Sagittal curvature of the spine as a predictor of the pediatric spinal deformity development

Current models to understand the onset and progression of scoliotic deformities in adolescent idiopathic scoliosis: a systematic review

PURPOSE

To create an updated and comprehensive overview of the modeling studies that have been done to understand the mechanics underlying deformities of adolescent idiopathic scoliosis (AIS), to predict the risk of curve progression and thereby substantiate etiopathogenetic theories.

METHODS

In this systematic review, an online search in Scopus and PubMed together with an analysis in secondary references was done, which yielded 86 studies. The modeling types were extracted and the studies were categorized accordingly.

RESULTS

Animal modeling, together with machine learning modeling, forms the category of black box models. This category is perceived as the most clinically relevant. While animal models provide a tangible idea of the biomechanical effects in scoliotic deformities, machine learning modeling was found to be the best curve-progression predictor. The second category, that of artificial models, has, just as animal modeling, a tangible model as a result, but focusses more on the biomechanical process of the scoliotic deformity. The third category is formed by computational models, which are very popular in etiopathogenetic parameter-based studies. They are also the best in calculating stresses and strains on vertebrae, intervertebral discs, and other surrounding tissues.

CONCLUSION

This study presents a comprehensive overview of the current modeling techniques to understand the mechanics of the scoliotic deformities, predict the risk of curve progression in AIS and thereby substantiate etiopathogenetic theories. Although AIS remains to be seen as a complex and multifactorial problem, the progression of its deformity can be predicted with good accuracy. Modeling of AIS develops rapidly and may lead to the identification of risk factors and mitigation strategies in the near future. The overview presented provides a basis to follow this development.

22q11.2 Deletion Syndrome as a Human Model for Idiopathic Scoliosis

To better understand the etiology of idiopathic scoliosis, prospective research into the pre-scoliotic state is required, but this research is practically impossible to carry out in the general population. The use of ‘models’, such as idiopathic-like scoliosis established in genetically modified animals, may elucidate certain elements, but their translatability to the human situation is questionable. The 22q11.2 deletion syndrome (22q11.2DS), with a 20-fold increased risk of developing scoliosis, may be a valuable and more relevant alternative and serve as a human ‘model’ for idiopathic scoliosis. This multicenter study investigates the morphology, dynamic behavior, and presence of intraspinal anomalies in patients with 22q11.2DS and scoliosis compared to idiopathic scoliosis. Scoliosis patients with 22q11.2DS and spinal radiography (n = 185) or MRI (n = 38) were included (mean age 11.6 ± 4.2; median Cobb angle 16°) and compared to idiopathic scoliosis patients from recent literature. Radiographic analysis revealed that 98.4% of 22q11.2DS patients with scoliosis had a curve morphology following predefined criteria for idiopathic curves: eight or fewer vertebrae, an S-shape and no inclusion of the lowest lumbar vertebrae. Furthermore, curve progression was present in 54.2%, with a mean progression rate of 2.5°/year, similar to reports on idiopathic scoliosis with 49% and 2.2–9.6°/year. The prevalence of intraspinal anomalies on MRI was 10.5% in 22q11.2DS, which is also comparable to 11.4% reported for idiopathic scoliosis. This indicates that 22q11.2DS may be a good model for prospective studies to better understand the etiology of idiopathic scoliosis.

Quantitative imaging of the spine in adolescent idiopathic scoliosis: shifting the paradigm from diagnostic to comprehensive prognostic evaluation

PURPOSE

We aimed to provide a perspective review of the available quantitative imaging modalities of the spine for prognostic evaluation of the adolescent idiopathic scoliosis (AIS).

METHODS

A technical description of the current imaging technologies for quantitative assessment of the pediatric spine with scoliosis was provided, and the pros and cons of each method were discussed. Imaging modalities that quantify the overall 3D alignment of the spine as well as the structural specification of the spinal bone, intervertebral disc, endplates, and ligaments as it pertains to development and progression of the idiopathic spinal deformities in adolescents were discussed.

RESULTS

Low-dose and microdose stereoradiography, ultrasound, and rasterstereography provide quantitative imaging of the 3D spinal alignment with low or no radiation in standing posture which allows repetitive imaging for early detection of the curve development. Quantitative magnetic resonance imaging, including ultrashort dual-echo time and T1-rho can provide quantitative assessment of the spinal tissues relevant to development of idiopathic spinal deformity in pediatric population. New computed tomography scans that uses dual-energy can provides high-resolution measure of the current-state of the bone quality and morphology as well as the osteogenic properties of the bone by quantitative evaluation of the bone marrow.

CONCLUSION

The presented imaging modalities can provide a wide spectrum of quantifiable information relevant to development and progression of the spinal deformity. Clinical application of these technologies can change the paradigm in clinical assessment of the pediatric scoliosis by improving our understanding of the pathogenesis of the idiopathic scoliosis.