寰枢椎后路柔性固定的生物力学研究

目的分析细棒、PEEK棒固定对寰枢关节稳定性的影响。方法采用6具新鲜成人枕骨(occipital bone,Oc)~颈椎C4节段进行测试,模拟以下手术及固定状态:①完整状态;②损伤状态:枢椎齿状突II型骨折;③坚强固定:寰枢椎均采用普通椎弓根螺钉固定,直径3.5 mm钛棒连接;④PEEK棒:直径3.5 mm的PEEK棒连接;⑤细棒:直径2.0 mm钛棒连接。采用重复测量实验设计,在完整、损伤和不同的固定状态下,通过脊柱试验机对标本分别施加1.5 N·m的前屈/后伸、左/右侧弯和左/右轴向旋转的纯力偶矩。采用Optotrak三维运动测量系统连续采集标本运动,分析寰枢椎之间角度运动范围和中性区。结果采用直径3.5 mm的钛棒,2.0 mm的细棒以及3.5 mm的PEEK棒固定后,在前屈、后伸、侧弯和旋转方向上均显著减小了固定节段的运动范围(P<0.05)。直径3.5 mm和2.0 mm的棒固定后的运动范围,在各个方向上无显著性差异。PEEK棒固定的运动范围仅在侧弯方向上大于坚强固定(P=0.005),其他方向无显著性差异。3种固定方式在屈伸、侧弯和旋转方向上均显著减小了固定节段的中性区(P<0.05)。各种固定方式之间相比较,无显著性差异(P>0.05)。结论在寰枢关节采用直径2.0 mm的细棒固定,与坚强固定的稳定性相当。采用直径3.5 mm的PEEK棒固定,在前屈、后伸、旋转方向上与坚强固定的稳定性相当,在侧弯方向上弱于坚强固定。     

后路枕骨髁螺钉技术研究进展

正枕骨、寰椎和枢椎共同构成了枕颈部活动的结构功能单位,即枕颈交界区~([1-2])。炎症、创伤、肿瘤及畸形等因素会导致枕颈交界区失稳,从而引起颈脊髓或神经根的损伤、麻痹及难以忍受的疼痛,甚至危及生命~([3-4])。后路内固定融合技术是治疗枕颈部失稳的重要手段,目前常用术式为枕骨螺钉技术,该技术较钢丝固定技术有更好的生物力学稳定     

Subdental synchondrosis and anatomy of the axis in aging: a histomorphometric study on 30 autopsy cases

During skeletal development the two ossification centers of the odontoid process are separated from the corpus of the axis by a subdental synchondrosis. This synchondrosis is thought to close and disappear spontaneously in adolescence although this has never been studied in detail. The basis of the dens is of clinical relevance as type II dens fractures are located here. To characterize the morphological architecture of the axis with particular attention to the subdental synchondrosis, the complete axis was harvested from thirty age-matched and gender-matched patients of the three different age groups at autopsy. The subdental synchondrosis and the bone structure of the dens, the basis of the dens and the body of C2 were analyzed by radiography, histology and quantitative histomorphometry. At the macroscopic level the persistency of the subdental synchondrosis in the adult cervical spine was detected in 87% (26 of 30) of the specimens. Histomorphometry revealed a residual disc blastema with an average size of 25.8% of the sagittal depth of the basis of the dens at this level. Bony integration of the synchondrosis was poor throughout all ages. Histologically a cartilaginous matrix composition of the subdental synchondrosis persisted throughout all groups. The trabecular microarchitecture demonstrated a significant reduction of bone volume and trabecular number as well as an increased trabecular separation within the basis of the dens as compared to the corpus or the dens of C2. This histomorphometric data regarding a poor integration of the synchondrosis into the trabecular network and the reduced bone mass within the basis of the dens might offer a previously underestimated explanation for the occurrence of type II dens fractures and their association with pseudoarthrosis, respectively.Matthias Gebauer and Christian Lohse contributed equally to this study and therefore share first authorship.     

C2椎弓根拉力螺钉选择性治疗Hangman骨折

目的探讨C_2椎弓根拉力螺钉治疗Hangman骨折的适应证,并评估其疗效。方法1998年2月～2000年12月共收治Hangman骨折患者22例。经颅骨牵引有10例骨折获得解剖复位但不稳定,对其中椎体结构完整的8例进一步施行了3.5mmC2椎弓根拉力螺钉内固定。男6例,女2例;年龄18～42岁,平均28.2岁。Levine-EdwardsⅠ型5例,Ⅱ型2例,Ⅱa型1例。脊髓功能FrankelD级2例,E级6例。患者全麻后俯卧于预制好的头-颈-胸石膏床腹片上,取后正中切口,暴露C1～C3后方结构。取C2侧块中点为进钉点,根据C2椎弓根的内缘和上缘走行确定进钉方向,一般为向头端倾斜25°～30°,向中线倾斜30°～35°。应用测深器确定螺钉长度,一般为25～30mm。所有操作均在“C”型臂X线机透视下完成。结果手术平均时间70min。未发现术后的早期和晚期并发症,神经功能恢复正常,所有骨折均在术后3个月愈合,颈椎活动范围接近正常,未出现C2,3的脱位和拉力螺钉的松动。结论C2椎弓根拉力螺钉技术可使Hangman骨折获得良好的即刻复位,通过骨块间加压恢复C2,3节段的稳定性。其适应证应限于骨折可复位的病例。     

枢椎后路侧块螺钉与椎弓根螺钉固定强度的生物力学评价

目的评价单皮质和双皮质枢椎侧块螺钉与枢椎椎弓根螺钉的固定强度,为临床选择枢椎后路螺钉的固定方式提供生物力学依据。方法利用12具新鲜尸体枢椎标本,进行单皮质和双皮质的椎弓根螺钉或侧块螺钉固定,测试比较其螺钉拔出强度。结果双皮质枢椎椎弓根螺钉的拔出力量最大,为(1 726.5±433.3)N;单皮质枢椎椎弓根螺钉〔(1 279.9±432.0)N〕与双皮质枢椎侧块螺钉〔(1 054.8±411.3)N〕之间差异无统计学意义;单皮质枢椎侧块最小为(689.4±128.0)N。结论枢椎后路螺钉固定宜首选椎弓根螺钉,侧块螺钉可作为补充固定技术,且以双皮质骨固定为宜。     

Atlas钛缆固定上颈椎的解剖与临床

目的: 观察寰椎后弓和枢椎椎板的形态学特征, 以更为安全、方便地开展颈后路寰枢椎Atlas钛缆固定术。方法: 观察 100套寰椎后弓和枢椎椎板的形态学特点并进行解剖学测量, 设计引导钛缆穿绕的特殊的器械, 并应用于 17例上颈椎损伤患者的手术操作。结果:(1) 寰椎后弓较纤弱, 横截面呈扇形, 内侧面从后上方向内下方倾斜; 枢椎椎板较粗大, 上窄下宽, 内侧面基本垂直, 内侧面下缘多形成一骨嵴; (2) 寰椎后弓的引导器要求头端折弯, 枢椎椎板引导器要求头端圆钝; (3) 17例患者手术操作均安全、顺利完成, 无脊髓损伤等并发症发生。结论: 根据寰椎后弓和枢椎椎板的形态学特征, 穿绕钛缆时宜自上向下操作; 采用专用的引导器使得颈后路寰枢椎Atlas钛缆固定术的操作更为安全、方便。     

C1侧块C2椎板螺钉固定与C1-2关节螺钉固定的生物力学性能比较

目的 比较1侧块C2椎板螺钉固定与后路C1-2关节螺钉固定的牛物力学性能,为枢椎交叉椎板螺钉的临床应用提供参考依据.方法 收集新鲜成年人尸体颈椎标本(C0-C4)10具,男6具,女4具,平均年龄58岁(50～72岁).分别制备成C1-2完整状态的模型(M0)、C1-2失稳的模型(M1)、C1,侧块螺钉C2交义椎板螺钉固定模型(M2)及后路C1-2关节螺钉固定模型(M3),进行三维生物力学测试,记录各组模型在屈伸、轴向旋转和侧屈的运动范围(ROM)和中性区(NZ).结果 屈伸模式下M0、M1、M2、M3的ROM和NZ分别为:(20.4±9.2)°、(10.4±5.8)°;(46.3±17.2))°、(34.5±14.1)°;(4.1±0.9)°、(1.9±0.8)°;(4.3±1.0)°、(2.1±0.7)°.轴向旋转模式下 M0、M1、M2、M3的ROM和NZ分别为:(65.3±12.9)°、(40.8±11.2)°;(91.7±10.5)°、(72.3±12.6)°;(8.9±2.1)°、(4.7±1.8)°;(8.4±2.5)°、(4.4±2.3)°.侧屈模式F M0、M1、M2、M3的ROM和NZ分别为:(11.5±4.3)°、(7.2±3.2)°;(35.0±12.9)°、(21.9±11.8)°;(2.9±1.1)°、(1.4±0.8)°;(2.5±1.4)°、(1.3±1.0)°.在三维运动模式下M2和M3力学稳定性均明显优于M1和M0,然而M2和M3,的差异无统计学意义(P>0.05).结论 C1侧块C2椎板螺钉固定拥有良好的生物力学稳定性,可作为C1-2关节螺钉固定的良好替代.     

枢椎侧弓螺钉安全钉道的判定与测量

目的:利用Unigraphics(UG)三维重建技术寻找枢椎侧弓螺钉安全钉道的经过,并进行相关参数的测量.方法:对4例干燥和8例新鲜枢椎行CT扫描, UG软件重建虚拟实体,利用3.5 mm虚拟螺钉模拟进钉,寻找安全钉道经过的特征标记点.以此为基础,测定57例干燥枢椎安全钉道的内倾角与上倾角(AutoCAD环境)及进针点距峡部及下关节突外缘的距离(手工测量).结果:模拟发现横断面安全钉道经过前弓中宽后界的内中1/3交界与中宽前界的外中1/3交界,矢状面经过前弓中宽后界中部及前界中宽与上关节突下界交界处.对另57例干燥标本进行测量发现安全钉道的内倾角为左/右＝(10.94±6.53)°/(11.95±2.82)°,上倾角为(13.31±5.44)°/(14.45±3.80)°,在大多数标本椎板后下方有一突起的骨嵴 (左/右＝84.2%/84.98%) ,进针点多位于这一骨嵴线上(左/右＝87.5%/84.9%).进针点距离下关节外侧缘左/右＝(6.71±1.33)mm/(6.28±1.48)mm,距离后弓左/右＝(9.93±1.38)mm/(8.47±1.70)mm.个体间差异较大.结论:侧方椎弓螺钉固定的安全钉道在横断面经过横突孔区域(侧弓前份)中宽后界的内中1/3交界与中宽前界的外中1/3交界,矢状面经过后方中宽中部及前方中宽与关节突下界交界处,不同侧别间及不同个体间有明显差别.     

Saccadic anomalies: vergence induces large departures from ball-and-socket behavior

The configuration of muscular forces, which maintains a given orientation of the eye, varies with vergence state. As a consequence, changes in vergence produce both static and dynamic violations of simple ball-and-socket behavior: during strong convergence, the entire eye is displaced temporally within its orbit at steady state by as much as 200 microns; and the axis of ocular rotation for small horizontal saccades is consistently displaced forward within the globe by an average of about 1 mm. These phenomena occur regardless of whether vergence is maintained by accommodation or by binocular disparity. Hence, systematic errors of as much as a full degree can arise in measurement of vergence movement, unless monitoring methods are used which are insensitive to translational motion. The observed displacement on the axis of rotation for saccades may be involved in subjective shrinkage of visual targets during convergence ("experimental micropsia ").