Study design: A retrospective cross-sectional review studied the posteroanterior and lateral bending radiographs of 26 preoperative patients with thoracic major adolescent idiopathic scoliosis.
Objective: To characterize the relation of vertebral axial rotation, apparent vertebral wedging, and disc wedging with lateral bending in patients with severe adolescent idiopathic scoliosis.
Summary of background data: Lateral bending radiographs are used commonly in surgical planning to assess the flexibility of the spine and to establish the placement of instrumentation. However, their use in the assessment of motion in the axial plane has not been clearly established.
Methods: Data were collected retrospectively from 26 subjects immediately before spinal surgery. All the subjects had adolescent idiopathic scoliosis with right thoracic major curves. Axial rotation, vertebral wedging, and disc wedging were measured from T4 to L4 on left and right supine bending and standing posteroanterior radiographs. The apexes of the major and minor curves, the neutral vertebrae, and the Cobb angles were recorded.
Results: No significant differences in axial rotation were found at the thoracic apex, neutral vertebrae, or lumbar apex in response to lateral bending. Most of the wedging occurs in the disc, and is maximal at the apex of the curve. The total amount of wedging was higher in more severe curves.
Conclusions: Lateral bending does not improve axial rotation in severe scoliosis (scoliosis for which surgical correction is advised). Structural changes including disc and vertebral wedging may be responsible for the lack of rotational correction of the scoliotic spine. Lack of axial flexibility in the thoracic region may hamper surgical attempts to correct the deformities of the trunk.