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  • Journal article
    Ding Z, Nolte D, Tsang CK, Cleather DJ, Kedgley AE, Bull AMet 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.
  • Journal article
    McGregor AH, Buckeridge E, Murphy AJ, Bull AMJet 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.
  • Journal article
    Humphries A, Cirovic S, Bull AM, Hearnden A, Shaheen AFet 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.
  • Journal article
    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.
  • Journal article
    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.
  • Book chapter
    Masouros S, Halewood C, Bull A, Amis Aet al., 2015,

    Biomechanics

    , Expertise orthopadie und unfallchirurgie: Knie, Editors: Kohn, ISBN: 978-3-1317500-1-3
  • Journal article
    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.
  • Journal article
    Edwards DS, Barbur SAR, Bull AMJ, Stranks GJet 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.
  • Journal article
    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.
  • Journal article
    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.

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
Department of Bioengineering
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Imperial College London
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