Papers by Keyword: Total Hip Arthroplasty

Abstract: This study aims to address these challenges by evaluating the displacement and interfacial damage of acetabular components with auxetic inner structures under cyclic loading conditions. Aseptic loosening of the acetabular cup is one of the primary causes of implant failure in hip replacements. However, assessing the damage behavior of implants in vivo remains a significant challenge, particularly when evaluating implant displacement and interfacial damage. A cantilever device for displacement measurements was designed and calibrated using a laser displacement sensor. The cantilever device successfully measured the displacement of the acetabular cup by monotonic and cyclic loading up to-2.3kN. Both AE sensors and cantilever devices could measure the increasing displacement in both the rotational and embedding directions. Finally, the loosening mechanism of the acetabular cup with an auxetic texture was discussed.

Abstract: Ti-6Al-7Nb is commonly used as orthopedic implant, especially for total hip arthroplasty application, due to its excellency in biocompatibility and surface feature. This study investigates the effects of varying solution treatment temperatures on the mechanical properties and corrosion resistance of the biomedical Ti-6Al-7Nb alloy fabricated using centrifugal investment casting. Solution treatment was performed at 850°C, 970°C, and 1050°C, and the results were evaluated through tensile tests, hardness measurements, microstructural observations, and potentiodynamic polarization tests. The treatment at 970°C produced the optimal combination of mechanical strength and corrosion resistance, achieving a tensile strength of 690 MPa and the lowest corrosion rate of 0.00826 mmpy. The superior performance at 970°C is attributed to the formation of fine α precipitates in the microstructure. These findings highlight the effectiveness of suitable solution treatment temperature in enhancing Ti-6Al-7Nb’s properties for potential use in biomedical applications.

Abstract: The impact of bone variables, including density, geometry, angle of femoral torsion, and thickness of the femoral cortices, on the formation of bone micro-damage following THA was investigated. Using CT images of avascular necrosis patients, we developed 28 intact femoral bone models with ages ranging from 19 to 87 years to explore the relationship between age and bone density. Among these 28 femur models, 10 models were selected for implantation with the Zweymuller stem, divided into two groups based on the highest and lowest bone mineral density (BMD). After proper stem insertion into the femoral bone canal, finite element analyses with nonlinear damage analysis were performed on the THA models under three boundary conditions: stance, lateral bending, and torsion. Using the Pearson’s correlation coefficient, the study revealed a strong correlation between bone density and fracture load in the 10 THA models, which remained consistent across all three boundary conditions: stance (r = 0.74), lateral bending (r = 0.79), and torsion (r = 0.88). However, a moderate correlation was observed between bone density and the number of solid element failures, which also remained consistent across all boundary conditions: stance (r = -0.40), lateral bending (r = -0.51), and torsion (r = -0.48). It was found that femoral models with a bent shape of the femoral shaft and thin cortices experienced greater bone damage compared to models with normal geometry. Additionally, THA models with retroversion stem placement resulted in higher bone damage compared to models with normal anteversion placement.

Abstract: The aim of the present investigation is to determine the ideal values for several parameters, such as the external diameter of the polyethylene liner, the Young's modulus of the cup, and the friction coefficients between the polyethylene liner's contact area and the acetabular shell and prosthetic head of the dual-mobility cup. Reduced stresses at the bone/cement interface are crucial for ensuring a well-fixed dual-mobility cup (DMC) with the acetabulum because orthopedic cement (PMMA) is the weakest component of total hip arthroplasty (THA). Four factors, such as the PE liner size, the rigidity of the cup, and the friction coefficients, are optimized using the three-dimensional finite element method (FEM) and experimental design approach (EDA). The numerical results show that the hemispherical-liner size, mechanical characteristics of the cup, surface state of the femoral head, liner PE, and shell components all influence the mechanical strength of the bone cement. To prevent fracturing the bone cement, which would render the total hip arthroplasty ineffective. The optimal values of the maximum von Mises stress in bone cement will be determined using this methodology. The numerical outcome shows that when the Young's modulus of the cup rises, the maximum stress in bone cement falls until it reaches a minimal value. The maximum stress in bone cement, however, increases as the PE liner's exterior diameter increases. Because the maximum stress is still below the yield stress of bone cement, the artificial hip joint is still considered safe despite the increased stress value.

Abstract: In this report, the middle-term clinical and radiographic results were investigated in total hip arthroplasty (THA) cases using PMMA bone cement and hydroxyapatite (HA) granules (modified interfacial bioactive bone cement technique; M-IBBC). 76 hip joins (69 cases) were operated between June 2010 and September 2012, and followed. The minimum follow-up period was 4.5 years, the average follow-up was 5.5 years and average age at operation was 67.4 years. Revision was not performed. Average Japanese orthopaedic association (JOA) score improved from 45 to 88. Socket loosening was not observed radiographically. X-p findings of sockets demonstrated radiolucent line in the outer part of Zone 1 (designated Zone 1a in this report) in 1.3% immediately after the operation, and 6.6% at 1 year postoperatively. After 2 years progressive changes were not observed. The improvement of radiolucent line was observed in two cases at 3 years postoperatively and radiolucent line in Zone 1a was observed in 3.9%. These findings suggested that osteoconductivity of HA granules was maintained after the operation.

Abstract: The necessity of coatings for endoprosthetic implants is discussed controversially. Thereby hydroxyapatite coatings are objects of the debate [1, 2]. Therefore, we investigated four different coatings (calcium-phosphate (CaP), titanium-calcium-phosphate (TiCaP), titanium-plasma-spray (TPS) and bilayer-composite calcium-phosphate (CaP-bc)) in comparison with rough uncoated test specimens to evaluate the impact of the osteoconductive coatings on the initial implant stability which is the key factor for its secondary stability. Dimensions of the test specimens were defined according to a conventional total hip stem and their geometry was simplified to a conical one for comparison of the surface-related parameters. The specimens were force-controlled pressed in artificial bone counterparts made of foam material while the displacement was monitored by the test machine to determine the subsidence behavior. Consecutively a displacement-controlled axial extraction of the test specimens was performed and the pull-out force was recorded. Roughness and geometry of the test specimens before testing were measured and correlated to type of coating and initial stability. The uncoated specimens showed highest extraction forces (3.9 kN) with moderate surface roughness compared to the coated specimens. In contrary to our assumption no correlation between surface roughness and the measured subsidence as well as pull-out force was found and a reduced subsidence or increased pull-out force for the different titanium and calcium-phosphate coatings could not be derived from the experimental tests.

Abstract: The middle-term clinical and radiographic results were investigated in total hip arthroplasty (THA) cases using bone cement and hydroxyapatite (HA) granules (the interfacial bioactive bone cement technique; IBBC). 42 hip joins (39 cases) were operated between October 2005 and July 2007, and followed. The minimum follow-up was 6 years, average follow-up period was 7.0 years and average age at operation was 67 years. One revision was performed due to late infection. Average Japanese orthopaedic association (JOA) score improved from 48 to 87. Socket loosening was not observed radiographically. X-p findings of sockets demonstrated radiolucent line in the outer part of Zone 1 in 12% immediately after the operation, 24% at 2 years postoperatively. After 2 years there was no progressive change, however, improvement of radiolucent line (gap filling) with bone remodeling was observed in three cases after 3 years postoperatively.

Abstract: Total hip arthroplasty (THA) is a routine procedure for the treatment of advanced hip joint damage. The long-term result of the prosthesis is mainly determined by migration or aseptic loosening caused by bone remodelling. Especially the migration of the artificial hip cup as a consequence of the remodelling process is a major problem. Patient-specific hip cups can be used to counteract this. However, individual hip cups are currently only implanted for the treatment of great deformations or tumours in the hip joint due to the cost-intensive manufacturing. The aim of this project is the development and establishment of a concept for the economical production of patient-individual prosthetic hip cups out of titanium sheets. This process consists of two steps. First, undersized cups of a universal acetabulum geometry are produced. In the second step a true-to-size enlargement of the produced universal cup prothesis is carried out by means of a modified adaptive rubber-die forming process. The development of this process is accompanied by a simulationbased planning of the production process as well as by a realization of a metal forming adapted design method. For the examination of the feasibility of the concept, CT-data of canine pelvis geoemtries are used because of the large number of CT data, which were aviable for the project. Furthermore it is planned, that the first manufactured prototypes will be tested using canine cadaver. In this study the planning of the manufacturing of the standardized titanium sheet metal components is carried out. For this two methods of producing the standardized hip cup were compared. The first method is a hydraulic forming; the second is a normal pressing process with a bunch die and a binder. Pure titanium was introduced in the simulation, which shows the same mechnical properties like the in prosthetics normally used titanium alloy TiAl6V5. The results of the process simulation of both methods showed that the reducing of the blank thickness is a problem of the manufacturing of the prosthesis. Because of that an adaption of the tool geometry was executed and the influence of the increase of the forming temperature at 200 C was examined. These simulations indicated, that the hydraulic forming seems to be a convenient method to produce the prosthetic acetabulum. The first part of the metal forming adapted design method is the deduction of a universal acetabulum geometry, which has to be designed for the production of the standardized component. This deduction shall be realized by means of a superposition of 3D models of pelvis geometries. For this, two different superposition methods were compared and the Best Fit method was determined as the suitable method. By means of the Best fit method a first universal geometry was created.

Abstract: Objective Three-dimensional finite element analysis was employed to select femoral prostheses according to different bone densities, and simultaneously simulated contrast mechanical tests were performed to determine the age criteria regarding the selection of femoral prosthesis during the hip replacement. Methods Three-dimensional finite element models of femur were established using Solidworks software. Following the known formula, the bone density and elastic modulus at different age brackets were calculated and input into the computer. The human one-foot standing condition was simulated and pressure was loaded on the reconstructed femoral models. Some iomechanical characteristics of un-cemented and cemented femoral prostheses, such as the distress distribution and initial micro-movement at different bone densities, were measured. Results Relatively well-distributed whole distress and slight initial micro-movement of un-cemented femoral prostheses were found in male patients at 30-60 years old and in female patients at 40-55 years old. Symptoms of cemented femoral prostheses the same as the un-cemented femoral prostheses were present in male patients at 60-70 years and in female patients older than 55 years old. Conclusion Results of three-dimensional finite element analysis and simulated contrast mechanical tests suggest that un-cemented femoral prostheses provide better therapeutic effects in male patients younger than 60 years and in female patients

Abstract: Objective To explore the relationship between acetabular cup position and the load distribution within the acetabulum and to confirm an optimal range of cup position, thereby providing a theoretical criterion from a biomechanical aspect for proper cup implantation in clinical work. Methods A male adult cadaveric pelvic was scanned with spiral CT, and then the two-dimensional images were evaluated using GE medical systems software and the outline of the pelvis was identified by the edge detective estimation. Pelvic coordinate data were put into the computer to build up a three-dimensional (3D) finite element model of the pelvic using Solidworks software . A φ48 non-cemented cup from Tianjin Huabei Medical Instrument Factory was used, and the 3D measurement of the cup was carried out by CLY single-arm 3D measurement apparatus, which was made in Testing Technology Institute of China. The measurement data were transferred into computer. Through the CAD Sliod Works 2010 software, the 3D model of the cup was automatically reconstructed. After wards, one-foot standing position was simulated to conduct the loading and constraint of the model, the Mises and shear force distributing of the cup were analyzed, forecasting the mechanical risk of prosthetic failure. Results In the 3D finite element model of human pelvis, the number of total nodes was 103043 and the number of total elements was 69271. Abduction angle did not affect the Mises and shear force distributions between the range of 40°-50°(P>0.05). However, significant affects appeared in Mises and shear force once the abduction angle was < 35° or > 50°. The change of the cup anteversion within5°-30°would not affect the Mises and shear forces in the acetabulum (P > 0.05). Conclusion A uniform load distribution on the cup-bone interface can be obtained when the cup abduction angle is from 40°to 50°. The change of the cup anteversion angle can not affect the load distribution in the acetabulum, therefore the cup abduction range of 40°-50°can be confirmed as the safe range for cup implantation.