Idiopathic scoliosis in children: a pragmatic approach for radiologists

Transcription

1 Idiopathic scoliosis in children: a pragmatic approach for radiologists Poster No.: C-2107 Congress: ECR 2012 Type: Educational Exhibit Authors: F. Uyttenhove, E. Nectoux, A. Moraux, J. Bigot, B. Herbaux, N. Boutry; Lille/FR Keywords: Musculoskeletal spine, Pediatric, Conventional radiography, CT, MR, elearning, Education, Pathology DOI: /ecr2012/C-2107 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 53

2 Learning objectives - To define key points that radiologists should report in evaluation of children with idiopathic scoliosis (IS). - To review current indications of conventional radiography (CR), computed tomography (CT) and magnetic resonance imaging (MRI) in children with IS. - To familiarize radiologists with the EOS system which allows both 2D imaging with a lower dose of radiation than CR and 3D surface reconstructions. - To expose the basic knowledge in IS management. Background IS is one of the most common conditions encountered in paediatric practice. It is defined as a three-dimensional (3D) structural deformity of the spine that may occur in the first 3 years of life (infantile IS, male preponderance, thoracic levoscoliosis more frequent); at age 4-10 years (juvenile IS, female predominance, thoracic dextroscoliosis more frequent) or at age years (adolescent IS, female predominance, dextroscoliosis more frequent). The aetiopathogenesis of IS remains unclear. IS is characterized by one or several lateral spinal curvatures in the coronal plane: - The major curve, ( Fig. 1 on page 3 ) also called primary curve or structural curve, is the first to develop. It may be single or multiple. It is characterized by vertebral morphologic changes (i.e. wedging, axial rotation). The structural curve is fixed, inflexible, and is included in operative fusion if surgery is necessary. - The minor curve, ( Fig. 2 on page 5 ; Fig. 3 on page 7 ) also called secondary curve or non-structural curve, is considered to develop secondarily, to compensate for the progression of the major curve and maintain a global spino-pelvic balance. It may be single or multiple. It is the smallest curve and the one that exhibits less vertebral rotation. There are no vertebral morphologic changes. The non-structural curve is nonfixed, flexible, and should not be included in operative fusion if surgery is necessary. However, over time, a non-structural curve may become structural. Page 2 of 53

3 Images for this section: Page 3 of 53

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5 Fig. 1: Major left thoraco-lumbar scoliosis Page 5 of 53

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7 Fig. 2: Major dextrothoracic scoliosis with left lumbar minor curve. Page 7 of 53

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9 Fig. 3: Levolumbar scoliosis with a discreet minor dextro thoracic curve Page 9 of 53

10 Imaging findings OR Procedure details Imaging is essential in making the diagnosis, determining the severity of initial curvature and its probability of progression, and therefore, helping establish proper treatment. I. Diagnosis of IS A. Conventional radiography Conventional radiography (CR) is still the modality of choice in IS, regarding both initial diagnosis and assessment. CR also serves well to rule out other types of scoliosis. Further on, CR allows proper follow-up and dynamic assessment of the curves. According to these X-rays, the most appropriate treatment will be chosen out of routine observation, orthopedic bracing or surgical treatment. Post-treatment follow-up is most often performed using CR. Moreover, CR is used to assess bone age of the patient using in our experience the iliac crest Risser index, but also both the Greulich-Pyle and the Nahum-Sauvegrain methods. It requires a good technique: patient in supine position, bare foot. Arms are over the head. Frontal radiograph is performed in PA incidence for female patients to lessen the radiation to the breasts and gonads. For male patients, gonad shielding can also be used. On lateral radiograph, major curve's convexity must be closed to the CR plate. Arms are over the head or at best horizontal maintained by a support (intravenous solution stand for example) in order to clear the spine without any anterior unbalance or curve modification. B. EOS This technology is based on adaptation of G. Charpak's works (92' Nobel Prize in Physics) in clinical X-ray detector. This new slot-scanning radiograph imager allows the simultaneous acquisition of radiograph images of two orthogonal planar images in a vertical, weight-bearing standing or sitting position. The gantry is composed of two sets of detectors and moves vertically ( Fig. 4 on page 19 ). The patient is positioned at the intersection of the two X-ray fan-beams which scan the patient vertically. A single scan will simultaneously produce both PA and lateral images of the patient at scale 1:1 ( Fig. 5 on page 20 ) Page 10 of 53

11 Scanning is not limited vertically, unlike CR; in this regard, lower limb length discrepancy can also be explored in the same time with minimal irradiation. C. What radiologists should describe, measure and assess on radiographs 1) In the coronal plane In the coronal plane, key points to assess on standing views are the coronal spino-pelvic balance, the degree of vertebral angulation, the spinal curve type, and the severity of vertebral rotation. The skeletal maturity (cf. infra) has also to be assessed. Coronal spino-pelvic balance - The coronal spinal balance is appreciated by dropping a plumb line vertically from the center of the C7 vertebral body. This usually intersects with the central sacral vertical line = CSVL (coronal balance). Balance is considered abnormal (coronal imbalance) when the distance between this plumb line and the sacral landmark is greater than 2 cm to the right (positive coronal imbalance) or to the left (negative coronal imbalance) ( Fig. 6 on page 21 ). - The pelvic balance is evaluated by drawing a tangential line across the top of the iliac crests. Normal pelvic balance corresponds to an horizontal line. If the line is oblique to the right or the left, the obliquity must be quantified in centimeters (or degrees) to the horizontal ( Fig. 7 on page 23 ). If there is a pelvic obliquity, the equality or inequality of femoral head height must be checked. Overall, lower limb length discrepancy is regarded significant when over 1 centimeter. Pelvic obliquity in a standing patient is more often in relation with leg length discrepancy rather than with IS. Thoraco-lumbar X-rays should be performed provided pelvic obliquity is corrected using compensation soles. Degree of angulation A spinal curve is characterized by one apex vertebrae (AV) and two end superior and inferior vertebrae (EV). Identification of these vertebrae is essential to assess the degree of angulation. AV is the vertebra which is located at the top of the curve. It is defined as the greatest rotated or farthest laterally deviated vertebra from the center of the spine (CSVL in routine) ( Fig. 8 on page 25 ). AV is also the most horizontally oriented vertebra within the curve. Superior and inferior EV, also called terminal vertebrae, are the vertebrae which are located at both extremities of the curve. They are defined as the most tilted vertebrae toward the apex of the curve. The degree of vertebral angulation is measured by the Cobb angle which is the angle Page 11 of 53

12 formed by the intersection of two lines, one parallel to the superior endplate of the superior end vertebra and the other parallel to the inferior endplate of the inferior end vertebra. When endplates are difficult to visualize, the superior and inferior borders of the pedicles of the superior end vertebra and inferior end vertebra respectively may be used, though unilateral pedicular dystrophy might lead to overevaluation of the Cobb angle in such cases. Scoliosis is defined by a lateral spinal curve with a Cobb angle of 10 or more and is at risk of progression. Lateral spinal curves smaller than 10 are within a normal range of variation and are less likely to progress. IS over 10 are at higher risk of progression when dealing with prepubertal children. It is less likely for a curve to progress when the Risser index is over II. A 20 curve in a Risser III adolescent has an approximate 5% risk of progression and a 70% risk of progression in a Risser 0 child. Regardless of maturation, all scoliosis over 30 are highly likely to progress. Spinal curve type and side Spinal curve type - The structural curve is the largest curve and the one that exhibits more vertebral rotation whereas the non-structural curve is the smallest curve and the one that exhibits less vertebral rotation. For each curve (structural or not), there are one apex vertebra (AV) and two end superior and inferior vertebrae (EV). The structural curve is non- or partially correctable on ipsilateral sideward-bending views with a Cobb angle ³ 25 whereas the non-structural curve is correctable on ipsilateral sideward-bending views with a Cobb angle < 25 ( Fig. 26 on page 47 ). Spinal curve side - The side is defined by the curve convexity. Severity of vertebral rotation It is maximal at the apex of the curve, and can be quantified on frontal radiographs by different methods (Cobb, Nash-Moe) but their accuracy is limited. - Cobb's method, the most known, uses the position of the spinous process as a reference landmark. If there is no vertebral rotation, the spinous process is seen in the midline of the vertebral body. As the degree of rotation increases (1, 2, 3 or 4 crosses), the spinous process migrates towards the curve concavity. At grade 0, spinous process is at the center of vertebral body ( Fig. 9 on page 25 ). - Nash-Moe's method uses the position of the pedicles as a a reference landmark. If there is no vertebral rotation, both pedicles are seen within the outer thirds of the two halves of the vertebra. As the degree of rotation increases (grades 1, 2, 3, or 4), the Page 12 of 53

13 convex-side pedicle migrates towards the curve concavity while the concave-side pedicle gradually disappears. At grade 0, vertebral pedicles are symmetric with spinous process in the middle ( Fig. 10 on page 26 ). Skeletal maturity Along with curve magnitude and pubertal status (Tanner stages) skeletal maturity at IS onset is a major parameter affecting IS progression. Skeletal maturity can be assessed by looking at the left hand and wrist (Greulich & Pyle method) and/or the left elbow during puberty (Nahum & Sauvegrain method) or most commonly, at the presence and degree of ossification of the iliac crest apophysis (Risser index). Normally, ossification progresses from lateral to medial. In Risser grade 0, the apophysis is not present. In Risser grades, 1,2,3 and 4 the apophysis covers 25%,50%,75% and 100% respectively. Grade 5 corresponds to a complete fusion of the apophysis ( Fig. 11 on page 27 ). Coronal spino-pelvic balance Degree of angulation Spinal curve type and side Severity of vertebral rotation Skeletal maturity Table n 1: Key points to assess on frontal radiographs 2) In the sagittal plane In the sagittal plane, key points to assess on standing views are the sagittal spino-pelvic balance, the spinal parameters, and the pelvic parameters that influence them. Sagittal spino-pelvic balance Sagittal spino-pelvic balance may be considered as an open linear chain composed of different anatomic segments, from the head to the pelvis, that are closely related to each other. This parameter is important to take into account when assessing IS because this balance helps to maintain a stable posture with a minimum of energy expenditure. It can be appreciated by dropping a plumb line vertically from the center of the C7 vertebral body. This usually intersects with the posterosuperior aspect of the S1 vertebral Page 13 of 53

14 body (sagittal balance). Balance is considered abnormal (sagittal imbalance) when the distance between this plumb line and the sacral landmark is greater than 2 cm anterior (positive sagittal imbalance) or posterior (negative sagittal imbalance) ( Fig. 12 on page 28 ). Global sagittal spino-pelvic balance can also be appreciated by dropping a plumb line vertically from the external acoustic meatus. This usually passes through the shoulders, hips and knees, to end slightly anterior to the ankles. Spinal parameters Thoracic kyphosis and lumbar lordosis are the two main spinal parameters to assess ( Fig. 13 on page 30 ). Thoracic kyphosis - It is the angle measured between the tangent lines to the superior endplate of T4 (or T1 when visible) and the inferior endplate of T12. Normal values are comprised between in children. Lumbar lordosis - It is defined as the angle measured between the tangent of the superior end plate of L1 and the tangent of the inferior end plate of L5. The normal values are comprised between However, values of thoracic kyphosis and lumbar lordosis must be interpreted according to the age of the child (there is an increase during childhood and adolescence) and the pelvic incidence (cf. infra) Pelvic parameters The sacral slope, the pelvic version (or tilt) and the pelvic incidence are the three main pelvic parameters to assess. Sacral slope - It is defined as the angle measured between the tangent line to the sacral plateau and the horizontal. Normal values are comprised between ( Fig. 14 on page 32 ). Pelvic version - It is defined as the angle measured between the vertical and the line connecting the center of the sacral plateau crossing the geometric center of femoral heads. Normal values are comprised between 0-15 ( Fig. 15 on page 32 ). Pelvic incidence - It is defined as the angle measured between a line perpendicular to the center of sacral endplate and a line connecting the center of sacral endplate to the center of femoral heads. This parameter is the sum of the sacral slope and the pelvic version. Normal values are comprised between ( Fig. 16 on page 33 ). All these spinal and pelvic parameters are positional, except pelvic incidence. This last parameter is an anatomic parameter, specific and constant for each individual. Page 14 of 53

15 Pelvic incidence refers to the pelvic shape. It tends to increase during childhood and adolescence until reaching its final and constant value in adulthood. Pelvic incidence determines pelvic orientation (i.e. sacral slope and pelvic version) as well as spinal curves, especially lumbar lordosis. A high incidence determines physiologically more important sagittal spinal curves. The greater the pelvic incidence, the greater the lumbar lordosis and thoracic cyphosis to maintain a stable posture. Sagittal spino-pelvic balance Thoracic kyphosis Lumbar lordosis Pelvic incidence Table n 2: Key points to assess on sagittal radiographs D. EOS versus CR Physical properties of slot-scanner suggest high quality images with less irradiation than standard imagers. Collimation of both the beams and detectors minimizes the scattered radiation, potentially enhancing effective detective quantum efficiency, and increasing the detected signal to noise ratio. The result is an optimized contrast difference for each exposure with more than levels of grey, leading to an excellent visualization of both hard and soft tissue in a single exposure ( Fig. 17 on page 34 ; Fig. 18 on page 35 ). Average skin dose is reduced from a factor of 5 to 9 with EOS system compared to CR for PA and lateral spine radiograph, which is very interesting in IS, requiring generally several follow up. The slot scanning technique eliminates vertical distortion and errors inherent in other systems that require digital stitching. Full spine images are easily created in about 5 seconds for a child. In addition to the 2D imaging advantages, the EOS system enables to obtain 3D weight bearing reconstructions, impossible thing to do with CT. Reconstruction of the 3D bone envelop of the spine is performed using EOS using low dose, orthogonal, biplane images and a priori statistical information about the 3D bones ( Fig. 19 on page 36 ). Reconstructions enable to schematize and visualize deformation at any angle, to measure spinal parameters and to quantify shifting and angulation of each vertebra in 3D ( Fig. 28 on page 48 ; Fig. 20 on page 38 ); in IS, axial vertebral rotation (especially Page 15 of 53

16 of apex vertebrae) can be measured and represented as vectors or diagrams ( Fig. 30 on page 51 ; Fig. 31 on page 51 ). Direct 3D visualization of spinal deformity, without and with bracing, before and after surgery, is also very useful and is now a validated method. E. Are CT and MR useful in IS? Further imaging is mainly indicated when an underlying cause is suspected (i.e. osseous or neuropathic.). However, computed tomography (CT) and magnetic resonance imaging (MRI) may be useful for assessing IS: - CT may be indicated in presence of a complex and severe IS on radiography, especially when surgery is planned, for better 2D (morphologic vertebral changes, width of pedicles) and/or 3D (importance of deformity) analysis. Like the EOS system, CT is a reliable method to measure vertebral rotation on axial images, but it is not performed in supine position and usually required a higher dose of radiation. Thus, CT spiral must be as short as possible, centered on IS. There is no need of contrast enhancement in IS and CTlow dose technique can be used. Moreover, EOS is not designed for malformative spinal reconstructions, and in the latter case, CT scan 3D reconstruction is mandatory. - MR may be indicated to evaluate patients with an anusual curve pattern or alarming clinical manifestations (Table n 3). It can depict several abnormalities such as ArnoldChiari malformation, tumor or syringomelia. In our insitution, basic MPR protocol is made up of sagittal T1 and T2-weigthed sequences of all spine, possibly completed by axial slices if necessary. In curve with great magnitude, the offset complicates the positioning of slices, with several segments and obliquity necessary for a complete study in 2D. Frontal images can often very useful in addition to the axial and the sagittal plane. 3D sequences with curvilign reformatted slices can also be useful for medullar and radicular assessment but generally require longer acquisition time. One must keep in mind that every painful scoliosis should be considered as a "symptom" scoliosis, thus leading to search an etiology (especially in the top and the concavity of the curve). Clinical features Radiographic features Age < 10 years (1 seule référence dans la Curve type commonly associated with literature) neuropathy (left thoracic, double thoracic, triple major, short segment, or long right thoracic curves ; severe curvature after skeletal maturity) Page 16 of 53

17 Neurologic signs Suspicion of intra canalar lesion (i.e. wide spinal canal, thin pedicle, wide neural foramina) Rapid progression of IS Foot deformity Pain (neckpain, backpain, headache) Table n 3: Main indications of MR imaging in presumed IS (from Kim, H., et al., Scoliosis imaging: what radiologists should know. Radiographics, (7): p ) Somes authors suggests that MR should be performed in age < 10 years old and systematically before every surgical treatment to exclude any underlying lesion that can be occulted by radiography (and ensure that it is an authentic IS). Identifying an underlying cause could therefore help alleviate progressive neurologic deterioration and lead to stabilize or improve scoliosis, and prevent new or additional neurologic deficits. 99 Tc- scintigraphy remains indicated in painful scoliosis (looking for infection, osteoid osteoma...) II. MONITORING of IS IS is a pathology developing through several years, requiring a serial observation and thus, repetition of CR. With the growing problem of radiation dose, EOS system appears as a very useful technique. In IS, progression is most likely during periods of rapid growth; Duval-Beaupère defined evolutivity laws in structural scoliosis. Scoliosis evolution occurs in three steps where the growth is linear (pre puberty, puberty and maturity). The aggravation of IS is rapid between the point "P" (beginning of puberty) and R (Risser sign i.e. grade I Risser) ( Fig. 21 on page 40 ). This moment precedes the menarche and coincides with the pubertal growth spurt. The optimal follow-up interval in skeletally immature patients may be as short as 4 months. After skeletal maturity is attained, only curves of more than 30 must be monitored for progression. An increase in the Cobb angle by 5 or more between consecutive radiographic examinations indicates progression of scoliosis. When incorporating measurement of the Page 17 of 53

18 Cobb angle into routine clinical assessments of curvature, especially in monitoring for progression, one should keep in mind the variability of Cobb angle: diurnal variation, prone position, CR technique and intra and inter-observer variability. Because measurement error is lower when end vertebrae are consistently defined, the same endpoints should be used at follow-up as at the initial curve assessment. The most commonly used and most accurate measurement of spinal curvature in monitoring is the Cobb angle. In curve of greater magnitude, simply measuring the Cobb angle may not show progression. However, assessing the degree of rotation of the AV, overall spine balance are all clinically significant suggestions of a progressive deformity. III. MANAGEMENT of IS IS, despite being idiopathic, could generate a functional (respiratory, neurologic, pain) or esthetic disorder. The treatment of IS depends from curve severity, IS localization and the likehood of curve progression. Different options are possible: observation, bracing or surgery. There is no international consensus for management and thus, the attitude might be "surgeon dependent". Attentive follow-up is proposed in adolescent IS with a Cobb angle less than 20 or when a skeletally mature patient has a curvature with a Cobb angle of less than 30 at presentation. Patients are followed up at 4 to 12 months intervals. Bracing aims to avoid surgery. Indications for bracing are represented by the following criteria: curve progression (>20 ) in skeletally immature patients (Risser <4), major sagittal imbalance as hypokyphosis and hypolordosis (which are major aggravating factors), lumbar scoliosis because they become painful at adult age. Bracing is a treatment of choice in adolescent IS with a Cobb angle of Results are considered satisfactory if the main curve is significantly reduced over 50% with the brace ( Fig. 22 on page 40 ; Fig. 23 on page 41 ; Fig. 24 on page 43 ; Fig. 25 on page 45 ). When surgery is required, its primary goal of surgery is to prevent curve progression by achieving bone fusion (arthrodesis) of involved vertebral segments. The secondary goals are curve correction, spino-pelvic balance restoration, while leaving as many mobile segments in lumbosacral spine as possible. In general, the surgeon attempts to minimize the number of fused motion segments; recognition of a non structural curve can allow a shorter fusion and maintain a maximal Page 18 of 53

19 range of motion. If the structural curve is straightened, the non structural curve will correct spontaneously. The structural or nonstructural nature of curves should be assessed on the basis of ipsilateral side-bending views, especially when surgery is planned. The radiographic definition of a structural curve is one with a Cobb angle of 25 or more on ipsilateral sidebending views ( Fig. 26 on page 47 ). Surgery is indicated in skeletally immature patients with Cobb angle superior to 45 at the thoracic level and superior to at the lumbar level at presentation, provided the triradiate cartilage is fused. Otherwise, there is a risk of crankshaft effect after surgery, i.e anterior growth of the spine with posterior fusion. Surgery is also a good option in IS progressing despite the use of brace or when the patient observanceof the brace is poor ( Fig. 27 on page 47 ; Fig. 28 on page 48 ; Fig. 29 on page 49 ; Fig. 30 on page 51 ; Fig. 31 on page 51 ). Images for this section: Page 19 of 53

20 Fig. 4: EOS 2D/3D system Page 20 of 53

21 Fig. 5: EOS Scanning technique. Vertical linear scanning allows the acquisition of long length images without being limited by the detector's vertical dimension. Page 21 of 53

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23 Fig. 6: Coronal vertebral alignment. Non significant coronal unbalance in right thoracolumbar scoliosis. The asterisk represents the center of C7 vertebral line. C7 plumb line from it (dotted line) doesn't cross the central sacral vertical line (CSVL) (in white) but the distance is not significant (< 2 cm). Page 23 of 53

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25 Fig. 7: Pelvic unbalance due to leg length discrepancy, inducing a scoliotic attitude, corrected by using compensation soles (not shown). Fig. 8: Measurement of a simple lateral curvature using Cobb method. T9 and L2 are defined as the end vertebras and T11 as the apex vertebra. The Cobb angle is defined either as the angle between the tangential lines (angle a) or the angle between two lines drawn perpendicular (solid lines) to the tangents (angle b). Page 25 of 53

26 Fig. 9: Measurement of vertebral rotation by Cobb method. Page 26 of 53

27 Fig. 10: Measurement of vertebral rotation by Nash & Moe method. Page 27 of 53

28 Fig. 11: Risser test. Difference between grades 0 and 5 may be done by checking the upper femoral physis (still open in grade 0; closed in grade 5). Page 28 of 53

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30 Fig. 12: Sagittal vertebral alignment. Significant negative sagittal imbalance. The asterisk represents C7 vertebral body ; the plumb line from the center of it is clearly posterior to the posterosuperior aspect of S1 and significant (> 2 cm) defining a sagittal imbalance. Page 30 of 53

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32 Fig. 13: Rachidian parameters measured on sagittal radiographs. The vertebral body landmarks should also be chosen according to the size of the curve (i.e. T1, T4, T12, L1 and L5. NB: T9 is considered as the gravity center of the spine but T9 sagittal offset is not routinely assessed in pediatric practice. Fig. 14: The sacral slope (SS) represents the angle between the sacral plate and the horizontal line. Page 32 of 53

33 Fig. 15: Pelvic version (PV) is measured from the angle between the vertical line and the line joining the middle of the upper sacral plate and the hip axis. Page 33 of 53

34 Fig. 16: Pelvic incidence (PI) is defined as the angle between the perpendicular of the upper sacral plate and the line joining the middle of the upper sacral plate and the hip axis. NB: PI represents the sum of sacral slope and pelvic version. Page 34 of 53

35 Fig. 17: Comparison between CR (right) and EOS system (left) on PA radiograph in the same patient followed-up for a scoliosis secondary to Scheuermann's disease. Page 35 of 53

36 Fig. 18: Comparison between CR (right) and EOS system (left) on lateral radiograph in a patient followed-up for a scoliosis secondary to a Scheuermann's disease (same patient as in Fig. 17). Page 36 of 53

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38 Fig. 19: Schematization of 3D reconstruction in EOS system. Page 38 of 53

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40 Fig. 20: Schematization of spine deformation with EOS reconstructions (same patient as in Fig. 8). Apex and end vertebras are defined semi automatically by the system but can be changed by the user. EOS enables to calculate shifting of each vertebra, thus generating Cobb angle. Fig. 21: Evolutivity laws of scoliotic curve according to Duval-Beaupère. Page 40 of 53

41 Fig. 22: AP standing radiograph without bracing shows a left lumbar scoliosis (Cobb angle = 23 ) with a minor right thoracic curve. With bracing, the major curve has nearly disappeared (Cobb angle = 5, reduction over 50% with the brace), corresponding to a good result. Page 41 of 53

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43 Fig. 23: CTM (Cheneau-Toulouse-Munster) corset, the most used in our institution (front view). Page 43 of 53

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45 Fig. 24: CTM (Cheneau-Toulouse-Munster) corset (back view). Page 45 of 53

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47 Fig. 25: Making of a CTM corset. Post manufactured alteration is made with CR, in order to localize areas requiring addition of material (to correct the curve) and other areas where the foam has to be removed (to permit a good expansion of soft tissues), while the spine is pushed in the good direction. Fig. 26: Neutral standing AP radiograph shows a major dextrothoracic scoliosis with minor left lumbar curve. Rightward-bending demonstrates a Cobb angle > 25 for the major curve (= structural) whereas leftward-bending shows a minime Cobb angle (< 25 ) for the lumbar curve (corresponding to a non-structural curve. Bending radiographs are systematic in preoperative assessment to minimize the number of fused motion segments. NB: The structural curve is non- or partially correctable on ipsilateral sidewardbending views with a Cobb angle > 25 whereas the non-structural curve is correctable on ipsilateral sideward-bending views with a Cobb angle < 25. Page 47 of 53

48 Fig. 27: Pre- (left) and post-operative (right) CR of a major right thoracic scoliosis (T6-T10-L1) with minor left lumbar curve (L1-L3-L4). In pre-operative CR, there was a nonsignificant coronal unbalance to the right, corrected after surgery (same patient as in Figs ). Page 48 of 53

49 Fig. 28: Pre- (left) and post-operative (right) CR of a major right thoracic scoliosis with EOS reconstruction. The Cobb angle of the major curve is significantly reduced after surgery. There is no significant modification of pelvic parameters. Notice that the sagittal balance is respected (same patient as in Figs ). Page 49 of 53

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51 Fig. 29: Pre- (up) and post-operative (down) 3D reconstructions. Left reconstructions correspond to frontal spine views ; right ones to top views. The 3D reconstructions are a priori reconstructions and so don't reflect the exact bony morphology (same patient as in Figs ). Fig. 30: Diagram showing the axial vertebral rotation (calculated in relation to the hips) before and after surgery. The diagram is extrapolated from 3D reconstructions and post processing. Note that the apex vertebra of the main curve (T10) is one of the most rotated vertebrae, unlike end vertebras (same patient as in Figs ). Fig. 31: Representation in top views of vertebral vectors before and after surgery. Each vertebra corresponds to a vector, characterized by a rotation (direction of the arrow) and distances from the geometric center of femoral heads in coronal (X axis) and sagittal (Y axis) planes. Notice the propensity of laterodeviation of the spine to the right in pre operative, already shown in CR. NB: The two green circles represent the femoral heads Page 51 of 53

52 Conclusion CR plays an important role in IS diagnosis and follow up but requires repeated examinations. In this regard, the EOS system is very useful, both for 2D and 3D assessment of the spinal deformity. Personal Information References 1. Boseker, E.H., et al., Determination of "normal" thoracic kyphosis: a roentgenographic study of 121 "normal" children. J Pediatr Orthop, (6): p Diard, F., et al., [Imaging of chilhood and adolescent scoliosis]. J Radiol, (9 Pt 2): p Duval-Beaupere, G., et al., [A unique theory on the course of scoliosis]. Presse Med, (25): p Hall, F.M., et al., Re: more about scoliosis imaging for radiologists. Radiographics, (4): p Kim, H., et al., Scoliosis imaging: what radiologists should know. Radiographics, (7): p Legaye, J., et al., Pelvic incidence: a fundamental pelvic parameter for threedimensional regulation of spinal sagittal curves. Eur Spine J, (2): p Lonner, B.S., et al., Variations in pelvic and other sagittal spinal parameters as a function of race in adolescent idiopathic scoliosis. Spine (Phila Pa 1976), (10): p. E Mac-Thiong, J.M., et al., Sagittal spinopelvic balance in normal children and adolescents. Eur Spine J, (2): p Nash, C.L., Jr. and J.H. Moe, A study of vertebral rotation. J Bone Joint Surg Am, (2): p Roussouly, P. and C. Nnadi, Sagittal plane deformity: an overview of interpretation and management. Eur Spine J, (11): p Page 52 of 53

53 11. Schmitz, A., et al., Visualisation of the brace effect on the spinal profile in idiopathic scoliosis. Eur Spine J, (2): p Page 53 of 53