SUMMARYAn enhanced discrete element method for the numerical modelling of particulate media is presented. This method models a particle of general shape by combining several smaller particles of simpler shape, such as a circle, into clusters that act as a single larger particle. The clusters more accurately model the geometrydependent behaviour of the particles, such as particle interlock and resistance to rolling. The method is implemented within the framework of an existing DEM program without the introduction of new contact or force algorithms. An extensive set of numerical &experiments' is performed which demonstrate the method's e!ectiveness. The granular media}structure interface shear test simulations are performed using both clustered and non-clustered particles. The results indicate that the clustered particles undergo less rolling and provide for increased shear resistance of the medium.

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Hip injuries are prevalent, especially within the athletic population. Of the hip injuries in this population, some 18-55% are lesions to the labrum of the hip. Clinical diagnosis of hip labral lesions is difficult because data on prevalence are varied. In addition, data on the prevalence of internal and external risk factors are absent as are data on the correlation of these risk factors with labral lesions, making it difficult to gauge the diagnostic utility. The mechanism of injury is often unknown or not specific to labral lesions. Internal risk factors may remain hidden to physical therapists because in most jurisdictions, ordering imaging tests is not within their scope of practice. Anterior inguinal pain seems highly sensitive for the diagnosis of patients with labral lesions but can hardly be considered specific; data on other pain-related and mechanical symptoms clearly have little diagnostic utility, making these data collected during the patient history almost irrelevant to diagnosis. By way of a comprehensive literature review and narrative and systematic analysis of the methodological quality of the retrieved diagnostic utility studies, this paper aimed to determine a diagnostic physical examination test or test cluster based on current best evidence for the diagnosis of hip labral lesions. Current best evidence indicates that a negative finding for the flexion-adduction-internal rotation test, the flexion-internal rotation test, the impingement provocation test, the flexion-adduction-axial compression test, the Fitzgerald test, or a combination of these tests provides the clinician with the greatest evidence-based confidence that a hip labral lesion is absent. Currently, research has produced no tests with sufficient specificity to help confidently rule in a diagnosis of hip labral lesion. Suggestions for future research are provided.

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