Nonanatomic Placement of Posteromedial Meniscal Root Repairs: A Finite Element Study

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Brett D. Steineman ◽  
Robert F. LaPrade ◽  
Tammy L. Haut Donahue
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Contact Area ◽  
Hoop Stress ◽  
Meniscal Extrusion ◽  
Meniscal Root ◽  
Knee Mechanics ◽  
Total Contact Area ◽  
And Cartilage ◽  
Element Study

Abstract Nonanatomic placement of posteromedial meniscal root repairs alters knee mechanics; however, little is known about how the position and magnitude of misplacement affect knee mechanics. Finite element knee models were developed to assess changes in cartilage and meniscus mechanics for anatomic and various nonanatomic repairs with respect to intact. In total, 25 different repair locations were assessed at loads of 500 N and 1000 N. The two-simple-suture method was represented within the models to simulate posteromedial meniscal root repairs. Anatomic repairs nearly restored total contact area; however, meniscal hoop stress decreased, meniscal extrusion increased, and cartilage–cartilage contact area increased. Repairs positioned further posterior altered knee mechanics the most and repairs positioned further anterior restored knee mechanics for posteromedial root repairs. Despite this, repair tension increased with further anterior placement. Anterior placement of repairs results in more restorative contact mechanics than posterior placement; however, anterior placement also increased the risk of suture cut-out or failure following repairs. Anatomic placement of repairs remains the best option because of the risks involved with anterior placement; however, suture methods need to be improved to better restore the strength of repairs to that of the native insertion. Proper placement of repairs is important to consider with meniscal root repairs because misplacement may negatively affect cartilage and meniscus mechanics in patients.

scholarly journals A 3D study of the contact surface developed by the contact between the tires and the structural pavements

Exacta ◽  
2009 ◽  
Vol 6 (2) ◽  
pp. 197-208
Author(s):  
Alex Alves Bandeira ◽  
Rita Moura Fortes ◽  
João Virgílio Merighi
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Contact Area ◽  
Augmented Lagrangian Method ◽  
Numerical Results ◽  
Real Contact Area ◽  
The Real ◽  
Real Contact ◽  
Commercial Program ◽  
Contact Surfaces

The basic aim in this work is to present a new technique to analyze the contact surfaces developed by the contact between the tires and the structural pavements by numerical simulations, using 3D finite element formulations with contact mechanics. For this purpose, the Augmented Lagrangian method is used. This study is performed just putting the tires on the structural pavement. These tires and the structural pavement are discretized by finite elements under large 3D elastoplastic deformation. The real loads (of aircrafts, trucks or cars) are applied directly on each tire and by contact mechanics procedures, the real contact area between the tires and the pavement surface is computed. The penetration conditions and the contact interfaces are investigated in details. Furthermore, the pressure developed at the contact surfaces is automatically calculated and transferred to the structural pavement by contact mechanics techniques. The purpose of this work research is to show that the contact area is not circular and the finite element techniques can calculate automatically the real contact area, the real geometry and its stresses and strains. In the end of this work, numerical results in terms of geometry, stress and strain are presented and compared to show the ability of the algorithm. These numerical results are also compared with the numerical results obtained by the commercial program ANSYS.

scholarly journals A 3D study of the contact surface developed by the contact between the tires and the structural pavements DOI: 10.5585/exacta.v6i2.797

Exacta ◽  
2009 ◽  
Vol 6 (2) ◽  
pp. 197-208
Author(s):  
Alex Alves Bandeira ◽  
Rita Moura Fortes ◽  
João Virgílio Merighi
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Contact Area ◽  
Augmented Lagrangian Method ◽  
Numerical Results ◽  
Real Contact Area ◽  
The Real ◽  
Real Contact ◽  
Commercial Program ◽  
Contact Surfaces

The basic aim in this work is to present a new technique to analyze the contact surfaces developed by the contact between the tires and the structural pavements by numerical simulations, using 3D finite element formulations with contact mechanics. For this purpose, the Augmented Lagrangian method is used. This study is performed just putting the tires on the structural pavement. These tires and the structural pavement are discretized by finite elements under large 3D elastoplastic deformation. The real loads (of aircrafts, trucks or cars) are applied directly on each tire and by contact mechanics procedures, the real contact area between the tires and the pavement surface is computed. The penetration conditions and the contact interfaces are investigated in details. Furthermore, the pressure developed at the contact surfaces is automatically calculated and transferred to the structural pavement by contact mechanics techniques. The purpose of this work research is to show that the contact area is not circular and the finite element techniques can calculate automatically the real contact area, the real geometry and its stresses and strains. In the end of this work, numerical results in terms of geometry, stress and strain are presented and compared to show the ability of the algorithm. These numerical results are also compared with the numerical results obtained by the commercial program ANSYS.

scholarly journals Thin-coating contact mechanics with adhesion

2006 ◽  
Vol 21 (10) ◽  
pp. 2660-2668 ◽  
Author(s):  
E.D. Reedy
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Contact Area ◽  
Elementary Theory ◽  
Compressive Load ◽  
Square Root ◽  
Thin Coating ◽  
Element Analysis ◽  
Linear Elastic ◽  
Element Simulation

An elementary theory for a rigid spherical indenter contacting a thin, linear elastic coating that is bonded to a rigid substrate was developed. This theory predicts that contact area varies as the square root of the compressive load in contrast to Hertz theory where contact area varies as the two-thirds power of the compressive load. Finite element analysis confirmed an approximate square root dependence of contact area on compressive load when the coating thickness-to-indenter radius ratio is less than 0.1 and when the coating Poisson’s ratio is less than 0.45. Thin-coating contact mechanics theories that use either the Derjaguin-Muller-Toporov (DMT) approximation or the Johnson-Kendall-Roberts (JKR) approximation were also developed. In addition, a finite element simulation capability that includes adhesion was developed and verified. Illustrative finite element simulations that include adhesion were then performed for a thin elastic coating (rigid indenter/substrate). Results were compared with the thin-coating contact theories and the transition from DMT-like to JKR-like response was examined.

Contact Area and Static Friction of Rough Surfaces With High Plasticity Index

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
L. Li ◽  
I. Etsion ◽  
F. E. Talke
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
Present Model ◽  
Rough Surfaces ◽  
Static Friction ◽  
Plasticity Index ◽  
High Plasticity ◽  
Spherical Surfaces ◽  
Trans Asme ◽  
Element Study

A model for the contact area and static friction of nominally flat rough surfaces and rough spherical surfaces is presented. The model extends previously published models, which are limited to plasticity index values below 8, to higher plasticity index values by accounting for fully plastically deformed asperities based on finite element results by Jackson and Green [2005, “A Finite Element Study of Elasto-Plastic Hemispherical Contact Against a Rigid Flat,” Trans. ASME, J. Tribol., 127, pp. 343–354]. The present model also corrects some deficiencies of the earlier models at very small plasticity index values below 0.5.

scholarly journals The Problems of Meniscal Root Tears

2020 ◽  
pp. 51-60
Author(s):  
I.M. Zazirnyi ◽  
O.O. Kostrub ◽  
R. Smigielski ◽  
A. Andreev
Keyword(s):  
Articular Cartilage ◽  
Clinical Outcomes ◽  
Contact Area ◽  
Surgical Repair ◽  
Root Avulsion ◽  
Meniscal Extrusion ◽  
Early Osteoarthritis ◽  
Meniscal Root ◽  
Hoop Stresses ◽  
Contact Pressures

Meniscal root tears are defined as radial tears located within 1 cm from the meniscal attachment or a bony root avulsion. This injury is biomechanically comparable to a total meniscectomy, leading to compromised hoop stresses resulting in decreased tibiofemoral contact area and increased contact pressures in the involved compartment. These changes are detrimental to the articular cartilage and ultimately lead to the development of early osteoarthritis. Surgical repair is the treatment of choice in patients without significant osteoarthritis (Outerbridge grades 3 or 4). Root repairs have been reported to improve clinical outcomes, decrease meniscal extrusion and slow the onset of degenerative changes. In this article, we describe the anatomy, biomechanics, clinical evaluation, treatment methods, outcomes, and post-operative rehabilitation for posterior meniscal root tears.

Loosening of Posteromedial Meniscal Root Repairs Affects Knee Mechanics: A Finite Element Study

2021 ◽  
Author(s):  
Brett Steineman ◽  
Robert LaPrade ◽  
Tammy Haut Donahue
Keyword(s):  
Finite Element ◽  
Mechanical Response ◽  
Compressive Force ◽  
Initial Position ◽  
Meniscal Root ◽  
Knee Mechanics ◽  
Root Repair ◽  
Intact Condition ◽  
Hoop Stresses ◽  
Better Than

Abstract Meniscal root repairs are susceptible to unrecoverable loosening that may displace the meniscus from the initial position reduced during surgery. Despite this, the effects of a loosened meniscal root repair on knee mechanics are unknown. We hypothesized that anatomic root repairs without loosening would restore knee mechanics to the intact condition better than loosened anatomic root repairs, but that loosened repairs would restore mechanics better than untreated meniscal root tears. Finite element knee models were used to evaluate changes in cartilage and meniscus mechanics due to repair loosening. The mechanical response from loosened anatomic root repairs was compared to anatomic repairs without loosening and untreated root tears. All conditions were evaluated at three flexion angles, 0°, 30°, and 60°, and a compressive force of 1,000 N to simulate return-to-activity loading. The two-simple-suture method was represented within the models to simulate posteromedial meniscal root repairs and repair loosening was derived from previous biomechanical experimental data. Loosening decreased hoop stresses throughout the meniscus, increased posterior extrusion, and shifted loading through the meniscus-cartilage region to the cartilage-cartilage region compared to the anatomic root repair without loosening. Despite differences between repairs and loosened repairs, the changes from loosened repairs more closely resembled the anatomic repair without loosening than the untreated root repair condition. Therefore, root repairs are susceptible to loosening that will prevent a successful initial repair from remaining in the intended position and will alter mechanics, although repairs that loosen appear better than leaving tears untreated.

Finite Element Predictions of Labrum and Cartilage Mechanics in Dysplastic Human Hips

2011 ◽  
Author(s):  
Corinne R. Henak ◽  
Ryan S. Davis ◽  
Benjamin J. Ellis ◽  
Michael D. Harris ◽  
Andrew E. Anderson ◽  
...  
Keyword(s):  
Finite Element ◽  
Femoral Head ◽  
Contact Area ◽  
Acetabular Dysplasia ◽  
Clinical Observation ◽  
Mechanical Load ◽  
Early Osteoarthritis ◽  
Cartilage Mechanics ◽  
Subject Specific ◽  
And Cartilage

Acetabular dysplasia, characterized by a shallow acetabulum and decreased coverage of the femoral head (Figure 1), is thought to cause early osteoarthritis due to altered mechanical loading. Clinical observation of hypertrophic labra in dysplastic hips suggests that the labrum supports mechanical load (e.g., [1]). Simulations have predicted increased cartilage contact pressure and decreased contact area in dysplastic hips as potential causes of early osteoarthritis (e.g., [2]), but have been limited by the use of simplified geometry and the omission of the labrum. The objective of this study was to compare labrum and cartilage mechanics between normal and dysplastic hips using a validated approach to subject-specific finite element modeling of the hip.

Utilization of Transtibial Centralization Suture Best Minimizes Extrusion and Restores Tibiofemoral Contact Mechanics for Anatomic Medial Meniscal Root Repairs in a Cadaveric Model

2019 ◽  
Vol 47 (7) ◽  
pp. 1591-1600 ◽  
Author(s):  
Blake T. Daney ◽  
Zachary S. Aman ◽  
Joseph J. Krob ◽  
Hunter W. Storaci ◽  
Alex W. Brady ◽  
...  
Keyword(s):  
Contact Mechanics ◽  
Contact Pressure ◽  
Posterior Border ◽  
Root Tear ◽  
Meniscal Extrusion ◽  
3 Dimensional ◽  
Anatomic Repair ◽  
Pull Out ◽  
Meniscal Root ◽  
Root Repair

Background: Although posterior medial meniscal root (PMMR) repairs are often successful, postoperative meniscal extrusion after a root repair has been identified as a potential clinical problem. Purpose/Hypothesis: The purpose was to quantitatively evaluate the tibiofemoral contact mechanics and extent of meniscal extrusion after a PMMR repair. It was hypothesized that the addition of a centralization suture (into the posterior medial tibial plateau) would help restore normal joint load-bearing characteristics and restore the native amount of meniscal extrusion after a root tear. Furthermore, we hypothesized that the amount of meniscal extrusion would be greatest in loaded and flexed knees when measured at the posterior border of the medial collateral ligament (MCL). Study Design: Controlled laboratory study. Methods: Meniscal extrusion and tibiofemoral contact mechanics were measured using 3-dimensional digitization and pressure sensors in 10 nonpaired, human cadaveric knees. The PMMR of each knee was tested under 6 states: (1) intact; (2) type 2A PMMR tear; (3) anatomic transtibial pull-out root repair; (4) anatomic transtibial pull-out repair with centralization; (5) nonanatomic transtibial pull-out repair; and (6) nonanatomic transtibial pull-out repair with centralization, with randomization of the order of conditions 3 and 4, and 5 and 6. The testing protocol loaded knees with a 1000-N axial compressive force at 4 flexion angles (0°, 30°, 60°, 90°) in each state. Meniscal extrusion was measured with a 3-dimensional coordinate digitizer at 0° and 90° in both the loaded and unloaded states and calculated from the difference from the articular margin of the tibia to the periphery of the meniscus. Peak contact pressure, contact area, and total contact pressure were also recorded for all states at all flexion angles. Statistical analysis investigated the independent effects of flexion, state, and loading using 3 distinct 2-factor models. Results: Differences in the contact mechanics between repair techniques were most notable at higher flexion angles, demonstrating significantly higher average and peak contact pressures for nonanatomic repair states when compared with anatomic repairs with and without centralization (all P < .05). In unloaded knees at full extension, the magnitude of medial meniscal extrusion was significantly higher at the posterior border of the MCL compared with the posterior medial tibia ( P < .001) and adjacent to the root attachment on the tibia locations ( P < .001). Both anatomic repair states had no significant difference in the degree of extrusion when compared with the intact state. Conclusion: The anatomic transtibial pull-out root repair and the anatomic transtibial pull-out root repair with centralization techniques best restored contact mechanics of the knee and meniscal extrusion when compared with root tear and nonanatomic repair states at time zero. There were no significant differences in contact pressure or magnitude of extrusion between the anatomic repair state and the anatomic repair with centralization state. We found that extrusion is best measured in the coronal plane at the posterior border of the MCL for unloaded knees. However, the degree of extrusion increased as the knee was loaded and flexed to 90°. Clinical Relevance: When there are concerns about meniscal extrusion with a medial meniscal root repair, the addition of a centralization suture may be beneficial for patients in reducing pathologic meniscal extrusion and restoring joint contact mechanics.

scholarly journals SIMPLIFIED VERSUS REAL GEOMETRY FINGERTIP MODELS: A FINITE ELEMENT STUDY TO PREDICT FORCE–DISPLACEMENT RESPONSE UNDER FLAT CONTACT COMPRESSION

2018 ◽  
Vol 18 (04) ◽  
pp. 1850048
Author(s):  
JEREMY DALLARD ◽  
SONIA DUPREY ◽  
XAVIER MERLHIOT
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
Mechanical Response ◽  
Medical Images ◽  
Displacement Response ◽  
Real Geometry ◽  
Force Displacement ◽  
Flat Contact ◽  
Visible Human ◽  
Element Study

Finite element fingertip models are useful tools to assess product ergonomics. While “real geometry” approaches provide accurate results, developing models requires medical images. “Simpified geometry” approaches have to date not been tested to see whether they can provide equally accurate results in terms of mechanical response, i.e. force-displacement response and dimensions of fingertip contact area. Four fingertip models were built either from medical images (Visible Human project) or from simplified geometries. Simulations of fingertip flat contact compression at 20[Formula: see text] were performed. A 2nd order hyperelastic material property was used to effectively reproduce the mechanical behavior of the fingertip. Models based on simplified geometries such as conics proved as accurate as models reconstructed from medical images. However, accurate positioning of the bony phalanx is paramount if a biofidelic mechanical response is to be reproduced.

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