scholarly journals The Effect of Enzymatic Crosslink Degradation on the Mechanics of the Anterior Cruciate Ligament: A Hybrid Multi-Domain Model

2021 ◽  
Vol 11 (18) ◽  
pp. 8580
Author(s):  
Fadi Al Khatib ◽  
Afif Gouissem ◽  
Armin Eilaghi ◽  
Malek Adouni
Keyword(s):  
Cruciate Ligament ◽  
Three Dimensional ◽  
Domain Model ◽  
Coarse Grained ◽  
Elastic Response ◽  
Type I ◽  
Coarse Grained Model ◽  
Promising Tool ◽  
Collagen Molecules ◽  
Anterior Cruciate

The anterior cruciate ligament’s (ACL) mechanics is an important factor governing the ligament’s integrity and, hence, the knee joint’s response. Despite many investigations in this area, the cause and effect of injuries remain unclear or unknown. This may be due to the complexity of the direct link between macro- and micro-scale damage mechanisms. In the first part of this investigation, a three-dimensional coarse-grained model of collagen fibril (type I) was developed using a bottom-up approach to investigate deformation mechanisms under tensile testing. The output of this molecular level was used later to calibrate the parameters of a hierarchical multi-scale fibril-reinforced hyper-elastoplastic model of the ACL. Our model enabled us to determine the mechanical behavior of the ACL as a function of the basic response of the collagen molecules. Modeled elastic response and damage distribution were in good agreement with the reported measurements and computational investigations. Our results suggest that degradation of crosslink content dictates the loss of the stiffness of the fibrils and, hence, damage to the ACL. Therefore, the proposed computational frame is a promising tool that will allow new insights into the biomechanics of the ACL.

scholarly journals Cruciate Ligament Cell Sheets Can Be Rapidly Produced on Thermoresponsive poly(glycidyl ether) Coating and Successfully Used for Colonization of Embroidered Scaffolds

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 877
Author(s):  
Ingrid Zahn ◽  
Daniel David Stöbener ◽  
Marie Weinhart ◽  
Clemens Gögele ◽  
Annette Breier ◽  
...  
Keyword(s):  
Gene Expression ◽  
Type I Collagen ◽  
Cruciate Ligament ◽  
Glycidyl Ether ◽  
Stable Gene ◽  
Type I ◽  
Cell Sheets ◽  
Thermoresponsive Polymers ◽  
Related Phenotype ◽  
Anterior Cruciate

Anterior cruciate ligament (ACL) cell sheets combined with biomechanically competent scaffolds might facilitate ACL tissue engineering. Since thermoresponsive polymers allow a rapid enzyme-free detachment of cell sheets, we evaluated the applicability of a thermoresponsive poly(glycidyl ether) (PGE) coating for cruciate ligamentocyte sheet formation and its influence on ligamentocyte phenotype during sheet-mediated colonization of embroidered scaffolds. Ligamentocytes were seeded on surfaces either coated with PGE or without coating. Detached ligamentocyte sheets were cultured separately or wrapped around an embroidered scaffold made of polylactide acid (PLA) and poly(lactic-co-ε-caprolactone) (P(LA-CL)) threads functionalized by gas-phase fluorination and with collagen foam. Ligamentocyte viability, protein and gene expression were determined in sheets detached from surfaces with or without PGE coating, scaffolds seeded with sheets from PGE-coated plates and the respective monolayers. Stable and vital ligamentocyte sheets could be produced within 24 h with both surfaces, but more rapidly with PGE coating. PGE did not affect ligamentocyte phenotype. Scaffolds could be colonized with sheets associated with high cell survival, stable gene expression of ligament-related type I collagen, decorin, tenascin C and Mohawk after 14 d and extracellular matrix (ECM) deposition. PGE coating facilitates ligamentocyte sheet formation, and sheets colonizing the scaffolds displayed a ligament-related phenotype.

A new model for packing of type-I collagen molecules in the native fibril

1981 ◽  
Vol 1 (10) ◽  
pp. 801-810 ◽  
Author(s):  
Karl A. Piez ◽  
Benes L. Trus
Keyword(s):  
Type I Collagen ◽  
Hexagonal Lattice ◽  
Three Dimensional ◽  
Equatorial Region ◽  
Type I ◽  
X Ray Diffraction ◽  
X Ray ◽  
Left Handed ◽  
Crystal Model ◽  
Collagen Molecules

A specific fibril model is presented consisting of bundles of five-stranded microfibrils, which are usually disordered (except axially) but under lateral compression become ordered. The features are as follows (where D = 234 residues or 67 nm): (1) D-staggered collagen molecules 4.5 D long in the helical microfibril have a left-handed supercoil with a pitch of 400–700 residues, but microfibrils need not have helical symmetry. (2) Straight-tilted 0.5-D overlap regions on a near-hexagonal lattice contribute the discrete x-ray diffraction reflections arising from lateral order, while the gap regions remain disordered. (3) The overlap regions are equivalent, but are crystallographically distinguished by systematic displacements from the near-hexagonal lattice. (4) The unit cell is the same as in a recently proposed three-dimensional crystal model, and calculated intensities in the equatorial region of the x-ray diffraction pattern agree with observed values.

Mechanical Simulation of Knee Movement in Basketball Shooting

2013 ◽  
Vol 336-338 ◽  
pp. 760-763
Author(s):  
Hui Yue
Keyword(s):  
Finite Element ◽  
Cruciate Ligament ◽  
Three Dimensional ◽  
Element Model ◽  
Basketball Player ◽  
Knee Movement ◽  
Dimensional Finite Element ◽  
Anterior Cruciate ◽  
Three Dimensional Finite Element

A short explanation of the finite element method as a powerful tool for mathematical modeling is provided, and an application using constitutive modeling of the behavior of ligaments is introduced. Few possible explanations of the role of water in ligament function are extracted from two dimensional finite element models of a classical ligament. The modeling is extended to a three dimensional finite element model for the human anterior cruciate ligament. Simulation of ligament force in pitching motion of basketball player is studied in this paper.

Riboswitch Folds to Holo-Form Like Structure Even in the Absence of Cognate Ligand at High Mg2+ Concentration

2021 ◽  
Author(s):  
Sunil Kumar ◽  
Govardhan Reddy
Keyword(s):  
Specific Binding ◽  
Three Dimensional ◽  
Coarse Grained ◽  
Thiamine Pyrophosphate ◽  
Initial Increase ◽  
Free Energy Surface ◽  
Physiological Concentration ◽  
Coarse Grained Model ◽  
Non Coding Rna ◽  
Thermodynamic Conditions

Riboswitches are non-coding RNA that regulate gene expression by folding into specific three-dimensional structures (holo-form) upon binding by their cognate ligand in the presence of Mg2+. Riboswitch functioning is also hypothesized to be under kinetic control requiring large cognate ligand concentrations. We ask the question under thermodynamic conditions, can the riboswitches populate holo-form like structures in the absence of their cognate ligands only in the presence of Mg2+. We addressed this question using thiamine pyrophosphate (TPP) riboswitch as a model system and computer simulations using a coarse-grained model for RNA. The folding free energy surface (FES) shows that with the initial increase in Mg2+ concentration ([Mg2+]), TPP AD undergoes a barrierless collapse in its dimensions. On further increase in [Mg2+], intermediates separated by barriers appear on the FES, and one of the intermediates has a TPP ligand-binding competent structure. We show that site-specific binding of the Mg2+ aids in the formation of tertiary contacts. For [Mg2+] greater than physiological concentration, AD folds into its holo-form like structure even in the absence of the TPP ligand. The folding kinetics shows that it populates an intermediate due to the misalignment of the two arms in the TPP AD, which acts as a kinetic trap leading to larger folding timescales. The predictions of the intermediate structures from the simulations are amenable for experimental verification.

scholarly journals Arthroscopic Primary Repair of Proximal Anterior Cruciate Ligament Tears: With or Without Additional Suture Augmentation?

2018 ◽  
Vol 6 (7_suppl4) ◽  
pp. 2325967118S0006 ◽  
Author(s):  
Anne Jonkergouw ◽  
Jelle P. van der List ◽  
Gregory S. DiFelice
Keyword(s):  
Range Of Motion ◽  
Patient Reported Outcomes ◽  
Suture Anchor ◽  
Primary Repair ◽  
Cruciate Ligament ◽  
Type I ◽  
Acl Repair ◽  
Patient Reported ◽  
Anterior Cruciate

Objectives: Over the last years, arthroscopic primary repair of anterior cruciate ligament (ACL) tears has shown excellent results owing to appropriate patient selection (only repairing proximal ACL tears and good tissue quality), minimal invasive surgery (arthroscopy) and focus on early range of motion. Some surgeons have repaired proximal ACL tears without suture augmentation while others have used internal suture augmentation to reinforce and thus protect the repaired ligament during range of motion. No studies have yet compared the two surgical techniques. The objective of this study was to compare failure rates, reoperation rates and patient-reported outcomes of arthroscopic primary repair with versus without suture augmentation. Methods: A retrospective search for all patients treated with suture anchor arthroscopic primary ACL repair between April 2008 and June 2016 was performed. All patients with isolated proximal ACL tears (type I) were included. Since the development of internal suture augmentation, this reinforcement was added to the repaired ACLs. Minimum follow-up length was 1.0 years. Results: A total of 56 patients were included (mean age 33 years (range: 14 - 57), 59% male) of which 28 (50%) patients received additional suture augmentation. Mean follow-up was 2.3 years (range: 1.0-9.2). Six of all patients had reruptured their repaired ACL (10.7%), of which four underwent uncomplicated ACL reconstruction and two were treated conservatively. Four reruptures were initially treated with primary repair only (4/28, 14.3%) and two patients with additional suture augmentation (2/28, 7.1%; p = 0.431). During follow-up, three patients underwent reoperation (5.4%; two for medial meniscus tear (one in each group) and one for tibial suture anchor removal of the suture augmentation). Patient-reported outcomes have so far been collected in 20 patients without reruptures (currently collecting), with mean Lysholm score of 96, modified Cincinnati 94, SANE 93, pre-injury Tegner 6.7, postoperative Tegner 6.3 and subjective IKDC 91. Objective IKDC was A in 90%, B in 5%, C in 5%. Conclusion: In this study, the total failure rate of arthroscopic primary ACL repair was 10.7% and was lower with additional suture augmentation (7.1%) than primary repair alone (14.3%). Patients with failed ACL repair underwent uncomplicated primary ACL reconstruction. We recommend adding suture augmentation in high-risk patients (i.e. adolescents, ones with hyperlaxity, high contact sports), to protect the repaired ligament, especially during early range of motion. These data support treating type I proximal ACL tears with arthroscopic primary repair.

Studying the Intact, ACL-Deficient and Reconstructed Human Knee Joint Using a Finite Element Model

2013 ◽  
Author(s):  
Achilles Vairis ◽  
Markos Petousis ◽  
George Stefanoudakis ◽  
Nectarios Vidakis ◽  
Betina Kandyla ◽  
...  
Keyword(s):  
Finite Element ◽  
Knee Joint ◽  
Cruciate Ligament ◽  
Three Dimensional ◽  
Element Model ◽  
Human Knee ◽  
Mechanical Responses ◽  
Human Knee Joint ◽  
Calculated Load ◽  
Anterior Cruciate

The human knee joint has a three dimensional geometry with multiple body articulations that produce complex mechanical responses under loads that occur in everyday life and sports activities. Knowledge of the complex mechanical interactions of these load bearing structures is of help when the treatment of relevant diseases is evaluated and assisting devices are designed. The anterior cruciate ligament in the knee connects the femur to the tibia and is often torn during a sudden twisting motion, resulting in knee instability. The objective of this work is to study the mechanical behavior of the human knee joint in typical everyday activities and evaluate the differences in its response for three different states, intact, injured and reconstructed knee. Three equivalent finite element models were developed. For the reconstructed model a novel repair device developed and patented by the authors was employed. For the verification of the developed models, static load cases presented in a previous modeling work were used. Mechanical stresses calculated for the load cases studied, were very close to results presented in previous experimentally verified work, in both load distribution and maximum calculated load values.

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