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• Journal article
  Majed A, Thangarajah T, Southgate DFL, Reilly P, Bull A, Emery Ret al., 2019,

  The biomechanics of proximal humeral fractures: Injury mechanism and cortical morphology

  , Shoulder & Elbow, Vol: 11, Pages: 247-255, ISSN: 1758-5732

  BackgroundThe aim of this study was to examine the effect of arm position on proximal humerus fracture configuration and to determine whether cortical thinning would predispose to fracture propagation and more complex patterns of injury.MethodsA drop test rig was designed to simulate falls onto an outstretched arm (‘parachute reflex’). Thirty-one cadaveric specimens underwent computer tomography scanning and cortical thicknesses mapping. Humeri were fractured according to one of the two injury mechanisms and filmed using a high-speed camera. Anatomical descriptions of the injuries were made. Areas of thinning were measured and correlated with zones of fracture propagation.ResultsDirect impact simulation resulted in undisplaced humeral head split fractures in 53% of cases, with the remainder involving disruption to the articular margin and valgus impaction. Alternatively, the ‘parachute reflex’ predominantly produced shield-type injuries (38%) and displaced greater tuberosity fractures (19%). A strong correlation was demonstrated between cortical thinning and the occurrence of fracture (odds ratio = 7.766, 95% confidence interval from 4.760 to 12.669, p<0.0001).ConclusionThis study has shown that arm position during a fall influences fracture configuration of the proximal humerus. Correlating fracture pattern and mechanism of injury will allow more appropriate fracture reduction techniques to be devised.

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• Journal article
  Ahmadzadeh SMH, Chen X, Hagemann H, Tang M-X, Bull AMJet al., 2019,

  Developing and using fast shear wave elastography to quantify physiologically-relevant tendon forces

  , Medical Engineering and Physics, Vol: 69, Pages: 116-122, ISSN: 1350-4533

  Direct quantification of physiologically-relevant tendon forces can be used in a wide range of clinical applications. However, tendon forces have usually been estimated either indirectly by computational models or invasively using force transducers, and direct non-invasive measurement of forces remains a big challenge. The aim of this study was to investigate the feasibility of using Shear Wave Elastography (SWE) for quantifying human tendon forces at physiological levels. An experimental protocol was developed to measure Shear Wave Speed (SWS) and tensile force in a human patellar tendon using SWE and conventional tensile testing to quantify the correlation between SWS and load. The SWE system was customised to allow imaging of fast shear waves expected in human tendons under physiological loading which is outside the normal range of the existing SWE systems. SWS increased from 10.8 m/s to 36.1 m/s with the increasing tensile load from 8 N to 935 N and a strong linear correlation between SWS and load (r = 0.99, p < 0.01) was observed. The findings in this study suggest that SWE can be used as a potential non-invasive method for direct quantification of physiologically-relevant tendon forces, as well as for validating the estimated forces from other methods such as computational models.

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• Journal article
  Berthaume MA, Di Federico E, Bull AMJ, 2019,

  Fabella prevalence rate increases over 150 years, and rates of other sesamoid bones remain constant: a systematic review

  , Journal of Anatomy, Vol: 235, Pages: 67-79, ISSN: 1469-7580

  The fabella is a sesamoid bone located behind the lateral femoral condyle. It is common in non-human mammals, but the prevalence rates in humans vary from 3 to 87%. Here, we calculate the prevalence of the fabella in a Korean population and investigate possible temporal shifts in prevalence rate. A total of 52.83% of our individuals and 44.34% of our knees had fabellae detectable by computed tomography scanning. Men and women were equally likely to have a fabella, and bilateral cases (67.86%) were more common than unilateral ones (32.14%). Fabella presence was not correlated with height or age, although our sample did not include skeletally immature individuals. Our systematic review yielded 58 studies on fabella prevalence rate from 1875-2018 which met our inclusion criteria, one of which was an outlier. Intriguingly, a Bayesian mixed effects generalized linear model revealed a temporal shift in prevalence rates, with the median prevalence rate in 2000 (31.00%) being ~ 3.5 times higher than that in 1900 (7.64%). In all four countries with studies before and after 1960, higher rates were always found after 1960. Using data from two other systematic reviews, we found no increase in prevalence rates of 10 other sesamoid bones in the human body, indicating that the increase in fabella prevalence rate is unique. Fabella presence/absence is due to a combination of genetic and environmental factors: as the prevalence rates of other sesamoid bones have not changed in the last 100 years, we postulate the increase in fabella prevalence rate is due to an environmental factor. Namely, the global increase in human height and weight (due to improved nutrition) may have increased human tibial length and muscle mass. Increases in tibial length could lead to a larger moment arm acting on the knee and on the tendons crossing it. Coupled with the increased force from a larger gastrocnemius, this could produce the mechanical stimuli necessary to initiate fabella formation an

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• Journal article
  Sivapuratharasu B, Bull AMJ, McGregor AH, 2019,

  Understanding low back pain in traumatic lower limb amputees: a systematic review

  , Archives of Rehabilitation Research and Clinical Translation, Vol: 1, ISSN: 2590-1095

  Objective: This systematic review aims to evaluate current literature for the prevalence, causes and effect of low back pain (LBP) in traumatic lower limb amputees, specifically its association with the kinematics and kinetics of the lumbar spine and lower extremities. Data Sources: Databases (EMBASE, MEDLINE, Scopus, CINAHL, and PsycINFO) were searched systematically for eligible studies from inception to January 2018. Study Selection: The inclusion terms were synonyms of ‘low back pain’, ‘lower limb amputation’, and ‘trauma’, whilst studies involving non-traumatic amputee populations, single cases or reviews were excluded. 1822 studies were initially identified, of which 44 progressed to full-text reading, and 11 studies were included in the review.Data Extraction: Two independent reviewers reviewed the included studies, which were evaluated using a quality assessment tool and the GRADE system for risk of bias, prior to analysing results and conclusions. Data Synthesis: There was a LBP prevalence of 52–64% in traumatic amputees, compared to the 48–77% in the general amputee population (predominantly vascular, tumour and trauma), attributed to a mixture of biomechanical, psycho-social and personal factors. These factors determined the presence, frequency and severity of the pain in the amputees, significantly impacting on their quality of life. However, little evidence was available on causality. Conclusion: The high prevalence of LBP in traumatic amputees highlights the necessity to advance research into the underlying mechanics behind LBP, specifically the spinal kinematics and kinetics. This may facilitate improvements in rehabilitation, with the potential to improve quality of life in traumatic amputees.

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• Journal article
  Thompson SM, Prinold JAI, Hill AM, Reilly P, Emery RJH, Bull AMJet al., 2019,

  The influence of full-thickness supraspinatus tears on abduction moments: the importance of the central tendon

  , Shoulder and Elbow, Vol: 11, Pages: 19-25, ISSN: 1758-5740

  Background: Detachment of the central tendon of the supraspinatus from its insertion is considered to be crucial to functional deficit. The aim of the present study was to assess the function of the supraspinatus in terms of abduction moments by introducing different tear configurations to assess the functional effect of the central tendon insertion. Methods: Ten fresh frozen shoulders from five cadavers were prepared for testing. A testing protocol was established to measure the abduction moment of the supraspinatus under physiological loading tailored to the anthropometrics of each specimen. Four conditions were tested: intact supraspinatus; complete detachment of portion of the supraspinatus tendon anterior to the main central tendon; detachment of the main central tendon; and detachment of the region of the supraspinatus posterior to the main central tendon. Results: There was a significant and large reduction in abduction moment when the central tendon was sectioned (p < 0.05). A smaller reduction in abduction moment was found when the regions anterior and posterior to the main central tendon were sectioned (p < 0.05). Conclusions: The central tendon is vital in the role of functional arm abduction through force transmission through the intact rotator cuff. Reinsertion of the central tendon in the correct anatomical location is desirable to optimize functional outcome of surgery.

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• Journal article
  Nolte D, Bull AMJ, 2019,

  Femur finite element model instantiation from partial anatomies using statistical shape and appearance models

  , Medical Engineering and Physics, Vol: 67, Pages: 55-65, ISSN: 1350-4533

  Accurate models of bone shapes are essential for orthopaedic reconstructions. The commonly used methods of using the contralateral side requires an intact bone and anatomical symmetry. Recent studies have shown that statistical shape and appearance models (SSAMs) as an alternative can predict accurate geometric models, but the accuracy of the mechanical property prediction is typically not addressed. This study compares stress and strain differences under identical loading conditions for reconstructions from partial anatomies.SSAMs representing shape and grey values were created using 40 female cadaveric X-ray computed tomography scans. Finite element models were created for shape reconstructions from partial bone of various lengths with boundary conditions obtained from musculoskeletal simulations. Commonly used anatomical measures, measures of the surface deviations and maximal stresses and strains were used to compare the reconstruction accuracy to the contralateral side.Surface errors were smaller compared to the contralateral side for reconstructions with 90% of the bone and slightly bigger when less bone was available. Anatomical measures were comparable. The contralateral side showed slightly smaller relative errors for strains of up to 6% on average.This study has shown that SSAM reconstructions using partial bone geometry are a possible alternative to the contralateral side.

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• Journal article
  Klemt C, Nolte D, Ding Z, Rane L, Quest RA, Finnegan ME, Walker M, Reilly P, Bull Aet al., 2019,

  Anthropometric scaling of anatomical datasets for subject-specific musculoskeletal modelling of the shoulder

  , Annals of Biomedical Engineering, Vol: 47, Pages: 924-936, ISSN: 0090-6964

  Linear scaling of generic shoulder models leads to substantial errors in model predictions. Customisation of shoulder modelling through magnetic resonance imaging (MRI) improves modelling outcomes, but model development is time and technology intensive. This study aims to validate 10 MRI-based shoulder models, identify the best combinations of anthropometric parameters for model scaling, and quantify the improvement in model predictions of glenohumeral loading through anthropometric scaling from this anatomical atlas. The shoulder anatomy was modelled using a validated musculoskeletal model (UKNSM). Ten subject-specific models were developed through manual digitisation of model parameters from high-resolution MRI. Kinematic data of 16 functional daily activities were collected using a 10-camera optical motion capture system. Subject-specific model predictions were validated with measured muscle activations. The MRI-based shoulder models show good agreement with measured muscle activations. A tenfold cross-validation using the validated personalised shoulder models demonstrates that linear scaling of anthropometric datasets with the most similar ratio of body height to shoulder width and from the same gender (p < 0.04) yields best modelling outcomes in glenohumeral loading. The improvement in model reliability is significant (p < 0.02) when compared to the linearly scaled-generic UKNSM. This study may facilitate the clinical application of musculoskeletal shoulder modelling to aid surgical decision-making.

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• Journal article
  Majed A, Thangarajah T, Southgate D, Reilly P, Bull A, Emery Ret al., 2019,

  Cortical thickness analysis of the proximal humerus.

  , Shoulder Elbow, Vol: 11, Pages: 87-93, ISSN: 1758-5732

  BACKGROUND: Structural changes within the proximal humerus influence the mechanical properties of the entire bone and predispose to low-energy fractures with complex patterns. The aim of the present study was to measure the cortical thickness in different regions of the proximal humerus. METHODS: Thirty-seven proximal humeri were analyzed using novel engineering software to determine cortical thickness in 10 distinct anatomical zones. RESULTS: The cortical thickness values ranged from 0.33 mm to 3.5 mm. Fifteen specimens demonstrated a consistent pattern of progressive cortical thinning that increased between the bicipital groove (thickest), the lesser tuberosity and the greater tuberosity (thinnest). Fifteen humeri were characterized by a progressive increase in cortical thickness between the greater tuberosity (thinnest), the bicipital groove and lesser tuberosity (thickest). The diaphysis exhibited the thickest cortical zone in 27 specimens, whereas the articular surface possessed the thinnest cortex in 18 cases. CONCLUSIONS: In conclusion, this is the first study to comprehensively assess cortical thickness of the humeral head. Our findings suggest that proximal humeral fractures occur along lines of cortical thinning and are displaced by the hard glenoid bone. The identification of specific areas of thick cortices may improve pre-operative planning and optimize fracture fixation.

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• Journal article
  Rane L, Ding Z, McGregor AH, Bull AMJet al., 2019,

  Deep learning for musculoskeletal force prediction

  , Annals of Biomedical Engineering, Vol: 47, Pages: 778-789, ISSN: 0090-6964

  Musculoskeletal models permit the determination of internal forces acting during dynamic movement, which is clinically useful, but traditional methods may suffer from slowness and a need for extensive input data. Recently, there has been interest in the use of supervised learning to build approximate models for computationally demanding processes, with benefits in speed and flexibility. Here, we use a deep neural network to learn the mapping from movement space to muscle space. Trained on a set of kinematic, kinetic and electromyographic measurements from 156 subjects during gait, the network’s predictions of internal force magnitudes show good concordance with those derived by musculoskeletal modelling. In a separate set of experiments, training on data from the most widely known benchmarks of modelling performance, the international Grand Challenge competitions, generates predictions that better those of the winning submissions in four of the six competitions. Computational speedup facilitates incorporation into a lab-based system permitting real-time estimation of forces, and interrogation of the trained neural networks provides novel insights into population-level relationships between kinematic and kinetic factors.

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• Journal article
  Xu R, Ming D, Ding Z, Bull AMJet al., 2019,

  Extra Excitation of Biceps Femoris during NMES Reduces Knee Medial Loading

  , Royal Society Open Science, Vol: 6, ISSN: 2054-5703

  Experimental data.

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