T4椎弓根-肋骨复合体横纵径的相关测量

目的:测量T4椎弓根-肋骨复合体的横纵径相关数据并探讨其意义。方法:12例随机成人胸椎,男7例,女5例;平均年龄23岁(19～28岁)。采用病例自身对照分组,即同一病例、同侧T4椎弓根与椎弓根-肋骨复合体对照。所用设备为GE公司Lightspeed16排螺旋CT,自T3至T5行CT扫描及三维重建。测量参数:椎弓根横径、椎弓根-肋骨复合体横径、椎弓根纵径、椎弓根-肋骨复合体纵径、椎弓根-肋骨复合体重叠纵径。结果:T4椎弓根-肋骨复合体中的椎弓根与肋骨部分重叠,椎弓根横径与椎弓根-肋骨复合体的横径比较差异有统计学意义(P<0.05);椎弓根纵径与椎弓根-肋骨复合体纵径间比较差异无统计学意义(P>0.05),椎弓根-肋骨复合体重叠纵径与椎弓根纵径或复合体纵径间差异均有统计学意义(P<0.05)。结论:T4椎弓根-肋骨复合体中椎弓根与肋骨是部分而非完全重叠,且椎弓根或复合体的纵径均不能等同于重叠纵径。     

胸椎经"椎弓根-肋骨间"螺钉与椎弓根螺钉固定的抗拔出力比较

目的比较胸椎经"椎弓根-肋骨间"螺钉与椎弓根螺钉固定的抗拔出力.方法5例新鲜尸体脊柱(T6～T10)标本,自椎间盘、小关节及上位椎体下肋椎关节处分解为单椎体(附带双侧肋骨)25个.根据配对随机分组的原则,随机选取椎体一侧作椎弓根螺钉固定组,另一侧则为配对的"椎弓根-肋骨间"螺钉固定组,共组成25个配对组.同组中"椎弓根-肋骨间"螺钉长度较椎弓根螺钉长10mm,直径与椎弓根螺钉相同.将25组的50个螺钉分别进行拔出测试(5mm/min的速度垂直方向拔出).结果"椎弓根-肋骨间"螺钉的抗拔出力为423.1±198.7N;椎弓根螺钉的抗拔出力为783.3±199.5N.前者的抗拔出力显著小于后者(P＜0.01).结论"椎弓根-肋骨间"螺钉的力学性能不及椎弓根螺钉,建议仅将前者作为后者的一种补充,特别是在无法完成椎弓根螺钉置入的部分胸椎节段.     

胸椎椎弓根-肋骨单元与椎弓根的CT测量

目的:比较经胸椎椎弓根-肋骨单元(pedicle rib unit;PRU)置钉与传统经椎弓根置钉技术的相关径线;为临床应用提供依据.方法:对30例患者脊柱T1～T10节段进行薄层CT扫描;层厚为1mm;选择有完整PRU结构的CT横断面图像进行以下指标测量:(1)PRU宽度(PRU-W);椎弓根宽度(PW);(2)PRU钉道长度(PRU-L);椎弓根钉道长度(PL);(3)PRU中轴与矢状面夹角(PRU-A);椎弓根中轴与矢状面夹角(PA);(4)经PRU置钉的安全角度范围(△A).结果:PRU-W和PW均以T5最小;以T1为最大;由T1至T5逐渐减小;由T5至T10逐渐增大.PRU-L和PL以T1为最小;以T10为最大;由T1至T10逐渐增大.PRU-A和PA以T1为最大;以T10最小;由T1至T10逐渐缩小.PRU-L与PL、PRU-W与PW间均有显著性差异(P＜0.01).PRU-W、PRU-L在男女之间差异亦有统计学意义(P＜0.01).PRU置钉的安全角度范围△A为20°～30°.结论:胸椎PRU的横径、钉道长度均较同节段的椎弓根大;经PRU可置入更粗更长的螺钉;有更大的内倾角;安全置钉角度范围也较大.     

胸椎弓根壁破裂3种补救置钉方法的生物力学研究

目的对人体标本胸椎弓根壁破裂3种补救置钉方法进行生物力学对比。方法选取5具青壮年尸体共30个胸椎体60个椎弓根,分为强化空心钉(HSS)组(15个椎弓根)、皮质骨通道螺钉(CBTS)组(30个椎弓根)和椎弓根-肋骨单元钉(PRUS)组(15个椎弓根),制成椎弓根内侧壁破裂模型。完成置钉后分别进行螺钉轴向抗拔出力实验,比较最大轴向抗拔出力、刚度、能量吸收值。结果 HSS组、CBTS组、PRUS组螺钉最大轴向抗拔出力分别为(973. 00±23. 88) N、(647. 13±21. 89) N、(613. 00±23. 25) N,差异有统计学意义(P 0. 05)。HSS组、CBTS组、PRUS组刚度分别为(284. 61±14. 77) N/mm、(218. 82±11. 84) N/mm、(194. 72±13. 06) N/mm,差异有统计学意义(P 0. 05)。HSS组、CBTS组、PRUS组能量吸收值分别为(2. 77±0. 13) J、(1. 41±0. 40) J、(1. 31±0. 57) J,HSS组与CBTS组、PRUS组比较差异有统计学意义(P 0. 05),但CBTS组与PRUS组比较差异无统计学意义(P 0. 05)。结论在胸椎弓根壁破裂情况下,HSS、CBTS、PRUS 3种补救置钉均能够提供内固定稳定,HSS内固定稳定性最大,CBTS次之,PRUS最小。     

上胸椎前路逆向椎弓根螺钉内固定技术的可行性研究

【摘要】 目的：通过放射解剖学研究及标本上的模拟手术操作来验证上胸椎（T1~T4）前路逆向椎弓根螺钉内固定技术的可行性及安全性。方法：在放射科CT数据库中选取40例层厚为0.625mm的正常上胸椎薄层CT扫描数据（男20例,女20例,年龄18～68岁,平均39.7岁）,对数据进行MPR重建,在每侧椎弓根轴心上选取其横切面和矢状面进行观察和测量,测得每侧椎弓根的横径、高度、横切面进钉点距离、进钉角度、矢状面进钉点距离、进钉角度、钉道长度,对所得数据进行统计学处理。选取10具（男5例、女5例,年龄不详）完整的成人上胸椎防腐标本（包括C7～T6）,外观无畸形和破损,完整保留T1～T4两旁肋椎关节及椎旁软组织,于椎体前方逆向置入椎弓根螺钉,通过X线透视、CT扫描、剖面观察、测量,参照Rao等的椎弓根螺钉穿破分级标准对置钉优良率进行评测。结果：T1～T4椎弓根横径逐渐减小8.14～3.47mm;椎弓根高度逐渐增大6.89～10.29mm;横切面进钉角度逐渐减小32.96°～11.64°;横切面进钉点距离逐渐增大1.80～5.50mm;矢状面进钉角度逐渐增大104.95°～115.74°;矢状面进钉点距离逐渐增大5.95～8.76mm;钉道长度32.95～35.96mm。T3、T4椎弓根横径过于细小,不适合逆向椎弓根螺钉的置入,但在T3、T4逆向置入椎弓根-肋骨复合体螺钉是可行的。T1、T2前路逆向椎弓根螺钉的规格为：直径4.0mm、长度35mm左右,T3、T4前路逆向椎弓根-肋骨复合体螺钉的规格为：直径5.0mm、长度35mm左右。在10具上胸椎标本上共置钉80枚,根据Rao等的椎弓根螺钉穿破分级标准,总体优良率达90%,其中椎弓根侧壁穿破小于2mm未造成脊髓压迫的共7枚;椎弓根内侧壁穿破距离在2～4mm的共有5枚,分别为T1椎体1枚,T3椎体1枚,T4椎体3枚,有不同程度脊髓压迫;椎弓根内侧壁穿破距离大于4mm的2枚,其中T2椎体1枚,T4椎体1枚,脊髓受压严重;T2椎体有1枚椎弓根外侧壁穿破。结论：T1、T2椎体前路逆向椎弓根螺钉内固定技术和T3、T4椎体前路逆向椎弓根-肋骨复合体螺钉内固定技术可达到双皮质固定的目的,但其安全性及临床实用性尚需进一步探讨。     

超声骨动力椎弓根寻路器的研制及其引导置钉的可行性研究

目的 :探讨自行研制的超声骨动力椎弓根寻路器辅助椎弓根螺钉置入的准确度及安全性。方法 :自行研制一种超声骨动力椎弓根寻路器,选择2具成年人脊柱标本(T1～L5节段),男性1具,年龄62岁,女性1具,年龄57岁,排除畸形、外伤及骨质疏松症等骨科疾病,将标本左侧椎弓根设置为实验组,通过超声骨动力椎弓根寻路器引导下置钉;右侧椎弓根设置为对照组,直视下徒手置钉。术中及术后即刻分别对两组标本行CT扫描,通过术中CT测量定位针长轴中线距椎弓根内外侧皮质距离;通过术后CT测量椎弓根螺钉穿出椎弓根皮质的距离并依据Neo法对置钉进行分级,统计两组精确置钉(0级置钉)、可接受置钉(Neo分级0级或1级)和不良置钉(Neo分级2级或3级)的情况。通过比较两组精确置钉率与不良置钉率上的整体差异,以及分别在上、中、下胸椎及腰椎的穿破皮质螺钉(Neo分级1、2、3级螺钉)的差异,评估两组间置钉精确性与安全性的差异。结果:两组各置入34枚定位针。实验组与对照组的定位针在上胸椎距皮质骨最小距离分别为2.77mm±1.05mm和0.59±2.31mm,中胸椎为1.97±1.01mm和0.98±1.70mm,下胸椎为3.02±0.93mm和2.53±0.83mm,腰椎为4.14±1.04mm和3.80±0.59mm。实验组有6枚定位针存在穿出的风险,对照组有14枚存在穿出的风险。在置钉方面,实验组与对照组的精确置钉率分别为82.36%和58.82%,可接受置钉率分别为97.06%和82.36%,不良置钉率分别为2.94%和17.64%。在所有穿破皮质螺钉中,实验组有1枚位于上胸椎(1级),2枚位于中胸椎(1级、2级各1枚),2枚位于下胸椎(1级2枚),1枚位于腰椎(1级);而对照组有6枚位于上胸椎(1级2枚、2级2枚、3级2枚),5枚位于中胸椎(1级3枚、2级1枚、3级1枚),3枚位于下胸椎(1级)。实验组在胸腰椎精确置钉率、可接受置钉率上明显高于对照组,而在不良置钉率上明显低于对照组,且差异均具有统计学意义(P0.05)。实验组与对照组在上胸椎节段(T1～T4)穿破皮质螺钉比率存在统计学差异(P0.05),而在中下胸椎及腰椎无统计学差异(P0.05)。结论:与徒手置钉相比,超声骨动力椎弓根寻路器引导下置钉在胸腰椎节段具有较高的准确性与安全性。     

椎弓根劈裂对内固定稳定性影响的生物力学研究

目的探讨椎弓根螺钉内固定时椎弓根皮质劈裂对骨折椎体稳定性的影响。方法取新鲜成年羊胸腰椎脊柱标本(T14~L2)20具,随机分为A、B两组。在A组和B组标本的L1椎体上分别制作单椎体压缩骨折模型,再单独对B组标本T14胸椎任意一侧的椎弓根行外侧(1/4~1/2)切除,作为椎弓根劈裂椎体骨折模型。然后对A、B两组分别置钉,进钉深度为钉道全长。标本模型固定后,在HY-3080微机控制电子万能材料试验机上,以频率为1.5 Hz的载荷对两组标本模型行10 000次疲劳实验,分别测量疲劳实验后两组标本前屈、后伸、左侧弯、右侧弯4个方向运动范围的大小和疲劳实验后两组标本模型螺钉拔出力大小,并比较两组差异。结果疲劳实验后A组各个方向活动范围:前屈(1.81±0.14)mm,后伸(1.68±0.37)mm,左侧弯(4.08±0.41)mm,右侧弯(4.18±0.12)mm;B组各个方向活动范围大小:前屈(4.49±0.40)mm,后伸(3.72±0.51)mm,左侧弯(6.67±0.64)mm,右侧弯(6.73±0.58)mm;A组各个方向活动范围均小于B组(P0.01)。疲劳实验后A组螺钉最大拔出力为(252.34±51.27)N,B组螺钉最大拔出力为(115.50±36.74)N,最大拔出力A组大于B组(P0.01)。结论椎弓根皮质劈裂将严重影响骨折椎体内固定的稳定性。     

枢椎椎弓根螺钉进钉点及植钉方式的解剖研究

目的对成人尸体枢椎干骨标本进行解剖学测量,探索一种简便、精确的植钉方法,为临床枢椎椎弓根螺钉内固定提供解剖学依据。方法取60具完整且无畸形的成人尸体枢椎干骨标本,以椎弓根内、外侧缘与侧块交界处连线的中点作纵垂线,经横突后支与下关节突外侧缘交界处作水平线,两线交点偏外1~2 mm处为进钉点,经椎弓根植钉,分别测量椎弓根高度及宽度、最大进钉长度、钉道至椎管和横突孔最短距离、进钉角度等解剖参数,评估枢椎椎弓根螺钉植钉的可行性及安全性。结果椎弓根上缘、中部、下缘宽度分别为(7.35±0.89)、(5.50±1.48)、(3.97±1.01)mm,椎弓根高度为(9.94±1.16)mm。最大进钉长度为(25.91±1.15)mm,进钉方向与冠状面夹角为(26.95±1.88)°、与矢状面夹角为(22.81±1.61)°。钉道至椎管、横突孔的最短距离分别为(2.72±0.83)mm和(1.98±0.26)mm。结论分别经椎弓根内、外侧缘与侧块的交界处,以及经横突后支与下关节突外侧缘的交界处作为枢椎椎弓根进钉点坐标的定位标志进行植钉,在解剖形态学方面是安全、可行的。     

经胸椎椎弓根-肋骨途径置入螺钉安全角度的CT测量

目的：探讨胸椎T1～T10经椎弓根-肋骨途径置入螺钉的安全角度及变化规律。方法：选取156例正常成人的胸椎CT薄层扫描资料，其中男96例，女60例；年龄18～54岁，平均39岁。在胸椎CT片上测量T1～T10椎弓根-肋骨的横径、经椎弓根-肋骨途径置入的螺钉与矢状面的最小与最大安全成角及安全角度范围。结果：从T1～T4椎弓根-肋骨的横径逐渐减小．T5～T10逐渐增大：置钉安全角度范围T1与T2比较及T5～T10无显著性差异（P〉0．05），而T2与，T3及T4与T5比较均有显著性差异（P〈0．05），T1、T2置钉安全角度范围最大，T5～T10次之，T3、T4最小；男性与女性比较无显著性差异（P〉0．05）。结论：T1～T10胸椎的椎弓根-肋骨横径大小不同。经此途径置钉安全角度的大小亦不完全相同。     

椎弓根螺钉植入导向器的研制及体外应用研究

目的　分析自制椎弓根螺钉导向器提高椎弓根螺钉植入的准确性。　方法　根据椎弓根的解剖特点 ,研制椎弓根螺钉植入导向器。用多层螺旋 CT测量 2具胸椎标本 (T1 ～ T1 0 )椎弓根的三维定量解剖数据。依据其中轴的水平位角 (transverse section angle,TSA)和矢状位角 (sagittal section angle,SSA)值 ,调节导向器水平和矢状刻度盘角度。植入螺钉后拔出 ,用显影剂填充钉道。 CT测量显影钉道的 TSA和 SSA值。　结果　析因设计资料方差分析显示 ,椎弓根显影钉道的 TSA、SSA与其中轴的 TSA、SSA间差异无统计学意义 (P>0 .0 5 )。　结论　椎弓根螺钉导向器操作简便 ,其导向使钉道达到理想角度 ,能减少椎弓根穿破的发生。     

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.     

下颈椎椎弓根螺旋CT扫描的三维重建及测量

目的 评价应用多层螺旋CT扫描三维重建技术测量下颈椎椎弓根相关参数的可行性. 方法 8具成年男性颈椎标本经螺旋CT扫描后,把信息传送至随机工作站(Silicon Graphics O2),结合下颈椎榷弓根置钉的参数需求,进行三维重建[容积成像(VR)和多平面重组(MPR)]后测量椎弓根各个相关数据.然后对这些数据进行分析. 结果本组下颈椎椎弓根的外展角平均为42.02°±7.55°,C_7最小(35.63°±6.34°),C_4最大(46.94°±5.69°);头倾角平均为76.30°±12.01°,C_3最小(72.93°±6.57°),C,最大(81.27°±13.34°);入点至下关节缘距离平均为(11.23±1.78)mm,C_3最小[(10.54±1.25)mm],C_6最大[(12.05±1.40)mm];入点至侧块外缘距离各椎体相筹较大,平均为(2.65±1.21)mm,C_4最小[(1.69±0.81)mm],C_7最大[(3.74±0.99)mm];入点至椎体前缘距离各椎体差异较小,平均为(31.42±2.13)mm;椎弓根皮质骨高度平均为(8.43±1.30)mm,宽度半均为(5.54±1.26)mm;椎弓根松质骨高度平均为(3.69±1.19)mm,宽度平均为(2.67±1.15)mm;椎弓根皮质高度一般大于宽度,C_4内径最小,C_7内径最大. 结论 VR、MPR重建图像可满足椎弓根参数测量要求,其所测量的下颈椎椎弓根参数可满足经椎弓根手术的术前评估需求;下颈椎椎弓根变异较大.     

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.     

改良钉棒系统治疗垂直不稳定骨盆骨折的生物力学研究

目的 探讨改良钉棒系统治疗垂直不稳定型骨盆骨折,并分析其生物力学性质.方法 在8例尸体骨盆标本上造模成垂直不稳定型骨盆骨折,分别行TOS术式固定、骶髂螺钉固定、改良钉棒系统固定,检测1000 N载荷下骨盆刚度、骨折分离移位距离及局部应变改变.结果 骨盆标本骨折模型采用各种不同固定方式,经生物力学测试,改良钉棒系统在载荷1000 N下刚度(224.3±18.3)N/mm及骨折分离移位距离(1.98±0.24)mm,明显优于骶髂螺钉固定(169.10±17.60)、(8.08±0.71)mm,差异有统计学意义(P＜0.01),与TOS(233.20±12.90)、(1.62±0.31)mm比较,差异无统计学意义(P＞0.05).结论 改良钉棒系统是一种生物力学性能较好的治疗垂直不稳定型骨盆骨折的新方法.     

Minimally invasive cortical bone trajectory screws placement via pedicle or pedicle rib unit in the lower thoracic spine: a cadaveric and radiographic study

Purpose

To evaluate the feasibility of cortical bone trajectory (CBT) screws fixation via pedicle or pedicle rib unit in the cadaveric thoracic spine (T9–T12).

Methods

Computed tomography (CT) images of 100 patients are analyzed by multiplanar reconstruction. Ten cadaveric thoracic spines are used to insert 4.5 × 35.0 mm CBT screws at all levels from T9 to T12.

Results

Maximal screw length obtained by CT has a tendency to gradually increase from T9 (29.64 mm) to T12 (32.84 mm), and the difference reaches significant level at all levels except T9 versus T10 (P < 0.01). Maximal screw diameter increases from T9 (4.92 mm) to T12 (7.47 mm) and the difference reaches significant level among all levels (P < 0.01). Lateral angle increases from T9 (7.37°) to T12 (10.47°), and the difference reaches significant level among all levels except T11 versus T12. Cephalad angle from T9 to T12 are 19.03°, 22.10°, 25.62° and 27.50° (P < 0.01), respectively. The percentage of the inner and outer pedicle breakage are 2.5 and 22.5 %, respectively. The violation of lateral pedicle wall occurs at T9 and T10, especially for women at T9.

Conclusions

Both radiographic and cadaveric studies establish the feasibility of CBT screws placement via pedicle or pedicle rib unit in the lower thoracic spine (T9–T12). Furthermore, our measurements are also useful for application of this technique.

     

Evaluation of a transpedicular drill guide for pedicle screw placement in the thoracic spine

Insertion of pedicle screws in the thoracic spine is technically difficult and may lead to major complications. Although many computer-assisted systems have been developed to optimize pedicle screw insertion, these systems are expensive, not user-friendly and involve significant radiation from pre-operative computed tomographic (CT) scan imaging. This study describes and evaluates a transpedicular drill guide (TDG) designed to assist in the proper placement of pedicle screws in the thoracic spine. Pilot holes were made manually using the TDG in the thoracic spine (T1-T11) of three human cadavers before inserting 4.5-mm-diameter screws. CT scans followed by visual inspection of the spines were performed to evaluate the position of the screws. Five of 66 screws (7.6%) violated the pedicle wall: two (3.0%) medially and three (4.5%) laterally. The medial and lateral perforations were within 1 mm and 2 mm of the pedicle wall, respectively. The medial perforations were not at risk of causing neurological complications. No screw penetrated the superior or inferior pedicle wall. The TDG is easy to use and can decrease the incidence of misplaced thoracic pedicle screws. The TDG could be used as a complement to fluoroscopy in certain applications, especially for training surgeons.     

Pedicle morphology of the thoracic spine in preadolescent idiopathic scoliosis: magnetic resonance supported analysis

Although several studies have been reported on the adult vertebral pedicle morphology, little is known about immature thoracic pedicles in patients with idiopathic scoliosis. A total of 310 pedicles (155 vertebrae) from T1 to T12 in 10–14 years age group were analyzed with the use of magnetic resonance imaging and digital measurement program in 13 patients with right-sided thoracic idiopathic scoliosis. Each pedicle was measured in the axial and sagittal planes including transverse and sagittal pedicle width and angles, chord length, interpedicular distance and epidural space width on convex and concave sides of the curve. The smallest transverse pedicle widths were in the periapical region and the largest were in the caudal region. No statistically significant difference in transverse pedicle widths was detected between the convex and concave sides. The transverse pedicle angle measured 15.56° at T1 and decreased to 6.32° at T12. Chord length increased gradually from the cephalad part of the thoracic spine to the caudad part as the shortest length was seen at T1 convex level with a mean of 30.45 mm and the largest length was seen at T12 concave level with a mean of 41.73 mm. The width of epidural space on the concave side was significantly smaller than that on the convex side in most levels of the curve. Based on the anatomic measurements, it may be reasonable to consider thoracic pedicle screws in preadolescent idiopathic scoliosis.     

Complexity of the thoracic spine pedicle anatomy

Transpedicular screw fixation provides rigid stabilization of the thoracolumbar spine. For accurate insertion of screws into the pedicles and to avoid pedicle cortex perforations, more precise knowledge of the anatomy of the pedicles is necessary. This study was designed to visualize graphically the surface anatomy and internal architecture of the pedicles of the thoracic spine. Fifteen vertebrae distributed equally among the upper, middle, and lower thoracic regions were used. For the purpose of mapping surface anatomy, each pedicle was cleaned, spraypainted white, and marked with more than 100 fine points. Using an optoelectronic digitizer, three-dimensional coordinates of the marked points and three additonal points, representing a coordiate system, were digitized. A solid modeling computer program was used to create three-dimensional surface images of the pedicle. To obtain cross-sectional information, each pedicle was sectioned with a thin diamond-blade saw to obtain four slices, 1 mm in thcikness and 0.5 mm apart. The pedicle slices were X-rayed and projected onto a digitizer. The internal and external contours were digitized and converted into graphs by a computer. The pedicles exhibited significant variability in their shape and orientation, not only from region to region within the thoracic spine, but also within the same region and even within the same pedicle. These variations are extremely significant in light of current techniques utilized in transpedicular screw fixation in the thoracic spine. Information documenting the three-dimensional complexity of pedicle anatomy should be valuable for surgeons and investigators interested in spinal instrumentation.     

Placement of pedicle screws in thoracic idiopathic scoliosis: a magnetic resonance imaging analysis of screw placement relative to structures at risk

In posterior pedicle screw instrumentation of thoracic idiopathic scoliosis, screw malposition might cause significant morbidity in tems of possible pleural, spinal cord, and aorta injury. Preoperative axial magnetic resonace images (MRI) in 12 consecutive patients with right thoracic adolescent scoliosis, all with King type 3 curves, were analyzed in order to evaluate the relationship between the inserted pedicle screw position to pleura, spinal cord, aorta. Axial vertebral images for each thoracic level were scanned and the simulation of pedicle screw insertion was performed using a digital measurement programme. The angular contact value for each parameter regarding the pleura and spinal cord was measured on both sides of the curve. The aorta-vertebral distance was also measured. Aorta-vertebral distance was found to be decreasing gradually from the cephalad to the caudad with the shortest distance being measured at T12 with a mean of 1.2 mm. Concave-sided screws on T5–T9 and convex-sided screws on T2–T3 had the greatest risk to spinal cord injury. Pleural injury is most likely on T4–T9 segments by the convex side screws. T4–T8 screws on the concave side and T11–T12 screws on the convex side may pose risk to the aorta. This MRI-based study demonstrated that in pedicle instrumentation of thoracic levels, every segment deserves special consideration, where computer scanning might be mandatory in immature spine and in patients with severe deformity.