Forced Lordosis on the Thoracolumbar Junction Can Correct Coronal Plane Deformity in Adolescents With Double Major Curve Pattern Idiopathic Scoliosis

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1 Forced Lordosis on the Thoracolumbar Junction Can Correct Coronal Plane Deformity in Adolescents With Double Major Curve Pattern Idiopathic Scoliosis Piet J. M. van Loon, MD,* Bob A. G. Kühbauch, MD,* and Frederik B. Thunnissen, MD, PhD SPINE Volume 33, Number 7, pp , Lippincott Williams & Wilkins Study Design. A prospective radiographic study was conducted. Objective. To support our hypothesis that correction of the scoliosis may benefit from a lordotic fulcrum force in the sagittal plane on the thoracolumbar spine. Summary of Background Data. Adolescent idiopathic scoliosis is an important spinal deformity. Correction can be achieved with limited options by current bracing techniques. Lateral bending radiographs are used to assess flexibility and predict treatment outcome. The corrective potential of a lordotic fulcrum force in the sagittal plane has not been addressed. Methods. Anterioposterior spine radiographs of patients with a double major curve pattern scoliosis were obtained in 2 groups of patients. In group A radiographs in 3 positions: standing, and supine with and without fulcrum (n 12), and group B radiographs in 2 positions (n 28): standing, and supine with lordotic fulcrum. Cobb angles were determined and evaluated statistically. The sagittal contour of the thoracolumbar junction in standing position was measured. Results. In group A with the patients lying supine a correction of the Cobb angle was obtained at the thoracic level of 15.4% and the lumbar level of 27.5% (P 0.001). Adding in supine position a lordotic fulcrum on the thoracolumbar junction resulted in a coupled further correction at the thoracic level of 15.7% and lumbar 18.1% (P 0.001). Comparing in group A the thoracic and lumbar curvatures in standing position with that on a lordotic fulcrum in supine position revealed a total reduction of 31% and 45.6%, respectively. For the independent group B this reduction in 1 step is 38% and 44.4%, respectively. Conclusion. Scoliotic deformities are significantly reduced in supine position by a lordotic fulcrum force on the thoracolumbar junction. These findings may have consequences on bracing techniques. Key words: adolescent idiopathic scoliosis, thoracolumbar junction, lordotic fulcrum, thoracolumbar kyphosis, etiology. Spine 2008;33: Adolescent idiopathic scoliosis is described as a 3-dimensional deformity of the spine with multifactorial and in essence unknown etiology. Frequently the deformity From the *Department of Orthopaedics, Rijnstate Hospital, Arnhem, The Netherlands; and Department of Pathology, VUMC, Amsterdam, The Netherlands. Acknowledgment date: January 9, First revision date: May 25, Second revision date: May 24, Third revision date: July 29, Fourth revision date: October 9, The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence and reprint requests to P.J.M. van Loon, MD, Department of Orthopaedics, Rijnstate Hospital, PO Box 9555, 6800 TA Arnhem, The Netherlands; pvanloon@wxs.nl consists of a double major curve with a thoracic (primary) and a lumbar (secondary) curve in the coronal plane. Together with a rotational component and decreased thoracic kyphosis in the sagittal plane, while the lumbar spine flattens the lordotic curve, the deformity settles truly in 3 planes. Scoliotic deformities are described in the coronal plane by calculating the radiographic Cobb-angle of each curve. 1 These measurements on standing full-spine anteroposterior radiographs are used as the golden standard to assess a scoliosis 2 and are currently standard in communication about these deformities. To assess the flexibility of a scoliotic curve and to predict the correctability, various radiographic methods have been described. 3 These methods of assessments include the lateral bending radiographs, traction radiographs, 4 push-prone radiographs, and the fulcrum-lateralbending radiographs. 4 9 All these different approaches have in common that they address a scoliosis as a deformity mainly in the coronal plane and the main correctional forces to treat this deformity should then also be applied in the same coronal plane. Various studies, however, indicate that none of these radiographs have been able to reliably predict the eventual correctability of the deformity. 1 4,7 9 Careful radiographic follow-up of possible curve progression is a mainstay of the treatment of scoliosis. Prolonged bracing therapy is frequently applied and for progressive curves corrective surgery is advocated. 10,11 Both in the bracing therapy and the multilevel spinal fusion correction of the deformity in the coronal and transversal planes have a more clear goal than correction in the sagittal plane. The aim of treatment is to obtain at the radiograph in the coronal plane a spinal column as straight as possible and minimal or no rotation. The effect on rotation is usually examined clinically. Remarkably the ideal sagittal curve at the different areas of the spine in scoliosis is not clearly defined in orthopedic textbooks. In case of bracing therapy distraction (as in the Milwaukee brace) or flexion (as in most braces based on 3-point correction) is applied in the sagittal plane on the thoracic spinal column in combination with the application of a lateral counter force (i.e., in the coronal plane) on the apex of the curve. Surgical techniques, such as the earlier Harrington instrumentation, also tend to straighten the scoliotic deformity in the coronal plane by distraction of the curve 12 often leaving the spine with a flattened contour in the sagittal plane. From our own clinical observations we noticed that an idiopathic scoliosis has a very slight kyphotic thoracolumbar junction, which is more prominent in sitting. In addition, active extension of the whole spine leads to a 797

2 798 Spine Volume 33 Number reduction of the kyphosis at the thoracolumbar junction. After empirical clinical testing we had the following hypothesis: a lordotic fulcrum force at the thoracolumbar spine may correct scoliosis from the sagittal plane According to this hypothesis forces in a pure perpendicular plane should alter coronal curves in scoliosis. This is in contrast to the currently applied counter forces in the coronal plane to correct a scoliotic deformity. The aim of our study was to examine radiographically that forced lordosis on the thoracolumbar junction can correct a double major pattern idiopathic scoliosis in adolescents. For this purpose, radiographs were made in a standing position and supine position, with and without a lordotic fulcrum at the thoracolumbar junction in the sagittal plane. Methods Forty patients with an adolescent idiopathic scoliosis with double (major) curves that were seen at our hospital between February 2003 and September 2006 were asked to participate with this study. Only patients with at least 1 curve of more than 25 Cobb angle were included. The study consisted of 35 female and 5 male patients with a double curve idiopathic scoliosis. The mean age was 14.2 years (range, 9 19 years). Risser sign varied from 0 to IV. The patients were divided into 2 groups: (A) with radiographs in 3 positions: standing, and supine with and without lordotic fulcrum (n 12), and (B) patients with radiographs in 2 positions (n 28): standing, and supine with lordotic fulcrum. Full-spine standing radiographs in 2 directions were obtained on long cassettes by certified radiology technicians in a standardized manner. Of all subjects an anteroposterior radiograph lying supine with the thoracolumbar junction over a radiolucent lordotic fulcrum was made (Figure 1). This fulcrumlordosis radiograph was obtained with the patient in a supine position with the thoracolumbar junction over a large, radiolucent plastic triangle that was padded for comfort. The fulcrum has a pyramid height of 10 centimeters. The fulcrum was placed directly under the thoracolumbar junction at the level T12 L1 (Figure 1). In both groups, a standing lateral radiograph was taken to measure the sagittal curve of the thoracolumbar spine. The Group A patients were kept to a minimum to avoid unnecessary radiographic exposure. The Cobb method was used to measure the upper (thoracic) and lower (lumbar) curve for each patient. Calculation of the Cobb angle was done independently by 2 observers (P.V.L. and B.K.). The average of 2 values was calculated when a difference was encountered. For all patients, a standing full-spine lateral radiograph was also available. Apart from the scoliotic Cobb angles in the coronal plane, the angle of the thoracolumbar junction was also measured in the sagittal plane. The sagittal thoracolumbar angle was defined as the angle between the proximal endplate of vertebra T10 and the distal endplate of vertebra L2. A straight thoracolumbar junction was defined as zero degrees, a lordotic thoracolumbar junction was defined when the junction had a negative angle, and a kyphotic thoracolumbar junction was defined when the junction had a positive angle (Figure 2). Statistical Analyses In Group A, the scoliotic Cobb angles on anteroposterior, fullspine radiographs were compared with the Cobb angles in the supine position with and without the application of a lordotic fulcrum and in Group B with supine over a fulcrum only. The reduction of the Cobb angle obtained in supine position (group A) was also expressed in percentages of the Cobb angle in standing position ( 100%). The differences between the means were analyzed by the paired t test. P-values 0.05 were considered to be significant. Results The clinical data of the patients and their sagittal Cobb angle of the thoracolumbar spine are shown in Table 1. For groups A and B, the scoliotic Cobb angles in standing and supine position, with and without lordotic fulcrum are shown in Table 2. In Table 3, the pair wise comparison for differences in Cobb angle and P-values are presented. In group A, with the patients lying supine, a significant correction of the Cobb angle was obtained at the thoracic level of 15.4% and the lumbar level of 27.5%. Adding a lordotic fulcrum in supine position on the thoracolumbar junction resulted in a further significant correction at the thoracic level of 15.7% and the lumbar level of 18.1%. Comparing in group A the thoracic and lumbar curvatures in standing position with that on a lordotic fulcrum in supine position revealed a total reduction of Figure 1. Photograph of patient in supine position in which an anteroposterior whole spine radiograph is taken with a lordotic fulcrum underneath. The top of the wedge-shaped fulcrum is placed centrally under the thoracolumbar spine.

3 Forced Lordosis and Coronal Plane Deformity van Loon et al 799 Figure 2. Full-spine anteroposterior radiographs while patient standing (A), lying supine (B), and (C) lying supine with the thoracolumbar junction over a radiolucant lordotic fulcrum. The standing radiograph demonstrated a 32 right thoracic curve Th5 Th12, with a subsequent correction to 26 while lying supine and 13 with a lordotic fulcrum. For the lumbar curve (Th12 L5), these Cobb angles were 33, 20, and 9, respectively. Note the correction of the rib-spine angle. 31% and 45.6%, respectively. For the independent group B this reduction is 38% and 44.4%, respectively. Full-spine standing lateral radiographs were used to calculate the sagittal angle of the thoracolumbar junction from Th10 to L2. A mean angle of 8 (range, 0 18, standard deviation, 5,4) was measured, indicating that in all patients a slight kyphotic or at least a neutral junction was present. In order to examine a possible relationship between the magnitudes of the scoliotic and kyphotic curves regression analysis was performed. No correlation was found between values of sagittal thoracolum- Table 1. Clinical Characteristics Are Shown for Groups A and B Group A (n 12) Group B (n 28) Age (yr)* Gender Male 1 4 Female Sagittal Cobb angle* The Sagittal Cobb angle is used as a measure for the thoracolumbar curve. *Mean standard deviation.

4 800 Spine Volume 33 Number Table 2. Scoliotic Cobb Angles (Mean Standard Deviation) in Patients With Standing Position (AP), Supine Position, and Supine With Fulcrum Is Shown for Thoracic and Lumbar Curves Radiograph Curve Localization Group A (n 12) Group B (n 28) AP Thoracic AP Lumbar Supine* Thoracic NA Supine* Lumbar NA Supine with fulcrum Thoracic Supine with fulcrum Lumbar *Without fulcrum, stretched legs. NA indicates not applicable. bar-curves and concomitant double curves in the coronal plane (P 0.2). Discussion This study demonstrates in 2 independent groups that application of a lordotic fulcrum on the thoracolumbar junction in the sagittal plane results in immediate correction of both curves in the coronal plane of double curve pattern idiopathic scoliosis. The relation between kyphotic and scoliotic spinal deformities are apparently a combined effect and by others already called coupled mechanism between curves in different planes. 16,17 Moreover, this effect on both curves is obtained by a 1 directional force in the perpendicular sagittal plane. To our knowledge this is the first study where correction of a concomitant kyphosis at the thoracolumbar junction is used in applying forces in a pure sagittal plane to demonstrate further correction from an only supine position of a scoliotic deformity in the coronal plane of 15% at thoracic level and 18% at lumbar level. Our study not only advocates a new type of correction film, but also shows that the potential effect of sagittal plane correction at the thoracolumbar junction may play a role in conservative treatment of the thoracic and lumbar curves. The Risser signs varied from O to IV. Since in all cases the correction was obtained, we assumed that maturity was not a factor of importance in the presented method of curve reduction in scoliosis, while applying forced lordosis. Incorporated in a brace treatment a more immature spine could theoretically benefit more of this technique. A sagittal kyphotic angle at Th10 12 in the standing radiograph is present in most patients. This kyphosis between the double scoliotic curves has not been mentioned before. However, this is in agreement with the hypothesis of Dickson, stating that lordosis or hypokyphosis in the sagittal plane is part of a 3-dimensional scoliotic configuration. 19 In between 2 scoliotic curves a kyphotic component has to be present, else it would be 1 scoliotic C-curve with long lordosis. Current bracing therapy of scoliosis has its focus mainly on straightening the spinal column together with application of a lateral counter force in the coronal plane. However, it is very well recognized that there are limitations to this technique. 10,20 Only limited correction of the preexistent deformity can be achieved and compliance of wearing these braces is problematic due to discomfort. Importantly, our data suggest that sagittal plane correction towards a lordotic, thus extended configuration of the thoracolumbar spine with increased space for the anterior parts of the vertebral bodies may be an interesting focus for future studies in the conservative treatment of idiopathic scoliosis. The traditionally made correction films for the evaluation of a scoliosis, such as the lateral (fulcrum) bending radiograph and the traction radiograph are used to assess the flexibility of the curves and to predict the surgical outcome. None of these techniques address the sagittal contour of the deformity. The fulcrum lordosis radiograph reflects a more natural posture and the act of correction more physiologic than with the traditional correction radiographs. The King classification system of scoliosis is based on standing radiographs in the coronal plane alone. Lenke classification connect findings in 2 perpendicular planes: coronal and sagittal plane. 2 Both classifications describe static conditions, while this study supports a coupled mechanism between curves in at least 2 perpendicular planes. The traditional radiographic correction efforts are performed in less natural positions than by our simple lordotic force. Application of a lordotic fulcrum force on the thoracolumbar junction may then be seen as a cantilever maneuver on the crossroads of curves at the center of the spine. In the liter- Table 3. Mean Standard Deviation of Scoliotic Cobb Angle Is Shown for Both Groups of Patients (A and B) in Standing (antero-posterior; AP) and Supine Position (Sup) With or Without Lordotic Fulcrum (F) Pairwise Comparison Curve Localization Difference in Cobb Angle Group A P Group B P AP sup with F Thoracic AP sup with F Lumbar Sup sup with F Thoracic NA Sup sup with F Lumbar NA AP sup without F Thoracic NA AP sup without F Lumbar NA NA indicates not applicable.

5 Forced Lordosis and Coronal Plane Deformity van Loon et al 801 ature it is stated that the sagittal contour of the thoracolumbar junction should ideally be slightly lordotic or at least be straight. 21,22 Actually little is written about the functional characteristics of this part of the spine. It is not excluded that our data fit in the hypothesis of Roth. His experimental studies give support to the mechanism of correction with the concept of disproportional osteo-neural growth giving alterations in the tension driven cooperation between the nervous system and the bony and discoligamentary spine. This is presented as a causative factor for the development and progression of kyphotic deformities and scoliosis ,18,23,24 A discussion in The European Spine Journal based on 2 of the later articles of Roth 13,15 between Porter, Burwell, and Dubousset ended in an atmosphere in which the uncoupled growth between osseous and neuromuscular structures could not be denied We feel that rapid progression of scoliosis and kyphosis, as is frequently seen during the growth-spurt in adolescents, may also be explained by this concept. In conclusion, adolescent scoliotic deformities with a double major curve pattern are immediately reduced by a lordotic fulcrum on the thoracolumbar junction. These results may have profound consequences on bracing therapy and strategies for surgical correction of scoliosis. Key Points Significant coupled correction of both curves in a double curved scoliotic deformity is achieved by a forced bending on a lordotic fulcrum of the thoracolumbar junction in the sagittal plane. This innovative approach may be applied to bracing therapy and in surgical correction. Evidence is shown for a relationship between a distinct thoracolumbar kyphotic deformity and an idiopathic double major curve scoliosis. The shown correction of double curved scoliosis by supposed restoration of the lordotic sagittal contour of early childhood points to a possible key role of the thoracolumbar junction in the dynamic mechanisms in adolescent spinal deformities. The revealed correction power of lordotic forces at the crossroad of curves in all planes at the thoracolumbar junction leads to similar known mechanisms related to redirection of tensile forces in mechanical spring-like structures. The supposed redirection of tensile forces in the spinal system shown by these results can be declared by Roth s hypothesis of tension-related discongruency of growth between the central neural system and the osseous and discoligamentary spine with deformities as scoliosis as shortening strategy. Acknowledgment This manuscript is dedicated to Jan Munneke, orthopaedic orthotist. He passed away suddenly August 7, 2007 during the last revision of this manuscript, for which he gave technical assistance in the correct way of getting results. As a keen technician he witnessed the moment of serendipity in revealing the first correction by lordotic forces of spinal deformity in children, away from the apexes. With all his skills and enthusiasm he developed a brace on the found principles of combined static and dynamic correction forces in kyphotic and scoliotic deformities. References 1. Cobb JR. Outline for studies of scoliosis. Am Acad Orthop Surg 1948; Lenke LG. Lenke classification system of adolescent idiopathic scoliosis. Instr Course Lect 2005;54: Hamzaoglu A,Talu U, Mirzanli C, et al. Assessment of curve flexibility in adolescent idiopathic scoliosis. Spine 2005;30: Kleinman RG, Csongradi JJ, Rinsky LA, et al. The radiographic assessment of spinal flexibility in scoliosis: a study of the efficacy of the push prone film. Clin Orthop Relat Res 1982;162: Vaughan JJ, Winter RB, Lonstein JE. Comparison of the use of supine bending and traction radiographs in the selection of the fusion area in adolescent idiopathic scoliosis. Spine 1996;21: Polly DW Jr, Sturm PF. Traction versus supine bending. Which technique best determines curve flexibility? Spine 1998;23: Cheung KM, Luk KD. Prediction of correction of scoliosis with use of the fulcrum bending radiograph. J Bone Joint Surg Am 1997;79: Luk KD, Cheung KM, Lu DS, et al. Assessment of scoliosis correction in relation to flexibility using the fulcrum bending correction index. Spine 1998; 23: Aronsson DD, Stokes IA, Ronchetti PJ, et al. Surgical correction of vertebral axial rotation in adolescent idiopathic scoliosis: prediction by lateral bending films. J Spinal Disord 1996;9: Karol LA. Effectiveness of bracing in male patients with idiopathic scoliosis. Spine 2001;15: Bridwell KH. Surgical treatment of idiopathic adolescent scoliosis. Spine 1999;24: Luk KD, Lu DS, Cheung KM, et al. A prospective comparison of the coronal deformity correction in thoracic scoliosis using four different instrumentations and the fulcrum-bending radiograph. Spine 2004;29: Roth M. Idiopathic scoliosis caused by a short spinal cord. Acta Radiol Diagn(Stockh) 1968;30: Roth M. Spinal cord and scoliosis. The cause and the effect (author s transl). Acta Chir Orthop Traumatol Cech 1975;42: Roth M. Idiopathic scoliosis from the point of view of the neuroradiologist. Neuroradiology 1981;21: Xiong B, Sevastik J, Hedlund R, et al. Sagittal configuration of the spine and growth of the posterior elements in early scoliosis. J Orthop Res 1994;12: van Rhijn LW, Plasmans CM, Veraart BE. Changes in curve pattern after brace treatment for idiopathic scoliosis. Acta Orthop Scand 2002;73: Nicolodani C. Anatomie und Mechanismus der Skoliose. Stuttgart: Erwin Naegele; Dickson RA. The aetiology of spinal deformities. Lancet 1988;1: Katz DE, Durrani AA. Factors that influence outcome in bracing large curves in patients with adolescent idiopathic scoliosis. Spine 2001;26: Bridwell KH, Betz R, Capelli AM, et al. Sagittal plane analysis in idiopathic scoliosis patients treated with Cotrel-Dubousset instrumentation. Spine 1990;15970: van Loon PJ, van Stralen G, van Loon CJ, et al. A pedicle subtraction osteotomy as an adjunctive tool in the surgical treatment of a rigid thoracolumbar hyperkyphosis; a preliminary report. Spine J 2006;6: Roth M. Idiopathic scoliosis and Scheuermann s disease: essentially identical manifestations of neuro-vertebral growth disproportion. Radiol Diagn (Berl) 1981;22: Roth M. Models of vertebroneural relations. Cesk Radiol 1970;24: Porter RW. The pathogenesis of idiopathic scoliosis: uncoupled neuroosseous growth? Eur Spine J 2001;10: Burwell RG. Comment to The pathogenesis of idiopathic scoliosis: uncoupled neuro-osseous growth? by Porter RW. Eur Spine J 2001;10: Dubousset J. Comment to The pathogenesis of idiopathic scoliosis: uncoupled neuro-osseous growth? by Porter RW. Eur Spine J 2001;10:488 9.