Treatment of idiopathic scoliosis with CD-instrumentation: Lumbar pedicle screws versus laminar hooks in 66 patients

We studied whether the pedicle screw is better than laminar hooks for fixation of the lumbar spine in the treatment of idiopathic scoliosis. 66 consecutive patients with idiopathic scoliosis (King I and II) were studied retrospectively. Group S included 33 patients (25 females) treated with pedicle screws. Their mean age at operation was 17 (13-54) years. Group H included 33 patients (30 females) treated exclusively with hooks. Their mean age at operation was 16 (11-40) years. The preoperative mean angles of the thoracic curve in group S was 66 (42-115)°, and in group H 65 (42-121)°. The lumbar curve averaged 46 (20-85)° in group H and 53 (33-86)° in group S. All patients were fused only posteriorly with Cotrel-Dubousset instrumentation and an autogenic bone graft. The mean follow-up time was 4 (2-7) years. Mean correction of the thoracic curve was 45% in group S and 50% in group H. The lumbar curve was corrected by 50% in group S and 51% in group H. Loss of correction of the thoracic curve occurred in 5% in group S and 6% in group H and of the lumbar curve in 3% in group S and 10% in group H (p = 0.04). Group S better maintained the correction of the lateral tilt of the uninstrumented segment adjacent to the fusion (p = 0.04). Derotation, according to Perdriolle, in the distal segment adjacent to the fusion was 6% in group S and 2% in group H. We found no difference between correction of the thoracic and lumbar curves using pedicle screws and laminar hooks in the lumbar spine. Pedicle screws better maintained the correction of the lumbar curve and the lateral tilt in the distal segment adjacent to fusion.     

Treatment of idiopathic scoliosis with CD-instrumentation: lumbar pedicle screws versus laminar hooks in 66 patients

We studied whether the pedicle screw is better than laminar hooks for fixation of the lumbar spine in the treatment of idiopathic scoliosis. 66 consecutive patients with idiopathic scoliosis (King I and II) were studied retrospectively. Group S included 33 patients (25 females) treated with pedicle screws. Their mean age at operation was 17 (13-54) years. Group H included 33 patients (30 females) treated exclusively with hooks. Their mean age at operation was 16 (1140) years. The preoperative mean angles of the thoracic curve in group S was 66 (42.115) degrees, and in group H 65 (42-121) degrees. The lumbar curve averaged 46 (20-85) degrees in group H and 53 (33-86) degrees in group S. All patients were fused only posteriorly with Cotrel-Dubousset instrumentation and an autogenic bone graft. The mean follow-up time was 4 (2-7) years. Mean correction of the thoracic curve was 45% in group S and 50% in group H. The lumbar curve was corrected by 50% in group S and 51% in group H. Loss of correction of the thoracic curve occurred in 5% in group S and 6% in group H and of the lumbar curve in 3% in group S and 10% in group H (p = 0.04). Group S better maintained the correction of the lateral tilt of the uninstrumented segment adjacent to the fusion (p = 0.04). Derotation, according to Perdriolle, in the distal segment adjacent to the fusion was 6% in group S and 2% in group H. We found no difference between correction of the thoracic and lumbar curves using pedicle screws and laminar hooks in the lumbar spine. Pedicle screws better maintained the correction of the lumbar curve and the lateral tilt in the distal segment adjacent to fusion.     

Comparative analysis of pedicle screw and hook instrumentation in posterior correction and fusion of idiopathic thoracic scoliosis

Posterior correction and fusion with segmental hook instrumentation represent the gold standard in the surgical treatment of progressive idiopathic thoracic scoliosis. However, there is a debate over whether pedicle screws are safe in scoliosis surgery and whether their usage might enable a better curve correction and a shorter fusion length. The details of curve correction, fusion length and complication rate of 99 patients with idiopathic thoracic scoliosis treated with either hook or pedicle screw instrumentation were analyzed. Forty-nine patients had been operated with the Cotrel-Dubousset system using hooks exclusively ("hook group"). Fifty patients had been operated with either a combination of pedicle screws in the lumbar and lower thoracic and hooks in the upper thoracic spine or exclusive pedicle screw instrumentation using the Münster Posterior Double Rod System ("screw group"). The preoperative Cobb angle averaged 61.3 degrees (range 40 degrees-84 degrees ) in the hook group and 62.5 degrees (range 43 degrees-94 degrees ) in the screw group. Average primary curve correction was 51.7% in the hook group and 55.8% in the screw group ( P>0.05). However, at follow-up (2-12 years later) primary curve correction was significantly greater ( P=0.001) in the screw group (at 50.1%) compared to the hook group (at 41.1%). Secondary lumbar curve correction was significantly greater ( P=0.04) in the screw group (54.9%) compared to the hook group (46.9%). Correction of the apical vertebral rotation according to Perdriolle was minimal in both groups. Apical vertebral translation was corrected by 42.0% in the hook group and 55.6% in the screw group ( P=0.008). Correction of the tilt of the lowest instrumented vertebra averaged 48.1% in the hook group and 66.2% in the screw group ( P=0.0004). There were no differences concerning correction of the sagittal plane deformity between the two groups. Fusion length was, on average, 0.6 segments shorter in the screw group compared to the hook group ( P=0.03). With pedicle screws, the lowest instrumented vertebra was usually one below the lower end vertebra, whereas in the hook group it was between one and two vertebrae below the lower end vertebra. Both operative time and intraoperative blood loss were significantly higher in the hook group ( P<0.0001). One pedicle screw at T5 was exchanged due to the direct proximity to the aorta. There were no neurologic complications related to pedicle screw instrumentation. Pedicle screw instrumentation alone or in combination with proximal hook instrumentation offers a significantly better primary and secondary curve correction in idiopathic thoracic scoliosis and enables a significantly shorter fusion length.     

内固定方式对青少年特发性脊柱侧凸选择性胸椎融合矢状面重建的影响

目的 探讨胸弯型青少年特发性脊柱侧凸患者行后路选择性胸椎融合术时采用不同内固定方式对胸椎矢状面形态及远端腰椎代偿模式的影响.方法 行胸弯后路矫形内同定术且有2年以上(2～3年)完整随访资料的lenke 1、2型青少年特发性脊柱侧凸患者51例,按内固定方式分为A组(全钩组)、B组(钩钉混合组)和C组(全钉组).测量术前及术后随访的胸弯Cobb角、腰弯Cobb角、胸椎后凸角、腰椎前凸角、远端交界性后凸、胸腰段交界性后凸及C7铅垂线偏离S1后上缘的距离.结果 三组患者主弯矫正率均大于60%,继发弯也获得较满意的自发性矫正.三组患者术前及随访中腰椎前凸角、C7铅垂线偏离S1后上缘的距离均保持正常.随访2年时,A组远端交界性后凸、胸椎后凸角、胸腰段交界性后凸分别达3.6°、23.0°、6.4°,其中远端交界性后凸与术前比较差异有统计学意义(P<0.05).B组和C组各项指标与术前比较差异均无统计学意义.结论 全钩型同定可以获得良好的冠状面矫形,且在随访中能保持腰椎前凸和欠状面平衡.但钩的固定不如椎弓根螺钉牢固,全钩型固定患者胸椎后凸角有增大趋势,胸腰椎交界区有失代偿的可能.     

Pullout strength of pedicle screws versus pedicle and laminar hooks in the thoracic spine

While the biomechanical properties of pedicle screws have proven to be superior in the lumbar spine, little is known concerning pullout strength of pedicle screws in comparison to hooks in the thoracic spine. In vitro biomechanical pullout testing was performed to evaluate the axial pullout strength of pedicle screws versus pedicle and laminar hooks in the thoracic spine with regard to surgical correction techniques in scoliosis. Nine human cadaveric thoracic spines were harvested and disarticulated. To simulate a typical posterior segmental scoliosis instrumentation, standard pedicle hooks were used between T4 and T8 and supralaminar hooks between T9 and T12 and tested against pedicle screws. The pedicle screws were loaded strictly longitudinal to their axis; the hooks were loaded perpendicular to the intended rod direction. In total, 90 pullout tests were performed. Average pullout strength of the pedicle screws was significantly higher than in the hook group (T4-T8: 531 N versus 321 N, T9-T12: 807 N versus 600 N, p < 0.05). Both screw diameter and the bone mineral density (BMD) had significant influence on the pullout strength in the screw group. For scoliosis correction, pedicle screws might be beneficial, especially for rigid thoracic curves, since they are significantly more resistant to axial pullout than both pedicle and laminar hooks.     

Correlative analysis of the results of surgical treatment of thoracolumbar injuries with long Texas Scottish rite hospital construct: is the use of pedicle screws versus hooks advantageous in the lumbar spine?

This is a prospective, randomized study to compare the efficacy of two similar "long-segment" Texas Scottish Rite Hospital instrumentations with the use of hooks in the thoracic spine and pedicle screws versus laminar hook claw in the lumbar spine for thoracolumbar A3, B, and C injuries. Forty consecutive patients with such thoracolumbar fractures (T11-L1) associated with spinal canal encroachment underwent early operative postural reduction and stabilization. The patients were randomly sampled into two groups: Twenty patients received hooks in "claw configuration" in both the thoracic and the lumbar spine (group A), and 20 patients received hooks in the thoracic vertebrae and pedicle screws in the lumbar vertebrae (group B). Pre- and postoperative plain roentgenograms and computed tomography scans were used to evaluate any changes in Gardner post-traumatic kyphotic deformity, anterior and posterior vertebral body height at the fracture level, and spinal canal clearance (SCC). All patients were followed for an average period of 52 months (range 42-71 months). The correction of anterior vertebral body height was significantly more (P < 0.01) in the spines of group B (33%) than in group A (16%), with a subsequent 11% loss of correction at the latest evaluation in group A and no loss of correction in group B. There were no significant differences in the changes of posterior vertebral body height and Gardner angle between the two groups. The SCC was significantly more (P < 0.05) immediately postoperatively in the spine of group B (32%) than in group A (19%). In the latest evaluation, there was a 9% loss of the immediately postoperatively achieved SCC in group A, while SCC was furthermore increased at 10.5% in group B. All patients with incomplete neurologic lesions in groups A and B were postoperatively improved at 1.1 and 1.7 levels, respectively. There were two hook dislodgements in the thoracic spine, one in each group, while there was no screw failure in group B. There was neither pseudarthrosis nor neurologic deterioration following surgery. Visual Analog Pain Scale and Short Form-36 scores were equally improved and did not differ between the two groups. The use of pedicle screws in the lumbar spine to stabilize the lowermost end of a long rigid construct applied for A3, B, and C thoracolumbar injuries was advantageous when compared with that using hook claws in the lumbar spine because the constructs with screws restored and maintained the fractured anterior vertebral body height better than the hooks without subsequent loss of correction and safeguarded postoperatively a continuous SCC at the injury level.     

2- to 4-year outcome of dorsal double rod instrumentation spondylodesis in idiopathic scoliosis]

INTRODUCTION: In order to evaluate the results of posterior correction and fusion using the Münster Posterior Doublerod-System (MPDS) 48 patients with idiopathic scoliosis were studied prospectively. METHODS: All patients underwent clinical examination and radiological analysis of the frontal and sagittal plane preoperatively, postoperatively and at follow-up (2-4 years). Pedicle screws were used at the lumbar and thoracolumbar spine exclusively. RESULTS: The preoperative average Cobb angle was 61.4 degrees with an average flexibility of 36.8% to 38.8 degrees. The average postoperative Cobb angle was 24.8 degrees (59.6%) with an average loss of correction of 2.6 degrees Cobb angle (3.6%). Due to the use of thoracolumbar and lumbar pedicle screws instrumented fusion could be stopped at the lower endvertebra in 71%. Patients in whom only pedicle screws had been used improved correction of frontal plane could be shown compared to combined instrumentations with hooks and screws. CONCLUSION: The posterior instrumentation guarantees primary stability with good results of correction and allows brace free treatment postoperatively. The postoperative correction compared to the results at follow-up proves the stability of the instrumentation largely. The results of mainly pedicle screw based instrumentations verify that an improved correction can be achieved. In most cases fusion levels end at the lower end vertebra and therefore are shorter compared to instrumentation's based on hooks only.     

Dorsale operative Korrektur der idiopathischen Skoliose

Posterior correction and fusion of scoliosis with multisegmental instrumentation systems was developed by Cotrel-Dubousset in the 1980s. Initially correction and instrumentation was performed using hooks only. Later pedicle screws were implemented first for the lumbar and then for the thoracic spine. Nowadays instrumentation based on pedicle screws only is well established for posterior scoliosis surgery. Biomechanical studies demonstrated higher pull-out forces for pedicle than for hook constructs. In clinical studies several authors reported better Cobb angle correction of the primary and the secondary curves and less loss of correction in pedicle screw versus hook instrumentations. Furthermore, pedicle screw instrumentation allows fewer segments to be fused, especially caudally, and thus saving mobile segments. In most of these publications there were no differences in operation time, blood loss and complication rates. In summary, there is better curve correction without an increased risk using multisegmental pedicle screw instrumentation in modern posterior scoliosis surgery.     

全椎弓根螺钉与钉钩联合系统治疗青少年Chiari畸形伴胸椎侧凸的疗效比较

 目的 评估青少年Chiari畸形伴胸椎侧凸不同内固定模式的选择对手术疗效的影响。 方法 回顾性分析2001年3月至2011年3月期间,接受后路胸椎融合术的75例Chiari畸形伴脊柱侧凸患者的病历资料,根据内固定方式分为全椎弓根螺钉组(44例)和钉钩联合组(31例)。分别测量术前、术后以及末次随访时的影像学指标：冠状面侧凸Cobb角、侧凸柔韧性、顶椎偏移、顶椎旋转及躯干偏移;矢状面胸椎后凸角、腰椎前凸角、躯干偏移及近端与远端交界区Cobb角。比较两组术前、术后及末次随访时上述影像学指标的改变。根据术前不同程度胸椎后凸进一步分组,比较两种内固定模式的手术疗效。结果 全椎弓根螺钉组术后胸弯平均矫正率为60.2％,明显著高于钉钩联合组(51.3％,t=2.372,P=0.023)。末次随访时全椎弓根螺钉组及钉钩联合组胸弯矫正丢失率分别为0.3％及1.7％(t=-0.468,P >0.05)。术后腰弯平均矫正率在全椎弓根螺钉组为61.7％,明显优于钉钩联合组51.1％(t=2.431,P=0.020)。术前全椎弓根螺钉组与钉钩联合组的胸弯顶椎偏移分别平均为25.0 mm和24.1 mm,术后减小至6.9 mm和7.4 mm,两组术后的胸弯顶椎偏移均获得明显改善。术前胸椎后凸>40°的病例中,全椎弓根螺钉组末次随访时矢状面近端交界区Cobb角为10.0°,高于钉钩联合组(4.5°,t=-2.031,P=0.052)。而且全椎弓根螺钉组近端交界性后凸发生率(20% )高于钉钩联合组(9%)。结论 对继发于青少年Chiari畸形的胸椎侧凸行后路内固定矫形,全椎弓根螺钉具有更好的畸形矫正率,但是,与钉钩联合固定相比,术前胸椎过度后凸的患者在胸椎全椎弓根螺钉固定术后远期发生近端交界性后凸的风险增高。     

Osteotomy for kyphosis in ankylosing spondylitis

Twenty-two patients suffering from progressive kyphosis due to ankylosing spondylitis underwent one or more lumbar osteotomies during 1957-1983. The primary thoracic kyphosis was 80° (45°-155°). The mean correction obtained by one level osteotomy was 44° (30°-60°).

The mean loss of correction after 3 years was 5°. The use of internal fixation reduced the loss of correction from 9° to 1°, also allowing ambulatory after-care and a shorter period of immobilization in plaster or jackets. We had no fatal and relatively few non-fatal complications; three cases of retrograde ejaculation were observed however. All the patients reported subjective respiratory improvement.     

Comparative analysis of pedicle screw versus hybrid instrumentation in adolescent idiopathic scoliosis surgery

The expectations of both the patient and surgeon have been greatly revised in the last 10 years with the introduction of pedicle screws (PS) in spinal surgery. In this study, we have retrospectively evaluated and compared the results of PS instrumentation and the Hybrid System (HS), the latter consists of pedicle screws, sublaminar wire and hooks. The mean follow-up period was 60.1 months (range: 49-94 months) for the patients of the HS group and 29.3 months (range: 24-35 months) for those of the PS group. In the HS group, pedicle screws were used at the thoracolumbar junction and lumbar vertebra, the bilateral pediculotransverse claw hook configuration was used at the cranial end of the instrumentation, sublaminar wire was used on the concave side of the apical region and the compressive hook was used on the convex side. In the PS group, PS were used on the concave sides at all levels and on the convex side of the cranial and caudal end of instrumentation, in the transition zone and at the apex. The two groups were comparable for variables such as mean age, preoperative Cobb angle, thoracic kyphosis angle, lordosis angle, coronal balance, flexibility of the curve, apical vertebra rotation (AVR), apical vertebra rotation (AVT) and the number of vertebrae included in the fusion (p > 0.05). The parameters of values of correction, ratio of correction loss, AV derotation, AVT correction ratio, amount of blood loss, operation time, postoperative global coronal and sagittal balance, thoracic kyphosis angle and lumbar lordosis angle were measured at the last follow-up and used for comparing the HS and PS groups. There was no statistically significant difference between the groups for correction ratio, postoperative coronal balance, postoperative thoracic kyphosis and lumbar lordosis angle, operation time, amount of blood loss and number of fixation points (p > 0.05) The difference for the ratio of correction loss, AV derotation angle and the AVT correction ratio at the last follow-up visit and for the total follow-up period between the groups was found to be statistically significant (p < 0.05). Although it is possible to obtain a similar amount of correction by either instrumentation system, the loss of correction seems to be lower with the more rigid PS construction. The PS system also has a stronger effect on vertebral bodies, thereby providing better AV de-rotation. There was no significant difference (p > 0.05) between the groups in terms of correction rate, postoperative coronal and sagittal balance, operation time, blood loss and number of fixation points. This may indicate that anchor points are more important than the use - or not - of screws. Correction durability and AV de-rotation was better with PS instrumentation, while AVT was better corrected by HS instrumentation (p < 0.05). We propose that the reason for the better correction of AVT with HS instrumentation is the forceful translation offered by the sublaminar wire at the apical region, while the reason for the better correction durability of the PS instrumentation may be due to the fact that multiple pedicle screws which afford three-column control are better at maintaining the correction and preventing late deterioration.     

Correction of adolescent idiopathic scoliosis using thoracic pedicle screw fixation versus hook constructs

This retrospective study was undertaken to determine the effectiveness and cost of thoracic pedicle screws versus laminar and pedicle hooks in patients undergoing surgical correction of adolescent idiopathic scoliosis (AIS). Immediate preoperative and 6-week postoperative radiographs were examined in 25 consecutive cases of children with AIS who were divided into two groups, those with thoracic pedicle screw constructs and those with thoracic hook constructs. Endpoints collected included radiographic measures, complications, surgical time, implant cost, and quality-of-life measures. Ten children underwent spinal fusion using thoracic pedicle screw fixation and 15 underwent thoracic constructs composed of hooks. Similar sex and age distribution were noted in both groups, and among the 20 girls and 5 boys the average age was 14.5. The mean preoperative Cobb angle was 53.5 degrees for the screw group and 52.5 degrees for the hook group. Correction averaged 70.2% for the screw group and 68.1% for the hook group. There were no significant differences between the two patient groups in terms of percentage of or absolute curve change after surgery. The apical vertebral translation, end vertebral tilt angle, and coronal balance did not differ significantly between the two patient groups. Comparison of operative time and quality of life revealed no significant differences. Screw constructs were significantly more expensive than hook constructs. The correction obtained from thoracic pedicle screw fixation is comparable to traditional hook constructs in AIS. Surgery using either construct effectively corrects AIS.     

Triggered electromyographic threshold for accuracy of thoracic pedicle screw placement in a porcine model.

STUDY DESIGN: A porcine model of thoracic pedicle screw insertion was used to determine the effect of screw position on triggered electromyographic response. OBJECTIVE: To develop a model of intraoperative detection of misplaced thoracic pedicle screws. SUMMARY OF BACKGROUND DATA: Triggered electromyographic stimulation has been a valuable aid in determining appropriate placement of lumbar pedicle screws. The use of pedicle screws is increasing in the thoracic spine. Misplaced thoracic pedicle screws may have significant implications if the spinal cord is injured. This study was an attempt to determine whether the established lumbar model can be used for thoracic pedicle screws. METHODS: Five 120- to 150-lb domestic pigs had 85 pedicle screws placed bilaterally in the thoracic spine at each level from T6 to T15. Screws were inserted entirely in the pedicle (Group A). After removal of the medial pedicle wall, the screws were reinserted in the pedicle with no neural contact (Group B). The screws were then placed with purposeful contact with the neural elements (Group C). The screws were stimulated, eliciting an electromyographic response in the intercostal muscles for each instrumented level. The type of response noted was classified as either primary (response from appropriate nerve root), secondary (response at different root) or no response (response at different root, no response at appropriate root). RESULTS: Two hundred fifty responses were recorded. A primary response was noted in 72% of recordings. There was a relatively consistent decrease in the triggered electromyographic response from Group A (mean 4.15 +/- 1.80 mA) to Group C (mean 3.02 +/- 2.53 mA) screws (P = 0.0003). There was little difference in the response obtained from Group A to Group B (mean 4.37 +/- 2.48 mA) screws (P > 0.05). When a primary response was recorded, the mean threshold electromyographic response recorded was significantly lower than recordings with secondary and no response recordings (P < 0.05). CONCLUSION: Even though there was a consistent decrease between the A and C screws that was more definitively separated when a primary response was elicited, it was not possible to determine a cutoff trigger electromyographic level that would consistently differentiate intraosseous from epidural pedicle screw placement. Furthermore, this method could not differentiate screws clearly in the pedicle from screws with medial pedicle wall breakthrough. A more direct method of spinal cord monitoring must be established to provide the surgeon with early warning of the potential of neural injury in the placement of thoracic pedicle screws.     

应用椎板开窗法置入胸椎椎弓根螺钉的精确性和安全性评估

目的 分析应用椎板开窗法行胸椎椎弓根螺钉置入治疗重度脊柱侧后凸患者的精确性和安全性. 方法 1996年6月至2007年12月,应用椎板开窗法行胸椎椎弓根螺钉置入治疗23例重度脊柱侧后凸患者(A组),其中男性9例,女性14例;年龄13～23岁,平均17.8岁;术前主胸弯冠状面Cobb角平均97.3°,平均后凸角67.4°.作为对照,同期应用非开放法置钉治疗重度脊柱侧后凸患者22例(B组),其中男性7例,女性15例;年龄14～21岁,平均17.2岁;术前主胸弯冠状面Cobb角平均为96.6°,平均后凸角62.1°.两组患者术后均行CT扫描,统计螺钉置入并发症,对螺钉穿透椎弓根皮质骨的CT扫描图像进行联机测量并统计分析.结果 A组和B组各置入胸椎椎弓根螺钉209和201枚,术中发生椎弓根骨折5例和16例,发生硬膜撕裂4例和7例,螺钉错置18枚和45枚.B组螺钉错置率高于A组,差异具有统计学意义(P<0.05).A组上、中胸椎与下胸椎之间、凸侧与凹侧之间,螺钉错置率差异均具有统计学意义(P<0.05).两组均无脊髓及大血管损伤. A和B组经平均3.2年、3.4年随访,术后冠状面和矢状面平均矫正度未见明显丢失.结论 重度脊柱侧后凸胸椎椎弓根螺钉置入技术难度较高,应用椎板开窗法可有效增加螺钉置入精确性和安全性.     

Junction kinematics between proximal mobile and distal fused lumbar segments: biomechanical analysis of pedicle and hook constructs

Background contextBiomechanical studies have demonstrated increased motion in motion segments adjacent to instrumentation or arthrodesis. The effects of different configurations of hook and pedicle screw instrumentation on the biomechanical behaviors of adjacent segments have not been well documented.PurposeTo compare the effect of three different fusion constructs on adjacent segment motion proximal to lumbar arthrodesis.MethodsSeven human cadaver lumbar spines were tested in the following conditions: 1) intact; 2) L4–L5-simulated circumferential fusion (CF); 3) L4–L5-simulated fusion extended to L3 with pedicle screws; and 4) L4–L5-simulated fusion extended to L3 with sublaminar hooks. Rotation data at L2–L3, L3–L4, and L4–L5 were analyzed using both load limit control (±7.5 N·m) and displacement limit control (truncated to the greatest common angular motion of the segments for each specimen).ResultsBoth the L3–L4 and L2–L3 motion segments above the L4–L5-simulated CF had significantly increased motion in all loading planes compared with the intact spine, but no significant differences were found between L3–L4 and L2–L3 motion. When the L3–L4 segment was stabilized with pedicle screws, its motion was significantly smaller in flexion, lateral bending, and axial rotation than when stabilized with sublaminar hooks. At the same time, L2–L3 motion was significantly larger in flexion, lateral bending, and axial rotation in the pedicle screw model compared with the sublaminar hook construct.ConclusionsThe use of sublaminar hooks to stabilize the motion segment above a circumferential lumbar fusion reduced motion at the next cephalad segment compared with a similar construct using pedicle screws. The semiconstrained hook enhancement may be considered if a patient is at a risk of adjacent segment disorders.     

全节段与选择性节段椎弓根螺钉固定治疗重度僵硬型青少年特发性脊柱侧凸比较

目的 比较全节段椎弓根螺钉(all segmental pedicle screws,ASPS)固定与选择性节段椎弓根螺钉(selective segmental pedicle screws,SSPS)固定治疗重度僵硬型青少年特发性脊柱侧凸(adoles-cent idiopathic scoliosis,AIS)的疗效.方法 回顾性分析我院2003年3月至2008年12月期间单纯行后路椎弓根螺钉固定融合治疗的重度僵硬型AIS患者.站立前后位主胸弯Cobb角>70°和柔韧度<30%者为筛选对象,从327例AIS患者中筛选出符合标准的48例,22例行SSPS同定,26例行ASPS固定.统计并比较两组患者手术时的年龄、术前冠状面主胸弯Cobb角、脊柞柔韧度、术中出血量、术后1周及末次随访时的矫正率.结果 ASPS组和SSPS组的平均年龄分别为15.65岁和17.32岁,术前冠状面主胸弯Cobb角分别为86.77°±11.71°(71.31°～107.51°)和87.56°±14.88°(70.10°～117.83°),柔韧度分别为15.82%±7.37%(6.82%～29.74%)和19.30%±9.19%(0.89%～29.71%),手术时间分别为(280.69±35.92)min和(275.10±33.91)min,术中出血量分别为(988.50±287.80)ml和(800.98±360.47)ml(t=2.004,P=0.051),术后1周冠状面主胸弯畸形矫正率分别为60.07%±8.80%和46.79%±14.90%(u=3.280,P=0.001).ASPS组有1例因凸侧断棒而明显丢失畸形矫正率,余患者无明显丢失.结论 对于重度僵硬型AIS,ASPS治疗的患者术后冠状面主胸弯矫正率明显高于SSPS治疗的患者.     

Transverse process wiring for thoracic scoliosis

We describe a method of reducing neurological risk by avoiding neural elements when performing segmental spinal fixation for scoliosis. This was done by making use of the transverse processes of the thoracic vertebrae 1-11 and wired plates. The wires are prevented from cutting the bone by attaching them to rectangular plates. These wired plates on the two sides of each segment should be firmly fixed to the base of the transverse process by tying them to each other. Maximum correction is obtained by spreading the force applied by stabilizing each thoracic vertebra from both sides. Derotation is attempted when all the wires have been tightened. Tension forces are spread to all fixated vertebrae simultaneously and the correction should be carried out at all levels at the same time. On the convex side, each wire connects over the rod to the next one above it and, tightened one by one, provides compression.

We treated 15 patients having a thoracic curve with this method and followed them for 25-39 months. In 2 cases of congenital scoliosis, a 50% correction was obtained. In 3 cases of neurofibromatosis scoliosis, a 55% correction was achieved. In 10 cases of idiopathic scoliosis, the correction was 60%. When the thoracic sagittal contour was evaluated, thoracic kyphosis, which had been between -20" and +90°, had improved to between +8° and +43° in all cases. No infection or neurological complications occurred.     

Computer-assisted thoracic pedicle screw placement: an in vitro feasibility study

STUDY DESIGN: In this cadaveric study, a computer-assisted image guidance system was tested for accuracy of thoracic pedicle screw placement. OBJECTIVES: Evaluate the system's accuracy for thoracic pedicle screw placement in vitro. SUMMARY OF BACKGROUND DATA: The effective use and reliability of pedicle screw instrumentation in providing short-segment stabilization and correction of deformity is well known in the lumbar spine. Pedicle screw placement in the thoracic spine is difficult because of the small dimensions of the thoracic pedicles and risk to the adjacent spinal cord and neurovascular structures. Investigators have shown the improved accuracy of computer-assisted lumbar pedicle screw placement; but the accuracy of computer-assisted thoracic pedicle screw placement, which is becoming more widely used, has not been shown. METHODS: In five human cadavers, 120 thoracic pedicle screws were placed with computer-assisted image guidance. The largest clinically feasible screw was used based on the cross-sectional dimensions of each pedicle. The accuracy was assessed by postoperative computed tomography and visual inspection. RESULTS: The overall pedicle cortex violation was 23 of 120 pedicles (19.2%). Nine violations (7.5%) were graded as major and 14 (11.7%) as minor. A marked and progressive learning curve was evident with the perforation rates that decreased from 37.5% in the first cadaver to 4.2% in the last two cadavers. CONCLUSIONS: Accurate thoracic pedicle screw placement is feasible with computer-assisted surgery. However, as with any other new surgical technology, the learning curve must be recognized and incorporated into the necessary fundamental knowledge and experience for these procedures.     

Effect of the Boston thoracic brace on the frontal and sagittal curves of the spine

The purpose of the present study was to compare the sagittal and lateral curves in progressive idiopathic scoliosis treated conservatively with the Boston thoracic brace. The importance of the delordosation was confirmed. The correlation was, however, seen only between correction of the lumbar lordosis and correction of the lumbar scoliosis. The correction of the proximal thoracic scoliosis with the brace was equally good, without a similar correlation between correction of the proximal scoliosis and correction of the sagittal curves being observed.

A coupling between the correction of the two scolioses may therefore be suspected. Further, the correcting forces of the Boston thoracic brace seemed to be approximately the same, independent of the range of the scoliosis, at least between 10° and 40°.     

全椎弓根螺钉与钉钩混合系统治疗青少年特发性脊柱侧凸的疗效分析

目的 通过临床病例回顾,对后路全椎弓根螺钉系统和钉钩混合系统治疗青少年特发性脊柱侧凸的疗效进行对比分析研究.方法 从2000年至2004年进行手术治疗的青少年特发性脊柱侧凸患者中选取60例配对分为两组(A、B两组,各30例),A组采用后路钉钩混合系统固定,B组采用后路全椎弓根螺钉系统固定,配对患者年龄相似、融合节段相仿、Lenke分型相近.通过比较手术前后影像学改变、手术时间、术中出血等,对两种手术方法的疗效进行对比分析研究.结果 A组患者术前冠状面主弯Cobb角平均为61°,术后为25°,平均矫正率为59%;B组患者术前冠状面主弯Cobb角平均为60°,术后为18°,平均矫止率为70%.两组患者主弯矫正率差异有统计学意义(P=0.002),随访2年两组间主弯矫正率差异仍有统计学意义(A、B两组分别为49%、67%,P<0.001).矢状面上,与术前相比,术后2年A组的胸椎后凸角平均减少了1°,而B组则减少了6°,差异有统计学意义(P=0.026).随访结果 提示,两组在下端椎远端融合椎体数、平均失血量方面差异均无统计学意义.两组患者术后均未出现神经系统并发症.结论 全椎弓根螺钉系统较钉钩混合系统能提供更好的主弯矫止率,而在最下端固定椎体的选择、术中失血量方面,两种内固定系统未见明显差异.