Multilevel analysis of trunk surface measurements for noninvasive assessment of scoliosis deformities

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.

Spectral Shape Analysis of Human Torsos: Application to the Evaluation of Scoliosis Surgery Outcome

This paper aims at evaluating the effect of spinal surgery on the torso shape appearance of adolescent patients. Current methods that assess the surgical outcome on the trunk shape are limited to its global asymmetry or rely on unreliable manual measurements. We introduce a novel framework to evaluate pre- to postoperative local asymmetry changes using a spectral representation of the torso shape, more specifically, the Laplacian spectrum (eigenvalues and eigenvectors) of a graph. We conduct a statistical analysis on the eigenvalues to efficiently select the spectral space and determine the significant components between preop and postop groups. On the selected eigenvectors, we propose a local analysis based on the concept of Euler characteristic to detect their local maxima and minima, which are then used to compute local left-right (L-R) asymmetries of torso shape. On 49 patients with a thoracic spinal deformity, the method captures significant pre- to postoperative changes of asymmetry at the waist, shoulder blades, shoulders, and breasts. We have evaluated average correction rates for L-R asymmetry of the waist height (67%), shoulder-blade height (64%) and depth (67%), lateral offset between shoulder and neck (61%), and breast height (52%). Spectral torso shape analysis provides a novel approach to quantify the surgical correction of the scoliotic trunk from local shape asymmetry. The proposed method could help the surgeon to understand the impact of different spinal surgery strategies on the postoperative appearance and choose the one that should provide better patient's satisfaction.

Application of an RGBD augmented C-arm for minimally invasive scoliosis surgery assistance

Minimally invasive surgeries (MISs) are gaining popularity as alternatives to conventional open surgeries. In thoracoscopic scoliosis MIS, fluoroscopy is used to guide pedicle screw placement and to visualise the effect of the intervention on the spine curvature. However, cosmetic external appearance is the most important concern for patients, while correction of the spine and achieving coronal and sagittal trunk balance are the top priorities for surgeons. The authors present the feasibility study of the first intra-operative assistive system for scoliosis surgery composed of a single RGBD camera affixed on a C-arm which allows visualising in real time the surgery effects on the patient trunk surface in the transverse plane. They perform three feasibility experiments from simulated data based on scoliotic patients to live acquisition from non-scoliotic mannequin and person, all showing that the proposed system accuracy is comparable with scoliotic surface reconstruction state of art.

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.

Changes in Trunk Appearance After Scoliosis Spinal Surgery and Their Relation to Changes in Spinal Measurements

STUDY DESIGN

Retrospective study of surgical outcome.

OBJECTIVES

To evaluate quantitatively the changes in trunk surface deformities after scoliosis spinal surgery in Lenke 1A adolescent idiopathic scoliosis (AIS) patients and to compare it with changes in spinal measurements.

SUMMARY OF BACKGROUND DATA

Most studies documenting scoliosis surgical outcome used either radiographs to evaluate changes in the spinal curve or questionnaires to assess patients health-related quality of life. Because improving trunk appearance is a major reason for patients and their parents to seek treatment, this study focuses on postoperative changes in trunk surface deformities. Recently, a novel approach to quantify trunk deformities in a reliable, automatic, and noninvasive way has been proposed.

METHODS

Forty-nine adolescents with Lenke 1A idiopathic scoliosis treated surgically were included. The back surface rotation and trunk lateral shift were computed on trunk surface acquisitions before and at least 6 months after surgery. We analyzed the effect of age, height, weight, curve severity, and flexibility before surgery, length of follow-up, and the surgical technique. For 25 patients with available three-dimensional (3D) spinal reconstructions, we compared changes in trunk deformities with changes in two-dimensional (2D) and 3D spinal measurements.

RESULTS

The mean correction rates for the back surface rotation and the trunk lateral shift are 18% and 50%, respectively. Only the surgical technique had a significant effect on the correction rate of the back surface rotation. Direct vertebral derotation and reduction by spine translation provide a better correction of the rib hump (22% and 31% respectively) than the classic rod rotation technique (8%). The reductions of the lumbar Cobb angle and the apical vertebrae transverse rotation explain, respectively, up to 17% and 16% the reduction of the back surface rotation.

CONCLUSIONS

Current surgical techniques perform well in realigning the trunk; however, the correction of the deformity in the transverse plane proves to be more challenging. More analysis on the positive effect of vertebral derotation on the rib hump correction is needed.

LEVEL OF EVIDENCE

III.

Is Breast Asymmetry Present in Girls with Adolescent Idiopathic Scoliosis?

STUDY DESIGN

Cross-sectional descriptive study.

OBJECTIVES

To characterize breast asymmetry (BA), as defined by breast volume difference, in girls with significant adolescent idiopathic scoliosis (AIS), using magnetic resonance imaging (MRI).

SUMMARY AND BACKGROUND

BA is a frequent concern among girls with AIS. It is commonly believed that this results from chest wall deformity. Although many women exhibit physiological BA, the prevalence is not known in adolescents and it remains unclear if it is more frequent in AIS. Breasts vary in shape and size and many ways of measuring them have been explored. MRI shows the highest precision at defining breast tissue.

METHODS

Thirty patients were enrolled on the basis of their thoracic curvature, skeletal and breast maturity, without regard to their perception on their BA. MRI acquisitions were performed in prone with a 1.5-Tesla system using a 16-channel breast coil. Segmentation was achieved using the ITK-SNAP 2.4.0 software and subsequently manually refined.

RESULTS

The mean left breast volume (528.32 ± 205.96 cc) was greater compared with the mean right breast volume (495.18 ± 170.16 cc) with a significant difference between them. The mean BA was found to be 8.32% ± 6.43% (p < .0001). A weak positive correlation was observed between BA and thoracic Cobb angle (0.177, p = .349) as well as thoracic gibbosity angle (0.289, p = .122). The left breast was consistently larger in 65.5% of the patients. Twenty patients (66.7%) displayed BA ≥5%.

CONCLUSIONS

We have described BA in patients with significant AIS using MRI. This method is feasible, objective, and very precise. The majority of patients had a larger left breast, which could compound the apparent BA secondary to trunk rotation. In many cases, BA is present independently of thoracic deformity. This knowledge will assist in counseling AIS patients in regards to their concerns with BA.

Non invasive clinical assessment of trunk deformities associated with scoliosis

Besides the spinal deformity, scoliosis modifies notably the general appearance of the trunk resulting in trunk rotation, imbalance and asymmetries which constitutes patients' major concern. Existing classifications of scoliosis, based on the type of spinal curve as depicted on radiographs, are currently used to guide treatment strategies. Unfortunately, even though a perfect correction of the spinal curve is achieved, some trunk deformities remain, making patients dissatisfied with the treatment received. The purpose of this study is to identify possible shape patterns of trunk surface deformity associated with scoliosis. First, trunk surface is represented by a multivariate functional trunk shape descriptor based on 3D clinical measurements computed on cross sections of the trunk. Then, the classical formulation of hierarchical clustering is adapted to the case of multivariate functional data and applied to a set of 236 trunk surface 3D reconstructions. The highest internal validity is obtained when considering 11 clusters that explain up to 65% of the variance in our dataset. Our clustering result shows a concordance with the radiographic classification of spinal curves in 68% of the cases. As opposed to radiographic evaluation, the trunk descriptor is three-dimensional and its functional nature offers a compact and elegant description of not only the type, but also the severity and extent of the trunk surface deformity along the trunk length. In future work, new management strategies based on the resulting trunk shape patterns could be thought of in order to improve the esthetic outcome after treatment, and thus patients satisfaction.