Biomedical subjects
H M Johnsen
Publications and source records attributed to H M Johnsen.
Ultrasound in the diagnosis of congenital dysplasia and dislocation of the hip joints in children older than two years.
To evaluate the use of ultrasound in the diagnosis to congenital dysplasia and dislocation of the hip (CDH) in children older than two years of age, 64 patients with normal hip joints and 47 patients with present or previous CDH were examined. Lateral and anterior ultrasound scanning was employed, and the coverage of the femoral head by the acetabular roof was assessed. The ultrasound measurements were compared with standard roentgenography, and a good accordance between the methods was found. A lateral projection of the femoral head in relation to the bony acetabular rim of more than 8 mm in children younger than ten years of age indicated subluxation and more than 15 mm at age two to four years indicated dislocation. Reliable images were obtained by ultrasound at any age between two and 18 years. Ultrasound is recommended as the primary imaging technique in the evaluation of hip joints, even in older children, and ultrasound should replace roentgenography in most of the follow-up examinations of children with previous CDH.
Ectopic pregnancy in Greenland. An epidemiological study.
A retrospective epidemiological investigation was carried out to study the rate and incidence of ectopic pregnancy (EP) in Greenland. Data from 7 of Greenland's 16 medical districts, representing 48% of the population, were available for analysis covering the years 1980-1984. A total of 4481 pregnancies were reported, including 105 cases of EP. A rate of EP 2.34 was calculated, one of the highest on record, and significantly higher than Scandinavian figures representing the same period. Estimated from our figures there would be 44 cases of EP annually in Greenland. Annual fluctuations, however, were seen, and a positive correlation was found to notified cases of Neisseria infections. Significance from the null hypothesis, however, was only found at the 10% level.
[Regression and correlation].
Simple linear regression and correlation are frequently used in medical publications. The methods are overused and have become greatly confused, probably because of the close similarity between the mathematical calculations. Simple regression is a method for a mathematical description of the dependence of a random response variable of another variable, a regressor, which is not random. The model can be used to predict the response form given values of the regressor. Correlation is a measure of the degree of linear association between two random variables, and has nothing to do with regression. The method is mainly an investigative tool in a statistical analysis, or to suggest further research; for forming hypotheses rather than for testing them. To judge form publications, fitting of a regression line and calculation of the correlation coefficient is the method of choice in modelling the linear relationship between two random variables. This is a completely misguided approach. When both variables are random, least squares estimation, as used in regression, is not appropriate. The correct method is to estimate a linear structural model by maximum likelihood.
[Stochastic variable, expectation and variance--basic concepts in statistical analysis].
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Protein concentration and oncotic pressure of interstitial fluid collected by wick technique.
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