S_1椎体横向骶髂关节螺钉固定钉道的数字化分析与应用

目的探讨经骶髂关节横向S1椎体螺钉固定安全钉道的确定及其在骶骨纵形骨折治疗中的应用。方法对50名健康成年志愿者进行腹部连续螺旋CT扫描、三维表面重建、标准骶骨矢状位多层剖分等,以确定最优钉道。将数字化分析结果应用于2012年8月至2013年8月内蒙古医科大学附属医院收治的18例骶骨纵形骨折患者,术中经骶骨矢状位图像投影确定横向置钉钉道后,采取经骶髂关节横向S1椎体螺钉固定治疗。结果矢状位X线片检查显示S1椎体安全区投影呈卵圆形,投影的长短轴连线交点为S1椎体最优横向钉道,钉道平均长度(135±8)mm,虚拟置入直径7.3 mm的拉力螺钉后骶髂关节螺钉位置及长度满意。术后X线片及CT平扫断层图像显示患者骶髂关节螺钉位置及长度均满意,平均长度(115±4)mm,平均手术时间(30±5)min。术后随访12~24个月,平均随访时间(16±3)个月,未见神经血管损伤、骶髂关节螺钉松动及断裂等并发症。结论通过术中骶骨矢状位图像投影确定横向置钉钉道,可提高经皮横向骶髂关节螺钉固定治疗骶骨纵形骨折的手术安全性,同时简化手术过程。     

经S2椎弓根骶髂关节螺钉固定CT和解剖学研究

目的 :为经S2 椎弓根水平骶髂关节螺钉固定提供解剖学依据。方法 :对 2 2个骨盆标本进行解剖学研究 ,测量经S2 椎弓根骶髂关节螺钉固定的进针点、进针方向、钉道直径、进针点至S2 椎体中心和椎弓根中心距离、S2 椎弓根横断面形状。结果 :螺钉进针点在髂后下棘前方 2 8 7mm (15 0～34 5mm) ,坐骨切迹上方 15 3mm(10 0～ 2 2 0mm) ;进针方向垂直于正中矢状面且与髂骨翼外侧面夹角为 6 2 4°(5 5°～ 72°) ;钉道直径为 11 5mm (8 5～ 14 0mm) ;进针点至S2 椎体中心距离 6 4 7mm(5 5 3～ 77 6mm) ;进针点至S2 椎弓根中心距离为 5 3 1mm(45 3～ 6 4 8mm) ;S2 椎弓根横截面呈三角形。结论 :经S2 椎弓根水平骶髂关节螺钉固定的进针点应位于髂后下棘前方 30mm ,坐骨切迹上方15mm ;进针方向垂直于正中矢状面且与髂骨翼外侧面夹角为 6 0°;S2 椎弓根钉道直径较小 ,经S2 椎弓根水平骶髂关节螺钉固定应选择直径较小的短螺钉。     

骶髂关节经皮拉力螺钉固定钉道参数的解剖学测量

目的 为经S_1椎弓根水平骶髂关节拉力螺钉固定术提供应用解剖学依据.方法 2008年6月至2009年7月收集50个成人骨盆的螺旋CT扫描数据,重建骨盆三维模型,模拟经皮托力螺钉固定.测量S_1椎弓根的宽和高、骶髂关节拉力螺钉的进针点和进针方向、进针点至S_1椎体对侧前皮质和髂后上棘的距离.结果 S_1椎弓根的宽和高分别为(20.43±1.63)mm和(20.26±0.99)mm;2枚螺钉的进针点均在髂前上棘和髂后上棘的连线上方,至髂后上棘的距离分别为(49.87±6.80)mm和(51.11±7.15)mm.螺钉平行进入S_1椎弓根,与髂骨翼后外侧面垂直,与冠状面和欠状面的夹角分别为18.35°±5.20°和77.62°±3.98°.进针点到S1椎体对侧前皮质的距离分别为(76.08±4.32)mm和(77.62±3.98)mm.骶髂关节拉力螺钉的长度、S_1椎弓根的高度和宽度、进针点到髂后上棘的距离、进针点与冠状面的夹角在男女之间差异有统计学意义(P<0.05).结论 正常成人在S_1椎弓根水平均町置入2枚直径为6.5 mm的拉力螺钉,钉道参数的解剖学测量为骶髂关节拉力螺钉固定手术导航模板的设计提供了理论基础.     

骶2椎弓根前外侧置钉法的应用解剖学研究

目的:观察S2椎弓根的解剖特点及与周围血管神经的毗邻关系,探讨以第一骶后孔与骶外侧嵴为解剖标志的S2椎弓根前外侧置钉技术的可行性。方法:取20具成人干燥骶骨标本,其中15具分别从S1-S2和S2-S3椎体融合遗迹(骶横线)处平行骶骨底平面截断骶骨,观察S2椎弓根的形态;在第一骶后孔下缘最低切迹处平行骶骨底平面截断骶骨。在S2椎弓根前部(即盆面),截面与骶前孔外侧缘连线的交点为A点,与耳状面前缘(即骶髂关节处)的交点为B点。在截面上测量骶外侧嵴(X点)与A、B两点连线即XA线、XB线长度及其与正中矢状面夹角α角、β角;在截面上测量骶中间嵴(Y点)与A、B两点连线即YA线、YB线长度及其与正中矢状面夹角γ角、θ角;在5具完整的干燥骶骨标本上于X点向前外侧置入椎弓根螺钉,置钉方法为矢状面平行骶骨底,角度在α角与β角之间,并行CT扫描观察螺钉的位置。在10具经福尔马林浸泡固定的成人尸体标本上观察骶骨前血管神经的毗邻关系,观察骶前孔、骶髂关节与骶前交感干、髂内动静脉的关系。并按照上述测量结果分别在X、Y点向前外侧置入S2椎弓根螺钉,使螺钉穿出骶骨前方,落在骶前孔外侧缘与耳状面前缘之间。观察螺钉的出钉点与骶前血管神经的关系。结果:S2前方有大量的骨质可供螺钉置入。XA为26.0±1.7mm,XB为33.1±1.1mm,α角为22.1°±2.0°,β角为36.0°±3.7°;YA为30.1±0.8mm,YB为35.5±1.0mm,γ角为36.7°±1.5°,θ角43.8°±1.3°。在骶髂关节前方从骶前孔外侧缘开始向外侧依次有髂内静脉、髂内动脉、髂外静脉、髂外动脉。第1骶前孔与第2骶前孔之间的前外侧有S1神经通过。骶前交感干走形在骶前孔内侧缘,出钉点在骶前孔外侧,髂内动静脉后方。结论:S2椎弓根前外侧置钉安全可行,向前外侧固定时螺钉不能突破前方骨皮质,以免伤及骶前血管及神经。以骶外侧嵴与第一骶后孔下缘最低切迹水平面交点(X点)为进钉点,前外侧置钉更适用。     

五种骶骨螺钉内固定的应用解剖研究

目的　评价五种骶骨内固定的安全性。方法　解剖七具尸体 ,以克氏针穿透模拟五种骶骨螺钉法 ,克氏针穿透骶椎前缘。分析骶骨螺钉损伤骶前重要结构的可能性 ,测量骶前安全区范围和螺钉钉道长度。结果　PTSF法螺钉不应穿透L5椎体前缘皮质 ,前外骶翼方向和垂直骶翼方向S1螺钉易损伤髂内动、静脉和腰骶干 ,前内骶岬方向S1螺钉的主要危险是骶正中血管 ,S2 螺钉易损及S1神经前支和交感链。结论　五种骶骨固定法均可损伤骶前重要结构 ,手术时应谨慎操作     

五种骶骨螺钉内固定的应用解剖研究

目的 评价五种骶骨内固定的安全性。方法 解剖七具尸体,以克氏针穿透模拟五种骶骨螺钉法,克氏针穿透骶椎前缘。分析骶骨踝螺钉损伤骶前重要结构的可能性,测量骶前安全区范围和螺钉道长度。结果 PTSF法螺钉不应穿透L5椎体前缘皮质,前外骶翼方向和垂直骶翼方向S1螺钉易损伤髂内动、静脉和腰骶干,前内骶岬方向S1螺钉的主要危险是骶正中血管,S2螺钉易损及S1神经前支和交感链。结论 五种骶骨固定法均可损伤骶前重要结构,手术时应谨慎操作。     

骶骨临床解剖学新进展

骶骨螺钉及骶髂关节螺钉广泛应用于L5S1椎体滑脱、骶髂关节分离和骶骨骨折的治疗.由于骶骨的解剖结构既复杂又特殊,螺钉的置入常难以达到理想的位置,并且螺钉的穿出会导致重要血管神经的损伤,因此掌握骶骨的解剖对于骨科医生至关重要[1～3].本文对近年来骶骨的临床解剖学进展综述如下. 1 骶骨的底 第1骶椎的头侧表面代表了骶骨的底.S1椎体上终板前缘向前凸出,称为岬,是腰骶联合部位前路手术的重要解剖标志.S1椎体后面是三角形的骶管,2个上关节突位于骶管外侧,关节面朝向后内方向,同L5的下关节突相关节.     

天玑骨科手术机器人结合三维成像技术辅助微创治疗骨盆骨折的疗效分析

目的探讨天玑骨科手术机器人结合三维成像技术辅助微创手术治疗骨盆骨折的疗效。方法回顾性分析2019年1月至2021年5月广东省阳江市人民医院创伤骨科收治的40例以S1及S2骶髂关节螺钉固定的骨盆骨折患者资料, 根据治疗方法不同分为两组:机器人组(采用天玑骨科手术机器人辅助经皮置入骶髂关节螺钉固定)20例, 男13例, 女7例;年龄为(38.2±8.8)岁。徒手组(采用普通C型臂X线机透视下徒手置入骶髂关节螺钉固定治疗)20例, 男11例, 女9例;年龄为(37.3±9.2)岁。记录并比较两组患者螺钉置入所用透视时间、导针调整次数、手术时间、术中出血量、术后72 h疼痛视觉模拟评分、术后住院时间、下地活动时间、螺钉置入优良率、并发症发生率、骨折愈合时间、术后6个月Majeed评分、功能评价优良率。结果两组患者术前一般资料比较差异均无统计学意义(P>0.05), 具有可比性。机器人组螺钉置入透视时间[(8.2±2.9)s]、导针调整次数[(0.4±0.2)次]、手术时间[(67.4±5.5)min]、术中出血量[(36.5±8.0)mL]显著少于徒手组[(40.4±4.5)s、(8.6...     

骶髂螺钉固定在骶髂关节脱位中的应用解剖学研究

目的 :为应用骶髂螺钉固定骶髂关节脱位提供形态学依据。方法 :对 3 0具成人干燥骨盆标本 ,模拟骶髂螺钉内固定手术并作CT扫描 ,对进针点与不同解剖结构之间的距离、进针的方向、进针的深度以及S1骶孔上方的骶骨翼的前后径和上下径进行测量。结果 :进针点距臀肌线的距离为 ( 2 0 70± 3 2 7)mm ,距坐骨大切迹的距离为( 3 5 0 0± 1 91)mm ;轴位及冠状位CT测量进针与髂骨外板的交角分别为 ( 90 18± 2 69)°和 ( 90 40± 2 87)° ;进针深度为 ( 67 77± 3 63 )mm ;S1骶孔上方骶骨翼的前后径和上下径分别为 ( 18 2 6± 2 0 6)mm和 ( 18 74± 1 5 1)mm。结论 :临床应用骶髂螺钉固定需选择恰当的进针点和进针方向 ,术中需行骨盆正位、入口位和出口位的透视以确定螺钉植入的准确性     

骶髂关节螺钉固定应用及CT与解剖学研究

目的 :采用CT扫描测量髂骨翼后外侧面至第 1骶椎 (S1)的距离和S1椎弓根宽 ,为临床上经骶髂关节螺钉固定治疗后骨盆环不稳定提供参考。方法 :对 2 2例中国成人的骨盆标本共 4 4侧骶髂关节进行CT和解剖学研究 ,测量S1椎弓根宽 ,髂骨翼后外侧面的进针点至S1椎弓根中心距离 ,进针点至S1椎体对侧前皮质距离 ,并对解剖测量值和CT测量值进行比较。在实验研究的基础上 ,对 11例垂直不稳定后骨盆环骨折进行骶髂螺钉固定。结果 :髂骨翼后外侧面的进针点至椎弓根中心距离解剖和CT测量值分别为 4 9 5± 4 0mm和 4 9 2± 3 9mm ,两者差异无显著性 (P >0 0 5 ) ;进针点至S1椎体对侧前皮质距离解剖和CT测量值分别为 86 9± 4 6mm和 86 4± 4 4mm ,两者差异无显著性 (P >0 0 5 ) ;S1椎弓根宽解剖和CT测量值分别为 2 7 7± 2 0mm和 2 0 7± 2 5mm ,两者差异有显著性 (P <0 0 1)。临床 11例共 13枚骶髂螺钉均准确置入 ,无骨皮质穿破或神经血管损伤等并发症。结论 :术前CT扫描可准确地推算骶髂螺钉长度 ,具有临床实用意义。     

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.     

骶髂关节空心钉内固定导向器的研制及临床应用

目的 自行设计并研制一种骶骼关节空心钉内固定导向器,以期提高S1椎弓根空心钉置入的成功率及置入质量。方法 自行设计并研制的骶髂关节空心钉内固定导向器由带有测量长度的定位器、带有角度刻度表的水平面S1椎弓根空心钉置入角（TSA）、矢状面置入角(SSA)调节器及固定螺丝等组成。2006年6月至2009年10月共收治15例不稳定型骨盆骨折累及骶髂关节者,男6例,女9例;年龄19 ～ 60岁,平均45.6岁。不稳定型骨盆骨折经骶髂关节韧带3例,经骶骨Ⅰ区5例,累及骶骨Ⅱ区5例,累及骶骨Ⅲ区2例。15例患者均采用骶髂关节空心钉内固定导向器引导术中空心钉的操作,共置入18枚空心钉。结果 术后CT及X线片示18枚空心钉置入位置准确,与术前设计相比,具有相同或相近的TSA及SSA。结论 骶骼关节空心钉内固定导向器设计合理,使用方便,能提高S1椎弓根空心钉置入的准确性及置入质量,且可显著减少C型臂X线机的透视次数。     

基于连续骨盆轴向CT扫描的上骶段分型

目的:介绍基于连续骨盆轴向CT扫描的上骶段的分型及其意义.方法:对127例全骨盆2.0 mm层厚轴向扫描图像进行观察,测量S1的平向骶髂螺钉通道,根据平向通道的大小对上骶段进行分型.如平向通道存在且在至少4层扫描图像上其宽度均＞7.3 mm,则将其定义为正常型上骶段;如平向通道存在且在扫描层面上其最大宽度≤7.3 mm,则将其定义为过渡型;如平向通道不存在,即在所有扫描层面上其宽度均≤0 mm,则将其定义为变异型.计算各型的例数、百分比及平向螺钉通道的平均值.结果:正常型58例(45.7％),其平向螺钉通道平均宽度13.9 mm;过渡型42例(33.1％),其平向螺钉通道的平均宽度5.2 mm;变异型27例(21.2％),其平向螺钉通道的平均宽度为0.9 mm.所有病例的上骶段可归属于3型中的1型.结论:正常型上骶段因存在平向安全通道而可置入平向骶髂螺钉,过渡型及变异型上骶段因无平向通道而无法置入平向骶髂螺钉.过渡型较变异型的优势表现在其标准骶骨侧位像上的有限平向通道可以作为进钉点的选择区域.     

S1 pediculoiliac screw fixation in instabilities of the sacroiliac complex: biomechanical study and report of two cases

OBJECTIVE: A new technique for posterior sacroiliac fixation is described and compared with conventional techniques. PATIENTS/MATERIAL AND METHODS: A patient with sacral alar fracture (zone 1) and another one with sacroiliac joint instability due to tuberculous infection underwent fixation using screws placed in the S1 pedicle and the iliac bone. Vertical stability of the new technique also was investigated using polyurethane pelvic bone analogs and compared with anterior double plating (group P) and iliosacral screw fixation (group ISS) techniques. RESULTS: Healing was obtained and reduction was maintained in both patients on the final follow-up examination at 2 years postoperatively. Vertical loading tests revealed that failure loads within the first 10 mm of displacement of the new pediculoiliac screw fixation technique (group PIS) was higher than plating (P = 0.03) and lower than ISS techniques (P = 0.002). Ultimate failure load of the PIS technique was slightly higher than plating (P = 0.277) and lower than ISS techniques (P = 0.003). With the addition of an iliosacral screw to the pediculoiliac screw construction (PIS+ISS), the PIS technique became more stable in early (P = 0.110) and ultimate failure loads (P = 0.003). CONCLUSIONS: Pediculoiliac screw fixation for sacroiliac joint disruptions and zone I sacrum fractures using iliac and S1 pedicle screws is a new and effective alternative for obtaining and maintaining anatomic reduction.     

髂骨钉棒固定治疗单侧不稳定性DenisⅠ、Ⅱ区骶骨骨折

目的探讨后路髂骨钉棒固定治疗单侧不稳定性DenisⅠ、Ⅱ区骶骨骨折的临床疗效。方法回顾性分析2016年3月至2018年10月治疗50例单侧不稳定性DenisⅠ、Ⅱ区骶骨骨折患者资料。根据置钉及固定方式分为髂骨钉棒固定组(简称髂骨钉棒组)和机器人辅助骶髂螺钉置入组(简称骶髂螺钉组),其中髂骨钉棒组20例,男13例,女7例,年龄(41.10±14.07)岁(范围,22~76岁);骶骨骨折Denis分型,Ⅰ型5例,Ⅱ型15例;均合并骨盆前环损伤,骨盆Tile分型,B1型2例,B2型12例,C1型6例;3例合并骶神经损伤,Gibbons分级Ⅱ级。骶髂螺钉组30例,男18例,女12例;年龄(44.70±13.35)岁(范围,16~78岁);骶骨骨折Denis分型,Ⅰ型6例,Ⅱ型24例;均合并骨盆前环损伤,骨盆Tile分型,B1型2例,B2型20例,C1型8例;4例合并骶神经损伤,Gibbons分级,3例Ⅱ级,1例Ⅲ级。两组患者年龄、手术时间、术中出血量、透视次数、Majeed评分比较采用独立样本t检验;骨折复位质量比较采用卡方检验;骶神经损伤恢复Gibbons分级比较采用秩和检验。结果两组患者均获得随访,随访时间22.8个月(范围,12~40个月)。髂骨钉棒组手术时间(41.40±7.30)min;术中出血(105.00±61.94)ml;术中透视(19.10±7.33)次;根据Mears和Velyvis影像学评价标准,9例解剖复位,10例复位满意,1例复位不满意;Majeed评分(84.25±8.29)分;术前3例GibbonsⅡ级骶神经损伤,术后2例恢复为Ⅰ级。骶髂螺钉组手术时间(18.27±5.89)min;术中出血(33.00±17.54)ml;术中透视(14.93±4.49)次;术后15例解剖复位,13例复位满意,2例复位不满意;Majeed评分(86.43±7.43)分;术前3例GibbonsⅡ级骶神经损伤,其中2例术后恢复为Ⅰ级,术前1例Ⅲ级损伤,术后恢复为Ⅱ级。与骶髂螺钉组比较,髂骨钉棒组手术时间长(t=-12.36,P<0.001)、出血量多(t=-6.04,P<0.001)、透视次数多(t=-2.50,P=0.016),以上各指标比较差异均有统计学意义。术后髂骨钉棒组与骶髂螺钉组在骨折复位质量(χ^2=0.23,P=0.89)、Majeed评分(t=0.97,P=0.34)、Gibbons分级(Z=-0.224,P=0.82)比较,差异均无统计学意义。术后髂骨钉棒组1例发生单侧伤口表浅感染,1例诉钉尾部不适;骶髂螺钉组1例发生S1神经损伤。结论对于单侧不稳定性DenisⅠ、Ⅱ区骶骨骨折且不适合使用骶髂螺钉固定者,采用后路髂骨钉棒固定操作简单,术后疗效满意,与使用机器人辅助骶髂螺钉固定相似。     

Anatomical and biomechanical analysis of sacral pedicle and lateral mass

Objective: To study the anatomical and biomechanical features of sacral pedicle and lateral mass so as to provide reference for clinical screw fixation technology of sacral pedicle and lateral mass.Methods: A total of 60 adult patients' spiral CT images of the sacrum and coccyx were selected randomly. The entry points of sacral pedicle and lateral mass screws were determined, and the screw trajectory was measured using the three dimensional reconstruction method. Meanwhile,the gross anatomy was scrutinized in 15 adult cadaver specimens to determine the sacral pedicle and lateral mass screw entry points. The length, width and angle of sacral pedicle and lateral mass screw trajectory were measured. Eight of 15cadaver specimens were selected to test the maximal extraction force of sacral pedicle and lateral mass screws. The clinical data of 15 cases treated by pedicle and lateral mass screw technology were collected and analyzed.Results: The diameter and length of S1-S5 sacral pedicle and lateral mass screw trajectory were regular, with about 20° inclination angle. The S1 pedicle screw entry point was located at the intersection point of the basal lateral part of articular process and median line of transverse process, and no significant difference was found for the maximal extraction force between pedicle and lateral mass screws (P＞0.05). The entry points of S2-S5 pedicle screws were located at the intersection point of the line connecting adjacent posterior sacral foramina and median line of the transverse process.The lateral mass screw entry point of S2-S5 was on the median side of intersection point between median line of the transverse process and lateral sacral crest. The maximal extraction force of pedicle screws was significantly greater than that of lateral mass screws (P＜0.05).Conclusion: Both the sacral pedicle and the lateral mass screw fixation techniques can offer effective fixation and reconstruction for fracture of the sacrum and coccyx,but pedicle screw fixation may be more convenient, safe and reliable than lateral mass screw fixation.     

肠道准备对经皮横向骶髂关节螺钉固定的影响

[目的]探讨肠道准备对经皮横向骶髂螺钉固定的影响。[方法]2015年8月~2018年12月,30例骶骨骨折行经皮横向S1骶髂关节螺钉置入治疗的患者纳入本研究,采用随机数字表法将患者分为两组,每组15例,准备组患者术前接受肠道准备,无准备组患者术前未接受肠道准备。比较两组手术时间、术中透视次数和曝光时间,以及影像测量的置钉偏差。[结果]准备组的手术时间显著短于无准备组,差异有统计学意义[(32.31±4.92)min vs(40.54±5.83)min,P<0.05)];准备组的术中X线暴露时间显著短于无准备组,差异有统计学意义[(62.59±5.79)s vs(83.19±6.41)s,P<0.05];准备组的术中透视次数显著少于无准备组,差异有统计学意义[(3.71±0.58)次vs(5.21±1.11)次,P<0.05]。术后CT三维重建测量螺钉与术前测量偏移方面,准备组的水平偏移小于无准备组,但差异无统计学意义[(5.53±2.21)°vs(5.63±1.97)°,P>0.05];准备组矢状位偏移小于无准备组,但差异无统计学意义[(4.32±2.08)°vs(4.52±1.91)°,P>0.05]。术后随访6~12个月,所有患者均未发生骶髂关节螺钉松动及断裂等并发症。[结论]肠道准备虽不能提高置钉准确率,但能够缩短手术时间和术中X线暴露时间。     

Trans-iliosacral plating for vertically unstable fractures of sacral spine associated with spinopelvic dissociation: A cadaveric study

Background:

The treatment algorithm for sacral fracture associated with vertical shear pelvic fracture has not emerged. Our aim was to study a new approach of fixation for comminuted and vertically unstable fracture pattern with spinopelvic dissociation to overcome inconsistent outcome and avoid complications associated with fixations. We propose fixation with well-contoured thick reconstruction plate spreading across sacrum from one iliac bone to another with fixation points in iliac wing, sacral ala and sacral pedicle on either side. Present biomechanical study tests the four fixation pattern to compare their stiffness to vertical compressive forces.

Materials and Methods:

Dissection was performed on human cadavers through posterior midline paraspinal approach elevating erector spinae from insertion with two flaps. Feasibility of surgical exposure and placement of contoured plate for fixation was evaluated. Ten age and sex matched computed tomography scans of pelvis with both hips were obtained. Reconstructions were performed with advantage windows 4.2 (GE Light Speed QX/I, General Electric, Milwaukee, WI, USA). Using the annotation tools, direct digital CT measurement (0.6 mm increments) of three linear parameters was carried out. Readings were recorded at S2 sacral level. Pelvic CT scans were extensively studied for entry point, trajectory and estimated length for screw placement in S2 pedicle, sacral ala and iliac wing. Readings were recorded for desired angulation of screw in iliac wing ala of sacrum and sacral pedicle with respect to midline. The readings were analyzed by the values of mean and standard deviation. Biomechanical efficacy of fixation methods was studied separately on synthetic bone. Four fixation patterns given below were tested to compare their stiffness to vertical compressive forces: 1) Single S1 iliosacral screw (7.5 mm cancellous screw), 2) Two S1 and S2 iliosacral screws, 3) Isolated trans-iliosacral plate, 4) Trans-iliosacral plate + single S1 iliosacral screw.

Statistical Analysis:

Mean of desired angulation for inserting screws and percentage of displacement on biomechanical testing was evaluated.

Results:

Mean angulations for inserting sacral pedicel were 12.3° (SD 2.7°) convergent to midline and divergent of 14° (SD 2.3°) for sacral ala screw and 23° (SD 4.9°) for iliac wing screw. All screws needed to be inserted at an angle of 90° to sacral dorsum to avoid violation of root canals. Cross headed displacement across fracture site was measured and plotted against the applied vertical shear load of 300 N in five cycles each for all the four configurations. Also, the force required for cross headed displacement of 2.5 mm and 5 mm was recorded for all configurations. Transmitted load across both ischial tuberosities was measured to resolve unequal distribution of forces. Taking one screw construct (configuration 1) as standard base reference, trans-iliosacral plate construct (configuration 3) showed equal rigidity to standard reference. Two screw construct (configuration 2) was 12% stronger and trans-iliosacral plate (configuration 4) with screw was 9% stronger at 2.5 mm displacing on 300 N force, while it showed 30% and 6%, respectively, at 5 mm cross-headed displacement.

Conclusions:

Trans-iliosacral plating is feasible anatomically, biomechanically and radiologically for sacral fractures associated with vertical shear pelvic fractures. Low profile of plate reduces the risk of hardware prominence and decreases the need for implant removal. Also, the fixation pattern of plate allows to spare mobile lumbosacral junction which is an important segment for spinal mobility. Biomechanical studies revealed that rigidity offered by plate for cross headed displacement across fracture site is equal to sacroiliac screws and further rigidity of construct can be increased with addition of one more screw. There is need for precountered thicker plate in future.     

Supplemental S1 fixation for type C pelvic ring injuries: biomechanical study of a long iliosacral versus a transsacral screw

Background

A single iliosacral screw placed into the S1 vertebral body has been shown to be clinically unreliable for certain type C pelvic ring injuries. Insertion of a second supplemental iliosacral screw into the S1 or S2 vertebral body has been widely used. However, clinical fixation failures have been reported using this technique, and a supplemental long iliosacral or transsacral screw has been used. The purpose of this study was to compare the biomechanical effect of a supplemental S1 long iliosacral screw versus a transsacral screw in an unstable type C vertically oriented sacral fracture model.

Materials and methods

A type C pelvic ring injury was created in ten osteopenic/osteoporotic cadaver pelves by performing vertical osteotomies through zone 2 of the sacrum and the ipsilateral pubic rami. The sacrum was reduced maintaining a 2-mm fracture gap to simulate a closed-reduction model. All specimens were fixed using one 7.0-mm iliosacral screw into the S1 body. A supplemental long iliosacral screw was placed into the S1 body in five specimens. A supplemental transsacral S1 screw was placed in the other five. Each pelvis underwent 100,000 cycles at 250 N, followed by loading to failure. Vertical displacements at 25,000, 50,000, 75,000, and 100,000 cycles and failure force were recorded.

Results

Vertical displacement increased significantly (p < 0.05) within each group with each increase in the number of cycles. However, there was no statistically significant difference between groups in displacement or load to failure.

Conclusions

Although intuitively a transsacral screw may seem to be better than a long iliosacral screw in conveying additional stability to an unstable sacral fracture fixation construct, we were not able to identify any biomechanical advantage of one method over the other.

Level of evidence

Does not apply—biomechanical study.