[The measurement of the kyphotic angle by contact free registration of back-shape (author's transl)].

Contour line patterns, as they are produced by Moiré Topography are dependent of position, posture and body-shape of the patient. For all medical applications data are needed, which are only dependent of shape and posture and which therefore have to be independent of positioning. Angles between tangents to the body surface are independent of positioning. The measurement of angles in general and the measurement of the inflectional tangent angle in particular is discussed for Moiré topograms. The angle against the grating plane of the Moiré apparatus can be found by calipering the fringe distance in the topogram and comparison with a tangent curve, photographically registered with each topogram (Fig 4). The difference of the two extreme angles along the profile (Fig. 5 a) equals the kyphotic angle. The inflectional points along the profile, where the angles are to be measured, are recognizable by the minimal vertical fringe distance in the topogram (Fig. 6). Although the kyphotic angle refers to the body surface, its definition equals in geometrical terms to that of the Cobb-angle (Fig. 7). A comparison between these two angles in 61 patients (Fig. 8) yields a correlation coefficient of 0.87.