I am studying the presence of an anatomical variation to the structure of a long bone in healthy and diseased individuals. I have two separate groups of individuals. The anatomical variation is torsion of long bone which sounds simple enough but not according to my reviewers. The big headache is that some individuals in both groups have a reversed direction of torsion. The majority are externally rotated; however; some are internally rotated.
- How do I convert circular data to linear?
- What do I use to test for Gaussian distribution? 3.Once I get past the distribution, what test do I use to compare? Is Mann-Whitney U test OK to use?
- Side-to side variability - left to right. Each pair of limbs regardless of disease status are torsed in the same direction.
The range of both groups is fairly narrow but in two opposite directions. Healthy individuals range (-5.44 degrees internal to + 6.39 external) Diseased individuals (-26.55 internal to +25.15) However when plotted on a compass rose the two groups' ranges hardly overlap.
I used (+) to determine external and (-) to determine internal torsion I am not a professional statistician so please go easy on me.
The original data set describing the geometry of the transverse axis (about 70 data pairs per specimen) was treated similarly as described for the longitudinal axis. Again, a normalised natural coordinate s was constructed such that 0 6 s 6 1, s = 0 at the medial border of the medial coronoid process and s = 1 at the lateral border of the medial coronoid process and the original Cartesian z–x reference frame (Fig. 2D) of each set of data was translated so that the medial border of the medial coronoid process was located at (z0, x0) = (0, 0). Sixth-order polynomial curve fits were performed (highest r2 = 0.9996, lowest r2 = 0.9933, mean r2 = 0.9981) and the x-coordinates were calculated for intervals of 0.025 (i.e. s = 0.025, 0.05, 0.075, 0.1, . . . , 1). The resulting series of 40 data set pairs characterised the geometry of the medial coronoid process at its transverse axis and was used for further calculations. The inclination angle b of the transverse axis of the medial coronoid process was calculated trigonometrically using the original coordinates of the first and last data set pair. Four joints (Table 1) were excluded from this analysis because the contour of the articular surface was not flat (like in all other joints) but had deep steps related to high degree subchondral bone erosion.