Progression of Sagittal plane deformity and axial vertebral rotation in adolescent idiopathic scoliosis using magnetic resonance imaging (original) (raw)

Adolescent Idiopathic Scoliosis (AIS) is a three-dimensional (3D) spinal deformity affecting 0.47-5.2% of the population and is up to ten times more common in females than males. Although there are multiple types of scoliosis, AIS is the most prevalent type, accounting for 80% of cases. With increased severity of the scoliotic curve, some patients will require treatment either with bracing or spinal instrumentation, with the latter being associated with significant risks and reduced spinal flexibility. For this reason, early diagnosis and sound understanding of the 3D pathoanatomy associated with AIS, is paramount in optimal treatment outcomes. Few studies have analysed multi-dimensional anatomical changes in the vertebrae in a large cohort and prospectively over a period of time. To understand how the sagittal and axial plane deformity changes with curve progression, this study used a sequential series of magnetic resonance images (MRI) for both AIS participants and non-scoliotic controls. Wedge angles, vertebral body (VB) heights, axial vertebral rotation (AVR) and thoracic kyphosis were compared at three time-points during adolescent growth. This study found a significant hypokyphosis already evident at MRI scan 1 in the AIS cohort, and subsequent reduction or very modest increase in kyphosis over the subsequent MRI scans, when compared to non-scoliotic control participants. Further contributing factors to the scoliotic deformity include a failure of progression of an anterior wedge of VBs and a relative slower growth rate of the posterior VB height. There was an observed reduction in axial vertebral rotation (AVR) three levels above and below the apex of the curve which may indicate the transition to a compensatory curve in the scoliotic deformity. Intravertebral rotation (IVR) had a greater progressive change at periapical levels when compared to the apex, which may contribute to the non-uniform de-rotation achieved following instrumented fusion surgery. Overall this study contributes to the understanding of spinal deformity progression in AIS patients, which will hopefully aid in therapeutic planning and optimise treatment outcomes.