Rob C. Brink

Three-dimensional characterization of torsion and asymmetry of the intervertebral discs versus vertebral bodies in adolescent idiopathic scoliosis.

Study Design. Cross-sectional study. Objective. To compare the relative contribution of the vertebral bodies and intervertebral discs with the 3-dimensional spinal deformity in adolescent idiopathic scoliosis. Summary of Background Data. There is an ongoing discussion about the causal role of skeletal growth processes in the etiopathogenesis of adolescent idiopathic scoliosis. Contradictory findings have been reported on the individual contribution of the vertebral bodies as compared with the discs to the coronal deformity. As far as we know, the true 3-dimensional deformity of the discs and vertebral bodies have not yet been described. Methods. High-resolution computed tomographic scans of 77 patients with severe adolescent idiopathic scoliosis were included. Torsion and anterior-posterior and right-left asymmetry of each individual vertebral body and intervertebral disc were studied from T2 to L5, using semiautomatic analysis software. True transverse sections were reconstructed along the anterior-posterior and right-left axis of all endplates. These “endplate-vectors” were calculated semiautomatically, taking rotation and tilt into account. Torsion was defined as the difference in axial rotation between 2 subsequent endplates. Asymmetry was defined as the relative anterior-posterior or right-left height difference of the discs and the vertebrae. Results. There were at least 3 times more torsion, anterior overgrowth, and coronal wedging in the discs than in the vertebrae in the thoracic as well as in the (thoraco) lumbar curves (P < 0.001). These values correlated significantly with the Cobb angle (r ≥ 0.37; P < 0.001). Anterior overgrowth and coronal asymmetry were greater in the apical regions whereas torsion was most pronounced in the transitional segments between the curves. Conclusion. The discs contribute more to 3-D deformity than the bony structures, and there is significant regional variability. This suggests an adaptive rather than an active phenomenon. Level of Evidence: 2

Upright, prone, and supine spinal morphology and alignment in adolescent idiopathic scoliosis

BackgroundPatients with adolescent idiopathic scoliosis (AIS) are usually investigated by serial imaging studies during the course of treatment, some imaging involves ionizing radiation, and the radiation doses are cumulative. Few studies have addressed the correlation of spinal deformity captured by these different imaging modalities, for which patient positioning are different. To the best of our knowledge, this is the first study to compare the coronal, axial, and sagittal morphology of the scoliotic spine in three different body positions (upright, prone, and supine) and between three different imaging modalities (X-ray, CT, and MRI).MethodsSixty-two AIS patients scheduled for scoliosis surgery, and having undergone standard pre-operative work-up, were included. This work-up included upright full-spine radiographs, supine bending radiographs, supine MRI, and prone CT as is the routine in one of our institutions. In all three positions, Cobb angles, thoracic kyphosis (TK), lumbar lordosis (LL), and vertebral rotation were determined. The relationship among three positions (upright X-ray, prone CT, and supine MRI) was investigated according to the Bland-Altman test, whereas the correlation was described by the intraclass correlation coefficient (ICC).ResultsThoracic and lumbar Cobb angles correlated significantly between conventional radiographs (68° ± 15° and 44° ± 17°), prone CT (54° ± 15° and 33° ± 15°), and supine MRI (57° ± 14° and 35° ± 16°; ICC ≥0.96; P < 0.001). The thoracic and lumbar apical vertebral rotation showed a good correlation among three positions (upright, 22° ± 12° and 11° ± 13°; prone, 20° ± 9° and 8° ± 11°; supine, 16° ± 11° and 6° ± 14°; ICC ≥0.82; P < 0.001). The TK and LL correlated well among three different positions (TK 26° ± 11°, 22° ± 12°, and 17° ± 10°; P ≤ 0.004; LL 49° ± 12°, 45° ± 11°, and 44° ± 12°; P < 0.006; ICC 0.87 and 0.85).ConclusionsAlthough there is a generalized underestimation of morphological parameters of the scoliotic deformity in the supine and prone positions as compared to the upright position, a significant correlation of these parameters is still evident among different body positions by different imaging modalities. Findings of this study suggest that severity of scoliotic deformity in AIS patients can be largely represented by different imaging modalities despite the difference in body positioning.

Anterior Spinal Overgrowth Is the Result of the Scoliotic Mechanism and Is Located in the Disc

Study Design. Cross-sectional study. Objective. To investigate the presence and magnitude of anterior spinal overgrowth in neuromuscular scoliosis and compare this with the same measurements in idiopathic scoliosis and healthy spines. Summary of Background Data. Anterior spinal overgrowth has been described as a potential driver for the onset and progression of adolescent idiopathic scoliosis (AIS). Whether this anterior overgrowth is specific for AIS or also present in nonidiopathic scoliosis has not been reported. Methods. Supine computed tomography (CT) scans of thirty AIS patients (thoracic Cobb 21–81°), thirty neuromuscular (NM) scoliotic patients (thoracic Cobb 19–101°) and 30 nonscoliotic controls were used. The difference in length in per cents between the anterior and posterior side {[(&Dgr;A-P)/P]*100%, abbreviated to A-P%} of each vertebral body and intervertebral disc, and between the anterior side of the spine and the spinal canal (A-C%) were determined. Results. The A-P% of the thoracic curves did not differ between the AIS (+1.2 ± 2.2%) and NM patients (+0.9 ± 4.1%, P = 0.663), both did differ, however, from the same measurements in controls (–3.0 ± 1.6%; P < 0.001) and correlated linearly with the Cobb angle (AIS r = 0.678, NM r = 0.687). Additional anterior length was caused by anterior elongation of the discs (AIS: A-P% disc +17.5 ± 12.7% vs. A-P% body –2.5 ± 2.6%; P < 0.001, NM: A-P% disc +19.1 ± 18.0% vs. A-P% body –3.5 ± 5.1%; P < 0.001). The A-C% T1-S1 in AIS and NM patients were similar (+7.9 ± 1.8% and +8.7 ± 4.0%, P = 0.273), but differed from the controls (+4.2 ± 3.3%; P < 0.001). Conclusion. So called anterior overgrowth has been postulated as a possible cause for idiopathic scoliosis, but apparently it occurs in scoliosis with a known origin as well. This suggests that it is part of a more generalized scoliotic mechanism, rather than its cause. The fact that the intervertebral discs contribute more to this increased anterior length than the vertebral bodies suggests an adaptation to altered loading, rather than a primary growth disturbance. Level of Evidence: 4

Asymmetry of the Vertebral Body and Pedicles in the True Transverse Plane in Adolescent Idiopathic Scoliosis: A CT-Based Study.

STUDY DESIGN Cross-sectional. OBJECTIVES To quantify the asymmetry of the vertebral bodies and pedicles in the true transverse plane in adolescent idiopathic scoliosis (AIS) and to compare this with normal anatomy. SUMMARY OF BACKGROUND DATA There is an ongoing debate about the existence and magnitude of the vertebral body and pedicle asymmetry in AIS and whether this is an expression of a primary growth disturbance, or secondary to asymmetrical loading. METHODS Vertebral body asymmetry, defined as left-right overlap of the vertebral endplates (ie, 100%: perfect symmetry, 0%: complete asymmetry) was evaluated in the true transverse plane on CT scans of 77 AIS patients and 32 non-scoliotic controls. Additionally, the pedicle width, length, and angle and the length of the ideal screw trajectory were calculated. RESULTS Scoliotic vertebrae were on average more asymmetric than controls (thoracic: AIS 96.0% vs. controls 96.4%; p = .005, lumbar: 95.8% vs. 97.2%; p < .001) and more pronounced around the thoracic apex (95.8%) than at the end vertebrae (96.3%; p = .031). In the thoracic apex; the concave pedicle was thinner (4.5 vs. 5.4 mm; p < .001) and longer (20.9 vs. 17.9 mm; p < .001), the length of the ideal screw trajectory was longer (43.0 vs. 37.3 mm; p < .001), and the transverse pedicle angle was greater (12.3° vs. 5.7°; p < .001) than the convex one. The axial rotation showed no clear correlation with the asymmetry. CONCLUSIONS Even in non-scoliotic controls is a degree of vertebral body and pedicle asymmetry, but scoliotic vertebrae showed slightly more asymmetry, mostly around the thoracic apex. In contrast to the existing literature, there is no major asymmetry in the true transverse plane in AIS and no uniform relation between the axial rotation and vertebral asymmetry could be observed in these moderate to severe patients, suggesting that asymmetrical vertebral growth does not initiate rotation, but rather follows it as a secondary phenomenon. LEVEL OF EVIDENCE Level 4.STUDY DESIGN Cross-sectional. OBJECTIVES To quantify the asymmetry of the vertebral bodies and pedicles in the true transverse plane in adolescent idiopathic scoliosis (AIS) and to compare this with normal anatomy. There is an ongoing debate about the existence and magnitude of the vertebral body and pedicle asymmetry in AIS and whether this is an expression of a primary growth disturbance, or secondary to asymmetrical loading. METHODS Vertebral body asymmetry, defined as left-right overlap of the vertebral endplates (ie, 100%: perfect symmetry, 0%: complete asymmetry) was evaluated in the true transverse plane on CT scans of 77 AIS patients and 32 non-scoliotic controls. Additionally, the pedicle width, length, and angle and the length of the ideal screw trajectory were calculated. RESULTS Scoliotic vertebrae were on average more asymmetric than controls (thoracic: AIS 96.0% vs. controls 96.4%; p =.005, lumbar: 95.8% vs. 97.2%; p <.001) and more pronounced around the thoracic apex (95.8%) than at the end vertebrae (96.3%; p =.031). In the thoracic apex; the concave pedicle was thinner (4.5 vs. 5.4 mm; p <.001) and longer (20.9 vs. 17.9 mm; p <.001), the length of the ideal screw trajectory was longer (43.0 vs. 37.3 mm; p <.001), and the transverse pedicle angle was greater (12.3° vs. 5.7°; p <.001) than the convex one. The axial rotation showed no clear correlation with the asymmetry. CONCLUSIONS Even in non-scoliotic controls is a degree of vertebral body and pedicle asymmetry, but scoliotic vertebrae showed slightly more asymmetry, mostly around the thoracic apex. In contrast to the existing literature, there is no major asymmetry in the true transverse plane in AIS and no uniform relation between the axial rotation and vertebral asymmetry could be observed in these moderate to severe patients, suggesting that asymmetrical vertebral growth does not initiate rotation, but rather follows it as a secondary phenomenon. LEVEL OF EVIDENCE Level 4.

Scoliosis in association with the 22q11.2 deletion syndrome: an observational study

Objective The 22q11.2 deletion syndrome (22q11.2DS) is the most common microdeletion syndrome in humans. It is characterised by wide phenotypic variability, including congenital heart disease (CHD), immunodeficiency and scoliosis. However, little is known regarding the prevalence and characteristics of scoliosis in patients with 22q11.2DS. The objective of this study is to assess the prevalence of scoliosis, its characteristics and the association with CHD in patients with 22q11.2DS. Design This prevalence study is based on physical examination and questionnaires of the world’s largest 22q11.2DS longitudinal collected database (n=1393, Children’s Hospital of Philadelphia) and was augmented with the scoliosis prevalence based on radiography in a smaller cohort (cross-sectional, University Medical Center Utrecht). Patients Patients with a laboratory-confirmed 22q11.2 deletion who visited the specialised outpatient clinics were considered for inclusion. Main outcome measures (1) The prevalence of scoliosis, (2) its association with CHD, and (3) the similarity between 22q11.2DS curve patterns and adolescent idiopathic scoliosis (AIS) curve patterns. Results Within the Philadelphia cohort, the prevalence of scoliosis in patients older than 16 years (n=317) was 48% (n=152). A similar prevalence (49%) was shown for the younger Utrecht cohort (n=97). The occurrence of scoliosis was not associated with the presence of CHD. Sixty-three per cent of patients with scoliosis had a scoliotic curve pattern that resembled AIS. Conclusions Clinicians should be aware that scoliosis is highly prevalent (48%–49%) in association with 22q11.2DS, irrespective of other clinical features (eg, the presence of CHD). Furthermore, 22q11.2DS may provide insights into the causes of AIS.

The Height-Width-Depth Ratios of the Intervertebral Discs and Vertebral Bodies in Adolescent Idiopathic Scoliosis vs Controls in a Chinese Population

Adolescent idiopathic scoliosis (AIS) patients have been reported to be taller and more slender than normal controls, suggesting less mechanical stiffness of their trunk and spine. For assessment of mechanical stiffness, to our best knowledge this is the first to study height-width-depth relations at the level of the individual vertebra and disc in 3-D and to evaluate its relation with the Cobb angle severity. A unique series of high-resolution pre-operative computed tomographic (CT) scans of a total of 105 Chinese patients with moderate to severe AIS and 11 age-matched non-scoliotic controls were used for this study. It was found that some geometric relations differed between primary thoracic curves, secondary curves and normal controls at the individual affected vertebra and disc level. The scoliotic discs in the primary curves were relatively more slender (taller and thinner) than in secondary curves and as compared to controls. In the lumbar spinal area, the vertebral bodies were more slender in the primary as well as secondary AIS curves as compared to the controls. Therefore, if all material properties remain the same, our finding indicates that scoliotic spines may be mechanically less stiff than normal spines. No significant correlation between any of the measures and Cobb angle severity was found.

What is the Actual 3D Representation of the Rib Vertebra Angle Difference (Mehta Angle)

Study Design. Cross-sectional study. Objective. To establish the relevance of the conventional two-dimensional (2D) rib vertebra angle difference (RVAD) and the relationship with the complex three-dimensional (3D) apical morphology in scoliosis. Summary of Background Data. The RVAD, also known as Mehta angle, describes apical rib asymmetry on conventional radiographs and was introduced as a prognostic factor for curve severity in early onset scoliosis, and later applied to other types of scoliosis as well. Methods. An existing idiopathic scoliosis database of high-resolution computed tomography scans used in previous work, acquired for spinal navigation, was used. Eighty-eight patients (Cobb angle 46°–109°) were included. Cobb angle and 2D RVAD, as described by Mehta, were measured on the conventional radiographs and coronal digitally reconstructed radiographs (DRR) of the prone computed tomography scans. A previously validated, semiautomatic image processing technique was used to acquire complete 3D spinal reconstructions for the measurement of the 3D RVAD in a reconstructed true coronal plane, axial rotation, and sagittal morphology. Results. The 2D RVAD on the x-ray was on average 25.3° ± 11.0° and 25.6° ± 12.8° on the DRR (P = 0.990), but in the true 3D coronal view of the apex, hardly any asymmetry remained (3D RVAD: 3.1° ± 12.5°; 2D RVAD on x-ray and DRR vs. 3D RVAD: P < 0.001). 2D apical rib asymmetry in the anatomical coronal plane did not correlate with the same RVAD measurements in the 3D reconstructed coronal plane of the rotated apex (r = 0.155; P = 0.149). A larger 2D RVAD was found to correlate linearly with increased axial rotation (r = 0.542; P < 0.001) and apical lordosis (r = 0.522; P < 0.001). Conclusion. The 2D RVAD represents a projection-based composite radiographic index reflecting the severity of the complex 3D apical morphology including axial rotation and apical lordosis. It indicates a difference in severity of the apical deformation. Level of Evidence: 4

Three-dimensional pelvic incidence is much higher in (thoraco)lumbar scoliosis than in controls

AbstractPurposeThe pelvic incidence (PI) is used to describe the sagittal spino-pelvic alignment. In previous studies, radiographs were used, leading to less accuracy in establishing the three-dimensional (3D) spino-pelvic parameters. The purpose of this study is to analyze the differences in the 3D sagittal spino-pelvic alignment in adolescent idiopathic scoliosis (AIS) subjects and non-scoliotic controls. MethodsThirty-seven female AIS patients that underwent preoperative supine low-dose computed tomography imaging of the spine, hips and pelvis as part of their general workup were included and compared to 44 non-scoliotic age-matched female controls. A previously validated computerized method was used to measure the PI in 3D, as the angle between the line orthogonal to the inclination of the sacral endplate and the line connecting the center of the sacral endplate with the hip axis.ResultsThe PI was on average 46.8° ± 12.4° in AIS patients and 41.3° ± 11.4° in controls (p = 0.025), with a higher PI in Lenke type 5 curves (50.6° ± 16.2°) as compared to controls (p = 0.042), whereas the Lenke type 1 curves (45.9° ± 12.2°) did not differ from controls (p = 0.141).ConclusionLenke type 5 curves show a significantly higher PI than controls, whereas the Lenke type 1 curves did not differ from controls. This suggests a role of pelvic morphology and spino-pelvic alignment in the pathogenesis of idiopathic scoliosis. Further longitudinal studies should explore the exact role of the PI in the initiation and progression of different AIS types.Graphical abstract These slides can be retrieved under Electronic Supplementary Material.

A reliability and validity study for different coronal angles using ultrasound imaging in adolescent idiopathic scoliosis

BACKGROUND CONTEXT Radiation exposure remains a big concern in adolescent idiopathic scoliosis (AIS). Ultrasound imaging of the spine could significantly reduce or possibly even eliminate this radiation hazard. The spinous processes (SPs) and transverse processes (TPs) were used to measure the coronal deformity. Both landmarks provided reliable information on the severity of the curve as related to the traditional Cobb angle. However, it remained unclear which coronal ultrasound angle is the most appropriate method to measure the curve severity. PURPOSE The objective of this study was to test the reliability and the validity of several ultrasound angle measurements in the coronal plane as compared with the radiographic coronal Cobb angle in patients with AIS. STUDY DESIGN/SETTING This is a cross-sectional study. PATIENT SAMPLE The study included 33 patients with AIS, both male and female (Cobb angle range: 3°-90°, primary and secondary curves), who underwent posterior-anterior radiography of the spine. OUTCOME MEASURES The outcome measures were the reliability (intraclass correlation coefficients [ICCs] for the intra- and interobserver variabilities) and the validity (linear regression analysis and Bland-Altman method, including the mean absolute difference [MAD]) of different ultrasound measurements. MATERIALS AND METHODS The patients were scanned using a dedicated ultrasound machine (Scolioscan, Telefield Medical Imaging Ltd, Hong Kong). The reliability and the validity were tested for three coronal ultrasound angles: an automatic and manual SP angle and a manual TP angle as compared with the radiographic coronal main thoracic or (thoraco)lumbar Cobb angles. RESULTS The ICC showed very reliable measurements of all ultrasound methods (ICC ≥0.84). The ultrasound angles were 15%-37% smaller as compared with the Cobb angles; however, excellent linear correlations were seen between all ultrasound angles and the Cobb angle (thoracic: R2≥0.987 and (thoraco)lumbar R2≥0.970), and the Bland-Altman plot showed a good agreement between all ultrasound angles and the Cobb angle. The MADs of the ultrasound angles, corrected using the linear regression equation, and the Cobb angles showed no significant difference between the different ultrasound angles (MAD: automatic SP angle 4.9°±3.2°, manual SP angle 4.5°±3.1°, and manual TP angle 4.7°±3.6°; p≥.388). CONCLUSIONS Coronal ultrasound angles are based on different landmarks than the traditional Cobb angle measurement and cannot represent the same angle values. In this study, we found excellent correlations between the ultrasound and Cobb measurements, without differences in the reliability and validity between the ultrasound angles based on the SPs and TPs. Therefore, the severity of the deformity in patients with AIS can be assessed by ultrasound imaging, avoiding hazardous ionizing radiation and enabling more individualized patient care. It also opens possibilities for screening.

Asymmetry of the Vertebral Body and Pedicles in the True Transverse Plane in Adolescent Idiopathic Scoliosis

Introduction Several studies have reported asymmetry of the vertebral bodies and between the concave and convex pedicles in AIS. There is ongoing debate about its magnitude and whether this caused by a primary growth disturbance, or is secondary to inherent asymmetrical loading within the curvature. The objective of this study is to quantify the asymmetry of the vertebral bodies and pedicles in the true transverse plane in adolescent idiopathic scoliosis (AIS) and to compare this with normal anatomy. Materials and Methods Vertebral body and pedicle asymmetry in the primary thoracic and lumbar curves were evaluated in the true transverse plane of the vertebral bodies on computed tomographic scans of 77 AIS patients with primary curves between 51–105° (thoracic) and 41–88° (lumbar). Magnitude of asymmetry was compared with the corresponding vertebrae in 32 non-scoliotic controls. Vertebral body asymmetry was defined as the percentage of left-right overlap of the vertebral endplates (i.e., 100% indicating perfect symmetry, 0% complete asymmetry). Additionally, the pedicle width and length, length of the ideal pedicle screw trajectory, transverse pedicle angle as well as amount of axial rotation were calculated for each level. Results Vertebrae showed asymmetry both in scoliotics and controls. In thoracic scoliosis, throughout the curve from end vertebra to end vertebra, there was on average significantly more asymmetry than in the controls over the same vertebrae (96.0% in AIS versus 96.4% in controls; p = 0.005). The asymmetry was more pronounced around the apex (95.8%) than at the end vertebrae (96.3%; p = 0.031). The lumbar vertebral bodies in AIS showed a similar pattern, with asymmetry being more pronounced than in controls (95.8% versus 97.2%; p < 0.001), but without significant difference between the apex and the end vertebrae. In the thoracic apex; the concave pedicle was significantly thinner (4.5 versus 5.4mm; p < 0.001) and longer (20.9 versus 17.9mm; p < 0.001) than the convex one, the length of the ideal screw trajectory was longer on the concavity (43.0 versus 37.3mm; p < 0.001) and the transverse pedicle angle was greater (12.3 versus 5.7°; p < 0.001). In the lumbar apex, the concave pedicle was shorter than convex (21.9 versus 24.5 mm; p < 0.001) and its transverse pedicle angle was greater (16.5 versus 9.5°; p = 0.015), there was no significant difference in pedicle width and the length of the ideal screw trajectory between concave and convex in the lumbar apex. The amount of axial rotation within the curve did not correlate with the vertebral asymmetry. Conclusions Even in non-scoliotic controls, there is a slight degree of asymmetry in the true transverse plane of vertebral bodies and pedicles. This vertebral and pedicle asymmetry, however, was slightly more pronounced in moderate to severe scoliosis patients, mostly around the rotated apical zones, with concave pedicles being thinner and longer. No linear relation between the amount of axial rotation and asymmetry could be observed in these severe AIS patients, suggesting that asymmetrical vertebral growth does not initiate rotation, but rather follows it as a secondary phenomenon.