Comparison of Radiographic and Surface Topography Measurements in Adolescents with Idiopathic Scoliosis

Jason M Frerich§, 1, *, Kristen Hertzler§, 1, Patrick Knott 1, Steven Mardjetko 2
1 Rosalind Franklin University of Medicine and Science – Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA
2 Illinois Bone and Joint Institute, 9000 Waukegan Road, Morton Grove, IL 60053, USA

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© Frerich et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA; Tel: (515) 707-3553; Fax: (847) 578-8690; E-mail:
§ Demarcates co-authorship.



In patients with adolescent idiopathic scoliosis (AIS), radiographic surveillance is the gold standard of assessing spinal deformity, but has negative long-term effects. The Formetric 4D surface topography system was compared to standard radiography as a safer option for evaluating patients with AIS.


Fourteen volunteers with typical AIS patient stature had 30 repeated Formetric 4D measurements taken, and reproducibility was assessed. Sixty-four patients with AIS were then enrolled during routine clinic visits. Evaluation included standard radiographs and surface topography measurements. A comparison analysis was performed.


When assessing same-day repeated scans, a standard deviation of +/- 3.4 degrees for scoliosis curve measurements was determined, and the Reliability Coefficient (Cronbach) was very high (0.996). Cobb angles measured with the Formetric 4D differed from radiographic measurements by an average of 9.42 (lumbar) and 6.98 (thoracic) degrees, while the correlation between the two measurements was strong (95% confidence interval [CI]), 0.758 (lumbar) and 0.872 (thoracic) respectively.


The Formetric 4D is comparable to radiography in terms of its test-retest reproducibility. Although this device does not predict curve magnitude exactly, the predictions correlate strongly with the Cobb angles determined from radiographs. It can be reliably used in the surveillance of patients with AIS.

Keywords: Scoliosis, radiography, surface topography, surveillance, comparison.