Biomechanical comparison of posterior cervical fixation

STUDY DESIGN: Biomechanical stability using four different posterior cervical fixation techniques was evaluated in human cadaveric spine. OBJECTIVES: To introduce an alternative interspinous fixation technique using wavy-shaped rods, and to compare its in vitro biomechanical stability with that of other posterior cervical fixation techniques. SUMMARY OF BACKGROUND DATA: Fixation of the posterior cervical spine with interspinous wiring is well known as Rogers' or Bohlman's technique. Recently, several plate fixation techniques have been used for posterior cervical stabilization. Since 1983, the authors have developed the wavy-shaped rod system as an alternative to the interspinous fixation technique. This unique technique has been proven clinically useful in Japan. However, the authors are not aware of any prior biomechanical studies. METHODS: Seven fresh frozen cervical human spines were tested at the C5-C6 motion segment. Nondestructive static biomechanical testing was performed with flexion-extension, lateral bending, and axial rotation for the following stabilization techniques: intact spine, creation of a Stage 3 distractive-flexion injury followed by fixation with the wavy-shaped rods bounded by three multistrand cables, interspinous wiring with a multistrand cable, triple wiring technique using multistrand cables with a pair of unicortical grafts from the ilium, and lateral mass plate fixation with Magerl's screw technique. Testing was performed on a material testing machine (MTS 858 Bionix test system, MTS, Minneapolis, MN), and load displacement curves were obtained using four linear extensometers and one rotatory extensometer across the C5-C6 motion segment. RESULTS: In axial compression loading, the reconstructed specimens showed significant differences in range of motion measured at the anterior and posterior positions, and statistical analysis was performed using one-way analysis of variance. In a comparison of the four fixation techniques, the construct with the wavy-shaped rod indicated significantly less motion both anteriorly and posteriorly than with the other fixation techniques. Also in flexion-extension loading, all the techniques significantly limited the intervertebral motion below the level of the intact motion segment. Particularly, the construct with the wavy-shaped rod showed the smallest mobility, 49.9% anteriorly and 9.3% posteriorly, compared with that of the intact spine. In lateral bending, the lateral mass plate provided the greatest stability, which was superior to the intact segment, but the difference was not statistically significant. In axial rotation, all the reconstruction techniques limited the angular motion below the intact level (wavy rod, 68.0%; Rogers' wiring, 75.2%; Bohlman's triple wiring, 59.8%; lateral mass plate, 71.7%), but no significant differences were observed using one-way analysis of variance, as compared with the intact segment. CONCLUSIONS: All four reconstruction techniques restored the stability of the cervical motion segment to at least the level of the intact motion segment before destabilization. An alternative cervical posterior fixation technique, the Wavy Rod system, was considered the most effective technique in stabilizing a cervical motion segment, particularly in axial compression and flexion extension loading.     

Trans-sacral fixation for failed posterior fixation of the pelvic ring

Introduction: In the treatment of certain pelvic ring pathologies (non-unions and failure of ilio-sacral screw fixation) trans-sacral fixation (i.e. fixation from iliac wing to the other traversing the body of S1) may be necessary. The purpose of our study was to describe our early experience and describe the surgical technique. Materials and methods: Seven cases of trans-sacral fixation were identified with a mean patient age of 49-years-old with four females and three males. The diagnosis at the time of trans-sacral fixation was failure of posterior ring fixation in four (three of which had vertical sacral fractures), mal-position of iliosacral (IS) screw in one, failure of fusion of sacroiliac (SI) joint in two. All these cases were augmented with a 4.5 mm reconstruction plate placed in tension posteriorly. Results: At average follow up of 39 months (range 24–75), all patients achieved union. There were no neurological or vascular complications. Two patients required reoperations prior to union. Our current use for this technique is with a 8.0 mm screw (16 mm thread). Conclusions: Initial experience with trans-sacral fixation has proven to be very effective technique to solve the most difficult problems in posterior pelvic ring fixation. We reserve its use to the following indications: nonunion/malunion of the pelvic ring, and sacral fractures.     

骨盆后环损伤的内固定治疗

目的 探讨手术内固定治疗骨盆后环损伤的临床疗效.方法 对22例骨盆后环损伤患者分别采用微创技术椎弓根螺钉固定、骶髂关节空心螺钉固定及骨盆重建带后方髂髂固定3种方式治疗.结果 22例均随访,时间4~22个月.无切口感染、血管神经损伤及内固定松动或断裂,无骨折不愈合.结论 微创椎弓根螺钉固定、骶髂关节空心螺钉固定及骨盆重建带后方髂髂固定3种方式均为治疗骨盆后环损伤的有效方法,根据骨折类型及患者的情况选择不同的内固定方式,可获满意疗效.     

寰枢关节后路内固定稳定性的生物力学比较研究

目的比较寰枢椎后路手术中常用的Gallie、Brooks、Magerl双螺钉、Maged单螺钉等内固定方法单独应用或联合应用时的力学稳定性,为临床选择治疗术式提供实验依据.方法取5具新鲜冷冻人体颈椎(C1～C5)标本,固定C1和C2~C5,仅保留C1～C2之间活动.切断寰椎横韧带和齿状突,造成寰枢关节不稳定.每个标本依次行Maged单螺钉、Maged双螺钉、Gallie、Maged单螺钉 Gallie、Maged双螺钉 Gallie、Brooks固定.在生物力学试验机上应用位移控制法测定各组的稳定性,前屈和侧屈的位移定为lmm,旋转角度为30°测定正常组、损伤组及内固定各组在前屈、双侧侧屈和旋转状态下的刚度,比较内固定各组的稳定性.结果在各组内固定中,Maged双侧侧块螺钉 GaUie刚度最大,最稳定.Magerl单螺钉 Gallie和Maged双螺钉相比.在各种状态下.二者刚度均无显著性差异(P＞0.05),在旋转状态下,其刚度值分别为1.55 0.07Nm/3°和1.44 0.13Nm/3°(P＞0.05);而Maged单螺钉的刚度在各种状态下均明显低于Magerl双螺钉(P＜0.05),其中在旋转状态下分别为0.96±0.17Nm/3°和1.44±0.13Nrn/3°(P＜0.05).结论Maged单螺钉 Gallie钢丝固定稳定性好,可替代Magerl双螺钉,而Maged单螺钉固定效果不佳,应尽量避免单独使用.     

Biomechanical comparison of five different atlantoaxial posterior fixation techniques

STUDY DESIGN: Five different reconstructions of the atlantoaxial complex were biomechanically compared in vitro in a nondestructive test. OBJECTIVES: To determine whether non-bone graft-dependent one-point fixation affords stability levels equivalent to three-point reconstructions. SUMMARY OF BACKGROUND DATA: Previous investigations have demonstrated that three-point fixation, using bilateral transarticular screws in combination with posterior wiring, provide the most effective resistance to minimize motion around C1-C2. However, placement of transarticular screws is technically demanding. Posterior wiring techniques affording one-point fixation have failure rates of approximately 15%, with failure considered to be secondary to structural bone graft failures. One-point, non-bone graft-dependent fixations have not been tested. METHODS: Eight human cervical specimens, C0-C3 were loaded nondestructively. Unconstrained three-dimensional segmental motion was measured. The reconstructions tested were two one-point fixations, one two-point fixation, and two three-point fixations. RESULTS: Under axial rotation two and three-point reconstructions provided better stiffness than the one-point reconstructions (P < 0.05). During flexion-extension, higher stiffness levels were observed in one- and three-point fixations when compared with the intact spine (P < 0.05). In lateral bending no significant differences were observed among the six groups, although the trend was that reconstructions including transarticular screws provided greater stability than one-point fixations. CONCLUSION: The current findings substantiate the use of three-point fixation as the treatment of choice for C1-C2 instability. [l: atlantoaxial fixation, biomechanics, cervical spine, instability, spinal instrumentation, transarticular screws]     

三种内固定物固定骨盆后环损伤稳定性的生物力学比较

 目的 比较张力带接骨板、2枚骶髂螺钉和可调式微创骨盆后环接骨板治疗骨盆后环纵 行骨折的固定效果。方法选择 8具成年男性非骨质疏松性骨盆标本, 保留骶髂复合体, 剔除其余软组 织, 制作右侧骶骨纵行骨折模型;±次应用张力带接骨板、2枚骶髂螺钉、可调式微创骨盆后环接骨板行 规范化固定。将标本以坐位固定于生物力学试验机, 首先以 20 N/s的速度对标本施加 0~620N的垂直 负荷, 记录标本移位程度;然后以 0.1°/s的角速度加载扭转负荷, 记录扭转角度及对应的扭矩。采用方差 分析比较不同内固定物的固定效果。结果 在垂直负荷作用下, 可调式微创骨盆后环接骨板固定骨盆 的移位与 2枚骶髂螺钉固定骨盆的移位无明显差别, 两者移位均小于张力带接骨板固定骨盆的移位。 在扭转负荷下, 可调式微创骨盆后环接骨板固定骨盆的扭矩与 2枚骶髂螺钉固定骨盆的扭矩无明显差 别, 两者均大于张力带接骨板固定骨盆的扭矩。结论 在垂直负荷和扭转负荷作用下, 可调式微创骨盆 后环接骨板固定骨盆的稳定性与 2枚骶髂螺钉固定效果相同, 两者均优于张力带接骨板。     

Computed tomography-guided fixation of unstable posterior pelvic ring disruptions.

Open reduction and internal fixation (ORIF), the current treatment of choice of posterior pelvic ring disruptions with instability, has significant disadvantages. These include relatively "blind" placement of the fixation screws, infection, exsanguinating hemorrhage, and high wound complication rates. We feel fluoroscopy does not offer significant clarity in defining the posterior structure. Advantages of computed tomography (CT)-guided sacral fixation are direct visualization of the course of the screws and absence of significant wound complications. This technique provides superior visualization of the nerve roots and sacral canal compared to fluoroscopic methods. Thirteen patients (10 unilateral and 3 bilateral) with unstable but reducible sacral fractures or sacroiliac joint (SIJ) disruptions underwent CT-guided posterior pelvic ring fixation using a cannulated screw system. Skeletal traction was required intraoperatively in one case by a traction-counteraction pulley system in the CT scanner. All other reductions were performed by preoperative skeletal traction or manually by the surgeons after anesthesia in the scanner or after push-pull films demonstrated instability. The guide pin, using depth and angulation measurements derived from the scout CT scans, was positioned across the fracture or SIJ. Following CT confirmation of the position of the pin, the screw tract was drilled and the cannulated screw was placed into position. Radiographic and clinical follow-up observation (7-24 months) showed healing with no significant complications in all 13 patients. Computed tomography-guided sacral fixation is a safe alternative to ORIF in selected patients with reducible unstable pelvic fractures.     

Biomechanical comparison of plate and screw fixation in anterior pelvic ring fractures with low bone mineral density

IntroductionOsteosynthesis of anterior pubic ramus fractures can be challenging, especially in poor bone quality. The aim of the present study was to compare plate and retrograde endomedullary screw fixation of the superior pubic ramus with low bone mineral density (BMD).Materials and methodsTwelve human cadaveric hemi-pelvises were analyzed in a matched pair study design. BMD of the specimens was 35 ± 30 mgHA/cm³, as measured in the fifth lumbar vertebra. A simulated two-fragment superior pubic ramus fracture model was fixed with either a 7.3-mm cannulated retrograde screw (Group 1) or a 10-hole 3.5-mm reconstruction plate (Group 2). Cyclic progressively increasing axial loading was applied through the acetabulum. Relative interfragmentary movements were captured using an optical motion tracking system.ResultsInitial axial construct stiffness was 424 ± 116.1 N/mm in Group 1 and 464 ± 69.7 N/mm in Group 2, with no significant difference (p = 0.345). Displacement and gap angle at the fracture site during cyclic loading were significantly higher in Group 1 compared to Group 2. Cycles to failure, based on clinically relevant criteria, were significantly lower in Group 1 (3469 ± 1837) compared to Group 2 (10,226 ± 3295) (p = 0.028). Failure mode in Group 1 was characterized by screw cutting through the cancellous bone. In Group 2 the specimens exclusively failed by plate bending.ConclusionsFrom biomechanical point of view, pubic ramus stabilization with plate osteosynthesis is superior compared to a single retrograde screw fixation in osteoporotic bone. However, the extensive surgical approach needed for plating must be considered.     

经皮微创桥接组合式内固定系统治疗骨盆后环损伤

[目的]介绍桥接组合式内固定系统治疗骨盆后环损伤的手术技术。[方法] 2015年1月～2018年6月,对19例骨盆后环损伤的患者行经皮微创桥接组合式内固治疗,其中12例还行前环有限切开内固定。先取俯卧位或者漂浮体位的前倾体位固定骨盆后环,然后再改为仰卧位后漂浮体位的后仰体位复位固定骨盆前环。于两侧髂后上棘外侧做斜形3～5 cm切口,显露骨折脱位处,牵拉、撬拨、挤压等方法予以骨折复位,再将塑形后的连接棒经皮下隧道穿过,安装连接块,调整至最佳位置,钻孔并拧紧螺钉,穿透双侧骨皮质,利用桥接系统的撑开加压功能辅助进一步复位,至满意后锁定固定系统。[结果] 19例患者均顺利手术,无血管、神经损伤等严重并发症。术后随访时间12～39个月。根据Majeed功能评分,优12例,良5例,可2例,优良率89.47%。影像评估方面,复位质量根据Matta评分标准:优18例,良1例,可0例,优良率为94.74%。[结论]经皮微创桥接组合式内固定系统治疗骨盆后环损伤,操作简单灵活,固定可靠,并发症少。     

Biomechanical comparison of sacroiliac screw techniques for unstable pelvic ring fractures

OBJECTIVE: To determine the stiffness and strength of various sacroiliac screw fixations to compare different sacroiliac screw techniques. DESIGN: Randomized comparative study on embalmed human pelvises. MATERIALS AND METHODS: In 12 specimens, we created a symphysiolysis and sacral fractures on both sides. Each of these 24 sacral fractures was fixed with 1 of the following methods: 1 sacroiliac screw in the vertebral body of S1, 2 screws convergingly in S1, or 1 screw in S1 and 1 in S2. On the left and right side of a pelvis, different techniques were used. The pubic symphysis was not stabilized. We measured the translation and rotation stiffness of the fixations and the load to failure using a 3-dimensional video system. RESULTS: The stiffness of the intact posterior pelvic ring was superior to any screw technique. Significant differences were found for the load to failure and rotation stiffness between the techniques with 2 screws and a single screw in S1. The techniques utilizing 2 screws showed no differences. CONCLUSIONS: Based on the results of this study, we can conclude that a second sacroiliac screw in completely unstable pelvic fractures increases rotation stiffness and improves the load to failure.     

胸腰椎爆裂骨折三种后路内固定方法的稳定性生物力学研究

[目的]比较长节段固定术、短节段固定术和短节段结合椎体成形固定术治疗胸腰椎爆裂骨折的稳定性。[方法]收集6具新鲜尸体的脊柱(T9～L5)标本,对每一具标本依次按完整状态、骨折状态、长节段固定、短节段固定和短节段结合椎体成形的顺序进行测试,计算其在屈曲、背伸、左右侧弯和左右旋转6个方向的运动范围,比较各组间差异。[结果]骨折后脊柱在6个方向上的运动范围均增加(P<0.05);各内固定组的运动范围均小于完整组(P<0.05);长节段固定和短节段结合椎体成形固定的运动范围小于单纯短节段固定组(P<0.05);短节段结合椎体成形固定在屈曲和左右侧屈方向上的运动范围与长节段固定无差别(P>0.05),而在背伸和左右旋转方向上的运动范围短节段结合椎体成形固定则大于长节段固定(P<0.05)。[结论]通过延长固定节段与联合椎体成形均能够增加短节段固定的稳定性,在屈曲和左右侧屈方向上短节段联合椎体成形已经能够达到长节段固定所能够达到的稳定性。     

后路重建钢板治疗骨盆后环损伤的应用解剖学研究

目的对重建钢板内固定在骨盆后环骨折治疗中的钢板有效固定区、置钉角度及深度进行测量,为临床手术提供解剖学基础。方法解剖21具成人骨盆标本,测量钢板有效固定区、耳状面距、腰骶干内缘距、腰骶干外缘距、骶椎间孔距、偏离角度。结果钢板有效固定区为（54.29±4.63）mm,近髂后上棘第1枚螺钉的耳状面距为（28.30±4.15）mm,腰骶干内缘距为（52.58±3.55）mm,骶椎间孔距（46.89±4.29）mm,第1枚螺钉偏离角度为〉（13.80°±8.78°）,〈（30.19°±11.15°）,近髂后上棘第2枚螺钉的耳状面距为（24.02±2.72）mm,近髂后上棘第3枚螺钉的耳状面距为（18.79±2.45）mm,近髂后上棘第4枚螺钉的耳状面距为（18.9±3.15）mm,腰骶干外缘距为（33.35±3.47）mm,第4枚螺钉偏离角度内偏9.24°±3.9°,外偏6.85°±3.1°。结论该研究对重建钢板内固定治疗骨盆后环骨折提供了应用解剖学基础,在每侧髂骨翼置入4枚螺钉是可行的。     

经皮重建钢板内固定治疗不稳定骨盆后环骨折

目的:探讨应用经皮重建钢板内固定治疗不稳定骨盆后环骨折的方法和临床疗效。方法:2004年3月至2008年10月治疗不稳定骨盆后环骨折36例。男26例,女10例;年龄10～65岁,平均37.3岁。牵引复位后,于双侧髂后上棘外侧顺髂嵴做弧形切口,长3～5cm,在患侧将重建钢板通过皮下隧道到对侧,经皮重建钢板内固定治疗。结果:36例均获得随访,时间12～36个月,平均17.8个月。无切口感染,无术中血管神经损伤,无内固定松动及断裂,无骨不愈合,无明显双下肢不等长。平均切口长度、手术时间、术中出血量分别为(4.36±0.99)cm、(42.61±7.97)min、(168.61±40.44)ml。术后功能恢复根据Majeed评价,优12例,良18例,可6例。结论:经皮重建钢板内固定治疗不稳定骨盆后环骨折操作简单、安全、创伤小、恢复快、并发症少,是治疗不稳定骨盆后环骨折的一种比较理想的手术方法。     

改良张力带钢板重建骨盆后环的生物力学研究

[目的]通过生物力学研究验证一种新的改良张力带钢板重建不稳定性骨盆后环损伤的效果,并与其他两种方法比较。[方法] 8具成人骨盆标本,制成不稳定性骨盆环损伤(AO分类C1.2)模型,随机依次应用三种不同内固定来重建骨盆后环:传统张力带钢板;改良张力带钢板;双骶髂螺钉。分别依次予以0～600 N垂直和0～8 N·m扭转加载,测量整体骨盆环垂直位移和扭转角度并计算轴向和扭转刚度;测量损伤侧骶髂关节在垂直、左右和前后方向上的位移以及在矢状面上的旋转角度。[结果]在垂直和扭转载荷下,改良张力带钢板固定后的整体骨盆环垂直位移和扭转角度均明显小于传统张力带钢板(P0.05),虽大于双骶髂螺钉,但差异无统计学意义(P0.05);改良张力带钢板固定后的整体骨盆环轴向刚度和扭转刚度均明显大于传统张力带钢板(P0.05),虽小于双骶髂螺钉,但差异无统计学意义(P0.05)。垂直载荷下,改良张力带钢板伤侧骶髂关节在垂直、左右、前后方向上位移以及在矢状面上的旋转位移明显小于传统张力带钢板(P0.05)。[结论]与传统张力带钢板相比,改良张力带钢板重建骨盆后环提供了更好的生物力学稳定性。     

Combined anterior and posterior ring fixation versus posterior ring fixation alone in the management of unstable Tile B and C pelvic ring injuries: A randomized controlled trial

PurposeCombined anterior and posterior ring (APR) fixation is classically performed in Tile B2 and C1 injuries to achieve superior biomechanical stability. However, the posterior ring (PR) is the main weight bearing portion that is responsible for weight transmission from the upper parts of the body to the lower limbs through the sacrum and the linea terminalis. It is hypothesized that isolated PR fixation can achieve comparable radiological and clinical outcomes to APR fixation. Therefore, we conducted this study to compare the two fixation principles in managing Tile B2 and C1 injuries.MethodsOur study included 20 patients with Tile B2 injuries and 20 patients with Tile C1 injuries. This study was a randomized control single-blinded study via computerized random numbers with a 1:1 allocation by using random block method. The study was performed at a level one trauma center. A total of 40 patients with Tile B2 and C1 injuries underwent combined APR or isolated PR fixation (Group A and B, respectively). Matta & Tornetta radiological principles and Majeed pelvic scoring system were used for the assessment of primary outcomes and postoperative complications. Secondary outcomes included operative time, amount of blood loss, intraoperative assessment of reduction, need of another operation, length of hospital stay, ability to weight bear postoperatively and pain control metrics. We used student t-test to compare the difference in means between two groups, and Chi-square test to compare proportions between two qualitative parameters. We set the confidence interval to 95% and the margin of error accepted to 5%. So, p ≤ 0.05 was considered statistically significant.ResultsThe mean follow-up duration was 18 months. The operative time (mean difference 0.575 h) and the intraoperative blood loss (mean difference 97.5 mL) were lower in Group B. Also, despite the higher frequency of rami displacement before union in the same group, there were no significant differences in terms of radiological outcome (excellent outcome with OR = 2.357), clinical outcome (excellent outcome with OR = 2.852) and postoperative complications assessment (OR = 1.556) at last follow-up.ConclusionThe authors concluded that isolated PR fixation could favorably manage Tile B2 and C1 pelvic ring injuries with Nakatani zone II pubic rami fractures and intact inguinal ligament. Its final radiological and clinical outcomes and postoperative complications were comparable to combined APR fixation, but with less morbidity (shorter operation time, lower amount of blood, and no records of postoperative wound infection).     

Percutaneous fixation of pelvic ring disruptions

Percutaneous pelvic fixation is possible because intraoperative fluoroscopic imaging and other technologies have been refined. Anterior and posterior unstable pelvic ring disruptions are amenable to percutaneous fixation after closed manipulation or open reduction. Stable and safe fixation is achieved only after an accurate reduction. Anterior pelvic external fixation remains the most common form of percutaneous pelvic fixation; however, percutaneously inserted medullary pubic ramus, transiliac, and iliosacral screws stabilize pelvic disruptions directly while diminishing operative blood loss and operative time. These percutaneous techniques do not decompress the pelvic hematoma allowing early definitive fixation without the risk of additional hemorrhage. Complications associated with open posterior pelvic surgical procedures are similarly avoided by using percutaneous techniques. A thorough knowledge of pelvic osseous anatomy, injury patterns, deformities, and their fluoroscopic correlations are mandatory for percutaneous pelvic fixation to be effective.     

The fixation of pelvic ring fractures

Summary Because of the increase in fast traffic and dangerous new sports, in the last few years there has been a dramatic increase in the number of severe pelvic injuries. In 1988, we treated 125 patients with such pelvic injuries. We use Tile's classification method to stage injuries of the pelvic ring type A, type B (B1, B2, B3) and type C. More than 60% of our patients had multiple injuries. In this paper we discuss making the diagnosis, operative procedures, and treatment management.     

经皮闭合内固定治疗骨盆环损伤

目的对骨盆环损伤闭合内固定术的临床疗效进行评价。方法回顾性分析58例骨盆环损伤患者的临床资料。其中女24例,男34例,年龄18—62岁,平均年龄36岁。全部患者均采用骶髂关节螺钉、耻骨螺钉、耻骨联合螺钉及髂骨后部螺钉等多种形式的闭合内固定。结果58例中满意复位者52例,6例复位不满意;57例骨折愈合,1例骨不连接;56例无血管神经损伤,2例有S1神经损伤,遗留下肢及马鞍麻木。结论经皮闭合固定骨盆环损伤小、出血少、固定效果较好,是一种有前景的手术方式,但对操作者要求高。术前大重量骨牵引有利于术中复位。