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.     

A biomechanical analysis of the self-retaining pedicle hook device in posterior spinal fixation

Regular hooks lack initial fixation to the spine during spinal deformity surgery. This runs the risk of posterior hook dislodgement during manipulation and correction of the spinal deformity, that may lead to loss of correction, hook migration, and post-operative junctional kyphosis. To prevent hook dislodgement during surgery, a self-retaining pedicle hook device (SPHD) is available that is made up of two counter-positioned hooks forming a monoblock posterior claw device. The initial segmental posterior fixation strength of a SPHD, however, is unknown. A biomechanical pull-out study of posterior segmental spinal fixation in a cadaver vertebral model was designed to investigate the axial pull-out strength for a SPHD, and compared to the pull-out strength of a pedicle screw. Ten porcine lumbar vertebral bodies were instrumented in pairs with two different instrumentation constructs after measuring the bone mineral density of each individual vertebra. The instrumentation constructs were extracted employing a material testing system using axial forces. The maximum pull-out forces were recorded at the time of the construct failure. Failure of the SPHD appeared in rotation and lateral displacement, without fracturing of the posterior structures. The average pull-out strength of the SPHD was 236 N versus 1,047 N in the pedicle screws (P < 0.001). The pull-out strength of the pedicle screws showed greater correlation with the BMC compared to the SPHD (P < 0.005). The SPHD showed to provide a significant inferior segmental fixation to the posterior spine in comparison to pedicle screw fixation. Despite the beneficial characteristics of the monoblock claw construct in a SPHD, that decreases the risk of posterior hook dislodgement during surgery compared to regular hooks, the SPHD does not improve the pull-out strength in such a way that it may provide a biomechanically solid alternative to pedicle screw fixation in the posterior spine.     

Segmental pedicle screw instrumentation in idiopathic thoracolumbar and lumbar scoliosis

The role of posterior correction and fusion in thoracolumbar and lumbar scoliosis as well as pedicle screw instrumentation in scoliosis surgery are matters of debate. Our hypothesis was that in lumbar and thoracolumbar scoliosis, segmental pedicle screw instrumentation is safe and enables a good frontal and sagittal plane correction with a fusion length comparable to anterior instrumentation. In a prospective clinical trial, 12 consecutive patients with idiopathic thoracolumbar or lumbar scolioses of between 40° and 60° Cobb angle underwent segmental pedicle screw instrumentation. Minimum follow-up was 4 years (range 48– 60 months). Fusion length was defined according to the rules for Zielke instrumentation, normally ranging between the end vertebrae of the major curve. Radiometric analysis included coronal and sagittal plane correction. Additionally, the accuracy of pedicle screw placement was measured by use of postoperative computed tomographic scans. Major curve correction averaged 64.6%, with a loss of correction of 3°. The tilt angle was corrected by 67.0%, the compensatory thoracic curve corrected spontaneously according to the flexibility on the preoperative bending films, and led to a satisfactory frontal balance in all cases. Average fusion length was the same as that of the major curve. Pathological thoracolumbar kyphosis was completely corrected in all but one case. One patient required surgical revision with extension of the fusion to the midthoracic spine due to a painful junctional kyphosis. Eighty-five of 104 screws were graded “within the pedicle”, 10 screws had penetrated laterally, 5 screws bilaterally and 4 screws medially. No neurological complications were noted. In conclusion, despite the limited number of patients, this study shows that segmental pedicle screw instrumentation is a safe and effective procedure in the surgical correction of both frontal and sagittal plane deformity in thoracolumbar and lumbar scoliosis of less than 60°, with a short fusion length, comparable to anterior fusion techniques, and minimal loss of correction. Received: 23 September 1999 Revised: 20 January 2000 Accepted: 26 January 2000     

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.     

New means in spinal pedicle hook fixation

Summary Pedicle hooks which are used as an anchorage for posterior spinal instrumentation may be subjected to considerable three-dimensional forces. In order to achieve stronger attachment to the implantation site, hooks using screws for additional fixation have been developed. The failure loads and mechanisms of three such devices have been experimentally determined on human thoracic vertebrae: the Universal Spine System (USS) pedicle hook with one screw, a prototype pedicle hook with two screws and the Cotrel-Dubousset (CD) pedicle hook with screw. The USS hooks use 3.2-mm self-tapping fixation screws which pass into the pedicle, whereas the CD hook is stabilised with a 3-mm set screw pressing against the superior part of the facet joint. A clinically established 5-mm pedicle screw was tested for comparison. A matched pair experimental design was implemented to evauluate these implants in constrained (series I) and rotationally unconstrained (series II) posterior pull-out tests. In the constrained tests the pedicle screw was the strongest implant, with an average pull-out force of 1650 N (SD 623 N). The prototype hook was comparable, with an average failure load of 1530 N (SD 414 N). The average pull-out force of the USS hook with one screw was 910 N (SD 243 N), not significantly different to the CD hook's average failure load of 740 N (SD 189 N). The result of the unconstrained tests were similar, with the prototype hook being the strongest device (average 1617 N, SD 652 N). However, in this series the difference in failure load between the USS hook with one screw and the CD hook was significant. Average failure loads of 792 N (SD 184 N) for the USS hook and 464 N (SD 279 N) for the CD hook were measured. A pedicular fracture in the plane of the fixation screw was the most common failure mode for USS hooks. The hooks usually did not move from their site of implantation, suggesting that they may be well-suited for the socalled segmental spinal correction technique as used in scoliosis surgery. In contrast, the CD hook disengaged by translating caudally from its site of implantation in all cases, suggesting a mechanical instability. The differences in observed hook failure modes may be a function of the type and number of additional fixation screws used. These results suggest that additional screw fixation allows stable attachment of pedicle hooks to their implantation site. Hooks using additional fixation screws passing obliquely into the pedicle apparently provide the most rigid attachment. The second fixation screw of the prototype hook almost doubles the fixation strength. Thus, the prototype hook might be considered as an alternative to the pepdicle screw, especially in the upper thoracic region.     

退行性脊柱侧凸三维矫形术并发症的探讨

目的:探讨使用椎弓根螺钉系统矫治退行性脊柱侧凸的并发症及其预防措施。方法:对82例退行性脊柱侧凸患者采用4种不同的手术方式:17例先行一期前路松解、支撑性融合,二期后路多节段椎弓根螺钉矫形,后外侧植骨融合;41例行后路椎管减压、椎体间支撑融合(PLIF)、椎弓根螺钉矫形内固定 后外侧植骨融合术;14例行后路短缩、椎管减压、椎弓根螺钉矫形内固定 后外侧植骨融合术;10例行椎管减压、椎弓根矫形内固定 后外侧植骨融合术。对75例获得6个月至4年(平均2年3个月)随访患者的并发症进行回顾性分析。结果:本组无围手术期死亡,术后重症监护时间平均22h,切口感染1例,切口延迟愈合4例;7例术后出现肺部感染,经处理后好转;6例手术后出现心脏病复发,经内科联合处理后好转;9例术后出现双下肢疼痛,经保守治疗3个月症状缓解;4例腰背部疼痛缓解不明显。无断钉、断棒现象。88.6%的患者对手术治疗的结果满意。结论:三维矫形手术治疗退行性脊柱侧凸的并发症较多且严重,手术治疗需慎重考虑患者的全身情况及术前症状,以选择适合的手术方式。     

Ventrale Skolioseoperationen

For more than 2 decades ventral derotation spondylodesis (Zielke VDS) as a major improvement over Dwyer instrumentation (DI) was the gold standard of instrumented curve correction and stabilization from the anterior approach. As the first available system it enables a true three-dimensional curve correction. A disadvantage is the low internal stabilization capability with a need for long-term external stabilization by means of cast and brace treatment postoperatively. Meanwhile with the development of modern single and dual solid rod systems these disadvantages can be avoided completely. Video-assisted (thoracoscopic) anterior scoliosis surgery accounts for less than 2% of anteriorly treated scoliosis cases, mainly due to a long operating time and significant learning curve. From the posterior approach the Cotrel-Dubousset instrumentation (CDI) as a polysegmentally attached posterior hook threaded dual rod system used to be state of the art for a long time, since it eliminated the disadvantages of Harrington instrumentation (HI) in terms of only one-dimensional correction and low stabilization capabilities. However even with CDI effective derotation was impossible. In posterior scoliosis surgery there is a strong trend away from hook systems towards transpedicular segmentally fixed dual rod systems not only in the lumbar spine but also in the thoracic area. Advantages of these newer techniques are shorter fusion, improved correction, and less loss of correction over time. Advantages of modern anterior instrumentation systems in comparison to posterior transpedicular instrumented dual rod systems are less blood loss, better derotation, slightly shorter fusion levels, and a better influence on sagittal plane control or improvement especially for hypokyphotic thoracic scoliosis cases. Our data also document a superior spontaneous correction of the lumbar curve after selective anterior instrumented correction (Lenke 1B+C), although other studies could not find significant differences. In our experience the neurological risk of anterior instrumented correction is also lower than that of posterior scoliosis surgery, although the morbidity and mortality data of the Scoliosis Research Society could not prove that anymore in recent years. A negative effect of anterior transthoracic scoliosis surgery in comparison to posterior surgery is a more negative effect on lung function, which improves slower after surgery and does not quite reach the levels of posterior surgery at follow-up. But new data on posterior segmental transpedicular correction and fusion also prove a lordosating effect with negative effect on lung function.     

青少年特发性脊柱侧凸椎弓根螺钉的误置模式及危险因素

目的 评估青少年特发性脊柱侧凸(AIS)椎弓根螺钉不良置入的模式并分析其原因.方法 收集从2008年7月至9月行后路椎弓根螺钉固定的70例AIS患者的临床资料,其中男性12例,女性58例;年龄12～19岁,平均(14.5±2.7)岁;术前Cobb角40°～125°,平均62.0°±18.2°.术中根据解剖标志徒手置入椎弓根螺钉,所有患者术后均行CT检查.在PACS系统上通过PacsClient软件测量螺钉穿破椎弓根内、外壁以及椎体前缘的距离.定义穿破任一壁超过2 mm为不良置钉.不良置钉中穿破内壁超过4 mm或钉尖使主动脉变形定义为高危置钉.对数据进行统计学分析,探讨不良置钉的危险因素.结果 共置入椎弓根螺钉1030枚,胸椎773枚,腰椎257枚.不良置钉108枚(10.5%),其中穿破外壁35枚,穿破内壁56枚,穿破椎体前缘33枚(其中有16枚既穿破了椎体前缘又穿破了外壁).高危置钉16枚(1.6%).顶椎、顶椎近端第5节段和顶椎远端第4节段的不良置钉率高于其他节段,其中顶椎左侧和顶椎近端第5节段右侧不良置钉率均高于对侧.顶椎区高危置钉率最高,达4.8%.Cobb角>90°组不良置钉率高于Cobb角40°～90°组,椎体旋转Ⅲ～Ⅳ度组不良置钉率高于椎体旋转0～Ⅱ度组.结论 AIS不良置钉集中在顶椎、顶椎近端第5节段和顶椎远端第4节段3个区域,高危置钉多发生在顶椎区,危险因素包括Cobb角大小、旋转程度以及与顶椎的距离.     

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.     

The suprapedicle claw construct in anterior scoliosis surgery

Proximal screw pullout is a well-recognized problem in anterior scoliosis surgery, with a rate of pseudarthrosis or screw pullout ranging from 15 to 30%. To prevent screw pullout at the top of the construct, the authors have devised the concept of a claw for the top instrumented vertebra. The claw consists of a classic anterior vertebral body screw inserted parallel to the inferior end-plate and in the posterior portion of the vertebral body 8 mm in front of the spine canal. After rib desarticulation, a laminar hook of a small size is inserted over the superior aspect of the pedicle of the same vertebra. The rod is then inserted into the two side openings of the screw and the hook. Compression across the hook and the screw is then performed, making a claw construct. This concept can also be extended in the case of early revision for a proximal screw pullout, where it is possible to revise the instrumentation with an offset connector linking the rod to the superior portion of the pedicle where the suprapedicule hook has been inserted. We report two cases where a suprapedicle claw was successfully used in anterior scoliosis correction of a right thoracic curve. Such a concept may represent the solution to proximal screw pullout in anterior scoliosis correction.     

Usefulness of a navigation system in surgery for scoliosis: segmental pedicle screw fixation in the treatment

Study design  Postoperative outcomes of segmental pedicle screw fixation were evaluated in posterior scoliosis surgery with the use of navigation system. Objectives  We report the usefulness of a navigation system and a segmental pedicle screw fixation in surgery for scoliosis. Summary of background data  Few reports on a segmental pedicle screw fixation method for scoliosis surgery using a navigation system have been published. This is the report on the usefulness of a navigation system in segmental pedicle screw fixation. Methods  We targeted 16 cases in which segmental pedicle screw fixation had been performed using a navigation system at our hospital. We inserted 264 pedicle screws in total, and we did not perform registration for each corpus vertebrate in order to shorten the duration of the surgery. We reviewed screw deviation among the items for review using Neo classification with postoperative CT images (1.25 mm). For screw deviation in this case, grade 2 or higher in the Neo classification system was designated as total deviation. Furthermore, we evaluated the registration period per corpus vertebrae, the complications, duration of surgery, blood loss, Cobb angle, and the correction rate. Results  In terms of screw deviation, 11 (4.2%) of the 264 inserted screws were classified as total deviation. However, there were no neurovascular complications during or after surgery in any cases, and all cases maintained strong internal fixation. In the relationship between the use or nonuse of registration and the deviation, four screws (3.2%) in the corpus vertebrae for which registration was performed and seven screws (5.0%) in the adjacent corpus vertebrae for which registration was not performed had deviated. The duration of registration per corpus vertebrate averaged 4 min and 24 s (58–791 s), but registration also requires a learning curve, so the duration of registration per corpus vertebrae averaged 1 min and 14 s in more recent cases, thus marking a significant shortening. Conclusion  Segmental pedicle screw fixation are excellent in regard to their fixing and correction force and have been clinically applied even in surgery for scoliosis, but the potential risk of neurovascular complications is unavoidable. The adoption of a navigation system in surgery for scoliosis is useful to increase the safety and certainty of the insertion of pedicle screws.     

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.     

TSRH内固定治疗脊柱侧凸

目的　回顾性研究TSRH(TexasScottishRiteHospital)脊柱内固定系统在治疗脊柱侧凸的临床疗效。 方法　对 1998年 1月至 2 0 0 0年 12月手术治疗的 12 9例脊柱侧凸患者 ,总结其侧弯矫形、脊柱平衡、并发症及 3年以上的随访结果。根据手术方法不同 ,共分为 4组。A组 :单纯脊柱后路融合固定术 ;B组 :单纯脊柱前路融合固定术 ;C组 :分期前、后路融合固定术 ;D组 :Ⅰ期前、后路融合固定术。四组患者均应用TSRH内固定系统。手术时平均年龄 14 .2岁 (6～ 5 5岁 ) ,平均随访 34个月。结果　A组 :78例病人行单纯脊柱后路融合TSRH内固定 ,术后平均矫形率为6 3.4 %。随访 38个月 (2 4～ 5 0个月 ) ,平均矫形丢失 7°,矫形丢失率平均 9.5 %。本组并发症发生率为 12 .8% ,包括 3例脱钩 ,3例螺钉断裂 (共 6枚螺钉 ) ,1例术后侧弯失代偿 ,1例术后发生曲轴现象。B组 :2 2例患者行单纯脊柱前路融合、短节段TSRH内固定 ,平均矫形率为 74 .8%。平均随访 36个月 ,平均矫形率丢失 5 %。 2例发生一过性交感神经损伤。术后 6个月内均自然恢复。C组 :17例有 90°以上的侧弯 ,且Bending像上侧弯仍大于 7°的患者行前路松解 ,2～ 3周后再行后路融合TSRH内固定。本组平均手术时间 8.3h ,出血 935ml,输血 6 83ml,平均矫形 33.6°,矫     

采用关键椎置钉及选择性融合治疗Lenke6型AIS可行性的有限元分析

[目的]通过有限元模型矫形手术模拟的方法探讨关键椎置钉技术的可行性及矫形效果,分析Lenke 6型脊柱侧凸是否适合采用选择性融合策略.[方法]通过CT图像建立1例Lenke 6型特发性脊柱侧凸三维有限元模型,并验证其有效性后,利用后路CD矫形手术模拟技术,分别模拟全节段椎弓根钉技术矫形工况、关键椎置钉技术矫形工况、胸腰弯选择性融合工况等.测量各种工况完成后双弯Cobb角度、计算矫形率,分析各种工况的矫形效果.[结果]全节段椎弓根钉技术(非选择性融合):胸腰弯矫形率47.8％,主胸弯矫形率43.9％;关键椎置钉技术:胸腰弯矫形率44.2％,主胸弯矫形率19.1％;胸腰弯选择性融合:胸腰弯矫形率43.5％,主胸弯矫形率14.3％.[结论]全节段椎弓根钉技术因矫形力施加点更多,矫形效果较关键椎置钉技术更佳;Lenke 6型脊柱侧凸采用选择性融合策略应慎重,非选择性融合策略能明显矫正双弯,纠正脊柱序列,更适合该类型病例.     

Augmentation of a loosened sacral pedicle screw with percutaneous polymethylmethacrylate injection

STUDY DESIGN: Case report describing augmentation of a loosened sacral screw with percutaneous injection of polymethylmethacrylate. OBJECTIVE: To highlight the advantages of percutaneous injection of polymethylmethacrylate in treatment of loosened pedicle screws. SETTING: Turkey. SUMMARY OF BACKGROUND DATA: Lumbosacral instrumentation with pedicle screws is a commonly used procedure for correcting deformity and stabilizing the spine until bony fusion occurs. Loosening of the screws is a complication of this procedure and is seen more frequently in multilevel instrumentation, particularly in those instrumentations using sacral screws. METHOD: We present the case of a woman who had had L3-L4-L5-S1 instrumentation with pedicle screws who developed severe low back pain radiating to the left hip 2 months after the operation. Radiologic and clinical examination revealed that the left pedicle screw of the sacrum had loosened, and revision surgery was planned. The left sacral screw was augmented with percutaneous injection of polymethylmethacrylate. RESULTS: The patient was free of pain after the operation. CONCLUSIONS: We suggest that percutaneous polymethylmethacrylate injection around a loosened screw may be an alternative to major open revision surgery in cases of sacral screw failure in multisegmental instrumentation.     

全椎弓根螺钉与钩钉联合系统对脊柱侧凸的矫形效果比较

目的比较全椎弓根螺钉与钩钉联合系统对特发性脊柱侧凸的后路矫形效果。方法对40例特发性脊柱侧凸患者进行回顾性对照研究,其中全节段椎弓根螺钉组20例,钩钉联合器械组20例。对两组的手术效果、手术时间和失血量等进行对照分析。结果平均冠状面矫形率：全节段椎弓根螺钉组82．4％,钩钉联合器械组71．8％（P〈0．01）;术后1—3年平均冠状面矫形率：全节段椎弓根螺钉组77．O％,钩钉联合器械组62．5％（P〈0．01）;平均顶椎旋转矫正率：全节段椎弓根螺钉组63％,钩钉联合器械组32％（P〈0．01）。而矢状面矫形效果、下固定椎倾斜度改善率、躯干偏移、手术时间、失血量方面,两组无明显差别（P〉0．05）。所有病例均未出现脊髓、神经根损伤等严重并发症。结论全椎弓根螺钉较钩钉联合系统具有更好的矫形效果,胸椎椎弓根螺钉置入安全可靠。     

Difficult thoracic pedicle screw placement in adolescent idiopathic scoliosis

STUDY DESIGN: Retrospective radiographic and clinical consecutive case series. OBJECTIVE: The objective of this study was to identify patients treated with posterior spinal fusion and pedicle screw instrumentation for adolescent idiopathic scoliosis (AIS) in whom it was not possible to place a planned pedicle screw, and describe the possible difficulties in screw placement. SUMMARY OF BACKGROUND DATA: Despite the knowledge of anatomic characteristics of upper thoracic spine pedicles and considerable experience in thoracic pedicle screw placement, inserting pedicle screws in some patients with AIS may be difficult. METHODS: We reviewed 96 patients with AIS in whom the intent was to use an all-screw construct in 2004. Placement of the pedicle screws was usually by the freehand method, with intraoperative fluoroscopy used as needed. If a screw could not be safely placed after multiple attempts, a down-going supralaminar or transverse process hook was placed. Medical records were reviewed and radiographs were measured by one of the authors. RESULTS: We identified 17 cases (18%) in which a hook had been placed. All cases had a major thoracic curve (Lenke 1, 2, and 3) and the single hook had always been placed at the most cephalad level of the construct on the patient's right side. The most common levels for hook placement were T3 and T4; these pedicles were noted to be sclerotic, narrow, and have a moderate amount of rotation on the preoperative posterior-anterior and side bending radiographs. CONCLUSIONS: Care should be exercised during pedicle screw instrumentation in the apical region of the proximal thoracic curve, whether structural or nonstructural, especially in the concavity. The preoperative radiographs may give helpful clues to intraoperative challenges of pedicle screw insertion at the uppermost level of instrumentation. Hook fixation was satisfactory in this scenario.     

脊柱后入路手术治疗Simmon Ⅱ型腰椎退变性侧凸

目的探讨后路手术治疗Simmon型腰椎退变性侧凸的临床疗效。方法自2008年3月至2010年2月对28例Simmon型腰椎退变性侧凸患者,采用后路椎管减压、矫形、椎弓根螺钉内固定加椎间和/或后外侧植骨融合手术治疗,术后随访3个月～2年,观察其疗效。结果全部患者手术顺利,随访时间平均11个月（3～24个月）。83%的患者疼痛明显减轻,下肢神经性间歇性跛行缓解,随访期间矫正度数无明显丢失。结论充分减压、适当矫形、融合加椎弓根螺钉内固定是治疗Simmon型腰椎退变性侧凸安全有效的方法。     

Posterior instrumentation and fusion

The purpose of surgery for adolescent idiopathic scoliosis, which characteristically includes thoracic hypokyphosis and all three columns of the spine, is the achievement of a balanced spine while preserving as many motion segments as possible and avoiding neurologic damage. Many approaches have been defined in the treatment of this common disease. Posterior-only surgery, instrumentation and fusion have become the preferred technique in many centers throughout the world due to simplicity of approach, decreased risk of certain complications and the correction power of pedicle screws. This review attempts to summarize the advantages and disadvantages related to posterior instrumentation and fusion in adolescent idiopathic scoliosis.