Stem Of Hip Prosthesis Research Articles

Design, fabrication, and clinical characterization of additively manufactured tantalum hip joint prosthesis

Abstract The joint prosthesis plays a vital role in the outcome of total hip arthroplasty. The key factors that determine the performance of joint prostheses are the materials used and the structural design of the prosthesis. This study aimed to fabricate a porous tantalum (Ta) hip prosthesis using selective laser melting (SLM) technology. The feasibility of SLM Ta use in hip prosthesis was verified by studying its chemical composition, metallographic structure, and mechanical properties. In vitro experiments proved that SLM Ta exhibited better biological activities in promoting osteogenesis and inhibiting inflammation than SLM Ti6Al4V. Then, the topological optimization design of the femoral stem of the SLM Ta hip prosthesis was carried out by finite element simulation, and the fatigue performance of the optimized prosthesis was tested to verify the biomechanical safety of the prosthesis. A porous Ta acetabulum cup was also designed and fabricated using SLM. Its mechanical properties were then studied. Finally, clinical trials were conducted to verify the clinical efficacy of the SLM Ta hip prosthesis. The porous structure could reduce the weight of the prosthesis and stress shielding and avoid bone resorption around the prosthesis. In addition, anti-infection drugs can also be loaded into the pores for infection treatment. The acetabular cup can be custom-designed based on the severity of bone loss on the acetabular side, and the integrated acetabular cup can repair the acetabular bone defect while achieving the function of the acetabular cup.

Material Removal of Hip Stem Prosthesis Using Bio-Inspiration from Trabecular Bone

In the hip stem prostheses domain, stress shielding represents a major issue due to its potential implant loosening effect. This phenomenon occurs when the implant is much stiffer than the bone itself. A way to reduce this stiffness difference is to remove material from the implant. In addition, this solution leads to mass reduction of the implant, improving the patient quality of life. To insure the implant will withstand the loading, material must be distributed in a specific way. Bones use the same objectives of lightness and mechanical efficiency while using a minimal amount of material. In addition, these biological structures are well spread and reliable in living beings, especially in mammals and avian species. In this paper, a method bio-inspired by trabecular bone structure is proposed to remove material from parts considering their mechanical stress field. In Nature, trabecular bone is defined as a graded porous material with bone material locally oriented along the local stresses’ direction. To mimic this natural behavior, the proposed method generates local porosities bio-inspired in position, shape, size and orientation. To evaluate the proposed method performance, experimental tests were carried out on a hip prosthesis stem. Test results demonstrated that the method can be used to reduce the stiffness of the prosthesis while withstanding the applied constrains.

Anterolateral Bone Window for Revision Broken Cemented Stem of Unipolar Hemiarthroplasty.

Background Fractured stem of the hip prosthesis is well documented in the literature. Although it is rare, it is considered as a challenging problem. Many techniques have been described to solve this problem. Purpose of the Study. Evaluation of the effect of anterolateral bone window for extraction of the cemented femoral stem of hemiarthroplasty in revision total hip replacement. Methods The study included eight revision hip arthroplasties in eight patients, with a broken stem of cemented (Thompson) hemiarthroplasty, which has been revised by the anterolateral proximal femoral window. All cases received cemented cups and cement-in-cement stems, except one case who received cementless long stem. Clinical follow-up of cases by Harries hip score (HHS) and X-ray. Results Functional improvement of HHS of all cases, with no signs of loosening, after a mean follow-up period of 1.5 years. Conclusion Extraction of broken stem is a challenging procedure. Many techniques have been described for revision of cases with a fractured stem of hip prosthesis, but we think that the anterolateral femoral bone window is a reproducible technique due to the characteristics of simplicity, short-time procedure, less invasive, not requiring extra instruments, and can be successful for most patients.

Bio-inspired redesign of a hip prosthesis stem for improving geometrical optimization time

It has been investigated the potential application of a bio-inspired 3D model for decreasing the time required to perform the geometrical optimization of a hip prosthesis stem. This research assumes that nature has already found the best solution for many situations, proved to be real for many cases, what has been demonstrated for the specific situation of a femur in this study. The application of bio-inspired 3D models can save up to a 35% of the time when geometrical optimizations are going to be performed.

Stability Loss of the Cemented Stem of Hip Prosthesis due to Fretting Corrosion Fatigue

Stability Loss of the Cemented Stem of Hip Prosthesis due to Fretting Corrosion Fatigue

Study on 4-axial precision milling of spatial freeform surface for individualized hip prosthesis stem

The fabrication of individualized hip prosthesis stem requires high machining freedom to dovetail precisely with the bond cavity of the patient. Hence, a 3-axial linkage motion is proposed in 4-axial milling along with a 1-axial differential drive and a cutter offset angle. Its advantage is to prevent from the accumulated errors of multi-axial motions. First, the centerline of spatial stem with the length of 200 mm was installed to a rotating axis; then, the transfer model of non-closed polar coordinate points was constructed to design 2D closed tool paths for the control of 3D cutting contact points; finally, the form error and the surface roughness of milled stem surface were investigated in connection with cutter posture angle. Theoretical analysis shows that the cutter offset angle contributes to an increase in cutter posture angle for high cutting velocity and the predication of the interference between cutter bar and workpiece. Experimental results show that the milled surface roughness and the milled form error are decreased by about 50 % and reach 0.26 and 126 μm when the cutter posture angle decreases to 20–40 °, respectively. It is confirmed that the 3-axial linkage milling along with 1-axial differential drive is likely to realize the precision machining of spatial hip prosthesis stem by controlling the cutter offset angle.

Mathematical computer modeling of biomechanical behaviour of hip endoprosthesis modified stem

The principles of mathematical modeling have been proposed in development and prognosing of biomechanical behavior of modified stem of hip prosthesis. We have made computer calculation of tensions and deformities of femoral component of metal stem and bone structures. We have defined critical disorders and wear of metal prosthesis with long groove and without groove. Mathematical calculations and the results confirm functional reliability and workability of the modified prosthesis.

Mesenchymal stem cells and platelet lysate in fibrin or collagen scaffold promote non‐cemented hip prosthesis integration

The objective of this study was to evaluate whether mesenchymal stem cells (MSC) and platelet lysate (PL) seeded in a fibrin or collagen scaffold could improve the new bone (NB) formation around an uncemented hip prosthesis stem in a sheep model. In vitro expanded MSC were suspended in PL and either mixed with collagen or fibrin gel as delivery vehicle. The cell-gel composites were inserted inside the femoral canal, then the prosthesis was press-fit inserted inside the femur. Identical procedures were performed in a control group, but only the prosthesis was implanted. Histomorphometrical analysis performed 4 months after surgery indicated that the newly formed bone inside the medullary canal, between the inner cortex and the prosthetic stem, was significantly higher in the MSC-PL-collagen group (mean 18.7 ± 4.5%) and in the MSC-PL-fibrin group (mean 18.8 ± 15.2%) when compared to the control group (mean 4.6 ± 2.0%). There was a significantly higher bone-prosthesis contact in the MSC-PL-collagen group (mean 2.7 ± 2.6%) and in the MSC-PL-fibrin group (mean 2.3 ± 3.1%) compared to the control group (mean 0.2 ± 0.1%). The results indicate that MSC and PL in a fibrin or collagen scaffold can promote NB formation around an uncemented hip prosthesis stem.

Analyses of Prosthesis Stem Failures in Noncemented Modular Hip Revision Prostheses

In recent years, hip prosthesis stem revision by means of modular revision systems has reached an essential role in revision prosthetics. It is an extremely successful technique. Reports about mechanical failure in nonmodular revision stems have already been published. This complication is rare, but feared. We report about mechanical failure of four non-cemented modular revision stems over a period of 28 months. All failures became clinically apparent because of severe inguinal or thigh pain and were confirmed by conventional x-ray imaging. All stem failures occurred just below the interface between prosthesis stem and neck, which is a biomechanically stressed area. Distal of the failure, all stems were still firmly fixed. In all cases, there was obvious evidence of loosening at the proximal component. Metallographic and energy-dispensive x-ray analysis of one stem showed a fatigue fracture due to dynamic stress. If new pain arises after revision surgery with modular non-cemented prosthesis systems, the possibility of an implant failure should be kept in mind. Patients should be informed accordingly about the risk of implant failure.

Computed Tomographic Metal Artifact Reduction for the Detection and Quantitation of Small Features Near Large Metallic Implants

Computed tomographic imaging of tissue surrounding metallic implants is often limited by metal artifacts. This paper compares 3 existing metal artifact reduction techniques that are based on segmentation of metal-affected regions in native images, followed by reprojection of segmented areas into original Radon space, removal of metal trace(s), and renewed reconstruction: Detector row-wise linear interpolation, 2-dimensional interpolation, and combination of row-wise linear interpolation and adaptive filtering. For each method, improvements of CT number accuracy and signal-noise as well as contrast-noise ratios near the prosthesis and in the image periphery over the values found for native images were evaluated in a phantom experiment simulating osteolytic bone lesions of different size and density around a Chrome-Cobalt hip prosthesis stem. Improvement in diagnostic usability was evaluated as lesion detectability by size. Quantitative and qualitative results showed that the linear interpolation and the combination method removed the artifacts most effectively. The mean accuracy error over different regions of interest placed in the direct vicinity of the metal and in the periphery of the object decreased 10-fold with linear interpolation. These methods increased contrast-noise ratio up to 68% of that measured on artifact-free images for the least dense lesion. Qualitatively, the linear interpolation and the combination method improved the lesion detectability and enabled differentiation of different lesion densities. However, in proximity to the stem, some artifacts remained for all methods. We conclude that published algorithms for metal artifact reduction substantially improve image quality for CT imaging of a metallic object and may be adequate for quantitative measurements except for the direct vicinity of the metallic object.

Spannungsanalyse einer anatomisch adaptierten Femurschaftprothese (Lubinus SPII)

Very good clinical long-term results of the Lubinus SP II hip prosthesis stem were reported in the literature. We therefore asked whether there is a relationship between these findings with biomechanical data of strain gauge measurements. 14 strain gauges were applied at a femur being measured at 10 different load cases before and after implantation of the stem. After stem implantation a similar patterns of principal stress distributions was observed, however, the magnitude was markedly reduced. A striking reduction of the hoop stresses at the femoral calcar was seen in the case of a missing collar contact. Even in the case of a perfect collar contact the hoop stresses were diminished after strem implantation. The S-shaped physiological stem did not correspond with a specific stress pattern measured at the femoral surface. These results suggest that the stresses at the femoral calcar may be lower than the limits of bone growth while the other parts of the femur are more physiologically stressed. However, the prosthesis may tolerate a missing collar contact during a long follow-up period. The large experimental data file presented here could be used to validate future finite element analyses which could evaluate the stress distribution within internal parts of the bone and the cement layer.

Fatigue failure analysis of a specific total hip prosthesis stem design

In an attempt to achieve initial stability and lack of motion at the cement stem interface, a specific design of the hip prosthesis femoral component was conceived. This design incorporated a specific geometrical feature in the prosthesis stem, namely a screw-like cross section profile. This feature was employed to avoid axial motion as well as stem subsidence into the cement mantle. Based on the numerical simulation results, this investigation reveals that the prosthesis unique design was not responsible for the stem loosening. Once the stem has been loosed, however, the concentration of stress at the geometrical feature root was sufficient to nucleate and propagate a fatigue crack, which eventually culminate in the femoral component catastrophic failure.

Eine Kniegelenkprothese mit femoralem Hülsenschaft zur Vermeidung einer interprothetischen Femurfraktur

Periprosthetic femoral fractures can be a difficult management problem. A certain risk factor occurs in long-stem component concerning biomechanical properties. Bending and torsional strength concentrate on short stem-free region of distal femur. In case of ipsilateral stem knee prosthesis the risk of fracture increase significantly. For prevention of an periprosthetic femoral fracture a total knee arthroplasty was done by using a prosthesis which can be connected rigidly with the hip prosthesis. A cemented femoral tube is put over the distal stem of hip prosthesis. The type of prosthesis, the operative procedure and outcome is presented by reviewed clinical cases.

F-0804 成長ひずみ法による人工股関節ステムの最適設計(S43-1 生体現象に対する計算力学的アプローチ)(S43 生体力学シミュレーション)

In order to restore damaged joint functions, prosthesis has been widely implanted into the joint part in recent years. However, the biononconformance often occurs after the reimplantation. In this paper, the shape optimization of a hip prosthesis stem in the total hip replacement was investigated using growth-strain method. At first, growth criterion parameters of femur were sought by applying finite element method for the mechanical adaptive growth behavior of femur. By this analysis, the effect of stress shielding on femur inserted with the prosthesis stem was investigated. Then, the optimum shape of the prosthesis stem was created by growing the stem not so as to be occurred the bone resorption on femur. It was found that the bone resorption of femur was the smallest when the stem area was at 80 % of the initial stem area.

231 アダプティブ p 法による人工股関節ステム形状最適化

Fatigue failure of the acrylic cement and resulting disruption of the bone-cement interface can limit the long-term clinical success of the cemented artificial hip joint. In order to overcome this problem optimal shape design prosthesis is required. This study describe a result of the design shape analysis (DSA) and the numerical shape optimization whereby the finite element method is used to determine optimal shape for the femoral stem of hip prosthesis in order to minimize the maximal value of the 1^<st> principal stress at the cement mantle.

Shape Optimization of a Hip Prosthesis Stem Using Growth-Strain Method.

Shape Optimization of a Hip Prosthesis Stem Using Growth-Strain Method.

Ultrasonic Measurement of Bone and Bone Marrow Thicknesses in Femur Covered with Flesh by Inserting a Hip Prosthesis Stem

The thicknesses of the bone and the bone marrow region within a pig femur covered with flesh are investigated nondestructively by inserting a hip prosthesis stem via an ultrasonic pulse echo method. An ultrasonic wave is emitted toward the hip prosthesis stem via a normal probe attached to the flesh, and the distances from the normal probe to the boundary surfaces of the bone and the metal stem are measured by observing the time intervals between each echo. Subsequently, the exact thicknesses of flesh, bone and bone marrow region are measured using vernier calipers. The results of the ultrasonic wave and vernier caliper measurements are graphically presented and compared. The ultrasonic method is found to be applicable for the proposed purpose.

Ultrasonic Measurement of Bone and Bone Marrow Thicknesses in Femur Covered wich Flesh by Inserting a Hip Prosthesis Stem.

The thicknesses of bone and bone marrow in a pig femur covered with flesh by inserting a hip prosthesis stem are investigated nondestructively by means of an ultrasonic pulse echo method. An ultrasonic wave is emitted toward the hip prosthesis stem via a normal probe attached to the flesh, and the distances from the normal probe to the boundary surfaces of bone and hip prosthesis stem are measured by observing the time intervals between each echo. Subsequently the actual thicknesses of flesh, bone and bone marrow are measured using vernier calipers. The results of the ultrasonic wave and vernier calipers measurements are graphically presented and compared. It is clarified that the ultrasonic method is useful for practical applications on the proposed problem.

Fracture of the femoral stem of the Ring TCH hip prosthesis

We report the clinical and operative details of seven cases of fracture of the femoral stem of the Ring TiMESH cementless hip prosthesis (two were cemented and five uncemented). Six fractures occurred in the proximal one-third of the stem and one at mid-stem. The failures are attributed mainly to two defects in stem design, the narrowness of the anteroposterior dimensions and the depth of the recess for the titanium mesh pads. Great difficulty was experienced in removing the osseo-integrated distal fragments of the broken stems.

The effects of hip prosthesis stem cross-sectional profile on the stresses induced in bone cement.

Bone cement has often been regarded as a weak link in a joint replacement structure. In spite of this, there has been little work published concerning experimental analysis of stresses in the cement. The purpose of the experiments described in this paper was to study the effects of some hip prosthesis stem designs on stresses in bone cement. The opportunity was also taken to examine some hypothetical designs. Photoelastic results show that some current designs of prosthesis stems cause less stress concentrations in cement than former designs. Stem designs which appeared good from photoelastic considerations also performed well in mechanical tests involving the impression of stem profiles in bone cement. A modification to current prosthesis stems is proposed which improves the ability of the cement to resist deformation.