Table 1 Advantages and disadvantages associated with radiographic and CT methods of rotation measurement

▪ Simple procedure

▪ No means to quantify rotation from gradation scheme

▪ Little patient exposure to radiation (one anteroposterior radiograph)

▪ Distortion of spinous process tip in scoliotic vertebrae may decrease accuracy

▪ Limited visibility of spinous process on radiographs of vertebrae with large rotation

▪ Position of pedicles are less affected by intravertebral rotation; more reliable landmark for measuring rotation

▪ Provides over-estimation of rotation (can be adjusted by 10° as suggested by Drerup)

▪ Pedicles are poorly visible on vertebrae rotated severely or on spines with surgical instrumentation

▪ Affordable

▪ Difficulty in making precise markings on radiographs – a 2 mm error corresponds to 5° rotation

▪ Non-invasive

▪ Simple procedure

▪ Little patient exposure to radiation (one anteroposterior radiograph)

▪ Reduced accuracy when measuring large degrees of rotation

▪ General findings report accurate measurements to within ± 5°

▪ Accounts for three-dimensionality of vertebra; similar accuracy to stereoradiograph

▪ Greater random error in comparison to methods involving marking of vertebral edges

▪ Little exposure to radiation

▪ Simple measuring procedure

▪ Better measurement accuracy even when measuring vertebrae tilted in the coronal and saggital planes

▪ More difficult to use for inexperienced observers due to less obvious landmark definitions

▪ Clearly defined reference points; simple procedure

▪ Less correlation to actual rotation value when measuring distorted and

▪ Better interobserver reliability in comparison to Aaro-Dahlborn method when assessing normal vertebrae

tilted vertebrae; less applicable in realistic conditions