Changes in trunk appearance following surgical correction of adolescent idiopathic scoliosis.

PURPOSE: To assess the postoperative appearance of the trunk in surgically treated scoliosis patients after a 2 year follow-up using reliable indices and compare the results with 6-month follow-up. METHODS: Forty-six Adolescent Idiopathic Scoliosis (AIS) patients (female; preop mean age 14.4 ± 2.4 years) who underwent a posterior spinal fusion from 2009 to 2018 were included in this study. All had Lenke 1A thoracic curves, with surface topography taken preoperatively, 6 months and 2 years postoperatively. To assess spinal deformity, we measured the proximal thoracic, main thoracic and thoracolumbar/lumbar Cobb angles in the frontal plane from spinal X-rays and inclinometer angles in the thoracic and lumbar regions. To assess trunk deformity, Back Surface Rotation (BSR) and Trunk Lateral Shift (TLS) were computed along the trunk. We analysed the effect of age, height, weight, Cobb angle, length of follow-up, and surgical technique. We also compared correction rates (CRs) of the spinal and trunk measurements after 6 months and 2 years. RESULTS: Good spinal correction was achieved, with Cobb angles decreasing in the whole cohort. CRs for TLS and BSR were positive (denoting improvement) for 76% and 48% of patients, respectively, after 2 years. Compared with 6 months, the mean TLS CR increased while there was no improvement for BSR on average. We found no significant association after 2 years between truncal index CRs and clinical variables (age, height, weight, preoperative Cobb angles) or surgical technique. However, there were significant correlations between the CRs of TLS and the main thoracic Cobb angle (r = 0.35), and between the CRs of BSR and thoracic inclinometer angle. CONCLUSION: Although more than 55% of the TLS was corrected after 2 years of follow-up, the BSR remained stable over time and the persistence of rib hump on the back surface could be observed. LEVEL OF EVIDENCE: III.

Automatic assessment of scoliosis surgery outcome on trunk shape using left-right trunk asymmetry.

PURPOSE: To present a novel set of Left-Right Trunk Asymmetry (LRTA) indices and use them to assess the postoperative appearance of the trunk in Adolescent Idiopathic Scoliosis (AIS) patients. METHODS: We hypothesize that LRTA measurements provide complementary information to existing trunk asymmetry indices when documenting the outcome of scoliosis surgery. Forty-nine AIS patients with thoracic curves who underwent posterior spinal fusion were included. All had surface topography scans taken preoperatively and at least 6 months postoperatively. We documented spinal curvature using Radiographic Cobb angles, scoliometer readings and coronal balance. To evaluate Global Trunk Asymmetry (GTA), we used the standard measures of Back Surface Rotation (BSR) and Trunk Lateral Shift (TLS). To measure LRTA, we identified asymmetry areas as regions of significant deviation between the left and right sides of the 3D back surface. New parameters called Deformation Rate (DR) and Maximum Asymmetry (MA) were measured in different regions based on the asymmetry areas. We compared the GTA and LRTA changes with those in spinal curvature before and after surgery. RESULTS: The GTA indices, mainly TLS, showed improvement for more than 75% of patients. There was significant improvement of LRTA in the shoulder blades and waist regions (95% and 80% of patients respectively). CONCLUSION: We report positive outcomes for LRTA in the majority of patients, specifically in the shoulder blades and waist, even when no reduction of BSR is observed. The proposed indices can evaluate local trunk asymmetries and the degree to which they are improved or worsened after scoliosis surgery.

3D reconstruction of the human trunk for designing personalized braces : Precision study.

The customized design of braces for adolescent idiopathic scoliosis (AIS) treatment requires the acquisition of the 3D external geometry of the patients' trunks. Three body scanning systems are available at CHU Sainte-Justine in Montreal: a fixed system of InSpeck Capturor II LF digitizers and two portable scanners, BodyScan and Structure Sensor. The aim of this study is to compare them by evaluating their accuracy and repeatability. To achieve this, we placed 46 surface markers on an anthropomorphic manikin and scanned it three times with each system. We also measured the 3D coordinates of the same markers using a coordinate measuring machine (CMM), serving as ground-truth. We evaluated the repeatability and accuracy of the three systems: the former, by measuring the bidirectional mean distance between the three surfaces acquired with a given modality; the latter, by calculating the residual normal distance separating each of the 3D surfaces and the CMM point cloud. We also compared texture mapping accuracy between InSpeck and Structure Sensor by examining the CMM point cloud versus the marker 3D coordinates selected on the trunk surface. The results show good accuracy and repeatability for all three systems, with slightly better geometric accuracy for BodyScan (p-value ≈ 10-6). In terms of texture mapping, InSpeck showed better accuracy than Structure Sensor (p-value = 0.0059).

Assessment of Breast Asymmetry in Adolescent Idiopathic Scoliosis Using an Automated 3D Body Surface Measurement Technique.

STUDY DESIGN: Cohort study. OBJECTIVES: To assess breast asymmetry (BA) directly with 3D surface imaging and to validate it using MRI values from a cohort of 30 patients with significant adolescent idiopathic scoliosis (AIS). Also, to study the influence of posture (prone vs standing) on BA using the automated method on both modalities. SUMMARY OF BACKGROUND DATA: BA is a common concern in young female patients with AIS. In a previous study using MRI, we found that the majority of patients with significant AIS experienced BA of up to 21% in addition to their chest wall deformity. MRI is costly and not always readily available. 3D surface topography, which offers fast and reliable breast acquisitions without radiation or distortion of the body surface, is an alternative method in the clinical setting. METHODS: Thirty patients with AIS were enrolled in the study on the basis of their thoracic curvature, skeletal and breast maturity, without regard to their perception of their BA. Each patient underwent two imaging studies of their torso: a 3D trunk surface topography and a breast MRI. An automated breast volume measuring method was proposed using a program developed with Matlab programming. RESULTS: Strong correlations were obtained when comparing the proposed method to the MRI on the left breast volumes (LBV) (r = 0.747), the right breast volumes (RBV) (r = 0.805) and the BA (r = 0.614). Using the same method on both imaging modalities also yielded strong correlation coefficients on the LBV (r = 0.896), the RBV (r = 0.939) and the BA (r = 0.709). CONCLUSIONS: The proposed 3D body surface automated measurement technique is feasible clinically and correlates very well with breast volumes measured using MRI. Additionally, breast volumes remain comparable despite being measured in different body positions (standing and prone) in a young cohort of AIS patients. LEVEL OF EVIDENCE: Level IV.

Evaluation of reducibility of trunk asymmetry in lateral bending.

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.