Quantification of gravity-induced skin strain across the breast surface

Background Quantification of the magnitude of skin strain in different regions of the breast may help to estimate possible gravity-induced damage whilst also being able to inform the selection of incision locations during breast surgery. The aim of this study was to quantify static skin strain over the breast surface and to estimate the risk of skin damage caused by gravitational loading. Methods Fourteen participants had 21 markers applied to their torso and left breast. The non-gravity breast position was estimated as the mid-point of the breast positions in water and soybean oil (higher and lower density than breast respectively). The static gravity-loaded breast position was also measured. Skin strain was calculated as the percentage extension between adjacent breast markers in the gravity and non-gravity loaded conditions. Findings Gravity induced breast deformation caused peak strains ranging from 14 to 75% across participants, with potentially damaging skin strain (>60%) in one participant and skin strains above 30% (skin resistance zone) in a further four participants. These peak strain values all occurred in the longitudinal direction in the upper region of the breast skin. In the latitudinal direction, smaller-breasted participants experienced greater strain on the outer (lateral) breast regions and less strain on the inner (medial) breast regions, a trend which was reversed in the larger breasted participants (above size 34D). Interpretation To reduce tension on surgical incisions it is suggested that preference should be given to medial latitudinal locations for smaller breasted women and lateral latitudinal locations for larger breasted women

Methodological and anatomical modifiers of Achilles tendon moment arm estimates implications for biomechanical modelling: Implications for biomechanical modelling

This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.Moment arms are important in many contexts. Various methods have been used to estimate moment arms. It has been shown that a moment arm changes as a function of joint angle and contraction state. However, besides the influence of these anatomical factors, results from recent studies suggest that the estimation of moment arm is also dependent on the methods employed. The overall goal of this thesis was to explore the interaction between the methodological and anatomical influences on moment arm and their effect on estimates of muscle-tendon forces during biomechanical modelling. The first experiment was a direct comparison between two different moment arm methods that have been previously used for the estimation of Achilles tendon moment arm. The results of this experiment revealed a significant difference in Achilles tendon moment arm length dependent on the moment arm method employed. However, besides the differences found, results from both methods were well correlated. Based on these results, methodological differences between these two methods were compared across different joint angles and contraction states in study two. Results of experiment two revealed that Achilles tendon moment arms obtained using both methods change in a similar way as a function of joint angle and contraction state. In the third experiment, results from the first two experiments were used to determine how methodological and anatomical influences on Achilles tendon moment arm would change muscle-tendon forces during the task of submaximal cycling. Results of the third experiment showed the importance of taking the method, ankle angle and contraction state dependence of Achilles tendon moment arm into account when using biomechanical modelling techniques. Together, these findings emphasis the importance of carefully considering methodological and anatomical modifiers when estimating Achilles tendon moment arm

3D computerized model for measuring strain and displacement of the brachial plexus following placement of reverse shoulder prosthesis

The aim of the present study was to develop a method for three-dimensional (3D) reconstruction of the brachial plexus to study its morphology and to calculate strain and displacement in relation to changed nerve position. The brachial plexus was finely dissected and injected with contrast medium and leaden markers were implanted into the nerves at predefined places. A reverse shoulder prosthesis was inserted in a cadaveric specimen what induced positional change in the upper limb nerves. Computed tomography (CT) was performed before and after this surgical intervention. The computer assisted image processing package Mimics (R) was used to reconstruct the pre- and postoperative brachial plexus in 3D. The results show that the current interactive model is a realistic and detailed representation of the specimen used, which allows 3D study of the brachial plexus in different configurations. The model estimated strains up to 15.3% and 19.3% for the lateral and the medial root of the median nerve as a consequence of placing a reverse shoulder prosthesis. Furthermore, the model succeeded in calculating the displacement of the brachial plexus by tracking each implanted lead marker. The presented brachial plexus 3D model currently can be used in vitro for cadaver biomechanical analyses of nerve movement to improve diagnosis and treatment of peripheral neuropathies. The model can also be applied to study the exact location of the plexus in unusual upper limb positions like during axillary radiation therapy and it is a potential tool to optimize the approaches of brachial plexus anesthetic blocks

A quantitative evaluation of physical and digital approaches to centre of mass estimation

Centre of mass is a fundamental anatomical and biomechanical parameter. Knowledge of centre of mass is essential to inform studies investigating locomotion and other behaviours, through its implications for segment movements, and on whole body factors such as posture. Previous studies have estimated centre of mass position for a range of organisms, using various methodologies. However, few studies assess the accuracy of the methods that they employ, and often provide only brief details on their methodologies. As such, no rigorous, detailed comparisons of accuracy and repeatability within and between methods currently exist. This paper therefore seeks to apply three methods common in the literature (suspension, scales and digital modelling) to three 'calibration objects' in the form of bricks, as well as three birds to determine centre of mass position. Application to bricks enables conclusions to be drawn on the absolute accuracy of each method, in addition to comparing these results to assess the relative value of these methodologies. Application to birds provided insights into the logistical challenges of applying these methods to biological specimens. For bricks, we found that, provided appropriate repeats were conducted, the scales method yielded the most accurate predictions of centre of mass (within 1.49 mm), closely followed by digital modelling (within 2.39 mm), with results from suspension being the most distant (within 38.5 mm). Scales and digital methods both also displayed low variability between centre of mass estimates, suggesting they can accurately and consistently predict centre of mass position. Our suspension method resulted not only in high margins of error, but also substantial variability, highlighting problems with this method

Book of Abstracts 15th International Symposium on Computer Methods in Biomechanics and Biomedical Engineering and 3rd Conference on Imaging and Visualization

In this edition, the two events will run together as a single conference, highlighting the strong connection with the Taylor & Francis journals: Computer Methods in Biomechanics and Biomedical Engineering (John Middleton and Christopher Jacobs, Eds.) and Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualization (JoãoManuel R.S. Tavares, Ed.). The conference has become a major international meeting on computational biomechanics, imaging andvisualization. In this edition, the main program includes 212 presentations. In addition, sixteen renowned researchers will give plenary keynotes, addressing current challenges in computational biomechanics and biomedical imaging. In Lisbon, for the first time, a session dedicated to award the winner of the Best Paper in CMBBE Journal will take place. We believe that CMBBE2018 will have a strong impact on the development of computational biomechanics and biomedical imaging and visualization, identifying emerging areas of research and promoting the collaboration and networking between participants. This impact is evidenced through the well-known research groups, commercial companies and scientific organizations, who continue to support and sponsor the CMBBE meeting series. In fact, the conference is enriched with five workshops on specific scientific topics and commercial software.info:eu-repo/semantics/draf

Mechanical factors affecting the estimation of tibialis anterior force using an EMG-driven modelling approach

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityThe tibialis anterior (TA) muscle plays a vital role in human movement such as walking and running. Overuse of TA during these movements leads to an increased susceptibility of injuries e.g. chronic exertional compartment syndrome. TA activation has been shown to be affected by increases in exercise, age, and the external environment (i.e. incline and footwear). Because activation parameters of TA change with condition, it leads to the interpretation that force changes occur too. However,activation is only an approximate indicator of force output of a muscle. Therefore, the overall aim of this thesis was to investigate the parameters affecting accurate measure of TA force, leading to development of a subject-specific EMG-driven model, which takes into consideration specific methodological issues. The first study investigated the reasons why the tendon excursion and geometric method differ so vastly in terms of estimation of TA moment arm. Tendon length changes during the tendon excursion method, and location of the TA line of action and irregularities between talus and foot rotations during the geometric method, were found to affect the accuracy of TA moment arm measurement. A novel, more valid, method was proposed. The second study investigated the errors associated with methods used to account for plantar flexor antagonist co-contraction. A new approach was presented and shown to be, at worse, equivalent to current methods, but allows for accounting throughout the complete range of motion. The final study utilised the outputs from studies one and two to directly measure TA force in vivo. This was used to develop, and validate, an EMG-driven TA force model. Less error was found in the accuracy of estimating TA force when the contractile component length changes were modelled using the ankle, as opposed to the muscle. Overall, these findings increase our understanding of not only the mechanics associated with TA and the ankle, but also improves our ability to accurately monitor these.Headley Court Trust and the Defence Medical Rehabilitation Centre

Mechanical factors affecting the estimation of tibialis anterior force using an EMG-driven modelling approach

The tibialis anterior (TA) muscle plays a vital role in human movement such as walking and running. Overuse of TA during these movements leads to an increased susceptibility of injuries e.g. chronic exertional compartment syndrome. TA activation has been shown to be affected by increases in exercise, age, and the external environment (i.e. incline and footwear). Because activation parameters of TA change with condition, it leads to the interpretation that force changes occur too. However,activation is only an approximate indicator of force output of a muscle. Therefore, the overall aim of this thesis was to investigate the parameters affecting accurate measure of TA force, leading to development of a subject-specific EMG-driven model, which takes into consideration specific methodological issues. The first study investigated the reasons why the tendon excursion and geometric method differ so vastly in terms of estimation of TA moment arm. Tendon length changes during the tendon excursion method, and location of the TA line of action and irregularities between talus and foot rotations during the geometric method, were found to affect the accuracy of TA moment arm measurement. A novel, more valid, method was proposed. The second study investigated the errors associated with methods used to account for plantar flexor antagonist co-contraction. A new approach was presented and shown to be, at worse, equivalent to current methods, but allows for accounting throughout the complete range of motion. The final study utilised the outputs from studies one and two to directly measure TA force in vivo. This was used to develop, and validate, an EMG-driven TA force model. Less error was found in the accuracy of estimating TA force when the contractile component length changes were modelled using the ankle, as opposed to the muscle. Overall, these findings increase our understanding of not only the mechanics associated with TA and the ankle, but also improves our ability to accurately monitor these

Structural Origins of the Stiffness and Work Contributions of the Human Foot

Human foot mechanics have been extensively studied over the last century to understand human evolution and treat foot pathologies.Much of this understanding has centered on the foot\u27s longitudinal arch that runs from heel to toe, especially its role in making human feet stiff enough to withstand many times our bodyweight during walking and running. But numerous studies on foot biomechanics, orthopedic surgical reconstructions, and human evolution point to substantial gaps in the understanding based on the longitudinal arch alone. In this thesis, I present two new findings related to foot stiffness and how it produces the mechanical power needed for propulsion. First, I show that the transverse arch that runs across its width contributes more to foot stiffness than the longitudinal arch. Second, I show that a mechanism involving the plantar fascia and the longitudinal arch, called the windlass mechanism, has no effect on stiffness as previously assumed. Instead, it helps transmit power from muscles outside the foot to locations within the foot for efficient walking. These findings hinge upon a combination of mathematical models, mechanical foot models, mechanical tests on cadaveric feet, and measurements on live walking and running human volunteers. Together, these studies show how the foot\u27s function emerges from the combined roles of the longitudinal and transverse arches, and how those features may have evolved to enable human walking and running. After an introduction in chapter 1 to the current understanding of foot biomechanics and evolution, chapter 2 will present a series of studies using mechanical foot mimics and three-point bending tests in cadaveric human feet to show how the curvature of the transverse arch contributes to sagittal plane stiffness.Chapter 3 extends this result to in vivo foot stiffness measurements in walking humans and shows that despite active muscle contraction changes during walking, the transverse arch continues to influence sagittal foot stiffness. The evidence indicates that the evolution of a transverse arch played a key role in human evolution by enabling a stiff foot for propulsion. Chapter 4 turns to the longitudinal arch with an experimental examination of the windlass mechanism in walking and running humans, and finds that the windlass does not increase foot stiffness but plays an important role in power transmission so that the foot can output mechanical power without the need for heavy muscles within the foot itself. This thesis advances the understanding of structure-function relationships in the human foot and impacts the fields of evolutionary biology, podiatry and robotics. The renewed understanding of the windlass mechanism, taken together with other studies that compare feet across many primate species, suggests that the power transmission function of the windlass is important for walking, and could have emerged well before the longitudinal arch evolved in humans. Future clinical studies have to consider the transverse arch in evaluating foot function and may find that to be a potential target for the design of foot reconstructive surgeries, design of orthotic implants, and evaluation and classification of flatfoot disorders. Finally, the mechanical foot mimics that were developed may inspire the design of lightweight robotic and prosthetic feet with tunable stiffness properties that exploit the curvature induced stiffening of the human foot

Mechanical Behaviour of Tendinopathic Tendon: An Engineering Perspective

Tendinopathy is a debilitating disease affecting millions of people worldwide. The aetiology of this disease is not well understood, and treatment remains difficult due to a lack of evidence-based management. This dissertation sought to quantify the mechanical behaviour of tendon in order to understand the difference between healthy and tendinopathic tendons. The findings in this dissertation offer insights that may contribute toward the development of better clinical management of tendinopathy