THE EFFECT OF A CEMENTLESS STEM CROSS-SECTIONAL SHAPE ON MECHANICAL STABILITY: A FINITE ELEMENT ANALYSIS APPROACH

Abstract: The standard cementless femoral stems commercially available may not be the best-fit to a patient in markets like India, because of the large anatomic variation of the human hip joint among the population. This investigation presents a regional anthropometric data based design approach for the standard anatomical cementless femoral component used in total hip replacement (THR). Aseptic loosening and dislocation are the most important causes of failure of THR due to the mismatch in dimensions between the femur bone and stem. Standard cementless stems with different cross-section shapes were designed and analyzed to solve the problem of a possible geometric mismatch between a selected implant and the hip joint considering a variety of patients with differing anatomical sizes. Finite element analysis was conducted on cementless tapered stems with four different stem cross-sectional shapes - oval, trapezoidal, rectangular and wedge. Comparison of Von Mises stresses and micromotion under axial and torsional loads were made. This study indicates a need for a regional anthropometric data based design of cementless femoral stems for providing greater longevity and better recovery to patients. This novel design approach can improve the implant fixation enhancing primary stability, rigidity, longevity of the implant and relieving patients from discomfort.  

Keywords: Total hip replacement, cementless stem, mechanical stability, cross section.