Comparison of Cobb angles in idiopathic scoliosis on standing radiographs and supine axially loaded MRI.
METHODS
Prospective, patient controlled.


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


BACKGROUND
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 degrees 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 degrees on standing radiographs, 23 degrees on nonloaded supine MRI, and 31 degrees on supine loaded MRI. Axially loaded, compared with nonloaded, MRI increased the Cobb angle by 8 degrees. The mean difference between standing radiograph and supine axially loaded MRI was 0 degrees, with an intermethodologic variation(s) of 3.4 degrees. 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.
Wessberg
Per
P
Department of Orthopaedics, Sahlgren University Hospital, Göteborg, Sweden. per.wessberg@vgregion.se
Danielson
Barbro I
BI
Willén
Jan
J
D000293:Adolescent; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011187:Posture; D011446:Prospective Studies; D011859:Radiography; D012600:Scoliosis / Q000175:diagnosis* / Q000000981:diagnostic imaging