Publications
358 results found
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.
Weinert-Aplin RA, Bull AM, McGregor AH, 2015, Orthotic Heel Wedges Do Not Alter Hindfoot Kinematics and Achilles Tendon Force During Level and Inclined Walking in Healthy Individuals., Journal of Applied Biomechanics, Vol: 32, Pages: 160-170, ISSN: 1543-2688
Conservative treatments such as in-shoe orthotic heel wedges to treat musculoskeletal injuries are not new. However, weak evidence supporting their use in the management of Achilles tendonitis suggests the mechanism by which these heel wedges work remains poorly understood. It was the aim of this study to test the underlying hypothesis that heel wedges can reduce Achilles tendon load. A musculoskeletal modelling approach was used to quantify changes in lower limb mechanics when walking due to the introduction of 12mm orthotic heel wedges. 19 healthy volunteers walked on an inclinable walkway while optical motion, forceplate and plantar pressure data were recorded. Walking with heel wedges increased ankle dorsiflexion moments and reduced plantar flexion moments. This resulted in increased peak ankle dorsiflexor muscle forces during early stance and reduced Tibialis Posterior and toe flexor muscles forces during late stance. Heel wedges did not reduce overall Achilles tendon force during any walking condition, but did redistribute load from the medial to lateral triceps surae during inclined walking. These results add to the body of clinical evidence confirming that heel wedges do not reduce Achilles tendon load and our findings provide an explanation as to why this may be the case.
Cheong VS, Bull AMJ, 2015, A novel specimen-specific methodology to optimise the alignment of long bones for experimental testing, Journal of Biomechanics, ISSN: 1873-2380
The choice of coordinate system and alignment of bone will affect the quantification of mechanical properties obtained during in-vitro biomechanical testing. Where these are used in predictive models, such as finite element analysis, the fidelic description of these properties is paramount. Currently in bending and torsional tests, bones are aligned on a pre-defined fixed span based on the reference system marked out. However, large inter-specimen differences have been reported. This suggests a need for the development of a specimen-specific alignment system for use in experimental work. Eleven ovine tibia were used in this study and three-dimensional surface meshes were constructed from micro-Computed Tomography scan images. A novel, semi-automated algorithm was developed and applied to the surface meshes to align the whole bone based on its calculated principal directions. Thereafter, the code isolates the optimised location and length of each bone for experimental testing. This resulted in a lowering of the second moment of area about the chosen bending axis in the central region. More importantly, the optimisation method decreases the irregularity of the shape of the cross-sectional slices as the unbiased estimate of the population coefficient of variation of the second moment of area decreased from a range of (0.210-0.435) to (0.145-0.317) in the longitudinal direction, indicating a minimisation of the product moment, which causes eccentric loading. Thus, this methodology serves as an important pre-step to align the bone for mechanical tests or simulation work, is optimised for each specimen, ensures repeatability, and is general enough to be applied to any long bone.
Masouros S, Halewood C, Bull A, et al., 2015, Biomechanics, Expertise orthopadie und unfallchirurgie: Knie, Editors: Kohn, ISBN: 978-3-1317500-1-3
Prinold JA, Bull AM, 2015, Scapula kinematics of pull-up techniques: avoiding impingement risk with training changes, Journal of Science and Medicine in Sport, Vol: 19, Pages: 629-635, ISSN: 1440-2440
OBJECTIVES: Overhead athletic activities and scapula dyskinesia are linked with shoulder pathology; pull-ups are a common training method for some overhead sports. Different pull-up techniques exist: anecdotally some are easier to perform, and others linked to greater incidences of pathology. This study aims to quantify scapular kinematics and external forces for three pull-up techniques, thus discussing potential injury implications. DESIGN: An observational study was performed with eleven participants (age=26.8±2.4 years) who regularly perform pull-ups. METHODS: The upward motions of three pull-up techniques were analysed: palms facing anterior, palms facing posterior and wide-grip. A skin-fixed scapula tracking technique with attached retro-reflective markers was used. RESULTS: High intra-participant repeatability was observed: mean coefficients of multiple correlations of 0.87-1.00 in humerothoracic rotations and 0.77-0.90 for scapulothoracic rotations. Standard deviations of hand force was low: <5% body weight. Significantly different patterns of humerothoracic, scapulothoracic and glenohumeral kinematics were observed between the pull-up techniques. The reverse technique has extreme glenohumeral internal-external rotation and large deviation from the scapula plane. The wide technique has a reduced range of pro/retraction in the same HT plane of elevation and 90° of arm abduction with 45° external rotation was observed. All these factors suggest increased sub-acromial impingement risk. CONCLUSIONS: The scapula tracking technique showed high repeatability. High arm elevation during pull-ups reduces sub-acromial space and increases pressure, increasing the risk of impingement injury. Wide and reverse pull-ups demonstrate kinematics patterns linked with increased impingement risk. Weight-assisted front pull-ups require further investigation and could be recommended for weaker participants.
Edwards DS, Barbur SAR, Bull AMJ, et al., 2015, Posterior mini-incision total hip arthroplasty controls the extent of post-operative formation of heterotopic ossification., Eur J Orthop Surg Traumatol, Vol: 25, Pages: 1051-1055
Heterotopic ossification (HO) is the formation of bone at extra-skeletal sites. Reported rates of HO after hip arthroplasty range from 8 to 90 %; however, it is only severe cases that cause problems clinically, such as joint stiffness. The effects of surgical-related controllable intra-operative risk factors for the formation of HO were investigated. Data examined included gender, age of patient, fat depth, length of operation, incision length, prosthetic fixation method, the use of pulsed lavage and canal brush, and component size and material. All cases were performed by the same surgeon using the posterior approach. A total of 510 cases of hip arthroplasty were included, with an overall rate of HO of 10.2 %. Longer-lasting operations resulted in higher grades of HO (p = 0.047). Incisions >10 cm resulted in more widespread HO formation (p = 0.021). No further correlations were seen between HO formation and fat depth, blood loss, instrumentation, fixation methods or prosthesis material. The mini-incision approach is comparable to the standard approach in the aetiology of HO formation, and whilst the rate of HO may not be controllable, a posterior mini-incision approach can limit its extent.
Buckeridge EM, Bull AMJ, McGregor AH, 2015, Incremental training intensities increases loads on the lower back of elite female rowers, Journal of Sports Sciences, ISSN: 0264-0414
Lumbar-pelvic kinematics change in response to increasing rowing stroke rates, but little is known about the effect of incremental stroke rates on changes in joint kinetics and their implications for injury. The purpose of this study was to quantify the effects of incremental rowing intensities on lower limb and lumbar-pelvic kinetics. Twelve female rowers performed an incremental test on a rowing ergometer. Kinematic data of rowers’ ankle, knee, hip and lumbar-pelvic joints, as well as external forces at the handle, seat and foot-stretchers of the rowing machine were recorded. Inter-segmental moments and forces were calculated using inverse dynamics and were compared across stroke rates using repeated measures ANOVA. Rowers exhibited increases in peak ankle and L5/S1 extensor moments, reductions in peak knee moments and no change in peak hip moments, with respect to stroke rate. Large shear and compressive forces were seen at L5/S1 and increased with stroke rate (P < 0.05). This coincided with increased levels of lumbar-pelvic flexion. High levels of lumbar-pelvic loading at higher stroke rates have implications with respect to injury and indicated that technique was declining, leading to increased lumbar-pelvic flexion. Such changes are not advantageous to performance and can potentially increase the risk of developing injuries.
Pandis P, Prinold JAI, Bull AMJ, 2015, Shoulder muscle forces during driving: sudden steering can load the rotator cuff beyond its repair limit Clinical Biomechanics, Clinical Biomechanics, Vol: 30, Pages: 839-846, ISSN: 1879-1271
BackgroundDriving is one of the most common everyday tasks and the rotator cuff muscles are the primary shoulder stabilisers. Muscle forces during driving are not currently known, yet knowledge of these would influence important clinical advice such as return to activities after surgery. The aim of this study is to quantify shoulder and rotator cuff muscle forces during driving in different postures.MethodsA musculoskeletal modelling approach is taken, using a modified driving simulator in combination with an upper limb musculoskeletal model (UK National Shoulder Model). Motion data and external force vectors were model inputs and upper limb muscle and joint forces were the outputs.FindingsComparisons of the predicted glenohumeral joint forces were compared to in vivo literature values, with good agreement demonstrated (61 SD 8% body weight mean peak compared to 60 SD 1% body weight mean peak). High muscle activation was predicted in the rotator cuff muscles; particularly supraspinatus (mean 55% of the maximum and up to 164 SD 27 N). This level of loading is up to 72% of mean failure strength for supraspinatus repairs, and could therefore be dangerous for some cases. Statistically significant and large differences are shown to exist in the joint and muscle forces for different driving positions as well as steering with one or both hands (up to 46% body weight glenohumeral joint force).InterpretationThese conclusions should be a key consideration in rehabilitating the shoulder after surgery, preventing specific upper limb injuries and predicting return to driving recommendations.
Cleather DJ, Bull AM, 2015, The development of a segment-based musculoskeletal model of the lower limb: introducing FreeBody., Royal Society Open Science, Vol: 2, ISSN: 2054-5703
Traditional approaches to the biomechanical analysis of movement are joint-based; that is the mechanics of the body are described in terms of the forces and moments acting at the joints, and that muscular forces are considered to create moments about the joints. We have recently shown that segment-based approaches, where the mechanics of the body are described by considering the effect of the muscle, ligament and joint contact forces on the segments themselves, can also prove insightful. We have also previously described a simultaneous, optimization-based, musculoskeletal model of the lower limb. However, this prior model incorporates both joint- and segment-based assumptions. The purpose of this study was therefore to develop an entirely segment-based model of the lower limb and to compare its performance to our previous work. The segment-based model was used to estimate the muscle forces found during vertical jumping, which were in turn compared with the muscular activations that have been found in vertical jumping, by using a Geers' metric to quantify the magnitude and phase errors. The segment-based model was shown to have a similar ability to estimate muscle forces as a model based upon our previous work. In the future, we will evaluate the ability of the segment-based model to be used to provide results with clinical relevance, and compare its performance to joint-based approaches. The segment-based model described in this article is publicly available as a GUI-based Matlab® application and in the original source code (at www.msksoftware.org.uk).
Edwards DS, Phillip RD, Bosanquet N, et al., 2015, What Is the magnitude and long-term economic cost of care of the British military Afghanistan amputee cohort?, Clinical Orthopaedics and Related Research, Vol: 473, Pages: 2848-2855, ISSN: 0009-921X
BackgroundPersonal protection equipment, improved early medical care, and rapid extraction of the casualty have resulted in more injured service members who served in Afghanistan surviving after severe military trauma. Many of those who survive the initial trauma are faced with complex wounds such as multiple amputations. Although costs of care can be high, they have not been well quantified before. This is required to budget for the needs of the injured beyond their service in the armed forces.Question/purposesThe purposes of this study were (1) to quantify and describe the extent and nature of traumatic amputations of British service personnel from Afghanistan; and (2) to calculate an estimate of the projected long-term cost of this cohort.MethodsA four-stage methodology was used: (1) systematic literature search of previous studies of amputee care cost; (2) retrospective analysis of the UK Joint Theatre Trauma and prosthetic database; (3) Markov economic algorithm for healthcare cost and sensitivity analysis of results; and (4) statistical cost comparison between our cohort and the identified literature.ResultsFrom 2003 to 2014, 265 casualties sustained 416 amputations. The average number of limbs lost per casualty was 1.6. The most common type of amputation was a transfemoral amputation (153 patients); the next most common amputation type was unilateral transtibial (143 patients). Using a Markov model of healthcare economics, it is estimated that the total 40-year cost of the UK Afghanistan lower limb amputee cohort is £288 million (USD 444 million); this figure estimates cost of trauma care, rehabilitation, and prosthetic costs. A sensitivity analysis on our model demonstrated a potential ± 6.19% variation in costs.ConclusionsThe conflict in Afghanistan resulted in high numbers of complex injuries. Our findings suggest that a long-term facility to budget for veterans’ health care is necessary.
Weinert-Aplin RA, Bull AMJ, McGregor AH, 2015, Investigating the Effects of Knee Flexion during the Eccentric Heel-Drop Exercise, Journal of Sports Science and Medicine, Vol: 14, Pages: 459-465, ISSN: 1303-2968
This study aimed to characterise the biomechanics of the widelypracticed eccentric heel-drop exercises used in the managementof Achilles tendinosis. Specifically, the aim was to quantifychanges in lower limb kinematics, muscle lengths and Achillestendon force, when performing the exercise with a flexed kneeinstead of an extended knee. A musculoskeletal modelling approachwas used to quantify any differences between theseversions of the eccentric heel drop exercises used to treat Achillestendinosis. 19 healthy volunteers provided a group fromwhich optical motion, forceplate and plantar pressure data wererecorded while performing both the extended and flexed kneeeccentric heel-drop exercises over a wooden step when barefootor wearing running shoes. This data was used as inputs into ascaled musculoskeletal model of the lower limb. Range of anklemotion was unaffected by knee flexion. However, knee flexionwas found to significantly affect lower limb kinematics, intersegmentalloads and triceps muscle lengths. Peak Achilles loadwas not influenced despite significantly reduced peak ankleplantarflexion moments (p < 0.001). The combination of reducedtriceps lengths and greater ankle dorsiflexion, coupledwith reduced ankle plantarflexion moments were used to providea basis for previously unexplained observations regardingthe effect of knee flexion on the relative loading of the tricepsmuscles during the eccentric heel drop exercises. This findingquestions the role of the flexed knee heel drop exercise whenspecifically treating Achilles tendinosis
Bull AMJ, Sabharwal S, Patel NK, et al., 2015, Surgical interventions for anterior shoulder instability in rugby players: A systematic review, World Journal of Orthopedics, Vol: 6, Pages: 400-408, ISSN: 2218-5836
AIM: To systematically evaluate the evidence-based literature on surgical treatment interventions for elite rugby players with anterior shoulder instability. METHODS: We conducted a systematic review according to the PRISMA guidelines, a literature search was performed in PubMed, EMBASE and Google Scholar using the following search terms: “rugby” and “shoulder” in combination with “instability” or “dislocation”. All articles published from inception of the included data sources to January 1st 2014 that evaluated surgical treatment of elite rugby players with anterior shoulder instability were examined. RESULTS: Only five studies were found that met the eligibility criteria. A total of 379 shoulders in 376 elite rugby union and league players were included. All the studies were retrospective cohort or case series studies. The mean Coleman Methodological Score for the 5 studies was 47.4 (poor). Owing to heterogeneity amongst the studies, quantitative synthesis was not possible, however a detailed qualitative synthesis is reported. The overall recurrence rate of instability after surgery was 8.7%, and the mean return to competitive play, where reported, was 13 mo.CONCLUSION: Arthroscopic stabilization has been performed successfully in acute anterior instability and there is a preference for open Latarjet-type procedures when instability is associated with osseous defects.
Shaheen AF, Bull AMJ, Alexander CM, 2015, Rigid and Elastic taping changes scapular kinematics and pain in subjects with shoulder impingement syndrome; an experimental study, JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY, Vol: 25, Pages: 84-92, ISSN: 1050-6411
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Newell N, Bull AMJ, Masouros SD, 2015, A computational model for prediction of lower-limb injury in under-vehicle explosions, Pages: 748-749
Bonner TJ, Newell N, Karunaratne A, et al., 2015, Strain-rate sensitivity of the lateral collateral ligament of the knee, Journal of The Mechanical Behavior of Biomedical Materials, Vol: 41, Pages: 261-270, ISSN: 1751-6161
The material properties of ligaments are not well characterized at rates of deformation that occur during high-speed injuries. The aim of this study was to measure the material properties of lateral collateral ligament of the porcine stifle joint in a uniaxial tension model through strain rates in the range from 0.01 to 100/s. Failure strain, tensile modulus and failure stress were calculated. Across the range of strain rates, tensile modulus increased from 288 to 905 MPa and failure stress increased from 39.9 to 77.3 MPa. The strain-rate sensitivity of the material properties decreased as deformation rates increased, and reached a limit at approximately 1/s, beyond which there was no further significant change. In addition, time resolved microfocus small angle X-ray scattering was used to measure the effective fibril modulus (stress/fibril strain) and fibril to tissue strain ratio. The nanoscale data suggest that the contribution of the collagen fibrils towards the observed tissue-level deformation of ligaments diminishes as the loading rate increases. These findings help to predict the patterns of limb injuries that occur at different speeds and improve computational models used to assess and develop mitigation technology.
Cleather DJ, Southgate DFL, Bull AMJ, 2014, On the Role of the Patella, ACL and Joint Contact Forces in the Extension of the Knee, PLoS ONE, Vol: 9, ISSN: 1932-6203
Traditional descriptions of the knee suggest that the function of the patella is tofacilitate knee extension by increasing the moment arm of the quadriceps muscles.Through modelling and evidence from the literature it is shown in this paper that thepresence of the patella makes the ability of the quadriceps to rotate the thighgreater than their ability to rotate the tibia. Furthermore, this difference increases asthe knee is flexed, thus demonstrating a pattern that is consistent with many humanmovements. This paper also shows that the anterior cruciate ligament plays apreviously unheralded role in extending the shank and that translation at thetibiofemoral and patellofemoral joints is important in improving the capacity for thighrotation when the knee is flexed. This study provides new insights as to how thestructure of the knee is adapted to its purpose and illustrates how the functionalanatomy of the knee contributes to its extension function.
Cleather DJ, Southgate DFL, Bull AMJ, 2014, The role of the biarticular hamstrings and gastrocnemius muscles in closed chain lower limb extension, Journal of Theoretical Biology
The role of the biarticular muscles is a topic that has received considerable attention however their function is not well understood. In this paper, we argue that an analysis that is based upon considering the effect of the biarticular muscles on the segments that they span (rather than their effect on joint rotations) can be illuminating. We demonstrate that this understanding is predicated on a consideration of the relative sizes of the moment arms of a biarticular muscle about the two joints that it crosses. The weight of the previous literature suggests that the moment arms of both the biarticular hamstrings and gastrocnemius are smaller at the knee than at the hip or ankle (respectively). This in turn leads to the conclusion that both biarticular hamstrings and gastrocnemius are extensors of the lower limb. We show that the existence of these biarticular structures lends a degree of flexibility to the motor control strategies available for lower limb extension. In particular, the role of the gastrocnemius and biarticular hamstrings in permitting a large involvement of the quadriceps musculature in closed chain lower limb extension may be more important than is typically portrayed. Finally, the analysis presented in this paper demonstrates the importance of considering the effects of muscles on the body as a whole, not just on the joints they span.
Prinold JAI, Bull AMJ, 2014, Scaling and kinematics optimisation of the scapula and thorax in upper limb musculoskeletal models, Journal of Biomechanics, Vol: 47, Pages: 2813-2819, ISSN: 0021-9290
Accurate representation of individual scapula kinematics and subject geometries is vital in musculoskeletal models applied to upper limb pathology and performance. In applying individual kinematics to a model׳s cadaveric geometry, model constraints are commonly prescriptive. These rely on thorax scaling to effectively define the scapula׳s path but do not consider the area underneath the scapula in scaling, and assume a fixed conoid ligament length. These constraints may not allow continuous solutions or close agreement with directly measured kinematics.A novel method is presented to scale the thorax based on palpated scapula landmarks. The scapula and clavicle kinematics are optimised with the constraint that the scapula medial border does not penetrate the thorax. Conoid ligament length is not used as a constraint. This method is simulated in the UK National Shoulder Model and compared to four other methods, including the standard technique, during three pull-up techniques (n=11). These are high-performance activities covering a large range of motion.Model solutions without substantial jumps in the joint kinematics data were improved from 23% of trials with the standard method, to 100% of trials with the new method. Agreement with measured kinematics was significantly improved (more than 10° closer at p<0.001) when compared to standard methods. The removal of the conoid ligament constraint and the novel thorax scaling correction factor were shown to be key. Separation of the medial border of the scapula from the thorax was large, although this may be physiologically correct due to the high loads and high arm elevation angles.
Eftaxiopoulou T, Macdonald W, Britzman D, et al., 2014, Gait compensations in rats after a temporary nerve palsy quantified using temporo-spatial and kinematic parameters, JOURNAL OF NEUROSCIENCE METHODS, Vol: 232, Pages: 16-23, ISSN: 0165-0270
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Buckeridge EM, Bull AMJ, McGregor AH, 2014, Biomechanical determinants of elite rowing technique and performance, Scandinavian Journal of Medicine & Science in Sports, Vol: 25, Pages: e176-e183, ISSN: 0905-7188
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