Pathogenesis of Adolescent Idiopathic Scoliosis

The benefits of touched vertebra concept for the selection of the lowest instrumented vertebra in thoracic curves of adolescent idiopathic scoliosis

PURPOSE

To assess the benefits of using the touched vertebra (TV) rule in Lenke classification for thoracic curves of adolescent idiopathic scoliosis (AIS).

METHODS

A total of 141 AIS patients with thoracic curves determined by Suk classification were divided based on whether the lowest instrumented vertebra (LIV) matched the TV into groups of mTV (n = 84, LIV = TV), TV- (n = 21, LIV above TV), and TV+ (n = 36, LIV below TV) for 5-year follow-up. The radiological parameters were the central sacral vertical line (CSVL)-LIV distance, distal end vertebra rotation, coronal, and sagittal parameters. Complications included adding-on phenomenon, coronal imbalance, and distal junctional kyphosis.

RESULTS

Adding-on phenomenon and coronal imbalance were significantly higher in the TV- group (P = 0.006) and TV + group (P = 0.006), respectively. The distal motion segments were significantly saved in the mTV group (P < 0.001). The CSVL-LIV distance was significantly improved in the mTV group compared to the others during the 5-year follow-up (P = 0.007). The 5-year follow-up CSVL-LIV distance correlated with LIV tilt angle (r = 0.442, P = 0.021) and coronal balance (r = 0.437, P = 0.023).

CONCLUSIONS

Selecting the TV as LIV minimizes the loss of the distal mobile segment and reduces the complications in the thoracic curves of AIS, which produces a more stable LIV on the CSVL. Therefore, TV is an ideal landmark for determining the distal fusion level using the Lenke classification or Suk classification.

The significance of cerebrospinal fluid dynamics in adolescent idiopathic scoliosis using time-SLIP MRI

Adolescent idiopathic scoliosis (AIS) affects approximately 3% of the global population. Recent studies have drawn attention to abnormalities in the dynamics of the CSF as potential contributors. This research aims to employ the Time-Spatial Labeling Inversion Pulse (Time-SLIP) MRI to assess and analyze cerebrospinal fluid (CSF) dynamics in AIS patients. 101 AIS patients underwent Time-SLIP MRI. Images were taken at the mid-cervical and craniocervical junction regions. The sum of the maximum movement distances of CSF on the ventral and dorsal sides of the spinal canal within a single timeframe was defined and measured as Travel Distance (TD). Correlations between TD, age, Cobb angle, and Risser grade were analyzed. TD comparisons were made across Lenke classifications. TD for all patients was a weak correlation with the Cobb angle (r = - 0.16). Comparing TD between Lenke type 1 and 5, type 5 patients display significantly shorter TD (p < 0.05). In Risser5 patients with Lenke type 5 showed a significant negative correlation between Cobb angle and TD (r = - 0.44). Lenke type 5 patients had significantly shorter CSF TD compared to type1, correlating with worsening Cobb angles. Further analysis and exploration are required to understand the mechanism of onset and progression.

Frequency of Coexistent Spinal Segment Variants: Retrospective Analysis in Asymptomatic Young Adults

BACKGROUND AND PURPOSE

Spinal segment variants are highly prevalent and can potentially lead to incorrect spinal enumeration and, consequently, interventions or surgeries at the wrong vertebral levels. Our aim was to assess the prevalence of spinal segment variants and to study the potential association among these variants in a population without histories of spine symptoms.

MATERIALS AND METHODS

Consecutive computed tomography exams of 450 young adults originally evaluated for non-spinal conditions and without a history of spinal diseases from a single institution. In addition to using descriptive statistics for reporting frequencies of spinal segment variants, the association between these variants was studied by calculating odds ratios and their 95% confidence interval. Consecutive CT exams were evaluated to determine the total number of presacral segments, presence of cervical rib, thoracolumbar transitional vertebra, iliolumbar ligament, and lumbosacral transitional vertebra.

RESULTS

The spinal segment distribution variants (an atypical number of presacral segments or an atypical distribution of thoracolumbar vertebrae), cervical rib, thoracolumbar transitional vertebra, and lumbosacral transitional vertebra were reported in 23.8%, 4.2%, 15.3%, and 26.4% of cases in our study population. The presence of a cervical rib or a thoracolumbar transitional vertebra was associated with concurrent lumbosacral transitional vertebra (OR = 3.28; 95% CI, 1.29-8.47 and 1.87; 95% CI, 1.08-3.20, respectively). The inability to visualize the iliolumbar ligament was also associated with the presence of cervical ribs (OR = 3.06; 95% CI, 1.18-7.80).

CONCLUSIONS

In a population of asymptomatic young adults, spinal segment variants are both highly prevalent with a high rate of coexistence. When a spinal segment variant (eg, transitional vertebra) is diagnosed, additional imaging might be considered for accurate spine enumeration before interventions or operations.

Elasticity change of the paravertebral fascia and muscle in adolescent idiopathic scoliosis after posterior selective fusion surgery

BACKGROUND

We sought to assess the elasticity change of the paravertebral fascia and muscle in adolescent idiopathic scoliosis patients with Lenke Type 1, 2, or 3 curves after posterior selective fusion surgery.

METHODS

The shear wave elasticity imaging system was used to assess the elasticity of the thoracic paravertebral muscles and fascia both on the concave and convex sides. Three regions of interest, including the apex, upper end, and lower end of the main curve, were tested.

FINDINGS

Ten female patients, with an average age of 16.6 ± 2.7 years old, were included. The average post-operation follow-up period was 9.0 ± 2.4 months. The Cobb angle was significantly corrected from 63.6 ± 12.0° to 10.7 ± 5.4° (p < 0.05). The length of the trunk increased from 40.4 ± 2.5 cm to 46.0 ± 2.8 cm (p < 0.05). The elasticity of deep fascia didn't show a significant change post-operation (p > 0.05). The elasticity of the paravertebral muscle on the concave side had a significant increase at the final follow-up (p < 0.05). The elasticity of the paravertebral muscle on the convex side also increased at the upper end (p < 0.05). The elasticity asymmetry of the deep fascia decreased, but the elasticity asymmetry of the paravertebral muscle increased at the upper end of the curve (p < 0.05).

INTERPRETATION

The paravertebral muscle on the concave side is stiffer after surgery. Elastic asymmetry of paravertebral muscle increased and elastic asymmetry of the deep fascia decreased at the upper end of the curvature. Further study is needed to elucidate the mechanism by which the paravertebral soft tissue responds after surgery.

Pedicle Screw Plowing in Adolescent Idiopathic Scoliosis: How Common Is It and Is It a Problem?

STUDY DESIGN

Multicenter retrospective review.

OBJECTIVE

To calculate overall incidence of pedicle screw "plowing" in adolescent idiopathic scoliosis (AIS) patients who underwent posterior spinal fusion (PSF). To identify risk factors for pedicle screw plowing and associated postoperative outcomes, including loss of correction and revision rate.

SUMMARY OF BACKGROUND DATA

Curve correction of AIS generates perpendicular stresses that can cause pedicle screws to lose alignment and "plow" through pedicles craniocaudally.

METHODS

We reviewed records of 1057 patients who underwent PSF for AIS from 2002 to 2015. Preoperative and first postoperative erect radiographs were evaluated by two observers to determine (1) presence of plowing and (2) subsequent loss of correction (LOC). Plowing was defined as more than 25° sagittal angulation compared with pedicle axis or entry of the most dorsal part of the screw outside the pedicle projection. LOC was defined as postoperative change in focal angulation of an instrumented spinal level, when in consensus of both reviewers. Bivariate analyses were performed (alpha = 0.05).

RESULTS

Nineteen thousand five hundred sixty nine screws were assessed across our cohort of 1057 patients. Both observers agreed that 48 patients (4.5%) demonstrated plowing of more than or equal to one pedicle screw. For 72 screws (0.4%), both observers noted plowing, most commonly through the cranial cortex of the pedicle (65/72 screws) and at the lowest instrument vertebra (LIV) (17/72 screws). Factors associated with plowing included larger curves (P = 0.02); lower mean pedicle screw density (P = 0.0003); skeletal immaturity as measured by open triradiate cartilage (P = 0.04); and younger chronological age at time of surgery (P = 0.04). LOC occurred in 13 patients, most commonly at LIV (P < 0.0001). Revision rate for loss of screw fixation was higher in the plowing group (P = 0.003).

CONCLUSION

Pedicle screw plowing occurred in 4.5% of AIS patients, especially in those skeletally immature and with decreased implant density. Plowing commonly occurred in the cranial direction and was associated with LOC, particularly at the LIV.Level of Evidence: 3.

Scoliosis Management for Primary Care Practitioners

For many families, the possibility that their child may have scoliosis causes great anxiety because their child may be deformed for life, may need to wear a brace for years, or may need to undergo a large and dangerous operation. For most families, these fears are groundless. Up to 3% of the population has a spinal curvature, most of which are small curves that may not need referral or repeated imaging. Many adolescents with scoliosis do well and do not need to wear a brace or have surgery.

Bibliometric Analysis of the Scientific Literature on Adolescent Idiopathic Scoliosis

BACKGROUND

In recent years, there has been increasing research on adolescent idiopathic scoliosis (AIS), leading to many publications on this topic. To our knowledge, no study has focused on the research trends in this field.

METHODS

Using the Web of Science Core Collection database for all articles on AIS, the number of citations, authorship, year of publication, journal of publication, country and institution of origin, and keywords were subjected to co-occurrence analysis using VOSviewer software. The top 100 most-cited articles on AIS were analyzed.

RESULTS

Between 1985 and 2020, 2266 articles related to AIS were identified. The frequency of publication on AIS has increased substantially over time. Among all countries, the United States has contributed the most articles on AIS (n = 671). The most productive institution has been Nanjing University (n = 154). Spine topped the list of journals and has published 569 AIS-related articles, which received 19,862 total citations. The clinical description of AIS has been the most common research focus in the AIS literature.

CONCLUSIONS

The scientific literature on AIS has rapidly expanded in recent years. This study represents the updated bibliometric analysis of scientific articles on AIS and provides a research trend for the first time, which aims to give a unique insight into the development of AIS research focus and serve as a useful guide to clinicians and researchers in the field.

Microstructural characterization of annulus fibrosus by ultrasonography: a feasibility study with an in vivo and in vitro approach

The main function of the intervertebral disc is biomechanical function, since it must resist repetitive high loadings, while giving the spine its flexibility and protecting the spinal cord from over-straining. It partially owes its mechanical characteristics to the lamellar architecture of its outer layer, the annulus fibrosus. Today, no non-invasive means exist to characterize annulus lamellar structure in vivo. The aim of this work was to test the feasibility of imaging annulus fibrosus microstructure in vivo with ultrasonography. Twenty-nine healthy adolescents were included. Ultrasonographies of L3-L4 disc were acquired with a frontal approach. Annulus fibrosus was segmented in the images to measure the thickness of the lamellae. To validate lamellar appearance in ultrasonographies, multimodality images of two cow tail discs were compared: ultrasonography, magnetic resonance and optical microscopy. In vivo average lamellar thickness was 229.7 ± 91.5 μm, and it correlated with patient body mass index and age. Lamellar appearance in the three imaging modalities in vitro was consistent. Lamellar measurement uncertainty was 7%, with good agreement between two operators. Feasibility of ultrasonography for the analysis of lumbar annulus fibrosus structure was confirmed. Further work should aim at validating measurement reliability, and to assess the relevance of the method to characterize annulus alterations, for instance in disc degeneration or scoliosis.

Opposite asymmetries of face and trunk and of kissing and hugging, as predicted by the axial twist hypothesis

The contralateral organization of the forebrain and the crossing of the optic nerves in the optic chiasm represent a long-standing conundrum. According to the Axial Twist Hypothesis (ATH) the rostral head and the rest of the body are twisted with respect to each other to form a left-handed half turn. This twist is the result, mainly, of asymmetric, twisted growth in the early embryo. Evolutionary selection tends to restore bilateral symmetry. Since selective pressure will decrease as the organism approaches symmetry, we expected a small control error in the form of a small, residual right-handed twist. We found that the mouth-eyes-nose (rostral head) region shows a left-offset with respect to the ears (posterior head) by up to 0.8° (P < 0.01, Bonferroni-corrected). Moreover, this systematic aurofacial asymmetry was larger in young children (on average up to 3°) and reduced with age. Finally, we predicted and found a right-sided bias for hugging (78%) and a left-sided bias for kissing (69%). Thus, all predictions were confirmed by the data. These results are all in support of the ATH, whereas the pattern of results is not (or only partly) explained by existing alternative theories. As of the present results, the ATH is the first theory for the contralateral forebrain and the optic chiasm whose predictions have been tested empirically. We conclude that humans (and all other vertebrates) are fundamentally asymmetric, both in their anatomy and their behavior. This supports the thesis that the approximate bilateral symmetry of vertebrates is a secondary feature, despite their being bilaterians.

Asymmetric biomechanical characteristics of the paravertebral muscle in adolescent idiopathic scoliosis

BACKGROUND

We sought to assess the biomechanical properties of the paravertebral muscles in adolescent idiopathic scoliosis patients with Lenke Type 1, 2, or 3 (Lenke 1-3) curves.

METHODS

The MyotonPro® and shear wave elasticity imaging system were used to assess the biomechanical features of the thoracic paravertebral muscles on concave and convex side in adolescent idiopathic scoliosis patients with Lenke 1-3 curves. The Cobb angle of the main curve was measured using the anteroposterior whole spine radiograph in the standing position.

FINDINGS

A total of 40 adolescent idiopathic scoliosis patients with a mean Cobb angle of 66.49° (SD 32.8°) were included in this study. Muscle tone, stiffness and Deborah number on the concave side was significantly greater than that on the convex side. Relaxation time was significantly longer on the convex side than on the concave side. No statistically significant difference in muscle elasticity was observed between the concave side and the convex side (P > 0.05). Pearson correlation analysis demonstrated that stiffness on the concave side was moderately positively correlated with the Cobb angle (P < 0.05, r = 0.582); the Deborah number on both sides and the relaxation time on the concave side showed a moderate negative correlation with the Cobb angle (P < 0.05, r = -0.632; r = -0.432; r = -0.611).

INTERPRETATION

Concave paravertebral muscle tone and stiffness were greater than those on convex side in adolescent idiopathic scoliosis patients. The asymmetric biomechanical characteristics of paravertebral muscles are closely related to the severity of scoliosis.

Scoliosis Secondary to Dystonia: A Case Report and Review of the Literature

CASE

An adolescent girl presented with an atypical scoliotic curve, pelvic obliquity, back pain, and lower-extremity paresthesias. A workup revealed generalized primary torsion dystonia. The condition was refractory to medical treatment and necessitated implantation of a deep brain stimulator. The scoliosis required operative correction, and the patient underwent posterior spinal arthrodesis with hook-rod instrumentation, which resulted in successful correction through 7 years of follow-up.

CONCLUSION

The differential diagnosis for adolescent scoliosis should include dystonia as a potential cause, especially when a patient presents with muscular contractures, an atypical scoliotic curve, pelvic obliquity, or changing curve characteristics.

A comparison of vertebral venous networks in adolescent idiopathic scoliosis patients and healthy controls

PURPOSE

Cadaveric studies have previously documented a typical pattern of venous drainage within vertebral bodies (VBs), comprised primarily of the basivertebral vein. These studies, however, are limited by the number of samples available. MRI is able to provide 3D images of soft tissue structures in the spine, including the basivertebral vein without the use of contrast in both healthy controls and subjects with abnormal anatomy such as adolescent idiopathic scoliosis (AIS). This study aimed to quantify the venous networks within VBs of 15 healthy adolescent controls and 15 AIS patients.

METHODS

Five transverse slices through the VBs were examined simultaneously and the observable vascular network traced. The length of the network on the left and right sides of the VB was calculated, and the spatial patterning assessed level-by-level within each subject.

RESULTS

Significant differences were seen in the left/right distribution of vessels in both the control and AIS subjects, with both groups having greater length on the right side of all of their VBs. No difference was seen between AIS and control subjects in any region. Large individual variations in patterns were seen in both groups; however, the control group showed more consistent spatial patterning of the vascular networks across levels in comparison to the AIS group.

CONCLUSION

The length of the basivertebral vein was seen to have a significant bias to the right hand side of the VB in both healthy and AIS adolescents. The spatial pattern of this vein showed large variations in branching both within and across individuals. No significant differences were seen between AIS and control subjects, suggesting both that this network is preserved in deformed AIS vertebrae, and that the vertebral venous system does not play a role in the etiology of AIS.

Qualitative and quantitative assessment of collagen and elastin in annulus fibrosus of the physiologic and scoliotic intervertebral discs

The biophysical properties of the annulus fibrosus of the intervertebral disc are determined by collagen and elastin fibres. The progression of scoliosis is accompanied by a number of pathological changes concerning these structural proteins. This is a major cause of dysfunction of the intervertebral disc. The object of the study were annulus fibrosus samples excised from intervertebral discs of healthy subjects and patients treated surgically for scoliosis in the thoracolumbar or lumbar spine. The research material was subjected to structural analysis by light microscopy and quantitative analysis of the content of collagen types I, II, III and IV as well as elastin by immunoenzymatic test (ELISA). A statistical analysis was conducted to assess the impact of the sampling site (Mann-Whitney test, α=0.05) and scoliosis (Wilcoxon matched pairs test, α=0.05) on the obtained results. The microscopic studies conducted on scoliotic annulus fibrosus showed a significant architectural distortion of collagen and elastin fibres. Quantitative biochemical assays demonstrated region-dependent distribution of only collagen types I and II in the case of healthy intervertebral discs whereas in the case of scoliotic discs region-dependent distribution concerned all examined proteins of the extracellular matrix. Comparison of scoliotic and healthy annulus fibrosus revealed a significant decrease in the content of collagen type I and elastin as well as a slight increase in the proportion of collagen types III and IV. The content of collagen type II did not differ significantly between both groups. The observed anomalies are a manifestation of degenerative changes affecting annulus fibrosus of the intervertebral disc in patients suffering from scoliosis.

The polymorphisms of melatonin receptor 1B gene (MTNR1B) (rs4753426 and rs10830963) and susceptibility to adolescent idiopathic scoliosis: a meta-analysis

OBJECTIVE

To determine whether MTNR1B rs4753426 and rs10830963 polymorphisms are correlated with AIS. Adolescent idiopathic scoliosis (AIS) is the most common form of spinal deformity, while its etiology remains uncertain. Melatonin receptor 1B (MTNR1B) gene polymorphisms have been found to be significantly associated with AIS risk; however, some of these results are controversial.

METHODS

An systematic online search was performed using PubMed, EMBASE, Web of Science and the Cochrane Library to identify case-control studies investigating the relationship between MTNR1B rs4753426 and rs10830963 polymorphisms and the susceptibility of AIS. The pooled odds ratio (OR) with 95 % confidence interval (95 % CI) was calculated to assess the associations, and subgroup meta-analyses were performed according to the ethnicity of the study populations.

RESULTS

A total of five studies involving 2395 cases and 3645 controls met the inclusion criteria after assessment by two reviewers. Overall, no significant associations were found between MTNR1B rs4753426 polymorphism and AIS risk (C vs. T: OR = 1.11, 95 % CI 0.94-1.30, P = 0.21; CC vs. TT: OR = 1.15, 95 % CI 0.97-1.36, P = 0.12; CT vs. TT: OR = 1.14, 95 % CI 0.97-1.35, P = 0.10; CC/CT vs. TT: OR = 1.14, 95 % CI 0.98-1.33, P = 0.09; CC vs.

CT/TT

OR = 1.10, 95 % CI 0.84-1.45, P = 0.48), as well as the MTNR1B rs10830963 polymorphism (G vs. C: OR = 0.99, 95 % CI 0.88-1.12, P = 0.91; GG vs. CC: OR = 0.99, 95 % CI 0.74-1.33, P = 0.96; CG vs. CC: OR = 1.00, 95 % CI 0.84-1.18, P = 0.88; GG/CG vs. CC: OR = 0.99, 95 % CI 0.84-1.17, P = 0.93; GG vs.

CG/CC

OR = 0.99, 95 % CI 0.75-1.30, P = 0.92). When stratified by ethnicity, there were no significant associations between MTNR1B rs4753426 and MTNR1B rs10830963 polymorphisms and AIS risk in either Asian or Caucasian populations.

CONCLUSION

MTNR1B rs4753426 and MTNR1B rs10830963 polymorphisms are not obviously associated with risk of AIS in either Asian populations or Caucasian populations.