下颈椎前路内固定联合后路经关节金属螺钉置入固定的生物力学稳定性

背景：对退变性颈椎管狭窄单纯采用前路椎体次全切除或椎间盘切除或单纯后路单开门椎管扩大成行均不能彻底完成脊髓减压和脊柱三柱稳定。目的：探讨下颈椎前路固定联合后路经关节螺钉固定的生物力学稳定性。方法：正常成人尸体颈椎标本,每具分别制作以下两种模型：①经后路C3～C7单开门和下颈椎前路C5椎体次全切除钛网支撑植骨、ORION内固定模型（对照组）。②经后路C3～C7单开门和经关节螺钉内固定及下颈椎前路C5椎体次全切除钛网内植骨、ORION内固定模型（实验组）。结果与结论：实验组在前屈、后伸、左、右侧屈及左、右旋转移位角度均小于对照组（P〈0.001）。提示：①在生物力学实验中,下颈椎前路固定联合后路经关突节螺钉固定的生物力学性能优良,对抗前屈、后伸、左、右旋转的作用力更强,颈椎可获得更可靠的稳定性。②下颈椎前路固定联合后路经关节螺钉固定在对抗颈椎前屈运动时力学稳定性更为强大。     

Biomechanical comparison of cervical discectomy/fusion model using allograft spacers between anterior and posterior fixation methods (lateral mass and pedicle screw)

BackgroundThe purpose of this study is to investigate effects of different fixation methods on the physical stress on allospacers, endplate-vertebral body, and implants using finite element model analyses.MethodsStress distribution and subsidence risk according to the fixation methods under the condition of hybrid motion control were analyzed. The detailed finite element model of a previously validated, three-dimensional, intact cervical spinal segment model, with C5–C6 segmental fusion using allospacer, was used to evaluate the biomechanical characteristics of different fixation combinations, such as anterior plate/screws, lateral mass screw, and posterior pedicle screw.FindingsThe load sharing on allospacers increased in extension in order of posterior pedicle screws (21.4%), lateral mass screws (31.5%), and anterior plate/screws (56.6%). lateral mass screw demonstrated the highest load sharing (68.1%) on the allospacer in flexion. The Peak von Mises stress of the allospacer was the lowest in flexion and axial rotation but the highest in extension with anterior plate/screws. Allospacer subsidence risk was the lowest in extension, lateral bending, and axial rotation with posterior pedicle screws but the lowest in flexion with anterior plate/screws. The bone-screw loosening risk was the lowest in all modes with posterior pedicle screws but the highest with anterior plate/screws.InterpretationPosterior pedicle screws demonstrated the best mechanical stability of allospacer failure-subsidence and the lowest risk of screw loosening. Different motion restrictions depending on the fixation method should be considered for implant and allospacer safety.     

体外生物力学评价上胸椎前路钛板内固定装置的三维运动稳定性

背景:国内外少见颈前路带锁钢板重建上胸椎的体外生物力学报道。目的:从生物力学角度评价自行研制的上胸椎前路钛板内固定装置。方法:15具成人尸体上胸椎标本分成3组,即上胸椎前路钛板内固定组(B),颈前路钛板预弯内固定组(C),颈前路钛板未预弯内固定组(D)。对完整标本进行三维活动度测量,分别安装好各组内固定再次进行标本在前屈、后伸和侧弯及旋转状态下的三维运动稳定性测量,并与完整状态(A)进行对比。结果与结论:在完整状态下B、C、D3组标本的三维运动稳定性差异无显著性意义(P>0.05)。前屈稳定性排列:B>D>C>完整,B、A之间差异有显著性意义(P=0.012);后伸稳定性排列:B>C>A>D,B与A,C,D之间差异有显著性意义(P=0.001,0.021,0.01);旋转状态下的稳定性排列:B>C>A>D,各组差异无显著性意义;侧弯稳定性排列:A>B>C>D,A和C,D之间差异有显著性(P=0.005,0.002)。提示上胸椎前路钛板装置具有较好的三维稳定性,如果采用颈前路钛板内固定建议塑型。     

体外生物力学评价上胸椎前路钛板内固定装置的三维运动稳定性

背景：国内外少见颈前路带锁钢板重建上胸椎的体外生物力学报道。目的：从生物力学角度评价自行研制的上胸椎前路钛板内固定装置。方法：15具成人尸体上胸椎标本分成3组,即上胸椎前路钛板内固定组（B）,颈前路钛板预弯内固定组（C）,颈前路钛板未预弯内固定组（D）。对完整标本进行三维活动度测量,分别安装好各组内固定再次进行标本在前屈、后伸和侧弯及旋转状态下的三维运动稳定性测量,并与完整状态（A）进行对比。结果与结论：在完整状态下B、C、D3组标本的三维运动稳定性差异无显著性意义（P〉0.05）。前屈稳定性排列：B〉D〉C〉完整,B、A之间差异有显著性意义（P=0.012）;后伸稳定性排列：B〉C〉A〉D,B与A,C,D之间差异有显著性意义（P=0.001,0.021,0.01）;旋转状态下的稳定性排列：B〉C〉A〉D,各组差异无显著性意义;侧弯稳定性排列：A〉B〉C〉D,A和C,D之间差异有显著性（P=0.005,0.002）。提示上胸椎前路钛板装置具有较好的三维稳定性,如果采用颈前路钛板内固定建议塑型。     

颈椎前路减压钛网植骨融合术后内固定早期失败原因及预防

【目的】探讨颈椎前路减压钛网植骨融合术后内固定早期失败原因及预防。【方法】回顾性分析2004年12月至2010年12月本院诊治的15例行颈椎前路内固定术后早期失败患者资料,其中男性6例,女性9例,平均年龄64（50～75）岁。所有患者均行颈椎前路椎体次全切＋钛网植骨自锁钛板固定融合术,术后予以颈部外固定支具固定。【结果】4例颈椎病神经根型,8例颈椎病脊髓型,3例颈椎骨折。3例单节段椎体次全切,10例双节段椎体次全切,2例多节段椎体次全切。术中12例采用10mm直径钛网,3例采用12mm直径钛网。钛网下沉12例,钛板及螺钉松动4例。未按要求严格佩戴外固定支具5例。所有患者内固定失败时间均小于12周。【结论】颈椎前路钛网植骨融合术早期内固定失败可能与患者年龄、固定节段长短、钛网直径、病种等因素相关。     

颈椎前路一体化钢板椎间融合器置入后与颈椎生物力学环境的匹配

背景：研究表明,颈椎一体化前路钢板融合器比现行钢板和融合器具有更多理论上的优势。但是目前有关其生物力学方面的研究国内尚无文献报道。目的：观察与评价颈椎前路一体化钢板椎间融合器内固定置入后的生物力学特征。方法：采集6具成人尸体颈椎标本,分为5组进行测试,即正常组、椎间盘摘除组、颈椎前路一体化钢板椎间融合器固定组、CBK融合器固定组及CBK融合器＋Secuplate钢板联合固定组,以C5～6椎间隙为观察对象,进行生物力学实验。结果与结论：颈椎间盘摘除后,颈椎在各个方向运动加大,刚度及强度等生物力学数值减小,脊柱失稳。与椎间盘摘除组相比,颈椎前路一体化钢板椎间融合器固定后其强度增加24%,椎体应变减小31%,刚度增加14.3%,位移减小15%（P〈0.05）,颈椎前路一体化钢板椎间融合器对颈椎的力学性能影响较小,说明它能较好地与颈椎的力学环境相匹配。CBK融合器固定后抗后伸及旋转作用相对较小,同椎间盘摘除组相比差异有显著性意义（P〈0.05）。CBK融合器＋Secuplate钢板联合固定组载荷强度和应变过大,与椎间盘摘除组相比其强度增加27%,椎体应变减小38%,刚度增加17%,位移减小17%（P〈0.05）,颈椎刚度增大且邻近椎节的运动有增大趋势,将引起力学性能的改变。提示颈椎前路一体化钢板椎间融合器结合了颈椎前路钢板和融合器生物力学方面的优点,能较好地与颈椎的力学环境相匹配。     

上胸椎前路钛板与颈前路钛板内固定装置的拔出强度实验

背景:目前尚无专门用于上胸椎前路的内固定器械,课题组自行研制的内固定器械已申请了专利,仍在进一步研究当中.目的:对自行研制的上胸椎前路钛板内固定装置与颈椎前路Orion钛板内固定装置拔出强度进行比较,探讨上胸椎前路钛板固定的可行性.方法:6例新鲜成人T2~T4尸体标本随机分为两组,即上胸椎前路钛板内固定组,颈椎前路Orion钛板内固定组,切除T3椎体和T2/3、T3/4椎间盘组织,同一尸体髂骨上取适当大小的骨块植入T3椎体缺损处,然后分别安装好内固定,在生物力学试验机上通过传感器测出固定钛板的最大拔出力并进行统计学分析.结果与结论:上胸椎前路钛板内固定装置最大拔出力平均(1 005.11±252.78) N,强于颈椎前路Orion钛板内固定装置 (469.37±142.75) N,差异有显著性意义(P < 0.05).可见自行研制的上胸椎前路钛板内固定装置拔出强度优于颈椎前路Orion钛板内固定装置,由此推断上胸椎前路内固定装置是比较牢固的,为后期临床应用奠定了实验基础.     

上胸椎前路钛板与颈前路钛板内固定装置的拔出强度实验

背景：目前尚无专门用于上胸椎前路的内固定器械,课题组自行研制的内固定器械已申请了专利,仍在进一步研究当中。目的：对自行研制的上胸椎前路钛板内固定装置与颈椎前路Orion钛板内固定装置拔出强度进行比较,探讨上胸椎前路钛板固定的可行性。方法：6例新鲜成人T2~T4尸体标本随机分为两组,即上胸椎前路钛板内固定组,颈椎前路Orion钛板内固定组,切除T3椎体和T2/3、T3/4椎间盘组织,同一尸体髂骨上取适当大小的骨块植入T3椎体缺损处,然后分别安装好内固定,在生物力学试验机上通过传感器测出固定钛板的最大拔出力并进行统计学分析。结果与结论：上胸椎前路钛板内固定装置最大拔出力平均（1005.11±252.78）N,强于颈椎前路Orion钛板内固定装置（469.37±142.75）N,差异有显著性意义（P〈0.05）。可见自行研制的上胸椎前路钛板内固定装置拔出强度优于颈椎前路Orion钛板内固定装置,由此推断上胸椎前路内固定装置是比较牢固的,为后期临床应用奠定了实验基础。     

改良解剖型颈椎钛网在颈椎前路椎体次全切术中的三维有限元分析

[目的]探讨改良解剖型颈椎钛网在颈椎前路椎体次全切除融合术(anterior cervical corpectomy and fusion,ACCF)中的生物力学分布特点.[方法]建立正常人C3～C7的三维有限元模型,模拟ACCF过程,分别装配传统颈椎钛网及改良解剖型钛网,并对模型施加40 N的预载荷及1.5 Nm的运动附加力,使模型产生前屈、后伸、侧倾及旋转运动,比较两种钛网植骨方式对钛网、椎体及钛网对终板-钛网界面应力分布的差异.[结果]在前屈、后伸、左倾、右倾、左转、右转等6种不同的工况下,传统颈椎钛网最大的等效应力值分别为73.782、177.36、124.42、100.85、191.64及221.91 MPa,新型改良钛网的最大等效应力值分别为31.028、62.236、46.053、44.337、41.549及39.255 MPa,新型改良钛网的椎体应力分布远小于传统钛网,改良钛网C4及C6终板-钛网接触面的应力小于传统钛网相应接触点的应力. [结论]在ACCF中应用改良解剖型颈椎钛网可有效避免终板应力过度集中,理论上可以降低钛网下沉的发生率.     

Biomechanical comparison of the angle of inserted screws and the length of anterior cervical plate systems with allograft spacers

BackgroundComparative studies of the biomechanical effects of plates of varying lengths and different screw insertion angles on allograft spacers are lacking.MethodsFinite element model analysis of a previously validated, three-dimensional, intact cervical spinal segment model of C3–6 was conducted in the present study. On the C5–6 segment, anterior discectomy and fusion were performed using allograft spacers and different combinations of anterior plates and screws. The biomechanical characteristics of combinations of short, medium, and maximal length plates with screw insertion angles of 0°, 8°, 16°, and 32° were analyzed.FindingsIn flexion and extension, the risk of allograft spacer subsidence decreased as screw angles increased. Short plates with a screw insertion angle of 32° posed the lowest subsidence risk, similar to medium length plates with a screw insertion angle of 16°, in all motion conditions. The risk of bone yielding increased as plate length increased, but decreased as the screw insertion angle increased.InterpretationShort plates with a large screw insertion angle (32°) showed the highest mechanical stability and load sharing of allograft spacers and the lowest risk of screw loosening. Accordingly, we recommend the use of a short plate and large screw insertion angle for anterior cervical discectomy and fusion.     

颈椎动态稳定器置入非融合颈椎的生物力学分析

背景：颈椎动态稳定器的解剖型设计与正常椎间盘应具有相似的生物力学特点,其动态性设计具有轴向顺应性以及震荡吸收功能,而前缘倒齿嵌入上下椎体可获得足够的轴向稳定性。目的：比较颈椎前路融合内固定和颈椎动态稳定器置入非融合后颈椎相关生物力学指标变化。方法：将6具新鲜人C2～ C7颈段脊柱标本随机分为3组,在完整颈椎测试后分别行C5、6前路减压颈椎动态稳定器DCI置入,C5、6前路减压单纯Cage融合内固定,C5、6前路减压颈椎前路一体化钢板椎间融合器融合内固定。检测各组标本前屈、后伸、左右侧屈不同生理运动工况并施加2.0N·m纯力偶矩,颈椎标本C5～ 6上下邻近节段手术前后活动度大小。结果与结论：3种内固定后C5～ 6上下邻近节段较正常颈椎标本前屈、后伸和左右侧屈关节活动度值均有所增加,且表现出良好的即时稳定性,但颈椎动态稳定器置入组最接近正常值;3组间C5～ 6上下邻近节段关节活动度差异无显著性意义。表明颈椎动态稳定器置入后对邻近节段椎体活动度无明显影响或影响甚小,在一定程度上减小假体与其邻近椎体轴向应力,有效地维持颈椎活动。     

Biomechanical comparison of the stable efficacy of two anterior plating systems

OBJECTIVE: To compare the immediate stable efficacy and load sharing effect of two types of anterior cervical screw-plating instrumentations: the Morscher Synthes titanium locking screw-plate system and the Caspar trapezoidal screw-plate system. DESIGN: Fresh porcine cervical spines with intact, two surgery unstable models, and then reconstructed with or without screw-plating instruments were compared in three physiological loading conditions. BACKGROUND: Two markedly instrumentation systems--Morscher Synthes titanium cervical locking screw-plate and Caspar trapezoidal screw-plate systems are commonly used in management of complex cervical spine disorders. Although the biomechanical study showed that the lower cost Caspar system performed superior in extension before and after plate fatigue, the clinic evaluations of two systems were contradictory. So (1) does the titanium cervical locking plate system pay for its higher cost? and (2) what is the load sharing character of strut graft in one level corpectomy?METHODS: Eight fresh ligamentous porcine cervical spines from C3 to C7 were undergone axial compression, rotation and sagittal flexion tests. The biomechanical experiment was sequentially repeated for the intact, C5-6 discectomy, C5 corpectomy, and then stabilized by either type of plate fixation devices with or without polymethylmethacrylate bone cement grafting. Strains measured by an extensometer across the operated motion segment were used as the index of stability. RESULTS: Analysis of the strain data showed both types of anterior fixation plate systems provided adequate-restored stability for the spinal column only aided with polymethylmethacrylate construction. Statistically, there was no significant difference in biomechanical evaluation for the stability effect between much cost Morscher Synthes plate and Caspar plate system (p<0.005). The spinal disc bore as much as 75% of axial loading. While the strut graft functioned as the disc substitute and spacer, it bore more than 90% of axial loading. In high degree of flexion, the transmitted compressive load was shifted anteriorly to the screw-plate. This might unload the polymethylmethacrylate graft and resulted in the strut graft in tensile fatigue failure. CONCLUSIONS: Statistically both systems showed similar stable efficacy, however, the Morscher Synthes cervical locking plate system might provide better stable effect in higher degrees of flexion motion. The strut graft played as the major load-bearing role in axial compression and sagittal flexion, while in axial rotation, the applied torque was mainly resisted by facet joint and screw-plate system complex. RELEVANCE: The minor discrepancy of two plating systems may be due to the nature of plate geometry and design but not the material properties. Combination of bone graft and either plating systems provides adequate fusion stability under physiological loadings. The high degree flexion may cause the posterior portion of polymethylmethacrylate graft in tensile fracture and then result in polymethylmethacrylate failure in clinic observation.     

Biomechanics of anterior plating failure in treating distractive flexion injury in the caudal subaxial cervical spine

BackgroundOperative level is a potential biomechanical risk factor for construct failure during anterior fixation for distractive flexion injury. No biomechanical study of this concept has been reported, although it is important in clinical management.MethodsTo explore the mechanism of this concept, a previously validated three-dimensional C2-T1 finite element model was modified to simulate surgical procedure via the anterior approach for treating single-level distractive flexion injury, from C2-C3 to C7-T1. Four loading conditions were used including no-compression, follower load, axial load, and combined load. Construct stability at the operative level was assessed.FindingsUnder these loading conditions with the head's weight simulated, segmental stability decreases when the operative level shifts cephalocaudally, especially at C6-C7 and C7-T1, the stress of screw-bone interface increases cephalocaudally, and in the same operative level, the caudal screws always carries more load than the cephalad ones. All these predicted results are consistent with failure patterns observed in clinical reports. In the contrast, under other loading conditions without the weight of head, no obvious segmental divergence was predicted.InterpretationThis study supports that the biomechanical mechanism of this phenomenon includes eccentric load from head weight during sagittal movements and difference of moment arms. Our study suggests that anterior fixation is not recommended for treating distractive flexion injury at the caudal segments of the subaxial cervical spine, especially at C6-C7 and C7-T1, because of the intrinsic instability in these segments. Combined posterior rigid fixation with anterior fixation should be considered for these segments.     

Posterior cervical spine crisscross fixation: Biomechanical evaluation

BackgroundBiomechanical/anatomic limitations may limit the successful implantation, maintenance, and risk acceptance of posterior cervical plate/rod fixation for one stage decompression-fusion. A method of posterior fixation (crisscross) that resolves biomechanical deficiencies of previous facet wiring techniques and not reliant upon screw implantation has been devised. The biomechanical performance of the new method of facet fixation was compared to the traditional lateral mass plate/screw fixation method.MethodsThirteen human cadaver spine segments (C2-T1) were tested under flexion-compression loading and four were evaluated additionally under pure-moment load. Preparations were evaluated in a sequence of surgical alterations with intact, laminectomy, lateral mass plate/screw fixation, and crisscross facet fixation using forces, displacements and kinematics.FindingsCombined loading demonstrated significantly lower bending stiffness (p < 0.05) between laminectomy compared to crisscross and lateral mass plate/screw preparations. Crisscross fixation showed a comparative tendency for increased stiffness. The increased overall motion induced by laminectomy was resolved by both fixation techniques, with crisscross fixation demonstrating a comparatively more uniform change in segmental motions.InterpretationThe crisscross technique of facet fixation offers immediate mechanical stability with resolution of increased flexural rotations induced by multi-level laminectomy. Many of the anatomic limitations and potentially deleterious variables that may be associated with multi-level screw fixation are not associated with facet wire passage, and the subsequent fixation using a pattern of wire connection crossing each facet joint exhibits a comparatively more uniform load distribution. Crisscross wire fixation is a valuable addition to the surgical armamentarium for extensive posterior cervical single-stage decompression-fixation.     

钛笼植骨融合联合钢板内固定在颈前路融合术中的应用

目的 探讨颈前路椎体次全切除钛笼植骨融合联合锁定钢板内固定术的手术方法与临床疗效.方法 对24例颈椎骨折、脱位伴截瘫,无骨折脱位型颈髓损伤及颈椎病患者行椎体次全切除减压钛笼植骨融合联合锁定钢板内固定术.结果 所有患者均获得随访,时间6～24个月,平均13个月,其中1例患者术后1个月出现钛笼下沉(3个月后未见继续下沉),所有患者椎体间3～5个月全部获得融合,未见有钢板螺丝钉松动、断裂.术后所有患者神经功能评价Frankel分级较术前均有1～2个级别的提高.结论 虽然颈前路椎体次全切除钛笼植骨融合联合锁定钢板内固定术有钛网下沉、颈椎邻近椎体退变等并发症的可能,但只要术中正确仔细的操作,术后仍能获得较好的椎体融合和神经恢复,临床疗效满意,是目前颈前路融合术中一种有效的手术方法.     

Does pedicle screw fixation of the subaxial cervical spine provide adequate stabilization in a multilevel vertebral body fracture model? An in vitro biomechanical study

BackgroundCervical vertebral body fractures generally are treated through an anterior-posterior approach. Cervical pedicle screws offer an alternative to circumferential fixation. This biomechanical study quantifies whether cervical pedicle screws alone can restore the stability of a three-column vertebral body fracture, making standard 360° reconstruction unnecessary.MethodsRange of motion (2.0 Nm) in flexion-extension, lateral bending, and axial rotation was tested on 10 cadaveric specimens (five/group) at C2–T1 with a spine kinematics simulator. Specimens were tested for flexibility of intact when a fatigue protocol with instrumentation was used to evaluate construct longevity. For a C4–6 fracture, spines were instrumented with 360° reconstruction (corpectomy spacer + plate + lateral mass screws) (Group 1) or cervical pedicle screw reconstruction (C3 and C7 only) (Group 2).FindingsResults are expressed as percentage of intact (100%). In Group 1, 360° reconstruction resulted in decreased motion during flexion-extension, lateral bending, and axial rotation, to 21.5%, 14.1%, and 48.6%, respectively, following 18,000 cycles of flexion-extension testing. In Group 2, cervical pedicle screw reconstruction led to reduced motion after cyclic flexion-extension testing, to 38.4%, 12.3%, and 51.1% during flexion-extension, lateral bending, and axial rotation, respectively.InterpretationThe 360° stabilization procedure provided the greatest initial stability. Cervical pedicle screw reconstruction resulted in less change in motion following cyclic loading with less variation from specimen to specimen, possibly caused by loosening of the shorter lateral mass screws. Cervical pedicle screw stabilization may be a viable alternative to 360° reconstruction for restoring multilevel vertebral body fracture.     

氮化纯钛颈椎植骨融合器的研制及生物力学测试

目的:根据国人颈椎特点设计研制了一种经氮化处理的纯钛植骨融合器,并进行生物力学测试。方法:取12具新鲜成年男性颈椎标本,分别处理成包含单、双运动功能单位的试样,模拟前路植骨及植人融合器,进行前屈、后伸、侧弯、扭转四个方面的测试,比较本融合器植人后与完整颈椎及单纯椎间植骨的稳定性,经统计学分析后自编程序拟合出载荷—位移曲线和扭矩一扭转角曲线。同时进行疲劳强度和强度破坏试验。结果:融合器植人后颈椎在各方向运动中的稳定性均明显强于单纯椎间植骨,也较完整颈椎运动功能单位稳定。结论:纯钛颈椎植骨融合器适用于前路间盘摘除减压手术的椎间固定融合,尤其是多节段病变的病例。     

Biomechanical evaluation of anterior lumbar interbody fusion with various fixation options: Finite element analysis of static and vibration conditions

BackgroundAnterior lumbar interbody fusion combined with supplementary fixation has been widely used to treat lumbar diseases. However, few studies have investigated the influence of fixation options on facet joint force and cage subsidence. The aim of this study was to explore the biomechanical performance of anterior lumbar interbody fusion with various fixation options under both static and vertical vibration loading conditions.MethodsA previously validated finite element model of the intact L1–5 lumbar spine was employed to compare five conditions: (1) Intact; (2) Fusion alone; (3) Fusion combined with anterior lumbar plate; (4) Fusion combined with Coflex-F fixation; (5) Fusion combined with bilateral pedicle screw fixation. The models were analyzed under static and vertical vibration loading conditions respectively.FindingsBilateral pedicle screws provided highest stability at surgical level. Applying supplementary fixation diminished the dynamic responses of lumbar spine. Compared with anterior lumbar plate and Coflex-F device, bilateral pedicle screws decreased the stress responses of the endplates and cage under both static and vibration conditions, while increased the facet joint force at adjacent levels. As for comparison between Coflex-F device and anterior lumbar plate, results showed a similarity in biomechanical performance under static loading, and a slightly higher dynamic response of the latter under vertical vibration.InterpretationThe biomechanical performance of lumbar spine was significantly influenced by the variation of fixations under both static and vibration conditions. Bilateral pedicle screws showed advantages in stabilizing surgical segment and relieving cage subsidence, but may increase the facet joint force at adjacent levels.     

颈椎前路一体化钢板椎间融合器置入后与颈椎生物力学环境的匹配

背景:研究表明,颈椎一体化前路钢板融合器比现行钢板和融合器具有更多理论上的优势。但是目前有关其生物力学方面的研究国内尚无文献报道。目的:观察与评价颈椎前路一体化钢板椎间融合器内固定置入后的生物力学特征。方法:采集6具成人尸体颈椎标本,分为5组进行测试,即正常组、椎间盘摘除组、颈椎前路一体化钢板椎间融合器固定组、CBK融合器固定组及CBK融合器+Secuplate钢板联合固定组,以C5～6椎间隙为观察对象,进行生物力学实验。结果与结论:颈椎间盘摘除后,颈椎在各个方向运动加大,刚度及强度等生物力学数值减小,脊柱失稳。与椎间盘摘除组相比,颈椎前路一体化钢板椎间融合器固定后其强度增加24%,椎体应变减小31%,刚度增加14.3%,位移减小15%(P<0.05),颈椎前路一体化钢板椎间融合器对颈椎的力学性能影响较小,说明它能较好地与颈椎的力学环境相匹配。CBK融合器固定后抗后伸及旋转作用相对较小,同椎间盘摘除组相比差异有显著性意义(P<0.05)。CBK融合器+Secuplate钢板联合固定组载荷强度和应变过大,与椎间盘摘除组相比其强度增加27%,椎体应变减小38%,刚度增加17%,位移减小17%(P<0.05),颈椎刚度增大且邻近椎节的运动有增大趋势,将引起力学性能的改变。提示颈椎前路一体化钢板椎间融合器结合了颈椎前路钢板和融合器生物力学方面的优点,能较好地与颈椎的力学环境相匹配。     

Anterior cervical corpectomy decompression and fusion for cervical kyphosis in a girl with Ehlers-Danlos syndrome:A case report

BACKGROUND Spinal deformities in Ehlers-Danlos syndrome(EDS; type VI) are generally progressive and severe. Surgical treatment has been described for kyphoscoliosis in the thoracolumbar spine. However, there are few studies describing the consequences of an anterior approach in cervical kyphosis. An anterior approach may not be able to fully decompress the spinal canal and restore the normal curvature of the cervical spine. Therefore, the anterior approach for cervical kyphosis in young children is hard. We describe the first case in an EDS girl with cervical kyphosis who received satisfactory anterior cervical corpectomy decompression and fusion.CASE SUMMARY The chief complaints of a 16-year-old girl with EDS were double upper limb weakness for 7 years and double lower limb walking instability for 2 years.Moreover, the imaging results revealed that the degree of kyphosis from cervical vertebra 2 to 4 accompanying with spinal cord compression was 30°. An anterior cervical corpectomy involving cervical vertebra 3 and a titanium mesh implant were performed with internal fixation. The results at 3 mo after surgery demonstrated that the anterior fusion was solid, and the kyphosis of the cervical spine was corrected. Additionally, the power of all four extremities was significantly improved.CONCLUSION The incidence rate of cervical kyphosis in EDS is rare. The surgical treatment for these patients, especially an anterior approach, is challenging. Therefore, to develop safer and more effective strategies to treat cervical kyphosis in EDS,there is still much work to do.