Table 1.

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

Method	Advantages	Disadvantages
Cobb	▪ 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
Nash-Moe	▪ 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
Perdriolle	▪ 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°
Stokes	▪ 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
Aaro-Dahlborn	▪ 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
Ho	▪ 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