分类:脊柱外科 时间:2010年7月30日 20时05分 收藏: QQ书签 百度搜藏 收藏本文
The advent of rigid spinal instrumentation was accompanied by higher fusion rates in the treatment of degenerative lumbar disease without between the plating systems, thus questioning the compressive properties of the plate in vivo. Clinical outcomes were similar among the groups, which led the investigators to conclude that the more expensive dynamic plates do not offer any clear benefit compared with rigid plates. Anterior cervical plating is associated with adjacent-level ossification which may be due to impingement from the plate on the adjacent level disc space (Fig. 2).24,25 Although comparative series have shown no difference in incidence of this complication when comparing rigid with dynamic cervical plating, special attention must be paid to technique when using a dynamic clear improvements in clinical outcomes.29–31
坚强的脊柱内固定装置，面临的是在治疗退变性脊柱疾病过程中融合率提高，但是临床疗效并未得到明显改善的尴尬局面。通过邻近节段椎间盘内压力的测量，坚强内固定确实增加了邻近节段的应力。邻近节段应力增加在导致邻近节段退变机器退变性疾病中的作用仍未确定。邻近节段退变性疾病的发生率高达36 %。对于邻近节段退变和退变性疾病的关注，驱使动态或者半坚强固定得到了发展。随着颈椎内固定器械的发展，腰椎动态装置被设计成一个载荷分享装置,该装置不会增加邻近节段的应力，也能促进融合。有部分动态装置也被用于非融合。前期临床证据尚不能支持低强度的固定可提高脊柱融合率。在美国,美国食品药品监督治疗局（FDA）批准腰椎动态固定装置通过了510（k）文件。自1976年开始，一个新的器械，必须是与现在美国市场上一种或多种相似器械对比而言是等价器械(substantially equivalent)。美国510k文件还强调，必须提交与1976年之前合法上市的器械具有等价的临床疗效，来说明器械是等效器械（predicate device）。用于非融合的动态固定装置已被广泛应用。因此,对于腰椎动态固定用于非融合的文献仅局限于一些前瞻性研究。所以，本节回顾分析动态装置用于融合的临床证据及讨论动态固定系统用于融合技术。为更广泛的回顾最新数据,读者可以参考Bono及其同事们公开发表的最新文献。
Rigid instrumentation does result in increased forces at the adjacent segments of the spine as measured by intradiscal pressure. The role of increased forces at the adjacent segments in causing adjacent segment degeneration and disease remains undetermined. The rates of adjacent segment disease are as high as 36%.32 The concern for adjacent segment degeneration and disease has driven the development of dynamic, or semirigid, constructs for lumbar spine instrumentation. As with cervical spine instrumentation, the dynamic instrumentation for the lumbar spine is designed to be a load-sharing device, allowing for fusion without excessive rigidity leading to adjacent segment complications.33 Some dynamic constructs have also been used without fusion. Preclinical evidence to support less rigid stabilization as a mechanism for improving fusion rates in the spine is limited. In the United States, the FDA has approved lumbar dynamic stabilization devices through the 510k regulatory pathway. A new technology that is substantially equivalent to existing devices that have been in use since before 1976 may be approved by the FDA under the process of 510 approval. The US FDA 510 regulatory process specifically applies to devices and technologies for which there was a predicate device in existence before 1976. The level of clinical evidence required for 510k approval is variable and approval may be based on mechanical and preclinical studies alone. Dynamic stabilization devices without fusion have been applied in a physicianThis directed use, or off-label application. Therefore, the literature on lumbar dynamic stabilization without fusion is limited to a few prospective studies. This section reviews the evidence for these devices as instruments for spinal fusion, and discusses the use of fusion devices for dynamic stabilization. For a broader review of the recent data, the reader is referred to the recent publication by Bono and colleagues.34
被FDA按照510k文件批准用于脊柱融合这个动态系统，是基于椎弓根螺钉系统共建的一种半坚强固定、或者限制轴向压缩或限制屈伸活动的装置。这些动态装置的强度受材料的选择及其纵向连接棒来决定。尽管坚强的不锈钢、钛合金常用语脊柱内固定系统，但是半坚强固定却是选用polyetheretherketone ( PEEK ) 作为连接杆材料，或者选用镍钛诺（Nitinol）记忆合金、特殊的剪切棒(例如,ACCUflex)、带关节的棒、聚乙烯索(oynesys)等等。半坚强固定系统的优化力学特性尚未确定。
PEEK is a polymer that has been studied in spinal fusion. The material properties of PEEK make it popular for several reasons. It is a biocompatible polymer, with excellent strength, virtually no reactivity, and it is radiolucent (Fig. 3).38 Ponnappan and colleagues33 compared the biomechanical properties of 5.5-mm PEEK rods with those of 5.5-mm titanium rods for single-level posterolateral fusion (PLF), and when paired with posterior lumbar interbody fusion (PLIF). They found no significant difference in stiffness between the PLF constructs in flexion/extension, lateral bending, or axial rotation. The PLIF constructs were significantly stiffer than the PLF constructs in all 3 planes. Again, there were no differences between the titanium and PEEK constructs with PLIF. The PEEK constructs with interbody graft did show increased load sharing with the interbody graft compared with the titanium posterior instrumentation. A PEEK posterior rod with an interbody graft may improve load sharing with interbody fusions, thereby encouraging compression of the interbody graft. The PEEK constructs also showed reduced stress at the pedicle screw to bone interface, which may reduce the risk of pedicle screw loosening. The ability to visualize the fusion mass is also a noted advantage of PEEK rods. There are no published clinical data that support improved outcome regarding fusion rates or screw loosening.
Nitinol is a nickel and titanium memory alloy. The flexibility and rigidity of the alloy vary with the temperature of the surrounding environment. These material properties allow the alloy to be contoured at room temperatures, and to return to a precontoured position at body temperature.The Bio-Flex System (Bio-Spine; Korea) consists of titanium pedicle screws and coiled 4-mm Nitinol rods. Kim and colleagues36 described the use of this system in a heterogeneous cohort of patients and treatment modalities for degenerative disease of the lumbar spine. Used in combination with PLIF, the fusion rate achieved was 90%, and the overall success rate was 90.7%. The investigators reported that adjacent segment motion was increased at levels adjacent to the Bio-Flex system alone and at combined Bio-Flex/PLIF levels, and concluded that the Bio-Flex system allows for more physiologic movement at the adjacent segments. The effect of increased motion at segments adjacent to instrumented levels on degeneration will require long-term follow-up. Further evaluation of nitinol semirigid fixation will require matched comparison with rigid fixation systems.
The AccuFlex System (Globus Medical Inc; Audubon, PA, USA) is a semirigid rod designed for use with a standard pedicle screw instrumentation system. Through a proprietary technique, helical cuts is fixed, the rod is not amenable to contouring. The results for a randomized controlled trial of single-level posterior spinal fusion (PSF) with interbody fusion with standard 6.5-mm rods versus AccuFlex rods were reported by Mandigo and colleagues.35 At 1 year of follow-up, results with respect to Short Form 36 (SF-36) scores, VAS scores, and fusion rates did not differ between the 2 groups. The investigators were careful to note that more follow-up is needed to determine whether rates of adjacent segment disease are different between the groups.
The Twinflex system (Eurosurgical; Beaurains, France) is a flexible system, based on 2.5-mm stainless steel rods, and pedicle screw fixation. The smaller diameter rods allow for less rigid fixation, again with the hypothesis that load sharing will allow for high fusion rates with less adjacent segment disease. A well-designed study by Korovessis and colleagues39 compared this system with rigid and semirigid pedicle screw systems. With 15 patients per group and an average of 4 years follow-up, no differences in clinical results were observed. Three patients in the dynamic Twinflex group sustained broken implants, but fusion rates were similar within all 3 groups. Adjacent segment disease was not observed in any of the groups. These investigators concluded that, as the results were similar among all groups, no clear recommendations may be made. In this case, further follow-up and cost analyses may help clarify the usefulness of these different instrumentation systems.
The Dynesys (Centerpulse/Zimmer, Winterthur, Switzerland) system is marketed as a fusion device, despite a lack of peer-reviewed reports available to assess its utility for this purpose. Dynamic stabilization of the spine without fusion remains a controversial strategy in the management of spinal disorders. The Dynesys dynamic stabilization system is a pedicle screw–based construct, with polyethylene terephthalate cords and polyurethane sleeves bridging the pedicle screws. The cord acts to stabilize the motion segment in flexion, whereas the sleeve acts to stabilize in extension, and this effect has been shown in cadaveric studies.40,41 As with other cuts are made in a 6.5-mm rod, making the rod less rigid. This system is limited to single-level use, and because the orientation of the helical patients underwent additional surgery for persistent pain or adjacent segment disease. Despite these high complication rates (30%), the trial investigators concluded that the implant was a success for management of degenerative lumbar disease. Statistically significant changes were observed in VAS and Oswestry Disability Index (ODI) scores. Comparison with a matched cohort treated with rigid stabilization will be useful in an assessment of the Dynesys system for treatment of degenerative lumbar pathology without fusion.
Dynesys instrumentation has been reported with variable outcomes in recent publications. Beastall and colleagues43 used positional magnetic resonance imaging (MRI) to compare instrumented segment and adjacent segment motion following rigid instrumentation and Dynesys instrumentation. The investigators confirmed the motionsparing and stabilizing properties of Dynesys compared with rigid instrumentation, as the dynamic stabilization group had a greater, although still restricted, range of motion (ROM) at the instrumented level. Their results, however, were opposite to the in vitro results of Schmoelz and colleagues,41 as extension was limited, rather than flexion. With only 9 months follow-up, Beastall and colleagues43 did confirm that adjacent segment motion was unchanged following Dynesys instrumentation. However, this same group found MRI evidence of progressive degenerative disease at Dynesys instrumented levels and at adjacent levels. Whether this is a result of the natural history of degenerative disease, as suggested by Hilibrand and colleagues6 in the cervical spine, or a result of the intervention is unknown and will require further follow-up. In a separate investigation comparing adjacent segment ROM after Dynesys and rigid instrumentation, Cakir and colleagues44 found no difference in ROM from the preoperative and postoperative periods. They conclude that Dynesys shows no beneficial effect on the adjacent segment.
DynesyS系统的临床疗效在最近刊物上被报道。Beastall和同事使用体位磁共振(postional MRI)比较了坚强内固定与Dynesys系统固定后的病变节段与邻近节段的运动。研究者证实：相对坚强固定而言，Dynesys系统的有限运动和动态特性更具有优势；因为动态固定组的内固定节段运动范围(ROM)更大，虽然其运动是被限制的。然而，他们的结果与Schmoelz及其同事的离体结果相反：后伸幅度有限而不是屈曲。Beastall 及其同事的一个只有9个月的随访，证明了在运用了Dynesys系统后邻近节段的运动不受影响。但是同组仍发现这Dynesys固定节段及其邻近节段退变的MRI证据。无论这是退变性疾病的的自然病史--Hilibrand和同事对颈椎的猜想，还是干预之后的结果仍然不得而知，这需要进一步的随访研究。在一个独立的的调查中，比较了Dynesys系统和坚强内固定系统邻近节段运动范围（ROM），Cakir和同事发现术前和术后无显著性差异。因此，他们认为:对于邻近节段，Dynesys显示不出任何有益的影响。
Patient-based outcome measures are an important tool for assessing device efficacy, and represent the most important measure of implant performance. Grob and colleagues45 presented results in their report of 2 years follow-up of a heterogeneous group of lumbar degenerative disease patients who underwent dynamic stabilization. Their results show that only 50% of patients reported that the procedure helped or helped a lot. When comparing their results with historical controls treated with fusion procedures for similar indications, these results were inferior. They note that 19% of the patients studied required reoperation within the short follow-up period. They conclude that there is no evidence to support that dynamic stabilization is superior to fusion regarding clinical outcome or need for revision surgery at the same or an adjacent level. Clinical results were also reported by Bothmann and colleagues46 in a review of 40 patients with an average of 16 months follow-up. Subjective improvements in pain and quality of life were re ported in 73% of the patients studied. These clin ical improvements were similar to results from traditional fusion surgery. The investigators conclude that dynamic stabilization alone is not a successful procedure, and stabilization should be accompanied by decompression of the neural elements. An alarming reoperation rate of 27.5% was reported, with 17.5% of patients suffering from loosening of the pedicle screws. Implant loosening and high reoperation rates are important limitations in the published efficacy of dynamic stabilization systems without fusion.
基于患者的疗效评价，是一项评价装置的功效的重要工具，代表植入器械的最重要评价指标。Grob及其同事报告了接受动态固定的腰椎退变性疾病患者的2年随访结果。结果显示：50 %的患者认为此项手术帮助或者很大程度上帮助了他们。当将他们的结果与历史文献中的相似手术适应证患者却采用融合术相比，Grob的结果都低。他们注意到19%的患者在短期随访中即需要再次手术。他们认为：在临床结果和同一或邻近节段需要进行翻修手术等方面，目前还没有证据支持动态固定优于坚强固定。Bothmann及其同事回顾了平均随访6个月的一组40例患者。73 %病人的主观疼痛和生活质量的得到改善。这些临床症状的改善与传统融合手术的临床疗效相似的。因此，研究者认为：单独运用动态固定并不是成功的手术方式，必须同时行神经减压（decompression of the neural e lements）。27.5%的手术率是令人震惊，同时17.5%的病人出现了椎弓根螺钉松动。内植物松动和很高的再手术率，是文献报道中单纯动态固定而不行融合患者的严重不足。
Semirigid instrumentation of the spine may be applied with the intent to fuse the spine, or to stabilize the affected motion segment without fusion. The optimal rigidity of a posterior instru mentation system for fusion remains undetermined. Preclinical data support semirigid fixation improving the load on the interbody graft. There is little evidence that semirigid fixation may improve PLF rates (Table 2). Long-term followup of the effect of semirigid fixation on adjacent segment pathology will permit an evaluation of the technology as a strategy for preventing adjacent segment degeneration.
[ 本帖最后由 步步高 于 2010-12-4 11:47 编辑 ]