CT测量在经口咽前路寰枢椎复位钢板内固定手术的作用

目的探讨术前CT测量在经口咽入路改良Ⅱ代解剖型寰枢椎复位钢板(TARP)内固定手术中的作用.方法15例难复性寰枢椎脱位患者均采用Ⅱ代解剖型TARP内固定手术,术前行寰枢椎薄层CT扫描及三维重建,测量与TARP内固定的相关指标,并应用测量数据指导手术实施.结果术前CT测量寰椎钉道长度为18.7±1.3(16.2～21.1)mm,枢椎钉道长度为14.7±0.9(12.8～15.6)mm,寰椎进钉外偏角为12.2°±0.4°(10.2°～14.6°),枢椎进钉内偏角为7.3°±0.3°(5.1°～9.4°),寰椎向外侧显露不能超过寰椎侧块外缘至前结节的距离为22.4±2.1(18.6～25.6)mm,根据寰椎进钉点间距和寰枢进钉点的垂直间距确定钢板型号,所有钢板成功安置,术后影像学检查均证实术前测量基本准确.结论术前薄层CT扫描及三维重建测量对Ⅱ代解剖型TARP手术复位固定有很强的指导作用.     

经口咽寰枢椎侧块关节复位块状骨支撑植骨治疗颅底凹陷症并寰枢椎脱位

目的:探讨经口咽寰枢椎侧块关节牵开复位、三面皮质块状骨支撑植骨、内固定治疗颅底凹陷症合并寰枢椎脱位的价值.方法:2009年12月～2011年12月我院收治33例合并寰枢椎脱位的颅底凹陷症患者,均有脊髓压迫症状.术前寰齿间隙(ADI)3.8～12.1mm (7.9±3.9mm),齿状突顶部与Chamberlain线的垂直距离(DCL) 3.0～15.6mm (9.3±6.2mm),寰枢椎垂直脱位指数(VAAI)0.35～0.51 (0.46±0.07),颈髓延髓角(CMA)112°～145°(127°±13°),JOA评分7～10分.均采用经口咽寰枢椎侧块关节牵开复位、三面皮质块状髂骨支撑植骨、TARP内固定术治疗.记录手术时间、手术出血量等,观察并发症发生情况.术后随访8～23个月,平均11.5个月,复查影像学评价寰枢椎脱位复位和脊髓压迫改善情况,采用JOA评分改善率对脊髓功能改善情况进行评价,在CT扫描图像上观察螺钉位置及植骨融合情况.结果:手术时间110～185min (145±35min),出血量35～85ml(58±18ml).共置入寰椎侧块螺钉66枚,枢椎逆向椎弓根螺钉41枚,枢椎椎体螺钉25枚.术后钉道扫描显示,寰椎螺钉均位于侧块内,2枚逆向枢椎椎弓根螺钉偏外进入椎动脉孔,导致椎动脉孔闭塞,小脑缺血梗死,其余枢椎螺钉均无偏差.术后发生咽后壁感染1例,将钢板取出后改行后路手术获得愈合.术后CT重建图像显示陷入枕骨大孔的齿状突获得较理想复位,脊髓受压解除,ADI改善为0.2～4.5mm( 2.3±2.1 mm),VAAI改善为0.6～0.84(0.74±0.08),CMA改善为140°～178°(157°±15°),与术前比较均有显著性差异(P＜0.01).植骨块镶嵌在寰枢侧块关节间隙,术后6～11个月均获骨性愈合.术后患者肢体麻木、肌肉无力等症状均较术前有明显改善,术后3个月复查JOA评分恢复至13～16分(15.2±0.9分),末次随访时为13～17分(15.3±0.8分),与术前比较均有显著性差异(P＜0.01).结论:经口咽寰枢椎侧块关节牵开复位三面皮质块状髂骨支撑植骨内固定术是治疗颅颈交界区病变的有效方法,但有一定风险和难度,应在严格掌握手术适应证和严格围手术期处理的条件下合理应用.     

单纯后路松解寰枢椎弓根钉棒复位固定治疗难复性寰枢椎脱位

目的采用单纯后路松解寰枢椎弓根钉棒复位固定技术治疗难复性寰枢椎脱位,评价其可行性及疗效。方法回顾性分析2011年3月至2015年12月我科收治的28例难复性寰枢椎脱位患者的临床资料。所有患者均采用后路松解寰枢椎弓根螺钉复位固定,后于寰枢椎板间植骨融合。随访颈椎X线、CT、MRI观察复位及脊髓减压情况,测量寰枢椎管最小矢状径及CMA改善状况,观察植骨愈合情况及JOA评分。结果手术时间平均(145±37)min(115~210 min);手术平均失血量(205±65)ml(140~290 ml)。术中无脊髓、神经根及椎动脉损伤发生,所有患者寰枢椎弓根螺钉成功置入,23位患者(82%)寰枢关节完全复位,所有患者脊髓减压满意。术后随访平均25.6(12~36)个月。术后6个月所有患者植骨融合良好,随访期间未发生内固定松动断裂及脱位复发。在末次随访,JOA评分由术前平均8.6±2.2改善到14.8±1.8(P<0.0005),平均改善率为73.8%;寰枢椎管最小矢状径由术前平均(9.3±4.2)mm改善到(18.6±3.2)mm(P<0.0005)。CMA由术前平均115.2°±12.5°改善到153.6°±9.3°(P<0.05)。结论采用单纯后路松解寰枢椎弓根螺钉复位固定技术可有效治疗难复性寰枢椎脱位,临床效果满意。     

基于椎动脉变异判别的Ⅲ代TARP钢板治疗寰枢椎脱位的个性化置钉

目的:探讨应用基于椎动脉变异判别的Ⅲ代TARP钢板治疗寰枢椎脱位的个性化置钉策略.方法:选择2010年6月～2011年12月实施手术治疗的22例寰枢椎脱位患者,年龄22～58岁,平均41岁.男9例,女13例. 其中外伤性寰枢椎脱位6例,游离齿状突合并的寰枢椎脱位9例,合并颅底凹陷症的寰枢椎脱位7例.均实施经口咽入路松解、复位、内固定手术术前对患者的寰枢椎实施层厚1 mm的薄层CT扫描判定枢椎椎动脉孔类型(Ⅰ型,松散低拐;Ⅱ型,紧密高拐;Ⅲ型,紧密低拐;Ⅳ型,松散高拐),并行CT血管造影,判断优势椎动脉及其他血管变异情况.寰椎采用前路侧块螺钉,枢椎根据以下原则选择置钉方式:①优势椎动脉侧采用枢椎椎体螺钉技术,非优势侧采用逆向椎弓根螺钉技术;②Ⅱ型枢椎椎动脉孔采用枢椎椎体螺钉技术,其他型采用逆向椎弓根螺钉技术.测量术前、术后寰齿间隙(ADI)及垂直寰枢椎指数(CMA)判断寰枢椎复位情况,测量脑干脊髓角评价脊髓压迫改善情况.采用JOA评分判断患者脊髓功能改善情况.结果:手术均顺利完成,共置入枢椎逆向椎弓根螺钉28枚,枢椎椎体螺钉16枚.平均手术时间139±35min,平均出血量49±16ml.术后复查CT显示,28枚逆向枢椎椎弓根螺钉中有1枚外倾角偏大,部分进入椎动脉孔,但无临床症状;16枚枢椎椎体钉均位于椎体内.置钉总优良率97.7％术后CT测量提示,ADI由术前7.9±4.4mm改善为2.1±1.7mm,CMA由术前129°±13°改善为158°±15°(P＜0.05).术后患者肢体麻木,肌肉无力等症状均较术前有明显改善.术前JOA评分9.1±1.6分,术后3个月复查恢复至15.8±0.9分(P＜0.05),末次随访时为15.9±0.7分.结论:在实施TARPⅢ手术,术前采用寰枢椎薄层CT扫描结合椎动脉CT造影的方法进行评估有助于精确判断椎动脉变异的类型,根据变异类型选择个性化的置钉方法有助于降低手术风险.     

前路经寰枢关节螺钉内固定术的解剖学测量及其临床意义

[目的] 为国人前路经寰枢关节螺钉内固定术提供解剖学依据.[方法] 在50套中国成人配套干燥寰枢椎标本上,对前路经寰枢关节螺钉内固定术的相关解剖学数据进行测量.[结果]前路经寰枢关节螺钉内固定术以枢椎前弓下缘与枢椎椎体侧缘交界点上方4mm处为进钉点,在矢状面上螺钉植入的最小外偏角为(10.80±2.10)°,最大外偏角为(25.13 ±3.12)°,冠状面上最小后偏角为(8.85±2.12)°,最大后偏角为(26.96 3.09)°,枢椎正中至枢椎横突孔内侧缘距离为(14.12±1.28)mm,内、外侧钉道长度分别为(17.48±2.10)mm和(25.41±2.59)mm.[结论] 前路经寰枢关节螺钉内固定术中,两侧置入螺钉的理想的钉道角度为外偏10°-25°,后倾9°-27°、理想的螺钉长度为17～25 mm,由枢椎前缘正中向外分离显露不宜超过14 mm.     

人工寰齿关节寰枢椎部件固定钉道的安全因素分析

目的探讨人工寰齿关节寰枢椎部件固定螺钉通道的安全性和可行性,为经口咽入路置换人工寰齿关节提供理论上的依据。方法在10具正常成年人尸体寰枢关节湿性标本上行人工寰齿关节置换术,测量寰椎部件上下位固定螺钉的长度和外倾角,测量枢椎部件固定螺钉的长度,测量枢椎部件固定螺钉的外倾角和下倾角等。结果寰椎部件上下位固定螺钉的长度（Ls、Li）分别为19.3mm±2.2mm和20.4mm±3.5mm;寰椎部件上下位螺钉外倾角（α,β）分别为5.2°±2.5°和14.4°±4.2°;枢椎部件固定螺钉的长度（S）是24.2mm±4.9mm;枢椎部件固定螺钉的外倾角度（θ）是24.8°±4.3°,枢椎部件固定螺钉的下倾角度（δ）是19.2°±4.5°。结论固定人工寰齿关节寰枢椎部件的螺钉通道不仅具有可行性,而且可以避开横突孔、椎动脉沟及椎管等重要解剖结构。     

骨桥切断凹侧松解半椎体切除治疗儿童轻中度混合型先天性脊柱侧后凸

目的:探讨骨桥切断、凹侧松解、半椎体切除治疗儿童轻中度混合型先天性脊柱侧后凸的效果。方法:2001年1月~2013年1月对32例椎体分节障碍混合椎体形成障碍的先天性脊柱侧后凸患儿行后路半椎体切除的同时,行凹侧骨桥切断、松解,利用椎弓根钉棒系统矫形。其中男10例,女22例;年龄4~12岁(7.8±4.2岁)。侧凸Cobb角58.3°±12.5°(35°~78°),后凸Cobb角47.6°±15.6°(13°~55°),躯干偏移18.2±5.5mm(11~32mm)。畸形位于T7~L3,顶椎位于胸段11例、胸腰段13例、腰段8例。合并脊髓纵裂3例,神经根囊肿1例,脊髓拴系综合征1例。结果:手术时间230±125min(160~270min),术中出血量590±113ml(310~850ml)。术中2例置钉过程中出现椎弓根骨折,调整固定节段后完成矫形。术后1例出现单侧下肢麻木无力,予甲强龙及脱水剂治疗1周后症状缓解;2例出现脑脊液漏。术后脊柱侧凸Cobb角13.8°±7.1°(5°~28°),矫正率(76.3±9.5)%;脊柱后凸15.1°±3.9°(0~20°),矫正率(68.3±11.2)%;躯干偏移距离3.1±2.3mm(0~11.6mm)。随访18.4±12.6个月(12~60个月),末次随访时侧凸矫正率丢失(3.9±1.6)%,后凸矫正率丢失(2.3±0.9)%,无内固定松动及断裂发生。结论:对儿童轻中度混合型先天性脊柱侧后凸畸形,行后路一期半椎体切除的同时,将凹侧分节障碍的骨桥予以切断、松解,再通过椎弓根钉棒系统矫形,可获得满意的矫形效果。     

基于CT三维重建的上颈椎三维活动度在体测量研究

目的:采用CT三维重建的方法测量健康成年人上颈椎寰枕关节、寰枢关节的各个方向上的活动度及其耦合运动,以及颈椎病患者上颈椎最大旋转位的三维活动度,并作对比分析,同时验证所使用的测量方法的可靠性。方法:2014年1月至2015年6月,选取20个健康成年受试者(健康成年组),其中男11例,女9例,年龄22～26(24.0±1.2)岁;26个颈椎病患者(颈椎病组),其中男24例,女2例,年龄36～72(52.8±8.6)岁。采集健康成年人中立位、最大右侧旋转位、最大右侧侧屈位及最大屈曲位、最大背伸位5个位置的及颈椎病患者中立位、最大右侧旋转位上颈椎(含枕骨大孔)的CT图像。利用软件Mimics将所得CT重建为三维图像。在各个椎体(或枕骨)上选取明显的解剖标志点进行标注,根据所标注的解剖标志点建立局部坐标系,局部坐标系即代表了所在椎体的位置及方向。利用Pro/Engineer及MATLAB软件运算出上位椎体(或枕骨)相对下位椎体的活动度及颈部整体三维活动度,并比较颈椎病组和健康成年组差异。因解剖标志点识别有人为差异,选取两名实验员进行3次测量,用组内相关系数(组内ICC)和组间相关系数(组间ICC)验证实验方法的可靠性。结果:可靠性验证结果:组内ICC、组间ICC结果均在0.90以上,测量方法有很高的可靠性;健康成年组上颈椎三维活动度:最大右侧旋转位时,寰枕关节有(-6.8±1.5)°的耦合左侧屈和(8.9±2.0)°的耦合背伸活动,其余3个位置寰枕关节各方向活动度均很小,最大为(5.3±2.6)°;最大右侧旋转位时寰枢关节右旋(37.9±5.1)°,占整个颈椎活动度[(72.4±5.0)°]的52.34%,其余3个位置寰枢关节仍以旋转活动最为突出;上位椎体(或枕骨)相对下位椎体的平移距离均很小。颈椎病患者颈椎整体平均轴向旋转角度[(62.0±3.4)°]较健康成年组明显下降,但寰枕关节、寰枢关节的平均轴向旋转角度比较健康成年组没有明显差异(P0.05)。结论:(1)基于CT三维重建的方法能够很好的描述颈椎的这种复杂的三维运动,并且有很高的可靠性。(2)上颈椎运动是一个复杂的三维运动过程,各个方向活动时均附带有其他方向上的耦合运动。(3)颈椎病患者最大旋转位上颈椎旋转方向的活动度较健康成年人没有明显变化。     

双侧经寰枢关节螺钉寰椎椎板钩固定植骨融合治疗可复性寰枢椎脱位的中长期随访报告

目的:评估双侧经寰枢关节螺钉寰椎椎板钩固定植骨融合治疗可复性寰枢椎脱位的中长期疗效。方法:回顾性分析85例在我院接受双侧经寰枢关节螺钉寰椎椎板钩固定植骨融合术的可复性寰枢椎脱位患者的临床资料,其中男21例,女64例;年龄25~65岁(44±9.4岁)。寰椎爆裂性骨折19例,C1、2旋转脱位畸形16例,齿状突骨折26例,齿状突游离15例,寰椎类风湿性关节炎致寰枢椎脱位9例。通过Ranawat分级、颈椎功能障碍指数(NDI)以及颈部/枕骨下疼痛视觉模拟量表(visual analogue scale,VAS)评分评估患者的临床疗效;在术前和末次随访时的颈椎正侧位X线片、MRI、CT三维重建等资料中,提取以下影像学数据:寰齿前间距(atlanto-dental interval,ADI)、有效椎管容积(space available for cord,SAC)、C1-2角、C2-7角,并观察植骨融合情况及颈椎稳定性。结果:所有患者均完成5年以上的随访。末次随访时24例术前存在脊髓压迫症状患者的Ranawat分级有所改善;95%的患者颈部疼痛得到缓解,VAS评分由术前7.56±1.03分下降至2.53±0.53分(P0.05);NDI由术前34.76±5.45分降至13.13±1.21分(P0.05)。ADI由术前6.5±1.0mm降至2.4±0.9mm(P0.05);SAC由术前13.37±2.11mm增大至19.93±2.20mm(P0.05)。手术前C1-2角为21.9°±1.2°,末次随访时为26.6°±6.9°;手术前C2-7角为19.8°±9.2°,末次随访时为15.5°±5.9°。术后6个月,81例(95.3%)患者获得良好的植骨融合,4例患者出现植骨延迟愈合。结论:双侧经寰枢关节螺钉寰椎椎板钩固定植骨融合治疗可复性寰枢椎脱位的长期疗效优良,是一种安全、可靠的后路寰枢椎固定融合技术。     

人工寰齿关节置换后寰枢关节三维稳定性的有限元分析

目的 通过有限元分析的方法评估人工寰齿关节置换对寰枢关节三维活动度的影响.方法 将CT扫描数据导入Mimics软件重建寰枢椎体及人工寰齿关节三维模型,去除模型中寰椎前弓、齿状突和枢椎部分椎体,模拟前路减压术,将人工寰齿关节模型装配于处理过的寰枢椎模型上.导入Ansys软件分析计算模型的三维活动度.结果 人工寰齿关节在前屈、后伸、右侧弯、右旋转状态下的位移分别为1.109、3.310、0.528、9.678 mm,活动度分别为1.6°、5.1°、4.6°和22.0°.结论 改良人工寰齿关节置换既可稳定寰枢关节又可保留寰枢关节运动.     

Investigation of coupled bending of the lumbar spine during dynamic axial rotation of the body

Purpose

Little is known about the coupled motions of the spine during functional dynamic motion of the body. This study investigated the in vivo characteristic motion patterns of the human lumbar spine during a dynamic axial rotation of the body. Specifically, the contribution of each motion segment to the lumbar axial rotation and the coupled bending of the vertebrae during the dynamic axial rotation of the body were analyzed.

Methods

Eight asymptomatic subjects (M/F, 7/1; age, 40–60 years) were recruited. The lumbar segment of each subject was MRI scanned for construction of 3D models of the vertebrae from L2 to S1. The lumbar spine was then imaged using a dual fluoroscopic system while the subject performed a dynamic axial rotation from maximal left to maximal right in a standing position. The 3D vertebral models and the fluoroscopic images were used to reproduce the in vivo vertebral motion. In this study, we analyzed the primary left–right axial rotation, the coupled left–right bending of each vertebral segment from L2 to S1 levels.

Results

The primary axial rotations of all segments (L2–S1) followed the direction of the body axial rotation. Contributions of each to the overall segment axial rotation were 6.7° ± 3.0° (27.9 %) for the L2–L3, 4.4° ± 1.2° (18.5 %) for the L3–L4, 6.4° ± 2.2° (26.7 %) for the L4–L5, and 6.4° ± 2.6° (27.0 %) for the L5–S1 vertebral motion segments. The upper segments of L2–L3 and L3–L4 demonstrated a coupled contralateral bending towards the opposite direction of the axial rotation, while the lower segments of L4–L5 and L5–S1 demonstrated a coupled ipsilateral bending motion towards the same direction of the axial rotation. Strong correlation between the primary axial rotation and the coupled bending was found at each vertebral level. We did not observe patterns of coupled flexion/extension rotation with the primary axial rotation.

Conclusions

This study demonstrated that a dynamic lumbar axial rotation coupling with lateral bendings is segment–dependent and can create a coordinated dynamic coupling to maintain the global dynamic balance of the body. The results could improve our understanding of the normal physiologic lumbar axial rotation and to establish guidelines for diagnosing pathological lumbar motion.     

固定平台后稳定型假体全膝关节置换术后的运动学研究

 目的 探讨固定平台后稳定型假体全膝关节置换(total knee arthroplasty,TKA)术后膝关节在负重屈膝下蹲时的运动学特征。方法 选取10名健康志愿者和10例固定平台后稳定型假体TKA术后患者。制作骨骼及膝关节假体三维模型,在持续X线透视下完成负重下蹲动作,膝关节屈曲度每增加15°截取一幅图像。通过荧光透视分析技术完成三维模型与二维图像的匹配,再现股骨与胫骨在屈膝过程中的空间位置,通过连续的图像分析比较正常与固定平台后稳定型假体TKA术后膝关节在负重下蹲时股骨内、外髁前后移动及胫骨内外旋转幅度。结果 负重下蹲时,正常膝关节平均屈曲136°,股骨内、外髁分别后移(7.3±1.2) mm和(19.3±3.1) mm,胫骨平均内旋23.8°±3.4°;TKA术后膝关节平均屈曲125°,股骨内、外髁分别后移(1.4±1.6) mm和(6.4±1.7) mm,胫骨平均内旋8.5°±3.4°。结论 固定平台后稳定型假体TKA术后膝关节运动与正常膝关节相似,均表现出股骨内、外髁后移及胫骨内旋运动,但幅度小于正常膝关节,且在屈膝过程中存在股骨矛盾性前移及胫骨外旋现象。     

In Vivo Knee Kinematics for a Cruciate Sacrificing Total Knee Arthroplasty Having Both a Symmetrical Femoral and Tibial Component

BackgroundEarly total knee arthroplasty (TKA) designs were symmetrical, but lead to complications due to over-constraint leading to loosening and poor flexion. Next-generation TKAs have been designed to include asymmetry, pertaining to the trochlear groove, femoral condylar shapes, and/or the tibial component. More recently, an advanced posterior cruciate sacrificing (PCS) TKA was designed to include both a symmetrical femoral component with a patented V-shaped trochlear groove and a symmetrical tibial component with an ultracongruent insert, in an attempt to reduce inventory costs. Because previous PCS TKA designs produced variable results, the objective of this study is to determine and evaluate the in vivo kinematics for subjects implanted with this symmetrical TKA.MethodsTwenty-one subjects, implanted with symmetrical PCS fixed-bearing TKA, were asked to perform a weight-bearing deep knee bend (DKB) while under fluoroscopic surveillance. A 3-dimensional to 2-dimensional registration technique was used to determine each subject’s anteroposterior translation of lateral and medial femoral condyles as well as tibiofemoral axial rotation and their weight-bearing knee flexion.ResultsDuring the DKB, the average active maximum weight-bearing flexion was 111.7° ± 13.3°. On average, from full extension to maximum knee flexion, subjects experienced −2.5 ± 2.0 mm of posterior femoral rollback of the lateral condyle and 2.5 ± 2.2 mm of medial condyle motion in the anterior direction. This medial condyle motion was consistent for the majority of the subjects, with the lateral condyle exhibiting rollback from 0° to 60° of flexion and then experienced an average anterior motion of 0.3 mm from 60° to 90° of knee flexion. On average, the subjects in this study experienced 6.6°± 3.3° of axial rotation, with most of the rotation occurring in early flexion, averaging 4.9°.ConclusionAlthough subjects in this study were implanted with a symmetrical PCS TKA, they did experience femoral rollback of the lateral condyle and a normal-like pattern of axial rotation, although less in magnitude than the normal knee. The normal axial rotation pattern occurred because the lateral condyle rolled in the posterior direction, while the medial condyle moved in the anterior direction. Interestingly, the magnitude of posterior femoral rollback and axial rotation for subjects in this study was similar in magnitude reported in previous studies pertaining to asymmetrical TKA designs. It is proposed that more patients be analyzed having this TKA implanted by other surgeons.     

Biomechanical investigation of a novel integrated device for intra-articular stabilization of the C1-C2 (atlantoaxial) joint

Background contextThe anatomy of the atlantoaxial joint makes stabilization at this level challenging. Current techniques that use transarticular screw fixation (Magerl) or segmental screw fixation (Harms) give dramatically improved stability but risk damage to the vertebral artery. A novel integrated device was designed and developed to obtain intra-articular stabilization via primary interference fixation within the C1–C2 lateral mass articulation.PurposeTo assess the atlantoaxial stability achieved with a novel integrated device when compared with the intact, destabilized, and stabilized state using the Harms technique.Study designA biomechanical study of implants in human cadaveric cervical spines.MethodsSix human cadaveric specimens were used. Biomechanical testing was performed with moment control in flexion-extension, lateral bending, and axial rotation. Range of motion (ROM) was measured in the intact state, after both destabilization by creation of a Type II odontoid peg fracture and sequential stabilization using the integrated device and the Harms technique.ResultsMean flexion-extension ROM of the intact specimens at C1–C2 was 14.1°±2.9°. Destabilization increased the ROM to 31.6°±4.6°. Instrumentation with the Harms technique reduced flexion-extension motion to 4.0°±1.4° (p<.01). The integrated device reduced flexion-extension motion to 3.6°±1.8° (p<.01). In lateral bending, the respective mean angular motions were 1.8°±1.1°, 14.1°±5.8°, 1.4°±0.7°, and 0.4°±0.3° for the intact destabilized Harms technique and integrated device. For axial rotation, the respective mean values were 67.3°±13.8°, 74.2°±16.1°, 1.4°±0.7° and 0.9°±0.7°. Both the Harms technique and integrated device significantly reduced motion compared with the destabilized spine in flexion-extension, lateral bending, and axial rotation (p<.05). Direct comparison of the Harms technique and the integrated device revealed no significant difference (p>.10).ConclusionsThe integrated device resulted in interference fixation at the C1–C2 lateral mass joints with comparable stability to the Harms technique. Perceived advantages with the integrated device include avoidance of fixation below the C2 lateral mass where the vertebral artery is susceptible to injury, and access to the C1 screw entry point through the blade of the integrated device avoiding extended dissection superior to the C2 nerve root and its surrounding venous plexus.     

In vivo kinematics of a low contact stress rotating platform total knee arthroplasty system under weight bearing and non-weight bearing condition

Background

The patterns and magnitudes of axial femorotibial rotation are variable due to the prosthesis design, ligamentous balancing, and surgical procedures. We aimed to investigate the effects of the weight bearing (WB) condition on the kinematics of mobile-bearing total knee arthroplasty (TKA).

Methods

We examined 12 patients (19 knees) implanted with a low contact stress (LCS) mobile-bearing TKA system using a two-dimensional to three-dimensional registration technique. The in vivo kinematics of dynamic deep knee flexion under WB and non-WB (NWB) conditions were compared. We evaluated the knee range of motion, femoral axial rotation relative to the tibial component, anteroposterior translation, and kinematic pathway of the femorotibial contact point for both the medial and lateral sides.

Results

Under the WB condition, the mean range of motion was 117.8° ± 16.7°. Under the NWB condition, the mean range of motion was 111.0° ± 4.4°. The mean range of axial rotation from full extension to maximum flexion was 3.0° ± 1.5° under the WB condition and 2.2° ± 1.0° under the NWB condition. With regard to the anteroposterior translation, the LCS mobile-bearing TKA system showed the same kinematic patterns under both conditions, except for axial rotation at 0°, 10°, and 110°. From hyperextension to maximum flexion, the kinematic pattern reflected a central pivot under both conditions.

Conclusions

In conclusion, this study demonstrated that, in an LCS mobile-bearing TKA system, knee kinematics showed the same patterns under NWB and WB conditions, except for axial rotation at the early phase. Further understanding of knee kinematics could provide us with useful information for future design concepts of TKA implants.     

Biomechanical comparison of transfacet screws to lateral mass screw-rod constructs in the lower cervical spine

Purpose

Transfacet screws have been used as an alternative posterior fixation in the cervical spine. There is lack of spinal stability of the transfacet screws either as stand-along constructs or combined with anterior plate. This study was designed to evaluate spinal stability of transfacet screws following posterior ligamentous injury and combined with anterior plate, respectively, and compare transfacet screws to lateral mass screw-rod constructs.

Methods

Flexibility tests were conducted on eight cadaveric specimens in an intact and injury, and instrumented with the transfacet screw fixation and lateral mass screw-rod construct at C5–C7 levels either after section of the posterior ligamentous complex or combined with an anterior plate and a mesh cage for C6 corpectomy reconstruction. A pure moment of ±2.0 Nm was applied to the specimen in flexion–extension, lateral bending, and axial rotation. Ranges of motion (ROM) were calculated for the C5–C7 segment.

Results

ROM with the transfacet screws was 22 % of intact in flexion–extension, 9 % in lateral bending and 11 % in axial rotation, while ROM with the lateral mass screw-rod construct was 9 % in flexion–extension, 8 % in lateral bending and 22 % in axial rotation. The only significant difference between two constructs was seen in flexion–extension (5.8 ± 4.2° vs. 2.4 ± 1.2°, P = 0.002). When combined with an anterior plate and mesh cage, the transfacet screw fixation reduced ROM to 3.0° in flexion–extension, 1.2° in lateral bending, and 1.1° in axial rotation, which was similar to the lateral mass screw-rod construct.

Conclusions

This study identified the transfacet screw fixation, as stand-alone posterior fixation, was equivalent to the lateral mass screw-rod constructs in axial rotation and lateral bending except in flexion–extension. When combined with an anterior plate, the transfacet screw fixation was similar to the lateral mass screw-rod construct in motion constraint. The results suggested the transfacet screw fixation a biomechanically effective way as supplementation of anterior fixation.

     

Segmental in vivo vertebral motion during functional human lumbar spine activities

Quantitative data on the range of in vivo vertebral motion is critical to enhance our understanding of spinal pathology and to improve the current surgical treatment methods for spinal diseases. Little data have been reported on the range of lumbar vertebral motion during functional body activities. In this study, we measured in vivo 6 degrees-of-freedom (DOF) vertebral motion during unrestricted weightbearing functional body activities using a combined MR and dual fluoroscopic imaging technique. Eight asymptomatic living subjects were recruited and underwent MRI scans in order to create 3D vertebral models from L2 to L5 for each subject. The lumbar spine was then imaged using two fluoroscopes while the subject performed primary flexion-extension, left-right bending, and left-right twisting. The range of vertebral motion during each activity was determined through a previously described imaging-model matching technique at L2-3, L3-4, and L4-5 levels. Our data revealed that the upper vertebrae had a higher range of flexion than the lower vertebrae during flexion-extension of the body (L2-3, 5.4 ± 3.8°; L3-4, 4.3 ± 3.4°; L4-5, 1.9 ± 1.1°, respectively). During bending activity, the L4-5 had a higher (but not significant) range of left-right bending motion (4.7 ± 2.4°) than both L2-3 (2.9 ± 2.4°) and L3-4 (3.4 ± 2.1°), while no statistical difference was observed in left-right twisting among the three vertebral levels (L2-3, 2.5 ± 2.3°; L3-4, 2.4 ± 2.6°; and L4-5, 2.9 ± 2.1°, respectively). Besides the primary rotations reported, coupled motions were quantified in all DOFs. The coupled translation in left-right and anterior-posterior directions, on average, reached greater than 1 mm, while in the proximal-distal direction this was less than 1 mm. Overall, each vertebral level responds differently to flexion-extension and left-right bending, but similarly to the left-right twisting. This data may provide new insight into the in vivo function of human spines and can be used as baseline data for investigation of pathological spine kinematics.     

Segond’s fracture: a biomechanical cadaveric study using navigation

Background

Segond’s fracture is a well-recognised radiological sign of an anterior cruciate ligament (ACL) tear. While previous studies evaluated the role of the anterolateral ligament (ALL) and complex injuries on rotational stability of the knee, there are no studies on the biomechanical effect of Segond’s fracture in an ACL deficient knee. The aim of this study was to evaluate the effect of a Segond’s fracture on knee rotation stability as evaluated by a navigation system in an ACL deficient knee.

Materials and methods

Three different conditions were tested on seven knee specimens: intact knee, ACL deficient knee and ACL deficient knee with Segond’s fracture. Static and dynamic measurements of anterior tibial translation (ATT) and axial tibial rotation (ATR) were recorded by the navigation system (2.2 OrthoPilot ACL navigation system B. Braun Aesculap, Tuttlingen, Germany).

Results

Static measurements at 30° showed that the mean ATT at 30° of knee flexion was 5.1 ± 2.7 mm in the ACL intact condition, 14.3 ± 3.1 mm after ACL cut (P = 0.005), and 15.2 ± 3.6 mm after Segond’s fracture (P = 0.08). The mean ATR at 30° of knee flexion was 20.7° ± 4.8° in the ACL intact condition, 26.9° ± 4.1° in the ACL deficient knee (P > 0.05) and 30.9° ± 3.8° after Segond’s fracture (P = 0.005). Dynamic measurements during the pivot-shift showed that the mean ATT was 7.2 ± 2.7 mm in the intact knee, 9.1 ± 3.3 mm in the ACL deficient knee(P = 0.04) and 9.7 ± 4.3 mm in the ACL deficient knee with Segond’s fracture (P = 0.07). The mean ATR was 9.6° ± 1.8° in the intact knee, 12.3° ± 2.3° in the ACL deficient knee (P > 0.05) and 19.1° ± 3.1° in the ACL deficient knee with Segond’s lesion (P = 0.016).

Conclusion

An isolated lesion of the ACL only affects ATT during static and dynamic measurements, while the addition of Segond’s fracture has a significant effect on ATR in both static and dynamic execution of the pivot-shift test, as evaluated with the aid of navigation.

     

Prediction of normal bone anatomy for the planning of corrective osteotomies of malunited forearm bones using a three‐dimensional statistical shape model

Corrective osteotomies of the forearm based on 3D computer simulation using contralateral anatomy as a reconstruction template is an approved method. Limitations are existing considerable differences between left and right forearms, and that a healthy contralateral anatomy is required. We evaluated if a computer model, not relying on the contralateral anatomy, may replace the current method by predicting the pre‐traumatic healthy shape. A statistical shape model (SSM) was generated from a set of 59 CT scans of healthy forearms, encoding the normal anatomical variations. Three different configurations were simulated to predict the pre‐traumatic shape with the SSM (cross‐validation). In the first two, only the distal or proximal 50% of the radius were considered as pathological. In a third configuration, the entire radius was assumed to be pathological, only the ulna being intact. Corresponding experiments were performed with the ulna. Accuracy of the prediction was assessed by comparing the predicted bone with the healthy model. For the radius, mean rotation accuracy of the prediction between 2.9 ± 2.2° and 4.0 ± 3.1° in pronation/supination, 0.4 ± 0.3° and 0.6 ± 0.5° in flexion/extension, between 0.5 ± 0.3° and 0.5 ± 0.4° in radial‐/ulnarduction. Mean translation accuracy along the same axes between 0.8 ± 0.7 and 1.0 ± 0.8 mm, 0.5 ± 0.4 and 0.6 ± 0.4 mm, 0.6 ± 0.4 and 0.6 ± 0.5 mm, respectively. For the ulna, mean rotation accuracy between 2.4 ± 1.9° and 4.7 ± 3.8° in pronation/supination, 0.3 ± 0.3° and 0.8 ± 0.6° in flexion/extension, 0.3 ± 0.2° and 0.7 ± 0.6° in radial‐/ulnarduction. Mean translation accuracy between 0.6 ± 0.4 mm and 1.3 ± 0.9 mm, 0.4 ± 0.4 mm and 0.7 ± 0.5 mm, 0.5 ± 0.4 mm and 0.8 ± 0.6 mm, respectively. This technique provided high accuracy, and may replace the current method, if validated in clinical studies. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2630–2636, 2017.

     

Lumbar facet joint and intervertebral disc loading during simulated pelvic obliquity

Background contextIntervertebral disc and facet joints are the two primary load-bearing structures of the lumbar spine, and altered loading to these structures may be associated with frontal plane spinal deviations.PurposeTo determine the load on the lumbar facet joint and intervertebral disc under simulated frontal plane pelvic obliquity combined loading, an in vitro biomechanical study was conducted.Study design/settingAn in vitro biomechanical study using a repeated-measures design was used to compare L4–L5 facet joint and intervertebral disc loading across pure moment and combined loading conditions.MethodsEight fresh-frozen lumbosacral specimens were tested under five loading conditions: flexion/extension, lateral bending, axial rotation using pure moment bending (±10 Nm), and two additional tests investigating frontal plane pelvic obliquity and axial rotation (sacrum tilted left 5° and at 10° followed by a ±10-Nm rotation moment). Three-dimensional kinematics, facet load, and intradiscal pressures were recorded from the L4–L5 functional spinal unit.ResultsSagittal and frontal plane loading resulted in significantly smaller facet joint forces compared with conditions implementing a rotation moment (p<.05). The facet joint had the highest peak load during the 10° combined loading condition (124.0±30.2 N) and the lowest peak load in flexion (26.8±16.1 N). Intradiscal pressure was high in lateral flexion (495.6±280.9 kPa) and flexion (429.0±212.9 kPa), whereas intradiscal pressures measured in rotation (253.2±135.0 kPa) and 5° and 10° combined loading conditions were low (255.5±132.7 and 267.1±127.1 kPa, respectively).ConclusionsFacet loading increased during simulated pelvic obliquity in frontal and transverse planes, whereas intradiscal pressures were decreased compared with sagittal and frontal plane motions alone. Altered spinopelvic alignment may increase the loads experienced by spinal tissue, especially the facet joints.