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Ulnar impaction syndrome is a painful condition of excessive contact and wear between the ulna and the carpus with an associated is a degenerative tear of the TFCC. Positive, neutral, and negative ulnar variance. Relationship between radial length and ulnar variance. Radial length is the measure from distal ulna to radial styloid process.
Consideration should also be given to pigmented villonodular synovitis, in the setting of ulnar deviation and metacarpophalangeal synovitis. [citation needed] Ulnar deviation is also a physiological movement of the wrist, where the hand including the fingers move towards the ulna. Ulnar deviation is a disorder in which flexion by ulnar nerve ...
There is an increased risk of interosseous intercarpal injury if the ulnar variance (the difference in height between the distal end of the ulna and the distal end of the radius) is more than 2mm and there is fracture into the wrist joint. [5] Triangular fibrocartilage complex (TFCC) injury occurs in 39% to 82% of cases.
Negative ulnar variance. Some Kienböck's patients present with an abnormally large difference in length between the radius and the ulna , termed " ulnar variance ", which is hypothesized to cause undue pressure on the lunate, contributing to its avascularity.
This algorithm can easily be adapted to compute the variance of a finite population: simply divide by n instead of n − 1 on the last line.. Because SumSq and (Sum×Sum)/n can be very similar numbers, cancellation can lead to the precision of the result to be much less than the inherent precision of the floating-point arithmetic used to perform the computation.
which is an unbiased estimator of the variance of the mean in terms of the observed sample variance and known quantities. If the autocorrelations are identically zero, this expression reduces to the well-known result for the variance of the mean for independent data. The effect of the expectation operator in these expressions is that the ...
An advantage of variance as a measure of dispersion is that it is more amenable to algebraic manipulation than other measures of dispersion such as the expected absolute deviation; for example, the variance of a sum of uncorrelated random variables is equal to the sum of their variances. A disadvantage of the variance for practical applications ...
In probability theory and statistics, the index of dispersion, [1] dispersion index, coefficient of dispersion, relative variance, or variance-to-mean ratio (VMR), like the coefficient of variation, is a normalized measure of the dispersion of a probability distribution: it is a measure used to quantify whether a set of observed occurrences are clustered or dispersed compared to a standard ...