Segmental deformity markers offer novel indicators of deformity progression risk in deformity-matched adolescent idiopathic scoliosis patients.

PURPOSE: Identification of adolescent idiopathic scoliosis (AIS) patients with mild curvatures who pose significant risk of progressing to severe levels of curvatures is of paramount importance for clinical care. This study aimed to compare segmental deformity changes in AIS sub-cohorts that are dichotomised by progression status. METHODS: Thirty-six female participants with Lenke 1 AIS curves were investigated with sequential MRIs during growth. Scans were reformatted to measure orthogonal segmental parameters, including sagittal/coronal wedging angles and axial rotation angles. Participants were dichotomised by progression. Two-tailed, independent sample t-tests were used to compare sub-cohort multi-segmental and segmental deformity parameters. Measurements were compared at each scan number and variable rates of change were determined using actual time between measures. RESULTS: AIS progression status sub-cohorts were comparable at scan 1 for multi-segmental deformity parameters (e.g. major thoracic curve angle, rib hump, kyphosis) (P > 0.05). However, apical measures of coronal IVD wedging, axial IVD rotation and axial vertebral rotation were segmental parameters at scan 1 which were larger for participants whose AIS would later go on to clinically progress (all P < 0.05). Measures of segmental hypokyphosis were comparable between groups. As development was tracked at each subsequent scan, coronal and axial plane differences between groups increased in both magnitude and number of differences. CONCLUSION: Initial disparity and then subsequent increasing magnitude of change of axial rotation may indicate a higher propensity to clinically progress in the future. This knowledge hopes to provide useful management information for AIS care providers and prognostic education for patients alike. LEVEL OF EVIDENCE: II.

Quantifying Typical Progression of Adolescent Idiopathic Scoliosis: Longitudinal Three-Dimensional MRI Measures of Disk and Vertebral Deformities.

STUDY DESIGN: A prospective cohort study. OBJECTIVE: Detail typical three-dimensional segmental deformities and their rates of change that occur within developing adolescent idiopathic scoliosis (AIS) spines over multiple timepoints. SUMMARY OF BACKGROUND DATA: AIS is a potentially progressive deforming condition that occurs in three dimensions of the scoliotic spine during periods of growth. However, there remains a gap for multiple timepoint segmental deformity analysis in AIS cohorts during development. MATERIALS AND METHODS: Thirty-six female patients with Lenke 1 AIS curves underwent two to six sequential magnetic resonance images. Scans were reformatted to produce images in orthogonal dimensions. Wedging angles and rotatory values were measured for segmental elements within the major curve. Two-tailed, paired t tests compared morphologic differences between sequential scans. Rates of change were calculated for variables given the actual time between successive scans. Pearson correlation coefficients were determined for multidimensional deformity measurements. RESULTS: Vertebral bodies were typically coronally convexly wedged, locally lordotic, convexly axially rotated, and demonstrated evidence of local mechanical torsion. Between the first and final scans, apical measures of coronal wedging and axial rotation were all greater in both vertebral and intervertebral disk morphology than nonapical regions (all reaching differences where P <0.05). No measures of sagittal deformity demonstrated a statistically significant change between scans. Cross-planar correlations were predominantly apparent between coronal and axial planes, with sagittal plane parameters rarely correlating across dimensions. Rates of segmental deformity changes between earlier scans were characterized by coronal plane convex wedging and convexly directed axial rotation. The major locally lordotic deformity changes that did occur in the sagittal plane were static between scans. CONCLUSIONS: This novel investigation documented a three-dimensional characterization of segmental elements of the growing AIS spine and reported these changes across multiple timepoints. Segmental elements are typically deformed from initial presentation, and subsequent changes occur in separate orthogonal planes at unique times.

Adolescent idiopathic scoliosis 3D vertebral morphology, progression and nomenclature: a current concepts review.

PURPOSE: There has been a recent shift toward the analysis of the pathoanatomical variation of the adolescent idiopathic scoliosis (AIS) spine with the three dimensions, and research of level-wise vertebral body morphology in single anatomical planes is now replete within the field. In addition to providing a precise description of the osseous structures that are the focus of instrumented surgical interventions, understanding the anatomical variation between vertebral bodies will elucidate possible pathoaetiological mechanisms of the onset of scoliotic deformity. METHODS: This review aimed to discuss the current landscape of AIS segmental vertebral morphology research and provide a comprehensive report of the typical patterns observed at the individual vertebral level. RESULTS: We have detailed how these vertebrae are typically characterised by lateral wedging to the convexity, have a marked degree of anterior overgrowth, are rotated towards the convexity, have inherent gyratory mechanical torsion created within them and are associated with pedicles on the concave side being narrower, longer and more laterally angled. For the most part, these findings are most pronounced at and around the apex of a scoliotic curve, with these deformations reducing towards junctional vertebrae. We have also summarised a nomenclature defined by the Scoliosis Research Society, highlighting the need for more consistent reporting of these level-wise dimensional anatomical changes. CONCLUSION: Finally, we emphasised how a marked degree of heterogeneity exists between the included investigations, namely in scoliotic curve-type inclusion, imaging modality and timepoint of analysis within scoliosis' longitudinal development, and how improvement in these study design characteristics will enhance ongoing research.

Sequential MRI reveals vertebral body wedging significantly contributes to coronal plane deformity progression in adolescent idiopathic scoliosis during growth.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: To provide a comprehensive, multi-stage investigation of vertebral body (VB) and intervertebral disc (IVD) coronal plane deformities for adolescent idiopathic scoliosis (AIS) patients with a main thoracic curve type, using a series of sequential magnetic resonance images (MRIs). Despite numerous investigations of AIS deformity at the spinal segmental level, there is little consensus as to the major contributor to the lateral curvature of a scoliotic spine. Moreover, scoliotic deformity is often described along a continuum of progression, with few studies having characterised the change in segmental deformity for AIS patients whose deformity progresses clinically over time. METHODS: 30 female AIS patients with primary thoracic curves were included between 2012 and 2016. Three sequential MRIs were captured for each patient. Datasets were reformatted to produce true coronal plane images of the thoracic spine (T4-L1). Overall curve morphology, coronal plane IVD and VB segmental deformity and rates of growth were analysed. RESULTS: Right-side asymmetry was greater in IVDs (18.5 ± 23.9%) when compared to VBs (8.3 ± 9.2%) (P < 0.05) by third scans. Despite this, 77% of patients demonstrated the majority (> 50%) of their coronal curvature was attributed to VB wedging when measured across all three scans. Regardless of progression status, scan number, or region, the sum of the VB wedging angle was greater than the sum of the IVD wedging angle (all P ≤ 0.05). There was no correlation between the rates of major curve angle progression and standing height increase, VB height growth, or IVD height growth (P > 0.05). CONCLUSIONS: VB wedging contributed more to the lateral deformity observed in primary thoracic subtypes of AIS patients than IVD wedging. While IVDs demonstrated the greatest asymmetric deformity, their relatively smaller height resulted in a smaller proportional change in lateral curve angle compared to the VBs. LEVEL OF EVIDENCE: IV.