Performance of local optimization in single-plane fluoroscopic analysis for total knee arthroplasty.

Fluoroscopy-derived joint kinematics plays an important role in the evaluation of knee prostheses. Fluoroscopic analysis requires estimation of the 3D prosthesis pose from its 2D silhouette in the fluoroscopic image, by optimizing a dissimilarity measure. Currently, extensive user-interaction is needed, which makes analysis labor-intensive and operator-dependent. The aim of this study was to review five optimization methods for 3D pose estimation and to assess their performance in finding the correct solution. Two derivative-free optimizers (DHSAnn and IIPM) and three gradient-based optimizers (LevMar, DoNLP2 and IpOpt) were evaluated. For the latter three optimizers two different implementations were evaluated: one with a numerically approximated gradient and one with an analytically derived gradient for computational efficiency. On phantom data, all methods were able to find the 3D pose within 1mm and 1° in more than 85% of cases. IpOpt had the highest success-rate: 97%. On clinical data, the success rates were higher than 85% for the in-plane positions, but not for the rotations. IpOpt was the most expensive method and the application of an analytically derived gradients accelerated the gradient-based methods by a factor 3-4 without any differences in success rate. In conclusion, 85% of the frames can be analyzed automatically in clinical data and only 15% of the frames require manual supervision. The optimal success-rate on phantom data (97% with IpOpt) on phantom data indicates that even less supervision may become feasible.

Does enhanced information exchange between social insurance physicians and occupational physicians improve patient work resumption? A controlled intervention study.

BACKGROUND: Patient work resumption after sickness absence varies even among patients with similar pathologies and characteristics. Explanations remain uncertain. One newly investigated field is "information asymmetry", a situation in which critical information is not appropriately exchanged between stakeholders in disability management. It is hypothesised that information asymmetry between social insurance physicians and occupational physicians prolongs sickness absence. OBJECTIVES: To assess the influence of enhanced information exchange between these physicians on patient outcome. METHODS: Non-randomised controlled intervention study. The setting was the work inability assessment consultation of social insurance physicians in Belgium. Inclusion criteria were: employee, age 18-50, and subacute (more than one month) sickness absence. The intervention was a structured information exchange (through the use of a communication form) between the patient's social insurance physician and occupational physician. The intervention started when the patient's sickness absence reached the subacute stage, and ended when the sickness absence benefit was ceased or the duration exceeded one year. The primary outcome measure was the sickness absence benefit status of the patient assessed one year after benefit onset. RESULTS: Of the 1883 patients asked to enroll in the study, 1564 (84%) participated; 505 (32%) of 1564 patients were assigned to the intervention group and 1059 (68%) to the control group; 1553 (99%) of 1564 patients completed the study. In the intervention group, 86% received no sickness absence benefit at the end of the study, versus 84% in the control group (95% CI 0.91-1.15). No significant differences in other outcome parameters were obtained. CONCLUSIONS: Information exchange between physicians may not be enough to influence work resumption among patients on sickness absence. Further research on stakeholders' information asymmetry and its effect on the outcome of patients are necessary. The complexity of information asymmetry in disability management cannot be underestimated.

Return to work after surgery for lumbar disc herniation. A rehabilitation-oriented approach in insurance medicine.

STUDY DESIGN: An intervention study by the medical advisers of a social security sickness fund on a mandatorily insured patient population after open discectomy for herniated lumbar intervertebral disc. The medical advisers were randomized into two groups: a control group (n = 30) and an intervention group (n = 30). OBJECTIVES: To compare a rehabilitation-oriented approach in insurance medicine focused primarily on early mobilization and early resumption of professional activities with the usual claim-based practice. SUMMARY OF BACKGROUND DATA: This study included 710 patients, with a mean age of 39.2 years, who underwent surgery for herniated lumbar disc. METHODS: Medical advisers in the rehabilitation-oriented group examined the patients monthly, starting at 6 weeks after the surgical intervention. They used a newly developed protocol to motivate the patients and treating physicians toward social and professional reintegration. RESULTS: At 52 weeks, 10.1% of the patients guided by medical advisers from the rehabilitation-oriented group had not resumed work in contrast to 18.1% of the patients in the control group. It was statistically proven that this effect also holds during the follow-up period. CONCLUSIONS: A rehabilitation-oriented approach by the medical advisers of social security can increase the probability of a return to work for patients after lumbar disc herniation surgery.

Central role of epidermal growth factor (EGF) receptor density in anchorage-independent growth of normal rat kidney cells.

Epidermal growth factor (EGF) receptor levels are known to play a central role in density dependent growth regulation of normal rat kidney (NRK) fibroblasts. Here we show that EGF receptor expression is strongly decreased when NRK cells are cultured under anchorage independent conditions, and that expression is returned to original levels upon cell readherence. Agents that stimulate anchorage independent growth (AIG) of NRK cells in the presence of EGF are shown to upregulate both EGF receptor promoter activity and (125)I-EGF binding capacity. These data show that two aspects of phenotypic transformation of NRK cells, namely density arrest and AIG, can both directly be correlated to EGF receptor levels.

Phenotypic transformation of normal rat kidney fibroblasts by endothelin-1. Different mode of action from lysophosphatidic acid, bradykinin, and prostaglandin f2alpha.

In the present study, we compared the effects of endothelin (ET)-1 on cell proliferation and second messenger induction in normal rat kidney (NRK) fibroblasts, with those of other activators of G-protein-coupled receptors such as prostaglandin (PG)-F2alpha, bradykinin (BK), and lysophosphatidic acid (LPA). LPA is mitogenic by itself, while the other factors require the presence of EGF. In density-arrested NRK cells, ET-1 and LPA induce phenotypic transformation rapidly, with similar kinetics as retinoic acid (RA) and transforming growth factor (TGF)-beta, while BK and PGF2alpha only do so with delayed kinetics. ET-1 and PGF2alpha are strong inducers of anchorage-independent growth, with a similar level of induction as TGFbeta, in contrast to LPA and BK. When investigating the second messenger generation, we found that ET-1 is the strongest activator of arachidonic acid release and phosphatidylinositol diphosphate hydrolysis. Only in the case of ET-1 the cell depolarization is not reversible upon removal of the factor. Similarly, only the ET-1-induced transient enhancement of intracellular calcium concentration is paralleled by both homologous and heterologous desensitization. In conclusion, these data show that ET-1 is a potent inducer of second messengers and phenotypic transformation in NRK cells, with characteristics that clearly differ from those of other activators of G-protein-coupled receptors, most likely as a result of prolonged receptor activation.

Epidermal growth factor (EGF) receptor density controls mitogenic activation of normal rat kidney (NRK) cells by EGF.

Normal rat kidney (NRK) fibroblasts are immortalized cells that are strictly dependent on externally added growth factors for proliferation. When cultured in the presence of epidermal growth factor (EGF) as the only growth stimulating hormone, these cells have a normal phenotype and undergo density-dependent growth inhibition. It has been postulated that this density-arrest results from a decrease of EGF receptor levels below a threshold level which makes these cells unresponsive to stimulation by EGF. In the present study, we show that NRK cells, made quiescent by serum-deprivation at submaximum density, are mitogenically still responsive to EGF, but show enhanced mitogenic stimulation after 8 hr pre-treatment with either transforming growth factor beta (TGF beta) or retinoic acid (RA), while prostaglandin F2 alpha (PGF2 alpha) and bradykinin (BK) enhance the mitogenic stimulation by EGF only slightly under these conditions. Addition of TGF beta or RA results in an increase of both 125I-EGF-binding capacity and EGF receptor mRNA levels. Using flow cytometric analysis, we show that pre-treatment with TGF beta or RA increases the percentage of cells entering the cell cycle as a function of time. Furthermore, pre-treatment of the cells with TGF beta or RA increases the rate of mitogen-activated protein kinase (MAPK) phosphorylation by EGF. PGF2 alpha and BK also increase EGF receptor levels, but only with delayed kinetics. These results show that already in serum-deprived quiescent NRK cells, EGF receptor levels limit EGF-induced mitogenic stimulation. This observation provides further evidence for the regulating role of the EGF receptor in density-dependent growth control of NRK cells.

Effect of bradykinin on loss of density-dependent growth inhibition of normal rat kidney cells.

Normal rat kidney fibroblasts, density-arrested in the presence of epidermal growth factor (EGF), can be restimulated to proliferate in a synchronous way and acquire a transformed phenotype following treatment with additional growth factors like retinoic acid (RA) and transforming growth factor (TGF)-beta. It was found that bradykinin has a strong inhibitory effect on growth stimulation induced by these factors, an effect which cannot be mimicked by PGF2 alpha. The growth-inhibiting effect can be blocked by inhibitors of cyclo-oxygenase activity, indicating that the relevant second messenger is most likely a prostaglandin. Externally added PGJ2, at a concentration of 10 microM, can mimic the inhibitory effect of bradykinin on the loss of density-arrest induced by RA suggesting that PGJ2 is a possible candidate for being the bradykinin induced growth-inhibiting prostaglandin.

Survey of cobalt exposure and respiratory health in diamond polishers.

This cross-sectional study was undertaken after the discovery of cobalt-related fibrosing alveolitis and bronchial asthma in diamond polishers occupationally exposed to cobalt. A total of 194 workers from 10 diamond polishing workshops and 59 workers from three other workshops from the diamond industry (control subjects) were studied; a questionnaire was administered and spirometry was performed. Cobalt exposure was assessed by environmental air sampling using both area and personal sampling and by measuring urinary cobalt concentration. When considered on a workshop basis, these environmental and biologic indices of exposure correlated well with each other. These measurements led to the definition of three cobalt exposure categories: a no exposure group, a low exposure group, and a high exposure group. The high exposure was, however, still below the present threshold limit value for cobalt (50 micrograms/m3). Spirometry showed that indices of ventilatory function (FVC and FEV1) were significantly (p less than 0.05) lower in the group with the highest exposure to cobalt. These differences were not due to differences in smoking habits. The results were confirmed when the data were analyzed by covariance analysis of lung function indices against smoking status, taking mean cobalt exposure in each workshop as a covariate, and when the data were analyzed by multiple regression analysis. This analysis showed that cobalt exposure correlated with decreased pulmonary function. Our results suggest that, during diamond polishing, exposure to cobalt at levels below the current threshold limit value is associated, on a group basis, with measurable effects on lung function parameters. The relationship between these cross-sectional epidemiologic findings and the occurrence of overt lung disease in diamond polishers remains to be established.

Exposure of diamond polishers to cobalt.

Interstitial pulmonary fibrosis due to 'hard metal' exposure is well known, and the presence of cobalt has always been considered as the causative factor. Recently interstitial pulmonary fibrosis has been described in diamond polishing workers. In this study the dust composition in different polisher's workplaces where diamond disks are in use has been determined. Careful investigation showed that the exposure to respirable dust was comparable to that of 'hard metal' workers. The dust consists mainly of iron and cobalt particles and small amounts of silica. No 'hard metals' have been found, and other fibrogenic agents such as beryllium have been excluded. These observations lend support to the hypothesis that crystalline cobalt particles can be responsible for pulmonary fibrosis even in the absence of carbides.

[Hydrocholecystitis in children and newborn infants. Apropos of 3 cases]. / L'hydrocholécyste chez l'enfant et le nouveau-né. A propos de trois observations.

We report two cases of hydrocholecystitis in children and one in a neonate. One child had hepatitis A and the other had typhoid fever. A beta-hemolytic group B streptococcal infection was found in the neonate. In all three cases, the first manifestation was an abdominal mass and treatment of the causative disease ensured recovery. These three observations provided us with the opportunity for reviewing the literature. Isolated hydrocholecystitis is distinguished from hydrocholecystitis as a symptom. The clinical evaluation and diagnostic investigations are described in detail; special attention is given to abdominal ultrasonography. Etiology and pathophysiology, as well as management are discussed. Our three cases and the review of the literature confirm the benign prognosis of this condition.

Value of the diagnostic sodium calcium edetate mobilization test as a criterion of lead absorption.

Among the laboratory tests available for the follow-up of lead-exposed workers, the EDTA mobilization test is presently underestimated in the diagnosis of lead intoxication. The authors present the results of regression comparison between the urinary lead excretion 3 h (PbU 3) or 6 h (PbU 6) after EDTA injection and blood lead (PbB), urinary aminolaevulinic acid (ALAU) and urinary lead (PbU). The results were collected from 133 medical examinations of workers exposed to lead, who put in a claim for compensation to the 'Fund of Occupational Diseases' in Belgium. On the basis of the regression curves, PbU 3 and PbU 6 limit values are calculated for different cut-off values of PbB in excessive lead absorption and lead intoxication. For each of these values the 'sensitivity', 'specificity' and 'validity' are calculated. As a result the authors still consider the EDTA mobilization test as a valuable parameter in the diagnosis of lead absorption.

Cost-benefit analysis of hepatitis-B vaccination.

Since 1983 the Belgian insurance Fund for Occupational Disease (FOD) has refunded the cost of hepatitis-B (HB) vaccination. Vaccination has been carried out by occupational physicians selectively on staff in hospitals and medical-care institutions. At the end of 1986, 40,000 people at high risk of HBV infection had been vaccinated. The vaccination costs are largely offset by the benefits resulting from the striking fall in the number of HB cases. The financial investment has proved economically beneficial for the insurance fund.

Neurochemical investigations in vitro with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in preparations of rat brain.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in concentrations ranging from 10(-8) M to 10(-6) M induced a decrease, and at 10(-5) M an increase of both basal and electrically evoked tritium outflow from [3H]dopamine-prelabeled rat striatal slices. These effects of MPTP were almost abolished in the presence of nomifensine. Chromatographic separation of the released tritium compounds revealed that the decrease of tritium outflow was mostly due to a decrease in the outflow of the dopamine metabolite [3H]3,4-dihydroxyphenylacetic acid (DOPAC) and the increase of tritium outflow due to a massive release of [3H]dopamine. MPTP inhibited oxidative deamination of [3H]dopamine non-competitively in a crude mitochondrial preparation of rat brain, with an apparent Ki value of 4.5 microM. No relevant effect of MPTP on adenylate cyclase activity in homogenates and on basal and electrically evoked tritium outflow from [3H]choline-prelabeled slices of rat striatum could be detected. In contrast, MPTP facilitated both basal and electrically evoked tritium outflow from [3H]noradrenaline-prelabeled rat cerebral occipital cortex slices. Furthermore, MPTP counteracted the inhibitory effect of clonidine on evoked tritium outflow from rat cerebral occipital cortex slices. Moreover, in the presence of cocaine, the effect on basal, but not that on electrically evoked tritium outflow was attenuated. These results are compatible with the view that MPTP has no affinity to dopamine receptors but is preferentially taken up into dopaminergic nerve terminals by the nomifensine-sensitive uptake system where it reaches a concentration sufficient to inhibit intraneuronal monoamine oxidase (MAO). In contrast, the facilitatory effect of MPTP on evoked tritium outflow from [3H]noradrenaline prelabeled rat cerebral occipital cortex slices appears to result from antagonistic effects at presynaptic alpha 2-adrenoceptors. The observation that MPTP at lower concentrations (10(-8) to 10(-7) M) inhibits basal tritium outflow from rat cerebral occipital cortex slices suggests that this compound inhibits also intraneuronal deamination of noradrenaline by MAO in noradrenergic nerve terminals.

Cobalt lung in diamond polishers.

Five diamond polishers with interstitial lung disease attributed to cobalt not alloyed to carbides of hard metals are described. The exposure originated from high-speed grinding tools with a polishing surface of microdiamonds cemented in very fine cobalt. Mineralogic analysis of lung tissue, lavage fluid, filtered air, and exhaust dust in the work environment revealed cobalt as the only toxic agent. Complaints consisted of work-related rhinitis, cough, chest tightness, dyspnea, anorexia, and weight loss, and were intensified in the absence of an adequate exhaust ventilation. Three subjects were in a rather subacute stage, as documented by open lung biopsy in 2 of them, and had a severe restrictive defect and markedly decreased diffusing capacity. Two patients presented a more chronic histologic pattern and had a less decreased diffusing capacity. Open lung biopsies showed in these 4 a fibrosing alveolitis, mainly of the centrilobular zones. In the former 2 patients, subacute lesions consisting of a mural mononuclear cell infiltrate, marked intra-alveolar desquamation, and multinucleated giant cells were found, whereas in the latter 2, centrilobular fibrosis with some microcyst formation was also already seen. Multiple multinucleated giant cells were present in the bronchoalveolar lavage fluid. Interruption of the exposure, with or without corticotherapy, caused a rapid regression of the complaints and a partial improvement of lung function.

X ray anomalies occurring in workers exposed to vibration caused by light tools.

A high frequency of radiological anomalies (vacuoles, cysts, enostoses) was found in workers exposed to vibration caused by light tools (screw drivers, nutrunners) compared with a non-exposed group. The lesions were mostly localised in the spongy carpal bones (os capitatum, os lunatum, os scaphoideum). There was no significant difference between the sexes, nor between the "active" or "passive" hand, both hands being simultaneously exposed. These findings support the need to implement preventive measures.

In vitro effect of the racemic mixture and the (-)enantiomer of N-n-propyl-3-(3-hydroxyphenyl)-piperidine (3-PPP) on postsynaptic dopamine receptors and on a presynaptic dopamine autoreceptor.

The racemic mixture and the (-)enantiomer of the putative dopamine autoreceptor agonist 3-PPP were investigated in vitro using dopamine-sensitive adenylate cyclase in homogenates of rat striatum as a model for a postsynaptic D1-receptor type and inhibition of electrically-evoked tritium overflow from rat striatal slices preincubated with [3H]choline and [3H]dopamine as a model for a postsynaptic D2- and a presynaptic dopamine autoreceptor type, respectively. In contrast, to apomorphine, neither the racemic mixture nor the (-)enantiomer exerted any effect, suggesting agonistic properties in all three receptor models. However, both (+/-)3-PPP and (-)3-PPP were weak antagonists at postsynaptic D1- and D2-receptors. The results of the present investigation suggest that the in vivo effects of 3-PPP are either the result of metabolic activation or that this drug activates an other dopamine autoreceptor type, pharmacologically different from that one modulating dopamine release.

Actual hazard of methyl bromide fumigation in soil disinfection.

Methyl bromide, a highly toxic and ready penetrating fumigant, is widely used against rodents, insects, mites, and a range of pathogenic organisms in soil, compost, and timber. To disinfect soil in greenhouses, methyl bromide is brought under pressure from outside by a vaporiser and blown on to ground under a polyethylene cover. The gas being three times heavier than air easily penetrates the ground. Depending on the local ventilation, a considerable amount of gas evaporates into the surrounding atmosphere, this emission being especially serious during the fumigation procedure and at the removal of the plastic cover. Previously, mechanical injection of methyl bromide on to the ground within closed areas was prohibited, since this technique exposed at least four disinfection workers at a time, who were provided with only a canister respirator, to gas concentrations of over 1000 ppm CH3Br. The present study established that fumigation with methyl bromide also carries risks for the well-protected worker inside, as well as for the one controlling the vaporiser. The concentration during application varies from 30 to 3000 ppm. Concentration in the air declines with time to 4 ppm CH3Br five days after application. Discarding the plastic sheet involves exposure to peak values as high as 200 ppm for a few seconds. On the ninth day after application, milling the soil can expose workers to up to 15 ppm; on the eleventh day no CH3Br concentration in the air could be found.