Background: The hip joint is the largest joint after the knee, which gives stability to the whole human structure. The hip joint consists of a femoral head which articulates with the acetabulum.
Due to age and wear between the joints, these joints need to be replaced with implants which can function just as a natural joint. Since the early 19th century, the hip joint arthroplasty has evolved, and many advances have been taken in the field which improved the whole procedure. Currently, there is a wide variety of implants available varying in the length of stem, shapes, and sizes.
Material and Methods: In this analytical study of femur, circular, oval, ellipse and trapezoidal-shaped stem designs are considered in the present study. The human femur is modeled using Mimics. CATIA V-6 is used to model the implant models. Static structural analysis is carried out using ANSYS R-19 to evaluate the best implant design.
Results:All the four hip implants exhibited the von Mises stresses, lesser than its yielded strength. However, circular and trapezoidal-shaped stems have less von Mises stress compared to ellipse and oval.
Conclusion:This study shows the behavior of different implant designs when their cross-sections are varied. Further, these implants can be considered for dynamic analysis considering different gait cycles. By optimizing the implant design, life expectancy of the implant can be improved, which will avoid the revision of the hip implant in active adult patients.
Abstarct
Background
The Hip joint is the primary joint which gives stability to the human body. The wear and tear associated with age and other factors, require these joints to be replaced by implants using hip arthroplasty surgeries. Cobalt chromium alloy (CoCr), titanium alloy, stainless steel are some of the most common hip joint materials used for hip implants. The design requirement for hip joint implants are very stringent to avoid revision joint surgeries due to aseptic loosening. There are various choices in shapes and materials used for stem and acetabular designs. This makes it more difficult to make an informed decision on the type of design and material that can be used for hip implants.
Methods
Circular, Oval, ellipse and trapezoidal designs with three individual cross sections (defined as profile 1, profile 2 and profile 3) are considered for the study. All models are modeled using CATIA V-6. Static structural analysis is performed using ANSYS R-19 to arrive at the best possible design and material combination for stem and acetabular cup.
Results
It was found that, profile 2 of all the four designs has the lowest possible deformation and von Mises stress when compared to profile 1 and profile 2. In general, profile 2 with trapezoidal stem has best outcomes in terms of its mechanical properties. Besides, stem designed with material CoCr and its associated acetabular cup with CoC (ceramic on ceramic) material can produce an implant having better properties and longer durability.
Conclusions
CoCr was found to be the preferred choice of material for stem design. It was also observed that, irrespective of material considered for the analysis profile 2 with trapezoidal stem showcased lesser deformation and von Mises stress over the other eleven models. For analysis involving acetabular cups, CoC implants exhibited better mechanical properties over the conventional CoPE (Ceramic on polyethylene) materials such as Ultra-high molecular weight polyethylene (UHMWPE). It is inferred from the findings of this study that, the profile 2 with trapezoidal stem design made of CoCr material and acetabular cup made of CoC material is best suited for hip joint implants.
Background:The femur bone is an essential part of human activity, providing stability and support in carrying out our day to day activities. The inter-human anatomical variation and load bearing ability of humans of different heights will provide the necessary understanding of their functional ability.Objective:In this study, femur bone of two humans of different lengths (tall femur and short femur) were subjected to static structural loading conditions to evaluate their load-bearing abilities using Finite Element Analysis.Methods:The 3D models of femur bones were developed using MIMICS from the CT scans which were then subjected to static structural analysis by varying the load from 1000N to 8000N. The von Mises stress and deformation were captured to compare the performance of each of the femur bones.Results:The tall femur resulted in reduced Von-Mises stress and total deformation when compared to the short femur. However, the maximum principle stresses showed an increase with an increase in the bone length. In both the femurs, the maximum stresses were observed in the medullary region.Conclusion:When the applied load exceeds 10 times the body weight of the person, the tall femur model exceeded 134 MPa stress value. The short femur model failed at 9 times the body weight, indicating that the tall femur had higher load-bearing abilities.
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