颈椎前路钛网钢板内固定及自体髂骨植骨在不同颈椎节段中的生物力学研究

目的 采用颈椎前路钛网钢板及自体髂骨植骨对不同颈椎节段进行内固定，分析其生物力学改变。方法 取自愿捐赠的6具新鲜尸体C3～7标本，C5、C5.6及C4～6椎体次全切除后，分别行髂骨植骨和钛网前路钢板内固定术，测量各节段的前屈、后伸、左、右侧弯及左、右旋转运动变化，以完整标本作为对照组。结果 自体髂骨的植入使失稳颈椎的稳定性提高，其侧弯、屈伸运动度减少，与对照组比较，差异有统计学意义（P〈0．05），但抗旋转运动减少不明显（P〉0．05）。不同颈椎节段开槽减压椎间撑开钛网前路钢板内固定状态下，手术节段的即刻稳定性比对照组及撑开植骨状态增加（P〈0．05）。结论 颈椎前路椎体次全切除之后，植骨仅能部分改善其稳定性，但应用颈椎前路钛网钢板内固定可明显增强颈椎的稳定性，也较完整颈椎运动功能单位稳定。     

早期前路减压植骨加CSLP系统内固定治疗下颈椎骨折脱位

目的　总结早期前路减压植骨融合加CSLP固定系统治疗下颈椎骨折脱位的经验。方法　下颈椎前路减压后用自体髂骨植入加CSLP内固定。结果　 6 1例患者经 8个月～ 4年随访观察 ,所有的病例植骨均完全愈合。按Frankel分级 ,术后神经功能恢复良好。结论　颈椎带锁钢板具有高度的内在稳定性 ,操作简便、安全、并发症少 ,生物相容性良好 ,无磁性等优点。只要患者全身状况允许 ,一周内行前路减压植骨融合加CSLP系统内固定有利于脊髓生理功能的恢复及保持颈椎稳定性。     

颈椎前路限制性与非限制性钛板固定稳定性比较的实验研究

目的：分析比较颈椎前路非限制性钛板与限制性钛板固定的三维稳定性.方法：采用6具成人新鲜颈椎标本（C2～T1）,在MTS脊柱三维运动系统上先后测量C5/6完整、椎间盘摘除、椎间单纯植骨、限制性钛板及非限制性钛板固定状态下C5～C6节段在前屈、后伸、左右侧弯及旋转时的活动范围（ROM）.结果：单节段椎间盘摘除可造成颈椎明显失稳,单纯椎间植骨可维持颈椎的稳定性.限制性与非限制钛板固定均可以显著提高固定节段的稳定性,在屈伸及旋转运动中两种钛板之间无显著性差异,在侧弯运动时限制性钛板稳定性高于非限制性钛板.结论：在单节段颈椎减压植骨融合时前路限制性与非限制性钛板均可以显著提高固定节段的稳定性.     

前路带锁钢板治疗严重颈椎损伤

目的 :评价AO颈椎前路带锁钢板 (cervicalspinelockingplate ,CSLP)在严重颈椎损伤中的应用效果。 方法 :对 10例颈椎骨折脱位伴截瘫或不全截瘫患者行颈椎前路减压、植骨融合 ,并采用CSLP内固定。结果 :经平均 18个月随访 ,全组病例植骨融合良好 ,未发现钢板螺钉松动、断裂等并发症。结论 :CSLP具有高度的内在稳定性 ,操作简单、安全、并发症少 ,内固定材料生物相容性好、无磁性 ,适用于颈椎骨折、脱位的治疗。     

颈椎前路融合后相邻节段的即刻运动范围

目的观察中下颈椎前路单椎体次全切除减压植骨和应用颈椎前路钢板固定对相邻节段即刻三维运动范围的影响.方法采用6具新鲜成人尸体颈椎标本,测量完整状态、C5椎体次全切除减压植骨、C5椎体次全切除减压植骨颈前路钢板固定3种状态上下相邻节段的三维六自由度运动范围.结果3种状态下相邻节段的即刻三维运动范围无显著差异.结论中下颈椎前路单椎体次全切除减压植骨和应用钢板内固定对相邻节段即刻运动范围没有显著影响,颈椎前路融合后相邻节段退变加快的原因需要进一步探讨.     

四种颈椎前路钢板的临床应用比较

目的 探讨叫种颈椎前路钢板的优缺点及临床应用价值.方法 采用Caspar、Codman、AO(CSLP)及Orion四种颈椎前路钢板行颈前路植骨加钢板内固定治疗颈椎疾患145例,随访6～18个月,观察各固定系统的稳定性、融合率及并发症.结果 93.7%(136/145例)患者神经功能获得不同程度的恢复.4种钢板螺钉固定系统融合率无显著差别,术后无钢板螺钉断裂、松动、植骨块脱出等并发症.结论 四种颈前路钢板对稳定颈椎、促进植骨融合、恢复和维持椎间高度及生理曲度均具有积极意义.Orion钢板螺钉系统固定效果更好,且更易操作.     

早期前路减压植骨加CSLP系统内固定治疗下颈椎骨折脱位

目的 总结早期前路减压植骨融合加CSLP固定系统治疗下颈椎骨折脱位的经验。方法 下颈椎前路减压后用自体髂骨植入加CSLP内固定。结果 61例患者经8个月－4年随访观察,所有的病例植骨均完全愈合。按Frankel分级,术后神经功能恢复良好。结论 颈椎带锁钢板具有高度的内在稳定性,操作简便、安全、并发症少,生物相容性良好,无磁性等优点。只要患者全身状况允许,一周内行前路减压植骨融合加CSLP系统内固定有利于脊髓生理功能的恢复及保持颈椎稳定性。     

高原颈椎前路椎间融合后不同固定方式的生物力学特性的研究

[目的]分析比较颈椎前路椎间融合后不同固定方式的生物力学特性.[方法]建立正常高原人C5/6的三维有限元模型.利用有限元软件ANSA13.0.2对模型进行有限元网格划分,最后加入韧带和关节囊,通过模拟前路手术摘除椎间盘建立椎间植骨融合的有限元模型,加入前路内固定器及后路椎弓根系统三种三维有限元模型.各模型施加前屈/后伸,左/右侧弯,左/右旋转6种生理载荷,模拟颈椎6个方向的生理活动.[结果]前路和后路2种固定方式均明显减少了前路椎体融合植骨块的应力,后路固定较前路固定更减少了植骨块的应力.主要的应力集中在椎体和螺钉交界处,不同方向运动上下螺钉承受的应力没明显差异.[结论]前路椎体间融合后通过前路和后路固定均可以降低植骨块的应力,达到手术后的初始稳定性,后路椎弓根固定在前路融合后其生物力学的稳定性强于前路钢板固定.     

早期前路减压内固定治疗下颈椎骨折伴不完全截瘫

目的 总结早期前路减压植骨融合加CSLP(Cervical Spine Locking P1ate，CSLP)固定治疗下颈椎骨折伴不完全截截的经验。方法 下颈椎前路减压后用自体髂骨植入加CSLP内固定。结果 15例患经8个月～3年随访观察，所有的病例植骨均完全愈合。按Frankel分级，术后神经功能恢复良好。结论 颈椎前路减压骨加AO带锁钢板具有较高的内在稳定性，操作简便、安全、并发症少、生物相容性好、无磁性等优点。有利于脊髓生理功能的恢复及保持颈椎的生理稳定性。     

四种颈椎前路钢板在颈椎融合手术中应用和比较

目的:观察和比较4种颈椎前路钢板在颈椎前路融合手术中的优点和不足.方法:101例颈椎病、颈椎后纵韧带骨化症(OPLL)无骨折脱位型颈髓损伤患者进行前路椎间盘减压、植骨融合同时分别采用AO、Caspar、Orion和Zephire颈椎前路固定系统固定.与单纯植骨融合组比较手术时间、出血量、术后并发症、术后症状体征缓解程度和融合情况.结果:患者症状特征术后明显改善;未发现手术并发症,颈椎前路钢板固定组融合率明显优于单纯植骨融合组.结论:4类钢板均能提供充分的颈椎稳定性,使用安全,Zephire钢板较其余钢板系统使用更为简便.     

Biomechanics of an integrated interbody device versus ACDF anterior locking plate in a single-level cervical spine fusion construct

Background contextNo profile, integrated interbody cages are designed to act as implants for cervical spine fusion, which obviates the need for additional internal fixation, combining the functionality of an interbody device and the stabilizing benefits of an anterior cervical plate. Biomechanical data are needed to determine if integrated interbody constructs afford similar stability to anterior plating in single-level cervical spine fusion constructs.PurposeThe purpose of this study was to biomechanically quantify the acute stabilizing effect conferred by a single low-profile device design with three integrated screws (“anchored cage”), and compare the range of motion reductions to those conferred by a standard four-hole rigid anterior plate following instrumentation at the C5–C6 level. We hypothesized that the anchored cage would confer comparable postoperative segmental rigidity to the cage and anterior plate construct.Study designBiomechanical laboratory study of human cadaveric spines.MethodsSeven human cadaveric cervical spines (C3–C7) were biomechanically evaluated using a nondestructive, nonconstraining, pure-moment loading protocol with loads applied in flexion, extension, lateral bending (right+left), and axial rotation (left+right) for the intact and instrumented conditions. Range of motion (ROM) at the instrumented level was the primary biomechanical outcome. Spines were loaded quasi-statically up to 1.5 N-m in 0.5 N-m increments and ROM at the C5–C6 index level was recorded. Each specimen was tested in the following conditions:1. Intact2. Discectomy+anchored cage (STA)3. Anchored cage (screws removed)+anterior locking plate (ALP)4. Anchored cage only, without screws or plates (CO)ResultsROM at the C5–C6 level was not statistically different in any motion plane between the STA and ALP treatment conditions (p>.407). STA demonstrated significant reductions in flexion/extension, lateral bending, and axial rotation ROM when compared with the CO condition (p<.022).ConclusionsIn this in vitro biomechanical study, the anchored cage with three integrated screws afforded biomechanical stability comparable to that of the standard interbody cage+anterior plate cervical spine fusion approach. Due to its low profile design, this anchored cage device may avoid morbidities associated with standard anterior plating, such as dysphagia.     

Biomechanical comparison of anterior cervical plating and combined anterior/lateral mass plating.

BACKGROUND CONTEXT: Previous studies showed anterior plates of older design to be inadequate for stabilizing the cervical spine in all loading directions. No studies have investigated enhancement in stability obtained by combining anterior and posterior plates. PURPOSE: To determine which modes of loading are stabilized by anterior plating after a cervical burst fracture and to determine whether adding posterior plating further significantly stabilizes the construct. STUDY DESIGN/SETTING: A repeated-measures in vitro biomechanical flexibility experiment was performed to investigate how surgical destabilization and subsequent addition of hardware components alter spinal stability. PATIENT SAMPLE: Six human cadaveric specimens were studied. OUTCOME MEASURES: Angular range of motion (ROM) and neutral zone (NZ) were quantified during flexion, extension, lateral bending, and axial rotation. METHODS: Nonconstraining, nondestructive torques were applied while recording three-dimensional motion optoelectronically. Specimens were tested intact, destabilized by simulated burst fracture with posterior distraction, plated anteriorly with a unicortical locking system, and plated with a combined anterior/posterior construct. RESULTS: The anterior plate significantly (p<.05) reduced the ROM relative to normal in all modes of loading and significantly reduced the NZ in flexion and extension. Addition of the posterior plates further significantly reduced the ROM in all modes of loading and reduced the NZ in lateral bending. CONCLUSIONS: Anterior plating systems are capable of substantially stabilizing the cervical spine in all modes of loading after a burst fracture. The combined approach adds significant stability over anterior plating alone in treating this injury but may be unnecessary clinically. Further study is needed to assess the added clinical benefits of the combined approach and associated risks.     

下颈椎后路内固定器对失稳颈椎固定作用的生物力学评价

目的 评价下颈椎后路内固定器重建失稳颈椎稳定性的生物力学性能。方法 5具新鲜颈椎尸体标本制造脱位模型后依次用棘突钢丝、侧块螺钉、自制螺钉、椎弓根螺钉固定，用脊柱三维运动测量系统测算其运动范围。结果 棘突钢丝在屈伸和侧弯时的运动范围可恢复完整颈椎水平，但旋转时的运动范围比完整颈椎大。侧块螺钉和自制螺钉的运动范围均较完整颈椎小，且侧弯和旋转的运动范围明显小于棘突钢丝。椎弓根螺钉侧弯和旋转的运动范围最小。内固定相邻节段的运动范围虽有变化，但差异无显著性(P＞0．05)。结论 棘突钢丝可重建失稳颈椎的屈伸稳定性，但侧弯和旋转稳定性欠佳，侧块螺钉和自制螺钉优于棘突钢丝，椎弓根螺钉的稳定性最强。     

Biomechanical evaluation of occipitocervicothoracic fusion: impact of partial or sequential fixation

BACKGROUND CONTEXT: Surgical instrumentation used for posterior craniocervical instability has evolved from simple wiring techniques to sophisticated implant systems that incorporate multiple means of rigid fixation for the cervical spine. Polyaxial screws and lamina hooks in conjunction with occipital plating and transitional rods for caudal fixation theoretically allow for fixation points at each vertebra along the posterior aspect of the cervical spine. However, the potential for anatomical constraints to prevent intraoperative instrumentation at the desired vertebral level exists. The biomechanical implications of such "skipped segments" have not been well documented. PURPOSE: The purpose of this study was to determine the biomechanical effects of partial three-point fixation versus sequential fixation at all levels of the cervical spine from the occiput to T1. STUDY DESIGN/SETTING: Fresh frozen human cadaveric cervical spines from the occiput (CO) to T1 were prepared and mounted on a spine simulator. Motion was assessed by a three-dimensional optoelectronic motion measurement system. Kinematic data were collected and range of motion (ROM) was analyzed and reported. METHODS: Eight human noninstrumented intact spines (Treatment 1) were tested for baseline ROM which was subclassified into axial (CO-C2), upper subaxial (C2-C4), lower subaxial (C4-T1), and total (CO-T1) ROM. Flexion extension, lateral bending, and axial torsion testing with an applied +/-3Nm moment was conducted. The same testing protocol was performed after three-point fixation in which screws were placed at the CO, C4, and T1 (Treatment 2), and also after sequential fixation at all levels from CO through T1 (Treatment 3). Fixation was achieved using an occipital plate, 12-mm lateral mass screws for C3 through C6, and 20-mm lateral mass or pedicle screws were used for C1, C2, C7, and T1. RESULTS: Intact spine testing (Treatment 1) showed statistically significant larger ROM for all segments and for overall ROM when compared with both Treatment 2 (partial fixation CO, C4, and T1) and Treatment 3 (sequential fixation at all levels from the occiput to T1). When comparing Treatment 2 with Treatment 3, no significant difference in flexion extension ROM was detected between axial, upper subaxial, lower subaxial, and total overall ROM (p > .05). Lateral bending showed statistically significant increased ROM for Treatment 2 constructs compared with Treatment 3 constructs in total overall lateral bend ROM. For axial rotation, there was significantly increased ROM for Treatment 2 at the lower subaxial segment and total overall ROM (p < .05) when compared with Treatment 3. CONCLUSIONS: There was no statistical difference between the three-point fixation treatment group and the sequential fixation group in flexion extension bending. Lateral bending and axial rotation demonstrated an increase in total overall ROM with partial fixation compared with fixation at all levels. Axial rotation in particular showed increased mobility in the lower cervical spine for the partial fixation group. In the instance where surgeons are not able to apply sequential fixation at diseased levels, especially for the lower subaxial cervical spine, particular attention to limitation of lateral bending and axial rotation by the use of external orthotics must be considered.     

Biomechanical comparison of two-level cervical locking posterior screw/rod and hook/rod techniques.

BACKGROUND CONTEXT: Locking posterior instrumentation in the cervical spine can be attached using 1) pedicle screws, 2) lateral mass screws, or 3) laminar hooks. This order of options is in order of decreasing technical difficulty and decreasing depth of fixation, and is thought to be in order of decreasing stability. PURPOSE: We sought to determine whether substantially different biomechanical stability can be achieved in a two-level construct using pedicle screws, lateral mass screws, or laminar hooks. Secondarily, we sought to quantify the differential and additional stability provided by an anterior plate. STUDY DESIGN: In vitro biomechanical flexibility experiment comparing three different posterior constructs for stabilizing the cervical spine after three-column injury. METHODS: Twenty-one human cadaveric cervical spines were divided into three groups. Group 1 received lateral mass screws at C5 and C6 and pedicle screws at C7; Group 2 received lateral mass screws at C5 and C6 and laminar hooks at C7; Group 3 received pedicle screws at C5, C6, and C7. Specimens were nondestructively tested intact, after a three-column two-level injury, after posterior C5-C7 rod fixation, after two-level discectomy and anterior plating, and after removing posterior fixation. Angular motion was recorded during flexion, extension, lateral bending, and axial rotation. Posterior hardware was subsequently failed by dorsal loading. RESULTS: Laminar hooks performed well in resisting flexion and extension but were less effective in resisting lateral bending and axial rotation, allowing greater range of motion (ROM) than screw constructs and allowing a significantly greater percentage of the two-level ROM to occur across the hook level than the screw level (p<.03). Adding an anterior plate significantly improved stability in all three groups. With combined hardware, Group 3 resisted axial rotation significantly worse than the other groups. Posterior instrumentation resisted lateral bending significantly better than anterior plating in all groups (p<.04) and resisted flexion and axial rotation significantly better than anterior plating in most cases. Standard deviation of the ROM was greater with anterior than with posterior fixation. There was no significant difference among groups in resistance to failure (p=.74). CONCLUSIONS: Individual pedicle screws are known to outperform lateral mass screws in terms of pullout resistance, but they offered no apparent advantage in terms of construct stability or failure of whole constructs. Larger standard deviations in anterior fixation imply more variability in the quality of fixation. In most loading modes, laminar hooks provided similar stability to lateral mass screws or pedicle screws; caudal laminar hooks are therefore an acceptable alternative posteriorly. Posterior two-level fixation is less variable and slightly more stable than anterior fixation. Combined instrumentation is significantly more stable than either anterior or posterior alone.     

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.

     

生物衍生肌腱双侧关节突交叉固定动力重建颈椎后柱动态稳定性的体外生物力学研究

目的对于颈椎后柱不稳定进行动态稳定性重建研究鲜有报道。探讨采用冻干处理的生物衍生肌腱动力重建颈椎后柱动态稳定性的生物力学性能。方法收集死亡捐献者残肢掌长屈肌腱及掌伸肌腱制备生物衍生肌腱。20个新鲜成年山羊颈椎标本(C1～7),随机分为4组,每组5个标本。A组为完整标本组,B组为损伤模型组,C组为后柱钉棒固定组,D组为肌腱动力重建组。B、C、D组通过破坏颈椎后方韧带复合体制作屈曲分离型损伤模型,C组用侧块螺钉经后路固定,D组用生物衍生肌腱行侧块经关节突交叉固定。用脊柱三维运动测量系统测算各组标本C3、C4节段前屈、后伸、侧屈、旋转的运动范围(range of motion,ROM)。结果前屈运动:C组ROM明显小于其他3组,差异有统计学意义(P<0.05);B组ROM较A、D组明显增加,差异有统计学意义(P<0.05);A、D组间比较差异无统计学意义(P>0.05)。后伸、侧屈、旋转运动:C组ROM明显小于其他3组,差异有统计学意义(P<0.05);其他3组间比较差异无统计学意义(P>0.05)。结论新鲜成年山羊颈椎标本行生物衍生肌腱侧块经关节突交叉固定,能够限制颈椎过度前屈,完全保留后伸运动,不限制侧屈和旋转运动,重建屈曲分离型损伤下颈椎的动态稳定性。     

Traumatic instabilities of the cervical spine caused by high-speed axial compression in a human model. An in vitro biomechanical study

STUDY DESIGN: Traumatic injury of the cervical spine was produced on human cadavers and evaluated with instability tests and radiographs. OBJECTIVE: To relate traumatic injuries of the cervical spine to instability and patterns of traumatic injury to different levels of impact energy. SUMMARY OF BACKGROUND DATA: Data from young human cadavers are rare in traumatic models of the cervical spine, and instabilities caused by axial compression with different impacts remain unknown. METHODS: Fourteen cervical spine specimens (C2-C4) obtained from fresh human cadavers were divided evenly into two groups and subjected to axial compressive impact with 30 J and 50 J impact energy, respectively. Pure moments in flexion-extension, left/right lateral bending, and left/right axial rotation were applied to each specimen before and after trauma. The maximum moment was 2.0 Nm in each case. Ranges of motion and neutral zones were measured using stereophotogrammetry. RESULTS: Ranges of motion and neutral zones for both groups increased after trauma. No bony injury was observed on the radiographs after trauma with 30 J, but motions increased significantly in flexion, extension, and axial rotation. All specimens showed bony injuries after trauma with 50 J, whereas motions continued to increase significantly in all directions. The relative neutral zone values were larger than the corresponding range of motion values, except in flexion-extension after trauma with 50 J. CONCLUSIONS: The injury patterns of the cervical spine were associated with impact energy, and a high level of impact energy could produce either three-column injury or anterior middle-column injury. Instabilities of the cervical spine caused by compressive trauma increased with the level of impact energy. The neutral zone was more sensitive than the range of motion in representing spinal instability, whereas instability testing was more sensitive than radiographs in evaluating traumatic injury of cervical spine.     

The effect of locking fixation screws on the stability of anterior cervical plating

STUDY DESIGN: Current anterior cervical plate systems were tested with locked and unlocked fixation screws and with unicortical and bicortical fixation screws to determine fixation rigidity and pull-off strengths. OBJECTIVES: To evaluate the effects of screw-plate locking and screw length on fixation strength and stability of anterior cervical plates. SUMMARY OF BACKGROUND DATA: New plate systems provide for rigid locking of the screw-plate interface, theoretically increasing construct rigidity, allowing unicortical fixation, and preventing screw back-out. There are few data on the effects of locking screws on the stability of anterior cervical plating. METHODS: Eighty fresh lamb vertebrae (C3-T1) were used. Test systems included: Cervical Spine Locking Plate (CSLP; Synthes, Paoli, PA, Orion plate (Sofamor-Danek, Memphis, TN), and Acroplate (AcroMed, Cleveland, OH). The CSLP and Orion plates were tested with fixation screws, locked and unlocked, and the AcroMed plate with unicortical and bicortical screw purchase. Biomechanical testing of the screw-plate constructs was performed to determine the initial bone-plate rigidity and pull-off strength. A 2.5-Nm cyclic bending moment was then applied to additional constructs for 10(5) cycles, and these constructs retested. RESULTS: Locked CSLP and Orion constructs were more rigid than all unlocked unicortical systems initially and after cyclic loading (P < 0.05). After cycling, the rigidity of all unlocked unicortical constructs decreased significantly (P < 0.05). There was no significant difference in pull-off strengths between the CSLP, the Orion, and the unicortical AcroMed plate. However, all had significantly less pull-off strength than the AcroMed plate with bicortical screws. A negative correlation was observed between initial pull-off strength and sagittal vertebral body diameter. CONCLUSIONS: Locking screws significantly increased the rigidity of the tested screw-plate systems initially and after cyclic loading. Because pull-off strength was affected by the vertebral body diameter, use of longer unicortical screws may be clinically beneficial in the patient with larger cervical vertebrae.     

枕颈部后路不同内固定的生物力学比较

目的评价不同内固定重建枕颈部稳定性的生物力学性能。方法12具新鲜人体枕颈部标本,在标本完整、枕寰枢不稳、枕颈部植骨块钛缆固定(A组)、枕颈部经关节螺钉内固定(B组)、SUM-MIT枕颈部内固定系统固定(C组)五种状态下,依次用脊柱三维运动测量系统测试其OcC1、C1,2节段的运动参数。同时对固定后的OcC1经关节螺钉(OcC1TA组)、C1,2经关节螺钉(C1,2TA组)、枢椎椎弓螺钉(C2IS组)和枕骨螺钉(Oc Screw组)在生理载荷下三维六自由度运动时,运用电测法测定四种螺钉的拔出应力,并行统计学分析。结果在OcC1节段,B组在屈伸运动中的运动范围和中性区显著大于C组。在侧屈和旋转运动中,A组的运动范围和中性区均明显大于B、C组。在C1,2节段,B组各方向运动的运动范围和中性区均明显小于A组。B组在旋转运动中的运动范围和中性区均显著小于C组。电测法结果显示,侧屈状态下所有螺钉局部应变均接近0;前屈和旋转时螺钉承受不同程度的拉应力,后伸时螺钉承受压应力。Oc Screw组在屈伸和旋转运动状态下,所承受的任何载荷应力均大于其他三种置钉方法。结论枕颈部后路经关节螺钉内固定和SUMMIT枕颈内固定在控制旋转和侧屈的稳定性上有优点。枕骨螺钉承受的拉应力最大,生理环境下枕骨螺钉可能更易发生松动和断裂。