Which factors determine the wear rate of large-diameter metal-on-metal hip replacements? Multivariate analysis of two hundred and seventy-six components.

BACKGROUND: Determining the relationship between clinical factors and engineering analysis of retrieved hip implants can help our understanding of the mechanism of device failure. This is particularly important for metal-on-metal hip arthroplasties because the most common cause of failure is unexplained. We sought to understand the variation in wear rates in a large series of retrieved metal-on-metal hip arthroplasty components. METHODS: We prospectively recorded preoperative, intraoperative, and postoperative data to study the effect on both head and cup wear rates of the following variables: patient sex, cause of failure, manufacturer type, resurfacing or modular design, blood cobalt and chromium levels, edge-loading, femoral head size, and cup inclination angle. We analyzed 276 components (138 femoral head and acetabular cup couples) retrieved from failed metal-on-metal hip replacements. RESULTS: We found a high rate of edge-loading (64%), but only forty-three (31%) of 138 hips had a cup inclination angle of >55°. Multivariate analysis showed that the most important factor responsible for the variation in wear rate was the presence or absence of edge-loading, even when adjusted for cup inclination angle. Strong positive correlations were found between acetabular cup and femoral head wear rates and between wear rates and both blood cobalt and chromium ion levels. CONCLUSIONS: Multivariate analysis of nine factors found that edge-loading was the most important predictor of wear rate and occurred in two-thirds of failed metal-on-metal hip replacements. The majority did not have excessive cup inclination angles: 68% had an inclination angle of ≤55°. This finding, together with the relatively low median wear rate of the components in our study, suggests that cup position and/or wear rate may not be the only outcome related to failure of metal-on-metal hip replacements.

A comparison of explanted Articular Surface Replacement and Birmingham Hip Resurfacing components.

The Articular Surface Replacement (ASR) hip resurfacing arthroplasty has a failure rate of 12.0% at five years, compared with 4.3% for the Birmingham Hip Resurfacing (BHR). We analysed 66 ASR and 64 BHR explanted metal-on-metal hip replacements with the aim of understanding their mechanisms of failure. We measured the linear wear rates of the acetabular and femoral components and analysed the clinical cause of failure, pre-revision blood metal ion levels and orientation of the acetabular component. There was no significant difference in metal ion levels (chromium, p = 0.82; cobalt, p = 0.40) or head wear rate (p = 0.14) between the two groups. The ASR had a significantly increased rate of wear of the acetabular component (p = 0.03) and a significantly increased occurrence of edge loading (p < 0.005), which can be attributed to differences in design between the ASR and BHR. The effects of differences in design on the in vivo wear rates are discussed: these may provide an explanation as to why the ASR is more sensitive to suboptimal positioning than the BHR.

Retrieval analysis of 240 metal-on-metal hip components, comparing modular total hip replacement with hip resurfacing.

This study compared component wear rates and pre-revision blood metal ions levels in two groups of failed metal-on-metal hip arthroplasties: hip resurfacing and modular total hip replacement (THR). There was no significant difference in the median rate of linear wear between the groups for both acetabular (p = 0.4633) and femoral (p = 0.0872) components. There was also no significant difference in the median linear wear rates when failed hip resurfacing and modular THR hips of the same type (ASR and Birmingham hip resurfacing (BHR)) were compared. Unlike other studies of well-functioning hips, there was no significant difference in pre-revision blood metal ion levels between hip resurfacing and modular THR. Edge loading was common in both groups, but more common in the resurfacing group (67%) than in the modular group (57%). However, this was not significant (p = 0.3479). We attribute this difference to retention of the neck in resurfacing of the hip, leading to impingement-type edge loading. This was supported by visual evidence of impingement on the femur. These findings show that failed metal-on-metal hip resurfacing and modular THRs have similar component wear rates and are both associated with raised pre-revision blood levels of metal ions.

[Technical limits of PET/CT with 18FDG in prostate cancer]. / Technische Grenzen des PET/CT mit 18FDG beim Adenokarzinom der Prostata.

There is increasing evidence that (18)FDG-PET is not useful for the imaging of primary prostate cancer. The aim of this examination was to prove whether or not these poor results are due to technical deficiencies of the examination method like older image reconstruction techniques, extensive (18)FDG-tracer activity in the bladder or improper contrast staining of the rectum. We examined three patients with primary prostate cancer using a modern combined PET/CT system, continuous irrigation of the bladder and an air-inflated rectal balloon catheter. PET/CT images show an exact depiction of both the prostate and all surrounding anatomic structures but no enhanced uptake of radiotracer in the tumour. Therefore, the mentioned poor results of (18)FDG-PET seem not to be due to technical deficiencies.

FDG-PET in immunocompetent patients with primary central nervous system lymphoma: correlation with MRI and clinical follow-up.

PURPOSE: The role of FDG-PET in primary central nervous system lymphoma (PCNSL) is unclear. It was the aim of this study to investigate the role of FDG-PET in detecting PCNSL and in predicting response to chemotherapy. METHODS: An FDG-PET scan of the brain was performed in 15 patients with histologically proven PCNSL (16 PET examinations, Siemens ECAT EXACT). PET was planned to investigate patients at the time of primary diagnosis, after chemotherapy and at the time of suspected relapse in seven, five and three cases, respectively. All except two patients simultaneously underwent MRI of the brain. FDG-PET results were correlated with histological results after stereotactic biopsy (primary diagnosis group) and with clinical data and MRI during follow-up. RESULTS: Six of the seven patients in the primary diagnosis group demonstrated a true positive finding (86%). In one of the true positive PET patients, there were two tumour lesions, one of which was only detectable on the FLAIR MRI sequence. In five patients, FDG-PET showed no sign of PCNSL during ongoing chemotherapy. These results were confirmed by the clinical follow-up (mean 26.6 months). MRI demonstrated minimal residual disease which had disappeared on further follow-up MRI in three of these five patients at the time of PET scanning. Recurrence of disease was confirmed concordantly by FDG-PET and MRI in three different patients. The standardised uptake value of all tumours was 10.2 (4.3-13.7). CONCLUSION: PCNSLs demonstrate high FDG uptake and can be diagnosed by FDG-PET with high sensitivity. It seems that FDG-PET is suitable for early therapeutic monitoring after chemotherapy.

Hybrid zones between invasive Rorippa austriaca and native R. sylvestris (Brassicaceae) in Germany: ploidy levels and patterns of fitness in the field.

Hybrid zones may serve as natural laboratories for evolutionary studies. One common viewpoint is that hybrids may always be less fit than their parents due to genetic discontinuities. An alternative idea is that genotype-environment interactions influence the outcome of natural hybridization. Our comparative study of two different natural hybrid zones between the invasive diploid Rorippa austriaca and the native polyploid R. sylvestris in Germany identified the ploidy level as a major determinant of hybrid fitness. Different ploidy levels and patterns of fitness were detected in different hybrid zones. In one hybrid zone (Mülheim, Ruhr valley) hybrids were pentaploid and showed a relatively high seed set, whereas in the second hybrid zone (Randersacker, Main valley) hybrids were triploid and displayed extremely low fitness values. Analyses of fitness values in different natural hybrid zones between the same two species may lead to very different conclusions about the evolutionary significance of natural hybridization.

Improved diagnosis of advanced bone marrow metastases by means of radiolabeled antigranulocyte antibodies.

Assessment of bone marrow metastases using Tc-99m-labeled antigranulocyte antibodies and Tc-99m-labeled nanocolloids is discussed in osseous metastasizing breast cancer. A 53-year-old patient with bone metastases of breast cancer (pT2 pN1biv cM1) developed leukocytopenia WHO Grade III following polychemotherapy. Bone marrow scintigraphy with Tc-99m labeled nanocolloids and Tc-99m-labeled antigranulocyte antibodies revealed pronounced bone marrow infiltration as the cause. Comparing both procedures, the images with antigranulocyte antibodies showed a clearly better bone marrow image, considerably higher contrast and almost no superimposition of the liver over the spine. In osseous metastasizing breast cancer, scintigraphy with Tc-99m-labeled antigranulocyte antibodies enables assessment of metastases in the entire bone marrow.

PET-imaging in tumors of the reproductive trac.

There is increasing evidence that metabolic imaging with positron-emission tomography (PET) using fluor-18 labeled fluorodeoxyglucose (18F FDG) is highly accurate for in vivo detection of a variety of malignancies. This quality gives FDG-PET an important role in the detection of malignant tumors and their metastases as well as for differentiation of tumors of unknown etiology. In the male and female reproductive tract, whole body imaging with FDG-PET is in particular capable of visualizing lymph-node and distant metastases before these changes become apparent on conventional cross-sectional imaging modalities. According to the incidence of tumors in the reproductive tract, FDG-PET-imaging has been evaluated in prostate cancer, ovarian cancer, cervical and testicular cancer. The role of PET is discussed with respect to the current management of patients. The presented data indicate that FDG-PET is more accurate for lymph-node staging in cervical cancer and testicular cancer. In ovarian cancer, FDG-PET may be helpful for detection of tumor recurrence. The role of FDG-PET is questionable in prostate cancer, due to the low metabolic activity of this type of cancer. Carbon-11 labeled acetate and carbon-11 or fluor-18 labeled choline are more promising than FDG for detection of recurrence in prostate cancer. In all other tumors of the reproductive tract there is limited experience with PET for a final conclusion.

Staging and monitoring response to treatment in primary non-Hodgkin's lymphoma of bone marrow using (18)F-fluorodeoxyglucose positron emission tomography.

Bone marrow involvement can be found in patients with low-, intermediate-, or high-grade non-Hodgkin's lymphoma. A 40-year-old woman experienced onset of low back pain radiating into her entire right lower extremity. Plain x-rays of her right leg and computed tomography of chest, abdomen, and pelvis were unremarkable. Magnetic resonance imaging of pelvis and thighs revealed diffusely abnormal marrow signal (low T1 and high T2 weighted) in the pelvis and femora. The patient underwent (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) scan to evaluate the extent of her disease. The scan revealed diffuse scattered foci of abnormal FDG uptake in the bone/bone marrow, which was particularly intense in the axial bones. Bone marrow biopsy confirmed extensive involvement of the bone marrow with diffuse large B-cell lymphoma. This case report highlights the utility of FDG-PET in the detection of bone marrow involvement by aggressive lymphoma.

Progressive intermediate-grade non-Hodgkin's lymphoma after high-dose therapy and autologous peripheral stem-cell transplantation: changing the natural history with monoclonal antibody therapy.

The prognosis of patients with progressive intermediate-grade non-Hodgkin's lymphoma (NHL) after high-dose chemotherapy and autologous peripheral stem-cell transplantation (PSCT) is poor, with survival measured in months. The advent of monoclonal antibody therapy for NHL has created new options for effective therapy with relatively mild side effects. We report on two patients with progressive intermediate-grade NHL after PSCT who were treated with monoclonal antibody therapy. Both patients initially received rituximab (unlabeled anti-CD20 monoclonal antibody) and were subsequently treated with (90)Y-epratuzumab (yttrium-90-labeled humanized anti-CD22 monoclonal antibody) at relapse. One patient received (90)Y-epratuzumab alone while the other was treated with higher doses in combination with autologous peripheral stem-cell infusion. Both patients achieved a rapid response to the radiolabeled antibody with minimal toxicity. Monoclonal antibody therapy may be an effective and tolerable treatment for progressive NHL after PSCT.

Fusarium in wheat: importance and toxin production in the field - possibilities and limits of fungicide treatments.

Effects of plant cropping measures on toxin production were investigated. The use of the plough reduced the DON level by 71%. Additionally, the choice of less sensitive varieties, as well as an adequate nitrogen fertilization showed a significant reduction of the DON content in grain. In non-ploughed systems, an ear application with fungicides reduced DON by 63 %. The effects of strobilurin containing fungicides (strobilurin solo products and strobilurin-azole mixtures) upon the toxin content were compared with azoles.

Lipid composition of glucose-stimulated pancreatic islets and insulin-secreting tumor cells.

The effect of glucose stimulation (25 mM for 5 min) on the phospholipid and neutral lipid composition of isolated pancreatic islets was studied to find out whether there is a change in the mass of potential lipid mediators or modulators of insulin secretion. For comparison, the lipid compositions of homogenates and subcellular fractions from RINm5F insulin-secreting tumor cells and of glucose-stimulated streptozotocin/nicotinamide-induced islet cell tumors were analyzed. After separation of the lipid extract into a neutral and an acidic fraction by anion-exchange chromatography, lipids were separated by high-performance thin-layer chromatography and quantitated by in situ densitometry of the cupric sulfate-charred bands. In glucose-stimulated islets, the molar percentages of phosphatidic acid (PA) and of phosphatidylinositol were significantly increased (3.1 vs. 4.7 mol% and 8.6 vs. 11.8 mol%), while those of all other phospholipids and neutral lipids, including 1,2-diacylglycerol, were not significantly changed. In stimulated islet cell tumors, an increase of PA was visible in the microsomal fraction, and there was an increase of lysophosphatidylcholine in the mitochondrial fraction. However, in both tumoral tissues, particularly in RINm5F cells, the lipid distribution pattern showed abnormalities which can be regarded as a loss of differentiation and which limit the usefulness of these tissues for the study of the physiological regulation of lipid metabolism during glucose stimulation. In conclusion, the data are in accordance with a role of PA early in stimulus-secretion coupling. The well-known stimulation of phospholipid synthesis in pancreatic islets during glucose-induced insulin secretion does not result in an increase in the total phospholipid mass.

Differences between predictive characteristics of signal-averaged electrocardiographic variables for postinfarction sudden death and ventricular tachycardia.

Several studies indicate that the electrophysiologic substrate for sustained ventricular tachycardia differs from that of ventricular fibrillation. This prospective study examined whether there were clinically relevant differences between the predictive values of the standard time-domain signal-averaged (SA) electrocardiographic (ECG) variables for ventricular tachycardia and sudden death after myocardial infarction. Predischarge SA electrocardiograms were recorded in 332 patients after infarction. During a follow-up period of greater than or equal to 6 months, there were 12 sudden deaths (3.6%), 14 patients (4.2%) developed spontaneous sustained ventricular tachycardia and 20 patients (6%) died of circulatory failure. The sensitivity, specificity and positive predictive accuracy of the numerical values of the time-domain SA electrocardiographic variables for predicting sudden death and ventricular tachycardia were compared. The optimal criteria for predicting ventricular tachycardia required the positivity of greater than or equal to 2 of the standard time-domain SA variables, whereas the optimal criteria for predicting sudden death required the positivity of all 3 variables. A high specificity was sustained over a wider range of sensitivity for sudden death than it was for ventricular tachycardia and the values of the variables which provided the same sensitivity for sudden death and ventricular tachycardia were different. For a sensitivity of 70%, the positive predictive accuracy was 31% for predicting sudden death and 13% for predicting ventricular tachycardia. The study concludes that differences in the predictive characteristics of variables for ventricular tachycardia and sudden death may be used to refine postinfarction risk stratification.