-off), serving as a benchmark for the assessment of the results of joint replacement model. Three equivalent models were made with the polycarbonate-urethane Tribofit system implanted, one for each of the three gait phases, after reproducing a virtual surgery over the respective healthy models. Standard body-weight loads were considered: 230% body-weight toe-off, 275% body-weight mid-stance, and 350% body-weight heel strike. Contact pressures were obtained for the different models. When comparing the results corresponding to the healthy model to polycarbonate-urethane joint, contact areas are similar and so contact pressures are within a narrower value range. In conclusion, polycarbonate-urethane characteristics are similar to those of the joint cartilage. So, it is a favorable alternative to traditional bearing surfaces in total hip arthroplasty, especially in young patients.

Clinical Replacement Strategies for Meniscus Tissue Deficiency

Cartilage ◽  
2021 ◽  
pp. 194760352110605
Author(s):  
Dean Wang ◽  
Erik Gonzalez-Leon ◽  
Scott A. Rodeo ◽  
Kyriacos A. Athanasiou
Keyword(s):  
Young Patients ◽  
Return To Sport ◽  
Short Term ◽  
Clinical Challenge ◽  
Meniscus Tissue ◽  
Collagen Meniscus Implant ◽  
Sport Activities ◽  
Joint Contact ◽  
Contact Pressures

Meniscus tissue deficiency resulting from primary meniscectomy or meniscectomy after failed repair is a clinical challenge because the meniscus has little to no capacity for regeneration. Loss of meniscus tissue has been associated with early-onset knee osteoarthritis due to an increase in joint contact pressures in meniscectomized knees. Clinically available replacement strategies range from allograft transplantation to synthetic implants, including the collagen meniscus implant, ACTIfit, and NUSurface. Although short-term efficacy has been demonstrated with some of these treatments, factors such as long-term durability, chondroprotective efficacy, and return to sport activities in young patients remain unpredictable. Investigations of cell-based and tissue-engineered strategies to treat meniscus tissue deficiency are ongoing.

scholarly journals Computationally Efficient Magnetic Resonance Imaging Based Surface Contact Modeling as a Tool to Evaluate Joint Injuries and Outcomes of Surgical Interventions Compared to Finite Element Modeling

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Joshua E. Johnson ◽  
Phil Lee ◽  
Terence E. McIff ◽  
E. Bruce Toby ◽  
Kenneth J. Fischer
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Joint Mechanics ◽  
Computationally Efficient ◽  
Efficient Manner ◽  
Element Modeling ◽  
Joint Injuries ◽  
Surface Contact ◽  
Joint Contact ◽  
Contact Pressures

Joint injuries and the resulting posttraumatic osteoarthritis (OA) are a significant problem. There is still a need for tools to evaluate joint injuries, their effect on joint mechanics, and the relationship between altered mechanics and OA. Better understanding of injuries and their relationship to OA may aid in the development or refinement of treatment methods. This may be partially achieved by monitoring changes in joint mechanics that are a direct consequence of injury. Techniques such as image-based finite element modeling can provide in vivo joint mechanics data but can also be laborious and computationally expensive. Alternate modeling techniques that can provide similar results in a computationally efficient manner are an attractive prospect. It is likely possible to estimate risk of OA due to injury from surface contact mechanics data alone. The objective of this study was to compare joint contact mechanics from image-based surface contact modeling (SCM) and finite element modeling (FEM) in normal, injured (scapholunate ligament tear), and surgically repaired radiocarpal joints. Since FEM is accepted as the gold standard to evaluate joint contact stresses, our assumption was that results obtained using this method would accurately represent the true value. Magnetic resonance images (MRI) of the normal, injured, and postoperative wrists of three subjects were acquired when relaxed and during functional grasp. Surface and volumetric models of the radiolunate and radioscaphoid articulations were constructed from the relaxed images for SCM and FEM analyses, respectively. Kinematic boundary conditions were acquired from image registration between the relaxed and grasp images. For the SCM technique, a linear contact relationship was used to estimate contact outcomes based on interactions of the rigid articular surfaces in contact. For FEM, a pressure-overclosure relationship was used to estimate outcomes based on deformable body contact interactions. The SCM technique was able to evaluate variations in contact outcomes arising from scapholunate ligament injury and also the effects of surgical repair, with similar accuracy to the FEM gold standard. At least 80% of contact forces, peak contact pressures, mean contact pressures and contact areas from SCM were within 10 N, 0.5 MPa, 0.2 MPa, and 15 mm2, respectively, of the results from FEM, regardless of the state of the wrist. Depending on the application, the MRI-based SCM technique has the potential to provide clinically relevant subject-specific results in a computationally efficient manner compared to FEM.

Analysis of Premium Connection of Connecting and Sealing Ability Loaded by Axial Tensile Loads

2012 ◽  
Vol 268-270 ◽  
pp. 737-740
Author(s):  
Yang Yu ◽  
Yi Hua Dou ◽  
Fu Xiang Zhang ◽  
Xiang Tong Yang
Keyword(s):  
Finite Element ◽  
Contact Pressure ◽  
Tensile Load ◽  
Element Model ◽  
Sealing Ability ◽  
Axial Tensile ◽  
High Level ◽  
Maximum Contact ◽  
Contact Pressures ◽  
The Finite Element Model

It is necessary to know the connecting and sealing ability of premium connection for appropriate choices of different working conditions. By finite element method, the finite element model of premium connection is established and the stresses of seal section, shoulder zone and thread surface of tubing by axial tensile loads are analyzed. The results show that shoulder zone is subject to most axial stresses at made-up state, which will make distribution of stresses on thread reasonable. With the increase of axial tensile loads, stresses of thread on both ends increase and on seal section and shoulder zone slightly change. The maximum stress on some thread exceed the yield limit of material when axial tensile loads exceed 400KN. Limited axial tensile loads sharply influence the contact pressures on shoulder zone while slightly on seal section. Although the maximum contact pressure on shoulder zone drop to 0 when the axial tensile load is 600KN, the maximum contact pressure on seal section will keep on a high level.

Effect of Sorafenib on Sex Hormone Levels in Male Swiss Albino Mice

2021 ◽  
pp. 3883-3888
Author(s):  
Surekha D. Shetty ◽  
Laxminarayana Bairy K. ◽  
AM Prasad ◽  
Satheesha Nayak B. ◽  
Ashwini Aithal P.
Keyword(s):  
Body Weight ◽  
Semen Analysis ◽  
Young Patients ◽  
Differentiated Thyroid Carcinoma ◽  
Positive Control ◽  
Vital Role ◽  
Reproductive Age ◽  
Control Group ◽  
Swiss Albino Mice ◽  
Albino Mice

Background: Hormones play a vital role in initiating and maintenance of male reproductive or testicular function which includes the production of androgens and spermatozoa. Testosterone is essential for the initiation and maintenance of spermatogenesis. FSH is responsible for the stimulation of spermatogenesis. Semen analysis and hormone evaluation are essential parameters in the diagnosis of infertility in males. Objective: The aim of the present study is to evaluate the effect of sorafenib on FSH and intratesticular testosterone levels in male Swiss albino mice. Materials and Methods: The animals were segregated into control, positive control, and treatment groups (n=6). Treatment group received 25, 50 and 100 mg/kg body weight of sorafenib orally for seven consecutive days at intervals of 24 hours between two administrations. Positive control group received 100 mg/kg body weight of imatinib. The animals were sacrificed at the end of 1st, 2nd, 4th, 5th, 7th and 10th week after the last exposure to sorafenib. Results: The intratesticular testosterone level was significantly (P<0.05) reduced in treated groups and severe effect was observed on week 4th and 5th weeks. FSH level was increased significantly (P<0.05) in sorafenib treated groups of mice. Conclusion: The administration of sorafenib does affect testosterone and FSH level significantly, but this effect is reversible once the drug is withdrawn. This finding may help the clinicians to plan and address the fertility-related issues in young patients of reproductive age who are being treated with sorafenib for advanced renal cell carcinoma, hepatocellular carcinoma and differentiated thyroid carcinoma.

Can the Hip Joint be Modeled Accurately Using Simplified Geometry?

2008 ◽  
Author(s):  
Andrew E. Anderson ◽  
Steve A. Maas ◽  
Benjamin J. Ellis ◽  
Jeffrey A. Weiss
Keyword(s):  
Contact Pressure ◽  
Hip Joint ◽  
Spherical Geometry ◽  
Model Complexity ◽  
Hip Morphology ◽  
Joint Contact ◽  
Analytical Approaches ◽  
Contact Pressures ◽  
In Vitro Data

Simplified analytical approaches to estimate hip joint contact pressures using perfectly spherical geometry have been described in the literature (rigid body spring models); however, estimations based on these simulations have not corresponded well with experimental in vitro data. Recent evidence from our laboratory suggests that finite element (FE) models of the hip joint that incorporate detailed geometry for cartilage and bone can predict cartilage pressures in good agreement with experimental data [1]. However, it is unknown whether this degree of model complexity is necessary. The objective of this study was to compare cartilage contact pressure predictions from FE models with varying degrees of simplicity to elucidate which aspects of hip morphology are required to obtain accurate predictions of cartilage contact pressure. Models based on 1) subject-specific (SS) geometry, 2) spheres, and 3) rotational conchoids were analyzed.

Assessment of the Effects of Diabetes on Midfoot Joint Pressures Using a Robotic Gait Simulator

2009 ◽  
Vol 30 (8) ◽  
pp. 767-772 ◽  
Author(s):  
Dong Gil Lee ◽  
Brian L. Davis
Keyword(s):  
Stance Phase ◽  
Walking Speed ◽  
Normal Population ◽  
Human Gait ◽  
Diabetic Patients ◽  
Foot Deformity ◽  
Charcot Neuroarthropathy ◽  
Joint Contact ◽  
Peak Pressures ◽  
Contact Pressures

Background: One of the more serious diabetic complications is Charcot neuroarthropathy (CN), a disease that results in arch collapse and permanent foot deformity. However, very little is known about the etiology of CN. From a mechanical standpoint, it is likely that there is a “vicious circle” in terms of (i) arch collapse causing increased midfoot joint pressures, and (ii) increased joint contact pressures exacerbating the collapse of midfoot bones. This study focused on assessment of peak joint pressure difference between diabetic and non-diabetic cadaver feet during simulated walking. We hypothesized that joint pressures are higher for diabetics than normal population. Materials and Methods: Sixteen cadaver foot specimens (eight control and eight diabetic specimens) were used in this study. Human gait at 25% of typical walking speed (averaged stance duration of 3.2s) was simulated by a custom-designed Universal Musculoskeletal Simulator. Four medial midfoot joint pressures (the first metatarsocuneiform, the medial naviculocuneiform, the middle naviculocuneiform, and the first intercuneiform) were measured dynamically during full stance. Results: The pressures in each of the four measured midfoot joints were significantly greater in the diabetic feet ( p = 0.015, p = 0.025, p < 0.001, and p = 0.545, respectively). Conclusion: Across all four tested joints, the diabetic cadaver specimens had, on average, 46% higher peak pressures than the control cadaver feet during the simulated stance phase. Clinical Relevance: This finding suggests that diabetic patients could be predisposed to arch collapse even before there are visible signs of bone or joint abnormalities.

scholarly journals Biomechanics of a novel extra-articular implant for younger patients with knee osteoarthritis

2018 ◽  
Vol 4 (1) ◽  
pp. 203-205
Author(s):  
Mehdi Saeidi ◽  
Maziar Ramezani ◽  
Piaras Kelly ◽  
Mohd Sabri Hussin ◽  
Thomas Neitzert
Keyword(s):  
Knee Joint ◽  
Cartilage Regeneration ◽  
Stress Distributions ◽  
Element Analysis ◽  
Medial Side ◽  
Pressure Distributions ◽  
Joint Contact ◽  
As Stress ◽  
Joint Contact Pressure ◽  
Contact Pressures

AbstractThis research aimed to study the efficacy of a novel implant for osteoarthritic knees. This implant is designed to eliminate excessive loads through the knee and to provide suitable conditions for possible tibiofemoral cartilage regeneration. The implant was designed for the medial side of the knee joint. Finite Element Analysis (FEA) was performed for an extended knee position of the knee joint. Contact pressure distributions on the medial and lateral compartments were investigated as well as stress distributions throughout the implant’s plates. Results with and without the implant were compared, and it was seen that the contact pressures on the surface of the distal femur were reduced by more than 90% after the introduction of the implant.

scholarly journals Translational PBPK Modeling of the Protein Therapeutic and CD95L Inhibitor Asunercept to Develop Dose Recommendations for Its First Use in Pediatric Glioblastoma Patients

Pharmaceutics ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 152 ◽  
Author(s):  
Nina Hanke ◽  
Claudia Kunz ◽  
Meinolf Thiemann ◽  
Harald Fricke ◽  
Thorsten Lehr
Keyword(s):  
Body Weight ◽  
Clinical Investigation ◽  
Young Patients ◽  
Study Data ◽  
Pbpk Modeling ◽  
Dose Selection ◽  
Clinical Phase ◽  
Protein Therapeutic ◽  
Pediatric Glioblastoma ◽  
Dose Recommendations

The protein therapeutic and CD95L inhibitor asunercept is currently under clinical investigation for the treatment of glioblastoma and myelodysplastic syndrome. The purpose of this study was to predict the asunercept pharmacokinetics in children and to give dose recommendations for its first use in pediatric glioblastoma patients. A physiologically-based pharmacokinetic (PBPK) model of asunercept in healthy and diseased adults was successfully developed using the available clinical Phase I and Phase II study data. This model was then extrapolated to different pediatric populations, to predict the asunercept exposure in children and to find equivalent starting doses. Simulation of the asunercept serum concentration-time curves in children between 1–18 years of age shows that a dosing regimen based on body weight results in a similar asunercept steady-state exposure in all patients (pediatric or adult) above 12 years of age. For children between 1–12 years, higher doses per kg body weight are recommended, with the highest dose for the very young patients. Translational PBPK modeling is strongly encouraged by regulatory agencies to help with the initial dose selection for pediatric trials. To our knowledge, this is the first report of pediatric PBPK to support the dose selection of a therapeutic protein before its administration to children.

Reliability Study of the Hydraulically Expanded Tube-to-Tubesheet Joint

2005 ◽  
Vol 128 (3) ◽  
pp. 408-413 ◽  
Author(s):  
Caifu Qian ◽  
Chenghong Duan ◽  
Hongjie Yu ◽  
Hongwei Duan ◽  
Junli Tian
Keyword(s):  
Finite Element ◽  
Contact Surface ◽  
Three Dimensional ◽  
Element Model ◽  
Tube Sheet ◽  
Reliability Study ◽  
Pull Out ◽  
Finite Element Calculations ◽  
Grooved Tube ◽  
Contact Pressures

A three-dimensional parametrized finite element model is established for the nonlinear analysis of the hydraulically expanded tube-to-tubesheet joint. Distribution of the residual contact pressure on the contact surface between the tube and the tubesheet is investigated. It is found that sealing circular bands exist on the contact surface which enhance the sealing of the joint since the residual contact pressures on the sealing circular bands are higher than on other positions. The sealing circular bands are located close to the two ends of the hole when it is not grooved, but they are located at the two brinks of the groove for a grooved hole and in the latter case, the residual contact pressures are even higher, reflecting that the joint with a grooved tube-sheet hole is more capable of sealing. Experiments and finite element calculations for the pull-out force of the joint are also performed for different expansion pressures and groove widths. Results show that with the increase of the groove width, the measured pull-out force increases significantly and becomes larger and larger than the calculated one, which is owing to the scratch on the contact surface between the tube and tubesheet.

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