Influence of stem design parameters on periprosthetic femoral fractures examined by subject specific finite element analyses

• Published in: Medical engineering & physics Vol. 119; p. 104032
• Main Authors: Hennicke, N.S., Kluess, D., Sander, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2023
• Subjects: Finite element analysis; Hip stem design; Periprosthetic femoral fractures; Periprosthetic femoral fractures; Hip stem design; Finite element analysis
• ISSN: 1350-4533; 1873-4030; 1873-4030
• DOI: 10.1016/j.medengphy.2023.104032

•The development of periprosthetic femoral fractures is influenced by hip stem design parameters.•Friction at the implant-bone interface increases the fracture load and even higher fracture loads are possible for surfaces that allow or induce osseointegration.•An undersized implant reduces fracture load considerably due to the smaller cross-sectional area of the implant and the consequently missing initial stability.•A longer stem length leads to an increase of fracture load but shows signs of causing stress shielding and implant loosening after implantation.•Subject specific finite element analyses offer the possibility to compare different implant designs and choose the most suitable implant geometry the individual patient. Due to the increasing number of periprosthetic femoral fractures (PFF), the optimisation of implant design gains importance. For the presented research a validated, subject specific finite element model of a human femur with an inlying total hip stem was used to compare the influence of different geometrical implant parameters on the development of PFF. The heterogeneous bone tissue was modelled on the basis of computed tomography scans. A ductile damage model with element deletion was applied to simulate bone fracture in a load case re-enacting a stumbling scenario. The results were compared in terms of fracture load, subsidence and fracture pattern to analyse the influence of friction at the implant-bone interface, implant size and stem length. The results showed that higher friction coefficients lead to an increase of fracture load. Also, the usage of an oversized implant has a negligible effect while an undersized implant reduces the fracture load by 48.9% for the investigated femur. Lastly, a higher fracture load was reached with an elongated stem, but the bending and change in fracture path indicate a more distal force transmission and subsequent stress shielding in the proximal femur.