[Trunk deformity in scoliosis studied by surface measurement]

Ihe three-dimensional back surface shape of 504 patients with untreated idiopathic scoliosis was studied using moiré topography. A new system for the quantitative analysis of moiré pictures was developed with the aid of a still video photo system and microcomputer system. With these systems, the outcome of the analysis can be obtained immediately at the clinical scene. Using a positioning device that restrained the movement of the patient's pelvis at the time of taking the moiré picture, the reproducibility error was very small. The relationship of the parameters from the surface measurements with the radiographic appearance was then examined. The hump sum (HS), that is the sum total of the hump indices on three levels of the back was used as an index that represented the severity of the trunk deformity. It was possible to estimate objectively from HS, the correction in trunk deformity obtained after treatment. There was a relatively weak but statistically significant number of cases in which the degree of hump and that of the lateral curvature did not agree. Those within the range of one standard deviation from the regression line were defined as the standard rotation group, and those out of this range as the nonstandard rotation group. In the standard rotation group, the progression in curvature could be detected by moiré analysis so that exposure to radiation could be reduced. In the nonstandard rotation group, radiographic examination remained necessary, although the magnitude of the trunk deformity itself could be estimated more accurately by HS. The discrepancy between the HS and the Cobb angle suggested that scoliosis and rib deformity were independent from each other, and therefore they should be evaluated separately.