Artificial Hip Prosthesis Research Articles

Orthopedic Spinal and Hip Prostheses: Effects of Magnetic Susceptibility Artifacts during MR Arteriography and Venography of Abdomen and Pelvis

To retrospectively determine if susceptibility artifacts from internal metallic spinal fixation devices and hip prostheses limit the depiction of vascular anatomy and pathologic abnormalities during magnetic resonance (MR) arteriography and venography. This study was approved by the Committee on Human Research of the Institutional Review Board, which waived the requirement for informed consent and deemed the study to be HIPAA compliant. Forty-two contrast material-enhanced MR angiographic examinations were performed by using a 1.5-T imager in 41 patients (16 men, 25 women; mean age, 57 years; range, 36-79 years); 33 of these examinations included both MR arteriographic and MR venographic components. On the basis of resolution, images for which more than 3 mm of vessels were affected by susceptibility artifacts were considered uninterpretable. The odds of obtaining an uninterpretable image due to metallic artifacts were calculated, and a chi(2) analysis was employed to determine significance. Total hip prostheses and spinal hardware that terminated above the L5 level did not generate any appreciable artifacts at MR arteriography (P < .001) or MR venography (P = .002). In patients with hardware that extended to the sacrum, 88% of MR arteriograms were of diagnostic quality (P = .001), but only 21% of MR venograms were interpretable (P = .004). Artifacts limited the evaluation of the inferior vena cava and common iliac veins near the confluence. Diagnostic-quality MR arteriograms and MR venograms can be obtained in patients with artificial hip prostheses and spinal hardware terminating above the L5 level, but there is 79% likelihood of obtaining a nondiagnostic MR venogram in patients with internal spinal fixation devices that extend to the sacrum.

The Characteristics of the New Ceramic Material for Artificial Joints

A new zirconia-toughened alumina ceramic (JMM-ZTA) for a ceramic-on-ceramic hip replacement has been developed. The JMM-ZTA has a fracture toughness superior to zirconia, and the JMM-ZTA/JMM-ZTA combination has superior wear-resistant performance to alumina/alumina. Moreover, the JMM-ZTA shows an excellent crystalline phase stability. Therefore, the JMM-ZTA is believed to be useful for artificial hip prostheses.

Fluorescence spectroscopic analysis of surface and subsurface residual stress fields in alumina hip joints

We aim to establish a confocal spectroscopic technique able to study the features of fluorescence spectra arising from native Cr3+ impurity in polycrystalline alumina (Al2O3) as a biomaterial and to use their emission lines as microscopic probes for the characterization of residual stress fields stored in artificial hip prostheses during their implantation in vivo. As an application of the technique, we report for the first time concerning the evolution of microscopic (residual) stress fields stored on the surface and in the subsurface of N=7 retrieved Al2O3 hip joints after exposure in the human body from a few months to 19 yr. The micrometric diameter of the laser beam waist impinging on the joint surface (typically about 1 microm in lateral resolution) enables us to estimate the patterns and magnitude of residual stress with high spatial resolution, at least comparable with the grain size of the material. In addition, a selected confocal configuration for the optical probe enables minimization of the probe size along the in-depth direction. According to a statistical collection of data on the microscopic level for retrieved femoral heads in toto, a residual stress field arising from loading history in vivo during the lifetime of the Al2O3 femoral head can be revealed. Finally, an interpretation is given of microscopic wear mechanisms in Al2O3 artificial hip joints consistent with the observed evolution of surface residual stress fields on elapsed time in vivo.

Investigation into dosimetric effect of a MAGNA‐SITE™ tissue expander on post‐mastectomy radiotherapy

It is increasingly common for radiotherapy departments to encounter high density objects in patients being planned for radiotherapy. Many cases, such as artificial hip prostheses, are well documented. In our cancer center we have recently come across a new type of implant--a McGhan Style 133 Tissue Expander--implanted in patients who have undergone a mastectomy and will in future have breast reconstruction. This type of implant contains a small rare earth magnet encased in a titanium body, which induces significant perturbations in the dose distribution. These perturbations have been measured using a p-type semiconductor diode. Attenuation of up to 30% of local dose has been observed for a single beam. However, in more realistic clinical situations using tangential parallel opposed beams, it is estimated that part of the planning target volume maybe be underdosed by approximately 10%. Comparisons have been made between measured attenuation and that calculated by a treatment planning system, which demonstrates inadequate modeling of the dose perturbation caused by the implant in this case.

Shape Optimization of an Artificial Hip Prosthesis.

Shape Optimization of an Artificial Hip Prosthesis.

416 3 次元 CAD モデルを用いた全人工股関節ステム形状最適設計

416 3 次元 CAD モデルを用いた全人工股関節ステム形状最適設計

Microstructural Characterization of a New Polytetrafluoroethylene for Artificial Hip Prosthesis

Abstract All joints in the human body are subject to destruction by disease and trauma. Although the modem concept of joint replacements dates back to 1800's, polymeric material were not utilized till 1940's [1]. Early experiments were conducted with polymethacrylate and polytetrafluoroethylene. The results were disappointing with the polymeric material either quick fracturing or wearing at an extreme rapid rate. Microstructures were not well investigated as a function of processing conditions. The goal of this research is to eliminate the presence of oxygen within the components during its processing operations, which is responsible for early failure of polytetrafluoroethylene. One approach to eliminate or reduce the amount of oxygen would be processing the PTFE resin in vacuum conditions. This research is aimed towards investigating the microstructure of PTFE when processed under vacuum conditions using SEM and TEM along with EDXS. The fabricated PTFE billet samples were received from Dewal Industries, NJ and the PTFE components in vacuum conditions, processed at University of Massachusetts Lowell (UML) were studied using microscopic techniques.

Book Remodeling Analysis of Femur Using Hybrid Beam Theory

An investigation has been performed to develop an analysis tool based on a nonlinear beam theory, which can be used to predict the long-term behavior of an artificial hip joint. The nonlinear behav ior of the femur arise from the coupled dependence of the bone density and the mechanical properties on each other. The beam theory together with its numerical algorithm is developed to take into account the nonlinear bone remodeling process of the femur that is long enough to be assumed as a beam. A piecewise linear curve for the bone remodeling rate is used in the bone remodeling theory and the surface area density of bone is modeled as the third order polynomial function of bone density. At each section of the beam, a constant curvature is assumed and the longitudinal strains are also assumed to vary linearly across the section. The Newton-Rhapson iteration method is used to solve the nonlinear equations for each cross section of the bone and a backward method is used to march along the time. The density and the remodeling signal ar, calculated along with time for the various time steps, and the developed beam theory has been verified by comparing with the results of finite element analysis of a remodeling bone with an artificial hip joint of titanium prosthesis subjected to uni-axial loads and pure bending moment. It is concluded that the developed beam theory can be used to predict the long-term behavior of the femur and thus to design the artificial hip prosthesis.

Hydroxyapatite–zirconia composite coatings via the plasma spraying process

Abstract Hydroxyapatite (HA) coatings have been deposited on artificial hip prosthesis as a bioactive surface to induce a direct chemical bond with natural bones and hence achieve a biological fixation onto implants. However, its intrinsic weak mechanical properties have always been the main obstacle to its applications, especially in the area of orthopedic applications, where implants have to withstand medium–high loading. In this study, HA and yttria-stabilized zirconia (YSZ) powders were ball-milled and then sprayed onto Ti–6Al–4V alloy substrates. The effect of plasma arc current on the phase composition was investigated. The amount of decomposition of HA increases with the increase of plasma arc current from 600 to 1000 A. The impurities, as a result of the decomposition, were α-TCP (alpha-tricalcium phosphate) and CaO, although a small amount of TTCP (tetra-calcium phosphate) was also detected. The influence of ZrO2 on the decomposition of HA was also studied. The results show that ZrO2 reacts with CaO in HA to form CaZrO3. This reaction caused an increase in the decomposition of the CaO-poor HA.

Orthopedic surgeons ponder: how best to secure artificial hip prostheses?

Orthopedic surgeons ponder: how best to secure artificial hip prostheses?

Orthopedic Surgeons Ponder: How Best to Secure Artificial Hip Prostheses?

MORE THAN 126 000 hip replacement procedures are performed annually in this country and, because of the graying of America, that number is likely to increase. But orthopedic surgeons are concerned by reports that too many—the number varies with the surgical series being reported—artificial hips become loose and need to be surgically revised. This raises the question: what is the best way to secure an artificial hip prosthesis in place? There are two competing technologies, one that uses a polymethyl methacrylate cement to anchor the device to the bone and one that uses bone growth into a porous surface to hold it secure. A definitive answer about which technology is the better and more permanent prosthesis may be some time in coming. Until then, orthopedists will continue to debate the relative merits of each, and remain torn between what they can accomplish and the results they would like to achieve.

Artificial hip prosthesis in acute and nonunion fractures of the femoral neck: follow-up study of seventy cases.

The replacement value of the artificial hip prosthesis in acute and nonunion fractures of the femoral neck has been substantiated. The goal of all reconstruction procedures is attainable with correct prosthesis insertion. The relatively guarded prognosis in the acute fracture is circumvented by the immediate use of prosthesis in a selected group of cases. This report will present the criteria evolved for correct prosthesis choice, the major complications of prosthesis use, the indications for prosthesis use, and incomplete follow-up results on 70 cases. The series consisted of 49 acute and 21 nonunion fractures. CHOICE OF CORRECT PROSTHESIS A satisfactory prosthesis must be capable of restoring neck length, anatomic valgus angle, and anteversion angle. It must be capable of retaining its position in the bone. It must not cause reactive changes of absorption in the bone. Four types of prostheses were used in this series. Transfixing-Type Prosthesis. —The Judet and J.