Idiopathic scoliosis: the relation between the vertebral canal and the vertebral bodies

Relative anterior spinal overgrowth in mild and moderate adolescent idiopathic scoliosis: a retrospective study

To determine whether relative anterior spinal overgrowth (RASO) occurs regardless of scoliosis segments and severity, and to explore the pattern of vertebral body height changes in adolescent idiopathic scoliosis (AIS). A total of 125 AIS and 179 non-scoliotic adolescents were enrolled. The anterior vertebral body height (VBHa) and posterior vertebral body height (VBHp) were measured on lateral spine radiographs, and the VBHa/VBHp ratio was calculated. The ratios were compared between the two groups and across scoliosis segments in the AIS group. The correlation between scoliosis severity and vertebral ratios, as well as the relationship between the apex vertebra's ratio and Cobb angle, was analyzed. Results showed that the VBHa/VBHp ratios were higher in the AIS group than the control group from T6 to L5 (P < 0.001), with increasing ratios from T7 to T10 and L1 to L5. No significant differences were found across scoliosis segments. Pearson analysis showed positive correlations between scoliosis severity and ratios at T7, T8, and T11 (P < 0.05), and a negative correlation at L5 (P < 0.05). No correlation was found between the apex vertebra's ratio and the Cobb angle. In conclusion, RASO is common in mild to moderate AIS and may help maintain spinal function.

Genetics and pathogenesis of scoliosis

Background

Scoliosis is defined as a lateral spine curvature of at least 10° with vertebral rotation, as seen on a posterior-anterior radiograph, often accompanied by reduced thoracic kyphosis. Scoliosis affects all age groups: idiopathic scoliosis is the most common spinal disorder in children and adolescents, while adult degenerative scoliosis typically affects individuals over fifty. In the United States, approximately 3 million new cases of scoliosis are diagnosed annually, with a predicted increase in part due to global aging. Despite its prevalence, the etiopathogenesis of scoliosis remains unclear.

Methods

This comprehensive review analyzes the literature on the etiopathogenetic evidence for both idiopathic and adult degenerative scoliosis. PubMed and Google Scholar databases were searched for studies on the genetic factors and etiopathogenetic mechanisms of scoliosis development and progression, with the search limited to articles in English.

Results

For idiopathic scoliosis, genetic factors are categorized into three groups: genes associated with susceptibility, disease progression, and both. We identify gene groups related to different biological processes and explore multifaceted pathogenesis of idiopathic scoliosis, including evolutionary adaptations to bipedalism and developmental and homeostatic spinal aberrations. For adult degenerative scoliosis, we segregate genetic and pathogenic evidence into categories of angiogenesis and inflammation, extracellular matrix degradation, neural associations, and hormonal influences. Finally, we compare findings in idiopathic scoliosis and adult degenerative scoliosis, discuss current limitations in scoliosis research, propose a new model for scoliosis etiopathogenesis, and highlight promising areas for future studies.

Conclusions

Scoliosis is a complex, multifaceted disease with largely enigmatic origins and mechanisms of progression, keeping it under continuous scientific scrutiny.

Is sagittal spinopelvic alignment a cause of low back pain in pediatric spine pathologies? A review

Purpose

Altered spinopelvic morphology is observed in many spine pathologies occurring during growth. The aim of the study is to better understand the sagittal compensatory mechanisms and their possible influence on the occurrence of pain in selected pediatric spine pathologies.

Methods

A bibliographic search in the PubMed database included articles published between September 1965 and July 2023. The keywords contained in the search were "spondylolysis," "spondylolisthesis," "scoliosis," "kypho," "sagittal," "pediatric," "child," "adolescent," "grow," "development," and "pain."

Results

The largest diversity in sagittal alignment patterns was reported in idiopathic scoliosis, with global flattening of the spine being the most common. Kyphotic deformations occurring during growth are characterized by structural thoracic or thoracolumbar kyphosis compensated by lumbar hyperlordosis and lower pelvic incidence. Whereas in spondylolisthesis, altered morphology of the spinopelvic junction with high values of pelvic incidence is observed. Pain does not seem to be related to sagittal alignment in idiopathic scoliosis. In Scheuermann disease, it is localized at the apex of the deformity and is associated with the curve pattern, whereas in spondylolisthesis, sagittal alignment correlates with pain scores only in high-grade slips.

Conclusion

Most of the patients with spine disorders that occurred during growth present a clinically balanced posture in the sagittal plane. It suggests that compensatory mechanisms before achieving skeletal maturity are really significant. A comprehension of sagittal alignment in spine deformities and its relationship to pain is essential for the proper assessment and treatment of these disorders.

Association of Ligamentum Flavum Hypertrophy with Adolescent Idiopathic Scoliosis Progression-Comparative Microarray Gene Expression Analysis

The role of the ligamentum flavum (LF) in the pathogenesis of adolescent idiopathic scoliosis (AIS) is not well understood. Using magnetic resonance imaging (MRI), we investigated the degrees of LF hypertrophy in 18 patients without scoliosis and on the convex and concave sides of the apex of the curvature in 22 patients with AIS. Next, gene expression was compared among neutral vertebral LF and LF on the convex and concave sides of the apex of the curvature in patients with AIS. Histological and microarray analyses of the LF were compared among neutral vertebrae (control) and the LF on the apex of the curvatures. The mean area of LF in the without scoliosis, apical concave, and convex with scoliosis groups was 10.5, 13.5, and 20.3 mm2, respectively. There were significant differences among the three groups (p < 0.05). Histological analysis showed that the ratio of fibers (Collagen/Elastic) was significantly increased on the convex side compared to the concave side (p < 0.05). Microarray analysis showed that ERC2 and MAFB showed significantly increased gene expression on the convex side compared with those of the concave side and the neutral vertebral LF cells. These genes were significantly associated with increased expression of collagen by LF cells (p < 0.05). LF hypertrophy was identified in scoliosis patients, and the convex side was significantly more hypertrophic than that of the concave side. ERC2 and MAFB genes were associated with LF hypertrophy in patients with AIS. These phenomena are likely to be associated with the progression of scoliosis.

Effects of posterior hemivertebra resection and short segment fusion on the evolution of sagittal balance in children with congenital scoliosis

There is a paucity of data describing sagittal alignment changes in children with congenital scoliosis (CS) treated by hemivertebra (HV) resection. This study aimed to evaluate the effects of posterior HV resection on spine sagittal alignment in children with CS. This is a retrospective analysis of 31 children with CS (mean age at surgery: 49.61 ± 10.21 months; range, 39-72; mean follow-up time: 5.16 ± 1.21 years; range: 3-7) treated at our Institution. Only patients with single thoracic or single lumbar, fully segmented HV managed by posterior HV resection and two segments fusion with four screws and two robs were included. According to the anatomical location of the HV, patients were divided into two groups: thoracic (group A) and lumbar (group B). Thoracic kyphosis (T1-T12; TK) and lumbar lordosis (L1-S1; LL) were measured pre- and postoperatively at 6 months interval. Postoperative TK and LL were 30.3 ± 11.47 and 28.8 ± 9.47, and were 31.98 ± 9.66 and 46.7 ± 11.37 at the last follow-up visit, respectively. The incidence of thoracic hypokyphosis in group B was 53.3%, and it was significantly higher compared to group A (12.5%, P = 0.04). During follow-up, TK changes were comparable between the two groups of patients while LL improved in all patients 6 months after surgery, and continued to improve thereafter. Posterior HV resection and short segment fusion have limited impact on the evolution of TK; in particular, children with lumbar HV were more likely to be hypokyphotic preoperatively, but less likely postoperatively with an increase in LL and a stabilization of TK.

Morphological patterns of the rib cage and lung in the healthy and adolescent idiopathic scoliosis

The morphology of the rib cage affects both the biomechanics of the upper body's musculoskeletal structure and the respiratory mechanics. This becomes particularly important when evaluating skeletal deformities, as in adolescent idiopathic scoliosis (AIS). The aim of this study was to identify morphological characteristics of the rib cage in relation to the lung in patients with non‐deformed and scoliotic spines. Computed tomography data of 40 patients without any visible spinal abnormalities (healthy group) and 21 patients with AIS were obtained retrospectively. All bony structures as well as the right and left lung were reconstructed using image segmentation. Morphological parameters were calculated based on the distances between characteristic morphological landmarks. These parameters included the rib position, length, and area, the rib cage depth and width, and the rib inclination angle on either side, as well as the spinal height and length. Furthermore, we determined the left and right lung volumes, and the area of contact between the rib cage and lung. Differences between healthy and scoliotic spines were statistically analysed using the t‐test for unpaired data. The rib cage of the AIS group was significantly deformed in the dorso‐ventral and medio‐lateral directions. The anatomical proximity of the lung to the ribs was nearly symmetrical in the healthy group. By contrast, within the AIS group, the lung covered a significantly greater area on the left side of the rib cage at large thoracic deformities. Within the levels T1–T6, no significant difference in the rib length, depth to width relationship, or area was observed between the healthy and AIS groups. Inferior to the lung (T7–T12), these parameters exhibited greater variability. The ratio between the width of the rib cage at T6 and the thoracic spinal height (T1–T12) was significantly increased within the thoracic AIS group (1.1 ± 0.08) compared with the healthy group (1.0 ± 0.05). No statistical differences were found between the lung volumes among all the groups. While the rib cage was frequently strongly deformed in the AIS group, the lung and its surrounding ribs appeared to be normally developed. The observed rib hump in AIS appeared to be formed particularly by a more ventral position of the ribs on the concave side. Furthermore, the rib cage width to spinal height ratio suggested that the spinal height of the thoracic AIS‐spine is reduced. This indicates that the spine would gain its growth‐related height after correcting the spinal deformity. These are the important aspects to consider in the aetiology research and orthopaedic treatment of AIS.

Investigation of the Phenomenon of Coronal-Sagittal Curvature Coupling on Curve Progression: An Exploratory Study using 3-D Ultrasound

A 3-D ultrasound system was determined to provide reliable and valid results for scoliosis assessment in the coronal and sagittal planes. The objective of this study was to investigate whether 3-D ultrasound can detect coronal-sagittal coupling and to study its potential effect on curve progression in patients with adolescence idiopathic scoliosis (AIS) as per the traditional Cobb angle classification. Radiographic and ultrasonic coronal and sagittal curvatures of 126 patients with AIS were evaluated. Thoracic kyphosis (TK) and lumbar lordosis (LL) with different coronal deformity were compared correspondingly based on either main thoracic or (thoraco)lumbar curve groups. The TK and LL of patients with single curves were also compared with study the curve effect on sagittal curvatures. A prospective cohort of 51 patients were followed for an average of 23 months for preliminary progression investigation. TKs in patients with larger main thoracic Cobb angles was significantly smaller than those with smaller main thoracic Cobb angles, judging by the results obtained from ultrasound and X-ray. The TKs of patients with only single right main thoracic curves were significantly smaller than those of patients with only single left (thoraco)lumbar curves. In addition, patients with progressive curves were observed to be relative hypokyphotic during early visits.

Changes in peri-apical vertebral body and intervertebral disc shape in both the sagittal and coronal planes correlate with scoliosis severity: a 3D study of 397 patients

PURPOSE

To evaluate associations between vertebrae and disc shape asymmetry and adolescent idiopathic scoliosis (AIS) curve severity.

METHODS

Analysis included normal screening referrals and patients with right, main thoracic AIS who underwent upright, biplanar radiographs with 3D reconstruction at a single institution from 2010 to 2015. Peri-apical anterior, posterior, right, and left vertebral body heights (aVBH, pVBH, rVBH, lVBH) and intervertebral disc heights (DH) were measured, and ratios of these measurements were calculated in sagittal and coronal planes. Correlations were performed between curve severity and height measurements. Sagittal and coronal plane components of these measurements were compared between normal controls with coronal curve measurements < 11° and patients with moderate (11°-49°) and severe curves (≥ 50°), with tolerance intervals established for the normal controls.

RESULTS

The analysis included a total of 397 patients. Patients with AIS had coronal curve measurements ranging from 11° to 101°. Greater coronal curve severity strongly correlated with smaller pVBH relative to aVBH and moderately correlated with smaller pDH relative to aDH (r = - 0.643, r = - 0.305, respectively). aVBH was greater for larger curves; pVBH remained stable. Scoliosis severity strongly correlated with right relative to left VBH and DH ratios (r = 0.919, r = 0.865 respectively). In comparison of normal controls to severe curves, severe curves had significantly greater aVBH and aDH, while pVBH was not significantly different and pDH was significantly less. Nearly half (46.9%) of the severe curves were below the range of normal for PA vertebral height ratio.

CONCLUSION

In right, main thoracic AIS, greater main thoracic curve severity is associated with greater sagittal and coronal plane asymmetry of both the vertebral bodies and the discs. Severity more strongly correlates with vertebral changes in symmetry than with disc changes, though both are present.

Do Thoracic Spinal Deformities Affect Outcomes of Spinal Cord Stimulators: A Retrospective Chart Review

STUDY DESIGN

Retrospective chart review.

OBJECTIVE

The aim of this study was to ascertain whether the presence of structural thoracic deformities affects outcomes of permanent SCS placement.

SUMMARY OF BACKGROUND DATA

Neural modulation via spinal cord stimulators (SCSs) has become an accepted treatment option for various chronic pain syndromes. In most cases, the surgeon desires accurate midline positioning of the paddle lead, allowing for flexibility of unilateral or bilateral coverage of pain patterns. Structural spinal deformities (scoliosis or kyphosis) often result from coronal, sagittal, and rotatory deformity that can make midline placement more difficult.

METHODS

Between 2013 and 2017, two-hundred forty-one charts of patients who underwent permanent SCS placement at our suburban hospital were reviewed. Demographic information, numerical rating system (NRS) pain scores, Oswestry Disability Index (ODI) scores, and opioid medication usage were recorded at baseline and after permanent stimulator placement. Thoracic scoliosis and kyphosis angles were measured using spinal radiographs. The effect of each structural deformity on NRS, ODI, and narcotic medication usage changes from baseline was analyzed.

RESULTS

Overall, 100 patients were included in our cohort. Fifty-six patients had measured thoracic spinal deformities (38% with scoliosis, 31% with kyphosis). There was no significant difference in NRS scores, ODI scores, or narcotic usage change between patients with scoliosis and those without (P = 0.66, P = 0.57, P = 0.75) or patients with kyphosis and those without (P = 0.51, P = 0.31, P = 0.63). Bivariate linear regression analysis showed that scoliotic and kyphotic angles were not significant predictors of NRS (P = 0.39, P = 0.13), ODI (P = 0.45, P = 0.07), and opioid usage (P = 0.70, P = 0.90) change, with multivariate regression analyses confirming these findings.

CONCLUSION

SCSs can be effective options for treating lumbar back pain and radiculopathy. Our study suggests that the presence of mild structural deformities does not adversely affect outcomes of permanent SCS placement and as such should not preclude this population from benefiting from such therapies.Level of Evidence: 4.

TIMP2 Polymorphisms Association With Curve Initiation and Progression of Thoracic Idiopathic Scoliosis in the Caucasian Females

Idiopathic scoliosis (IS) etiology remains unclear, but strong genetic background is suggested. Previously reported TIMP2 study indicates an association of genic rs8179090 with IS progression in a Han Chinese population. However, there has been a lack of investigation into intragenic TIMP2 polymorphisms in IS patients. We recruited 100 Caucasian females with IS and 100 controls. Patients were subdivided accordingly to: progression rate, curve severity, joint mobility, and curve pattern. Allele-specific-polymerase chain reaction based on fluorescence resonance energy transfer was applied to evaluate nine TIMP2 polymorphisms. Distribution of genotype and allele frequency in only one polymorphism (rs11658743) differed in case-control study. Four of the polymorphisms (rs2277700, rs11077401, rs2376999, and rs4789934) showed non-equal distributions either in genotype or/and allele distributions in the patients of different progression rates. The rs11077401 was related to curve severity patients distinction and the rs8179090 distinguished patients with different joint mobility level. Two polymorphisms either differed statistically in case of curve patterns subgrouping (rs8068674 and rs8179090) or showed a slight tendency toward significance in the recessive model of allele distributions (rs9916809 and rs8179090). The remaining two polymorphisms (rs2377005, rs11658743) showed no association with either clinical or radiographic IS characteristics. The influence of the G allele of the rs8179090 on the clinical course of IS has not yet been confirmed. We identified four TIMP2 polymorphisms (rs11077401, rs2376999, rs2277700, and rs4789934) that were associated with a higher risk of the progressive IS form. Further genetic association studies based on suggested clinical criteria would be necessary to validate TIMP2 polymorphisms associated with the curve progression. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2217-2225, 2019.

Theory of Bowstring Disease: Diagnosis and Treatment Bowstring Disease

Bowstring disease (BSD) is a new classification of spine disease caused by axial stretched lesion on nerve roots and the spinal cord, which is differentiated from disc herniation and canal stenosis in that it is caused by nerve compression lesions. BSD could be caused by mismatched growth rates between the spine and nerve roots (the juvenile type), or by imbalanced degenerative rates between the spine column and nerve roots (degenerative type). Here, we propose that there are several self-adjust mechanisms to relieve axial nerve tension: (i) nerve growth; (ii) posture adjustment and low back pain; (iii) autogenous degeneration of intervertebral disc; and (iv) idiopathic and degenerative scoliosis. Iatrogenic lesions could also result in BSD, which could be presented as adjacent segment degeneration, leading to adding-on effects and other neurological symptoms. The diagnosis criteria are proposed based on symptoms, physical examination, and radiological presentations. To remove axial tension on nerve roots, lumbar surgery should aim to restore the coordination of spine and cord units. Capsule surgery, shortening the spine column, could decompress cord and nerve roots 3-dimensionally.

Anterior-posterior length discrepancy of the spinal column in adolescent idiopathic scoliosis-a 3D CT study

BACKGROUND CONTEXT

One of the characteristics of reported observations in adolescent idiopathic scoliosis (AIS) is that the thoracic spine is longer anteriorly than posteriorly, more pronounced around the apex than the transitional zones. This reversal of the normal kyphotic anatomy of the thoracic spine is related to questions of etiopathogenesis of AIS. The changes in the anatomy of the anterior column have been described rather in detail; however, the role of the posterior spinal column and the laminae has so far not been elucidated. If the posterior column exhibits a longitudinal growth disturbance, it could act as a tether, leading to a more or less normal anterior column with a deformed and shorter posterior aspect of the spine. So far, it has remained unclear whether this anterior-posterior length discrepancy is the result of relative anterior lengthening or relative posterior shortening, and which tissues (bone, disc, intervertebral soft tissue) are involved.

PURPOSE

The present study aimed to compare the discrepancy of the anterior-posterior length of the spinal column in the "true" midsagittal plane of each vertebra in patients with idiopathic scoliosis versus controls, using three-dimensional computed tomography (CT) scans.

STUDY DESIGN/SETTING

This is a cross-sectional study.

PATIENT SAMPLE

The sample consisted of computed tomography scans of 80 patients with moderate to severe AIS (Cobb angle: 46°-109°) before scoliosis navigation surgery and 30 non-scoliotic age-matched controls.

OUTCOME MEASURES

The height of the osseous and non-osseous structures from anterior to posterior in the "true" midsagittal plane has been determined: the anterior side of the vertebral body and disc, the posterior side of the vertebral body and disc, the lamina and interlaminar space and the spinous process and interspinous space, as well as the height ratios between the anterior column and posterior structures of the primary thoracic and lumbar AIS curves and corresponding levels in non-scoliotic controls.

METHODS

Semiautomatic software was used to reconstruct and measure the parameters in the true midsagittal plane of each vertebra and intervertebral structure that are rotated and tilted in a different way.

RESULTS

In AIS, the anterior height of the thoracic curve was 3.6±2.8% longer than the posterior height, 2.0±6.1% longer than the length along the laminae, and 8.7±7.1% longer than the length along the spinous processes, and this differed significantly from controls (-2.7±2.4%, -7.4±5.2%, and +0.7±7.8%; p<.001). The absolute height of the osseous parts did not differ significantly between AIS and controls in the midsagittal plane. In contrast, the intervertebral structures contributed significantly to the observed length discrepancies. In absolute lengths, the anterior side of the disc of the thoracic curve was higher in AIS (5.4±0.8 mm) than controls (4.8±1.0 mm; p<.001), whereas the interspinous space was smaller in AIS (12.3±1.4 mm vs. 14.0±1.6 mm; p<.001).

CONCLUSIONS

Based on this in vivo analysis, the true three-dimensional anterior-posterior length discrepancy of AIS curves was found to occur through both anterior column lengthening and posterior column shortening, with the facet joints functioning as the fulcrum. The vertebrae contribute partly to the anterior-posterior length discrepancy accompanied by more significant and possibly secondary increased anterior intervertebral discs height.

Effect of Asymmetric Tension on Biomechanics and Metabolism of Vertebral Epiphyseal Plate in a Rodent Model of Scoliosis

OBJECTIVE

To investigate the effect of asymmetric tension on idiopathic scoliosis (IS) and to understand its pathogenic mechanism.

METHODS

The rodent model of scoliosis was established using Sprague-Dawley rats with left rib-tethering from T₆ to T₁₂ , tail and shoulder amputation, and high-cage feeding. Vertebrae epiphyseal cartilage plates were harvested from the convex and concave sides. To analyze differences on the convex and concave sides, finite element analysis was carried out to determine the mechanical stress. Protein expression on epiphyseal cartilage was evaluated by western blot. Micro-CT was taken to evaluate the bone quality of vertebral on both sides.

RESULTS

Scoliosis curves presented in X-ray radiographs of the rats. Finite element analysis was carried out on the axial and transverse tension of the spine. Stresses of the convex side were -170.14, -373.18, and -3832.32 MPa (X, Y, and Z axis, respectively), while the concave side showed stresses of 361.99, 605.55, and 3661.95 MPa. Collagen type II, collagen type X, Sox 9, RunX2, VEGF, and aggrecan were expressed significantly more on the convex side (P < 0.05). There was asymmetric expression of protein on the epiphyseal cartilage plate at molecular level. Compared with the convex side, the concave side had significantly lower value in the BV/TV and Tb.N, but higher value in the Tb.Sp (P < 0.05). There was asymmetry of bone quality in micro-architecture.

CONCLUSIONS

In this study, asymmetric tension contributed to asymmetry in protein expression and bone quality on vertebral epiphyseal plates, ultimately resulting in asymmetry of anatomy. In addition, asymmetry of anatomy aggravated asymmetric tension. It is the first study to show that there is an asymmetrical vicious circle in IS.

Characteristic morphological patterns within adolescent idiopathic scoliosis may be explained by mechanical loading

PURPOSE

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine which exhibits morphological changes during growth. The goal of this study was to identify morphological patterns that could be explained by different loading patterns for AIS.

METHODS

Computed tomography data of 21 patients with diagnosed AIS and 48 patients without any visual spinal abnormalities were collected prospectively. The bony structures were reconstructed, and landmarks were placed on characteristic morphological points on the spine. Multiple morphological parameters were calculated based on the distances between the landmarks. The intra- and inter-observer variability for each parameter was estimated. Differences between healthy and scoliotic spines were statistically analysed using the t test for unpaired data, with a significance level of α = 0.01.

RESULTS

Within the healthy group, an out-of-plane rotation of the vertebrae in the transverse plane was measured (2.6° ± 4.1° at T2). Relating the length of the spinal curvature to the T1-S1 height of the spine revealed that scoliotic spines were significantly longer. However, the endplate area in the AIS group was significantly smaller once compared to the curvature length. The relation between the left and right pedicle areas varied between 2.5 ± 0.79 and 0.4 ± 0.19, while the ratio of the facet articular surfaces varied within 2.3 ± 0.5 and 0.5 ± 0.2.

CONCLUSIONS

This study identified a certain morphological pattern along the spine, which reveals a distinct load path prevalent within AIS. The data suggested that the spine adapts to the asymmetric load conditions and the spine is not deformed by asymmetric growth disturbance. These slides can be retrieved under Electronic Supplementary Material.

T1-weighted MR imaging of bone marrow pattern in children with adolescent idiopathic scoliosis: a preliminary study

PURPOSE

Distinct normal physiological patterns of fat conversion in vertebrae were described both for children and adults. Our aim was to evaluate the T1-weighted bone marrow pattern of the vertebral bodies in various sites along the scoliotic spine of children with adolescent idiopathic scoliosis (AIS).

METHODS

We retrospectively evaluated spine MRI studies of children with AIS. Scoliosis radiographs were assessed for type of curvature according to the Lenke classification. A paediatric neuroradiologist assessed the T1-weighted signal of vertebral bodies in comparison with the adjacent disc and distinct patterns of fatty conversion within the apical and stable vertebral bodies. Statistical assessment was performed.

RESULTS

MRI study of the spines of 75 children with AIS were assessed, 59 (79%) of whom were female, with an age range of nine to 19 years. The relative overall T1-weighted signal intensity of the vertebral body bone marrow relative to the intervertebral disc was hyperintense in 76% and isointense in 24%. Fatty conversion grade of the stable vertebra was higher than the apex vertebra (p = 0.0001). A significant tendency to have more advanced fat conversion patterns in the apex vertebra up to age 13.5 years old compared with adolescents above that (p = 0.015) was seen.

CONCLUSION

This preliminary study suggests a different pattern of bone marrow conversion in AIS from the normal physiologic pattern described in the literature. Whether these changes are secondary to the biomechanics of the curved spine or may suggest that bone marrow maturation rate and content have a role in the pathogenesis of AIS remains to be further researched.

LEVEL OF EVIDENCE

Level III (Diagnostic Study).

Etiological Theories of Adolescent Idiopathic Scoliosis: Past and Present

Adolescent idiopathic scoliosis is one of the most common spinal deformities, yet its cause is unknown. Various theories look to biomechanical, neuromuscular, genetic, and environmental origins, yet our understanding of scoliosis etiology is still limited. Determining the cause of a disease is crucial to developing the most effective treatment. Associations made with scoliosis do not necessarily point to causality, and it is difficult to determine whether said associations are primary (playing a role in development) or secondary (develop as a result of scoliosis). Scoliosis is a complex condition with highly variable expression, even among family members, and likely has many causes. These causes could be similar among homogenous groups of AIS patients, or they could be individual. Here, we review the most prevalent theories of scoliosis etiology and recent trends in research.

THE ETIOLOGIC RELEVANCE OF 3-D PATHOANATOMY OF ADOLESCENT IDIOPATHIC SCOLIOSIS

ABSTRACT Despite many years of dedicated research into the etiopathogenesis of adolescent idiopathic scoliosis, there is still no single distinct cause for this puzzling condition. In this overview, we attempt to link knowledge on the complex three-dimensional pathoanatomy of AIS, based on our ongoing research in this field, with etiopathogenic questions. Evidence from multiple recent cross-sectional imaging studies is provided that supports the hypothesis that AIS has an intrinsic biomechanical basis: an imbalance between the biomechanical loading of the upright human spine due to its unique sagittal configuration on the one hand, and the body’s compensating mechanisms on the other. The question that remains in the etiology of AIS, and the focus of our ongoing research, is to determine what causes or induces this imbalance.

More preoperative flexibility implies adequate neural pliability for curve correction without prophylactic untethering in scoliosis patients with asymptomatic tethered spinal cord, a retrospective study

Background

Tethered spinal cord is frequently associated with scoliosis. It is still controversial whether a prophylactic untethering is necessary before correction procedure in scoliosis patients with tethered spinal cord. In this study we determined the clinical outcome of a one-stage posterior scoliosis correction without a prophylactic untethering for treating scoliosis with an asymptomatic tethered spinal cord.

Methods

Seventeen (5 males and 12 females) scoliosis patients with tethered spinal cords were retrospectively reviewed. All patients underwent a one-stage posterior scoliosis correction without preventive untethering. Parameters of radiograph were used to assess correction result. The Scoliosis Research Society (SRS)-22 questionnaire was analyzed pre- and post-operatively to evaluate the clinical outcomes. The modified Japanese Orthopaedic Association (mJOA) score was used to assess the pre- and post-operative spinal cord function.

Results

The post-operative coronal Cobb angle was significantly decreased compared with preoperative. (23.8 ± 6.4° vs. 58.4 ± 12.6°, P < 0.01). The coronal Cobb angle was 22.4 ± 6.8° at the final follow-up evaluation. The apical vertebral translation (AVT) was also decreased significantly. (27.5 mm vs. 60.9 mm, P < 0.01). The SRS-22 total score was improved at the 1-year follow-up evaluation compared with the pre-operative SRS-22 total score (87 ± 4 vs. 70 ± 5, p < 0.05). The functional activities, pain, self-image, mental health, and surgery satisfactory scores at the final follow-up evaluation were all improved compared with the corresponding pre-operative scores, especially the self-image and mental health scores (p < 0.05). The spinal cord function was stable and there was no new neurological symptoms after scoliosis correction. No difference existed between the pre- and post-operative total mJOA score (26 ± 2 vs. 27 ± 2, p = 0.39), which including subjective symptom (p = 0.07), clinical symptom (p = 0.33), daily activities (p = 0.44) and bladder function (p = 0.67).

Conclusion

One-stage posterior scoliosis correction is a safe and effective surgical procedure for scoliosis patients combined with asymptomatic tethered spinal cord who have adequate spinal cord function reserve.

Restrained Differential Growth: The Initiating Event of Adolescent Idiopathic Scoliosis?

STUDY DESIGN

An experimental model study and a short review of literature.

OBJECTIVE

The purpose of this study was to explore a new hypothesis suggesting that the curvatures seen in adolescent idiopathic scoliosis (AIS) originate from restrained differential growth between the vertebral column and the surrounding musculo-ligamentary structures.

SUMMARY OF BACKGROUND DATA

Despite decades of research, there is no generally accepted theory on the physical origin of the severe spinal deformations seen in AIS. The prevailing theories tend to focus on left-right asymmetry, rotational instability, or the sagittal spinal profile in idiopathic scoliosis.

METHODS

We test our hypothesis with a physical model of the spine that simulates growth, counteracted by ligaments and muscles, modeled by tethers and springs. Growth of the spine is further restrained by an anterior band representing the thorax, the linea alba, and abdominal musculature. We also explore literature in search of molecular mechanisms that may induce differential growth.

RESULTS

Differential growth in the restrained spine model first induces hypokyphosis and mild lateral bending of the thoracic spine, but then suddenly escalates into a scoliotic deformity, consistent with clinical observations of AIS. The band simulating the ventral structures of the body had a pivotal effect on sagittal curvature and the initiation of lateral bending and rotation. In literature, several molecular mechanisms were found that may explain the occurrence of differential growth between the spine and the musculo-ligamentary structures.

CONCLUSION

While AIS is a three-dimensional deformation of the spine, it appears that restrained differential growth in the sagittal plane can result in lateral bending and rotation without a pre-existing left-right asymmetry. This supports the concept that AIS may result from a growth imbalance rather than a local anatomical defect.

LEVEL OF EVIDENCE

N/A.

Predicting 3D Thoracic Kyphosis Using Traditional 2D Radiographic Measurements in Adolescent Idiopathic Scoliosis

STUDY DESIGN

Retrospective.

OBJECTIVE

To develop and validate a prediction formula to estimate three-dimensional (3D) T5-T12 kyphosis in adolescent idiopathic scoliosis (AIS) from standard two-dimensional (2D) radiographic measurements.

SUMMARY OF BACKGROUND DATA

2D measurements of thoracic kyphosis in AIS patients overestimate 3D kyphosis; however, there is a lack of widespread availability of 3D imaging technology.

METHODS

Retrospective review was performed for AIS patients with right thoracic curves evaluated with EOS Imaging from January 2010 to June 2014. Standard 2D posteroanterior and lateral radiographic measurements, pelvic incidence, Nash-Moe grade, Perdriolle rotation, and "3D T5-T12" sagittal measures (reconstructed with sterEOS, analyzed with custom MatLab code) were input into a multivariate logistic analysis to create a prediction model for 3D T5-T12 sagittal alignment. An initial cohort of 66 patients (curves 14°-85°) was used to create a predictive model, and a separate cohort of 129 patients (curves 16°-84°) was used to validate the formula.

RESULTS

2D thoracic coronal Cobb and 2D T5-T12 kyphosis were the only significant predictors in the model. The prediction formula for estimating 3D T5-T12 sagittal measurement from standard 2D measurements, in degrees, was 18.1 + (0.81*2D T5-T12 sagittal Cobb) - (0.54*2D coronal Cobb), r² = 0.84. The average model error between predicted and measured 3D T5-T12 kyphosis was ±7°. The predicted 3D T5-T12 kyphosis (8.6° ± 12.1°) and measured 3D T5-T12 kyphosis (8.5° ± 13.0°) were not significantly different (p = .8). 3D kyphosis was less than standard measures of 2D kyphosis (8.5° ± 13.0° vs. 20.2° ± 12.6°, p < .001).

CONCLUSION

This simple validated formula to predict 3D T5-T12 sagittal alignment using routine 2D thoracic Cobb and T5-T12 kyphosis for thoracic AIS patients has great potential value in assessing historical data collected prior to the development of 3D imaging methods as well as understanding/planning surgical hypokyphosis correction in patients without access to 3D imaging.

Anterior Overgrowth in Primary Curves, Compensatory Curves and Junctional Segments in Adolescent Idiopathic Scoliosis

Introduction

Although much attention has been given to the global three-dimensional aspect of adolescent idiopathic scoliosis (AIS), the accurate three-dimensional morphology of the primary and compensatory curves, as well as the intervening junctional segments, in the scoliotic spine has not been described before.

Methods

A unique series of 77 AIS patients with high-resolution CT scans of the spine, acquired for surgical planning purposes, were included and compared to 22 healthy controls. Non-idiopathic curves were excluded. Endplate segmentation and local longitudinal axis in endplate plane enabled semi-automatic geometric analysis of the complete three-dimensional morphology of the spine, taking inter-vertebral rotation, intra-vertebral torsion and coronal and sagittal tilt into account. Intraclass correlation coefficients for interobserver reliability were 0.98–1.00. Coronal deviation, axial rotation and the exact length discrepancies in the reconstructed sagittal plane, as defined per vertebra and disc, were analyzed for each primary and compensatory curve as well as for the junctional segments in-between.

Results

The anterior-posterior difference of spinal length, based on “true” anterior and posterior points on endplates, was +3.8% for thoracic and +9.4% for (thoraco)lumbar curves, while the junctional segments were almost straight. This differed significantly from control group thoracic kyphosis (-4.1%; P<0.001) and lumbar lordosis (+7.8%; P<0.001). For all primary as well as compensatory curves, we observed linear correlations between the coronal Cobb angle, axial rotation and the anterior-posterior length difference (r≥0.729 for thoracic curves; r≥0.485 for (thoraco)lumbar curves).

Conclusions

Excess anterior length of the spine in AIS has been described as a generalized growth disturbance, causing relative anterior spinal overgrowth. This study is the first to demonstrate that this anterior overgrowth is not a generalized phenomenon. It is confined to the primary as well as the compensatory curves, the junctional zones do not exhibit this growth discrepancy, however, they are straight.

A comparison of four techniques to measure anterior and posterior vertebral body heights and sagittal plane wedge angles in adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) spinal deformity of unknown aetiology. Increased growth of the anterior part of the vertebrae known as anterior overgrowth has been proposed as a potential driver for AIS initiation and progression. To date, there has been no objective evaluation of the 3D measurement techniques used to identify this phenomenon and the majority of previous studies use 2D planar assessments which contain inherent projection errors due to the vertebral rotation which is part of the AIS deformity. In this study, vertebral body (VB) heights and wedge angles were measured in a test group of AIS patients and healthy controls using four different image analysis and measurement techniques. Significant differences were seen between the techniques in terms of VB heights and VB wedge angles. The low variability, and the fact that the rotation and tilt of the deformed VBs are taken into account, suggests that the proposed technique using the full 3D orientation of the vertebrae is the most reliable method to measure anterior and posterior VB heights and sagittal plane wedge angles in 3D image data sets. These results have relevance for future investigations that aim to quantify anterior overgrowth in AIS patients for comparison with healthy controls.

Quantifying Progressive Anterior Overgrowth in the Thoracic Vertebrae of Adolescent Idiopathic Scoliosis Patients: A Sequential Magnetic Resonance Imaging Study

STUDY DESIGN

Anterior and posterior vertebral body heights were measured from sequential magnetic resonance imaging (MRI) scans of adolescent idiopathic scoliosis (AIS) patients and healthy controls.

OBJECTIVE

To measure changes in vertebral body height over time during scoliosis progression to assess how vertebral body height discrepancies change during growth.

SUMMARY OF BACKGROUND DATA

Relative anterior overgrowth has been proposed as a potential driver for AIS initiation and progression. This theory proposes that the anterior column grows faster, and the posterior column slower, in AIS patients when compared with healthy controls. There is a disagreement in the literature as to whether the anterior vertebral body heights are proportionally greater than posterior vertebral body heights in AIS patients when compared with healthy controls. To some extent, these discrepancies may be attributed to methodological differences.

METHODS

MRI scans of the major curve of 21 AIS patients (mean age 12.5 ± 1.4 years, mean Cobb 32.2 ± 12.8 degrees) and between T4 and T12 of 21 healthy adolescents (mean age 12.1 ± 0.5 years) were captured for this study. Of the 21 AIS patients, 14 had a second scan on average 10.8 ± 4.7 months after the first. Anterior and posterior vertebral body heights were measured from the true sagittal plane of each vertebra such that anterior overgrowth could be quantified.

RESULTS

The difference between anterior and posterior vertebral body height in healthy, nonscoliotic children was significantly greater than in AIS patients with mild to moderate scoliosis. There was; however, no significant relationship between the overall anterior-posterior vertebral body height difference in AIS and either severity of the curve or its progression over time.

CONCLUSION

Whilst AIS patients have a proportionally longer anterior column than nonscoliotic controls, the degree of anterior overgrowth was not related to the rate of progression or the severity of the scoliotic curve.

LEVEL OF EVIDENCE

3.

Scoliosis may be the first symptom of the tethered spinal cord

BACKGROUND

Tethered cord syndrome (TCS) is a progressive clinical entity that arises from abnormal spinal cord tension. Scoliosis may be a unique symptom in TCS. The aim of this study is to investigate prognosis after releasing the filum terminale in scoliosis due to TCS with/without findings in magnetic resonance imaging (MRI) and to draw attention to the importance of somatosensorial evoked potentials (SSEP) on the differential diagnosis of idiopathic scoliosis versus scoliosis due to TCS with normal appearance of filum terminale and conus medullaris.

MATERIALS AND METHODS

Eleven female and seven male patients with progressive scoliosis were included in the study. They were evaluated radiologically, SSEP and urodynamical studies. Preoperative and postoperative anteroposterior full spine X-rays were obtained for measuring the Cobb's angle. MRI was performed in all cases for probable additional spinal abnormalities. All patients underwent filum terminale sectioning through a L5 hemilaminectomy. The resected filum terminale were subjected to histopathological examination.

RESULTS

The mean Cobb angle was 31.6° (range 18°-45°). Eight patients (44.45%) had a normal appearance of filum terminale and normal level conus medullaris in MRI, but conduction delay and/or block was seen on SSEP. In the histopathological examination of filum terminale dense collagen fibers, hyaline degeneration and loss of elastic fibers were observed. Postoperatively none of the patients showed worsening of the Cobb angle. Three patients showed improvement of scoliosis.

CONCLUSION

In TCS presented with scoliosis, untethering must be performed prior to the corrective spinal surgery. Absence of MRI findings does not definitely exclude TCS. SSEP is an important additional guidance in the diagnosis of TCS. After untethering, a followup period of 6 months is essential to show it untethering helps in stopping the progress of the scoliotic curve. In spite of non progression (curve stopped lesser than 45°) or even improvement of scoliosis, there may be no need for major orthopedic surgical intervention.

MRI-based morphological evidence of spinal cord tethering predicts curve progression in adolescent idiopathic scoliosis

BACKGROUND CONTEXT

Existing prognostic factors for adolescent idiopathic scoliosis (AIS) patients have focused mainly on curve, maturity, and bone-related factors. Previous studies have shown significant associations between curve severity and morphological evidences of relative shorter spinal cord tethering in AIS, and increased prevalence of abnormal somatosensory cortical-evoked potentials and low-lying cerebellar tonsil in severe AIS. Earlier evidence suggests that there might be neural morphological predictors for curve progression.

PURPOSE

The purpose of this study was to identify any morphological predictors associated with cord tethering, as measured by magnetic resonance imaging (MRI), for curve progression in AIS patients.

STUDY DESIGN/SETTING

This is a prospective cohort study.

PATIENT SAMPLE

A total of 81 female AIS subjects between 10 and 14 years were included, without surgical intervention during the follow-up period.

OUTCOME MEASURES

Magnetic resonance imaging scans of hindbrain and whole spine and areal bone mineral density (BMD) at bilateral femoral necks were performed.

METHODS

All AIS patients were longitudinally followed up starting from initiation of bracing beyond skeletal maturity in 6-month intervals. Clinical and radiographic data were recorded at each clinic visit. Bone mineral density and MRI measurements including ratio of spinal cord to vertebral column length, ratio of anteroposterior (AP) and transverse (TS) diameter of cord, lateral cord space (LCS) ratio, cerebellar tonsil level, and conus medullaris position were obtained at baseline. Only compliant patients with a minimum 2-year follow-up were analyzed. Adolescent idiopathic scoliosis girls were assigned into three groups according to bracing outcome: Group A, nonprogression (curvature increase of less than or equal to 5°); Group B, progression (curvature increase of greater than or equal to 6°); Group C, progression with surgery indication (Cobb angle of greater than or equal to 50° after skeletal maturity despite bracing). The predictors for curve progression were evaluated using univariate analysis and multivariate ordinal regression model.

RESULTS

The average duration of follow-up was 3.4 (range, 2.0-5.6) years. There were 46 girls (57%) in Group A, 19 (23%) in Group B, and 16 (20%) in Group C. No significant intergroup differences were found in spinal cord length, tonsil level, and conus position. Group C had significantly longer vertebral column length, smaller cord-vertebral length ratio, and higher AP/TS cord ratio compared with Group A, whereas LCS ratio in Group C was significantly increased compared with both Group A and Group B. In regression model, five significant independent predictors including cord-vertebral length ratio (odds ratio [OR]: 1.993 [95% confidence interval {CI}: 1.053-3.771], p=.034), LCS ratio (OR: 2.639 [95% CI: 1.128-6.174], p=.025), initial Cobb angle (OR: 1.156 [95% CI: 1.043-1.281], p=.006), menarche age (OR: 1.688 [95% CI: 1.010-2.823], p=.046), and BMD (OR: 2.960 [95% CI: 1.301-6.731], p=.010) and a marginally significant predictor namely AP/TS cord ratio (OR: 1.463 [95% CI: 0.791-2.706], p=.096) were obtained.

CONCLUSIONS

On baseline MRI measurement, cord-vertebral length ratio and LCS ratio are identified as new significant independent predictors for curve progression in AIS, whereas AP/TS cord ratio is suggested as a potential predictor requiring further validations. The earlier MRI parameters can be taken into accounts for prognostication of bracing outcome.

Three-dimensional spinal morphology can differentiate between progressive and nonprogressive patients with adolescent idiopathic scoliosis at the initial presentation: a prospective study

STUDY DESIGN

This is a prospective case-control study.

OBJECTIVE

The objective of this study was to compare 3-dimensional (3D) morphological parameters of the spine at the first visit between a nonprogressive (NP) and a progressive (P) group of immature adolescent idiopathic scoliosis (AIS).

SUMMARY OF BACKGROUND DATA

Prediction of curve progression remains challenging in AIS at the first visit. Prediction of progression is based on curve type, curve magnitude, and skeletal or chronological age.

METHODS

A prospective cohort of 133 AIS was followed from skeletal immaturity to maturity (mean, 37 mo). The first group was made up of patients with AIS with a minimum 6-degree progression of the major curve between the first and last follow-up (P) (n = 53) and the second group was composed of patients with NP who reached maturity with less than 6-degree progression (n = 81). Computerized measurements were taken on reconstructed 3-dimensional (3D) spine radiographs of the first visit. There were 6 categories of measurements: angle of plane of maximum curvature, Cobb angles (kyphosis, lordosis), 3D wedging (apical vertebra, apical disks), rotation (upper and lower junctional vertebra, apical vertebra, and thoracolumbar junction), torsion, and slenderness (height/width ratio). t tests were also conducted.

RESULTS

There was no statistical difference between the 2 groups for age and initial Cobb angle. P presented significant hypokyphosis, and parameters related to rotation presented significant statistical differences between NP and P (plane of maximal curvature, torsion, and apical axial rotation). Depth slenderness also presented statistical differences.

CONCLUSION

This study confirms that even at the initial visit, 3D morphological differences exist between P and NP AIS. It supports the use of 3D reconstructions of the spine in the initial evaluation of AIS to help predict outcome.

Effect of anterior mobilization and shortening in the correction of rigid idiopathic thoracic scoliosis

STUDY DESIGN

Retrospective study of patients with anterior release and posterior correction instrumentation in a 2-stage procedure for rigid thoracic scoliosis.

OBJECTIVE

To examine the effect of the anterior release and shortening alone as well as its role in the overall correction.

SUMMARY OF BACKGROUND DATA

With segmental transpedicular instrumentation the need for an additional anterior mobilization became rare. However, its effect on sagittal profile was not sufficiently acknowledged.

METHODS

Twenty-two patients with rigid thoracic scoliosis (Lenke 1A, n = 3; 2A, n = 6; 2B, n = 2; 2C, n = 1; 4B, n = 1; 4C, n = 9 patients) were operated in a 2-stage procedure with anterior release followed by posterior correction. The anterior release included convex resection of the rib heads and shortening of the anterior column by resection of the discs and the convex anterolateral endplates in a mean of 8 (4-11) segments.After 14 days (6-27), the posterior instrumentation and correction was done.

RESULTS

The preoperative thoracic scoliosis measured a mean of 80°, upper thoracic 42°, and lumbar 49°. The thoracic curve corrected in bending 20° (25%), upper thoracic 10° (24%), and lumbar 26° (53%). The mean thoracic kyphosis (T5-T12) was 11°, lumbar lordosis was -41°.After the anterior release and shortening, thoracic scoliosis improved to 50°, thoracic kyphosis increased to 32°.After the posterior surgery the following values were noted: thoracic scoliosis 10°, upper thoracic 9°, lumbar 8°, thoracic kyphosis 25°, and lumbar lordosis -41°. The results were maintained at follow-up.

CONCLUSION

Anterior shortening results in a spontaneous correction of the thoracic scoliosis and hypokyphosis. In this series, the Cobb angle reduced 38% from a mean of 80° to a mean of 50°. Thoracic kyphosis increased from 11° to 32°. This correction was achieved without any corrective force or instrumentation. The second-stage posterior correction is facilitated and nearly complete correction is achieved with a residual curve on average of 10° with a physiological sagittal profile.

LEVEL OF EVIDENCE

4.

Clinical anatomy of vertebrae in scoliosis: global analysis in four different diseases by multiplanar reconstructive computed tomography

BACKGROUND CONTEXT

Few accurate analyses of clinically useful vertebral anatomy have been conducted, and most have focused on thoracic idiopathic scoliosis.

PURPOSE

To evaluate the different anatomic characteristics in scoliosis by disease type and level.

STUDY DESIGN

Observational cohort study.

PATIENT SAMPLE

Forty-eight patients with scoliosis were included in this study.

OUTCOME MEASURES

Subjects underwent computed tomography (CT) of the whole spine.

METHODS

Forty-eight patients with scoliosis were included in this study: 15 adolescent idiopathic, 11 cerebral palsy (CP), 10 muscular dystrophy (MD), and 12 congenital (CG) scoliosis patients with similar demographics. Subjects underwent CT of the whole spine, preoperatively. Eight anatomic parameters were measured in multiplanar reconstructive CT images, and statistical analysis was performed to investigate differences.

RESULTS

In general, values in the anatomic parameters were similar for the four diseases. Each parameter showed the unique change pattern according to the spinal level regardless of curvature shape, direction, or magnitude. In particular, chord length (CL) in MD and CG scoliosis was lower than in adolescent idiopathic scoliosis (AIS) and CP, and pedicle rib unit length was lower in CG scoliosis than in the other diseases (p<.05). Comparisons of convex and concave anatomies in AIS showed that inner pedicle width (PWI) and outer pedicle width (PWO) were wider for convex side, CL, pedicle width, and transverse pedicle angle were greater for concave side (p<.05), and differences were more significant at apices. However, in CP, PWI and PWO were similar between convex and concaves sides (p>.05). Although PWI and PWO were wider for convex sides and CL and pedicle length were greater for concave sides in MD (p<.05), differences were less significant at apices. Particularly, CG scoliosis showed severely deformed anatomy, with differences of seven parameters at apical vertebrae (p<.05).

CONCLUSION

Clinical anatomies of vertebrae in scoliosis were found to differ significantly at different levels and in terms of convexity and disease type.

Comparison of harrington rod and cotrel-dubousset devices in surgical correction of adolescent idiopathic scoliosis

Background

Since the time of Paul Harrington numerous implants have been introduced for correction of scoliosis, but none are ideal. Newer devices are very expensive, and in our country some patients cannot afford them.

Objectives

The aim of this study was to compare the results of the Harrington rod (HR) device and the newer Cotrel-Dubousset (CD) device in treatment of adolescent idiopathic scoliosis (AIS).

Materials and Methods

A retrospective review assessed patients with AIS admitted for spinal curve correction treated with HR (n = 120) and CD devices (n = 138) between October 1988 to April 2001 at the Shafa Yahyaeian Hospital, Tehran, Iran. We extracted information from the patient’s file and radiographs before, after and two years post-operation.

Results

The mean age of patients was 16.7 ± 2.5 years. There was no statistically significant difference between the two groups regarding gender, age, curve before surgery, and percentage of flexibility. The mean curvature was 70 ± 20.7 in the HR and 64.81 ± 19.4 in the CD group before surgery (P = 0.09); and the mean curvature was 40 ± 16.3 and 26.58 ± 15.37 in HR and CD groups respectively after surgery (P = 0.156). The mean curvature was 47.2 ± 15.9 in HR and 31.2 ± 15.4 in CD groups at two years follow-up (P = 0.156).

Conclusions

Results of many studies have shown no significant impairment in long-term quality of life and function in patients treated with Harrington rods. According to previously performed studies and the current study, surgical correction with Harrington rods seem to be comparable with the newer more expensive CD device. Although there is no doubt that the preference is to use newer devices in view of some disadvantages of HR, but this does not preclude using it for patients that cannot afford the newer devices.

Changes in CSF flow after one-stage posterior vertebral column resection in scoliosis patients with syringomyelia and Chiari malformation Type I

Object

Phase contrast–cine MRI (PC-cine MRI) studies in patients with syringomyelia and Chiari malformation Type I (CM-I) have demonstrated abnormal CSF flow across the foramen magnum, which can revert to normal after craniocervical decompression with syrinx shrinkage. In order to investigate the mechanisms leading to postoperative syringomyelia shrinkage, the authors studied the hydrodynamic changes of CSF flow in the craniocervical junction and spinal canal in patients with scoliosis associated with syringomyelia after one-stage deformity correction by posterior vertebral column resection.

Methods

Preoperative and postoperative CSF flow dynamics at the levels of the foramen magnum, C-7, T-7 (or apex), and L-1 were assessed by electrocardiogram-synchronized cardiac-gated PC-cine MRI in 8 adolescent patients suffering from severe scoliosis with syringomyelia and CM-I (scoliosis group) and undergoing posterior vertebral column resection. An additional 8 patients with syringomyelia and CM-I without spinal deformity (syrinx group) and 8 healthy volunteers (control group) were also enrolled. Mean values were obtained for the following parameters: the duration of a CSF cycle, the duration of caudad CSF flow (CSF downflow [DF]) and cephalad CSF flow (CSF upflow [UF]), the ratio of DF duration to CSF cycle duration (DF%), and the ratio of UF duration to CSF cycle duration (UF%). The ratio of the stationary phase (SP) duration to CSF cycle duration was calculated (SP%). The maximum downflow velocities (VDmax) and maximum upflow velocities (VUmax) were measured. SPSS (version 14.0) was used for all statistical analysis.

Results

Patients in the scoliosis group underwent one-stage posterior vertebral column resection for deformity correction without suboccipital decompression. The mean preoperative coronal Cobb angle was 102.4° (range 76°–138°). The mean postoperative Cobb angle was 41.7° (range 12°–75°), with an average correction rate of 59.3%. During the follow-up, 1 patient with hypermyotonia experienced a significant decrease of muscle tension and 1 patient with reduced anal sphincter tone manifested recovery. A total of 5 patients demonstrated a significant decrease (> 30%) in syrinx size. With respect to changes in CSF flow dynamics, the syrinx group was characterized by slower and shorter downflow than the control group, and the difference was more significant at the foramen magnum and C-7 levels. In patients with scoliosis, CSF downflow at the foramen magnum level was significantly restricted, and a prolonged stationary phase indicated increased obstruction of CSF flow. After posterior vertebral column resection, the peak velocity of CSF flow at the foramen magnum increased, and the downflow phase duration was markedly prolonged. The parameters showed a return to almost normal CSF dynamics at the craniocervical region, and this improvement was maintained for 6–12 months of follow-up.

Conclusions

There were distinct abnormalities of CSF flow at the craniocervical junction in patients with syringomyelia. Abnormal dynamics of downflow could be aggravated by associated severe spinal deformity and improved by correction via posterior vertebral column resection.

Caracterização da qualidade de vida de adolescentes com escoliose idiopática

INTRODUÇÃO: Pacientes com escoliose possuem autoestima mais baixa, pior percepção corporal, dores na coluna vertebral; sentem-se menos saudáveis e mais infelizes que indivíduos sem deformidades na coluna. OBJETIVO: Avaliar a qualidade de vida (QV) de adolescentes com escoliose idiopática (EI) por meio do questionário autoadministrável Br-SRS-22r. MATERIAIS E MÉTODOS: Trata-se de estudo transversal. Foram selecionados por conveniência 30 pacientes com EI, média de idade de 15,5 (± 2,6) anos e curvaturas de valores médios de 28,4 (± 21,0) graus Cobb. A estatística descritiva apresentada mostra a distribuição de frequências dos escores dos cinco domínios do Br-SRS-22r. RESULTADOS: Analisando-se o domínio função, observa-se que 93,3% dos voluntários apresentaram escore acima de 3. Para o domínio autoimagem, nota-se maior distribuição dos pontos, sendo que 26,7% pontuaram entre 2 e 2,9. A distribuição dos escores dor e saúde mental foi semelhante, observando-se maior concentração entre 3 e 3,9 pontos (36,7 e 40%, respectivamente). No domínio satisfação com o tratamento, 78,6% dos voluntários apresentaram escore acima de 4. CONCLUSÃO: Os achados deste estudo para os domínios dor, função física e autoimagem corroboram estudos anteriores. Os resultados demonstraram que, em uma amostra de adolescentes com EI cuja maioria é tratada conservadoramente apenas por medidas fisioterapêuticas, o impacto da condição na percepção da QV foi considerado mediano, nos domínios dor, aparência e saúde mental, a fraco, no domínio função física.

Pathogenesis and biomechanics of adolescent idiopathic scoliosis (AIS)

Adolescent idiopathic scoliosis is defined as a scoliosis that starts after the age of ten and has no clear underlying disease as a reason for its development. There is, however, a disparity between the growth of the vertebral bodies anteriorly and that of the posterior elements. The vertebral bodies grow faster than the posterior elements, resulting primarily in a lordosis. The diminished dorsal growth impedes the ventrally located vertebral bodies from increasing in height, forcing them to become distorted, i.e., rotate, in order to create space for themselves. This produces a rotational lordosis. The idea of looking at it in this way dates back to Somerville in 1952. Many recent studies have confirmed this idea and have shown that the spinal canal is shorter than the anterior ligament of the vertebral bodies. In a mathematical model of the spine it was demonstrated that-although the vertebral column in humans is still predominantly loaded in an axial direction-certain segments of the human spine (especially the backward inclined segments) are subject to dorsally directed shear loads as well. In addition to the antero-posterior difference in growth, there is also a deformation of the vertebral bodies itself in 3-D. This is probably secondary and not primary effects, but this question is still under discussion. For the treatment of scoliosis, the biomechanical principles of axial and transverse forces are used. The combination of axial and transverse loads is most beneficial for all curves. The axial forces provide most of the corrective bending moment when deformity is severe, while the transverse loads take over the correcting function when deformity is mild. The deformity angle of 53° is the break-even point for the axial and transverse loads. In more severe curves transverse forces become less and less efficient, while axial forces rapidly gain more and more effect.

Idiopathic scoliosis: etiological concepts and hypotheses

Scoliosis is diagnosed as idiopathic in 70 % of structural deformities affecting the spine in children and adolescents, probably reflecting our current misunderstanding of this disease. By definition, a structural scoliosis should be the result of some primary disorder. The goal of this article is to give a comprehensive overview of the currently proposed etiological concepts in idiopathic scoliosis regarding genetics, molecular biology, biomechanics, and neurology, with particular emphasis on adolescent idiopathic scoliosis (AIS). Despite the fact that numerous potential etiologies for idiopathic scoliosis have been formulated, the primary etiology of AIS remains unknown. Beyond etiology, identification of prognostic factors of AIS progression would probably be more relevant in our daily practice, with the hope of reducing repetitive exposure to radiation, unnecessary brace treatments, psychological implications, and costs-of-care related to follow-up in low-risk patients.

Asynchronous neuro-osseous growth in adolescent idiopathic scoliosis--MRI-based research

Adolescent idiopathic scoliosis (AIS) is a common worldwide problem and has been treated for many decades; however, there still remain uncertain areas about this disorder. Its involvement and impact on different parts of the human body remain underestimated due to lack of technology in imaging for objective assessment in the past. The advances in imaging technique and image analysis technology have provided a novel approach for the understanding of the phenotypic presentation of neuro-osseous changes in AIS patients as compared with normal controls. This review is the summary of morphological assessment of the skeletal and nervous systems in girls with AIS based on MRI. Girls with AIS are found to have morphological differences in multiple areas including the vertebral column, spinal cord, skull and brain when compared with age- and sex-matched normal controls. Taken together, the abnormalities in the skeletal system and nervous system of AIS are likely to be inter-related and reflect a systemic process of asynchronous neuro-osseous growth. The current knowledge about the anatomical changes in AIS has important implications with respect to the understanding of fundamental pathomechanical processes involved in the evolution of the scoliotic deformity.

A new method for measuring torsional deformity in scoliosis

Background

The importance of spinal rotational and torsional deformity in the etiology and the management of scoliosis are well-recognized. For measuring the posterior spinal component rotation, Ho's method was reported to be reliable. However, there is no practical method to measure the anterior spinal component rotation. Moreover, there is also no method to quantify the spinal torsional deformity in scoliosis. The goal of this study is to characterize scoliosis and its deformity to hypothesize the etiology and the development of scoliosis, and to establish a new method for the measurement of the vertebral body rotation and spinal torsional deformity in scoliosis using CT scans.

Methods

Pre-operative CT scans of 25 non-congenital scoliosis patients were recruited and the apical vertebral rotation was measured by a newly developed method and Ho's method. Ho's method adopts the laminae as the rotational landmark. For a new method to measure the apical vertebral rotation, the posterior point just beneath each pedicle was used as a landmark. For quantifying the spinal torsional deformity angle, the rotational angle difference between the two methods was calculated.

Results

Intraobserver and interobserver reliability analyses showed both methods to be reliable. Apical vertebral rotation revealed 13.9 ± 6.8 (mean ± standard deviation) degrees by the new method and 7.9 ± 6.3 by Ho's method. Right spinal rotation was assigned a positive value. The discrepancy of rotation (6.1 ± 3.9 degrees), meaning that the anterior component rotated more than the posterior component, was considered to express the spinal torsional deformity to the convex side.

Conclusions

We have developed an easy, reliable and practical method to measure the rotation of the spinal anterior component using a CT scan. Furthermore, we quantified the spinal torsional deformity to the convex side in scoliosis by comparing the rotation between the anterior and posterior components.

Changes in level of the conus after corrective surgery for scoliosis: MRI-based preliminary study in 31 patients

BACKGROUND

Detection of postoperative spinal cord level change can provide basic information about the spinal cord status, and electrophysiological studies regarding this point should be conducted in the future.

METHODS

To determine the changes in the spinal cord level postoperatively and the possible associated factors, we prospectively studied 31 patients with scoliosis. All the patients underwent correction and posterior fusion using pedicle screws and rods between January 2008 and March 2009. The pre- and postoperative conus medullaris levels were determined by matching the axial magnetic resonance image to the sagittal scout image. The patients were divided according to the change in the postoperative conus medullaris level. The change group was defined as the patients who showed a change of more than one divided section in the vertebral column postoperatively, and the parameters of the change and non-change groups were compared.

RESULTS

The mean pre- and postoperative Cobb's angle of the coronal curve was 76.80° ± 17.19° and 33.23° ± 14.39°, respectively. Eleven of 31 patients showed a lower conus medullaris level postoperatively. There were no differences in the pre- and postoperative magnitude of the coronal curve, lordosis and kyphosis between the groups. However, the postoperative degrees of correction of the coronal curve and lumbar lordosis were higher in the change group. There were also differences in the disease entities between the groups. A higher percentage of patients with Duchenne muscular dystrophy had a change in level compared to that of the patients with cerebral palsy (83.3% vs. 45.5%, respectively).

CONCLUSIONS

The conus medullaris level changed postoperatively in the patients with severe scoliosis. Overall, the postoperative degree of correction of the coronal curve was higher in the change group than that in the non-change group. The degrees of correction of the coronal curve and lumbar lordosis were related to the spinal cord level change after scoliosis correction.

Characterization of a novel bidirectional distraction spinal cord injury animal model

Scoliosis corrective surgery requires the application of significant multidirectional stress forces, including distraction, for correction of the curved spine deformity and the application of fixation rods. If excessive, spine distraction may result in the development of new neurological deficits, some as severe as permanent paralysis. Current animal models of spinal cord injury, however, are limited to contusion, transection, or unidirectional distraction injuries, which fail to replicate the multidirectional forces that occur during spine corrective surgery. To address such limitation, we designed a novel device that relies on intervertebral grip fixation and linear actuators to induce controllable bidirectional distraction injuries to the spine. The device was tested in three (i.e., 3, 5, and 7 mm) distention paradigms of the rat T9-T11 vertebra, and the resulting injuries were evaluated through electrophysiological, behavioral, and histological analysis. As expected, 3mm bilateral spine distractions showed no neurological deficit. In contrast, those with 5 and 7 mm showed partial and complete paralysis, respectively. The relationship between the severity of the spine distraction and injury to the spinal cord tissue was determined using glial fibrillary acidic protein immunocytochemistry for visualization of reactive astrocytes and labeling of ED1-positive activated macrophages/microglia. Our results demonstrate that this device can produce bidirectional spine distraction injuries with high precision and control and, thus, may be valuable in contributing to the testing of neuroprotective strategies aimed at preventing unintended new neurological damage during corrective spine surgery.

A novel pedicle channel classification describing osseous anatomy: how many thoracic scoliotic pedicles have cancellous channels?

STUDY DESIGN

Prospective clinical series.

OBJECTIVE

To determine how many thoracic scoliotic pedicles have cancellous versus cortical versus absent channels.

SUMMARY OF BACKGROUND DATA

Although morphologic evaluations of thoracic pedicles have been well reported, the results do not practically reflect clinical findings during actual pedicle screw placement. We propose a novel pedicle channel classification describing the osseous anatomy encountered during pedicle probe insertion.

METHODS

We noted 4 pedicle types in 53 consecutive scoliosis patients. Type A: pedicle probe smoothly inserted without difficulty; the morphology is described as a "Large Cancellous Channel." Type B: pedicle probe inserted snugly with increased force; described as a "Small Cancellous Channel." Type C: pedicle probe cannot be manually pushed but must be tapped with a mallet down the pedicle into the body; described as a "Cortical Channel." Type D: pedicle probe cannot locate a channel thus necessitating a "juxtapedicular" screw position; described as a "Slit/Absent Channel." The average age at time of surgery was 23.4 ± 16.7 years. Diagnoses included idiopathic scoliosis (n = 38) and syndromic scoliosis (n = 15). The average main thoracic Cobb angle was 73° ± 26°. Evaluation of pedicle morphology of the 4 types was also performed in 21 consecutive cases of adolescent idiopathic scoliosis using preoperative computed tomography images.

RESULTS

A total of 1021 pedicles with screws placed were evaluated. The average percent per type was as follows: 61.0% type A; 29.2% type B, 6.8% type C, and 3.0% type D. On the convexity, 98.2% of pedicles were type A or B versus 81.5% on the concavity (P < 0.05). There were significant differences between adolescent versus adult idiopathic scoliosis (P = 0.007), and syndromic scoliosis versus adult idiopathic scoliosis (P = 0.017) regarding pedicle morphologic proportions. There was a significant tendency toward a decrease in the proportion of type A pedicles, an increase in the proportion of type B pedicles as the Cobb angle increased (P < 0.0001). Evaluation based on 312 thoracic pedicles in 21 consecutive adolescent idiopathic scoliosis patients using preoperative computed tomography axial images confirmed assumptions of the 4 pedicle types.

CONCLUSION

We propose a classification for pedicle channels describing the osseous anatomy encountered during pedicle probe insertion. Based on the classification, surprisingly, we found during surgery that 90% of thoracic pedicles had a cancellous channel, whereas 7% had a cortical channel and only 3% had an absent channel.

Uncoupled neuro-osseous growth in adolescent idiopathic scoliosis? A preliminary study of 90 adolescents with whole-spine three-dimensional magnetic resonance imaging

Previous literatures revealed abnormal cross-sectional morphology of spinal cord in AIS, suggesting the presence of disproportional growth between the neural and skeletal system. No accurate measurement of whole spine by MRI multiplanar reconstruction and their correlation with Cobb angle were studied. In this study, MRI three-dimensional reconstruction of the whole spine was performed in 90 adolescents (49 AIS with thoracic/thoracolumbar curve, and 41 age-matched healthy controls). Measurements of the ratio of anteroposterior (AP) and transverse (TS) diameter of the cord, the concave and convex lateral cord space (LCS) were obtained at the apical level in AIS patients. Cerebellar tonsillar level related to the basion-opsithion line, location of conus medullaris, cord length, vertebral column length, cord/vertebral column length ratio were obtained. All of the same parameters were also measured in healthy controls at matched vertebral levels and their correlations with Cobb angle were made. We notice that AP, TS, AP/TS and LCS ratio were increased in AIS subjects with low-lying position of cerebellar tonsillar level and elevating position of conus medullary when compared with healthy controls (P < 0.01). AP, AP/TS and LCS ratio were correlated significantly with Cobb angle (P < 0.05). Cord length and vertebral column length were not significantly different between AIS and control group. However, cord/vertebral column length ratio was significantly smaller in AIS group (P < 0.01). Cord length, vertebral column length and cord/vertebral column length ratio were not related with age or Cobb angle (P > 0.05). These data suggest the presence of uncoupled neuro-osseous growth along the longitudinal axis of spinal cord with associated morphologic changes of cross-sectional configuration and relative position of the cord. Some changes are significantly relevant with Cobb angle, which may indicate pathogenesis of AIS.

Analysis of idiopathic scoliosis progression by using numerical simulation

STUDY DESIGN

The mechanisms of idiopathic scoliosis progression were investigated through a patient-specific numerical model.

OBJECTIVE

To explore the combined effect of gravity, the decrease of intervertebral discs' stiffness and the anterior spinal growth on scoliosis progression, by using a numerical simulation, to better understand mechanisms of scoliosis progression.

SUMMARY OF BACKGROUND DATA

Eighteen adolescents (12 girls, 6 boys) with an average age of 10.5 years (range, 7-13) were divided into 2 groups: 12 mild scoliotic patients with thoracolumbar curves and 6 asymptomatic subjects.

METHODS

Accurate 3-dimensional reconstructions of the spine were performed from biplanar radiographs. A patient-specific validated finite element model was used. Four configurations were simulated for each patient: the first configuration with the spine under gravity, the second one under gravity with a decrease of disc's mechanical stiffness, the third one under gravity with anterior vertebral growth, and the last one with combination of the 3 previous configurations.

RESULTS

Gravity loads resulted mainly in a vertebral lateral deviation of the curve without axial rotation for all patients with mild scoliosis. Anterior vertebral growth with gravity induced both lateral deviation and axial rotation. This phenomenon was amplified when the mechanical properties of discs were decreased. None of these simulations initiated a scoliosis-like deformity for asymptomatic subjects.

CONCLUSION

For preexisting spinal curvature, an anterior spinal growth combined with gravity and a decrease of disc's mechanical stiffness could lead to a progression of scoliosis. Biomechanical factors could be secondary after initial deformation.

Dural ectasia in adolescent idiopathic scoliosis: quantitative assessment on magnetic resonance imaging

To our knowledge, the assessment of dural sac diameters in patients with adolescent idiopathic scoliosis (AIS) is not reported in the literature. The aim of this study was to find out if, dural ectasia occurs more frequently among patients with AIS, to define cut-off values for dural sac ratio and test the validity of such values. A total of 126 spine MRIs (79 patients with AIS and 47 control subjects) were included in this retrospective analysis (age range 7-25 years, 62% were females). Dural sac diameter (DSD) and vertebral body diameter (VBD) were estimated and dural sac ratio (DSR = DSD/VBD) was calculated at T5 and L3. DSR at T5 and L3 were 0.69 +/- 0.12, and 0.52 +/- 0.10, respectively, in patients with AIS compared with 0.62 +/- 0.11, and 0.44 +/- 0.07, respectively, in controls (P = 0.001 at T5 and <0.001 at L3). Our estimated cut-off values for DSR were 0.84 and 0.58 at T5 and L3, respectively. This resulted in 100% sensitivity compared with 74% when using the cut-off values proposed by Oosterhof et al. No statistically significant association was found between the occurrence of dural sac enlargement in patients with AIS and the severity of scoliotic deformity, the apical vertebral rotation, epidural fat thickness, occurrence of pain, neurological deficit, atypical scoliosis or rapid curve progression. Females were affected more frequently than males. As dural sac enlargement means thinning of the pedicles, we believe that the findings of this study have important clinical implications on the preoperative workup of AIS.

Aetiology of idiopathic scoliosis: current concepts

The aetiology of the three-dimensional spinal deformity of idiopathic scoliosis (IS) is unknown. Progressive adolescent idiopathic scoliosis (AIS) that mainly affects girls is generally attributed to relative anterior spinal overgrowth from a mechanical mechanism (torsion) during the adolescent growth spurt. Established biological risk factors to AIS are growth velocity and potential residual spinal growth assessed by maturity indicators. Spine slenderness and ectomorphy in girls are thought to be risk factors for AIS. Claimed biomechanical susceptibilities are (1) a fixed lordotic area and hypokyphosis and (2) concave periapical rib overgrowth. MRI has revealed neuroanatomical abnormalities in approximately 20% of younger children with IS. A neuromuscular cause for AIS is probable but not established. Possible susceptibilities to AIS in tissues relate to muscles, ligaments, discs, skeletal proportions and asymmetries, the latter also affecting soft tissues (e.g. dermatoglyphics). AIS is generally considered to be multi-factorial in origin. The many anomalies detected, particularly left-right asymmetries, have led to spatiotemporal aetiologic concepts involving chronomics and the genome altered by nurture without the necessity for a disease process. Genetic susceptibilities defined in twins are being evaluated in family studies; polymorphisms in the oestrogen receptor gene are associated with curve severity. A neurodevelopmental concept is outlined for the aetiology of progressive AIS. This concept involves lipid peroxidation and, if substantiated, has initial therapeutic potential by dietary anti-oxidants. Growth saltations have not been evaluated in IS.

The pathogenesis of adolescent idiopathic scoliosis: review of the literature

STUDY DESIGN

Review of the literature on the pathogenesis of adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To discuss the different theories that have appeared on this subject.

SUMMARY OF BACKGROUND DATA

The pathogenesis of AIS, a condition exclusive to humans, has been the subject of many studies. Over the years, practically every structure of the body has been mentioned in the pathogenesis of AIS; however, the cause of this spinal deformity remains little understood. The pathogenesis of this condition is termed multifactorial.

METHODS

PubMed and Google Scholar electronic databases were searched focused on parameters concerning the pathogenesis of adolescent idiopathic scoliosis. The search was limited to the English language.

RESULTS

No single causative factor for the development of idiopathic scoliosis has been identified, it is thus termed multifactorial. AIS is a complex genetic disorder. The fully erect posture, which is unique to humans, seems to be a prerequisite for the development of AIS.

CONCLUSION

Although any or all of the mentioned factors in this review may play a certain role in the initiation and progression of AIS at a certain stage, the presented material suggests that in the observed deformation, genetics, and the unique mechanics of the fully upright human spine play a decisive role.

Do adolescents with a severe idiopathic scoliosis have higher locations of the conus medullaris than healthy adolescents?

BACKGROUND

Based on the "uncoupled neuro-osseous growth" theory, the hypothesized etiology of adolescent idiopathic scoliosis (AIS), a shorter spinal cord or a higher conus location, could be found in AIS patients. However, there are no case-control studies with large samples regarding the conus position in AIS patients. This study is performed to determine the positions of the conus medullaris in AIS patients with a large curve magnitude when compared with healthy adolescents and to investigate the relationships of the conus locations with patients' age, sex, curve magnitude, and curve pattern.

METHODS

Two hundred forty AIS patients with a Cobb angle greater than 40 degree were included in this study, and 120 age-matched healthy adolescents were recruited to serve as controls. Both AIS patients and healthy controls displayed normal on neurological examinations. On sagittal magnetic resonance images of the spine in both groups, the position on the conus medullaris relative to lumbar vertebrae and intervertebral disk space was measured according to a standard method.

RESULTS

There was no significant difference in the distributions of the positions of the conus medullaris in AIS patients and healthy controls (P = 0.448). In both groups, the mean position of the conus medullaris was located at the same level, which was the lower 1/3 of L1 (range: the middle third of T12 to L2-3 disk space). The conus positions were neither significantly different among adolescents of different ages (P = 0.662 in AIS and P = 0.897 in controls) nor between boys and girls (P = 0.875 in AIS and P = 0.675 in controls). It was shown that the conus position was not significantly different among AIS patients with different curve severity (F = 0.314, P = 0.731) and curve patterns (F = 0.097, P = 0.756).

CONCLUSIONS

The mean and the distribution of the conus locations were similar for AIS patients and the controls. No significant associations of the conus position with curve severity and with curve patterns were found, indicating that the conus location might not be involved in the pathogenesis and curve progression of AIS.

LEVEL OF EVIDENCE

Level III.

Relative shortening and functional tethering of spinal cord in adolescent scoliosis - Result of asynchronous neuro-osseous growth, summary of an electronic focus group debate of the IBSE

There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The Statement for this debate was written by Dr WCW Chu and colleagues who examine the spinal cord to vertebral growth interaction during adolescence in scoliosis. Using the multi-planar reconstruction technique of magnetic resonance imaging they investigated the relative length of spinal cord to vertebral column including ratios in 28 girls with AIS (mainly thoracic or double major curves) and 14 age-matched normal girls. Also evaluated were cerebellar tonsillar position, somatosensory evoked potentials (SSEPs), and clinical neurological examination. In severe AIS compared with normal controls, the vertebral column is significantly longer without detectable spinal cord lengthening. They speculate that anterior spinal column overgrowth relative to a normal length spinal cord exerts a stretching tethering force between the two ends, cranially and caudally leading to the initiation and progression of thoracic AIS. They support and develop the Roth-Porter concept of uncoupled neuro-osseous growth in the pathogenesis of AIS which now they prefer to term 'asynchronous neuro-osseous growth'. Morphological evidence about the curve apex suggests that the spinal cord is also affected, and a 'double pathology' is suggested. AIS is viewed as a disorder with a wide spectrum and a common neuroanatomical abnormality namely, a spinal cord of normal length but short relative to an abnormally lengthened anterior vertebral column. Neuroanatomical changes and/or abnormal neural function may be expressed only in severe cases. This asynchronous neuro-osseous growth concept is regarded as one component of a larger concept. The other component relates to the brain and cranium of AIS subjects because abnormalities have been found in brain (infratentorial and supratentorial) and skull (vault and base). The possible relevance of systemic melatonin-signaling pathway dysfunction, platelet calmodulin levels and putative vertebral vascular biology to the asynchronous neuro-osseous growth concept is discussed. A biomechanical model to test the spinal component of the concept is in hand. There is no published research on the biomechanical properties of the spinal cord for scoliosis specimens. Such research on normal spinal cords includes movements (kinematics), stress-strain responses to uniaxial loading, and anterior forces created by the stretched cord in forward flexion that may alter sagittal spinal shape during adolescent growth. The asynchronous neuro-osseous growth concept for the spine evokes controversy. Dr Chu and colleagues respond to five other concepts of pathogenesis for AIS and suggest that relative anterior spinal overgrowth and biomechanical growth modulation may also contribute to AIS pathogenesis.

[Selective dorsal T1-T6 fusion of the thoracic spine and effects on thorax growth: experimental study in prepuberal New Zealand White rabbits]

PURPOSE OF THE STUDY

The purpose of this study is to assess the consequences brought by selective dorsal arthrodesis of thoracic spine (T1-T6) to the growth of spine and thoracic volume in operated and sham-operated New Zealand White rabbits, between prepubertal age and the end of somatic growth, through the study of computerised tomography (CT) scans periodically carried out on them after arthrodesis surgery.

MATERIAL AND METHODS

Nine female rabbits were subjected to surgery for selective dorsal arthrodesis of the upper thoracic spine and three were sham-operated. Surgery was performed at age nine weeks, before the onset of puberty. Two "C"-shaped titanium bars were placed beside the spinous processes of the thoracic vertebrae to obtain a selective posterior arthrodesis of the first six thoracic vertebrae. Under general anesthesia, three CT scans were performed, 10 (t1), 55 (t2) and 139 (t3) days after surgery. Measures were obtained by Myrian Pro software for three different groups: group 1 with complete fusion, group 2 with incomplete fusion, group 3 sham-operated.

RESULTS

The total dorsal and ventral lengths of thoracic vertebral bodies in the spinal segment T1-T6 was smaller in group 1 and group 2 than in group 3, whereas no differences were observed between the three groups in the T7-T12 segment. The average of the dorsoventral/laterolateral thoracic diameter ratio at fused levels was less than 1 in group 1 as well as in group 2; on the contrary, in group 3 it was greater than 1. The sternum and lung volume grow less.

CONCLUSIONS

Vertebral arthrodesis in the treatment of progressive idiopathic scoliosis in prepubertal patients is not ideal, but is still a choice in treating major deformities of the spine. Postoperative assessment of spinal deformity is essential, feasible and recordable through CT scans. Dorsal arthrodesis in prepubertal rabbits changes thoracic growth patterns. In operated rabbits, the dorsoventral thoracic diameter grows more slowly than the laterolateral thoracic diameter. The sternum, the total lengths of thoracic vertebral bodies in the spinal segment T1-T6 and lungs grow less. The Crankshaft phenomenon is evident at the fused vertebral levels where there is a reduction of thoracic kyphosis.

Morphological and functional electrophysiological evidence of relative spinal cord tethering in adolescent idiopathic scoliosis

STUDY DESIGN

Magnetic resonance (MR) imaging and multiplanar reconstruction was used to evaluate the morphology and relative position of the spinal cord in adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To determine the longitudinal and cross-sectional morphology of spinal cord in AIS subjects versus normal controls and their correlation with relative position of cerebellar tonsils and somatosensory cortical evoked potentials (SSEP).

SUMMARY OF BACKGROUND DATA

Our previous studies revealed significantly reduced spinal cord to vertebral column length ratios in AIS patients with severe scoliotic curves suggesting the presence of disproportional growth between the neural and skeletal system. A possible neural origin of etiopathogenesis of AIS is suggested.

METHODS

MR multiplanar reconstruction was performed in 97 adolescent girls (35 moderate, 26 severe AIS with right-sided thoracic/thoracolumbar curve, and 36 age-matched controls). Measurements of the ratio of anteroposterior (AP) and transverse (TS) diameter of the cord, the concave and convex lateral cord space (LCS) were obtained at the apical level in AIS subjects. Same parameters were obtained in normal controls at matched vertebral levels. Correlations were made with cord to vertebral column length ratio, cerebellar tonsil position and SSEP findings.

RESULTS

AP/TS cord ratio and LCS ratio were increased in AIS subjects in the presence of reduced spinal cord to vertebral length ratio when compared with normal controls (P < 0.05). The above ratios were exaggerated in AIS subjects with abnormal SSEP findings. The AP/TS cord ratio and LCS ratio were negatively correlated with the cord to vertebral column length ratio (rho = -0.410 and -0.313, P < 0.01) and cerebellar tonsillar level (rho = -0.309 and -0.432, P < 0.01).

CONCLUSION

Our study suggests presence of tethering and increased tension along the longitudinal axis of spinal cord with associated morphologic changes of cross-sectional shape and relative position of the cord.