Pathologic mechanism of experimental scoliosis in pinealectomized chickens

STUDY DESIGN: This study was designed to investigate the pathologic mechanisms of idiopathic scoliosis using experimentally induced scoliosis in chickens. OBJECTIVE: To understand the process of producing a scoliotic deformity in pinealectomized chickens. SUMMARY OF BACKGROUND DATA: Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. Pinealectomized chickens are an important animal model for the study of idiopathic scoliosis. METHODS: In this study, 40 chickens were divided into two groups; 20 chickens treated with pinealectomy and 20 with a sham operation as control subjects on the second after hatching. The chickens in both groups then were killed at intervals ranging from 1 to 20 weeks after surgery. Their spines were examined visually and radiologically for the presence of a scoliotic curve and vertebral deformities. RESULTS: Rotational lordoscoliosis developed in pinealectomized chickens. The chickens with severe scoliosis were characterized by apically wedge-shaped vertebrae. In contrast, no scoliosis with any vertebral deformity developed in any of the chickens that received a sham operation. CONCLUSIONS: Because there normally is evidence of lordosis in the thoracic spine of chickens, the rotational instability of the spine induced by pinealectomy may produce a scoliotic deformity as a secondary phenomenon. Pinealectomy in chickens consistently produces scoliosis with anatomic characteristics similar to those of human idiopathic scoliosis. The authors believe that disturbance of the equilibrium and the posture mechanism associated with a defect in melatonin synthesis after pinealectomy may promote the development of rotational lordoscoliosis.     

Morphometric analysis of thoracic and lumbar vertebrae in idiopathic scoliosis

STUDY DESIGN: Prospective study on the morphometry of 337 pedicles in 29 patients with idiopathic scoliosis. OBJECTIVES: To analyze by means of computed tomographic scans the vertebral morphometry in idiopathic scoliosis treated by pedicle screw instrumentation. SUMMARY OF BACKGROUND DATA: Although several studies exist on the vertebrae's morphometry in normal spines, little is known concerning the morphometry of scoliotic vertebrae. METHODS: The pedicles' morphometry between T5 and L4 was analyzed by computed tomographic scans in 29 surgically treated patients with idiopathic right thoracic scoliosis. Measurements included chord length, endosteal transverse pedicle width, transverse pedicle angle, and pedicle length. RESULTS: The endosteal transverse pedicle width was significantly smaller (P < 0.05) on the concavity in the apical region of the thoracic spine and measured between 2.5 and 4.2 mm in the middle thoracic spine (T5-T9) and between 4.2 and 5.9 mm in the lower thoracic spine (T10-T12). In the lumbar spine, the width varied between 4.8 and 9.5 mm without significant differences between the concave and convex sides (P > 0.05). The chord length was shortest at T5, measuring 37 mm and increased gradually to 50 mm at L3 with significantly larger dimensions in male patients and on the concavity of the apical region in the thoracic spine (P < 0.05). The pedicle length varied minimally, with a range of between 20 and 22 mm, and was relatively consistent throughout the thoracic and lumbar spine. The transverse pedicle angle varied between 6 degrees in the lower thoracic spine and 12 degrees in the upper thoracic and lower lumbar spine. CONCLUSION: The morphometry in scoliotic vertebrae is substantially different from that of vertebrae in normal spines, with an asymmetrical intravertebral deformity shown in scoliotic vertebrae. Pedicle screw instrumentation on the concavity in the apical region of thoracic curves appears critical because of the small endosteal pedicle width.     

The effect of pedicle screw insertion through the neurocentral cartilage on the growth of immature canine vertebra

Objective: To explore the influence of pedicle screw insertion through the neurocentral cartilage (NCC) on the development of vertebrae and spinal canal in an animal experiment. Methods: Sixteen dogs were randomly assigned to three groups: in group 1, posterior muscles at the surgery site were dissected; in group 2, the pedicles were drilled through the NCC by screws; in group 3, screws were placed in the pedicles through the NCC. Vertebrae of T8, T10, T12, L2, L4 and L6 were studied with the average data of the adjacent two vertebrae serving as controls. Spiral computerized tomography (CT) was used to assess the morphologic parameters of studied vertebrae and their controls. Measurements were made by an independent radiologist on the first post‐operative day and 3 months after operation. Paired Student's t‐tests of studied vertebrae and their controls were performed to evaluate the effect of pedicle screw insertion. Results: In group 3, 3 months after operation the area, transverse diameter and anterior‐posterior diameter of the vertebral canal and length of pedicle of studied vertebrae were significantly smaller than those of control vertebrae (P < 0.05). There were no significant differences in morphologic parameters between the studied vertebrae and the control vertebrae in groups 1 and 2 (P > 0.05). Conclusion: (i) Pedicle screw placement has a significant impact on the growth of the canine vertebra canal, and may lead to iatrogenic spinal stenosis, but their placement has no significant effect on the vertebral bodies; and (ii) the NCC can repair itself automatically. Drilling pedicle bone through the NCC with a screw and then removing the screw has no obvious impact on the growth of vertebrae.     

The sagittal curvature of spine in idiopathic scoliosis--its morphological features and the correlation among sagittal and frontal curvatures and rotation of apical vertebra

The change in sagittal curvature especially in thoracic kyphosis of idiopathic scoliosis patients, was analyzed and discussed. Those patients who had scoliotic deformity with typical vertebral rotation only in thoracic spine (ST group), showed significant decrease compared to normal person in thoracic kyphosis, but no difference in lumbar lordosis. Those suffering from scoliotic deformities with typical vertebral rotation in thoracic and lumbar spine showed a significant decrease in thoracic kyphosis and an increase in lumbar lordosis. However those changes in sagittal curvature were not found in FT group patients, who had scoliotic deformity without vertebral rotation. In conclusion, it is not the frontal curvature but the vertebral rotation which influenced the sagittal curvature of spine in patients with idiopathic scoliosis.     

Segmental pedicle screwing for idiopathic scoliosis using computer-assisted surgery

STUDY DESIGN: Retrospective clinical study. OBJECTIVES: To evaluate the accuracy of computer-assisted surgery for idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Segmental pedicle screw fixation has been proven to enable enhanced correction of scoliotic deformities. However, both neurovascular and visceral structures are at potential risk from screw misplacement due to pedicle drift. No reports exist on the accuracy and benefits of computer-assisted surgery for pedicle screwing in scoliosis surgery. METHODS: A total of 40 consecutive patients with idiopathic scoliosis were evaluated. Postoperative computed tomography was assessed for the accuracy of pedicle screw placement in 20 cases treated without a navigation system and 20 cases with a computed tomography-based navigation system. Correlations between registered levels and pedicle perforation were investigated. RESULTS: Pedicle violation was observed in 28.0% of the control group and 11.4% of the navigation group, with significant differences. No screw misplacements at the registered levels were seen, and the longer the distance between the registered level and level of screw insertion, the higher the rate of pedicle violation. No intraoperative complications caused by pedicle perforation occurred. CONCLUSIONS: In the navigation group, a tendency to lateral perforation at the concave side and medial perforation at the convex side was noted, like in the control group. Use of the navigation system significantly reduced the screw misplacement rate for rotated vertebrae as compared with the control group. Separate registration is recommended for rotated vertebrae when possible.     

The changes of relative position of the thoracic aorta after anterior or posterior instrumentation of type I Lenke curve in adolescent idiopathic thoracic scoliosis

The risk of impingement of the aorta associated with thoracic vertebral screw or pedicle screw instrumentation in the treatment of thoracic scoliosis has been an important concern. To understand this phenomenon more systematically, the relative position of the aorta with reference to the thoracic vertebrae in right thoracic adolescent idiopathic scoliosis (AIS) following anterior and posterior spinal instrumentation was analyzed in detail quantitatively; 34 patients underwent anterior (n = 14) or posterior (n = 20) spinal instrumentation were recruited in the present study. The relative position of the thoracic aorta, vertebral rotation, apical vertebral translation and thoracic kyphosis were measured from pre- and post-operative CT images from T5 to T12. The aorta was found to shift antero-medially in the anterior instrumentation group but not in the posterior spinal instrumentation group. It is likely that the disc removal, soft tissue release and spontaneous vertebral derotation of the scoliosis could account for the antero-medial shifting of the aorta. By the shifting, the space for contralateral screw penetration was reduced.     

青少年特发性脊柱侧凸胸椎形态学的MRI测量及临床意义

目的 通过磁共振成像(MRI)观察青少年特发性脊柱侧凸(AIS)和正常同年龄组青少年胸椎的形态学差异,探讨其临床意义.方法 胸椎轻度侧凸(MS)组患者10例(Cobb角15°～39°),胸椎中度侧凸(SS)组患者10例(Cobb角40°～75°).另选健康青少年10名作为对照(非侧凸组).所有研究对象均为女性,年龄13～14岁.用1.5 T磁共振扫描仪(Sonata,Siemens,Erlanger,德国)对所有研究对象进行全脊柱矢状面扫描,在图像工作站(Easy Vision,Philips Medical Systems,Best,荷兰)上重建脊柱矢状面图像,测量每个胸椎椎体前壁高度,后壁高度,棘突间高度,在横截面测量椎体横径长度,并进行对比分析.结果 椎体前后高度、宽度从T1到T12逐渐增加,并呈线性分布,脊柱侧凸组椎体高度普遍>正常同年龄非侧凸组患者.脊柱侧凸组患者椎体高度横径比值以及脊椎前后高度比值均>无侧凸组.胸椎侧凸顶椎区T6～T9椎体前方高度、椎体高度横径比值以及脊椎前后高度比值,脊柱侧凸组明显>非侧凸组,差异均有统计学意义(P<0.05).结论 AIS胸椎侧凸女性患者胸椎顶椎区存在显著的脊柱生长模式异常,与正常胸椎相比AIS的胸椎更高、并显得更为瘦长.     

The anatomical relationship between the aorta and the thoracic vertebral bodies and its importance in the placement of the screw in thoracoscopic correction of Scoliosis

Thoracoscopically-assisted anterior spinal instrumentation is being used widely to treat adolescent idiopathic scoliosis (AIS). Recent studies have showed that screws placed thoracoscopically could counter the aorta or entrance into the spinal canal. There are a few studies defining the anatomic landmarks to identify the relationship between the aorta and the thoracic vertebral body using quantitative measurement for the sake of safe placement of thoracoscopic vertebral screw in anterior correction for AIS. The CT scanning from T4 to T12 in 64 control subjects and 30 AIS patients from mainland China were analyzed manually. Parameters to be measured included the angle for safety screw placement (α), the angle of the aorta relative to the vertebral body (β), the distance from the line between the left and the right rib heads to the anterior wall of the vertebral canal (a), the distance from the left rib head to posterior wall of the aorta (b), the vertebral body transverse diameter (c) and vertebral rotation (γ). No significant differences were found between the groups with respect to age or sex. Compared with the control group, α angle from T7 to T10, β angle from T5 to T10 and b value at T9, T10 were significantly lower in the scoliotic group. The a value was significantly lower in the scoliotic group. The c value showed no significant difference between the two groups. In conclusion, to place the thoracoscopic vertebral screw safely, at the cephalad thoracic spine (T4–T6), the maximum ventral excursion angle should decrease gradually from 20° to 5°, the entry-point of the screw should be close to the rib head. For apical vertebrae (T7–T9), the maximum ventral excursion angle increased gradually from 5° to 12°. At the caudal thoracic spine (T10–T12), the maximum ventral excursion angle increased, the entry-point should shift 3∼5 mm ventrally.     

特发性胸椎侧凸前路矫形对胸主动脉偏移的影响及意义

目的 比较青少年特发性胸椎右侧凸患者前路开放小切口矫形手术和后路矫形手术对胸主动脉偏移的影响及其意义.方法 29例青少年特发性胸椎右侧凸患者分为两组.A组14例患者行开放小切口前路矫形术,男1例,女13例,平均14.3岁,胸弯Cobb角平均44.9°.B组15例患者行后路钉钩联合矫形术,男3例,女12例,平均14.2岁,胸弯Cobb角平均46.4°.两组患者手术前后均行胸椎T5～T12节段CT扫描,在每个节段测量右侧肋骨头至主动脉后壁的切线与双侧肋骨头连线的夹角(α)、椎管前缘中点与主动脉中心连线和双侧肋骨头连线的夹角(β)、椎体旋转(γ)、主动脉与椎体间距离(a)以及与左侧肋骨头前缘的垂直距离(b)并进行比较.将胸主动脉偏移与侧凸的三维矫形进行相关性分析明确胸主动脉偏移的原因.结果 A组患者手术后置钉安全角α、主动脉相对椎管前缘旋转角β较术前增大,在T8,T9差异有显著性(P＜0.05);椎体旋转γ角减小,在T8,T9差异有显著性(P＜0.05);主动脉与椎体间距离a减小,主动脉后壁与右侧肋骨头间距离b增大,两者和术前相比在T9有显著性差异(P＜0.05).B组手术前后椎体旋转及主动脉与相邻椎体的解剖关系无明显变化.A组α角、β角、b值增加量与γ角减小量呈明显相关性(P＜0.01);a值减少量与β角增加量具有良好相关性(P＜0.05);在顶椎区α角、β角、b值的增加量与顶椎偏移减少量、a值减少量与T5～T12后凸增加量明显相关(P＜0.01).结论 特发性胸椎右侧凸患者行小切口前路矫形术后胸主动脉相对椎体向前方偏移并靠近椎体.发生主动脉偏移的原因包括主动脉松解、椎体去旋转、冠状面和矢状面矫形.     

Porcine model of early onset scoliosis based on animal growth created with posterior mini-invasive spinal offset tethering A preliminary report

Several models of scoliosis were developed in the past 10 years. In most of them, deformations are induced in old animals and required long time observation period and a chest wall ligation ± resection. The purpose of the study was to create a scoliosis model with a size similar to an early onset scoliosis and an important growth potential without chest wall injuring. An original offset implant was fixed posteriorly and connected with a cable in seven (6 + 1 control) one-month-old Landrace pigs. The mean initial spinal length (T1-S1) was 25 cm and the mean weight was 9 kg. After 2 months observation, spinal deformities were assessed with a three dimension stereographic analysis. In four animals, the cable was sectioned and the deformities followed-up for next 2 months. No post-operative complication was observed. Mean weight growth was 10 kg/month and mean spine lengthening (T1-S1) was 7 cm/month. In 2 months, we obtained structural scoliotic curves with vertebral and disk wedging which were maximal at the apex of the curve. Mean frontal and sagittal Cobb angles was 45°. Chest wall associated deformities were similar to those observed in scoliotic deformities and were correlated to spinal deformities (p = 0.03). The cable section resulted in a partial curve regression influenced by disk elasticity and could probably be influenced by gravity loads (Decrease of the Cobb angle of 30% in the sagittal plane and 45% in the frontal plane). According to the results, the model creates a structural scoliosis and chest wall deformity that is similar to an early onset scoliosis. The spinal deformities were obtained quickly, and were consistent between animals in term of amount and characteristic.     

Observations on the growth of the adolescent spine

We have measured the increase in height and width of the vertebral bodies and expressed them as percentages of the total growth in children aged 10 to 17 years. The first group, 10 boys and 10 girls, each had a single thoracic adolescent idiopathic scoliosis while the second group, 10 girls, each had a single lumbar adolescent idiopathic scoliosis. No significant differences were found between the growth increments and spinal dimensions of the vertebral bodies involved in the scoliotic curve and those vertebrae outside the curve in the same patient. The vertebrae were more slender in girls than in boys.     

Congenital scoliosis

Congenital scoliosis, those scoliotic deformities owing to congenitally anomalous vertebrae, was for many years the least understood of the major causes of scoliosis. This was a result of the wide variety of anomalies, the variable natural history, the poor results of bracing, and the meager correction obtained at surgery. The past 20 years have, however, brought major understandings about the natural history and far better programs of treatment. This article provides a summary of these advances for the reader and defines the current state of understanding.     

One-stage and posterior approach for correction of moderate to severe scoliosis in adolescents associated with Chiari I malformation: is a prior suboccipital decompression always necessary?

Priority of neurological decompression was regarded as necessary for scoliosis patients associated with Chiari I malformation in order to decrease the risk of spinal cord injury from scoliosis surgery. We report a retrospective series of scoliosis associated with Chiari I malformation in 13 adolescent patients and explore the effectiveness and safety of posterior scoliosis correction without suboccipital decompression. One-stage posterior approach total vertebral column resection was performed in seven patients with scoliosis or kyphosis curve >90° (average 100.1° scoliotic and 97.1° kyphotic curves) or presented with apparent neurological deficits, whereas the other six patients underwent posterior pedicle screw instrumentation for correction of spinal deformity alone (average 77.3° scoliotic and 44.0° kyphotic curves). The apex of the scoliosis curve was located at T7–T12. Mean operating time and intraoperative hemorrhage was 463 min and 5,190 ml in patients undergoing total vertebral column resection, with average correction rate of scoliosis and kyphosis being 63.3 and 71.1%, respectively. Mean operating time and intraoperative hemorrhage in patients undergoing instrumentation alone was 246 min and 1,450 ml, with the average correction rate of scoliosis and kyphosis being 60.8 and 53.4%, respectively. The mean follow-up duration was 32.2 months. No iatrogenic neurological deterioration had been encountered during the operation procedure and follow-up. After vertebral column resection, neurological dysfunctions such as relaxation of anal sphincter or hypermyotonia that occurred in three patients preoperatively improved gradually. In summary, suboccipital decompression prior to correction of spine deformity may not always be necessary for adolescent patients with scoliosis associated with Chiari I malformation. Particularly in patients with a severe and rigid curve or with significant neurological deficits, posterior approach total vertebral column resection is likely a good option, which could not only result in satisfactory correction of deformity, but also decrease the risk of neurological injury secondary to surgical intervention by shortening spine and reducing the tension of spinal cord.     

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

STUDY DESIGN: The axial length of the vertebral canal and the anterior aspect of the vertebrae were measured in 36 skeletons, 15 with probable idiopathic scoliosis. OBJECTIVES: To compare the discrepancy in length of the vertebral canal and the anterior spinal column in skeletons having probable idiopathic scoliosis with the degree of deformity. SUMMARY AND BACKGROUND DATA: In idiopathic scoliosis, the vertebral bodies rotate toward the convexity of the curve, whereas the vertebral canal tends to retain a midline position. The vertebral canal therefore will be relatively short. The degree of shortening has not been described previously, nor its relation with the degree of deformity. METHODS: The axial length of the vertebral canal and the anterior aspect of the vertebral bodies were measured in 36 skeletons: 8 with normal spines, 13 with kyphosis, and 15 with probable idiopathic scoliosis. The relative shortening in the scoliotic spines was correlated with the Cobb angle and the degree of rotation. RESULTS: No significant difference in length was found between the vertebral canal and the vertebral column in the normal spines. The kyphotic spines had canals significantly longer than the vertebral length (P<0.025). All but one of the scoliotic spines had short vertebral canals (P<0.01). The degree of discrepancy was related to the Cobb angle (r = -0.50; P< 0.05), and particularly to the degree of rotation (r = -0.88; P< 0.001). CONCLUSIONS: The findings have surgical and etiologic implications. The results are consistent with a conceivable hypothesis that in some patients with idiopathic scoliosis, there may be impaired growth in the length of the spinal cord, the posterior elements are tethered, and as the vertebral bodies continue to grow, they become lordotic and then rotate.     

Rib cage surgery for the treatment of scoliosis: a biomechanical study of correction mechanisms.

Rib shortening or lengthening are surgical options that are used to address the cosmetic rib cage deformity in scoliosis, but can also alter the equilibrium of forces acting on the spine, thus possibly counteracting in a mechanical way the scoliotic process and correcting the spinal deformities. Although rib surgeries have been successful in animal models, they have not gained wide clinical acceptance for mechanical correction of scoliosis due to the lack of understanding of the complex mechanisms of action involved during and after the operation. The objective of this study was to assess the biomechanical action of different surgical approaches on the rib cage for the treatment of scoliosis using a patient-specific finite element model of the spine and rib cage. Several unilateral and bilateral rib shortening/lengthening procedures were tested at different locations on the ribs (convex/concave side of the thoracic curvature; at the costo-transverse/costo-chondral joint; 20 and 40 mm adjustments). A biomechanical analysis was performed to assess the resulting geometry and load patterns in ribs, costo-vertebral articulations and vertebrae. Only slight immediate geometric variations were obtained. However, concave side rib shortening and convex side rib lengthening induced important loads on vertebral endplates that may lead to possible scoliotic spine correction depending on the remaining growth potential. Convex side rib shortening and concave side rib lengthening produced mostly cosmetic rib cage correction, but generated inappropriate loads on the vertebral endplates that could aggravate vertebral wedging. This study supports the concept of using concave side rib shortening or convex side rib lengthening as useful means to induce correction of the spinal scoliotic deformity during growth, though the effects of growth modulation from induced loads must be addressed in more detail to prove the usefulness of rib shortening/lengthening techniques.     

Demonstration of vertebral and disc mechanical torsion in adolescent idiopathic scoliosis using three-dimensional MR imaging

This study was designed to demonstrate and measure mechanical torsion in patients with adolescent idiopathic scoliosis using three-dimensional magnetic resonance (MR) imaging. Ten patients with adolescent idiopathic scoliosis were imaged with three-dimensional MR imaging, and the data post-processed through multiplanar reconstruction to produce images angled through individual endplates. Transverse rotation was measured at each endplate and these measurements used to calculate the amount of vertebral and disc mechanical torsion present. A test object was imaged in order to validate the measurement technique. Mechanical torsion was demonstrated within the vertebral bodies and discs of the imaged subjects, with vertebral mechanical torsion contributing on average 45% of the overall transverse plane deformity. It is concluded that deformation occurs in the transverse plane within the vertebrae and discs of subjects with idiopathic scoliosis, and a significant proportion of the rotation present in the scoliotic spine occurs as a result of plastic deformation within the vertebrae themselves. We believe that this is the first systematic demonstration of mechanical torsion in idiopathic scoliosis.     

Morphology of scoliosis: three-dimensional evolution

The clinical examination of the scoliotic child's profile shows that it does not correspond to the physiological curvatures. This three-dimensional study of scoliosis shows evidence of the existence of three components, frontal, sagittal, and axial. Each generates a pathological displacement of the vertebrae maximal at the apical vertebral level. Because of rotation, in order to analyze each of the components, radiographs must be taken along the frontal or sagittal plane of the vertebrae. A comparative study of the sagittal and frontal components during progression of scoliosis indicates that the apical vertebrae are displaced not only laterally but also forward and then backward. The apical vertebrae are situated anteriorly with respect to the end vertebrae. If the scoliotic curves progress, the apical vertebrae eventually become displaced backward. During this displacement at a given moment they are situated in the frontal plane of the child at the same level as the upper end vertebra; then they come to lie behind this if the scoliosis continues to progress. This explains why, when observed from the side, the appearance changes and passes through three successive stages, lordosis, flat back, and kyphosis.