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The value of the lateral bending test is important in the assessment of spinal curve mobility and prediction of surgical outcome in the treatment of adolescent idiopathic scoliosis (AIS). However, radiographic bending tests are unable to assess the reducibility of trunk asymmetry. This study aims to exploit surface topography measurement in order to evaluate the changes in shape of the trunk (a) between bending and neutral standing positions, and (b) between standing pre- and post-operative visits, in a cohort of adolescents with AIS having undergone surgical correction; and to correlate the differences measured in cases (a) and (b). Our cohort includes 13 patients with right thoracic AIS. Each patient had their 3D trunk surface digitized with a multi-head InSpeck system in standing posture (at the pre-op and post-op visits) and in maximum voluntary right and left bending (at the pre-op visit). We developed a novel trunk shape analysis method which produces a set of inclined trunk cross-sections allowing comparison between different postures. Two asymmetry indices, trunk rotation (TR) and back surface rotation (BSR), were computed in all cases and a statistical analysis was performed. Our correlation study (Pearson test) showed fair correlations in most cases between the changes in side-bending and those post-surgery, with the strongest relationship (p-value < 0.01) when combining the TR measurements from both bendings. These results provide evidence that the bending test can be used to assess trunk asymmetry reducibility. The proposed approach could provide a non-invasive trunk asymmetry reducibility test for routine clinical use in AIS surgery planning. [ABSTRACT FROM AUTHOR]

The value of side bending test is important in the assessment of curve mobility and planning of scoliosis surgery. Our hypothesis is that side-bending test could also assess the reducibility of external asymmetry in the prediction of surgical outcome. However, the current method for analyzing trunk surface topography, based on horizontal cross-sections, is not suitable to side-bending. The purpose of this study was to develop a novel method to analyze the changes in external asymmetry in side-bending. The novel method consists in extracting the back valley curve, then defining cutting planes that are normal to the curve. The intersection between each cutting plane and the trunk surface defines a cross-section to be analyzed. Indices of external trunk asymmetry, such as the rotation of the tangent lines to the back and the rotation of the major axis of the cross-sections, are computed. When visiting the scoliosis clinic for their preoperative evaluation, patients had their 3D trunk surface geometry digitized with a multi-head Inspeck system in standing posture and in maximum voluntary right and left side-bending. For each patient, the surface reconstructions for the 3 acquisitions were analyzed with the proposed method. The standing geometry was also analyzed with the horizontal cross-section method. The resulting curves and indices were coherent with the observed deformations and changes between standing and side-bending. Comparison between the novel approach and the horizontal cross-section-based approach, for standing posture, indicated that the novel one tended to be more representative of the perceived asymmetry. [ABSTRACT FROM AUTHOR]

The value of the lateral bending test is important in the assessment of spinal curve mobility and prediction of surgical outcome in the treatment of adolescent idiopathic scoliosis (AIS). However, radiographic bending tests are unable to assess the reducibility of trunk asymmetry. This study aims to exploit surface topography measurement in order to evaluate the changes in shape of the trunk (a) between bending and neutral standing positions, and (b) between standing pre- and post-operative visits, in a cohort of adolescents with AIS having undergone surgical correction; and to correlate the differences measured in cases (a) and (b). Our cohort includes 13 patients with right thoracic AIS. Each patient had their 3D trunk surface digitized with a multi-head InSpeck system in standing posture (at the pre-op and post-op visits) and in maximum voluntary right and left bending (at the pre-op visit). We developed a novel trunk shape analysis method which produces a set of inclined trunk cross-sections allowing comparison between different postures. Two asymmetry indices, trunk rotation (TR) and back surface rotation (BSR), were computed in all cases and a statistical analysis was performed. Our correlation study (Pearson test) showed fair correlations in most cases between the changes in side-bending and those post-surgery, with the strongest relationship (p-value < 0.01) when combining the TR measurements from both bendings. These results provide evidence that the bending test can be used to assess trunk asymmetry reducibility. The proposed approach could provide a non-invasive trunk asymmetry reducibility test for routine clinical use in AIS surgery planning.

The purpose of this study was to evaluate the 3D reconstruction accuracy of a new technology that allows the acquisition of the whole trunk and to develop a software to analyse the trunk surface asymmetry. A non-invasive active vision system provides a 3D textured reconstruction of the whole trunk. The analysis system provides the clinician with quantitative indices that characterize the whole external trunk asymmetry.