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Comparison of Cobb Angles in Idiopathic Scoliosis on Standing Radiographs and Supine Axially Loaded MRI

Wessberg, Per MD*; Danielson, Barbro I. MD, PhD; Willén, Jan MD, PhD*

doi: 10.1097/01.brs.0000249513.91050.80
Diagnostics

Study Design. Prospective, patient controlled.

Objective. To compare Cobb angles in idiopathic scoliosis between standing radiographs and a nonradiographic procedure.

Summary of Background Data. Repeated radiographic examinations at young age may increase the risk for breast cancer in adulthood. MRI images the spine satisfactorily but is cumbersome in standing. A harness supplying axial load to a lying subject simulates the standing radiograph appearance of the lumbar spine.

Methods. Thirty patients with idiopathic scoliosis greater than 20° performed a routine posteroanterior and lateral standing thoracolumbar spine radiograph and an MRI in supine position without and with axial loading.

Results. Mean Cobb angle for the major curve was 31° on standing radiographs, 23° on nonloaded supine MRI, and 31° on supine loaded MRI. Axially loaded, compared with nonloaded, MRI increased the Cobb angle by 8°. The mean difference between standing radiograph and supine axially loaded MRI was 0°, with an intermethodologic variation(s) of 3.4°. Radiographic and MRI (axially loaded) Cobb angles correlated positively (r = 0.78).

Conclusions. Axial loading on supine MRI produces coronal Cobb angles similar to standing radiographs. This is a way to acquire reliable Cobb angles without radiation in the monitoring of idiopathic scoliosis.

Children and adolescents with idiopathic scoliosis are exposed to repeated radiographic examinations, which may pose risks for serious pathologies later in life. Supine MRI with axial loading gives similar Cobb angles as standing radiographs. This may be a way to follow scoliosis patients without exposure to radiation.

From the Departments of *Orthopaedics and †Radiology, Sahlgren University Hospital, Göteborg, Sweden.

Acknowledgment date: October 12, 2005. First revision date: February 2, 2006. Acceptance date: February 20, 2006.

Supported by the Bertha Neuberg Research Fund and the Wallenberg Foundation.

The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.

Foundation funds were received in support of this work. One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., royalties, stocks, stock options, decision making position.

Address correspondence and reprint requests to Per Wessberg, MD, Department of Orthopaedics, Sahlgren University Hospital, S-41345 Göteborg, Sweden; E-mail: per.wessberg@vgregion.se

© 2006 Lippincott Williams & Wilkins, Inc.