Failure of a polyether-ether-ketone expandable interbody cage following transforaminal lumbar interbody fusion

Purpose

Expandable cages are a more recent option for maintaining or restoring disc height and segmental lordosis with transforaminal lumbar interbody fusion (TLIF). Complications associated with expandable cages have not yet been widely reported. We report a case of postoperative failure of a polyether-ether-ketone (PEEK) expandable interbody device used during TLIF.

Methods

A 50-year-old man presented with severe back and right leg pain after undergoing L4-5 and L5-S1 TLIFs with expandable cages and L3-S1 posterior instrumented fusion. Imaging showed retropulsion of a portion of the interbody cage into the spinal canal causing nerve compression. Displacement occurred in a delayed manner. In addition, pseudoarthrosis was present.

Results

The patient underwent re-exploration with removal of the retropulsed wafer and redo fusion.

Conclusions

Expandable cages are a recent innovation; as such, efficacy and complication data are limited. As with any new device, there exists potential for mechanical failure, as occurred in the case presented.

     

Failure of a polyether-ether-ketone expandable interbody cage following transforaminal lumbar interbody fusion

Purpose

Expandable cages are a more recent option for maintaining or restoring disc height and segmental lordosis with transforaminal lumbar interbody fusion (TLIF). Complications associated with expandable cages have not yet been widely reported. We report a case of postoperative failure of a polyether-ether-ketone (PEEK) expandable interbody device used during TLIF.

Methods

A 50-year-old man presented with severe back and right leg pain after undergoing L4-5 and L5-S1 TLIFs with expandable cages and L3-S1 posterior instrumented fusion. Imaging showed retropulsion of a portion of the interbody cage into the spinal canal causing nerve compression. Displacement occurred in a delayed manner. In addition, pseudoarthrosis was present.

Results

The patient underwent re-exploration with removal of the retropulsed wafer and redo fusion.

Conclusions

Expandable cages are a recent innovation; as such, efficacy and complication data are limited. As with any new device, there exists potential for mechanical failure, as occurred in the case presented.

     

Biomechanical stability of five stand-alone anterior lumbar interbody fusion constructs

Anterior lumbar interbody fusion (ALIF) cages are expected to reduce segmental mobility. Current ALIF cages have different designs, suggesting differences in initial stability. The objective of this study was to compare the effect of different stand-alone ALIF cage constructs and cage-related features on initial segmental stability. Human multi-segmental specimens were tested intact and with an instrumented L3/4 disc level. Five different ALIF cages (I/F, BAK, TIS, SynCage, and ScrewCage) were tested non-destructively in axial rotation, flexion/extension and lateral bending. A cage ‘pull-out’ concluded testing. Changes in neutral zone (NZ) and range of motion (ROM) were analyzed. Cage-related measurements normalized to vertebral dimensions were used to predict NZ and ROM. No cage construct managed to reduce NZ. The BAK and TIS cages had the largest NZ increase in flexion/extension and lateral bending, respectively. Cages did reduce ROM in all loading directions. The TIS cage was the least effective in reducing the ROM in lateral bending. Cages with sharp teeth had higher ‘pull-out’ forces. Antero-posterior and medio-lateral cage dimensions, cage height and wedge angle were found to influence initial stability. The performance of stand-alone ALIF cage constructs generally increased the NZ in any loading direction, suggesting potential directions of initial segmental instability that may lead to permanent deformity. Differences between cages in flexion/extension and lateral bending NZ are attributed to the severity of geometrical cage-endplate surface mismatch. Stand-alone cage constructs reduced ROM effectively, but the residual ROM present indicates the presence of micromotion at the cage-endplate interface. Received: 3 June 1999/Revised: 3 September 1999/Accepted: 8 September 1999     

斜向单枚BAK植入后路腰椎椎体间融合术的生物力学及临床研究

目的 :对作者设计的单枚融合器后斜向植入后路腰椎椎体间融合术行生物力学评价及临床观察。方法 :生物力学研究 :12个小牛脊柱运动节段分为 2组 ,每组 6个。实验组行单侧小关节突、半椎板切除术 ,经侧后方斜向植入加长BAK融合器 1枚 ;对照组行常规后路双侧小关节突、全椎板切除术 ,后前向植入双枚融合器。分别测试两组的纵向压缩、屈曲、侧方弯曲、伸展及双向扭转刚度并进行比较。临床研究 :经后路斜向植入单枚融合器行腰椎椎体间融合术共 40例 ,平均随访 18个月 ,进行临床评价。结果 :生物力学研究显示实验组的垂直压缩刚度、左侧 (融合器植入侧 )弯曲刚度、双侧扭转刚度均较双枚融合器组增大 (P <0 0 5 )。临床随访结果显示 ,患者症状缓解率为 92 % ,术后 1年融合率 88% ,主观满意率 90 % ,所有患者均无融合器的移位。结论 :经侧后方斜向植入单枚融合器的腰椎椎体间融合术 ,能满足后路椎体间融合的生物力学要求 ,有损伤小、脊柱后柱稳定性好、可同时行椎管减压等优点 ,可以较理想地取代后路双枚融合器植入的腰椎椎体间融合术     

单纯斜外侧腰椎椎间融合术后融合器沉降与腰椎矢状面参数的关系

目的:探讨单纯斜外侧腰椎椎间融合术(oblique lumbar interbody fusion,OLIF)术后融合器沉降与腰椎矢状面参数之间的关系.方法:回顾性分析117例接受单节段OLIF手术(无内固定)患者的临床资料,根据椎间隙高度(disc height,DH)下降程度分为融合器0级沉降组(0～24％)、Ⅰ级...     

新型扩张式腰椎椎间融合器的生物力学评价

目的评价新型扩张式腰椎椎间融合器单独单枚使用不附加椎弓根螺钉时的生物力学稳定性能。方法15个人体新鲜标本随机分为圆柱状螺纹融合器组（Interfix）;箱形融合器组（Telamon）;扩张式融合器组（Expanded）。模拟后路腰椎间融合术式将融合器单个置入椎间隙,不附加椎弓根螺钉。将标本放置于力学实验机中加载进行三维六度运动记录运动范围（ROM）。对3种融合器行拔出实验,记录最大拔出强度。结果各种状态下Expanded组ROM值均小于Interfix组和Telamon组,Expanded组最大拔出力为747N,抗拔出强度分别比Telamon组和Interfix组高98．1％和32．4％。结论在单独单个使用情况下,扩张式融合器界面稳定性能高于圆柱状螺纹融合器和箱形融合器,并且在抗滑移性能上也远远超过另2种融合器,在严格适应证下可以单独使用。     

Biomechanical evaluation of an expandable meshed bag augmented with pedicle or facet screws for percutaneous lumbar interbody fusion

Objective

To evaluate the biomechanics of lumbar motion segments instrumented with stand-alone OptiMesh system augmented with posterior fixation using facet or pedicle screws and the efficacy of discectomy and disc distraction.

Background context

OptiMesh bone graft containment system has been used for vertebral compression fractures and percutaneous lumbar interbody fusion. The filled mesh bag serves as the interbody device providing structural support to the motion segment being fused. No biomechanical data of this new device are available in the literature.

Methods

Twenty-four fresh human cadaveric lumbar motion segments were divided into two groups. In the control group, multidirectional flexibility testing was conducted after an intact condition and standard transforaminal lumbar interbody fusion (TLIF) procedure. In the OptiMesh group, testing was performed following intact, stand-alone OptiMesh procedure, OptiMesh with facet screws (placed using the transfacet approach), and OptiMesh with pedicle screws and rods. Range of motion (ROM) was calculated for each surgical treatment. The lordosis and disc height change of intact and instrumented specimens were measured in the lateral radiographs to evaluate the disc space distraction. In the OptiMesh group, cyclic loading in flexion extension (FE) was applied to measure cage subsidence or collapse (10,000 cycles at 6 Nm). After biomechanical testing, all the specimens were dissected to inspect the discectomy and end plate preparation. The area of discectomy was measured.

Results

The mean ROM of the intact specimens was 2.7°, 7.4°, and 7.2° in axial torsion (AT), lateral bending (LB), and FE, respectively. There was no difference between the control group and OptiMesh group. The mean ROM of the stand-alone OptiMesh system decreased to 2.4°, 5.1°, and 4.3° in AT, LB, and FE. The ROM decreased to 0.9° in AT, 2.2° in LB, and 0.9° in FE with OptiMesh system and facet screws. On average, OptiMesh system with pedicle screws and rods reduced the ROM to 1.3° in AT, 1.6° in LB, and 1.1° in FE. Compared with the intact condition and stand-alone OptiMesh system, both posterior fixation options had significant statistical difference (p<.001). In AT, ROM of facet screws was lower than that of pedicle screws (p<.05). There was no statistical difference between the facet and pedicle screws in LB and FE (p>.05). The mean volume of bone graft packed into each bag was 8.3±1.5 cc. The average increase of lordosis was 0.6°±1.0° after meshed bag was deployed. The average distraction achieved by the OptiMesh system was 1.0±0.6 mm. The average prepared area of discectomy was 42% of the total disc. The disc height change after cyclic loading was 0.2 mm. No subsidence or collapse was noticed.

Conclusions

The OptiMesh system offers large volume of bone graft in the disc space with small access portals. The OptiMesh system had similar construct stability to that of standard TLIF procedure when posterior fixation was applied. However, the amount of distraction was limited without additional distraction tools. With the anterior support provided by the expandable meshed bag, facet screws had comparable construct stability to that of pedicle screws. Slightly higher stability was observed in facet screws in AT.     

Biomechanical evaluation of stand-alone interbody fusion cages in the cervical spine.

STUDY DESIGN: An in vitro biomechanical investigation of the immediate stability in cervical reconstruction. OBJECTIVES: The purpose of this study was to compare the segmental stability afforded by the interbody fusion cage, the anterior locking plate, and the "gold standard" autograft. SUMMARY OF BACKGROUND DATA: Recently, interbody fusion cage devices have been developed and used for cervical reconstruction, but to the authors' knowledge no studies have investigated the biomechanical properties of the stand-alone interbody cage device in the cervical spine. METHODS: Using six human cervical specimens, nondestructive biomechanical testing were performed, including axial rotation (+/-1.5 Nm, 50 N preload), flexion/extension (+/-1.5 Nm) and lateral bending (+/-1.5 Nm) loading modes. After C4-C5 discectomy, each specimen was reconstructed in the following order: RABEA cage (cage), tricortical bone graft (autograft), cervical spine locking plate system (plate). Unconstrained three-dimensional segmental range of motion at C4-C5 and above and below were evaluated. RESULTS: In flexion/extension, the plate demonstrated significantly lower range of motion than did the cage and the autograft (P < 0.005), and the cage showed a significantly higher range of motion than did the intact spine (P < 0.05). Under axial rotation, the plate indicated a significantly lower range of motion than did all other groups (P < 0.05). No significant differences were indicated in lateral bending. Adjacent to C4-C5, an increased range of motion was observed. CONCLUSIONS: The increased motion adjacent to C4-C5 may provide an argument for acceleration of disc degeneration. From the biomechanical point of view, this study suggests that the cervical interbody fusion cage should be supplemented with additional external or internal supports to prevent excessive motion in flexion-extension.     

椎间融合器植入颈椎即刻稳定性的生物力学评价

目的 :①探讨不同直径螺纹状椎间融合器对颈椎强度、刚度和稳定性的影响。②椎间融合器植入法改进 ,最佳融合器直径的选择 ,为临床手术提供理论依据。方法 :成人新鲜颈椎标本 12具 ,实验应力分析 ,对颈椎的稳定性与不同程度切除终板、植入不同直径融合器后的生物力学关系进行系统分析和比较。结果 :①椎间融合器植入后 ,颈椎强度增加 2 2 % ,椎体应变下降 15 % ,而刚度增加 43 % ,位移减小 2 0 % ,与植入前颈椎具有非常显著性差异 (P <0 0 1) ,颈椎稳定性得到增强。②在改进植入法中 ,选用直径 11～ 12mm融合器 ,其覆盖椎体终板超过 3 0 %以上 ,接触面积达 65 %以上 ,颈椎最稳定 ,其椎体应变、融合器位移及沉降率最小。结论 :颈椎前路螺纹状椎间融合器植入是一种有效的初始稳定手段 ;改进植入法应选用直径 11～ 12mm之椎间融合器。     

经椎间孔入路单枚融合器结合椎弓根钉治疗腰椎不稳

目的:评价经椎间孔入路单枚椎间融合器植入结合椎弓根钉系统复位固定融合治疗腰椎不稳的应用价值。方法:回顾性分析2006年至2009年腰椎不稳症患者36例39个间隙,其中男14例,女22例;年龄45～68岁,平均54岁;病程6个月～12年,平均4年。其中腰椎间盘突出症不稳8例,腰椎管狭窄症不稳5例,腰椎间盘突出症术后不稳3例,腰椎峡部裂20例;不稳定节段L3,42例,L4,518例,L5S113例,双节段3例(均为L4,5、L5S1)。均采用经椎间孔入路单枚椎间融合器植入结合椎弓根钉系统,行减压、复位、内固定、椎体间及后外侧植骨融合等治疗,按照影像学结果及JOA评分进行疗效评定。结果:36例均获随访,时间8～32个月,平均18个月。结果融合38个椎间隙,可疑融合1个椎间隙,融合率97.4%(38/39)。影像学节段前凸角观察,术后较术前增大(4.09±0.13)°,经统计学分析差异有统计学意义(P0.01),而随访时较术后虽有(3.83±0.17)°的减小,但两者无统计学差异(P0.05)。下腰痛JOA评分术前(8.14±1.09)分,末次随访(13.54±1.19)分,差异有统计学意义(P0.01);同时根据JOA评分好转率(RIS)评定:优28例,良6例,中2例,优良率94.4%。结论:经椎间孔入路单枚椎间融合器植入加椎弓根钉复位固定融合能简化手术操作、减少并发症,是治疗腰椎不稳的有效方法。     

腰椎椎间融合器的翻修手术

目的：探讨后路腰椎间融合器(PLIF cage)术后并发症的再手术方法及疗效。方法：对21例PLIF cage术后并发症患者施行再手术治疗，再手术距植入时间6d～1．5年，其中11例植入时间超过3个月；16例初次手术单纯采用PLIF cage融合；15例植入术后腰及下肢疼痛加剧，其中4例伴间歇性跛行，10例下肢感觉减退；腹部疼痛、不适1例；3例排尿困难；2例单侧、1例双侧小腿不全瘫。影像学检查：20例cage后移位、侵入椎管，1例前移位、突出椎间隙。再手术方法：11例cage重新植入，7例取出，3例椎管扩大减压；12例附加椎弓根固定；7例横突间植骨。结果：平均随访时间14．2个月，13例骨性愈合，3例假关节形成；21例中，5例症状消除，9例部分改善，6例无改变，1例加重，其中8例遗留下腰痛，1例排尿困难。结论：PLIF cage术后并发症再手术困难，疗效欠满意，需尽早行再手术；严格PLIF cage适应证、正确操作，是防止术后并发症的关键。     

Biomechanical analysis of an interbody cage with three integrated cancellous lag screws in a two-level cervical spine fusion construct: an in vitro study

Background contextDespite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels.PurposeTo biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws (“anchored cage”) with a traditional six-hole rigid anterior plate in a two contiguous levels (C4–C5+C5–C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct.Study designA biomechanical laboratory study using cadaveric human cervical spines.MethodsSeven (n=7) cadaveric human cervical spines (C3–C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4–C5 and C5–C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome.ResultsFlex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826).ConclusionsThe anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.     

Biomechanical comparison of anterior lumbar interbody fusion and transforaminal lumbar interbody fusion

STUDY DESIGN: An in vitro biomechanical comparison of 2 fusion techniques, anterior lumbar interbody fusion (ALIF) and transforaminal lumbar interbody fusion (TLIF), on cadaveric human spines. OBJECTIVE: To compare the immediate construct stability, in terms of range of motion (ROM) and neutral zone, of ALIF, including 2 separate approaches, and TLIF procedures with posterior titanium rod fixation. SUMMARY OF BACKGROUND DATA: Both ALIF and TLIF have been used to treat chronic low back pain and instability. In many cases, the choice between these 2 techniques is based only on personal preference. No biomechanical performance comparison between these 2 fusion techniques is available to assist surgical decision. METHODS: Twelve cadaveric lumbar motion segments were loaded sinusoidally at 0.05 Hz and 5 Nm in unconstrained axial rotation, lateral bending and flexion extension. Specimens were randomly divided into 2 groups with 6 in each group. One group was assigned for TLIF whereas the other group for ALIF. In the ALIF group, there were 3 steps. First, the lateral ALIF procedure with the anterior longitudinal ligament (ALL) intact was performed. Afterwards, the ALL was cut without removing the ALIF cage. Finally, another appropriately sized ALIF cage was inserted anteriorly. Biomechanical tests were conducted after each step. RESULTS: In the ALIF group, the lateral ALIF and subsequent anterior ALIF reduced segmental motion significantly (P=0.03) under all loading conditions. Removing the ALL increased ROM by 59% and 142% in axial rotation and flexion extension, respectively (P=0.03). The anterior ALIF approach was able to achieve similar biomechanical stability of the lateral approach in lateral bending and flexion extension (P>0.05) under all loading conditions. The TLIF procedure significantly reduced the range of motion compared with the intact state (P=0.03). However, no statistical difference was detected between the TLIF group and the ALIF group (P>0.05). CONCLUSIONS: Both ALIF and TLIF procedures combined with posterior instrumentation significantly improved construct stability of intact spinal motion segments. However, there was no statistical difference between these 2 fusion techniques. The 2 ALIF approaches (lateral and anterior) also had similar construct stability even though anterior longitudinal ligament severing significantly reduced stability.     

Design and finite-element evaluation of a versatile assembled lumbar interbody fusion cage

Introduction  

When an interbody cage is inserted into a human being’s lumbar spine, not only the design, but also the material used is considerably crucial, particularly when minimally invasive lumbar fusion (MILIF) approaches are considered. The purpose of this study was to design a multi-function cage (either for MILIF or open lumbar interbody fusion) and also to evaluate the strength of the design based on a finite-element model analysis.     

前路腰椎椎体间融合术的生物力学研究

前路腰椎椎体间融合术(ALIF)具有诸多优势,临床应用越来越多.关于ALIF的生物力学稳定性研究国外开展较多,但结果并不完全一致.应根据不同需要合理选择ALIF试验模型,人类尸体,动物尸体、有限元模型、其他替代模型等各有优缺点.单纯ALIF术后椎间获得即刻稳定性是根据"撑开一压缩"原理.前路椎间植入融合器后能够增加除了后伸动作以外的其他各方向稳定性,目前大多数关于ALIF的生物力学测试均针对即刻稳定性,然而融合器植入椎间隙后纤维环弹性逐渐丧失及融合器陷入终板内均会使椎间稳定性逐渐降低,因此椎间融合稳定性还取决于界面骨长入速度等术后因素.影响ALIF稳定性的因素有预负荷、辅助内固定、相邻椎体骨质量等.