Evaluating Spinal Deformity Using Surface Topography By Patrick Knott, PhD, PA- C, and Marcel Betsch, MD

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1 Evaluating Spinal Deformity Using Surface Topography By Patrick Knott, PhD, PA- C, and Marcel Betsch, MD WP Bunnell described the scoliometer in 1984 as a simple, reliable, and inexpensive measurement of trunk asymmetry that was related to the deformity of scoliosis. (1) This asymmetry, which was caused by the rotation and deformity of the rib cage, was related to the magnitude of the scoliosis curve, although the correlation between trunk rotation and Cobb Angle is not very strong, ranging from 0.3 to 0.5 in published studies (2, 3). Use of the scoliometer is now widespread, however, in screening for scoliosis and determining which patients need orthopaedic and radiographic follow- up. This surface topography evaluation has proven to be a useful clinical tool, and has led to more research work in the field. Moiré topography (also referred to as rasterstereography) is a mathematical technique for reproducing the contour of a surface by studying the distortion of a grid that is projected on it. This technique was developed in the 1960 s, and was used by medical researchers beginning in the mid 1980 s. Early systems projected a grid of light onto a subject s back, and took a photo. This photo was then digitized and analyzed by computer software to produce a topographical model. The prediction of the shape of the spinal deformity using surface landmarks was first described by Turner- Smith, Harris et al, and produced strong correlational models of prediction (4). The analysis was initially slow and burdensome, and did not lend itself to efficient use by those in clinical practice. As computer capability improved, however, the analytical power of this technology became more evident. Two early systems, ISIS and Quantec, developed computer models that estimated radiographic Cobb Angles using surface topography data. Correlations were good (r = 0.8 and tended to be within 10 degrees of the radiographic measurements (5). The formetric system was first developed at the University of Muenster, and then taken commercial by the DIERS company (Schlangenbad, Germany) in the mid 1990 s using a sophisticated evaluation of the surface topography of the trunk. A more complex mathematical model that correlated the topographic scan with nearly 500 reference radiographs of the spine was developed by Drerup and Hierholzer in Muenster (6,7). This was used to produce an accurate 3D reconstruction of the subject s spinal column from the topographic image that is taken. Validation of this model was done by the DIERS company over many years of research in partnership with several international and German universities (8). Early studies showed that the formetric system could accurately locate anatomic landmarks on the human body (10, 11, 12) and subsequent research demonstrated that the system was able to more accurately find those landmarks than even an experienced clinician could (13). Studies from the University Muenster showed that the accuracy of rasterstereography in patients with idiopathic scoliosis with Cobb <50 degrees is excellent and even in patients with Cobb angles between 50 and 88 degrees it is still satisfactory (14, 15, 16). In addition these researchers were also

2 able to demonstrate that rasterstereography can be used in patients with scoliosis after anterior and posterior correction and fusion (17, 18). Independent evaluation of the formetric system began after it was introduced into the European and US markets. Initial studies of reproducibility done on volunteer patients measured 30 consecutive times showed strong test- retest reproducibility, with a Chronbach s Alpha of for angular measurements of scoliosis (19). The standard deviation for scoliosis measurements was 3.4 degrees, which is similar to what would be encountered measuring Cobb Angles on radiographs. Sixty- six topographical scans were then compared to radiographs from the same patients, and the correlation between them was strong (r = 0.700) and statistically significant (p <.0001). A separate study of reproducibility used different examiners, and found that the intra- rater reliability was high (Chronbach s Alpha from to 0.992) as was the inter- rater reliability (Chronbach s Alpha 0.979) (20). The Body Mass Index (BMI) was also measured in these 51 volunteers, and correlated to the reliability of the measurements. No change in reliability was found with increasing BMI (21). A clinical study looking at the effect of BMI in female patients found that for BMI readings between 16 and 29, the formetric was able to produce reliable measurements. There was a correlation between reliability and BMI (r = 0.65) showing that it was easier to measure thinner patients, but even at the maximum BMI measured of 29, the spinal measurements had a standard deviation of only 4.6 degrees (22). Mangone et al. demostrated in 2013 that the rasterstereographic evaluation of vertebral rotation showed a good correlation with radiographically measured vertebral rotation, thereby confirming the possibility to use this method for deformity assessment in patients with idiopathic scoliosis. Surface topography also has many benefits in the long- term surveillance of spinal deformity. Because it exposes patients to no ionizing radiation, it can be used during every follow- up visit for the largest number of data points on the timeline. This will allow clinicians to pick up a change in deformity sooner. It also images the patient in their normal, habitual posture, avoiding some of the unnatural changes in posture induced by positioning the patient in front of the x- ray machine. One study followed 16 patients with AIS for a mean of 8 years (range 3-10) to compare their change in topography to their change in radiographic Cobb Angle (24), and found an excellent correlation between the two. The use of rasterstereography is however not limited to patients with scoliosis. Multiple studies have shown the versatility of this technique, since it can also be utilized e.g. to determine and treat pelvic obliquity, to evaluate for lumbar back pain and for changes of the spinal posture due to thoracic/lumbar spine fractures (25, 26,

3 27, 28, 29). Furthermore, clinical tests such as the forward bending test and the Matthiass posture test can be quantified with rasterstereography (30,31). The next phase of surface topography is to use it under dynamic conditions. The Formetric can measure patients at a rate of 60 frames per second, giving the clinician the opportunity to see the 3D shape of the spine change during the gait cycle. Initial studies of the reliability and validity of this new method by Betsch and colleagues indicate that it can produce accurate measurements over time during walking (32, 33). A number of similar studies are also underway. 1. Bunnel WP. An Objective Criterion for Scoliosis Screening. JBJS 1984 Dec: 66(9): Amendt LE, Ause- Ellias KL, Eybers JL, Wadsworth CT, Nielsen DH, Weinstein SL. Validity and reliability testing of the scoliometer. Physical Therapy 1990;70: Huang SC: Effectiveness of scoliometer in school screening for scoliosis. Taiwan I Hsueh Hui Tsa Chih 87: , 1988 J Formosan Med Assoc 1988; 87 : Turner- Smith AR, Harris JD, Houghton GR, Jefferson RJ. A method for analysis of back shape in scoliosis. J Biomech. 1988;21(6): Berryman F, Pynsent P, Fairbank J, Disney S. A new system for measuring three- dimensional back shape in scoliosis. Eur Spine J. 2008;17(5) Drerup B, Hierholzer E. Evaluation of frontal radiographs of scoliotic spines Part I. Measurement of position and orientation of vertebra and assessment of clinical shape parameters. J Biomech. 1992;25(11): Drerup B, Hierholzer E. Evaluation of frontal radiographs of scoliotic spines Part II. Relations between lateral deviation, lateral tilt and axial rotation of vertebrae. J Biomech. 1992;25(12): Drerup B, Hierholzer E. Assessment of scoliotic deformity from back shape asymmetry using an improved mathematical model. Clin Biomech (Bristol, Avon). 1996;11(7): Huysmans T, Haex B, Van Audekercke R, Vander Sloten J, Van der Perre G. Three- dimensional mathematical reconstruction of the spinal shape, based on active contours. J Biomech. 2004;37(11): Drerup B, Hierholzer E. Automatic localization of anatomical landmarks on the back surface and construction of a body- fixed coordinate system. J Biomech. 1987;20(10): Drerup B, Hierholzer E. Objective determination of anatomical landmarks on the body surface: measurement of the vertebra prominens from surface curvature. J Biomech. 1985;18(6): Drerup B, Hierholzer E. Movement of the human pelvis and displacement of related anatomical landmarks on the body surface. J Biomech. 1987;20(10):

4 13. Knott P, Mardjetko S, Thompson S. A Comparison of Automatic vs. Manual Detection of Anatomic Landmarks During Surface Topography Evaluation Using the Formetric 4D System. Scoliosis 2012; 7(Suppl 1): O Hackenberg L, Hierholzer E. 3- D back surface analysis of severe idiopathic scoliosis by rasterstereography: comparison of rasterstereographic and digitized radiometric data. Stud Health Technol Inform. 2002;88: Hierholzer E, Hackenberg L. Three- dimensional shape analysis of the scoliotic spine using MR tomography and rasterstereography. Stud Health Technol Inform. 2002;91: PubMed PMID: Schulte TL, Hierholzer E, Boerke A, Lerner T, Liljenqvist U, Bullmann V, Hackenberg L. Raster stereography versus radiography in the long- term follow- up of idiopathic scoliosis. J Spinal Disord Tech Feb;21(1): Hackenberg L, Hierholzer E, Pötzl W, Götze C, Liljenqvist U. Rasterstereographic back shape analysis in idiopathic scoliosis after posterior correction and fusion. Clin Biomech (Bristol, Avon) Dec;18(10): Hackenberg L, Hierholzer E, Pötzl W, Götze C, Liljenqvist U. Rasterstereographic back shape analysis in idiopathic scoliosis after anterior correction and fusion. Clin Biomech (Bristol, Avon) Jan;18(1): Frerich J, Hertzler K, Knott P, Mardjetko S. Comparison of Radiographic and Surface Topography Measurements in Adolescents with Idiopathic Scoliosis. Open Orthop J. 2012;6: Schülein S, Mendoza S, Malzkorn R, Harms J, Skwara A. Rasterstereographic evaluation of interobserver and intraobserver reliability in postsurgical adolescent idiopathic scoliosis patients. J Spinal Disord Tech Jun;26(4):E Mohokum M, Mendoza S, Udo W, Sitter H, Paletta JR, Skwara A. Reproducibility of rasterstereography for kyphotic and lordotic angles, trunk length, and trunk inclination: a reliability study. Spine(Phila Pa 1976) 2010;35(14): Knott P, Mardjetko S, Tager D, Hund R, Thompson S. The Influence of Body Mass Index (BMI) on the Reproducibility of Surface Topography Measurements. Scoliosis 2012; 7(Suppl 1):O Mangone M, Raimondi P, Paoloni M, Pellanera S, Di Michele A, Di Renzo S, Vanadia M, Dimaggio M, Murgia M, Santilli V. Vertebral rotation in adolescent idiopathic scoliosis calculated by radiograph and back surface analysis- based methods: correlation between the Raimondi method and rasterstereography. Eur Spine J Feb;22(2): Schulte TL, Hierholzer E, Boerke A, Lerner T, Liljengvist U, Bullmann V, Hackenberg L. Raster stereography versus radiography in the long- term follow- up of idiopathic scoliosis. J Spinal Disord Tech. 2008;21(1): Betsch M, Rapp W, Przibylla A, Jungbluth P, Hakimi M, Schneppendahl J, Thelen S, Wild M. Determination of the amount of leg length inequality that alters spinal posture in healthy subjects using rasterstereography. Eur Spine J Jun;22(6):

5 26. Betsch M, Schneppendahl J, Dor L, Jungbluth P, Grassmann JP, Windolf J, Thelen S, Hakimi M, Rapp W, Wild M. Influence of foot positions on the spine and pelvis. Arthritis Care Res (Hoboken) Dec;63(12): Betsch M, Wild M, Große B, Rapp W, Horstmann T. The effect of simulating leg length inequality on spinal posture and pelvic position: a dynamic rasterstereographic analysis. Eur Spine J Apr;21(4): Schroeder J, Schaar H, Mattes K. Spinal alignment in low back pain patients and age- related side effects: a multivariate cross- sectional analysis of video rasterstereography back shape reconstruction data. Eur Spine J Apr Krause M, Breer S, Mohrmann B, Vettorazzi E, Marshall RP, Amling M, Barvencik F. Influence of non- traumatic thoracic and lumbar vertebral fractures on sagittal spine alignment assessed by radiation- free spinometry. Osteoporos Int Jun;24(6): Betsch M, Wild M, Jungbluth P, Thelen S, Hakimi M, Windolf J, Horstmann T, Rapp W. The rasterstereographic- dynamic analysis of posture in adolescents using a modified Matthiass test. Eur Spine J Oct;19(10): Hackenberg L, Hierholzer E, Bullmann V, Liljenqvist U, Götze C. Rasterstereographic analysis of axial back surface rotation in standing versus forward bending posture in idiopathic scoliosis. Eur Spine J Jul;15(7): Betsch M, Wild M, Jungbluth P, Hakimi M, Windolf J, Haex B, Horstmann T, Rapp W. Reliability and validity of 4D rastersterography under dynamic conditions. Comput Biol Med. 2011;41(6) Betsch M, Wild M, Johnstone B, Jungbluth P, Hakimi M, Kühlmann B, Rapp W. Evaluation of a novel spine and surface topography system for dynamic spinal curvature analysis during gait. PLoS ONE. 2013;8(7)e Cite this article as: Knott P, Betsch M. (July, 2013) Evaluating Spinal Deformity Using Surface Topography. SSTSG Website, Spine and Surface Topography Study Group. Retrieved from literature.html.

Appraisal of the DIERS method for calculating postural measurements: an observational study

Degenhardt et al. Scoliosis and Spinal Disorders (2017) 12:28 DOI 10.1186/s13013-017-0134-y RESEARCH Open Access Appraisal of the DIERS method for calculating postural measurements: an observational study