To decrease the influence of postural sway during spinal measurements, an instrumented fixation posture (called G) was proposed and tested in comparison with the free standing posture (A) using the DTP-3 system in a group of 70 healthy volunteers. The measurement was performed 5 times on each subject and each position was tested by a newly developed device for non-invasive spinal measurements called DTP-3 system. Changes in postural stability of the spinous processes for each subject/the whole group were evaluated by employing standard statistical tools. Posture G, when compared to posture A, reduced postural sway significantly in all spinous processes from C3 to L5 in both the mediolateral and anterioposterior directions. Posture G also significantly reduced postural sway in the vertical direction in 18 out of 22 spinous processes. Importantly, posture G did not significantly influence the spinal curvature.

Aims:The accuracy of non-radiographic measurement of the spinal shape is infl uenced by postural sway (PS). The aim of this study was to determine whether certain examination postures prevent PS without changing key spinal characteristics.Methods: We tested 1) natural standing position (posture A), 2) fi xation postures standing with the support of the upper limbs against a wall (posture B) and 3) standing with the support of the head and chest against a wall (posture C). There were examined 60 subjects; the examination of each posture was repeated fi ve times in each individual by DTP-3 microcomputer position system. The spinal shape changes resulting from tested postures were assessed using t-test. The role of PS was assessed using standard deviations, and the signifi cance of diff erences between the individual postures was determined using the F-test.Results: Compared to posture A, the fi xation posture B did not have any signifi cant infl uence on the degree of PS, but it signifi cantly infl uenced the shift of the spine from the ideal vertical and its slope, although this did not result in spine curve deformation. The fi xation posture C signifi cantly reduced the PS compared to posture A; however, there were signifi cant changes in the spinal shape. This fi xation posture shifted signifi cantly the spine from the ideal vertical and slope characteristics.Conclusion: PS plays a role in the examination of spinal shape. Positions B and C did not meet the required criteria. Therefore, it is necessary to search for another examination position.

PURPOSE OF THE STUDYRepeated measurements of the spine are absolutely necessary in children and adolescents affected by spinal deformities especially during their growing-up periods. To avoid risks of tissue damage from x-ray exposure, several methods for non-invasive measurement of the spinal curvature have been developed. One of them is the DTP-3 position system allowing for a three-dimensional measurement of anatomical landmarks (spinous processes) and the calculation of curvature angles in both the frontal and sagittal planes. We were interested to know whether the DTP-3 was precise enough to determine the true spinal curvature. MATERIAL AND METHODSTo determine the precision of the DTP-3 system, we constructed a model of the spine. The model was then repeatedly investigated by both the noninvasive and x-ray methods. The distortion of x-ray images caused by the central projection mechanism was considered and included in the calculation. In addition, a group of patients with scoliosis up to 40° was evaluated by both the DTP-3 system and x-ray (the latter according to Cobb's method). RESULTSDifferences in spatial coordinates between DTP-3 and x-ray examinations reached 20.9 mm in the frontal plane and 67.3 mm in the sagittal plane without distortion correction of x-ray images. The differences decreased below 1.5 mm after image distortion correction in each plane. Distortion correction had not the same effect for angle parameters as for coordinates. Differences between the DTP-3 angle parameters and Cobb's x-ray angles were below 4.7°, both without correction and after correction. The difference between DTP-3 angle parameters and Cobb's x-ray angles was -1.8° ± 3.0° (mean ± standard deviation) when measurement was performed on the patients with scoliosis. DISCUSSIONThe goal of any clinical examination is to obtain data applicable to decision-making analysis. In the case of scoliosis it is necessary to report results in terms of Cobb's angle, which is the problem for all surface-dependent methods, especially in patients with double curves. A solution may be to define the maximal difference between noninvasive and x-ray methods that could be acceptable for good clinical practice. CONCLUSIONSIn this study we report good concordance between noninvasive and x-ray examinations of a modeled spinal deformity in terms of both angle and linear measurements. The same results were obtained for angle measurements in a group of patients with scoliosis up to 40°. Based on this study and our previous data we believe that the DTP-3 system can be introduced into clinical practice.