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• Journal article
  Nolte D, Ko S-T, Bull AMJ, Kedgley AEet al., 2020,

  Reconstruction of the lower limb bones from digitised anatomical landmarks using statistical shape modelling

  , Gait & Posture, Vol: 77, Pages: 269-275, ISSN: 0966-6362

  BackgroundBone shapes strongly influence force and moment predictions of kinematic and musculoskeletal models used in motion analysis. The precise determination of joint reference frames is essential for accurate predictions. Since clinical motion analysis typically does not include medical imaging, from which bone shapes may be obtained, scaling methods using reference subjects to create subject-specific bone geometries are widely used.Research questionThis study investigated if lower limb bone shape predictions from skin-based measurements, utilising an underlying statistical shape model (SSM) that corrects for soft tissue artefacts in digitisation, can be used to improve conventional linear scaling methods of bone geometries.MethodsSSMs created from 35 healthy adult femurs and tibiae/fibulae were used to reconstruct bone shapes by minimising the distance between anatomical landmarks on the models and those digitised in the motion laboratory or on medical images. Soft tissue artefacts were quantified from magnetic resonance images and then used to predict distances between landmarks digitised on the skin surface and bone. Reconstruction results were compared to linearly scaled models by measuring root mean squared distances to segmented surfaces, calculating differences of commonly used anatomical measures and the errors in the prediction of the hip joint centre.ResultsSSM reconstructed surface predictions from varying landmark sets from skin and bone landmarks were more accurate compared to linear scaling methods (2.60–2.95 mm vs. 3.66–3.87 mm median error; p < 0.05). No significant differences were found between SSM reconstructions from bony landmarks and SSM reconstructions from digitised landmarks obtained in the motion lab and therefore reconstructions using skin landmarks are as accurate as reconstructions from landmarks obtained from medical images.SignificanceThese results indicate that SSM reconstructions can be used to increase the accurac

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• Journal article
  Papi E, Bull AMJ, McGregor AH, 2020,

  Alteration of movement patterns in low back pain assessed by Statistical Parametric Mapping

  , Journal of Biomechanics, Vol: 100, Pages: 109597-109597, ISSN: 0021-9290

  Changes in movement pattern in low back pain (LBP) groups have been analysed by reporting predefined discrete variables. However, this approach does not consider the full kinematic data waveform and its dynamic information, potentially exposing the analysis to bias. Statistical Parametric Mapping (SPM) has been introduced and applied to 1 dimensional (D) kinematic variables allowing the assessment of data over time. The aims of this study were to assess differences in 3D kinematics patterns in people with and without LBP during functional tasks by using SPM and to investigate if SPM analysis was consistent with standard 3D range of motion (RoM) assessments. 3D joints kinematics of the spine and lower limbs were compared between 20 healthy controls and 20 participants with non-specific LBP during walking, sit-to-stand and lifting. SPM analysis showed significant differences in the 3Dkinematics of the lower thoracic segment, upper and lower lumbar segment and knee joint during walking and lifting mostly observed at the beginning and/or towards the end of the tasks. ROMs differed between groups in the lower thoracic segment (walking/sit-to-stand), upper and lower lumbar segments (walking/sit-to-stand/lifting), hip and knee (sit-to-stand/lifting). Based on these results, the two approaches can yield different data interpretations. SPM analysis allows the identification of differences in movement that occur over time. This adds value to LBP movement analysis as it allows an understanding of the LBP strategies adopted during motion that may not be conveyed by simple discrete parameters such as ROMs.

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• Journal article
  Bull A, Berthaume M, 2020,

  Human biological variation in sesamoid bone prevalence: the curious case of the fabella

  , Journal of Anatomy, Vol: 236, Pages: 228-242, ISSN: 0021-8782

  The fabella is a sesamoid bone located in the gastrocnemius behind the lateral femoral condyle. In humans, fabellae are 3.5 times more common today than they were 100 years ago, with prevalence rates varying between and within populations. In particular, fabellae have been assumed to be more common in Asians than non-Asians, equally common in men and women, potentially more common in older individuals, and bilateral cases (one per knee) appear to be more common than unilateral ones. The roles of genetic and environmental factors in this phenotypic variation have been hypothesized, but not rigorously investigated. Given its clinical and evolutionary significance (i.e., being associated with several knee ailments, causing medical issues on its own, interfering with medical devices, and being less common in humans compared to other mammals), it is important to comprehensively understand prevalence rate variation, and the roles of genetics and environmental factors in that variation. To address these questions, we performed a meta-analysis on data from a previously published systematic review to investigate possible variation in sexual dimorphic (n = 22 studies, 7,911 knees), ontogenetic (n = 10 studies, 4,391 knees), and global (n = 65 studies, 21,626 knees) fabella prevalence rates. In addition, we investigated what proportion of cases are bilateral (n = 37 studies, 900 individuals), and among unilateral cases (n = 20 studies, 204 individuals), if fabellae are more common in the left or right knee. Our results show that, today, fabellae are 2.47-2.60% more common in men than women, and prevalence rates increase ontogenetically into old age (i.e., 70 years old), implying that fabellae can ossify early (i.e., 12 years old) or late in life. Approximately 72.94% of cases are bilateral, and among unilateral ones, fabellae are equally common in right and left knees. There is marked regional variation in fabella prevalence rates, with rates being highest in Asia, followed by

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• Journal article
  Smith SHL, Reilly P, Bull AMJ, 2020,

  A musculoskeletal modelling approach to explain sit-to-stand difficulties in older people due to changes in muscle recruitment and movement strategies

  , Journal of Biomechanics, Vol: 98, ISSN: 0021-9290

  By 2050 the proportion of over 65s is predicted to be 20% of the population. The consequences of an age-related reduction in muscle mass have not been fully investigated and, therefore, the aim of the present study was to quantify the muscle and joint contact forces using musculoskeletal modelling, during a sit-to-stand activity, to better explain difficulties in performing everyday activities for older people. A sit-to-stand activity with and without the use of arm rests was observed in ninety-five male participants, placed into groups of young (aged 18-35 years), middle-aged (aged 40-60 years) or older adults (aged 65 years and over). Older participants demonstrated significantly lower knee extensor and joint forces than the young when not using arm rests, compensating through elevated hip extensor and ankle plantarflexor muscle activity. The older group were also found to have higher shoulder joint contact forces whilst using arm rests. This tendency to reorganise muscle recruitment to include neighbouring groups or other parts of the body could make everyday activities more susceptible to age-related functional decline. Reductions in leg strength, via age- or atrophy- related means, creates increased reliance on the upper body and may result in further lower limb atrophy through disuse. The eventual decline of upper body function reduces strength reserves, leading to increased vulnerability, dependence on others and risk of institutionalisation.

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• Journal article
  Ding Z, Gudel M, Smith SHL, Ademefun RA, Bull AMJet al., 2019,

  A femoral clamp to reduce soft tissue artefact: accuracy and reliability in measuring three-dimensional knee kinematics during gait

  , Journal of Biomechanical Engineering, Vol: 142, Pages: 044501-1-044501-8, ISSN: 0148-0731

  The accurate measurement of full sixdegrees-of-freedom(DOFs) knee joint kinematics is prohibited by soft tissue artifact (STA), which remains the greatest source of error. The purpose of this study was to present and assess a new femoral clampto reduce STA at the thigh. It was hypothesised that the device can preserve the natural knee joint kinematics pattern and outperform a conventional marker mounted rigid cluster during gait. 6Six healthy subjects were askedto walk barefoot on level ground with a cluster marker set (cluster gait) followed by a cluster-clamp-merged marker set (clamp gait) and their kinematics wasmeasured using the clustermethod in clustergait and thecluster and clamp methodssimultaneouslyin clamp gait. Two operators performed the gait measurement. A six DOFs knee joint model wasdeveloped to enable comparison withthe gold standard knee joint kinematics measured using adual fluoroscopic imaging technique. One-dimensional paired t-tests were used to compare the knee joint kinematics waveforms between cluster gait and clamp gait. The accuracy was assessed in terms of the root mean square error, coefficient of determination and Bland-Altman plots. Inter-operatorreliability was assessed15usingthe intra-class correlation coefficient.The result showed that the femoral clamp did not change the walking speed andknee joint kinematicswaveforms. Additionally, clamp gait reduced the rotationand translation errorsin the transverse plane and improved the inter-operator reliabilitywhen compared to the rigid cluster method, suggesting amore accurate and reliable measurement of knee joint kinematics.

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• Journal article
  Ding Z, Tsang C, Nolte D, Kedgley A, Bull Aet al., 2019,

  Improving musculoskeletal model scaling using an anatomical atlas: the importance of gender and anthropometric similarity to quantify joint reaction forces

  , IEEE Transactions on Biomedical Engineering, Vol: 66, Pages: 3444-3456, ISSN: 0018-9294

  Objective: The accuracy of a musculoskeletal model relies heavily on the implementation of the underlying anatomical dataset. Linear scaling of a generic model, despite being time and cost-efficient, produces substantial errors as it does not account for gender differences and inter-individual anatomical variations. The hypothesis of this study is that linear scaling to a musculoskeletal model with gender and anthropometric similarity to the individual subject produces similar results to the ones that can be obtained from a subject-specific model. Methods: A lower limb musculoskeletal anatomical atlas was developed consisting of ten datasets derived from magnetic resonance imaging of healthy subjects and an additional generic dataset from the literature. Predicted muscle activation and joint reaction force were compared with electromyography and literature data. Regressions based on gender and anthropometry were used to identify the use of atlas. Results: Primary predictors of differences for the joint reaction force predictions were mass difference for the ankle (p<0.001) and length difference for the knee and hip (p≤0.017) . Gender difference accounted for an additional 3% of the variance (p≤0.039) . Joint reaction force differences at the ankle, knee and hip were reduced by between 50% and 67% (p=0.005) when using a musculoskeletal model with the same gender and similar anthropometry in comparison with a generic model. Conclusion: Linear scaling with gender and anthropometric similarity can improve joint reaction force predictions in comparison with a scaled generic model. Significance: The scaling approach and atlas presented can improve the fidelity and utility of musculoskeletal models for subject-specific applications.

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• Journal article
  Smith SHL, Reilly P, Bull AMJ, 2019,

  Serratus anterior weakness is a key determinant of arm-assisted standing difficulties

  , Medical Engineering and Physics, Vol: 74, Pages: 41-48, ISSN: 1350-4533

  The ageing population has led to recent increases in musculoskeletal conditions, with muscle weakness a major contributor to functional decline. Understanding the early phases of muscle weakness will help devise treatments to extend musculoskeletal health. Little is understood of the effects of muscle weakness on everyday activities such as sit-to-stand, a determinant of mobility that, in the early stages of weakness, requires upper limb compensation. This experimental and computational modelling study investigated the effects of muscle weakness on upper-extremity muscle forces of 27 healthy adults when using arm rests. Weakness of 29 upper limb muscles was simulated by individually removing each from a musculoskeletal model. Serratus anterior weakness was highlighted as detrimental, with the model unable to fully solve the loadsharing redundancy in its absence, and forces at the elbow and glenohumeral joint and in other muscles were found to be profoundly increased. Its large number of fast-twitch muscle fibres, predisposed to atrophy with age, highlight the centrality of the serratus anterior as a key determinant of mobility in this critical task and a potential source of early immobility through its preferential loss of strength and thus point to the requirement for early clinical interventions to mitigate loss.

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• Journal article
  Ding Z, Güdel M, Smith S, Ademefun R, Bull AMJet al., 2019,

  Measuring Three-dimensional Knee Kinematics Using a Femoral Clamp: Accuracy, Repeatability and Reproducibility in Gait.

  , J Biomech Eng

  The ability to measure full six degrees-of-freedom knee joint kinematics is critical in the diagnosis of knee pathology. Soft tissue artifact (STA) remains the greatest source of error in measurement knee kinematics. The purpose of this study is to present a new femoral clamp to reduce STA at the thigh while preserving the natural gait pattern. Knee joint kinematics during gait was measured for six healthy subjects by using the femoral clamp and a rigid cluster-based technique. Performance was assessed in terms of accuracy, repeatability and reproducibility. The result showed that the femoral clamp did not change the walking speed and the natural knee kinematics pattern of the subjects. The clamp-measured kinematics had smaller knee translation in the transverse plane and were closer to data from the literature obtained by dual fluoroscopic imaging. The clamp had improved repeatability and reproducibility compared to the rigid cluster technique, suggesting that this technology is suitable for accurate measurement of gait.

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• Journal article
  Barnes SC, Clasper JC, Bull AMJ, Jeffers JRTet al., 2019,

  Micromotion and Push-Out Evaluation of an Additive Manufactured Implant for Above-the-Knee Amputees

  , JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 37, Pages: 2104-2111, ISSN: 0736-0266
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• Journal article
  Milwood Hargrave J, Pearce P, Mayhew E, Bull A, Taylor Set al., 2019,

  Blast injuries in children: a mixed-methods narrative review.

  , BMJ Paediatrics Open, Vol: 3, ISSN: 2399-9772

  Background and significance. Blast injuries arising from high explosive weaponry iscommon in conflict areas. While blast injury characteristics are well recognised in the adults,there is a lack of consensus as to whether these characteristics translate to the paediatricpopulation. Understanding blast injury patterns in this cohort is essential for providingappropriate provision of services and care for this vulnerable cohort.Methods. In this mixed-method review, original papers were screened for data pertaining topaediatric injuries following blasts. Information on demographics, morbidity and mortality andservice requirements were evaluated. The papers were written and published in English from a range of international specialists in the field. Patient and public involvementstatement: No patients or members of the public were involved in this review.Results. Children affected by blast injuries are predominantly male and their injuries arisefrom explosive remnants of war, particularly unexploded ordinance. Blasts show increasedmorbidity and mortality in younger children, while older children have injury patterns similarto adults. Head and burn injuries represent a significant cause of mortality in young children,while lower limb morbidity is reduced compared to adults. Children have a disproportionaterequirement for both operative and non-operative service resources, and provisions for thisburden are essential.Conclusions. Certain characteristics of paediatric injuries arising from blasts are distinctfrom that of the adult cohort, while the intensive demands on services highlights theimportance of understanding the diverse injury patterns in order to optimise future serviceprovisions in caring for this the child blast survivor.

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