Rehabilitation versus surgical reconstruction for non-acute anterior cruciate ligament injury (ACL SNNAP): a pragmatic randomised controlled trial

Background: Anterior cruciate ligament (ACL) rupture is a common debilitating injury that can cause instability of the knee. We aimed to investigate the best management strategy between reconstructive surgery and non-surgical treatment for patients with a non-acute ACL injury and persistent symptoms of instability. Methods: We did a pragmatic, multicentre, superiority, randomised controlled trial in 29 secondary care National Health Service orthopaedic units in the UK. Patients with symptomatic knee problems (instability) consistent with an ACL injury were eligible. We excluded patients with meniscal pathology with characteristics that indicate immediate surgery. Patients were randomly assigned (1:1) by computer to either surgery (reconstruction) or rehabilitation (physiotherapy but with subsequent reconstruction permitted if instability persisted after treatment), stratified by site and baseline Knee Injury and Osteoarthritis Outcome Score—4 domain version (KOOS4). This management design represented normal practice. The primary outcome was KOOS4 at 18 months after randomisation. The principal analyses were intention-to-treat based, with KOOS4 results analysed using linear regression. This trial is registered with ISRCTN, ISRCTN10110685, and ClinicalTrials.gov, NCT02980367. Findings: Between Feb 1, 2017, and April 12, 2020, we recruited 316 patients. 156 (49%) participants were randomly assigned to the surgical reconstruction group and 160 (51%) to the rehabilitation group. Mean KOOS4 at 18 months was 73·0 (SD 18·3) in the surgical group and 64·6 (21·6) in the rehabilitation group. The adjusted mean difference was 7·9 (95% CI 2·5–13·2; p=0·0053) in favour of surgical management. 65 (41%) of 160 patients allocated to rehabilitation underwent subsequent surgery according to protocol within 18 months. 43 (28%) of 156 patients allocated to surgery did not receive their allocated treatment. We found no differences between groups in the proportion of intervention-related complications. Interpretation: Surgical reconstruction as a management strategy for patients with non-acute ACL injury with persistent symptoms of instability was clinically superior and more cost-effective in comparison with rehabilitation management. Funding: The UK National Institute for Health Research Health Technology Assessment Programme

A Compliant Visco-Plastic Particle Contact Model Based on Differential Variational Inequalities ✩

This work describes an approach to simulate contacts between threedimensionalshapeswithcomplianceanddampingusingtheframeworkofthe differential variational inequality theory. Within the context of nonsmooth dynamics, we introduce an extension to the classical set-valued model for frictional contacts between rigid bodies, allowing contacts to experience local compliance, viscosity, and plasticization. Different types of yield surfaces can be defined for various types of contact, a versatile approach that contains the classic dry Coulomb friction as a special case. The resulting problem is a differential variational inequality that can be solved, at each integration time step, as a variational inequality over a convex set

A Rosenbrock–Nystrom state space implicit approach for the dynamic analysis of mechanical systems: I -- theoretical formulation

When performing dynamic analysis of a constrained mechanical system, a set of index three differential-algebraic equations (DAE) describes the time evolution of the system. The paper presents a state space based method for the numerical solution of the resulting DAE. A subset of so-called independent generalized coordinates, equal in number to the number of degrees of freedom of the mechanical system, is used to express the time evolution of the mechanical system. The second-order state space ordinary differential equations (SSODE) that describe the time variation of independent coordinates are numerically integrated using a Rosenbrock-type formula specialized to second-order systems of differential equations. Rosenbrock methods are known to be efficient for medium accuracy integration of stiff systems; they do not require the solution of non-linear systems for the stage values, and possess optimal linear stability properties for stiff integration. The computation of exact Jacobians needed by Rosenbrock formulas is discussed in the context of multibody systems. The companion paper [19] discusses a choice of method coefficients based on a four-stage L-stable Rosenbrock formula and presents numerical results

A Rosenbrock–Nystrom state space implicit approach for the dynamic analysis of mechanical systems: II -- method and numerical examples

When performing dynamic analysis of a constrained mechanical system, a set of index three differential-algebraic equations (DAE) describes the time evolution of the system. A state-space based method for the numerical solution of the resulting DAE has also been developed. The numerical method uses a linearly implicit time stepping formula of the Rosenbrock type, which is suitable for medium accuracy integration of stiff systems. This paper discusses choices of method coefficients and presents numerical results. For stiff mechanical systems, the proposed algorithm is shown to reduce significantly simulation times when compared to state of the art existent algorithms. The better efficiency is due to the use of an L-stable integrator, and a rigorous and general approach to providing analytical derivatives required by it

Coupled numerical simulation of floating offshore wind turbine platforms: investigating the effects of wave and wind loading using a high-fidelity SPH-based model

In order to enhance the overall comprehension of floating offshore wind turbine (FOWT) performance, a detailed investigation into the dynamic response of a commonly used floater type, namely the tension-leg platform tension-leg platform (TLP), has been undertaken. The objective is to utilize high-fidelity numerical tools to analyze and characterize the expected forces in the anchoring systems resulting from combined actions of sea waves and wind. To capture the coupled effects of waves and wind, a reliable dataset is generated through a high-fidelity computational fluid dynamic stool. This tool is essential to capturing the nonlinearities inherent in the interaction between waves and low surgestiffnes splatforms, such as the TLP being studied here.The outcomes of this study, presented as a survivor analysis, aim to provide insight into the characteristic values that arise from various load combinations in the mooring system, considering the specific environmental conditions at the site. Given the challenging nature faced by FOWTs, the analysis will primarily focus on extreme loading cases, accounting for the global motions induced by wind thrust when the turbine is in survival mode (i.e., parked conditions).<br/

Analysis of Rotating Systems Using General-Purpose Multibody Dynamics

This work illustrates the application of general-purpose multibody formulations to the analysis of rotating systems dynamics. Various benchmark problems encompassing multiple deformable components are presented and analyzed. The suitability of the approach is assessed and conclusions are drawn on the basis of correlating the numerical simulations with analogous examples from the open literature

Simulation of surface strain in tibiofemoral cartilage during walking for the prediction of collagen fibre orientation

<p>The collagen fibres in the superficial layer of tibiofemoral articular cartilage exhibit distinct patterns in orientation revealed by split lines. In this study, we introduce a simulation framework to predict cartilage surface loading during walking to investigate if split line orientations correspond with principal strain directions in the cartilage surface. The two-step framework uses a multibody musculoskeletal model to predict tibiofemoral kinematics which are then imposed on a deformable model to predict surface strains. The deformable model uses absolute nodal coordinate formulation (ANCF) shell elements to represent the articular surface and a system of spring-dampers and internal pressure to represent the underlying cartilage. Simulations were performed to predict surface strains due to internal pressure, loading induced by walking, and the combination of both loading due to pressure and walking. Peak femoral and tibial cartilage deflections were slightly greater than 1 mm during simulated walking. First principal strain magnitudes within the cartilage surface ranged up to 3%. Time-averaged first principal strains agreed best with split line maps from the literature when surface loading due to internal cartilage pressure was included. This result suggests there may be a connection between pressure-induced surface strain patterns and the collagen fibre orientation patterns that emerge.</p