Infantile Scoliosis Workup

Updated: Nov 01, 2019
  • Author: Palaniappan Lakshmanan, MBBS, MS, AFRCS, FRCS(Tr&Orth); Chief Editor: Jeffrey D Thomson, MD  more...
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Workup

Radiography

Radiographs of the spine in infants are taken with the child held up by the arms. Because the patients are very young, radiographs usually are obtained either with a parent holding the child or with the use of a pediatric immobilizer and positioner (eg, Pigg-O-Stat). The severity of the scoliosis is established by calculating the rib-vertebral angle difference (RVAD) in the radiographs (see the image below). [11]

RVAD (rib-vertebral angle difference) measurement RVAD (rib-vertebral angle difference) measurement at apical vertebra: RVAD = b - a (concave - convex side).

The rib-vertebral angle is measured by (1) drawing a line perpendicular to the middle of the upper or lower border of the apical vertebrae of the curve and then (2) measuring the angle this line makes with medial extension of another line drawn from the midpoint of the head to the midpoint of the neck of the rib, just medial to the beginning of the shaft of the rib. The difference between the right side and the left side (ie, between the concave side and the convex side) is the RVAD.

The apical vertebrae are the vertebrae at the curve of the apex. If there are the same number of vertebrae between the superior and the inferior end vertebrae, there will be two apical vertebrae.

Radiographs and RVAD calculations should be repeated every 2-3 months to determine whether the curve is progressing or regressing.

Anteroposterior (AP) radiographs may also be used to evaluate the severity of the curve; however, they may not be accurate, because they assess a three-dimensional (3D) deformity in a two-dimensional (2D) projection. Still, they provide a reasonable estimation of severity and hence are used commonly in the evaluation of scoliosis.

The angle between the superior endplate of the superior end vertebra and the inferior endplate of the inferior end vertebra is assessed. Because lines drawn along these endplates normally pass beyond the edge of the radiograph, a second set of lines is drawn perpendicular to these lines, and the angle subtended between them is measured; this is the Cobb angle (see the image below).

Preoperative scoliogram showing Cobb angle. Preoperative scoliogram showing Cobb angle.

The end vertebrae are the most superior and inferior vertebrae in the curve; they are differentiated by the opening of the intervertebral disk space caused by crowding on the concave surface. These vertebrae are the least displaced and rotated, and they have maximally tilted endplates. [12, 13]

A study by Redding et al reviewed the frequency of asymmetric lung perfusion and ventilation in children with congenital or infantile thoracic scoliosis before surgical treatment and the relation between the Cobb angle and asymmetry of lung function. [14] In this study, asymmetric ventilation and perfusion between the right and left lungs occurred in more than half of the children with severe congenital and infantile thoracic scoliosis, but the severity of this asymmetry did not relate to Cobb angle measurements. Asymmetry in lung function was influenced by deformity of the chest wall in multiple dimensions and could not be ascertained by chest radiography alone.

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Computed Tomography

Computed tomography (CT) can be used to get a detailed picture of the scoliosis curve. Because spinal fusion is a major surgical treatment modality, patients must be assessed with respect to their ability to withstand a major surgical procedure, and tests must be done for hemoglobin level and respiratory function. [15]

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Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is necessary in moderate-to-severe infantile scoliosis because the reported frequency of neural axis abnormalities associated with infantile scoliosis has been high (21-50% in some sources). The common abnormalities are Arnold-Chiari type I malformation and syringomyelia. Hence, whole-spine MRI is indicated before surgery. The current recommendation is for patients with infantile scoliosis with a Cobb angle greater than 20º.

In a retrospective case series assessing MRI findings in 54 patients with presumed infantile idiopathic scoliosis, [16] a neural axis abnormality was revealed in seven patients (13%), of whom five (71.4%) required neurosurgical intervention. Tethered cord requiring surgical release was identified in three patients, Chiari malformation requiring surgical decompression in two, and a small nonoperative syrinx in two. The authors concluded that close observation may be a reasonable alternative to an immediate screening MRI in patients presenting with presumed infantile idiopathic scoliosis and a curve greater than 20º.

A study by Zhang et al used MRI to examine 504 infantile and juvenile patients diagnosed with "presumed idiopathic" scoliosis for neural axis abnormalities. [17]  Such abnormalities were found in 94 of the 504 patients (18.7%). The authors concluded that routine MRI evaluation appeared to be warranted for patients with "presumed idiopathic" scoliosis if they were younger than 10 years, were male, or had a left thoracic or right lumbar curve. 

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