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  • Journal article
    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).
  • Journal article
    Edwards DS, Phillip RD, Bosanquet N, Bull AMJ, Clasper JCet 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.
  • Journal article
    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
  • Journal article
    Bull AMJ, Sabharwal S, Patel NK, Reilly Pet 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.
  • Journal article
    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
  • Journal article
    Bonner TJ, Newell N, Karunaratne A, Pullen AD, Amis AA, Bull AMJ, Masouros SDet 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.
  • Conference paper
    Newell N, Bull AMJ, Masouros SD, 2015,

    A computational model for prediction of lower-limb injury in under-vehicle explosions

    , Pages: 748-749
  • Journal article
    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.
  • Journal article
    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.
  • Journal article
    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.

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

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Professor Anthony Bull
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Imperial College London
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