A clinical morphologic study of the C2 pedicle and isthmus

Purpose

This anatomic, radiographic study investigated locational differences in the C2 pedicle and isthmus [pediculoisthmic component (PIC)] and characterized its narrowest section for clinical application in posterior C2 screw fixation.

Methods

Structures surrounding the transverse foramina of 30 dry C2s and 10 C3s were compared morphologically. Spinal CT scans of 32 Chinese adults were subjected to volume rendering and multiplanar reconstruction to identify the narrowest C2 PIC, and correlative parameters were measured and analyzed.

Results

Inferior C2 and C3 structures were morphologically similar. In superior view, the C2 superior facets lay on the transverse foramen and the upper portion between superior and inferior facets was flat (average mediolateral angle, 11.1° ± 2.4°). In inferior view, the posteroinferomedial portion of the C2 transverse foramen displayed a partially tubular structure (average mediolateral angle of projection, 42.6° ± 4.9°). Average height and width were 11.6 and 6.9 mm. The inner medullary cavity was elliptical and the middle site of endosteal diameter was 3.3 ± 1.9 mm. Medial internal cortical bone was significantly thicker than lateral bone (P < 0.01).

Conclusions

The PIC is located between superior and inferior C2 facets. The superior flat area is the isthmus and the inferomedial area connecting the inferior facet and vertebral body is the pedicle. The pedicle is partially tubular and projects posteromedially to the transverse foramen. The narrowest PIC section is the narrowest point of the C2 pedicle. Considering its thin lateral cortical bone, medial and superior pedicle screw placement and preoperative CT reconstruction are recommended.     

Comparison of revision strategies for failed C2-posterior cervical pedicle screws: a biomechanical study

Study purpose

With increasing usage within challenging biomechanical constructs, failures of C2 posterior cervical pedicle screws (C2-pCPSs) will occur. The purpose of the study was therefore to investigate the biomechanical characteristics of two revision techniques after the failure of C2-pCPSs.

Materials and methods

Twelve human C2 vertebrae were tested in vitro in a biomechanical study to compare two strategies for revision screws after failure of C2-pCPSs. C2 pedicles were instrumented using unicortical 3.5-mm CPS bilaterally (Synapse/Synthes, Switzerland). Insertion accuracy was verified by fluoroscopy. C2 vertebrae were potted and fixed in an electromechanical testing machine with the screw axis coaxial to the pullout direction. Pullout testing was conducted with load and displacement data taken continuously. The peak load to failure was measured in newtons (N) and is reported as the pullout resistance (POR). After pullout, two revision strategies were tested in each vertebra. In Group-1, revision was performed with 4.0-mm C2-pCPSs. In Group-2, revision was performed with C2-pedicle bone-plastic combined with the use of a 4-mm C2-pCPSs. For the statistical analysis, the POR between screws was compared using absolute values (N) and the POR of the revision techniques normalized to that of the primary procedures (%).

Results

The POR of primary 3.5-mm CPSs was 1,140.5 ± 539.6 N for Group-1 and 1,007.7 ± 362.5 N for Group-2; the difference was not significant. In the revision setting, the POR in Group-1 was 705.8 ± 449.1 N, representing a reduction of 38.1 ± 32.9 % compared with that of primary screw fixation. For Group-2, the POR was 875.3 ± 367.9 N, representing a reduction of 13.1 ± 23.4 %. A statistical analysis showed a significantly higher POR for Group-2 compared with Group-1 (p = 0.02). Although the statistics showed a significantly reduced POR for both revision strategies compared with primary fixation (p < 0.001/p = 0.001), the loss of POR (in %) in Group-1 was significantly higher compared with the loss in Group-2 (p = 0.04).

Conclusions

Using a larger-diameter screw combined with the application of a pedicle bone-plastic, the POR can be significantly increased compared with the use of only an increased screw diameter.     

The differential effect of BMI on prosthetic versus autogenous breast reconstruction: A multivariate analysis of 12,986 patients

BackgroundThe comparative safety of breast reconstruction in obese patients remains to be clearly defined. This study utilized multi-institutional data to characterize the effect of body mass index (BMI) on breast reconstruction outcomes.MethodsUtilizing Current Procedural Terminology (CPT) codes, patients undergoing tissue expander, pedicled transverse rectus abdominis myocutaneous (TRAM) flap, latissimus dorsi flap, and free flap breast reconstruction were identified in the National Surgical Quality Improvement Program (NSQIP) database. Patients were stratified as obese (BMI ≥ 30) and non-obese (BMI < 30). Overall postoperative morbidity, flap complications, non-flap complications, and reoperation rates were compared among the groups.ResultsOf 12,986 patients who underwent breast reconstruction, 3636 (28.0%) were obese. Overall morbidity was significantly elevated in obese patients across all forms of reconstruction (p < 0.05). BMI was correlated with increased surgical complications for tissue expander, pedicled TRAM, and free flap reconstructions (OR = 1.09, OR = 1.05, OR = 1.10, respectively; p < 0.05). Medical complications were higher in obese patients undergoing tissue expander and pedicled TRAM reconstructions (p = 0.001 and p < 0.001), but no significant difference was observed in latissimus and free flap reconstruction patients. Compared with obese tissue expander recipients, obese patients reconstructed using autologous tissue had higher rates of reoperations (12.8% versus 9.1%), overall morbidity (18.0% versus 9.5%), surgical (12.7% versus 8.3%), and medical complications (9.0% versus 2.2%).ConclusionsThe NSQIP database allows for evaluation and comparison of reconstructive outcomes in the obese population. Increased BMI was associated with higher morbidity in autologous reconstruction than tissue expander reconstruction. Among autologous procedures, latissimus flaps experienced the lowest captured 30 day morbidity.     

椎弓根螺钉的不同结构特点对螺钉电阻的影响

目的:研究椎弓根螺钉的不同结构特点(实心与空心螺钉、直径)对螺钉电阻的影响,进而探讨其对刺激肌电监测椎弓根螺钉置入准确性的可能影响.方法:选择临床常用的两个厂家(强生和美敦力公司)的12枚椎弓根螺钉,每个厂家各6枚,强生公司实心与空心螺钉的直径均为5.0mm、6.0mm和7.0mm;美敦力公司实心与空心螺钉的直径均为4.5mm、5.5mm和6.5mm.用万用电表测量通过椎弓根螺钉的电流,用电位差计测量螺钉杆上间隔20mm节段的电位差,通过欧姆定律计算椎弓根螺钉的电阻值.结果:美敦力公司的4.5mm实心与空心椎弓根螺钉电阻分别为(0.142±0.003)Ω和(0.398±0.002)Ω,5.5mm实心与空心椎弓根螺钉电阻分别为(0.110±0.007)Ω和(0.347±0.003)Ω,6.5mm实心与空心椎弓根螺钉电阻分别为(0.086±0.002)Ω和(0.290±0.003)Ω.强生公司的5.0mm实心与空心椎弓根螺钉电阻分别为(0.149±0.001)Ω和(0.291±0.001)Ω,6.0mm实心与空心椎弓根螺钉电阻分别为(0.123±0.004)Ω和(0.237±0.001)Ω,7.0mm实心与空心椎弓根螺钉电阻分别为(0.095±0.001)Ω和(0.148±0.001)Ω.相同直径的空心椎弓根螺钉较实心椎弓根螺钉具有较大的电阻,差异有统计学意义(P＜0.05).无论实心椎弓根螺钉或空心椎弓根螺钉,随着直径的增大,椎弓根螺钉的电阻值逐渐减小,差异有统计学意义(P＜0.05).结论:长度与直径相同的空心椎弓根螺钉较实心螺钉具有较大的电阻,长度相同的实心或空心小直径椎弓根螺钉具有较大的电阻,应用刺激肌电监测椎弓根螺钉置入时要注意其带来的影响.     

1～6岁正常小儿胸椎椎弓根形态学研究

【摘要】 目的：测量1～6岁小儿胸椎椎弓根的形态学参数,为小儿胸椎椎弓根螺钉固定提供解剖学依据。方法：收集2009年7月~2010年1月在北京儿童医院行胸部CT检查的1～6岁非脊柱疾患小儿胸椎螺旋CT影像资料。根据年龄将入组儿童分为1～岁组（1组）,2～岁组（2组）,4～6岁组（3组）,每组20例。每例均测量T1～T12左右两侧椎弓根参数共24组数值。将64排螺旋CT平扫胸椎的三维重建数据传至工作站,在多平面重建技术下获得每个椎弓根的矢状面及横断面成像,测量胸椎椎弓根横径（内外径）、纵径（内外径）、骨-螺钉通道长度、椎弓根横断面夹角、椎弓根矢状面夹角,并将上述各参数与年龄进行相关性分析,椎弓根横断面夹角和椎弓根矢状面夹角年龄组间采用多重T检验。结果：（1）椎弓根的横径（内外径）T1～T4逐渐减小,T5～T12逐渐增大;横内径值（除T1、T6、T11、T12外）与年龄无显著相关性（rs：0.011～0.363,除T1、T6、T11、T12外,P>0.05）,其随年龄增长变化不明显;横外径值（除T4外）与年龄均存在显著正相关性（rs：0.151～0.539,除T4外,P<0.05）,其随年龄增长而增长。（2）椎弓根纵径（内外径）T1～T12逐渐增大,除T1外纵径均大于横径;各节段参数与年龄均存在显著正相关性（纵内径rs：0.526～0.786,纵外径rs：0.692～0.864,P<0.05）。（3）骨-螺钉通道长度各年龄组中最短为T1或T2,最长为T9或T10,T1～T9有逐渐增加的趋势,T10～T12有逐渐减小的趋势;各节段参数与年龄均存在显著正相关性（rs：0.299～0.676,P<0.05）。（4）椎弓根横断面夹角最大为T1,T1～T12逐渐减小,部分小儿T11及T12的椎弓根横断面夹角可达0°甚至负角,除T1外,其余各节段参数与年龄均存在显著负相关性（rs：-0.432～-0.107,除T1 P>0.05外,余P<0.05）,1组与2、3组间存在显著性差异（P<0.05）,2组与3组间无显著性差异（P>0.05）。（5）椎弓根矢状面夹角T1~T12呈下降趋势,各节段参数与年龄无显著相关性（rs：-0.125～0.127,P>0.05）,1、2、3三组间无显著性差异（P>0.05）。结论：1～6岁小儿胸椎椎弓根横外径、纵经、骨-螺钉通道长度与年龄的相关性较大,而椎弓根横内径的生长速度较慢,与年龄的相关性较小;横断面及矢状面夹角与年龄的相关性较小,除1~岁年龄组外,其余年龄段的参数值随年龄增长无明显变化。因此行1～6岁小儿胸椎椎弓根螺钉内固定手术时,应根据患儿年龄及术中情况妥善选择螺钉型号及进钉方式,以避免手术风险。     

椎弓根螺钉短节段固定联合椎体成形术治疗单节段胸腰段骨质疏松性椎体爆裂骨折

【摘要】 目的：探讨椎弓根螺钉短节段固定联合椎体成形术治疗单节段胸腰段骨质疏松性椎体爆裂骨折的临床疗效。方法：回顾性分析我院2008年1月～2012年3月收治的86例单节段胸腰段爆裂椎体骨折患者的临床资料,对其中32例合并骨质疏松症的患者进行随访分析。男14例,女18例;年龄56～78岁,平均64.5岁;跌倒伤14例,车祸伤9例,高处坠落伤5例,重物砸伤4例;骨折节段：T11 3例;T12 10例;L1 15例;L2 4例。手术时均在骨折上下椎置入椎弓根螺钉,安装连接棒,通过体位结合撑开实现骨折椎体复位,然后在伤椎注入骨水泥。应用VAS及SF-36量表评估患者疼痛及生活质量改变情况,通过X线片测量计算伤椎椎体前缘高度恢复、受伤节段后凸矫正及丢失情况,随访观察治疗效果。结果：所有患者均顺利完成手术,术中无明显并发症。随访12～36个月,平均16.5个月。术后VAS评分（2.43±1.81分）及末次随访时VAS评分（2.17±1.81分）与术前（7.67±2.25分）比较差异有统计学意义（P<0.05）;末次随访SF-36评分（123.5±22.3分）与术前（95.7±17.5分）比较差异有统计学意义（P<0.05）。术前Cobb角为22.3°±3.6°,术后Cobb角矫正至5.2°±1.2°,末次随访时为6.0°±2.3°,丢失0.8°±1.5°;术前椎体高度（56.4±5.8）%,术后椎体高度恢复至（95.3±2.9）%,末次随访时为（91.4±3.7）%,丢失（4.0±2.5）%。3例出现椎旁静脉骨水泥栓塞,无明显症状,无内固定断裂。结论：后路短节段椎弓根螺钉固定联合椎体成形术能够有效恢复并维持伤椎高度,减少后凸畸形矫正丢失及内固定失败的发生,具有良好的疗效。     

C6、C7椎弓根置钉的应用解剖学研究

目的:通过对C6、C7椎弓根的解剖学测量,设计一种以“峡部”为参考的C6、C7椎弓根置钉的方法.方法:15具经福尔马林浸泡的成人颈椎标本,不分性别、年龄,排除畸形及破坏.取C6、C7共30个椎体.先测量椎弓根宽度(PW)、椎弓根高度(PH).将C6、C7侧块中的一部分定义为“峡部”,即过上关节突下缘最低点、下关节突上缘最高点的水平线与过上关节突内外侧缘的垂线所围成区域.过上关节突内外侧缘之间划两条垂线,将“峡部”分为3等份,中份为“峡部”的后侧面,外份为“峡部”的后外侧面.取过横突根部中点的水平线与过“峡部”中外1/3垂线的交点为螺钉的进钉点.选择3.5mm直径及合适长度的螺钉,直视下沿椎弓根中轴线方向置入,使螺钉中轴线与椎弓根中轴线重合,螺钉前端穿出椎体或上终板.沿椎弓根中轴线的水平面锯开标本,可看到螺钉处在椎弓根中轴线上.螺钉在水平面上与“峡部”的后外侧面形成的角为横向角(E角);螺钉在矢状面上与“峡部”后侧面形成的角为纵向角(F角).测量椎弓根钉道全长(FSC).对数据进行t检验及类聚分析.结果:各指标同一节段左右侧数据比较无统计学差异(P＞0.05),故将同节段左右侧数据合并后进行统计分析.C6的PW为6.12±0.78mm,PH为7.48±0.81mm;C7的PW为6.85±0.73mm,PH为8.03 ±0.38mm;PW与PH均为C6＜C7(P＜0.05),同一节段PW＜PH(P＜0.05).利用聚类分析中的Hierarchical cluster过程对数据进行聚类分析,结果显示E角趋向于两类,即E1和E2.C6的E1角、E2角、F角及FSC与C7比较均无统计学差异(P＞0.05),将同一指标C6与C7数据合并统计结果为FSC 30.83±0.91mm,E1角89.61°±1.24°,E2角59.71°±1.10°,F角75.86°±112°.结论:在C6、C7以过横突根部中点的水平线与过“峡部”中外1/3垂线的交点为螺钉的进钉点,沿椎弓根中轴线方向,在水平面上按照E角、在矢状面上按照F角进钉,行椎弓根置钉具有可行性.     

术中头部体位对强直性脊柱炎胸腰椎后凸畸形患者后路截骨矫形时唤醒试验的影响

【摘要】 目的：探讨术中头部体位对强直性脊柱炎（ankylosing spondylitis,AS）胸腰椎后凸畸形患者经椎弓根椎体截骨（pedicle subtraction osteotomy,PSO）时唤醒时间及苏醒质量的影响。方法：选取2005年5月~2012年11月在我院行PSO的35例AS胸腰椎后凸畸形患者,分为头部抬高体位组（抬高组）和头部未抬高体位组（未抬高组）。两组患者麻醉方式、麻醉诱导用药和维持用药均相同,同时用脑电双频指数（bispectral index,BIS）监测麻醉深度使其保持一致,比较抬高组和未抬高组患者PSO术中唤醒时间及苏醒质量（采用Imani等分级标准分级）。结果：所有患者术中唤醒试验均成功。抬高组患者的术中唤醒时间为24.9±5.13min,未抬高组为39.8±9.41min,两组差异有显著性（P<0.05）。唤醒试验中,抬高组1例、未抬高组5例患者突然睁眼,并伴有四肢不自主活动,苏醒质量为2级,其余29例患者苏醒质量均为1级。抬高组患者术后颜面部及球结膜水肿的外观表现均较未抬高组轻。结论：AS胸腰椎后凸畸形患者PSO术中头部抬高体位可以缩短术中唤醒时间、提高患者的苏醒质量。     

后路椎弓根螺钉系统矫正青少年特发性脊柱侧凸术后主动脉位置变化分析

【摘要】 目的：评价接受后路椎弓根螺钉系统矫正手术的青少年特发性脊柱侧凸患者术前、术后1周和术后2年主动脉相对于脊柱的空间位置变化。方法：研究对象为接受后路椎弓根螺钉系统矫正手术的22例右胸主弯的青少年特发性脊柱侧凸患者。通过三维重建CT测量患者术前、术后1周、术后2年主动脉位置和顶椎旋转畸形情况,测量参数包括主动脉-椎体距离、主动脉-椎体角、主动脉-椎管距离、左侧椎弓根螺钉长度和顶椎旋转角。通过X线片测量胸主弯的Cobb角和胸椎后凸角。结果：术前主胸弯Cobb角为57.5°±9.8°,术后1周矫正至13.6°±6.5°,术后2年时为16.2°±6.8°;主胸弯Cobb角矫正率术后1周时为77.5%,术后2年时为73.3%。术前顶椎轴面旋转角为29.4°±9.3°,术后1周矫正至14.6°±6.9°,术后2年时为17.4°±6.8°;顶椎旋转畸形的矫正率术后1周时为49.5%,术后2年时为39.7%。主动脉-椎体距离在T6～T11节段术前显著大于术后1周（P<0.05）;在T7～T9节段术后2年显著大于术后1周（P<0.05）。主动脉-椎体角在T5～T11节段术前显著大于术后1周（P<0.05）;在T7～T10节段术后2年显著大于术后1周（P<0.05）。主动脉-椎管距离在T7～T11节段术前显著小于术后1周（P<0.05）;在T6～T10节段术后2年显著小于术后1周（P<0.05）。结论：右胸主弯的青少年特发性脊柱侧凸患者中,术后主动脉相对于脊柱的位置较术前向前内侧移位,术后2年较术后向后外侧移位。在使用椎弓根螺钉系统治疗特发性脊柱侧凸的手术中应该避免椎弓根螺钉穿出椎体前皮质或者椎弓根外侧皮质而导致主动脉损伤。     

经皮椎弓根螺钉内固定治疗胸腰椎骨折疗效观察

目的探讨经皮椎弓根螺钉内固定手术治疗胸腰椎骨折的效果。方法将42例胸腰椎骨折患者随机分为开放椎弓根螺钉内固定组(开放组,21例)和经皮椎弓根螺钉内固定组(经皮组,21例)。对术中、术后反映手术创伤的指标进行监测,观察术前、术后1年椎体前缘高度和伤椎Cobb角,并进行比较分析。结果经皮组手术时间、术中出血量、术后引流量、切口长度、住院时间及带支具离床时间均少于开放组(P<0.05),经皮组内固定破坏、腰背部疼痛的程度和发生率均低于开放组(P<0.05);两组术后伤椎椎体前缘高度、Cobb角与术前比较差异均有统计学意义(P<0.05),经皮组伤椎椎体恢复较开放组好。结论微创经皮置入椎弓根钉固定技术治疗胸腰椎骨折并发症少,功能恢复较开放椎弓根螺钉内固定好。