Biomechanical Framework Research Articles

Endoscopic versus laparoscopic bariatric procedures: A computational biomechanical study through a patient-specific approach

Background and ObjectivesWithin the framework of computational biomechanics, finite element models of the gastric district could be seen as a potential clinical tool not only to study the effects apported by bariatric surgery, but also to compare different surgical techniques such as the new emerging Endoscopic Sleeve Gastroplasty (ESG) with respect to well-established ones (such as the Laparoscopic Sleeve Gastrectomy, LSG). MethodsThis work realized a fully computational comparison between the outcomes obtained from 10 patient-specific stomach models, which were used to simulate ESG, and the complementary results obtained from models representing the post-LSG of the same subjects. Specifically, once the ESG was simulated, a mechanical stimulus was applied by increasing an intragastric pressure up to a maximum of 5 kPa, in order to replicate the process of food intake, as well as for post-LSG models. Results: Results revealed non negligible differences between the techniques also within the same subject. In particular, not only LSG could lead to a greater reduction in the stomach volume (about 77 % at baseline, which is strictly linked to weight loss), but also influence the gastric distension (12 % less than pre-operative models). On the contrary, if ESG would be performed, a more similar pre-operative mechanical stimulation of the gastric walls may be seen (difference of about 1 %), thus preserving the mechanosensation, but the detriment of the volume reduction (about 56 % at baseline, and even decreases with increasing pressure). Moreover, since results suggested ESG may be more influenced by the pre-operative gastric cavity than LSG, a predictive model was proposed to support the surgical planning and the estimation of the volume reduction after ESG. Conclusions: ESG and LSG have substantial differences in their protocols and post-surgical effects. This work pointed out that variations between the two procedures may be observed also from a computational point of view, especially when including patient-specific geometries. These insights support gastric modelling as a valuable tool to evaluate, design and critically compare emerging bariatric surgical procedures, not only from empirical aspects and clinical outcomes, but also from a mechanical point of view.

Fascicle dynamics of the tibialis anterior muscle reflect whole-body walking economy

Humans can inherently adapt their gait pattern in a way that minimizes the metabolic cost of transport, or walking economy, within a few steps, which is faster than any known direct physiological sensor of metabolic energy. Instead, walking economy may be indirectly sensed through mechanoreceptors that correlate with the metabolic cost per step to make such gait adaptations. We tested whether velocity feedback from tibialis anterior (TA) muscle fascicles during the early stance phase of walking could potentially act to indirectly sense walking economy. As participants walked within a range of steady-state speeds and step frequencies, we observed that TA fascicles lengthen on almost every step. Moreover, the average peak fascicle velocity experienced during lengthening reflected the metabolic cost of transport of the given walking condition. We observed that the peak TA muscle activation occurred earlier than could be explained by a short latency reflex response. The activation of the TA muscle just prior to heel strike may serve as a prediction of the magnitude of the ground collision and the associated energy exchange. In this scenario, any unexpected length change experienced by the TA fascicle would serve as an error signal to the nervous system and provide additional information about energy lost per step. Our work helps provide a biomechanical framework to understand the possible neural mechanisms underlying the rapid optimization of walking economy.

Arterial tissues and their inflammatory response to collagen damage: A continuum in silico model coupling nonlinear mechanics, molecular pathways, and cell behavior

Damage in soft biological tissues causes an inflammatory reaction that initiates a chain of events to repair the tissue. This work presents a continuum model and its in silico implementation that describe the cascade of mechanisms leading to tissue healing, coupling mechanical as well as chemo-biological processes. The mechanics is described by means of a Lagrangian nonlinear continuum mechanics framework and follows the homogenized constrained mixtures theory. Plastic-like damage, growth and remodeling as well as homeostasis are taken into account. The chemo-biological pathways account for two molecular and four cellular species, and are activated by damage of collagen molecules in fibers. To consider proliferation, differentiation, diffusion and chemotaxis of species, diffusion–advection–reaction equations are employed. To the best of authors’ knowledge, the proposed model combines for the first time such high number of chemo-mechano-biological mechanisms in a consistent continuum biomechanical framework. The resulting set of coupled differential equations describe balance of linear momentum, evolution of kinematic variables as well as mass balance equations. They are discretized in time according to a backward Euler finite difference scheme, and in space through a finite element Galerkin discretization. The features of the model are firstly demonstrated presenting the species dynamics and highlighting the influence of damage intensities on the growth outcome. In terms of a biaxial test, the chemo-mechano-biological coupling and the model’s applicability to reproduce normal as well as pathological healing are shown. A last numerical example underlines the model’s applicability to complex loading scenarios and inhomogeneous damage distributions. Concluding, the present work contributes towards comprehensive in silico models in biomechanics and mechanobiology.

Salvage Reconstruction of Oncologic Humeral Defects with Free Fibula Flap after Failure with Prosthesis-based Reconstruction

PURPOSE: Advancements in orthoplastic reconstructive surgery have enabled surgeons to perform limb salvage surgery successfully after long bone tumor extirpation of upper extremities. A variety of reconstructive options (allograft, prosthetics, allograft-prosthetic combination, non-vascularized autografts) exist for surgical rehabilitation of such cases. Even though reconstruction by prosthesis is most commonly used in this setting, the associated risks of mechanical failure, aseptic loosening, and infection, can potentially lead to failure and amputation. Furthermore, revision procedures of the primary surgery after implant failure are complicated by unfavorable local tissue properties like massive bone loss, unreliable local tissue, and osteopenic process of the host bone. Therefore, prosthetic reconstruction is usually undesirable; whereas vascularized bone flaps have proven to be an excellent alternative to restore the biomechanical framework of the limb. Herein, we present the free fibula flap (FFF) used to reconstruct oncological humeral defects previously treated with prosthetic based reconstruction which failed. METHOD: We conducted a retrospective review of patients who underwent salvage of the humeral reconstructions in which the prosthesis failed, during 2009 and 2019. We included patients with previous reconstruction of humeral defects only with prosthetic material and no tissue transfer. All cases were reconstructed with the FFF. The Musculoskeletal Tumor Society (MSTS) scoring system was used to evaluate functional outcomes. RESULTS: The mean age was 24 ± 5.54 years. Six male patients (85.7%) and one female were included (14.3%). None of the patients had comorbidities. Four patients had primitive neuro-ectodermal tumors (57.1%) while three had osteogenic sarcomas (42.9%). All patients had the radial nerve preserved during onco-resection. The average gap between implant surgery and salvage with FFFs was 77.5 ± 49.024 months. The indications for salvage with the FFF were infection of implants (42.9%) and aseptic loosening (57.1%). The defects were located proximally in seven patients (85.7%) and mid-shaft in one patient (14.3%). Seven patients had adjuvant chemotherapy (85.7%), while two had neoadjuvant radiotherapy (28.6%). The defect length after debridement and implant removal was 13 ± 5.62 cm. The fibula head was incorporated in 57.1% of the flaps (n=4). For flap fixation dynamic compression plates was used in one patient (14.3%); number 20 cerclage wiring, prolene mesh, and ethibond was used in another patient (14.3%); K wires were used in four patients (57.1%); and ethibond in 1 patient (14.3%). Only one flap had a double venous anastomosis. Two patients underwent re-exploration of the anastomosis (57.1%), the only flap harvested with a skin paddle required debridement of the cutaneous component (14.3%), and one patient had wound dehiscence (14.3%). Six flaps survived (85.7%). Bone union was achieved at 17 ± 1.25 weeks on average. The average MSTS score was 74.9%. The average follow up was 59.57 ± 43.48 months. CONCLUSION: The FFF is a resourceful alternative for the management of a failed prosthesis after oncologic resection of the proximal and mid-humerus, especially with previously infected prosthetic material. Due to its anatomical shape and the vascularized nature of tissue, the FFF provides a long bone segment for humeral reconstruction.

Biomechanical framework for the inverse dynamic analysis of swimming using hydrodynamic forces from swumsuit

This study aims to integrate an open-source software capable of estimating hydrodynamic forces solely from kinematic data with a full-body biomechanical model of the human body to enable inverse dynamic analyses of swimmers. To demonstrate the methodology, intersegmental forces and joint torques of the lower limbs were computed for a six-beat front crawl swimming motion, acquired at LABIOMEP-UP. The hydrodynamic forces obtained compare well with existing numerical literature. The intersegmental forces and joint torques obtained increase from distal to proximal joints. Overall, the results are consistent with the limited literature on swimming biomechanics, which provides confidence in the presented methodology.

Wang Zongyue's Taijiquan Discourse: the Biomechanics of Dongjin

We present in this following paper a verse-by-verse translation of the Taijiquan Discourse, with annotations in the framework of biomechanics. In the text, dongjin 懂劲 the “comprehension of jin” crystallizes as a central concept. Dongjin can be viewed as how the body comprehends, and interacts functionally with force. While the body relates to force by its strength and functionality, the Taiji body, is considered to be instilled with dongjin, and perceives the force associated with jin (劲) as “soft” (rou) and “hard” (gang), which correspond to the vector quantities of the force, namely, direction and magnitude. In most cases the common response to an attacking force is to fight back, in a direct force- against-force interaction, which creates a “double- weighted” conditions (shuangzhong 双重) that tenses up, and traps the body from being able to maneuver. This renders the body vulnerable. Dongjin enables the body to respond to the incoming force by making postural adjustments to receive force at an angle, at the moment of impact, thus deflecting and mitigating it. In other words, the body uses the rou component (softness) to absorb and neutralize the incoming force. Also, dongjin accords liveliness and spontaneity in the response of rou and gang, which is a fundamental feature of martial skills. Dongjin is more comprehensive than perceiving force as a vector; it enables the body to use the dynamics of rou and gang functionally in its application, with great efficacy. Dongjin forms the biomechanical basis for Taijiquan's key strategy of responding with rou-softness in martial interactions (yi rou wei zhu 以柔为主).

Modelling Wind Damage to Southeastern U.S. Trees: Effects of Wind Profile, Gaps, Neighborhood Interactions, and Wind Direction

Tree damage from a variety of types of wind events is widespread and of great ecological and economic importance. In terms of areas impacted, tropical storms have the most widespread effects on tropical and temperate forests, with southeastern U.S. forests particularly prone to tropical storm damage. This impact motivates attempts to understand the tree and forest characteristics that influence levels of damage. This study presents initial findings from a spatially explicit, individual-based mechanistic wind severity model, ForSTORM, parameterized from winching research on trees in southeastern U.S. This model allows independent control of six wind and neighborhood parameters likely to influence the patterns of wind damage, such as gap formation, the shape of the vertical wind profile, indirect damage, and support from neighbors. We arranged the subject trees in two virtual stands orientations with identical positions relative to each other, but with one virtual stand rotated 90 degrees from the other virtual stand – to explore the effect of wind coming from two alternative directions. The model reproduces several trends observed in field damage surveys, as well as analogous CWS models developed for other forests, and reveals unexpected insights. Wind profiles with higher extinction coefficients, or steeper decrease in wind speed from canopy top to lower levels, resulted in significantly higher critical wind speeds, thus reducing level of damage for a given wind speed. Three alternative formulations of wind profiles also led to significant differences in critical wind speed (CWS), although the effect of profile was less than effect of different extinction coefficients. The CWS differed little between the two alternative stand orientations. Support from neighboring trees resulted in significantly higher critical wind speeds, regardless of type of wind profile or spatial arrangement of trees. The presence or absence of gaps caused marginally significant different in CWS, while inclusion of indirect damage along with direct damage did not significantly change CWS from those caused by direct damage alone. Empirical research that could most benefit this modelling approach includes improving crown area measurement, refining drag coefficients, and development of a biomechanical framework for neighbor support.

Kinematika Sendi Lengan Penari Bapang Malangan


 
 
 
 Dancers experience various injuries, because dancing requires high intensity movements. Frequent injuries to dancers involve overuse of joints and muscles. The highest potential for injury is in the knee. However, in the Bapang Malangan Dance, the arms are the limbs that are often used in extreme movements. Thus the potential for injury can be high. This study focuses on the kinematics of arm movement of the Bapang Malangan Dance in relation to the possibility of injury. The research was carried out through analyzing image data resulting from the rendering of dance video footage, following a kinematics-based biomechanical framework and engineering dynamics. The results showed that the kinematic analysis of the Bapang dancer's arm was depicted only on the change in position because velocity and velocity could not be measured directly. Changes in the position of the Bapang dancer's arms can be depicted in graphic form through frame analysis of the transformed video files into image files. The arm joints that get a lot of weight are the shoulder and elbow joints, which in Bapang Malangan dancers have the potential to experience injury due to tugging and twisting. The complexities of movements and changes in dancer movements turn out to make it difficult to determine the speed and acceleration by analyzing the rendered images. A measuring instrument is needed that can directly measure arm movements when dancing. This tool must not use cables so as not to obstruct the dance movement.
 
 
 
 
 
 Keywords: biomechanic, kinematic, arm joint, dancer, Bapang Malangan
 
 
 

Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment.

PurposeTo provide a biomechanical framework to better understand the postsurgical optomechanical behavior of the cornea after ring implantation.MethodsCalibrated in silico models were used to determine the corneal shape and stresses after ring implantation. After mechanical simulations, geometric ray-tracing was used to determine the change in spherical equivalent. The effect of the surgical procedure, circadian variation of intraocular pressure, or the biomechanical weakening introduced by keratoconus (KC) were evaluated for each intrastromal ring.ResultsModels predicted the postsurgical optomechanical response of the cornea at a population level. The localized mechanical effect of the additional intrastromal volume introduced by the implants (size and diameter) drives the postsurgical corneal response. However, central corneal stresses did not increase more than 50%, and thus implants did not strengthen the cornea globally. Because of the biomechanical weakening introduced by laser pocketing, continuous implants in a pocket resulted in higher refractive corrections and in the relaxation of the anterior stroma, which could slow down KC progression. Implants can move within the stroma, acting as a dynamic pivot point that modifies corneal kinematics and flattens the corneal center. Changes in stromal mechanical properties did not impact on refraction for normal or pathological corneas.ConclusionsImplants do not stiffen the cornea but create a local bulkening effect that regularizes the corneal shape by modifying corneal kinematics without canceling corneal motion.Translational RelevanceIn silico models can help to understand corneal biomechanics, to plan patient-specific interventions, or to create biomechanically driven nomograms.

Interdisciplinary methodological framework of biomechanics and occupational psychology for MSD prevention

In both France and abroad, musculoskeletal disorders (MSD) remain the most widespread occupational diseases. The scientific literature has established that links exist between the occurrence of MSD and the professional gesture. The aim of this paper is to show how biomechanical analysis helps to create intervention tools implemented in a methodological framework in clinical activity with a view to preventing MSD through analysis of the gesture. The aim of this paper is to analyse how an intervention was conducted within the general methodological framework of occupational psychology using activity-clinic research based on professional gesture analysis and it also benefited from interdisciplinary co-operation with biomechanics. The interdisciplinary methodology employed in relation to eight gravediggers consisted of different steps that included a detailed analysis of the muscular activity of the shoulder and back muscles. The results show that the interdisciplinary methodology makes it possible to widen the potential development zone of the gesture in the gravediggers’ activity by stimulating their professional discussions. The creation of visibility and discussion in the profession of inter- and intra-individual variability has opened up the professional world to new forms of action to prevent MSD.

An efficient and accurate method for modeling nonlinear fractional viscoelastic biomaterials

Computational biomechanics plays an important role in biomedical engineering: using modeling to understand pathophysiology, treatment and device design. While experimental evidence indicates that the mechanical response of most tissues is viscoelastic, current biomechanical models in the computational community often assume hyperelastic material models. Fractional viscoelastic constitutive models have been successfully used in literature to capture viscoelastic material response; however, the translation of these models into computational platforms remains limited. Many experimentally derived viscoelastic constitutive models are not suitable for three-dimensional simulations. Furthermore, the use of fractional derivatives can be computationally prohibitive, with a number of current numerical approximations having a computational cost that is O(NT2) and a storage cost that is O(NT) (NT denotes the number of time steps). In this paper, we present a novel numerical approximation to the Caputo derivative which exploits a recurrence relation similar to those used to discretize classic temporal derivatives, giving a computational cost that is O(NT) and a storage cost that is fixed over time. The approximation is optimized for numerical applications, and an error estimate is presented to demonstrate the efficacy of the method. The method, integrated into a finite element solid mechanics framework, is shown to be unconditionally stable in the linear viscoelastic case. It was then integrated into a computational biomechanical framework, with several numerical examples verifying the accuracy and computational efficiency of the method, including in an analytic test, in an analytic fractional differential equation, as well as in a computational biomechanical model problem.

Labour and delivery: a clinician's perspective on a biomechanics problem.

Predicting how and when a pregnant woman will deliver her fetus has always been a problem for the clinician, and, consequently, there has been little progress made in preventing poor outcomes from pregnancies that deliver too soon or too late. In the opinion of the author, a maternal-fetal medicine specialist, rethinking labour within a biomechanical framework and studying it like an engineering problem could be a promising approach to unlocking the mysteries of labour.

Cuff tear arthropathy in the nineteenth century: 'chronic rheumatic arthritis' with 'partial luxation upwards' of the humeral head.

Cuff tear arthropathy of the shoulder is a common indication for insertion of an increasing number of reverse shoulder arthroplasties. It is widely believed that this condition was unknown to medical practitioners and writers prior to the introduction of the term cuff tear arthropathy by Charles Neer in 1977. To search nineteenth-century written sources for pathoanatomical and biomechanical descriptions of the typical changes found in cuff tear arthropathy. A historical review. Nineteenth-century medical textbooks, reviews, case series, autopsy reports and illustrations were systematically searched and retrieved for relevance. References were hand-searched. Illustrations were reproduced and interpreted. A richly illustrated nineteenth-century literature was identified. The typical changes in cuff tear arthropathy were termed 'chronic rheumatic arthritis' of the shoulder with 'partial luxation upwards' of the humeral head and interpreted within a pathoanatomical and biomechanical framework. Detailed descriptions and illustrations of massive rotator cuff tears, biceps pathology and the osseous changes were identified and presented. The pathoanatomical and biomechanical changes later termed cuff tear arthropathy were well understood and nicely described in nineteenth-century medical literature.

A computational framework to investigate retinal haemodynamics and tissue stress

The process of vision begins in the retina, yet the role of biomechanical forces in the retina is relatively unknown and only recently being explored. This contribution describes a computational framework involving 3D fluid-structure interaction simulations derived from fundus images that work towards creating unique data on retinal biomechanics. We developed methods to convert 2D fundus photographs into 3D geometries that follow the curvature of the retina. Retina arterioles are embedded into a six-layer representation of the retinal tissue with varying material properties throughout the retinal tissue. Using three different human retinas (healthy, glaucoma, diabetic retinopathy) and by varying our simulation approaches, we report the effects of transient versus steady flow, viscosity assumptions (Newtonian, non-Newtonian and Fåhræus-Lindqvist effect) and rigid versus compliant retinal tissue, on resulting wall shear stress (WSS) and von Mises stress. In the retinal arterioles, the choice of viscosity model is important and WSS obtained from models with the Fåhræus-Lindqvist effect is markedly different from Newtonian and non-Newtonian models. We found little difference in WSS between steady-state and pulsatile simulations (< 5%) and show that WSS varies by about 7% between rigid and deformable models. Comparing the three geometries, we found notably different WSS in the healthy (3.3 ± 1.3Pa), glaucoma (5.7 ± 1.6Pa) and diabetic retinopathy cases (4.3 ± 1.1Pa). Conversely, von Mises stress was similar in each case. We have reported a novel biomechanical framework to explore the stresses in the retina. Despite current limitations and lack of complete subject-specific physiological inputs, we believe our framework is the first of its kind and with further improvements could be useful to better understand the biomechanics of the retina.

Chitosan-Based Hydrogels Embedded with Hyaluronic Acid Complex Nanoparticles for Controlled Delivery of Bone Morphogenetic Protein-2.

Chitosan(CH)-poly(dioxanone) (CH-PDO) copolymers containing varied amounts of PDO and having free amino groups at their CH backbone were synthesized using a group protection method. The selected CH-PDO with soluble characteristics in aqueous media was used together with hyaluronic acid (HA) to prepare HA/CH-PDO polyelectrolyte complex nanoparticles (NPs) via an ionotropic gelation technique, and such a type of HA/CH-PDO NPs was employed as a carrier for delivering bone morphogenetic protein-2 (BMP-2). The optimal BMP-2-encapsulated HA/CH-PDO NPs with high encapsulation efficiency were embedded into CH/glycerophosphate composite solutions to form different hydrogels in order to achieve long-term BMP-2 release. The formulated gels were found to be injectable at room temperature and had its thermosensitive phase transition near physiological temperature and pH. They also showed abilities to administer the release of BMP-2 in approximately linear manners for a few weeks while effectively preserving the bioactivity of the encapsulated BMP-2. In view of their fully biocompatible and biodegradable components, the presently developed gel systems have promising potential for translation to the clinic use in bone repair and regeneration where the sustained and controlled stimuli from active signaling molecules and the stable biomechanical framework for housing the recruited cells are often concurrently needed.

A subject-specific integrative biomechanical framework of the pelvis for gait analysis.

Analysis of the human locomotor system using rigid-body musculoskeletal models has increased in the biomechanical community with the objective of studying muscle activations of different movements. Simultaneously, the finite element method has emerged as a complementary approach for analyzing the mechanical behavior of tissues. This study presents an integrative biomechanical framework for gait analysis by linking a musculoskeletal model and a subject-specific finite element model of the pelvis. To investigate its performance, a convergence study was performed and its sensitivity to the use of non-subject-specific material properties was studied. The total hip joint force estimated by the rigid musculoskeletal model and by the finite element model showed good agreement, suggesting that the integrative approach estimates adequately (in shape and magnitude) the hip total contact force. Previous studies found movements of up to 1.4 mm in the anterior-posterior direction, for single leg stance. These results are comparable with the displacement values found in this study: 0-0.5 mm in the sagittal axis. Maximum von Mises stress values of approximately 17 MPa were found in the pelvic bone. Comparing this results with a previous study of our group, the new findings show that the introduction of muscular boundary conditions and the flexion-extension movement of the hip reduce the regions of high stress and distributes more uniformly the stress across the pelvic bone. Thus, it is thought that muscle force has a relevant impact in reducing stresses in pelvic bone during walking of the finite element model proposed in this study. Future work will focus on including other deformable structures, such as the femur and the tibia, and subject-specific material properties.

Chemical imaging of fresh vascular smooth muscle cell response by epi-detected stimulated Raman scattering.

An understanding of deformation of cardiovascular tissue under hemodynamic load is crucial for understanding the health and disease of blood vessels. In the present work, an epi-detected stimulated Raman scattering (epi-SRS) imaging platform was designed for in situ functional imaging of vascular smooth muscle cells (VMSCs) in fresh coronary arteries. For the first time, the pressure-induced morphological deformation of fresh VSMCs was imaged with no fixation and in a label-free manner. The relation between the loading pressure and the morphological parameters, including angle and length of the VSMCs, were apparent. The morphological responses of VMSCs to drug treatment were also explored, to demonstrate the capability of functional imaging for VSMCs by this method. The time-course imaging revealed the drug induced change in angle and length of VSMCs. The present study provides a better understanding of the biomechanical framework of blood vessels, as well as their responses to external stimulations, which are fundamental for developing new strategies for cardiovascular disease treatment.

A biomechanical approach to understand the ecomorphological relationship between primate mandibles and diet

The relationship between primate mandibular form and diet has been previously analysed by applying a wide array of techniques and approaches. Nonetheless, most of these studies compared few species and/or infrequently aimed to elucidate function based on an explicit biomechanical framework. In this study, we generated and analysed 31 Finite Element planar models of different primate jaws under different loading scenarios (incisive, canine, premolar and molar bites) to test the hypothesis that there are significant differences in mandibular biomechanical performance due to food categories and/or food hardness. The obtained stress values show that in primates, hard food eaters have stiffer mandibles when compared to those that rely on softer diets. In addition, we find that folivores species have the weakest jaws, whilst omnivores have the strongest mandibles within the order Primates. These results are highly relevant because they show that there is a strong association between mandibular biomechanical performance, mandibular form, food hardness and diet categories and that these associations can be studied using biomechanical techniques rather than focusing solely on morphology.

Anatomical and biomechanical framework for shoulder arthroplasty rehabilitation

This article provides an anatomical and biomechanical framework for the postoperative management and progression of treatment for shoulder arthroplasty. The clinical relevance of normal shoulder anatomy, biomechanics, and pathomechanics related to this surgery is emphasized to provide the reader with an understanding of the rationale for treatment. We review the rehabilitation implications of surgical indications and technique for both traditional total shoulder arthroplasty and reverse total shoulder arthroplasty procedures with an emphasis on biomechanical considerations. Relevant factors that affect rehabilitation outcomes are discussed along with supporting evidence from the literature. Principles to guide and progress treatment are highlighted with a discussion on return to sports with the ultimate objective of providing a comprehensive approach for successful rehabilitation.

Improved identifiability of myocardial material parameters by an energy-based cost function

Myocardial stiffness is a valuable clinical biomarker for the monitoring and stratification of heart failure (HF). Cardiac finite element models provide a biomechanical framework for the assessment of stiffness through the determination of the myocardial constitutive model parameters. The reported parameter intercorrelations in popular constitutive relations, however, obstruct the unique estimation of material parameters and limit the reliable translation of this stiffness metric to clinical practice. Focusing on the role of the cost function (CF) in parameter identifiability, we investigate the performance of a set of geometric indices (based on displacements, strains, cavity volume, wall thickness and apicobasal dimension of the ventricle) and a novel CF derived from energy conservation. Our results, with a commonly used transversely isotropic material model (proposed by Guccione et al.), demonstrate that a single geometry-based CF is unable to uniquely constrain the parameter space. The energy-based CF, conversely, isolates one of the parameters and in conjunction with one of the geometric metrics provides a unique estimation of the parameter set. This gives rise to a new methodology for estimating myocardial material parameters based on the combination of deformation and energetics analysis. The accuracy of the pipeline is demonstrated in silico, and its robustness in vivo, in a total of 8 clinical data sets (7 HF and one control). The mean identified parameters of the Guccione material law were C_1=3000pm 1700,hbox {Pa} and alpha =45pm 25 (b_f=25pm 14, b_{ft}=11pm 6, b_{t}=9pm 5) for the HF cases and C_1=1700,hbox {Pa} and alpha =15 (b_f=8, b_{ft}=4, b_{t}=3) for the healthy case.