寰椎椎弓根髓腔大小对椎弓根螺钉置入的影响

目的:评估寰椎椎弓根髓腔大小对椎弓根螺钉置入的影响.方法:从2009年1月～2012年6月在本院行寰枢椎后路固定融合术的患者中,筛选出年龄≥20岁、术前影像学测量寰椎椎弓根高度＞4mm的患者97例,男41例,女56例,年龄20～79岁,平均41.6岁术中选择内固定方法时,寰椎首先选择椎弓根螺钉固定,若椎弓根螺钉置钉失败则改用椎板钩或侧块螺钉固定.其中145个椎弓根成功置入椎弓根螺钉,49个椎弓根因无法形成椎弓根螺钉通道,改用椎板钩或侧块螺钉固定.用CT 三维重建技术测量所有患者寰椎椎弓根髓腔的高度.根据髓腔高度将寰椎椎弓根分为3型:Ⅰ型,髓腔高度≥2mm;Ⅱ型,髓腔高度＜2mm;Ⅲ型,无髓腔.统计每型椎弓根成功置入椎弓根螺钉的比率,比较其差异.结果:椎弓根螺钉固定组中,Ⅰ、Ⅱ、Ⅲ型椎弓根个数(比率)分别为104个(71.7％)、39个(26.9％)、2个(1.4％);非椎弓根螺钉固定组中,Ⅰ、Ⅱ、Ⅲ型椎弓根个数(比率)分别为2个(4.1％)、28个(57.1％)、19个(38.8％).Ⅰ、Ⅱ、Ⅲ型椎弓根成功置入椎弓根螺钉的比率分别为98.1％(104/106)、58.2％(39/67)、9.5％(2/21),Ⅰ型明显高于Ⅱ型和Ⅲ型,Ⅱ型明显高于Ⅲ型,差异均有统计学意义(P＜0.001).结论:寰椎椎弓根髓腔大小对椎弓根螺钉的置入有一定影响.寰椎椎弓根髓腔高度≥2mm时建议行椎弓根螺钉固定,髓腔高度＜2mm时可根据术者情况选择固定方法;无髓腔时建议不行椎弓根螺钉固定.     

中国青少年特发性脊柱侧凸患者胸椎椎弓根形态学三维CT分析

目的 总结中国青少年特发性脊柱侧凸患者胸椎椎弓根形态学特点,与其他人种特发性脊柱侧凸患者胸椎椎弓根形态比较,为手术中胸椎安全置钉提供参考.方法 回顾性分析2007年7月至2012年6月期间56例于我院行术前CT扫描三维重建的青少年特发性脊柱侧凸(右胸弯)患者的资料,男10例,女46例;年龄10～18岁,平均14.8岁.Lenke分型:Ⅰ型28例、Ⅱ型12例、Ⅲ型14例、Ⅳ型2例.术前主胸弯Cobb角平均为55°(36°～90°).测量其胸椎两侧椎弓根在矢状面、冠状面、轴面的置钉长度、椎弓根宽度及角度等形态学指标,总结其变化规律,并与文献报道的其他人种数据进行对比.结果 主胸弯顶椎区凹侧椎弓根宽度小于凸侧,椎弓根置钉长度大于凸侧,椎弓根尾倾角度小于凸侧.椎弓根矢状面宽度自头端向尾端逐渐增加,平均值范围为0.68～1.36 cm;轴面椎弓根宽度平均值范围为0.30～0.70 cm.冠状面椎弓根最小径略小于轴面椎弓根宽度,平均值范围为0.28～0.67 cm.结论 与欧美人种相比,中国特发性脊柱侧凸患者椎弓根宽度较小.顶椎区凹侧置钉难度大、风险高,建议使用直径3.5 mm椎弓根螺钉或采用极外侧置钉法.     

个体化选择脊柱侧凸患者胸椎椎弓根螺钉进钉点的研究

目的:探讨个体化选择脊柱侧凸患者胸椎椎弓根螺钉进钉点对置钉准确性的影响.方法:2006年3月至2008年6月手术治疗脊柱侧凸患者57例,其中青少年特发性脊柱侧凸44例,先天性脊柱侧凸12例,马凡综合征1例.根据患者术前CT设计拟固定胸椎的椎弓根螺钉进钉点并用于指导术中的进钉点选择,术后根据螺钉是否突破椎弓根的皮质壁来判断置钉准确性.结果:全部患者共置入椎弓根螺钉591枚,胸椎417枚,腰椎174枚,术后530枚螺钉的轴线完全位于椎弓根皮质内,准确率为89.7%, 其中胸椎置钉准确率为86.8%(362,417).61枚螺钉的轴线突破椎弓根皮质壁,胸椎55枚,腰椎6枚.55枚偏置的胸椎椎弓根螺钉中52枚螺钉的实际进钉点与术前设计一致,其中19枚钉尖位于椎体内;3枚螺钉为术中实际进钉点选择失误,螺钉轴线突破椎弓根皮质壁的距离均不超过4mm.无脊髓、大血管及脏器损伤等严重并发症发生.结论:个体化选择胸椎椎弓根螺钉进钉点可提高脊柱侧凸患者胸椎置钉的准确率,减少术中进钉点选择失误所致的并发症.     

术中CT导航在脊柱侧凸后路胸椎椎弓根螺钉植入术中的应用

目的探讨术中CT导航在脊柱侧凸后路胸椎椎弓根螺钉植入术中的应用价值。方法回顾分析2009年10月-2011年12月行脊柱后路矫形融合术的46例胸弯脊柱侧凸患者临床资料,比较术中CT导航下(A组,21例)和传统C臂X线机下徒手(B组,25例)植入胸椎椎弓根螺钉的准确性和安全性。两组患者性别、年龄、脊柱侧凸类型、累及节段、主胸弯Cobb角等一般资料比较,差异均无统计学意义(P>0.05),具有可比性。A、B组各植入胸椎椎弓根螺钉273枚及308枚。采用Modi等方法,通过术中CT扫描对椎弓根螺钉位置分级,计算两组在上胸椎(T1～4)、中胸椎(T5～8)、下胸椎(T9～12)和整个胸椎(T1～12)的准确植钉率、安全植钉率和潜在危险植钉率。结果 A组整个胸椎的准确植钉率(93.4%)、安全植钉率(98.9%)均显著高于B组(83.8%、92.5%),潜在危险植钉率(1.1%)显著低于B组(7.5%),比较差异均有统计学意义(P<0.05)。两组上、中、下胸椎的准确植钉率、安全植钉率和潜在危险植钉率比较,差异均无统计学意义(P>0.05)。根据CT评估结果将潜在危险植钉重新植钉或去除。术后3 d根据神经系统体检评定两组均无神经功能缺失发生。结论与传统C臂X线机下徒手植钉技术相比,术中CT导航可提高胸椎椎弓根螺钉植入的准确性和安全性,可在术中发现危险螺钉并及时去除或修正,保障手术安全。     

青少年特发性胸椎侧凸患者胸椎椎弓根横径的分型及其临床意义

目的 探讨胸椎椎弓根横径的测量及分型在青少年特发性胸椎侧凸患者治疗中的临床意义.方法 对2008年10月至2009年7月收治的30例青少年特发性胸椎侧凸患者(侧凸组)和2008年8月至2009年7月于本院就诊的20例年龄匹配的非侧凸青少年患者(对照组)采用螺旋CT行胸椎连续扫描,在图像编档和通信系统(PACS)上逐层阅片,选择胸椎椎弓根显示最清楚的层面对椎弓根横径进行测量,并根据测量结果将其分为4型.分别对侧凸组凹凸侧和对照组左右侧椎弓根横径进行对比,并对侧凸组与对照组椎弓根分型的构成比进行分析.结果 两组患者胸椎椎弓根横径T1～4逐渐减少,T5～12逐渐增加.对照组同节段双侧胸椎椎弓根横径差异无统计学意义(P>0.05).侧凸组顶椎区凹侧的椎弓根横径明显小于凸侧,差异有统计学意义(P<0.05).侧凸组中4型椎弓根的比例明显高于对照组,1型椎弓根的比例低于对照组,差异均有统计学意义(P<0.05).结论 青少年特发性胸椎侧凸患者胸椎椎弓根横径常较小,术前应根据CT胸椎椎弓根形态制定置钉策略,以减少经胸椎椎弓根置入螺钉的并发症的发生.     

应用AIIMS分型评价脊柱侧后凸畸形胸椎椎弓根螺钉置入的研究

目的:探讨AIIMS(All India Institute of Medical Sciences)分型在评价脊柱侧后凸胸椎椎弓根螺钉置人中的应用价值.方法:1996年6月～2008年1月治疗脊柱侧后凸畸形患者73例,从中选取有完整术后CT资料者25例.其中男10例,女15例,年龄13～25岁,平均17.9岁.特发性脊柱侧后凸14例,先天性脊柱侧后凸5例,神经纤维瘤病伴脊柱侧后凸3例,脊髓空洞伴脊柱侧后凸2例,成骨不全性脊柱侧后凸1例.术前主胸弯冠状面Cobb角75°～1420°,平均93.6°;主弯后凸角50.5°～86.2°,平均65.1°.手术方式采用椎板间开窗法行胸椎椎弓根螺钉置入,后路主弯区附件松解和/或顶椎全脊椎切除,三维矫形和360°植骨融合术.术后根据AIIMS分型统计螺钉置人位置及相关并发症.结果:共置入218枚胸椎椎弓根螺钉,15例出现91枚螺钉偏置(41.74%).AIIMS分型中Ⅰ型(螺钉位置可接受型)占96.33%(210/218),Ⅱ型(螺钉位置不可接受型)占3.67%(8/218),无Ⅲ型(并发症型).术中在凹侧建立椎弓根通道时造成椎弓根骨折5例,未予置钉;术中硬膜撕裂4例,其中2例术后出现脑脊液漏,对症治疗5d后愈合;均无脊髓或大血管损伤.术后平均主胸弯冠状面Cobb角39.7°,平均矫正率57.6%,术后平均主弯后凸角35.5°,平均矫正率45.5%.随访1～5年,平均3.1年,冠状面和矢状面平均矫正度未见明显丢失.结论:AIIMS分型能较全面地评价脊柱侧后凸畸形胸椎椎弓根螺钉置入后的位置和并发症情况,有一定临床应用价值.     

全椎弓根螺钉系统矫正特发性脊柱侧凸

[目的]探讨胸椎椎弓根螺钉的植入方法,总结钉棒系统矫正脊柱侧凸的效果.[方法]咬除进钉点骨皮质,以据术前测量的深度和旋转的程度,分别先后用1.5 mm、2.5 mm克氏针沿椎弓根方向钻孔,如阻力加大、克氏针弯曲,说明遇到骨皮质,调整进针方向.达到测定的深度停止进针,球形探子探查无误后改用锤子将导锥顺着制造的钉道小心缓慢击入,深度一致后,再次用球形探子探查,植入螺钉.[结果]胸椎椎弓根螺钉一次性植入成功率胸段97%(600/619),腰段99%(733/740).术后未出现脊髓损伤和神经功能障碍,无切口感染.术后冠状面平均矫正率73%.矢状面后凸Cobb's角(T1～T12)6°～30°,平均23°.旋转畸形矫正Ⅰ～Ⅱ度.103例平均随访4.9年,躯干平衡良好,无平背畸形,植骨融合良好,末次随访冠状面角度丢失率平均为3.7%,迟发性感染1例,螺钉断裂2例,均行内固定取出.[结论]克氏针制备螺钉钉道,是胸椎椎弓根螺钉植入的较好方法.钉棒结构具有良好的三维矫正控制力.全椎弓根螺钉系统矫正特发性脊柱侧凸效果良好.     

CT三维重建椎弓根钉导航系统在胸椎手术中的应用

目的探讨CT三维重建椎弓根钉导航系统的使用方法和临床效果。方法自2003年5月至2004年5月在15例(80枚)胸椎弓根钉植入手术中使用CT三维重建椎弓根钉导航系统,其中上胸椎30枚,中下胸椎50枚。男10例,女5例;年龄13～76岁,平均47岁。胸椎肿瘤切除后重建5例,胸椎爆裂骨折4例,胸椎黄韧带骨化2例,胸椎侧凸4例。记录手术中螺钉植入时间、出血量。术中使用“C”型臂X线机拍摄正侧位X线片,术后进行CT扫描以了解内固定位置情况。结果每枚椎弓根钉从注册到植入完毕平均需要15min(10～20min)。术中出血量:胸椎肿瘤切除后重建平均1200ml,胸椎爆裂骨折后路固定平均800ml,胸椎黄韧带骨化切除平均300ml,胸椎侧凸平均500ml。椎弓根钉位置根据Andrew椎弓根螺钉CT位置分级标准进行分级,术后CT扫描显示80枚胸椎椎弓根钉中,位置Ⅰ级76枚(96%),Ⅱ级(突破椎弓根皮质≤2mm)2枚,Ⅲ级(突破皮质>2mm)2枚。Ⅱ、Ⅲ级的椎弓根钉均偏向椎弓根外侧,但术后均无神经刺激症状。结论CT三维重建导航系统可为术者虚拟三维的椎弓根钉植入环境,使椎弓根钉按预期的路径准确植入,提高了胸椎椎弓根钉植入的安全性和准确性。     

个体化导航模板在胸椎椎弓根螺钉置入中的初步临床应用

目的:通过临床应用评价个体化导航模板辅助胸椎椎弓根螺钉置入的准确性和安全性。方法:2008年7月～2009年9月,对11例需要行胸椎椎弓根螺钉置入手术的患者(青少年特发性脊柱侧凸7例,先天性脊柱侧凸2例,胸椎结核后凸畸形1例,多发性胸椎骨折1例)术前根据CT三维重建图像利用计算机辅助设计及快速成型技术设计制作46个胸椎个体化导航模板,术中应用个体化导航模板辅助在T2～T12置入椎弓根螺钉92枚,术后CT扫描评价螺钉位置,记录有无与螺钉置入相关的并发症。结果:通过个体化导航模板辅助置入的92枚胸椎椎弓根螺钉中,83枚完全在椎弓根内,9枚穿破椎弓根壁(其中椎弓根内侧壁穿破2枚、椎弓根外侧壁穿破7枚),其中5枚螺钉因椎弓根宽度小于4mm(3.0～3.8mm)而采用椎弓根旁固定方法(椎弓根螺钉轻度穿破椎弓根外侧壁经胸肋关节内侧进入椎体),椎弓根壁非故意穿破率为4.3%,置钉准确率为95.7%,所有穿破椎弓根壁的螺钉的穿出距离均小于2mm,螺钉位置可接受率为100%。无与螺钉置入有关的神经、血管、内脏损伤等并发症的发生。结论:个体化导航模板辅助胸椎椎弓根螺钉置入的置钉准确率高,安全、可行。     

脊柱侧凸胸椎椎弓根形态学分型

目的研究脊柱侧凸胸椎椎弓根的畸形发生率和畸形特征,并提出形态学分型系统。方法应用Siemens Somatom Sensation 64CT,对60例不同类型脊柱侧凸1440个胸椎椎弓根进行CT轴位扫描。在Lenke椎弓根分型的基础上对其进行量化和适当补充,将椎弓根形态分型为：A型（正常型）;B型（狭窄型）;C型（峡部硬化型）;D型（完全硬化型）,D-Ⅰ型（凹陷硬化型）,D-Ⅱ型（平直硬化型）;E型,椎弓根缺如。按照上述分型标准,对影像学资料进行测量、分析并分型。结果各种类型脊柱侧凸胸椎椎弓根形态分型A、B、C、D-Ⅰ、D-Ⅱ及E型分别占62.12%、24.72%、5.94%、2.75%、3.18%及1.29%,胸椎椎弓根的畸形发生率为37.88%。各种类型脊柱侧凸间胸椎椎弓根的畸形发生率差异有统计学意义（P〈0.05）,其中神经纤维瘤病性脊柱侧凸胸椎椎弓根的畸形发生率高达60.83%。结论各种类型的脊柱侧凸普遍存在胸椎椎弓根畸形,以狭窄型较为常见。     

What is the Difference in Morphologic Features of the Thoracic Pedicle Between Patients With Adolescent Idiopathic Scoliosis and Healthy Subjects? A CT-based Case-control Study

Background

Describing the morphologic features of the thoracic pedicle in patients with adolescent idiopathic scoliosis is necessary for placement of pedicle screws. Previous studies showed inadequate reliability owing to small sample size and heterogeneity of the patients surveyed.

Questions/Purposes

To use CT scans (1) to describe the morphologic features of 2718 thoracic pedicles from 60 female patients with Lenke Type 1 adolescent idiopathic scoliosis and 60 age-, sex-, and height-matched controls; and (2) to classify the pedicles in three types based on pedicle width and analyze the distribution of each type.

Methods

A total of 2718 pedicles from 60 female patients with Lenke Type 1 adolescent idiopathic scoliosis and 60 matched female controls were analyzed via CT. All patients surveyed were diagnosed with adolescent idiopathic scoliosis, Lenke Type 1, at the First Affiliated Hospital of Sun Yat-sen University, and all underwent pedicle screw fixation between January 2008 and December 2013 with preoperative radiographs and CT images on file. We routinely obtained CT scans before these procedures; all patients who underwent surgery during that period had CT scans, and all were available for analysis here. Control subjects had CT scans for other clinical indications and had no abnormal findings of the spine. The control subjects were chosen to match patients in terms of age (15 ± 2.6 years versus 15 ± 2.6 years) and sex. Height of the two groups also was matched (154 ± 9 cm versus 155 ± 10 cm; mean difference, −1.06 cm; 95% CI, −1.24 to −0.81 cm; p < 0.001). Pedicle width and length were measured from T1 to T12. The thoracic spine was classified in four regions: apical vertebra in the structural curve (AV-SC), nonapical vertebra in the structural curve (NAV-SC), apical vertebra in the nonstructural curve (AV-NSC), and nonapical vertebra in the nonstructural curve (NAV-NSC). Pedicles were classified in three types: pedicle width less than 2 mm as Type I, 2 mm to 4 mm as Type II, and greater than 4 mm as Type III. Types I and II were defined as dysplastic pedicles. Paired t test, independent samples t test, one-way ANOVA, followed by Bonferroni’s post hoc test and chi-square or Fisher’s exact tests were used for statistical comparisons between patients and controls, as appropriate.

Results

No difference was found between pedicle width on the convex side (PWv) and in controls (PWn), but pedicle width on the concave side (PWc) (4.99 ± 1.87 mm) was found to be narrower than PWv (6 ± 1.66 mm) and PWn (6 ± 1.45 mm). The variation degree of pedicle width (VDPW) was greatest in the AV-SC region (34% ± 37%), in comparison to AV-NSC (20% ± 25%) (mean difference, 14%; 95% CI, 1.15%–27%; p = 0.025), NAV-SC (17% ± 30%) (mean difference, 17%; 95% CI, 7%–27%; p < 0.001), and NAV-NSC (11% ± 24%) (mean difference, 24%; 95% CI, 13%–34%; p < 0.001). Dysplastic pedicles appeared more in patients with adolescent idiopathic scoliosis (22%; 293 of 1322) compared with controls (13%; 178 of 1396) (odds ratio [OR] = 0.51; 95% CI, 0.42–0.63; p < 0.001). In patients with adolescent idiopathic scoliosis, they commonly occurred on the concave side 34% (228 of 661) and on the AV-SC region (32%; 43 of 136).

Conclusions

Pedicle width on the concave side was narrower than pedicle width on the convex side and pedicle width in healthy control subjects. The apical vertebra in the structural curve was the most variegated region of the curve with the highest prevalence of dysplastic pedicles.

Clinical Relevance

Our study can help surgeons perform preoperative assessments in females with adolescent idiopathic scoliosis, and with preoperative and intraoperative management for difficult pedicle screw placement. In particular, our results suggest that surgeons should exercise increased vigilance when selecting pedicle screw dimensions, especially in the concave aspect of the mid-thoracic curve, to avoid cortical breeches. Future studies should evaluate other Lenke types of adolescent idiopathic scoliosis, and males with adolescent idiopathic scoliosis.

     

Thoracic pedicle screw placement guided by computed tomographic measurements.

Cadaveric pedicle screw placement guided by the measurements from axial computed tomography (CT) scans in the thoracic spine was assessed in this study. Axial CT scans were performed on four cadaveric thoracic spines, and the measurements included the pedicle transverse angle, inner pedicle width, and distance between the midline of the vertebra and the pedicle axis on the dorsal aspect of the lamina. With utilization of the data from CT scans, screws were directly placed into the thoracic pedicle from T1 to T10. Screw penetration of the pedicle was determined by gross examination. The results showed that the largest pedicle transverse angle was found at the levels of T1-2, and the smallest occurred at the T3 through T8 levels. The value of the pedicle inner width was quite different between specimens with a minimum of 3.0 mm at T4 and a maximum of 9.2 mm at T10. Gross examination of the pedicle showed that 13 (16.3%) of 80 screws penetrated the pedicle wall, with a Grade I penetration in 11 pedicles and a Grade II penetration in 2 pedicles. Screw penetration of the medial wall was found in four pedicles and penetration of the lateral wall was noted in nine pedicles. No screw penetration of the superior and inferior walls of the pedicle was identified in any of the four specimens. Thoracic pedicle screw placement guided by the measurements from axial CT scans significantly reduced the incidence of pedicle penetration. Axial CT measurements of the pedicle inner diameter and transverse angle as well as the starting point for screw insertion are recommended if pedicle screw fixation is intended in the thoracic spine.     

Morphometric analysis using multiplanar reconstructed CT of the lumbar pedicle in patients with degenerative lumbar scoliosis characterized by a Cobb angle of 30° or greater

Object Although the anatomy of the thoracic pedicle in adolescent idiopathic scoliosis is well known, that of the lumbar pedicle in degenerative lumbar scoliosis is not. The morphometric differences between the pedicles on the concave and convex sides can result in an increased risk of malpositioned pedicle screws. The purpose of this study was to analyze the lumbar pedicle morphology in degenerative lumbar scoliosis using multiplanar reconstructed CT. Methods The study group comprised 16 consecutive patients (1 man and 15 women, mean age 70.9 ± 4.5 years) with degenerative lumbar scoliosis characterized by a Cobb angle of at least 30° who underwent preoperative helical CT scans. The CT data in DICOM format were reconstructed, and the following parameters were measured for each pedicle inside the curves: the inner cortical transverse pedicle width (TPWi) and outer cortical transverse pedicle width (TPWo) and axial angle, all on an axial plane, and the inner cortical minimum pedicle diameter (MPDi) and outer cortical minimum pedicle diameter (MPDo) and cephalocaudal inclination of the pedicle, all on the plane perpendicular to the pedicle axis. The cortical thickness and cortical ratio of the pedicles on the axial plane and the plane perpendicular to the pedicle axis were calculated. Data were obtained for a total of 124 pedicles; L-1, 26 pedicles in 13 patients; L-2, 32 pedicles in 16 patients; L-3, 32 pedicles in 16 patients; L-4, 28 pedicles in 14 patients; and L-5, 6 pedicles in 3 patients. Results Among the target vertebrae, the TPWi, MPDi, and MPDo were significantly smaller and the axial angle was significantly larger on the concave side than on the convex side (TPWi, 6.37 vs 6.70 mm, p < 0.01; MPDi, 5.15 vs 5.67 mm, p < 0.01; MPDo, 7.91 vs 8.37 mm, p < 0.05; axial angle, 11.79° vs 10.56°, p < 0.01). The cortical ratio of the pedicles was larger on the concave side than on the convex side (on the axial plane, 0.29 vs 0.26, p < 0.05; on the plane perpendicular to the pedicle axis, 0.36 vs 0.32, p < 0.01). These differences were most evident at L-4. Conclusions This study demonstrated lumbar pedicle asymmetry in degenerative lumbar scoliosis. The authors speculate that these asymmetrical changes were attributed to the remodeling caused by axial load imbalance and the limited space available for pedicles on the concave side. On the concave side, because of the narrower pedicle diameter and larger axial angle, surgeons should carefully determine screw size and direction when inserting pedicle screws to prevent possible pedicle wall breakage and neural damage.     

Pedicle morphology in thoracic adolescent idiopathic scoliosis: is pedicle fixation an anatomically viable technique?

STUDY DESIGN: A radiographic study of thoracic pedicle anatomy in a group of adolescent idiopathic scoliosis (AIS) patients. OBJECTIVE: To investigate the anatomic constraints of the thoracic pedicles and determine whether the local anatomy would routinely allow pedicle screw insertion at every level. SUMMARY OF BACKGROUND DATA: In spite of the clinical successes reported with limited thoracic pedicle screw-rod constructs for thoracic AIS, controversy exists as to the safety of this technique. MATERIAL AND METHODS: Twenty-nine patients with right thoracic AIS underwent preoperative thoracic CT scans and plain radiographs. Anatomic parameters were measured from T1 to T12. RESULTS: Information on 512 pedicles was obtained. The transverse width of the pedicles from T1 through T12 ranged from 4.6-8.25 mm. The medial pedicle to lateral rib wall transverse width from T1 through T2 ranged from 12.6 to 17.9 mm. Measured dimensions from the CT scans showed the actual pedicle width to be 1-2 mm larger than would have been predicted from the plain radiographs. Age, Risser grade, curve magnitude, and the amount of segmental axial rotation did not correlate with the morphology or size of the thoracic pedicles investigated. In no case would pedicle morphology have precluded the passage of a pedicle screw. CONCLUSION: Based on the data identified in this group of adolescent patients, it is reasonable to consider pedicle screw insertion at most levels and pedicle-rib fixation at all levels of the thoracic spine during the treatment of thoracic AIS.     

寰椎“椎弓根”三维CT重建测量及分型的临床意义

目的:研究通过三维CT重建测量正常状态下寰椎"椎弓根"形态及其相关解剖学数据,对其进行分类并探讨其临床意义。方法:选取150例正常成人志愿者,年龄18～52岁(平均32.3岁),排除相关上颈椎疾患,尤其局部骨性增生明显者。对其寰枢椎进行螺旋CT扫描,在CT三维多平面重建下,取经枢椎下关节突中点矢状线延长线与寰椎椎动脉沟底部下2mm处后弓的交点为A点,同时建立通过椎动脉沟底部下2mm处的寰椎横切面图,取寰椎后弓移行为侧块处椎动脉孔内壁与椎管外壁连线的中点为B点,AB连线的延长线与寰椎前弓的交点为C点,AC连线即为寰椎椎弓根钉道。取经AC连线建立寰椎椎弓根通道的矢状面切图。测量寰椎双侧椎弓根各主要解剖参数:寰椎椎弓根的上倾角,椎动脉沟底椎弓根厚度(H1),寰椎椎弓根最大厚度;根据H1数值的大小分型,探讨各分型与椎弓根钉选择的相符性。结果:钉道椎动脉沟底处骨质厚度为4.10±1.17mm。根据H1数值的大小,以直径4.00mm和3.50mm的螺钉为参照,分为四型:正常型:H1>4.00mm(92例,61.3%);相对狭窄型:3.500.05)。正常型和相对狭窄型建议采用"椎弓根"螺钉技术。狭窄型和无椎弓根型者采用侧块螺钉技术。结论:三维CT重建能够准确提供寰椎椎弓根的解剖学形态、解剖学参数,根据寰椎椎动脉沟处骨质的高度进行分类,可以较好的指导寰椎后路"椎弓根"及侧块螺钉固定技术的选择及螺钉直径的选择。     

Pedicle screw diameter selection for safe insertion in the thoracic spine

Objective

Many thoracic pedicles are too small for the safe acceptance of a transpedicular screw. However, few studies have so far reported on the methods to select a proper pedicle screw size and to confirm the morphologic changes for such a small thoracic spine pedicle. The objective of this work was to determine the potential limits of a pedicle screw diameter for transpedicular screw placement in the thoracic spine.

Methods

T2–T9 vertebrae from eleven patients that underwent posterior thoracic instrumentation with the use of fluoroscopically assisted insertion method were analyzed. The outcome measures were the pedicle widths, the gap between the outer pedicle width and the selected pedicle screw diameter, and the penetration length of the pedicle screws using computed tomography. The screws were distributed into two groups according to the pedicle width and screw diameter, and the screw perforation rate of the two groups was compared. The relationships of the gap and the distance of the screw penetration were compared and investigated in regard to the pedicle screw diameter selection.

Results

A total of 16 screws demonstrated a smaller diameter than the inner pedicle widths, while 22 screws had a larger diameter than the inner pedicle widths. One screw (6.3%) perforated the pedicle cortex in the smaller screw group, and twelve screws (54.5%) perforated the pedicle cortex in the larger screw group (P?=?0.006). A linear regression analysis in the larger screw group revealed that when the gap was less than 0.5?mm, a risk of a pedicle wall violation was observed.

Conclusions

When the screws with a larger diameter than the inner pedicle width are selected, the screw perforation rate increases. Therefore, the size of the screw diameter must be at least 0.5?mm less than the outer pedicle width to ensure safe transpedicular screw placement.     

Internal morphology of human cervical pedicles

STUDY DESIGN: The internal architecture of cervical spine pedicles was investigated by thin sectioning and digitization of radiographic images. OBJECTIVES: To provide quantitative information on the internal dimensions and cortical shell thicknesses of the middle and lower cervical pedicles. SUMMARY OF BACKGROUND DATA: Although there have been a number of studies presenting data on the external dimensions of the cervical pedicle, little is known regarding its internal architecture and cortical shell thickness along the pedicle axis. METHODS: Twenty-five human cervical vertebrae (C3-C7) were secured to a thin-sectioning machine to produce three 0.7-mm-thick pedicle slices along its axis. Plain radiographs of the pedicle slices were scanned and digitized to facilitate measurement of the internal dimensions. Computer software was specifically developed to determine the external dimensions (i.e., pedicle height and width) and the internal dimensions (i.e., cortical shell thicknesses of the superior, inferior, lateral, and medial walls and the cancellous core height and width) of cervical pedicles. RESULTS: Superior and inferior wall cortical thicknesses of pedicle thin slices were similar, whereas the lateral wall cortical thickness was significantly smaller than the medial wall thickness. The medial cortical shell (average value range: 1.2-2.0 mm) was measured to be 1.4 to 3.6 times as thick as the lateral cortical shell (average value range: 0.4-1.1 mm). When medial and lateral cortical thicknesses were normalized for external dimensions, the combined cortical shell thickness was thinnest at C7 (average value range: 18. 6-25.6% of the external width), and this result was statistically significant when compared with other vertebral levels. CONCLUSIONS: The cervical pedicle is a complex, three-dimensional structure exhibiting extensive variability in internal morphology. Characteristics of the cervical pedicle at different spinal levels must be noted before transpedicular screw fixation.     

Comparison of differences and random errors in pedicle diameter measurements between MRI and CT: observational study of 315 pedicles in Lenke type 1 adolescent idiopathic scoliosis patients

BACKGROUND CONTEXTPosterior spinal fusion with pedicle screws is commonly used for the treatment of adolescent idiopathic scoliosis (AIS). To reduce radiation exposure, methods other than computed tomography (CT) are desirable for preoperative determination of pedicle diameter.PURPOSEInvestigate the differences between magnetic resonance imaging (MRI) and CT measurements of pedicle diameter.STUDY DESIGNCross-sectional research.PATIENT SAMPLETwenty-one AIS Lenke type 1 patients (19 female and 2 males, mean age at surgery: 15.4 years) who underwent posterior spinal fusion between April 2009 and October 2019.OUTCOME MEASURESGap between CT and MRI pedicle diameters.METHODSThe inner and outer diameters of the right and left pedicles from T1 to L3 were measured separately by two spine surgeons for statistical comparisons.RESULTSThe respective minimum and maximum CT-MRI values were -3.7 mm and 4.7 mm for inner diameter and -4.6 mm and 5.3 mm for outer diameter. Regarding inter-examiner error, the probability of a 2 mm difference in measurement was less than 5% for both modalities. The probability of a 1 mm difference was also less than 5%, and that of a 3 mm or more difference was 2.1% for the inner diameter and 2.9% for the outer diameter. Whereas low body weight was significantly associated with measurement differences, pedicle laterality was not.CONCLUSIONSMRI does not have the reliability to measure pedicle size in AIS patients at present. However, with advancements in image processing technology, the accuracy of pedicle size measurement by MRI may soon improve.