Calculation of 3-D deformity in scoliosis by MRI of the total spine in two perpendicular reconstructed planes

AIM: Scoliosis is a spinal deformity that is more complex and does not exist in one plane only. There have been many attempts to analyse three-dimensional spinal deformity, however, these procedures necessitate higher radiation doses. METHOD: In this study we define angles according to the Cobb Definition. By means of trigonometrical evaluation, 3D calculation of spinal deformity is demonstrated using MRI of the total spine in two reconstructed perpendicular planes. 3D spinal analysis was performed on 41 female and 7 male patients with scoliosis. RESULTS: 79 angles were measured by using the Cobb angle in reconstructed coronal plane of MRI of the total spine and, in addition, by using our method. The scoliosis Cobb angles ranged from 11 - 59 degrees (mean: 23 degrees +/- 9 degrees ), the real angles ranged from 12 - 70 degrees (mean: 32 +/- 14 degrees ). There was a poor correlation between Cobb angles and the 3D calculated angles (r = 0.37; p < 0.0001). CONCLUSION: Our method enables us to determine the real angle of scoliosis and to avoid techniques with any radiation risk for the patient.     

后路全椎弓根螺钉系统治疗青少年特发性脊柱侧凸疗效分析

目的 探讨采用单纯后路全椎弓根螺钉系统治疗青少年特发性脊柱侧凸(AIS)的疗效.方法 2002年4月至2006年7月,连续收治121例AIS患者,其中男性28例,女性93例;年龄10～20岁,平均15.5岁.全部患者采用后路全椎弓根螺钉系统治疗.手术前后在脊柱X线片上测量冠状位Cobb角,矢状面胸椎后凸和腰椎前凸角,最下端融合椎冠状面成角,锁骨角及双肩高度差.骶骨中垂线与融合下端椎、顶椎及C,中垂线平均距离,融合近端交界区后凸角,对以上指标进行对比分析并观察并发症发生情况.结果 平均融合(11.0±1.5)个椎体.冠状面平均矫正率近胸弯为41.8%,主胸弯为70.8%,胸腰.腰弯为74.0%;矢状面各指标无明显改变.主弯顶椎偏移及双肩平衡均得到良好恢复.术后随访36～54个月,未发现假关节形成,且无明显矫形丢失;1例患者出现附加现象,4例患者出现术后近胸弯失代偿,15例患者出现近端交界性后凸.结论 后路全椎弓根螺钉系统治疗AIS能获得良好的矫正率,并发症少,疗效满意.     

Three-dimensional measurement of wedged scoliotic vertebrae and intervertebral disks

Idiopathic scoliosis involves complex spinal intrinsic deformations such as the wedging of vertebral bodies (VB) and intervertebral disks (ID), and it is obvious that the clinical evaluation obtained by the spinal projections on the two-dimensional (2D) radiographic planes do not give a full and accurate interpretation of scoliotic deformities. This paper presents a method that allows reconstruction in 3D of the vertebral body endplates and measurement of the 3D wedging angles. This approach was also used to verify whether 2D radiographic measurements could lead to a biased evaluation of scoliotic spine wedging. The 3D reconstruction of VB contours was done using calibrated biplanar X-rays and an iterative projection computer procedure that fits 3D oriented ellipses of adequate diameters onto the 3D endplate contours. “3D wedging angles” of the VB and ID (representing the maximum angle between adjacent vertebrae) as well as their angular locations with respect to the vertebral frontal planes were computed by finding the positions of the shortest and longest distances between consecutive endplates along their contour. This method was extensively validated using several approaches: (1) by comparing the 3D reconstructed endplates of a cadaveric functional unit (T₈-T₉) with precise 3D measurements obtained using a coordinate measuring machine for 11 different combinations of vertebral angular positions; (2) by a sensitivity study on 400 different vertebral segments mathematically generated, with errors randomly introduced on the digitized points (standard deviations of 0.5, 1, 2, and 3 mm); (3) by comparing the clinical wedging measurements (on postero-anterior and lateral radiographs) at the thoracic apical level of 34 scoliotic patients (15° < Cobb < 45°) to the computed values. Mean errors for the 11 vertebral positions were 0.5 ± 0.4 mm for VB thickness, less than 2.2° for endplate orientation, and about 11° (3 mm) for the location of the maximum 3D wedging angle along the endplate contour. The errors below 2 mm (introduced on the digitized points) slightly affected the 3D wedging angle (< 2°) and its location (< 4°) for the ID. As for the clinical evaluation, average angular errors were less than 0.4° in the radiographic frontal and lateral planes. The mean 3D wedged angles were about 4.9°± 1.9° for the VB and 6.0°± 1.7° for the ID. Linear relations were found between the 2D and the 3D angles, but the 3D angles were located on diagonal planes statistically different than the radiographic ones (between 100° and 221°). There was no statistical relation between the 2D radiographic angles and the locations of the 3D intervertebral wedging angles. These results clearly indicate that VB and ID endplates are wedged in 3D, and that measurements on plain radiographs allow incomplete evaluation of spinal wedging. Clinicians should be aware of these limitations while using wedging measurements from plain radiographs for diagnosis and/or research on scoliotic deformities. Received: 4 January 1997 Revised: 26 July 1997 Accepted: 1 August 1997     

Relationship between Quantec measurement and Cobb angle in patients with idiopathic scoliosis

The Quantec Spinal Imaging System (QSIS) is a raster stereography used to measure three-dimensional trunk images. The Q angle, a coronal plane measurement generated by the Quantec Spinal Imaging System (QSIS), was compared with the Cobb angle in assessment of scoliosis curve magnitude. One hundred forty-nine patients with idiopathic scoliosis were evaluated using both the Quantec system and plane radiographs. The Cobb and Q angles demonstrated significant correlation in the thoracic region (r = 0.65, p < 0.05), lumbar region (r = 0.63, p < 0.05), and in the thoracolumbar region (r = 0.70, p < 0.05). The difference between the Q and Cobb angles was small when the Cobb angle was <21 degrees with less than 6 degrees of axial surface rotation, as measured by the QSIS method. For smaller curves with minimal rotation, there is close correlation between the Cobb angle and the Quantec angle.     

Posterior pedicle screws combined with shortening and release techniques for lumbar and thoracolumbar adolescent idiopathic scoliosis

Objective: To prospectively evaluate the clinical and radiographic effects of posterior surgery with wide posterior shortening release and segmental pedicle screws techniques in a consecutive group of patients with thoracolumbar /lumbar adolescent idiopathic scoliosis. Methods: Between April 2002 and July 2005, 114 patients (86 women and 28 men) were enrolled in this study. There were 72 Lenke type 5, 32 Lenke type 6, and 10 Lenke type 3C curves. Radiographic parameters such as coronal plane Cobb angle; lordosis angle; lowest instrumented vertebrae (LIV) angulation; and the distances from the central sacral vertical line (CSVL) to the LIV, to the apical vertebra and to the C7 plumb line, were analyzed. Complication rates were also recorded during follow‐up. Results: The average coronal correction was from 61° to 13° (78.6%). In the sagittal plane, lumbar lordosis was normalized from 36° with a wide range (23°–67°) to 42° with a normal range (34°–55°). The LIV had 79% correction of coronal angulations. The center sacral line to LIV was improved from 2.3 cm to 0.5 cm, apex to center sacral line from 5.0 cm to 1.6 cm, and CSVL from 2.7 cm to 0.8 cm. A total of 1460 pedicle screws were placed safely, average 9.6 levels (5–14) were fused. The patients were followed up for an average of 30 months (range, 12–50). There was excellent maintenance of correction at final follow‐up. Conclusion: Wide posterior release and segmental pedicle screw instrumentation has excellent radiographic and clinical results with minimal complications.     

椎弓根固定建立山羊脊柱侧凸模型

目的 探讨未成年山羊行椎弓根螺钉原位固定自然形成侧凸模型的可行性.方法 未成年雌性山羊13只,年龄6.5～8.5周,体重9～11 kg.体表定位,全身麻醉下行胸腰段正中小切口,固定右侧T12、T13和L3椎弓根,钛棒连接原位固定.术前、术后即刻、术后2个月和3个月拍脊柱x线正侧位片,观察脊柱侧凸的进展情况.结果 1只山羊因麻醉过量、术后死亡.另外12只山羊无感染、螺钉松动等并发症发生.随着时间延长Cobb角不断增大,术前、术后即刻Cobb角为O°,术后2个月Cobb角为(16.34±1.07)°(14.5～17.8)°.术后3个月Cobb角为(21.06±1.09)°(19.2～22.4)°.术后3个月取脊柱标本时去除内固定物,证实侧弯为结构性.结论 通过单侧椎弓根螺钉原位固定、可以最大程度上避免脊柱及其附属结构的损伤,借助未成年山羊的自然生长,可以建立良好的脊柱侧凸模型.     

Radiation-free quantitative assessment of scoliosis: a multi center prospective study

Accurate quantitative measurements of the spine are essential for deformity diagnosis and assessment of curve progression. There is much concern related to the multiple exposures to ionizing radiation associated with the Cobb method of radiographic measurement, currently the standard procedure for diagnosis and follow-up of the progression of scoliosis. In addition, the Cobb method relies on 2-D analysis of a 3-D deformity. The aim of this prospective study was to investigate the clinical value of Ortelius800^TM that provides a radiation-free method for scoliosis assessment in three planes (coronal, sagittal, apical), with simultaneous automatic calculation of the Cobb angle in both coronal and sagittal views. Analysis of the clinical value of the device for assessing spinal deformities was performed on patients with adolescent idiopathic scoliosis, deformity angles ranging from 10° to 48°. Correlation between Cobb angles measured manually on standard erect posteroanterior radiographs and those calculated by Ortelius800^TM showed an absolute difference between the measurements to be significantly less than ± 5° for coronal measurements and significantly less than ± 6° for sagittal measurements indicating good correlation between the two methods. The measurements from four independent sites and six independent examiners were not significantly different. We found the novel clinical tool to be reliable for following mild and moderate idiopathic curves in both coronal and sagittal planes, without exposing the patient to ionizing radiation. Considering the need for further validation of this new method, any change in treatment protocol should still be based on radiographic control.     

Sagittal Cobb-angle measurements in scoliosis with MRI whole spine imaging

AIM: A newly developed MR procedure allows imaging of the whole spine in coronal and sagittal planes. We studied the use of total spine MR imaging in measuring sagittal Cobb angles in scoliosis. METHOD: 64 patents with idiopathic scoliosis (mean age 18.1 years, 35 thoracic, 20 double major, and 9 lumbar curves) and 27 patients without scoliosis were consecutively examined. The MR images were acquired in the supine position. The sagittal Cobb angles were measured between T4-T12 and between T12-L5. RESULTS: For the group of the thoracic and double major scoliosis the mean sagittal Cobb angle (T4-T12) was 13 degrees and for the group without scoliosis 23 degrees, which was a significant difference (p < 0.01, Mann Whitney-U-test). There was a negative correlation between the sagittal Cobb angles (T4-T12) and the lateral, thoracic curves. The mean sagittal Cobb angle (T12-L5) of the group with lumbar and double major curves was 35 degrees, which was not a significant difference when compared to 37 degrees of the non-scoliotic group. CONCLUSION: Using total spine MR imaging the lordotic aspect of the thoracic deformation in scoliosis can be reliably measured. Because of the absent radiation exposure the sagittal MR reconstructions could be used as an additional imaging in monitoring scoliosis.     

Reliability of 2 Smartphone Applications for Cobb Angle Measurement in Scoliosis

BackgroundAs mobile technology has evolved, smartphone applications have been used for radiographic angle measurements in daily clinical practice. This study aimed to assess the reliability of 2 smartphone applications (iPinPoint and Cobbmeter) in measuring scoliosis Cobb angles compared with picture archiving and communication system (PACS) tools.MethodsAnteroposterior whole spinal digital radiographs of 50 patients were retrospectively analyzed. Four observers measured Cobb angles of predetermined major structural curves using the tools in the PACS software and 2 smartphone applications. The inter- and intraobserver reliabilty were measured using intraclass correlation coefficients (ICC).ResultsVery good interobserver agreement was seen with PACS, iPinPoint, and Cobbmeter measurements (ICC, 0.991, 0.980, and 0.991, respectively). Intraobserver reliability of the 4 observers was also very good for all techniques (ICC > 0.9 for all observers).ConclusionsBoth smartphone applications were reliable in measuring scoliosis Cobb angles, with reference to PACS tools. They may be useful when digital or manual mesurement tools are not available.     

Effect of rotation on frontal plane deformity in idiopathic scoliosis

To analyze the effect of rotation on frontal plane deformity in idiopathic scoliosis, 44 patients with idiopathic scoliosis aged 11 to 18 years were examined using standing anteroposterior and true AP radiographs. Axial rotation was measured by computed tomography. Patients were divided into two groups according to Cobb angle: patients with angles <30 degrees comprised group 1 and patients with angles >30 degrees comprised group 2. Cobb angle increased with true-AP projection a mean of 21.2% in group 1 and 16.7% in group 2. Rotation degree was significantly correlated with increasing degree of frontal plane deformity (P<.01) in group 1 but not in group 2 (P>.05). These results demonstrate the influence of rotation over frontal plane deformity and is more apparent at curves >30 degrees.     

经椎弓根截骨与非截骨技术治疗中重度脊柱侧后凸的临床研究

目的探讨对于中重度脊柱侧后凸畸形,采用经椎弓根截骨(pedicle subtraction osteotomy,PSO)技术和非截骨技术治疗的临床效果。方法 2005年1月-2009年1月,对99例中重度脊柱侧后凸畸形患者分别采用PSO截骨(PSO截骨组,46例)和非截骨技术(非截骨组,53例)行后路矫形治疗。两组患者性别、年龄、术前主侧凸Cobb角、胸腰段后凸Cobb角等一般资料比较差异无统计学意义(P>0.05),有可比性。分别记录两组手术时间、出血量,术后测量脊柱主侧凸Cobb角、胸腰段后凸Cobb角,并计算侧凸和后凸矫正率以及末次随访的矫正率丢失。结果患者均顺利完成手术。PSO截骨组患者手术时间和出血量均多于非截骨组,比较差异有统计学意义(P<0.05)。所有患者均获随访,随访时间12～56个月,平均22.4个月。两组均未出现脊髓神经损伤,末次随访时均获得良好的骨性融合。两组患者术后2周及末次随访时的主侧凸Cobb角及胸腰段后凸Cobb角均较术前显著改善(P<0.05)。术后2个时间点的主侧凸Cobb角、矫正率两组间比较差异均无统计学意义(P>0.05);但PSO截骨组末次随访时的矫正率丢失明显小于非截骨组(P<0.05)。术后2个时间点的胸腰段后凸Cobb角、矫正率及矫正率丢失,PSO截骨组均优于非截骨组,差异有统计学意义(P<0.05)。结论对于中重度脊柱侧后凸畸形,PSO截骨技术较非截骨技术在冠状面侧凸的矫形方面无显著差异,但能够获得更好的脊柱矢状面后凸矫形效果;但PSO截骨的手术时间和出血量会显著增加。     

Ideal starting point and trajectory for C2 pedicle screw placement: a 3D computed tomography analysis using perioperative measurements

Background contextC2 pedicle screws provide stable fixation for posterior cervical fusion. Placing C2 pedicle screws is fraught with risks, and a misplaced screw can result in cortical breach of the pedicle, resulting in injury to the vertebral artery or spinal cord.PurposeWe sought to identify a reproducible starting point and trajectory for C2 pedicle screw placement using three-dimensional (3D) computed tomography (CT) imaging. Our aims included identifying correct cephalad and mediolateral angles used for determining the most accurate trajectory through the C2 pedicle.Study designA radiographic analysis of the anatomy of the C2 pedicle using CT.Patient sampleA random sample of 34 cervical spine CT scans in patients without medical or surgical pathology of the cervical spine.Outcome measuresNormal anatomic measurements made in the axial and sagittal planes of the CT scans. Angles and measures in millimeters were recorded.MethodsThe C2 pedicles were evaluated using CT scanning with a 3D imaging application. The ideal trajectory through each pedicle was plotted. The mediolateral and cephalad angles were measured using the midline sagittal plane and the inferior vertebral body border as references. Other measurements made were the distances through the pedicle and vertebral bodies, and the surface distances along the laminae between the isthmus and the starting point of the chosen trajectories. Other measurements involving the height of the laminae were also made. The mean values, standard deviations, and intraobserver variations are presented.ResultsCT scans from 34 patients were reviewed. The sex of the patient did not predict angle measurements (p=.2038), so combined male and female patient measures are presented. The mean mediolateral angle measured was 29.2°, and the mean cephalad angle was 23.0°. The mean distance along the lamina surface between the isthmus and the starting point was 8.1 mm. The mean distance from the superior border of the lamina to the starting point was 5.7 mm. There were no statistically significant differences between the dataset collected in duplicate by the same observer (p=.74); as such, we present one data analysis on combined data from the two datasets collected.ConclusionIt is possible to determine an ideal trajectory through the C2 pedicle. These measurements may facilitate C2 pedicle screw fixation decreasing the risk of injury to the vertebral artery, spinal cord, or nerve roots. Delineating the individual anatomy in each case with imaging before surgery is recommended.     

Radiological presentations in relation to curve severity in scoliosis associated with syringomyelia

BACKGROUND: Few radiographic guidelines are available to assist clinicians in deciding when to order magnetic resonance imaging in patients with a normal history and physical examination. Most of the recent reports on the radiographic characteristics of scoliosis are limited by a small number of patients and a shortage of large curves. The association between radiological features and the severity of scoliosis has little been elaborated. The purpose of this study is to further explore the radiological presentations in relation to curve severity in scoliosis associated with Chiari malformation and syringomyelia. METHODS: A total of 87 children and adolescents were divided into 3 groups: group 1 (10 degrees < or = Cobb angle < or = 30 degrees), group 2 (30 degrees < Cobb angle < or = 60 degrees), and group 3 (Cobb angle > 60 degrees). Curves were classified into typical and atypical patterns in the coronal plane, and the sagittal profile was measured. Cerebellar tonsillar descent or syrinx patterns in relation to curve severity and the frequency of atypical curves were also investigated. RESULTS: The frequency of atypical curve patterns from groups 1 to 3 was 46.2%, 45.2%, and 40.7%, respectively. A total of 65.3% of patients with typical curve patterns had atypical features in all of the 3 groups. There was a significant difference of kyphotic angle among the 3 groups showing that the larger curves tended to have greater thoracic kyphosis. Both the degree of cerebellar tonsillar descent and syrinx patterns had no correlation with the curve severity or the frequency of atypical curves. CONCLUSIONS: These results show that radiographic presentations including atypical curve patterns, atypical features in typical curve patterns, and a normal to hyperkyphotic thoracic spine may suggest the need for a preoperative magnetic resonance imaging. Kyphosis may be indicative of progressive scoliosis. There is no evidence to suggest that the degree of cerebellar tonsillar descent and syrinx patterns have an effect on the progress of scoliosis and the frequency of atypical curves.     

Morphometry of the lumbar spine: anatomical perspectives related to transpedicular fixation

The pedicles of lumbar vertebrae were measured both directly and radiographically to determine the differences between the sexes and the accuracy of radiographic measurement. The lumbar pedicles of cadavera of forty-nine patients--twenty-four men and twenty-five women--who died between the ages of sixty and ninety-eight years were measured directly and on radiographs. The pedicles of lumbar vertebrae from fifty-one patients--twenty-three men and twenty-eight women--between the ages of twenty and fifty years who had low-back problems were measured on radiographs and computerized tomographic scans. Comparison revealed that the average transverse and sagittal diameters of the pedicles and the distance from the posterior aspect of the laminar cortex to the anterior aspect of the cortex of the vertebral body along the central axis of the pedicles were 5 to 20 per cent greater in men, but the transverse and sagittal angles of the pedicle did not differ significantly between the sexes. Measurements on radiographs and computerized tomographic scans of the transverse angles of the pedicles and of the distances from the posterior aspect of the laminar cortex to the anterior aspect of the cortex of the vertebral body from the second to the fifth lumbar vertebra were greater than direct measurements, even without magnification. Direct measurements of the diameters of the transverse and sagittal diameters of the pedicle of the fifth lumbar vertebra, however, were greater than the radiographic measurements.     

Estimation of spinal deformity in scoliosis from torso surface cross sections.

STUDY DESIGN: Correlation of torso scan and three-dimensional radiographic data in 65 scans of 40 subjects. OBJECTIVES: To assess whether full-torso surface laser scan images can be effectively used to estimate spinal deformity with the aid of an artificial neural network. SUMMARY OF BACKGROUND DATA: Quantification of torso surface asymmetry may aid diagnosis and monitoring of scoliosis and thereby minimize the use of radiographs. Artificial neural networks are computing tools designed to relate input and output data when the form of the relation is unknown. METHODS: A three-dimensional torso scan taken concurrently with a pair of radiographs was used to generate an integrated three-dimensional model of the spine and torso surface. Sixty-five scan-radiograph pairs were generated during 18 months in 40 patients (Cobb angles 0-58 degrees ): 34 patients with adolescent idiopathic scoliosis and six with juvenile scoliosis. Sixteen (25%) were randomly selected for testing and the remainder (n = 49) used to train the artificial neural network. Contours were cut through the torso model at each vertebral level, and the line joining the centroids of area of the torso contours was generated. Lateral deviations and angles of curvature of this line, and the relative rotations of the principal axes of each contour were computed. Artificial neural network estimations of maximal computer Cobb angle were made. RESULTS: Torso-spine correlations were generally weak (r < 0.5), although the range of torso rotation related moderately well to the maximal Cobb angle (r = 0.64). Deformity of the torso centroid line was minimal despite significant spinal deformity in the patients studied. Despite these limitations and the small data set, the artificial neural network estimated the maximal Cobb angle within 6 degrees in 63% of the test data set and was able to distinguish a Cobb angle greater than 30 degrees with a sensitivity of 1.0 and specificity of 0.75. CONCLUSIONS: Neural-network analysis of full-torso scan imaging shows promise to accurately estimate scoliotic spinal deformity in a variety of patients.     

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.

Combined anterior and posterior instrumentation in severe and rigid idiopathic scoliosis

A prospective clinical and radiographic evaluation of 33 consecutive patients with severe and rigid idiopathic scoliosis (average Cobb angle 93°, flexibility on bending films 23%) were treated with combined anterior and posterior instrumentation with a minimum follow-up of 2 years. All patients underwent anterior release and VDS-Zielke Instrumentation of the primary curve. In highly rigid scoliosis, this was preceded by a posterior release. Finally, posterior correction and fusion with a multiple hook and pedicle screw construct was performed. Thirty patients were operated in one stage, three patients in two stages. Preoperative curves ranged from 80 to 122° Cobb angle. Frontal plane correction of the primary curve averaged 67% with an average loss of correction of 2°. The apical vertebral rotation of the primary curve was corrected by 49%. In all but three patients, sagittal alignment was restored. There were no neurological complications, deep wound infections or pseudarthrosis. Combined anterior and posterior instrumentation is safe and enables an effective three-dimensional curve correction in severe and rigid idiopathic scoliosis.     

Cotrel-Dubousset instrumentation for the treatment of severe scoliosis

In a multicentric study, 36 cases (40 curves) of severe scoliosis were analysed; 19 were idiopathic and 17 neurological, Cobb angles ranged from 70° to 145°, all had undergone three-rod Cotrel-Dubousset (CD) instrumentation. The correction on the frontal plane achieved more than 50% of the preoperative angle (53.9% for idiopathic curves and 55.6% for neurological ones). On the sagittal plane the pathological shape of the spine was reduced and distinctly ameliorated. In ten patients, the authors successfully applied a technique, alternative to the original one, which was based on the use of two or three screws in the lumbar area, one supplementary pedicle transverse claw on the cranial area and two rods connected by a domino, instead of a single rod (the longer one applied on the concave side). The main complications were: one case of infection, three of vascular compression of the duodenum, one of crank-shaft phenomenon and one laminar hook displacement. The excellent result achieved in both, idiopathic and neurological severe and stiff scoliosis shows the efficacy, reliability and versatility of CD three-rod instrumentation. Received: 28 November 1997 Revised: 9 July 1998 Accepted: 3 August 1998