Finite element studies of femoroacetabular impingement

  • Felix Lutz Hellwig

    Student thesis: Doctoral Thesis


    Recently, femoroacetabular impingement (FAI) was introduced as a pathomechanical concept that could explain idiopathic cartilage and labral degeneration. FAI can be subdivided into three mechanisms: 'Cam'- and 'pincer'-type impingement and the 'contracoupe' mechanism. The suggested concept aims to create a link between retrospective findings of cartilaginous tissue degeneration and mild abnormal structural deformations of the hip joint. The theoretical concept focuses on abnormal articulation rather than increased axial-overloading. Although clinical evidence seems to be given, prospective biomechanical verification would be desirable to provide further justification for early joint reconstruction surgery. A comprehensive research program has been carried out to highlight elevated stresses, contact pressures, affected fluid-load support, abnormal articulation and increased femoral head motion evoked by mild to severe abnormal conditions of the hip joint.
    Contact pressure, stress distributions and femoral head motion, indicating joint stability, were studied using three dimensional finite element models of normal and abnormal hip joint conditions; the considered abnormal conditions included a varying degree of acetabular and femoral version and manifestation of femoral protrusions (hump) at the femoral head-neck junction. The cartilogenous tissues were considered as linear elastic isotropic materials. The highlighted abnormal articulation confirmed the suggested concept of FAI; the predicted abnormal stress and contact pressure distribution corresponded to clinical findings.
    The fluid-load support, solid-on-solid stress, stress components, within the solid extracellular matrix of the cartilaginous tissues, and total contact pressure were studied during normal and isolated 'cam'-type impinged articulation. The cartilogenous tissues were considered as linear biphasic orthotropic materials. While the maximum total contact pressure, predicted during distinct 'cam'-type impingement, did not exceed the maxima obtained for normal articulation, the fluid-load support was severely affected at the zone of impingement. Vigorous elevated solid-on-solid stresses found at the zone of impingement, suggest a local increase in the coefficient of friction, which might lead to cartilage wear and progresses to severe osteoarthritis.
    Date of Award2013
    Original languageEnglish
    Awarding Institution
    • University of Portsmouth
    SupervisorJie Tong (Supervisor), J. G. Hussell (Supervisor) & Liguo G. Zhao (Supervisor)

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