Publications
287 results found
Czasche MB, Goodwin JE, Bull AMJ, et al., 2018, Effects of an 8-week strength training intervention on tibiofemoral joint loading during landing: a cohort study., BMJ Open Sport and Exercise Medicine, Vol: 4, ISSN: 2055-7647
Objectives: To use a musculoskeletal model of the lower limb to evaluate the effect of a strength training intervention on the muscle and joint contact forces experienced by untrained women during landing. Methods: Sixteen untrained women between 18 and 28 years participated in this cohort study, split equally between intervention and control groups. The intervention group trained for 8 weeks targeting improvements in posterior leg strength. The mechanics of bilateral and unilateral drop landings from a 30 cm platform were recorded preintervention and postintervention, as was the isometric strength of the lower limb during a hip extension test. The internal muscle and joint contact forces were calculated using FreeBody, a musculoskeletal model. Results: The strength of the intervention group increased by an average of 35% (P<0.05; pre: 133±36 n, post: 180±39 n), whereas the control group showed no change (pre: 152±36 n, post: 157±46 n). There were only small changes from pre-test to post-test in the kinematics and ground reaction forces during landing that were not statistically significant. Both groups exhibited a post-test increase in gluteal muscle force during landing and a lateral to medial shift in tibiofemoral joint loading in both landings. However, the magnitude of the increase in gluteal force and lateral to medial shift was significantly greater in the intervention group. Conclusion: Strength training can promote a lateral to medial shift in tibiofemoral force (mediated by an increase in gluteal force) that is consistent with a reduction in valgus loading. This in turn could help prevent injuries that are due to abnormal knee loading such as anterior cruciate ligament ruptures, patellar dislocation and patellofemoral pain.
Azmi NL, Ding Z, Xu R, et al., 2018, Activation of biceps femoris long head reduces tibiofemoral anterior shear force and tibial internal rotation torque in healthy subjects, PLoS ONE, Vol: 13, ISSN: 1932-6203
The anterior cruciate ligament (ACL) provides resistance to tibial internal rotation torque and anterior shear at the knee. ACL deficiency results in knee instability. Optimisation of muscle contraction through functional electrical stimulation (FES) offers the prospect of mitigating the destabilising effects of ACL deficiency. The hypothesis of this study is that activation of the biceps femoris long head (BFLH) reduces the tibial internal rotation torque and the anterior shear force at the knee. Gait data of twelve healthy subjects were measured with and without the application of FES and taken as inputs to a computational musculoskeletal model. The model was used to investigate the optimum levels of BFLH activation during FES gait in reducing the anterior shear force to zero. This study found that FES significantly reduced the tibial internal rotation torque at the knee during the stance phase of gait (p = 0.0322) and the computational musculoskeletal modelling revealed that a mean BFLH activation of 20.8% (±8.4%) could reduce the anterior shear force to zero. At the time frame when the anterior shear force was zero, the internal rotation torque was reduced by 0.023 ± 0.0167 Nm/BW, with a mean 188% reduction across subjects (p = 0.0002). In conclusion, activation of the BFLH is able to reduce the tibial internal rotation torque and the anterior shear force at the knee in healthy control subjects. This should be tested on ACL deficient subject to consider its effect in mitigating instability due to ligament deficiency. In future clinical practice, activating the BFLH may be used to protect ACL reconstructions during post-operative rehabilitation, assist with residual instabilities post reconstruction, and reduce the need for ACL reconstruction surgery in some cases.
Klemt C, Nolte D, Grigoriadis G, et al., 2017, The contribution of the glenoid labrum to glenohumeral stability under physiological joint loading using finite element analysis, Computer Methods in Biomechanics and Biomedical Engineering, Vol: 20, Pages: 1613-1622, ISSN: 1025-5842
Pearce AP, Bull AMJ, Clasper JC, 2017, Re: Mediastinal injury is the strongest predictor of mortality in mounted blast amongst UK deployed forces: Methodological issues, Injury: International Journal of the Care of the Injured, Vol: 48, Pages: 2610-2610, ISSN: 0020-1383
Bull AMJ, Pandis P, 2017, A low cost 3D laser surface scanning approach for defining body segment parameters, Proceedings of the Institution of Mechanical Engineers Part H - Journal of Engineering in Medicine, Vol: 231, Pages: 1064-1068, ISSN: 0954-4119
Body segment parameters are used in many different applications in ergonomics as well as in dynamic modelling of the musculoskeletal system. Body segment parameters can be defined using different methods, including techniques that involve time-consuming manual measurements of the human body, used in conjunction with models or equations. In this study, a scanning technique for measuring subject-specific body segment parameters in an easy, fast, accurate and low-cost way was developed and validated. The scanner can obtain the body segment parameters in a single scanning operation, which takes between 8 and 10 s. The results obtained with the system show a standard deviation of 2.5% in volumetric measurements of the upper limb of a mannequin and 3.1% difference between scanning volume and actual volume. Finally, the maximum mean error for the moment of inertia by scanning a standard-sized homogeneous object was 2.2%. This study shows that a low-cost system can provide quick and accurate subject-specific body segment parameter estimates.
Junaid S, Sanghavi S, Anglin C, et al., 2017, Treatment of the Fixation Surface Improves Glenoid Prosthesis Longevity in vitro., Journal of Biomechanics, Vol: 61, Pages: 81-87, ISSN: 0021-9290
Many commercial cemented glenoid components claim superior fixation designs and increased survivability. However, both research and clinical studies have shown conflicting results and it is unclear whether these design variations do improve loosening rates. Part of the difficulty in investigating fixation failure is the inability to directly observe the fixation interface, a problem addressed in this study by using a novel experimental set-up. Cyclic loading-displacement tests were carried out on 60 custom-made glenoid prostheses implanted into a bone substitute. Design parameters investigated included treatment of the fixation surface of the component resulting in different levels of back-surface roughness, flat-back versus curved-back, keel versus peg and more versus less conforming implants. Visually-observed failure and ASTM-recommended rim-displacements were recorded throughout testing to investigate fixation failure and if rim displacement is an appropriate measure of loosening. Roughening the implant back (Ra>3µm) improved resistance to failure (P<0.005) by an order of magnitude with the rough and smooth groups failing at 8712±5584 cycles (mean±SD) and 1080±1197 cycles, respectively. All other design parameters had no statistically significant effect on the number of cycles to failure. All implants failed inferiorly and 95% (57/60) at the implant/cement interface. Rim-displacement correlated with visually observed failure. The most important effect was that of roughening the implant, which strengthened the polyethylene-cement interface. Rim-displacement can be used as an indicator of fixation failure, but the sensitivity was insufficient to capture subtle effects. LEVEL OF EVIDENCE: Basic Science Study, Biomechanical Analysis.
Pearce AP, Bull AMJ, Clasper JC, 2017, Mediastinal injury is the strongest predictor of mortality in mounted blast amongst UK deployed forces., Injury, Vol: 48, Pages: 1900-1905, ISSN: 0020-1383
BACKGROUND: Blast injury has been the most common cause of morbidity and mortality encountered by UK forces during recent conflicts. Injuries sustained by blast are categorised by the injuring component of the explosion and depend upon physical surroundings. Previous work has established that head injuries and intra cavity haemorrhage are the major causes of death following exposure to under body (mounted) blast but has yet to explore the precise nature of these torso injuries nor the effect of particular injuries upon survival. This study examines the patterns of torso injury within the mounted blast environment in order to understand the effect of these injuries upon survivability. METHODS: This retrospective study examined the UK Joint Theatre Trauma Registry to determine precise injury patterns of mounted blast casualties within a 13year period of UK military deployments. Survival rates of individual injuries were compared and a multivariable logistic regression model was developed in order to assess the effect that each injury had upon likelihood of death. RESULTS: 426 mounted casualties were reviewed of whom 129 did not survive. Median NISS and ISS for non-survivors was found to be 75. Torso injuries were significantly more common amongst non-survivors than survivors and high case fatality rates were associated with all haemorrhagic torso injuries. Multivariable analysis shows that mediastinal injuries have the largest odds ratio for mortality (20.4) followed by lung laceration and head injury. CONCLUSIONS: Non-compressible torso haemorrhage is associated with mortality amongst mounted blast. Of this group, mediastinal injury is the strongest predictor of death and could be considered as a surrogate marker of lethality. Future work to link blast loading characteristics with specific injury patterns will inform the design of mitigating strategies in order to improve survivability of underbody blast.
Panagiotakis E, Mok K-M, Fong DT-P, et al., 2017, Biomechanical analysis of ankle ligamentous sprain injury cases from televised basketball games: Understanding when, how and why ligament failure occurs, Journal of Science and Medicine in Sport, Vol: 20, Pages: 1057-1061, ISSN: 1440-2440
OBJECTIVES: Ankle sprains due to landing on an opponent's foot are common in basketball. There is no analysis to date that provides a quantification of this injury mechanism. The aim of this study was to quantify the kinematics of this specific injury mechanism and relate this to lateral ankle ligament biomechanics. DESIGN: Case series. METHODS: The model-based image-matching technique was used to quantify calcaneo-fibular-talar kinematics during four ankle inversion sprain injury incidents in televised NBA basketball games. The four incidents follow the same injury pattern in which the players of interest step onto an opponent's foot with significant inversion and a diagnosed ankle injury. A geometric analysis was performed to calculate the in vivo ligament strains and strain rates for the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL). RESULTS: Despite the controlled selection of cases, the results show that there are two distinct injury mechanisms: sudden inversion and internal rotation with low levels of plantarflexion; and a similar mechanism without internal rotation. The first of these mechanisms results in high ATFL and CFL strains, whereas the second of these strains the CFL in isolation. CONCLUSIONS: The injury mechanism combined with measures of the ligament injury in terms of percentage of strain to failure correlate directly with the severity of the injury quantified by return-to-sport. The opportunity to control excessive internal rotation through proprioceptive training and/or prophylactic footwear or bracing could be utilised to reduce the severity of common ankle injuries in basketball.
Ramasamy A, masouros S, grigoriadis, 2017, The lower extremities: Computational Modelling Attempts to Predict Injury, Military Injury Biomechanics The Cause and Prevention of Impact Injuries, Publisher: CRC Press, ISBN: 9781498742825
An international team of experts have been brought together to examine and review the topics. The book is intended for researchers, postgraduate students and others working or studying defence and impact injuries.
Fratini A, Bonci T, Bull AM, 2016, Whole body vibration treatments in postmenopausal women can improve bone mineral density: results of a stimulus focussed meta-analysis., PLOS One, Vol: 11, ISSN: 1932-6203
Whole body vibration treatment is a non-pharmacological intervention intended to stimulate muscular response and increase bone mineral density, particularly for postmenopausal women. The literature related to this topic is controversial, heterogeneous, and unclear despite the prospect of a major clinical effect.The aim of this study was to identify and systematically review the literature to assess the effect of whole body vibration treatments on bone mineral density (BMD) in postmenopausal women with a specific focus on the experimental factors that influence the stimulus. Nine studies fulfilled the inclusion criteria, including 527 postmenopausal women and different vibration delivery designs. Cumulative dose, amplitudes and frequency of treatments as well as subject posture during treatment vary widely among studies. Some of the studies included an associated exercise training regime. Both randomized and controlled clinical trials were included. Whole body vibration was shown to produce significant BMD improvements on the hip and spine when compared to no intervention. Conversely, treatment associated with exercise training resulted in negligible outcomes when compared to exercise training or to placebo. Moreover, side-alternating platforms were more effective in improving BMD values than synchronous platforms and mechanical oscillations of magnitude higher than 3 g and/or frequency lower than 25 Hz were also found to be effective. Treatments with a cumulative dose over 1000 minutes in the follow-up period were correlated to positive outcomes.Our conclusion is that whole body vibration treatments in elderly women can reduce BMD decline.However, many factors (e.g., amplitude, frequency and subject posture) affect the capacity of the vibrations to propagate to the target site; the adequate level of stimulation required to produce these effects has not yet been defined. Further biomechanical analyses to predict the propagation of the vibration waves along the body a
Rane L, Bull AMJ, 2016, Functional electrical stimulation of gluteus medius reduces the medial joint reaction force of the knee during level walking, Arthritis Research & Therapy, Vol: 18, ISSN: 1478-6354
Background: By altering muscular activation patterns, internal forces acting on the human body during dynamic activity may be manipulated. The magnitude of one of these forces, the medial knee joint reaction force (JRF), is associated with disease progression in patients with early osteoarthritis (OA), suggesting utility in its targeted reduction. Increased activation of gluteus medius has been suggested as a means to achieve this. Methods: Motion capture equipment and forceplate transducers were used to obtain kinematic and kinetic data for 15 healthy subjects during level walking, with and without the application of functional electrical stimulation (FES) to gluteus medius. Musculoskeletal modelling was employed to determine the medial knee JRF during stance phase for each trial. A further computer simulation of increased gluteus medius activation was performed using data from normal walking trials by a manipulation of modelling parameters. Relationships between changes in the medial knee JRF, kinematics and ground reaction force were evaluated. Results: In simulations of increased gluteus medius activity, the total impulse of the medial knee JRF was reduced by 4.2% (p=0.003) compared to control. With real-world application of FES to the muscle, the magnitude of this reduction increased to 12.5% (p<0.001), with significant inter-subject variation. Across subjects, the magnitude of reduction correlated strongly with kinematic (p<0.001) and kinetic (p<0.001) correlates of gluteus medius activity. Conclusions: The results support a major role for gluteus medius in the protection of the knee for patients with OA, establishing the muscle’s central importance to effective therapeutic regimes. FES may be used to achieve increased activation in order to mitigate distal internal loads, and much of the benefit of this increase can be attributed to resulting changes in kinematic parameters and the ground reaction force. The utility of interventions targeting g
Cheong VS, Karunaratne A, Amis AA, et al., 2016, Strain rate dependency of fractures of immature bone, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 66, Pages: 68-76, ISSN: 1751-6161
Radiological features alone do not allow the discrimination between accidental paediatric long bone fractures or those sustained by child abuse. Therefore, there is a clinical need to elucidate the mechanisms behind each fracture to provide a forensic biomechanical tool for the vulnerable child. Four-point bending and torsional loading tests were conducted at more than one strain rate for the first time on immature bone, using a specimen-specific alignment system, to characterise structural behaviour at para-physiological strain rates. The bones behaved linearly to the point of fracture in all cases and transverse, oblique, and spiral fracture patterns were consistently reproduced. The results showed that there was a significant difference in bending stiffness between transverse and oblique fractures in four-point bending. For torsional loading, spiral fractures were produced in all cases with a significant difference in the energy and obliquity to fracture. Multiple or comminuted fractures were seen only in bones that failed at a higher stress or torque for both loading types. This demonstrates the differentiation of fracture patterns at different strain rates for the first time for immature bones, which may be used to match the case history given of a child and the fracture produced.
Grigoriadis G, Carpanen D, Bull AMJ, et al., 2016, A finite element model of the foot and ankle for prediction of injury in under-body blast, International Research Council on the Biomechanics of Injury, Publisher: IRCOBI, Pages: 457-458, ISSN: 2235-3151
Nolte D, Tsang CK, Zhang KY, et al., 2016, Non-linear scaling of a musculoskeletal model of the lower limb using statistical shape models, Journal of Biomechanics, Vol: 49, Pages: 3576-3581, ISSN: 1873-2380
Accurate muscle geometry for musculoskeletal models is important to enable accurate subject-specific simulations. Commonly, linear scaling is used to obtain individualised muscle geometry. More advanced methods include non-linear scaling using segmented bone surfaces and manual or semi-automatic digitisation of muscle paths from medical images. In this study, a new scaling method combining non-linear scaling with reconstructions of bone surfaces using statistical shape modelling is presented. Statistical Shape Models (SSMs) of femur and tibia/fibula were used to reconstruct bone surfaces of nine subjects. Reference models were created by morphing manually digitised muscle paths to mean shapes of the SSMs using non-linear transformations and inter-subject variability was calculated. Subject-specific models of muscle attachment and via points were created from three reference models. The accuracy was evaluated by calculating the differences between the scaled and manually digitised models. The points defining the muscle paths showed large inter-subject variability at the thigh and shank – up to 26 mm; this was found to limit the accuracy of all studied scaling methods. Errors for the subject-specific muscle point reconstructions of the thigh could be decreased by 9% to 20% by using the non-linear scaling compared to a typical linear scaling method. We conclude that the proposed non-linear scaling method is more accurate than linear scaling methods. Thus, when combined with the ability to reconstruct bone surfaces from incomplete or scattered geometry data using statistical shape models our proposed method is an alternative to linear scaling methods.
Grigoriadis G, Newell N, Carpanen D, et al., 2016, Material properties of the heel fat pad across strain rates, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 65, Pages: 398-407, ISSN: 1751-6161
The complex structural and material behaviour of the human heel fat pad determines the transmission of plantar loading to the lower limb across a wide range of loading scenarios; from locomotion to injurious incidents. The aim of this study was to quantify the hyper-viscoelastic material properties of the human heel fat pad across strains and strain rates. An inverse finite element (FE) optimisation algorithm was developed and used, in conjunction with quasi-static and dynamic tests performed to five cadaveric heel specimens, to derive specimen-specific and mean hyper-viscoelastic material models able to predict accurately the response of the tissue at compressive loading of strain rates up to 150 s−1. The mean behaviour was expressed by the quasi-linear viscoelastic (QLV) material formulation, combining the Yeoh material model (C10=0.1MPa, C30=7MPa, K=2GPa) and Prony׳s terms (A1=0.06, A2=0.77, A3=0.02 for τ1=1ms, τ2=10ms, τ3=10s). These new data help to understand better the functional anatomy and pathophysiology of the foot and ankle, develop biomimetic materials for tissue reconstruction, design of shoe, insole, and foot and ankle orthoses, and improve the predictive ability of computational models of the foot and ankle used to simulate daily activities or predict injuries at high rate injurious incidents such as road traffic accidents and underbody blast.
Eftaxiopoulou T, Chaillot V, Bull AMJ, 2016, Interaction between equipment and athlete performance in racket sports: A cricketing story, Sports Innovation, Technology and Research, Pages: 43-62, ISBN: 9781786340412
Greenberg N, Bull A, Wessely S, 2016, Chilcot: Physical and mental legacy of Iraq war on UK service personnel, BMJ, Vol: 354, ISSN: 0959-8138
Barnett-Vanes A, Sharrock A, Eftaxiopoulou T, et al., 2016, CD43Lo classical monocytes participate in the cellular immune response to isolated primary blast lung injury, Journal of Trauma and Acute Care Surgery, Vol: 81, Pages: 500-511, ISSN: 2163-0763
BACKGROUND: Understanding of the cellular immune response to primary blast lung injury (PBLI) is limited, with only the neutrophil response well documented. Moreover, its impact on the immune response in distal organs remains poorly understood. In this study, a rodent model of isolated primary blast injury was used to investigate the acute cellular immune response to isolated PBLI in the circulation and lung; including the monocyte response, and investigate distal sub-acute immune effects in the spleen and liver 6hr after injury. METHODS: Rats were subjected to a shock wave (~135kPa overpressure, 2ms duration) inducing PBLI or sham procedure. Rat physiology was monitored and at 1, 3 and 6 hr thereafter blood, lung, and Broncho-alveolar lavage fluid (BALF) were collected and analysed by flow cytometry (FCM), ELISA and Histology. In addition, at 6hr spleen and liver were collected and analysed by FCM. RESULTS: Lung histology confirmed pulmonary barotrauma and inflammation. This was associated with rises in CXCL-1, IL-6, TNF-α and albumin protein in the BALF. Significant acute increases in blood and lung neutrophils and CD43Lo/His48Hi (classical) monocytes/macrophages were detected. No significant changes were seen in blood or lung 'non-classical' monocyte, NK, B or T Cells. In the BALF, significant increases were seen in neutrophils, CD43Lo monocyte-macrophages and MCP-1. Significant increases in CD43Lo and Hi monocyte-macrophages were detected in the spleen at 6hr. CONCLUSIONS: This study reveals a robust and selective response of CD43Lo/His48Hi (classical) monocytes - in addition to neutrophils - in blood and lung tissue following PBLI. An increase in monocyte-macrophages was also observed in the spleen at 6hr. This profile of immune cells in the blood and BALF could present a new research tool for translational studies seeking to monitor, assess or attenuate the immune response in blast injured patients. EVIDENCE: Experimental laboratory study.WC- 300.
Buckeridge EM, Weinert-Aplin RA, Bull AM, et al., 2016, Influence of foot-stretcher height on rowing technique and performance, Sports Biomechanics, Vol: 15, ISSN: 1752-6116
Strength, technique, and coordination are crucial to rowing performance, but external interventions such as foot-stretcher set-up can fine-tune technique and optimise power output. For the same resultant force, raising the height of foot-stretchers on a rowing ergometer theoretically alters the orientation of the resultant force vector in favour of the horizontal component. This study modified foot-stretcher heights and examined their instantaneous effect on foot forces and rowing technique. Ten male participants rowed at four foot-stretcher heights on an ergometer that measured handle force, stroke length, and vertical and horizontal foot forces. Rowers were instrumented with motion sensors to measure ankle, knee, hip, and lumbar–pelvic kinematics. Key resultant effects of increased foot-stretcher heights included progressive reductions in horizontal foot force, stroke length, and pelvis range of motion. Raising foot-stretcher height did not increase the horizontal component of foot force as previously speculated. The reduced ability to anteriorly rotate the pelvis at the front of the stroke may be a key obstacle in gaining benefits from raised foot-stretcher heights. This study shows that small changes in athlete set-up can influence ergometer rowing technique, and rowers must individually fine-tune their foot-stretcher height to optimise power transfer through the rowing stroke on an ergometer.
Bull AMJ, Eftaxiopoulou T, Persad L, 2016, Assessment of Performance Parameters of a Series of Five ‘Historical’ Cricket Bat Designs, Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, Vol: 231, Pages: 57-62, ISSN: 1754-3371
The performance of five different bat designs, from different eras spanning from 1905 to 2013, was assessed to addressthe question whether the changes in bat design over the years have resulted in a performance advantage to the batsman.Moment of inertia and ‘freely suspended’ vibration analysis tests were conducted, as these physical properties have beendirectly associated with rebound characteristics of the bats. Results showed that changes in the blade’s profile such asdistribution of the blade’s weight along the edges and closer to the toe have resulted in a clear performance advantageof the newest bats in comparison with older designs. These results add to the weight of evidence in cricket that thegame has changed to the benefit of the batsman and additional changes to bat design are conceivable as modern engineeringtools are applied to further optimise performance.
Amabile C, Bull A, Kedgley A, 2016, The centre of rotation of the shoulder complex and the effect of normalisation, Journal of Biomechanics, Vol: 49, Pages: 1938-1943, ISSN: 1873-2380
Shoulder motions consist of a composite movement of three joints and one pseudo-joint, which together dictate the humerothoracic motion. The purpose of this work was to quantify the location of the centre of rotation (CoR) of the shoulder complex as a whole. Dynamic motion of 12 participants was recorded using optical motion tracking during coronal, scapular and sagittal plane elevation. The instantaneous CoR was found for each angle of elevation using helical axes projected onto the three planes of motion. The location of an average CoR for each plane was evaluated using digitised and anthropometric measures for normalisation. When conducting motion in the coronal, scapular, and sagittal planes respectively, the coefficients for locating the CoRs of the shoulder complex are −61%, −61%, and −65% of the anterior-posterior dimension – the vector between the midpoint of the incisura jugularis and the xiphoid process and the midpoint of the seventh cervical vertebra and the eighth thoracic vertebra; 0%, −1%, and −2% of the superior-inferior dimension – the vector between the midpoint of the acromioclavicular joints and the midpoint of the anterior superior iliac spines; and 57%, 57%, and 78% of the medial-lateral dimension −0.129 times the height of the participant. Knowing the location of the CoR of the shoulder complex as a whole enables improved participant positioning for evaluation and rehabilitation activities that involve movement of the hand with a fixed radius, such as those that employ isokinetic dynamometers.
Campos-Pires R, Dickinson R, 2016, Modelling Blast Brain Injury, Blast Injury Science and Engineering A Guide for Clinicians and Researchers, Editors: Clasper, Bull, Mahoney, Publisher: Springer, Pages: 173-182, ISBN: 9783319218670
The consequences of blast traumatic brain injury (blast-TBI) in humans are largely determined by the characteristics of the trauma insult and, within certain limits, the individual responses to the lesions inflicted (1). In blast-TBI the mechanisms of brain vulnerability to the detonation of an explosive device are not entirely understood. They most likely result from a combination of the different physical aspects of the blast phenomenon, specifically extreme pressure oscillations (blast-overpressure wave), projectile penetrating fragments and acceleration-deceleration forces, creating a spectrum of brain injury that ranges from mild to severe blast-TBI (2). The pathophysiology of penetrating and inertially-driven blast-TBI has been extensively investigated for many years. However, the brain damage caused by blast-overpressure is much less understood and is unique to this type of TBI (3). Indeed, there continues to be debate about how the pressure wave is transmitted and reflected through the brain and how it causes cellular damage (4). No single model can mimic the clinical and mechanical complexity resulting from a real life blast-TBI (3). The different models, non-biological (in silico or surrogate physical) and biological (ex vivo, in vitro or in vivo), tend to complement each other.
Newell N, Masouros SD, 2016, Testing and development of mitigation systems for tertiary blast, Blast Injury Science and Engineering A Guide for Clinicians and Researchers, Editors: Bull, Clasper, Mahoney, Publisher: Springer, Pages: 249-255, ISBN: 9783319218670
Biomechanics in blast is a key discipline in blast injury science and engineering that addresses the consequences of high forces, large deformations and extreme failure and thus relates closely to knowledge of materials science (Chap. 3) and ...
Newell N, Salzar R, Bull AMJ, et al., 2016, A validated numerical model of a lower limb surrogate to investigate injuries caused by under-vehicle explosions, Journal of Biomechanics, Vol: 49, Pages: 710-717, ISSN: 0021-9290
Under-vehicle explosions often result in injury of occupants׳ lower extremities. The majority of these injuries are associated with poor outcomes. The protective ability of vehicles against explosions is assessed with Anthropometric Test Devices (ATDs) such as the MIL-Lx, which is designed to behave in a similar way to the human lower extremity when subjected to axial loading. It incorporates tibia load cells, the response of which can provide an indication of the risk of injury to the lower extremity through the use of injury risk curves developed from cadaveric experiments. In this study an axisymmetric finite element model of the MIL-Lx with a combat boot was developed and validated. Model geometry was obtained from measurements taken using digital callipers and rulers from the MIL-Lx, and using CT images for the combat boot. Appropriate experimental methods were used to obtain material properties. These included dynamic, uniaxial compression tests, quasi-static stress-relaxation tests and 3 point bending tests. The model was validated by comparing force-time response measured at the tibia load cells and the amount of compliant element compression obtained experimentally and computationally using two blast-injury experimental rigs. Good correlations between the numerical and experimental results were obtained with both. This model can now be used as a virtual test-bed of mitigation designs and in surrogate device development.
Eftaxiopoulou T, Barnett-Vanes A, Arora H, et al., 2016, Prolonged but not short duration blast waves elicit acute inflammation in a rodent model of primary blast limb trauma, Injury, Vol: 47, Pages: 625-632, ISSN: 0020-1383
BackgroundBlast injuries from conventional and improvised explosive devices account for 75% of injuries from current conflicts; of these over 70% involve the limbs. Variable duration and magnitude of blast wave loading occurs in real-life explosions and is hypothesised to cause different injuries. While a number of in-vivo models report the inflammatory response to blast injuries, the extent of this response has not been investigated with respect to the duration of the primary blast wave. The relevance is that explosions in open air are of short duration compared to those in confined spaces. MethodsHind limbs of adult Sprauge-Dawley rats were subjected to focal isolated primary blast waves of varying overpressure (1.8-3.65kPa) and duration (3.0-11.5ms), utilising a shock tube and purpose built experimental rig. Rats were monitored during and after blast. At 6 and 24hrs after exposure blood, lungs, liver and muscle tissue were collected and prepared for histology and flow cytometry.ResultsAt 6hrs increases in circulating neutrophils and CD43Lo/His48Hi monocytes were observed in rats subjected to longer duration blast waves. This was accompanied by increases in circulating pro-inflammatory chemo/cytokines KC and IL-6. No changes were observed with shorter duration blast waves irrespective of overpressure. In all cases, no histological damage was observed in muscle, lung or liver. By 24hrs post-blast all inflammatory parameters had normalised. ConclusionsWe report the development of a rodent model of primary blast limb trauma that is the first to highlight an important role played by blast wave duration and magnitude in initiating acute inflammatory response following limb injury in the absence of limb fracture or penetrating trauma. The combined biological and mechanical method developed can be used to further understand the complex effects of blast waves in a range of different tissues and organs in-vivo.
Southgate DFL, Childs PRN, Bull AMJ, 2016, Sports Innovation, Technology and Research, Publisher: World Scientific, ISBN: 9781786340412
Sports Innovation, Technology and Research gives an insight into recent research and design projects at Imperial College London. It presents the on-going development of a diverse range of areas from elite rowing performance to impact protection to sporting amenities in communities.Also included are descriptions of some of the latest innovations that have been developed as part of the Rio Tinto Sports Innovation Challenge, an initiative that tasked engineering students to design, build and implement Paralympic and other sporting equipment. It offers a glimpse at the breadth of creativity that can be achieved when human centred design is applied to an area such as disabled sport. It also shows the potential that design and engineering have to contribute to healthy lifestyles and the generation of whole new sporting domains.
Ding Z, Nolte D, Tsang CK, et al., 2015, In Vivo Knee Contact Force Prediction Using Patient-Specific Musculoskeletal Geometry in a Segment-Based Computational Model., Journal of Biomechanical Engineering-Transactions of the ASME, Vol: 138, ISSN: 0148-0731
Segment-based musculoskeletal models allow the prediction of muscle, ligament and joint forces without making assumptions regarding joint degrees of freedom. The dataset published for the "Grand Challenge Competition to Predict In Vivo Knee Loads" provides directly-measured tibiofemoral contact forces for activities of daily living. For the "Sixth Grand Challenge Competition to Predict In Vivo Knee Loads", blinded results for "smooth" and "bouncy" gait trials were predicted using a customised patient-specific musculoskeletal model. For an unblinded comparison the following modifications were made to improve the predictions: • further customisations, including modifications to the knee centre of rotation; • reductions to the maximum allowable muscle forces to represent known loss of strength in knee arthroplasty patients; and • a kinematic constraint to the hip joint to address the sensitivity of the segment-based approach to motion tracking artefact. For validation, the improved model was applied to normal gait, squat and sit-to-stand for three subjects. Comparisons of the predictions with measured contact forces showed that segment-based musculoskeletal models using patient-specific input data can estimate tibiofemoral contact forces with root mean square errors (RMSEs) of 0.48-0.65 times body weight (BW) for normal gait trials. Tibiofemoral contact force patterns were estimated with an average coefficient of determination of 0.81 and with RMSEs of 0.46-1.01 times BW for squatting and 0.70-0.99 times BW for sit-to-stand tasks. This is comparable to the best validations in the literature using alternative models.
McGregor AH, Buckeridge E, Murphy AJ, et al., 2015, Communicating and using biomechanical measures through visual cues to optimise safe and effective rowing, Proceedings of the Institution of Mechanical Engineers Part P - Journal of Sports Engineering and Technology, Vol: 230, Pages: 246-252, ISSN: 1754-3371
The use of representations of physiological parameters to an athlete and coach during training is becoming increasingly common. Their utility is enhanced when the appropriate data are captured and communicated in real time for the athlete to make training adjustments immediately. The aim of this work was to develop a biofeedback tool for ergometer rowing by creating a data acquisition system, data analysis and interpretation that could be conducted in real time and a feedback system with appropriate cues to the athlete. This fourteen year study resulted in a set of measured parameters with inferred correlations between the directly measured parameters acquired during the activity and performance and injury outcome measures. These parameters were represented through a customisable visual display in real-time during ergometer training. An athlete and coach open survey was conducted to assess the utility of the biofeedback tool. This survey found that all parties valued the feedback system since it provided a common language to identify body motion and performance parameters in a way that was accessible and meaningful to all parties as well available during training and coaching. Athletes noted that it helped them to understand body segment motion and its relation to performance and both coaches and medical staff valued this in enhancing performance and monitoring injury and injury prediction. There was also speculation that the system help to underpin coaching practice and its translation to the team. The biofeedback tool has been adopted by the British elite rowing squad.
Humphries A, Cirovic S, Bull AM, et al., 2015, Assessment of the glenohumeral joint's active and passive axial rotational range., Journal of Shoulder and Elbow Surgery, Vol: 24, Pages: 1974-1981, ISSN: 1532-6500
BACKGROUND: Assessment of the range of axial rotation of the glenohumeral joint will improve understanding of shoulder function, with applications in shoulder rehabilitation and sports medicine. However, there is currently no complete description of motion of the joint. The study aimed to develop a reliable protocol to quantify the internal and external axial rotations of the glenohumeral joint during active and passive motion at multiple humeral positions. METHODS: Optical motion tracking was used to collect kinematic data from 20 healthy subjects. The humerus was positioned at 60°, 90°, and 120° of humerothoracic elevation in the coronal, scapular, and sagittal planes. Internal and external rotations were measured at each position for active and passive motion, where intrasubject standard deviations were used to assess variations in internal-external rotations. RESULTS: The protocol showed intrasubject variability in the axial rotational range of <5° for active and passive rotations at all humeral positions. Maximum internal rotation was shown to be dependent on humeral position, where a reduced range was measured in the sagittal plane (P < .001) and at 120° elevations (P < .001). Conversely, maximum external rotations were not affected by humeral position. CONCLUSION: The results describe normal ranges of internal-external rotation of the glenohumeral joint at multiple humeral positions. The protocol's low variability means that it could be used to test whether shoulder pathologic conditions lead to changes in axial rotational range at specific humeral positions.
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