Prediction of transitional lumbosacral anatomy on magnetic resonance imaging of the lumbar spine

AIM:To evaluate two simple angle measurements for predicting lumbosacral transitional vertebra(LSTV) in magnetic resonance imaging(MRI) studies of the spine.METHODS:The lumbar spine MRI studies of 50 subjects with LSTV and 50 subjects with normal lumbosacral anatomy were retrospectively evaluated.In each study,the mid-sagittal T2-weighted image was used to measure the angle formed by a line parallel to the superior surface of the sacrum and a line perpendicular to the axis of the scan table(A-angle),as well as the angle formed by a line parallel to the superior endplate of the L3 vertebra and a line parallel to the superior surface of the sacrum(B-angle).RESULTS:The total study population consisted of 100 subjects(46 males,54 females,51 ± 16 years old).There were no differences in age and sex between the two groups.Both A-angle and B-angle were significantly increased in subjects with LSTV compared to controls(P < 0.05).The optimal cut-off values of A-angle and B-angle for the prediction of LSTV were 39.8°(sensitivity = 80%,specificity = 80%,accuracy = 83%;95% confidence interval = 74%-89%,P = 0.0001) and 35.9°(sensitivity = 80%,specificity = 54%,accuracy = 69%;95% confidence interval = 59%-78%,P = 0.0005),respectively.CONCLUSION:On sagittal MR images of the lumbar spine,an increased A-angle and/or B-angle should alert the radiologist to the presence of LSTV.