Three-dimensional finite element analysis of unicompartmental knee arthroplasty--the influence of tibial component inclination.

Aseptic loosening and failure of a tibial component are recognized problems in unicompartmental knee arthroplasty (UKA). Excessive stress on the supporting cancellous bone is thought to contribute to the loosening and failure. Of factors that could influence supporting cancellous bone stresses, we focused on the inclination of a unicompartmental tibial component by analyzing the effect of coronal plane and sagittal plane inclination. Detailed geometrically accurate, three-dimensional finite element models were constructed from computed tomography (CT) data of a typical adult male proximal tibia. The material properties for the models were obtained directly from the CT data to simulate the inhomogeneous distribution of cancellous bone properties. Placing the component in slight valgus inclination in the coronal plane reduced the cancellous bone stresses. Posterior inclination in the sagittal plane caused a moderate increase in the stresses. Our results suggest that slight valgus inclination of a UKA tibial component may be preferable to varus or square inclination in the coronal plane. An excessive posterior slope of a tibial component should be avoided.

The effects of tibial component inclination on bone stress after unicompartmental knee arthroplasty.

Unlike the case with total knee arthroplasty, the femorotibial angle (FTA) after unicompartmental knee arthroplasty (UKA) does not directly depend on the inclination of the tibial component when the height of the joint line is maintained. This study analyzed the effects of the inclination of the tibial component in the coronal plane on the contact pressure of the implant-bone surface and the stresses on the proximal tibia. A two-dimensional, coronal plane model of the proximal tibia was subjected to finite-element analysis. Sixteen patterns of finite-element models of equal FTA were developed in which the inclination of tibial components ranged from 5 degrees valgus to 10 degrees varus in increments of 1 degrees. Stress concentration at the proximal medial diaphyseal cortex gradually increased as the inclination changed from valgus to varus. Maximum contact pressure on the metal-bone interface similarly changed and shifted from the lateral edge to the medial edge of the implant as the inclination changed to varus. It was found that even without changing FTA, the inclination of the tibial component might affect stress concentration and contact pressure in the proximal tibia after UKA. The results suggested that slight valgus inclination of the tibial component might be preferable to varus and even to 0 degrees (square) inclination so far as the stress distribution is concerned.

The MEK1-ERK map kinase pathway and the PI 3-kinase-Akt pathway independently mediate anti-apoptotic signals in HepG2 liver cancer cells.

Primary liver cancers, which are generally hypervascular in nature, depend highly on blood supply. So far there are few reports on apoptosis of liver cancer cells upon deprivation of serum-derived survival factors. The aim of our study is to clarify molecular mechanisms by which liver cancer cells survive with the aid of serum. In HepG2 liver cancer cells, serum deprivation induced time-dependent increase in the number of apoptotic cells, which was detected by fragmentation of genomic DNA and fluorescent nuclear staining. The activity of extracellular signal-regulated kinase (ERK) did not decrease considerably after serum deprivation, although it increased after serum stimulation. However, we found that the MEK1 inhibitor PD98059, but not the p38 kinase inhibitor SB203580, potently induced apoptosis of the liver cancer cells in the presence of serum, indicating that the MEK-ERK signaling pathway is required for serum-dependent survival of HepG2 cells. In agreement with this notion, transient expression of active MEK1 prevented apoptosis in serum-deprived condition. We also found that the protective effect of serum against apoptosis was totally abrogated by LY294002 or wortmannin, which are the inhibitors of phosphatidylinositol (PI) 3-kinase. The activity of Akt, the target of PI 3-kinase, decreased gradually after deprivation of serum, whereas it was rapidly reactivated upon serum stimulation. These data indicate that survival of HepG2 liver cancer cells depends upon serum and that both the MEK1-ERK- and the PI 3-kinase-Akt- pathways are required for survival signaling to the nucleus.

[Relapse of gingival tumor during hematological remission in acute promyelocytic leukemia].

A 56-year-old man was admitted to the hospital in April, 1986, with the chief complaint of fatigue. The diagnosis of acute promyelocytic leukemia (APL) was made based on the proliferation of atypical promyelocytes in the bone marrow. No gingival swelling was found on admission. A complete remission was achieved by the BHAC-DMP therapy and maintained by the consolidation therapy and the intensification therapy. In July, 1987, he noticed a solitary gingival tumor around the left lower second molar. The biopsy showed the massive infiltration of leukemic cells, despite the hematological remission. Combination chemotherapy was not effective but the tumor disappeared by irradiation. A hematological relapse occurred in November, 1987, but the second complete remission was achieved by the AB-triple V therapy. He died because of the second hematological relapse in July, 1988. Along with the wide use of intensive chemotherapy for acute leukemia, tumor forming leukemia during the hematological remission, as seen in this case, would be increasing. Thus, we should not overlook any newly formed tumor in the treatment of leukemia.

["AB-Triple V" therapy of relapsed or refractory acute myelogenous leukemia].

Sixteen adults with acute myelogenous leukemia (AML) in relapse or refractory to conventional therapy were treated with AB-Triple V therapy. This regimen consists of aclarubicin, behenoyl cytosine arabinoside, etoposide, vincristine, and vinblastine or vindesine. Patients who obtained complete remission (CR) were then given monthly three courses of AB-Triple V therapy, and further courses of AB-triple V therapy every three months. Eleven of the 16 patients entered CR, three were no response, and two died early after initial AB-Triple V therapy. Among 11 patients who achieved CR, 7 are alive and in CR during 1 to 13 months, one died of hepatic failure, and three patients died of infection in CR. Systemic arthralgia following the administration of vinblastine were frequently observed. These results indicate that this salvage therapy are useful relapsed or refractory AML. Therefore, the role of this combination chemotherapy as a part of the initial post-remission therapy needs to be evaluated.

The use of multidimensional perceptual models in the selection of sonar echo features.

The development of an accurate and efficient sonar-target classification system depends upon the identification of a set of signal features which may be used to discriminate important classes of signals. Feature selection can be facilitated through the identification of perceptual features used by human listeners in discriminating relevant sonar echoes. This study was conducted to establish a more reliable means of identifying perceptual features in terms of physical signal parameters as an initial step toward the development of an automatic sonar-target classification system. The results of an experiment involving eight subjects and six sonar echoes are presented. A model of the perceptual structure of these echoes was derived from subject similarity judgments using a multidimensional scaling (MDS) technique. It was found that three perceptual features accounted for the similarity judgments made by the human listeners. Echoes modified along candidate physical dimensions were employed to aid in the identification of perceptual dimensions in terms of physical signal parameters. The three perceptual features could be associated with signal parameters involving the amplitude envelope of the echoes.

Real-time noncontacting distance measurement using optical triangulation.

Real-time noncontacting distance measurement systems are constructed using photogrammetric principles. The system is used to measure a distance between two points specified by sharp visible contrast change under optical illumination. Tests of the system indicate that it can measure the distance with a repeatability of better than one part in 10(4).

Experimental analysis of surface flaw detection using grazing angle illumination.

The capability of a method using grazing angle illumination for automated surface flaw detection has been analyzed experimentally for actual flaws. Bearing rollers were chosen as test samples and two different methods, low angle scattered light observation and high angle scattered light observation, were evaluated. For the latter method, an analysis of the data from a number of samples results in a sample classification that accurately matches that determined by careful visual inspection.

Optical heterodyne scanning microscope.

A new optical heterodyne scanning microscope is described in which both the illumination beam and reference beam scan the object in synchronization. Characteristics of the microscope are similar to those of the laser scanning microscope. The present system, however, has additional advantages in that the object illumination can be at least one order of magnitude less intense and that ambient light has no effect for images. Preliminary experimental results will be shown, including a two-dimensional cross-section pattern from a 3-D object, unfocused image rejection characteristics, and images of some biological samples.

Surface flaw detection using oblique angle illumination.

An analysis of a surface flaw detection method is presented in which oblique illumination is combined with a high pass spatial filter to detect the light scattered from surface flaws. The effects of surface finishes of test samples (meteoric plates) are assessed statistically, and the sensitivity of the system is calculated. Data have been collected on diffraction patterns and surface scratch detection for three stainless steel plates having different surface finishes. The results agree with theoretical considerations and are quite promising.