Abstract
BackgroundStress shielding in the cemented hip prosthesis occurs due to the mismatching in the mechanical properties of metallic stem and bone. This mismatching in properties is considered as one of the main reasons for implant loosening. Therefore, a new stem material in orthopedic surgery is still required. In the present study, 3D finite element modeling is used for evaluating the artificial hip joint stem that is made of Function Graded (FG) material in terms of joint stress distributions and stem length.Method3D finite element models of different stems made of two types of FG materials and traditional stems made of Cobalt Chromium alloy (CoCrMo) and Titanium alloy (Ti) were developed using the ANSYS Code. The effects on the total artificial hip joint stresses (Shear stress and Von Mises stresses at bone cement, Von Mises stresses at bone and stem) due to using the proposed FG materials stems were investigated. The effects on the total artificial hip joint system stresses due to using different stem lengths were investigated.ResultsUsing FG stem (with low stiffness at stem distal end and high stiffness at its proximal end) resulted in a significant reduction in shear stress at the bone cement/stem interface. Also, the Von Mises stresses at the bone cement and stem decrease significantly when using FG material instead of CoCrMo and Ti alloy. The stresses’ distribution along the bone cement length when using FG material was found to be more uniform along the whole bone cement compared with other stem materials. These more uniform stresses will help in the reduction of the artificial hip joint loosening rate and improve its short and long term performance.ConclusionFE results showed that using FG stem increases the resultant stresses at the femur bone (reduces stress shielding) compared to metallic stem. The results showed that the stem length has significant effects on the resultant shear and Von Mises stresses at bone, stem and bone cement for all types of stem materials.
Highlights
It is well known that the fully understanding of stresses’ distribution in the hip joint is useful for both pre-operative planning and post operative rehabilitation
The stresses’ distribution along the bone cement length when using Function Graded (FG) material was found to be more uniform along the whole bone cement compared with other stem materials. These more uniform stresses will help in the reduction of the artificial hip joint loosening rate and improve its short and long term performance
The results showed that the stem length has significant effects on the resultant shear and Von Mises stresses at bone, stem and bone cement for all types of stem materials
Summary
It is well known that the fully understanding of stresses’ distribution in the hip joint is useful for both pre-operative planning and post operative rehabilitation. These non-uniform stresses’ distribution can cause the fixation to be altered as the bone density changes For these reasons, many experimental and analytical studies have been implemented to optimize the stresses distribution in total hip joint replacement through the modification of stem design parameters [12,13,14,15,16]. Many experimental and analytical studies have been implemented to optimize the stresses distribution in total hip joint replacement through the modification of stem design parameters [12,13,14,15,16] These results indicated that the bone cement material, stem shape and material have great effects on the total hip joint short and long term performance. 3D finite element modeling is used for evaluating the artificial hip joint stem that is made of Function Graded (FG) material in terms of joint stress distributions and stem length
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