ORAL PRESENTATION Open Access Evaluation of the reproducibility of the formetric 4D measurements for scoliosis Patrick Knott * , Steven Mardjetko, Michelle Rollet, Scott Baute, Magdelina Riemenschneider, Laura Muncie From 7th International Conference on Conservative Management of Spinal Deformities Montreal, Canada. 20-22 May 2010 Introduction Frequent assessment and monitoring of AIS patients is necessary to determine the progression of spinal defor- mity. Radiographs are used as the standard-of-care for evaluation, but have negative long-term effects. Surface topography is a safer option for assessment in these patients. The Formetric 4D (DIERS, International GmbH of Schlangenbad, Germany) provides fast and radiation-free mages of the spine position using surface topography. The goal of this study was to measure the reproducibility of the Formetric 4D system in measuring trunk dimensions and scoliosis Cobb angles. Methods Twelve young adult volunteer patients with the stature of a typical AIS patient were enrolled in the study. The volunteer patients had 30 repeated Formetric 4D mea- surements taken over a period of 1-2 hours on a single day. Two of the patients returned one month later to have the measurement process repeated a second time. Results For each series of 30 measurements, a Standard Deviation was calculated for 12 of the most important parameters, including the Cobb angle measure. The Average Standard Deviation was then calculated by comparing the Standard Deviations from each trial. The following results were obtained (Table 1). The two patients who were measured again one month later had measurements that were very similar. Angular measurements differed by less than one degree in all cases. Distance measurements differed by less than one millimeter in all cases but one. Discussion Surface topography has obvious advantages to repeated radiographs in the adolescent population. If it can deli- ver reliable results, then it should replace radiographs in patients where curve surveillance is necessary and exposure to radiation can be avoided. This study of 12 different patients showed that repeated measure- ments using the Formetric 4D gave very reliable and reproducible measurements with standard deviations that are consistent with those found when taking standing radiographs. Conclusion The Formetric 4D uses surface topography to measure trunk dimensions that are important in the evaluation of scoliosis. These measurements are very reproducible, with standard deviations of only a few degrees for angu- lar measurements and only a few millimeters for Rosalind Franklin University of Medicine and Science, Chicago, USA Full list of author information is available at the end of the article Table 1 Results of reproducibility measurements using Formetric 4D Parameter Average Standard Deviation Range Trunk Length 6.4 mm 2.5 – 15.4 Trunk Imbalance 4.4 mm 2.7 – 6.7 Pelvic Tilt 2.0 degrees 1.2 – 4.8 Thoracic Kyphosis 3.1 degrees 1.8 – 4.4 Kyphosis Depth 6.0 mm 2.9 – 16.3 Lumbar Lordosis 2.3 degrees 1.4 – 4.4 Lordosis Depth 4.4 mm 3.0 – 6.9 Maximal Right Rotation 2.3 degrees 0.9 – 3.8 Maximal Left Rotation 1.3 degrees 0.7 – 2.2 Max Right Lateral Deviation 2.3 mm 1.0 – 4.3 Max Left Lateral Deviation 2.0 mm 0.9 – 3.9 Cobb Angle of Major Curve 3.2 degrees 1.2 – 6.2 Knott et al. Scoliosis 2010, 5(Suppl 1):O10 http://www.scoliosisjournal.com/content/5/S1/O10 © 2010 Knott et al; licensee BioMed Central Ltd.