Horizontal plane morphometry of normal and scoliotic vertebrae

Summary Computed tomography (CT) scans are widely used for quantification of the morphology of the vertebral body and of the changes of the thoracic cage in the horizontal plane in scoliosis. So far, however, no method exists for precise quantification of the parameters of the posterior elements. We present a method for quantification on the basis of CT scans of different parameters of the morphology of both the vertebral body and posterior elements in the horizontal plane. The precision and accuracy of the method were estimated in a model study by CT scanning of a normal and a scoliotic vertebra in different, controlled, tilted positions. Moreover, in a clinical study CT scans of 19 thoracic vertebrae from non-scoliotic subjects and the apex vertebra from 40 scoliotic subjects were selected to test the applicability of the method to clinical studies. The intra- and interobserver variation of the measurements was analysed. The angle between the longitudinal axis of the vertebral body and that of the whole vertebra was used to evaluate the asymmetry of the vertebral body. The right to left pedicle width index, the right to left hemi-canal width index and the index of transverse process angles related to the axis of the vertebra were used to quantify the asymmetry of the posterior elements. The results indicate that, except for the pedicle width index, the variables under study were not significantly influenced by a 5° or 10° tilt ventrally, dorsally, or laterally of either the normal or the scoliotic vertebra. Hence, the method can be satisfactorily applied to longitudinal group comparisons. However, its use in longitudinal studies of individual patients is questionable.     

3D MRI在脊柱侧弯畸形矫形术前的临床应用价值

目的探讨3D MRI在脊柱侧弯患者矫形术前的临床应用价值。方法对100例脊柱侧弯患者行术前3DMR检查,采用3D-SPACE T2W序列,多平面重组图像,测量T4、顶椎、L1水平脊髓和椎体的轴位旋转角,观察测量所得顶椎脊髓旋转角与Cobb角的相关性,并进行统计学分析,对顶椎水平脊髓旋转与椎体旋转进行对比。结果顶椎水平脊髓旋转角与Cobb角存在相关性。顶椎水平脊髓旋转可分为3种类型,过度旋转型80例,旋转不足型13例,相反旋转型7例。35例患者最大脊髓旋转角不在顶椎水平。脊髓旋转与椎体旋转不同,在Cobb角大者,大部分脊髓旋转角度大于椎体旋转。MR检查发现2例合并多发神经纤维瘤,1例脊髓空洞,1例蝴蝶椎畸形,5例半椎体并蝴蝶椎畸形,1例合并腹股沟斜疝。结论脊髓、椎体旋转的大小及类型存在差异。脊柱侧弯患者常合并脊髓及椎体多发畸形,3DMR检查在脊柱侧弯畸形矫形术前评估中起着重要作用。     

The position of the aorta relative to the spine: a comparison of patients with and without idiopathic scoliosis

BACKGROUND: There is little information documenting the relationship of the aorta to the thoracic scoliotic spine. Recent studies have suggested that the ends of screws placed during an anterior spinal arthrodesis, and pedicle screws used for the treatment of right thoracic scoliosis, may be in proximity to the aorta. The purpose of this study was to analyze the anatomical relationship between the aorta and the spine in a comparison of patients with idiopathic right thoracic scoliosis and patients with a normal spine. METHODS: Thirty-six patients with adolescent idiopathic scoliosis with a right thoracic curve and forty-three with a normal straight spine were studied. Radiographs were analyzed to determine the Cobb angle, the apex of the curve, and the apical vertebral rotation for the patients with scoliosis. Axial magnetic resonance images from the fourth thoracic vertebra to the third lumbar vertebra at the midvertebral body level were used to measure the distance from the aorta to the closest point of the vertebral body cortex, the distance from the posterior edge of the aorta to the spinal canal, and the aorta-vertebral angle. RESULTS: No differences were found between the groups with respect to age or sex distribution. For the scoliosis and normal groups, boys had greater average vertebral body width and depth for all levels than did girls (p < 0.05). For the scoliosis group, the most common apical vertebra was the eighth thoracic vertebra, the average coronal curve measurement was 55.2 degrees, and the average apical rotation was 17.3 degrees. The average distance from the aortic wall to the vertebral body cortex at the apex of the curve was greater in the patients with scoliosis (4.0 mm) than at similar levels in the normal group (2.5 mm) (p < 0.05). The distance from the posterior aspect of the aorta to the anterior aspect of the spinal canal was less in the scoliosis group (11.1 mm) than in the normal group (19.2 mm) for the fifth to the twelfth thoracic level (p < 0.05). The aorta was positioned more laterally and posteriorly adjacent to the vertebral body at the fifth to the twelfth thoracic level in patients with scoliosis compared with that in normal patients as reflected in a smaller aorta-vertebral angle (p < 0.05). With an increasing coronal Cobb angle in the thoracic curve and apical vertebral rotation, the aorta was positioned more laterally and posteriorly (p < 0.05). CONCLUSION: In patients with right thoracic idiopathic scoliosis, the aorta is positioned more laterally and posteriorly relative to the vertebral body compared with that in patients without spinal deformity.     

Segmental vertebral rotation in early scoliosis

Summary In order to investigate the development of the vertebral axial rotation in patients with early scoliosis, the vertebral rotation angle (VRA) was quantified on the basis of 132 anteroposterior radiographs obtained from patients with diagnosed or suspected scoliosis. The rotation was measured in the apical vertebra and in the two suprajacent and two subjacent vertebrae. The radiographic material was divided into a control reference group and three scoliotic groups with varying Cobb angle from 4° up to 30°. In the reference group a slight vertebral rotation was significantly more often seen to the right. In the scoliotic groups, the rotation was most pronounced in the apical segments. The mean VRA toward the convex side was significantly increased in the vertebrae just suprajacent to the apex in curves with a Cobb angle of 8°–15° and in the cranial four vetebrae in curves with a Cobb angle of 16°–30°. Atypical vertebral rotation to the opposite side of the major curve was observed in 12.8% of the cases. There was a significant positive correlation between the VRA and the Cobb angle. These results show that a slight VRA to the right is a common feature in the normal spine, and that the VRA increases with progressive lateral deviation of the spine. It is concluded that the coronal plane deformity in early idiopathic scoliosis is accompanied and probably coupled to vertebral rotation in the horizontal plane.     

Rib deformity in scoliosis

Rib deformity in scoliosis is of interest because it may help in the diagnosis, and also, in some pronounced cases, it may need correction by costoplasty. There are, however, debates about its use in diagnosis, because some authors think that rib deformity is not closely related to either the magnitude or the extent of rotation of the curve. In order to define the relation between rib deformity and scoliosis, 11 patients were recruited who were to undergo scoliosis surgery and thoracoplasty, and anteroposterior (AP) T1-S1 standing radiographs, computerized tomography (CT) scans, and three-dimensional (3D) reconstructions were obtained. From the radiographs, the most rotated vertebra, the Cobb angle, the apex and the type of the curve were determined. From the CT scans and 3D reconstructions, the exact level of the rib deformity measured was matched with the corresponding vertebral level. In this way, the most rotated vertebra and the most prominent part of the rib cage deformity were identified. The most rotated vertebra was found to be at the same level in both radiographs and CT scans in only five patients. In the rest of the patients, CT scans showed it either one level higher or lower than it appeared on the radiograph. The most prominent part of the rib cage deformity was at the same level as the most rotated vertebra in two patients, and in the rest of the patients it was one, two or three vertebral levels lower. There was no association between the Cobb angle, vertebral rotation and rib deformity. A CT scan is necessary preoperatively in patients who will undergo a costoplasty, to determine the exact levels of the prominence. However, a scanogram or a 3D reconstruction is required for exactly matching the most prominent part of the rib cage deformity to the corresponding vertebral level.     

Correction of flexible thoracic scoliosis below 65 degrees—A radiological comparison of anterior versus posterior segmental instrumentation applied to similar curves

Direct comparison of the correction of scoliosis achieved by different surgical methods is usually limited by the heterogeneity of the patients analyzed (their age, curve pattern, curve magnitude, etc.). The hypothesis is that an analysis of comparable scoliotic curves treated by different implant systems could detect subtle differences in outcome. The objective of this study was therefore: (1) to measure the 3D radiological parameters of scoliotic deformity and to quantify their postoperative changes, and (2) to compare the radiographic results achieved with one anterior and one posterior instrumentation methods applied to similar curves but representing different mechanisms of correction. Material and methods: The clinical notes and radiographs of 46 patients operated on for adolescent idiopathic scoliosis were reviewed. The inclusion criteria consisted of: a single thoracic curve, right convex, a frontal Cobb angle minimum of 45° and a maximum of 65°, flexibility on a lateral bending test of more than 30%, and a Risser test value of between 1 and 4. The operative procedures were: Cotrel-Dubousset instrumentation (CDI) for 25 patients (the CD group) and correction by anterior instrumentation (Pouliquen plate) for 21 patients (the ANT group). Preoperative and postoperative long cassette standing antero-posterior and lateral radiographs were examined. The frontal and sagittal thoracic Cobb angle, apical vertebra transposition (AVT), apical vertebra rotation (AVR), lowest instrumented vertebra (LIV) tilt, C7 vertebra shift and rib cage shift (RCS) were all compared. A computed reconstruction was produced with Rachis-91 software. Vertebral axial rotation angle was evaluated throughout the spine. Results: Postoperative assessment revealed a mean correction of the frontal Cobb angle of 37.0° for the CD group and 41.0° for the ANT group. The AVT operative correction was 45.8 and 42.7 mm, respectively, and AVR correction was 1.8 and 12.6°, respectively. The postoperative change of the sagittal Th4–Th12 Cobb angle was not significant for any method but it was significant (P=0.05) for the CD group if the curves were divided preoperatively into hypokyphotic and normokyphotic subgroups and then analyzed separately. Computed assessment demonstrated a correction of segmental axial rotation of more than 50% in the main thoracic curve in the ANT group, significantly more than that in the CD group (P<0.001). Conclusions: Anterior instrumentation provided better correction of the vertebral axial rotation and of the rib hump. CD instrumentation was more powerful in translation and more specifically addressed the sagittal plane: the postoperative thoracic kyphosis angle increased in the hypokyphotic curves and slightly decreased in the normokyphotic curves.     

The segmental effect of Cotrel-Dubousset instrumentation on vertebral rotation,rib hump and the thoracic cage in idiopathic scoliosis

The segmental effect of Cotrel-Dubousset instrumentation (CDI) on the spine and thoracic cage was investigated in 38 patients with adolescent idiopathic scoliosis by preoperative and postoperative postero-anterior and lateral radiographs and computed tomography from T1 to S1. Mean Cobb angle decreased by 67%. The T5–T12 kyphosis in the hypokyphotic patients increased on average by 8.4° (P<0.001). Average preoperative as well as postoperative maximal vertebral rotation was located at the apex level, and was reduced from 19.0° to 14.3° (P<0.001). All vertebrae between the upper and lower instrumented vertebrae were significantly derotated. Average derotation for the apical zone was 4.8° (P<0.001), for the upper instrumented zone it was 2.5° (P<0.01), and for the lower instrumented zone it was 2.6° (P<0.01). Vertebral derotation was significantly higher in the apical zone than in the upper and lower instrumented zones. The apical rib hump index (RHi) decreased by 38% (P<0.001) and the cumulative RHi for the five apical levels decreased by 34% (P<0.001). The RHi for the two levels above and below the instrumentation each decreased by 20% (n.s.). No significant increase in sagittal or transverse rib cage diameter at any level was observed. The translation in the coronal plane of the apical vertebra of major right thoracic curves improved significantly (P<0.001). The preoperative flexibility index of the major curve correlated positively (r=0.47) with derotation at the apex level (P<0.01). However, no correlation was found between flexibility index and reduction of RHi at the apex level. Vertebral derotation did not correlate with reduction in RHi at any level. The study shows that CDI results in a postoperative three-dimensional improvement of the spine and a limited improvement of the thoracic cage, with no tendency towards a worsened deformity at any level within or outside the instrumentation.     

Vertebral rotation and pedicle length asymmetry in the normal adult spine

Summary Rotation in the horizontal plane of vertebra T8, T9 or T10 was determined on CT scans of 25 male and 25 female patients with normal spines. The pedicle length was measured using a new method, and the right/left pedicle length index was calculated. In 38 (76%) of the patients there was vertebral rotation to the right with a mean Cobb angle of 3.0°, and in 4 (8%) rotation to the left, mean Cobb angle 2.2° (P0.01). In 8(16%) there was no measurable rotation. The pedicle length index was greater than 1.05 in 9 subjects, between 0.95 and 1.05 in 16 and less than 0.95 in 25, indicating a predominance of longer pedicles on the left side. In 21 out of the 38 patients with vertebral rotation to the right, the left pedicle was longer than the right one (P0.01). The results indicate that the normal spine is afflicted with a vertebral rotation to the right in association with a longer pedicle on the left. The significance of these observations for the pathogenesis of idiopathic scoliosis remain uncertain.     

Rib cage deformities in scoliosis: Spine morphology,rib cage stiffness,and tomography imaging

A computer-implemented biomechanical model of a thoracolumbar spine and deformable rib cage was used to investigate the influence of spine morphology and rib cage stiffness properties on the rib cage deformities that arise from scoliosis and to study the relationship of actual rib distortions with those seen on computed tomography (CT) scans. For the purposes of this study, it was assumed that rib cage deformities result from forces imposed on the ribs by the deforming spine. When a structurally normal rib cage was allowed to follow freely the imposition of scoliotic curves on the spine, different configurations of scoliosis led to substantial differences in the resulting rib cage deformities. Rib cage lateral offset correlated well with the Cobb angle of the scoliosis but not with the apical vertebral axial rotation, whereas rib cage axial rotation correlated well with apical vertebral axial rotation but not with the Cobb angle. These model-obtained findings mirror clinical findings that correction of the Cobb angle leads to correction of the lateral offset of the rib cage but does not correlate well with correction of the rib cage axial rotation. The stiffnesses of the ligamentous tissue connecting the sternum to the pelvis, of the costovertebral joints, and of the ribs themselves also influenced the rib deformities substantially. The influence of the sternopelvic ligamentous ties has not been recognized previously. The total rib cage volume remained essentially constant regardless of the severity of the resulting deformity, but the distribution of this volume between convex and concave sides varied somewhat. Simulated CT scans of model rib cages suggested that distortions of individual ribs are substantially exaggerated in such images.     

Vertebral rotation and thoracic torsion in adolescent idiopathic scoliosis: what is the best radiographic correlate?

BACKGROUND: As a result of the increased appreciation of the three-dimensional nature of scoliosis and modern spinal instrumentation's improved corrective capabilities, there has been renewed interest in the correction and measurement of vertebral rotation. Computed tomography (CT), the gold standard for accuracy, is limited in its clinical utility owing to cost, radiation exposure, and the effects of postural changes on scoliosis curves and vertebral rotation. Consequently, the Perdriolle and Nash-Moe techniques remain the standard measurements for providing a reasonable estimate of pre- and postoperative vertebral rotation because of their simplicity. However, these techniques have considerable interobserver variability, and pedicle screw instrumentation obscures the landmarks necessary for utilizing these techniques for postoperative vertebral rotation assessment. The purpose of the present study was to assess the utility of alternate radiographic measures to assess vertebral rotation and thoracic torsion when compared with conventional measures on pre- and postoperative radiographs and CT evaluation. METHODS: We reviewed the preoperative, immediate postoperative, and final follow-up radiographs, as well as the pre- and postoperative CT scans, of 19 patients (average age 15 years, 6 months) with Lenke 1 curves (average 55 degrees , range 47-66 degrees ), all treated with anterior spinal fusion. Coronal and sagittal Cobb angles as well as vertebral rotation (Perdriolle and Nash-Moe) at the superior uninstrumented, superior instrumented, apical, inferior instrumented, and inferior uninstrumented vertebrae were measured on all films, and vertebral rotation was assessed on the CT scans by a previously described method. Additionally, several measures of thoracic torsion (as a proxy for vertebral rotation and overall deformity improvement) were assessed. These included the rib-vertebral angle difference (RVAD), apical rib hump prominence (RH), apical vertebral body-rib ratio (AVB-R), and apical rib spread difference (ARSD). RESULTS: The postoperative main thoracic curve averaged 26 degrees (range 16-39 degrees , 52% correction) and 29 degrees (range 22-40 degrees , 47% correction) at final follow-up. For apical derotation, the postoperative CT improved from -11.5 degrees to -6.6 degrees and correlated significantly with the Cobb main thoracic curves (42% correction, r = 0.48, P = 0.003). There was weakly positive, but statistically significant, correlation between the pre- and postoperative CT scans and the corresponding Perdriolle and Nash-Moe measures of segmental rotation (r = 0.32-0.40, all P < 0.0001). The RVAD demonstrated poor correlation with the main thoracic curve values and correction, Perdriolle rotation and correction, and CT rotation and correction (r = -0.22-0.37, all P > 0.20). The apical RH demonstrated good correlation with the main thoracic curve (r = 0.65, P < 0.0001), apical Perdriolle rotation (r = 0.57, P < 0.0001), and CT apical rotation (r = 0.53, P = 0.002). We also found moderate correlation between the AVB-R and the main thoracic Cobb, apical Perdriolle, and CT (r = 0.57, 0.59, and 0.49, respectively; all P < 0.005). Similar relationships were found with the ARSD (r = 0.51, 0.47, and 0.43, respectively; all P < 0.02). CONCLUSIONS: The RH, AVB-R, and the ARSD-measures of thoracic torsion-demonstrated moderate to good overall correlation with the main thoracic curve Cobb angles, apical Perdriolle rotation, and apical CT rotation. These should be useful as clinical measures for assessing three-dimensional deformity correction on plane radiographs, especially for the intraoperative evaluation of vertebral derotation and thoracic symmetry restoration.     

Visualisation of the brace effect on the spinal profile in idiopathic scoliosis

We studied the brace effect on the spinal profile in idiopathic scoliosis, using a MR procedure visualising the complete scoliotic spine in any vertical plane, while rotating it 180° on the longitudinal axis of the patient. Thirty-eight female patients (mean age, 14.5 years) were included in the study. Inclusion criteria were an idiopathic scoliosis, a Cobb angle greater than 20°, age of 10–17 years and bracing with a Chêneau brace. The brace effect was studied in 38 thoracic curves. The MR examinations were carried out in direct sequences, with and without brace. A reconstruction algorithm allows visualising the whole spine in vertical projections, with rotational steps of 2°, from –90° to 90°, referred to as MR animation. In various vertical MR projections, the changes of the curves were evaluated by measuring the Cobb angle. Additionally, a translation angle of the apical vertebra was determined, representing the lateral deviation of the apical vertebra from a defined midline. Testing the reproducibility of the Cobb angles, the standard deviation of the intra-individual differences was 1.7° and of the inter-individual differences, 2.1°. For the translation angles, the standard deviation of the intra-individual differences was 0.8° and of the inter-individual differences, 0.9°. With brace the mean Cobb angle of the thoracic curves was significantly reduced in the various vertical MR projections. The mean translation angle was also reduced. MR analysis showed that the brace effect is a translation process, straightening the profile of the scoliotic spine in all vertical planes. MR animation allows visualising the brace effect on the spine in scoliosis based on a 3D data set, without additional radiation exposure. It showed the straightening effect of the brace leading to a flattening of the sagittal spinal profile.     

青少年特发性脊柱侧凸胸廓对椎体轴向旋转影响的力学研究

目的 研究青少年特发性脊柱侧凸(AIS)在轴向负载条件下胸廓结构对椎体旋转的影响.方法 基于AIS患者CT扫描数据,构建包括胸廓和不包括胸廓两种三维有限元模型,进入ANSYS前处理器,设置边界条件和载荷,进入求解模块,进行不同载荷下轴向负载模拟计算,最后进入ANSYS后处理器,读取并分析脊柱侧凸不同椎体旋转角度大小和方向变化.结果 胸廓对胸椎结构性侧凸以上椎体的旋转角度大小和旋转方向有明确影响,对腰椎椎体和骶椎的旋转没有作用.胸廓对顶椎的轴向旋转角度仅有轻度影响,两种模型在不同载荷条件下,顶椎的旋转方向一致,角度大小比较差异无统计学意义.结论 AIS脊柱畸形造成椎体和胸廓结构的解剖学改变,会带来生物力学的相应改变.畸形的胸廓不能有效保护胸椎轴向旋转的稳定性.     

Evaluation of deformities and pulmonary function in adolescent idiopathic right thoracic scoliosis

Summary Seventy patients with adolescent idiopathic right thoracic scoliosis had full assessment of their pulmonary function using a computerised pulmonary function system. Their mean age at evaluation was 13.8 years. The following measurements were obtained from anteroposterior and lateral standing and antero-posterior supine bending radiographs: lateral curvature, vertebral rotation, kyphosis, maximum sterno-vertebral distance and apical rib-vertebral angles. Using the above measurements, the flexibility of curve, vertebral rotation and rib-vertebral angle asymmetry were calculated. Patients were classified into three groups on the basis of their predicted vital capacity, to determine whether radiological features of deformity can help identify patients with compromised pulmonary function. The mean Cobb angle and vertebral rotation for the 70 patients were 50° (range 35–100°) and 22° (range 1–44°) respectively. The mean flexibility of curve and vertebral rotation were 52% and 49% respectively. Mean thoracic kyphosis was 25%, ranging from -7 to 55%. Of the patients with Cobb angle less than 90%, 71% had vital capacity less than 80% of predicted values, and of these, 18% had marked compromise of vital capacity (less than 60% of predicted values). Mean values of Cobb angle, vertebral rotational flexibility, kyphosis, rib-vertebral angle asymmetry (in standing as well as supine bending radiographs) differed significantly between patients with more than 80% of predicted vital capacity and those with 60% or less of predicted values. Radiological features indicative of better pulmonary function were: rotational flexibility exceeding 55%, rib-vertebral angle asymmetry (standing) less than 25% and kyphosis greater than 15%. Two deformity parameters—that give a better prediction of pulmonary function than the widely used Cobb angle, vertebral rotational flexibility and rib-vertebral angle asymmetry—were identified in this study.     

The change in ratio of convex and concave lung volume in adolescent idiopathic scoliosis: a 3D CT scan based cross sectional study of effect of severity of curve on convex and concave lung volumes in 99 cases

To study the effect of the degree of scoliosis, degree of hypokyphosis/lordosis and rotation of apical vertebra on individual lung volume (measured with CT scan) in asymptomatic adolescent idiopathic scoliosis (AIS) patients. Individual (right and left) lung volume, angle of kyphosis and rotation of apical vertebra, were measured in 77 asymptomatic AIS patients having right thoracic curve, using modern computed tomography (CT) scan. To compare, lung volumes were measured in 22 normal persons (control group). The ratio of “right to left lung volume (convex to concave side)” was obtained and compared among these groups. With increased Cobb’s angle, ratio of convex to concave lung volume increased. For Cobb’s angle more than 40°, it was increased significantly (P = 0.0042). A significant degree of correlation was found between axial rotation angle of apical vertebra and right to left lung volume ratio (P = 0.0067, r = 0.271). A significant inverse correlation was found between the angle of kyphosis and right to left lung volume ratio, i.e., as the angle of kyphosis decreased the convex to concave lung volume ratio increased (P = 0.0109, r = −0.255). In asymptomatic, AIS patients, with increase in degree of curvature, and rotation of apical vertebra, the ratio of convex to concave side lung volume increases; indicating concave side lung volume is comparatively more affected (decreased) than convex side lung volume. On the other hand with decrease in the angle of kyphosis the convex to concave lung volume ratio increases indicating kyphotic angle has an inverse relation to convex to concave lung volume ratio. An erratum to this article can be found at     

Apical instrumentation alters the rotational correction in adolescent idiopathic scoliosis

The aim of this study was to retrospectively evaluate the effect of apical vertebral instrumentation in the axial plane in the surgical treatment of idiopathic scoliosis. Seventy-six consecutive patients with King type II idiopathic scoliosis, treated with posterior spinal instrumentation, were included in the study. The mean age of the patients was 14.5 years (range 10-18 years), and the mean follow-up was 49 (range 28-74) months. Preoperative radiological evaluation was performed with postero-anterior, lateral, traction and side-bending radiographs. Vertebral rotation was measured with a Perdriolle torsion meter. Patients were retrospectively divided into two groups according to the presence of apical vertebra instrumentation. Group 1 consisted of 43 patients in whom the upper and lower neutral and intermediate vertebrae of thoracic curves had been instrumented on the concave side. Group 2 consisted of 33 patients who had received instrumentation of the apical vertebra on the concave side in addition to the instrumentation configuration of group 1. Posterior fusion was added in all patients. Cobb and Perdriolle measurements were compared between the two groups preoperatively and at the last follow-up. Preoperative age and gender distribution, Cobb angle and rotational measurements, and correction ratios on side-bending films were similar in the two groups. Although the differences between the two groups in preoperative mean values of both Cobb angle and apical rotation were not statistically significant (P>0.05), mean values of apical rotation were significantly different postoperatively (P<0.05). At the same time, apical derotation ratios differed significantly between the two groups (P=0.000). We conclude that instrumentation of the apical vertebra provides better derotation at the apex.     

Measurement of vertebral rotation: Perdriolle versus Raimondi

Summary The measurement of vertebral rotation according to Perdriolle is widely used in the French-speaking and Anglo-American countries. Even in this measurement technique there may be a relatively high estimation error because of the not very accurate grading in steps of 5°. The measurement according to Raimondi seems to be easier to use and is more accurate, with 2° steps. The purpose of our study was to determine the technical error of both measuring methods. The apex vertebra of 40 curves on 20 anteroposterior (AP) radiographs were measured by using the Perdriolle torsion meter and the Regolo Raimondi. Interrater and intrarater reliability were computed. The thoracic Cobb angle was 43°, the lumbar Cobb angle 36°. The average rotation according to Perdriolle was 19.1° thoracic (SD 11.14), 12.7° lumbar (11.21). Measurement of vertebral rotation according to Raimondi showed an average rotation of 20.25° in the thoracic region (11.40) and 13.4° lumbar (10.92). The intrarater reliability was r=0.991 (Perdriolle) and r=0.997 (Raimondi). The average intrarater error was 1.025° in the Perdriolle measurement and 0.4° in the Raimondi measurement. Interrater error was on average 3.112° for the Perdriolle measurement and 3.630° for the Raimondi measurement. This shows that both methods are useful tools for the follow-up of vertebral rotation as projected on standard X-rays for the experienced clinicial. The Raimondi ruler is easier to use and is slightly more reliable.     

Mid-term effects of Cotrel-Dubousset instrumentation on the configuration of the spine and the thoracic cage in thoracic idiopathic scoliosis

Summary The effect of Cotrel-Dubousset instrumentation (CDI) on the three-dimensional spinal deformity in 24 consecutive patients with idiopathic scoliosis was investigated by posteroanterior and lateral radiographs and by computed tomography preoperatively, postoperatively, and at a mean follow-up of 3.2 years (range 2.0–5.3 years). At follow-up the mean Cobb angle was decreased by 73%, and the translation of the apical vertebra was significantly decreased by 33%. The sagittal contour was significantly improved with thoracic kyphosis T5–12 increased by 46% (6.9°) and lumbar lordosis L1–5 increased by 28% (10.3°) at follow-up. The sagittal diameter was significantly improved by 5 mm at follow-up. Although the vertebral rotation and the size of rib hump was improved postoperatively, this was followed by significant loss of correction, and at follow-up the vertebral rotation and the size of rib hump were not significantly better than preoperatively. The study indicates that while CDI improves the coronal and sagittal plane deformity permanently, the effect on vertetebral rotation and the rib hump deteriorates with time.     

Analysis of vertebral morphology in idiopathic scoliosis with use of magnetic resonance imaging and multiplanar reconstruction

BACKGROUND: Several studies have provided data on the vertebral morphology of normal spines, but there is a paucity of data on the vertebral morphology in patients with idiopathic scoliosis. METHODS: The morphology of the pedicles and bodies of 307 vertebrae as well as the distance between the pedicles and the dural sac (the epidural space) in twenty-six patients with right-sided thoracic idiopathic scoliosis were analyzed with use of magnetic resonance imaging and multiplanar reconstruction. RESULTS: A distinct vertebral asymmetry was found at the apical region of the thoracic curves, with significantly thinner pedicles on the concave side than on the convex side (p < 0.05). The degree of intravertebral deformity diminished farther away from the apex, with vertebral symmetry restored at the neutral level. In the thoracic spine, the transverse endosteal width of the apical pedicles measured between 2.3 mm and 3.2 mm on the concave side and between 3.9 mm and 4.4 mm on the convex side (p < 0.05). In the lumbar spine, the pedicle width measured between 4.6 mm at the cephalad part of the curve and 7.9 mm at the caudad part of the curve. The chord length and the pedicle length gradually increased from 34 mm and 18 mm, respectively, at the fourth thoracic vertebra to 51 mm and 25 mm, respectively, at the third lumbar vertebra. The transverse pedicle angle measured 15 in the cephalad aspect of the thoracic spine, decreased to 7 at the twelfth thoracic vertebra, and increased again to 16 at the fourth lumbar vertebra. The width of the epidural space was <1 mm at the thoracic apical vertebral levels and averaged 1 mm at the lumbar apical vertebral levels on the concave side, whereas it was between 3 mm and 5 mm on the convex side (p < 0.05). CONCLUSION: Idiopathic scoliosis is associated with distinctive intravertebral deformity, with smaller pedicles on the concave side and a shift of the dural sac toward the concavity.     

Harrington-Luque and Cotrel-Dubousset instrumentation for idiopathic thoracic scoliosis. A postoperative comparison using segmental radiologic analysis

This article reports a comparison of the Cotrel-Dubousset (CD) operation with the Harrington-Luque (HL) procedure for the treatment of adolescent idiopathic thoracic scoliosis. Thirty-nine patients were studied preoperatively and postoperatively using segmental radiologic measurements including Cobb angle, end-vertebra angles (EVAs), surgical flexibility index, vertebral rotation, displacement and tilt, convex and concave rib-vertebra angles (RVAs), and kyphosis and lordosis. Cotrel-Dubousset is not significantly different from HL with respect to Cobb angle (%), surgical flexibility index, apical vertebral displacement, apical vertebral rotation, apical rib-vertebra angles, kyphosis, and lordosis. It is significantly better than the HL with respect to the correction of vertebral displacement at T10-11; lower EVA of the thoracic curve; vertebral rotation mainly above the apex; convex RVAs above the apex; and concave RVAs at T10. The surgical correction of vertebral tilt above and below the apex of the thoracic curve is significantly related to the correction of convex and concave RVAs. The view that persistent deformity of ribs is a factor needing surgical correction in some patients with adolescent idiopathic thoracic scoliosis having posterior instrumentation and fusion needs further evaluation.