PhD position: Modeling the dynamic behavior of implants used in total hip arthroplasty

Cementless implants are increasingly used in clinical practice. They are inserted in the host bone using impacts performed with an orthopaedic hammer (press-fit procedure). However, the rate of revision surgery is still high, which is a public health issue of major importance. The press-fit phenomenon occurring at implant insertion induces biomechanical effects in the bone tissues, which should ensure implant primary stability (that is, the stability of the implant during the surgery). Despite a routine clinical use, implant failures, which may have dramatic consequences, still occur and are difficult to anticipate. Just after surgery, the implant fixation relies on the pre-stressed state of bone tissue around the implant. In order to avoid aseptic loosening, a compromise must be found by the surgeon. On the one hand, sufficient primary stability can be ensured by minimizing micromotion at the bone-implant interface in order to promote osteointegration phenomena. On the other hand, excessive stresses in bone tissue around the implant must be avoided, as they may lead to bone necrosis or fractures. This raises a number of applied mathematical issues such as: – What is the appropriate mechanical model of the implant insertion process into the bone? – What are the suitable high-performance computing methods to accurately solve the above modelling equations for the bone-implant interaction subject to dynamic excitations? – Which robust inversion approaches can be employed to retrieve the quantities of interest of the bone-implant interaction such as the bone-implant contact area? During the PhD thesis, after a bibliographical review, the successful candidate will investigate possible dynamic models described by partial differential equations and their possible simplifications. Inversion aspects of the problem will be considered such as reconstruction of the material (bone) parameters and estimation of the stability characteristics of the implant. Anticipating the need for real-time performance, reduced-order modelling aspects should be studied. The funding of this PhD thesis is granted by the ANR project “MoDyBe” (Modeling the Dynamic Behavior of implants used in total hip arthroplasty), which also involves the Multiscale modeling and simulation laboratory (CNRS, Paris-Est Créteil University), together with clinical partners from the department of orthopaedic (Henri Mondor hospital). Required skills: General interest in applied mathematics and modelling in physics or life sciences, theoretical and practical experience with numerical methods for partial differential equations. Experience in continuum modelling, solution of inverse problems and model-order reduction techniques would be highly appreciated.

Last updated: 30 May 2025