Papers by Keyword: Femoral Head

Abstract: This work presents an experimental program to determine the mechanical properties of cancellous bone in the femoral head as a function of location. To achieve this several specimens of cancellous bone of approximately 10 mm height and 10 mm diameter were obtained from one human femoral head, starting the sampling from its main loading compressive direction. All specimens underwent compression testing in order to determine the mechanical properties of each specimen and thus a properties map of the cancellous bone in the femoral head was obtained. Based on the results a parametric file with material properties was created in order to be used by professionals in finite element analysis programs.

Abstract: A 3-dimensional hip joint implant model was constructed which separates into three individual parts namely femoral stem with neck, femoral head and acetabular cup. Each part were assigned with the specific materials and a total of 3000 N loads was applied to mimic the body weight of an adult in static position or in double leg standing position. The results of the stress distribution were obtained from the finite element analysis for the difference diameter for each component of ball-socket and neck as well as the difference materials. The results showed that an optimum diameter of femoral ball-socket with 36 mm and titanium alloy have design rigidity which provided better performance and longer life span based on 13.922 Mpa equivalent stress .

Abstract: In femoral head necrosis, the cortical shell of the femoral head collapses and buckles into the cancellous bone. The purpose of this study is to explore the biomechanical characteristics of the femoral head and the necrosis region by comparing the results before and after drug treatment. In this paper, we study two patient cases with femoral head necrosis disease and establish the corresponding computational three-dimensional models. The results show that the deformation of the femur decreases slightly after the treatment, the equivalent stress distributes more evenly, and the stress magnitude reduces. The results also reveal that the volume of the necrosis in the femoral head decreases after treatment, the overall necrosis presents relatively lower equivalent stress, and the area with the relatively high equivalent stress is smaller comparing to the necrosis in femoral head before treatment.

Abstract: In this paper, a new method for reconstructing the model of the necrotic femoral head is presented. It can reconstruct the optimal femoral head prosthesis model utilizing the reverse technology. This new method not only affords a theoretical model for the accurate operation position fixing in orthopaedic clinic, but also provides an innovative practical means for the individualized manufacturing of artificial femoral head prosthesis.The femoral head is regarded as a sphere. Then, the femoral head's configuration is reconstructed by means of fitting using the data points on the unspoiled acetabulum lunate surface. A spatial dynamic analysis is implemented, it is proved that the sphere fitting model can well satisfy the spatial motion relation between the femoral head and the acetabulum. The experiment results show that this method can well reconstruct the femoral head model of the target patient.

Abstract: In order to obtain the optimal model of femoral head prosthesis, a novel modeling method is proposed in this paper. It can revert the necrotic femoral head into the satisfactory model that primely matched with the acetabulum. This new method not only affords a theoretical model for the accurate operation position fixing in orthopaedic clinic, but also provides an innovative practical means for the individualized manufacturing of artificial femoral head prosthesis. Two male sufferers with different femoral head necrosis extent were chosen as the experimental subject for the prosthetic modeling simulation. The prosthetic models highly presented the primary shape of the femoral heads.

Abstract: Raman microprobe spectroscopy and atomic force microscopy (AFM) were systematically used to characterize the surface of an advanced alumina/zirconia composite (henceforth also referred to as zirconia toughened alumina, ZTA), in comparison with a commercially available femoral head made of monolithic zirconia. Experiments were conducted before and after in vitro exposure in water moist environment up to 100 h. Both materials contained zirconia partly stabilized with yttria. Tetragonal-to-monoclinic phase transformation, which was quantitatively characterized by confocal Raman spectroscopy as a function of grain size, showed significant difference between the investigated samples. Such difference was similarly found with respect to both roughness level and time needed for such topologic changes to occur. Variation of phase fractions and of topologic surface parameters were plotted as a function of in vitro exposure time and compared.

Abstract: In view of the imminent release on the Japanese market of hip prostheses made of an advanced alumina/zirconia, we performed morphologic and spectroscopic assessments of their surfaces with high spatial resolution. Femoral heads were characterized to a degree of statistical accuracy in the as-received state and after long-term exposures in vapor-moist environment. Surface and sub-surface screening was made by atomic force microscopy (AFM) and by confocal Raman spectroscopy, respectively. AFM scanning was systematically repeated with nanometer resolution on portions of surface as large as several tens of micrometers, randomly selected on the head surface, while in-depth scanning by the Raman probe allowed non-destructive analysis of phase structure in the sub-surface slab of material. Polymorphic transformation in zirconia was confined to the first few micrometers below the surface and involved no significant increase in surface roughness even after long-term environmental exposure. Surface roughness lied in a range <10 nm after environmental exposures up to 100 h, corresponding to an exposure time in vivo of several human lifetimes (i.e., according to experimentally derived thermal activation energy).

Abstract: This paper presents a stress analysis of the ceramic femoral heads of hip joint prostheses with different borehole shapes to evaluate their mechanical reliability in terms of stress concentration. Under the ideal loading conditions used for ceramic rupture tests specified by the ISO 7206-5 standard, a finite element (FE) modeling is performed to determine the tensile and hoop stress distributions in the ceramic femoral heads. Two borehole shapes that are currently used in the manufacturing industry for hip joint prostheses, namely the flat bottom and keyhole, were first studied. Two new borehole shapes, dome arc and dome ellipse, were then introduced by the authors in the paper to minimize the stress concentration. It was found that while the currently used borehole shapes lead to high tensile notch stresses at their critical corners causing possible fracture failure of ceramic heads, the authors’ borehole designs can improve the mechanical reliability significantly. In addition, the effects of taper-bore contact length and their interface friction are investigated and discussed.

Abstract: Hip hemiarthroplasty is a popular method for curing hip joint diseases. Comparing with the total hip replacement (THR), hip hemiarthroplasty has some advantages, such as simpler operation, lower cost and less injury. However, inevitable acetabular cartilage wear, which leads to ultimately conversion to THR, has been reported by many authors. That limits its applications. To solve this problem, more suitable biomaterial should be chosen to make the femoral head. In this research, a kind of carbon femoral head, which was made of graphite coated with low temperature isotropic pyrolytic carbon, was studied in vivo. Nineteen New Zealand adult white rabbits were divided into 3 groups. Every rabbit was taken the replacement operation and time-dependently killed after certain periods. X-ray photographs of the hip joint, macroscopic apperarance and histological morphometry of the neocartilage around the prosthesis, were examined. The results proved that the coating material of the femoral head was biocompatible and the neocartilage tissue around the prothetic head might protect the acetabulum from wear. However, because of the complicated physiological environment, further research is needed.

Abstract: The fracture is an important failure behavior of cancellous bone. Three-point-bending experiment was used to study fracture behavior of cancellous bone. Three group specimens were taken from two human femoral head and there was a non-angled crack and an angled crack in every group respectively. By using Digital Speckle Correlation Method (DSCM), the displacement and strain field were obtained at the crack-tip and the full specimen. The initial crack path was always at the maximal strain location and could be predicted by the DSCM. In the macro-scope, the crack propagation paths towards the load tip, and are independent of the initial crack angle.