Primary stabilizing effect of interbody fusion devices for the cervical spine: an in vitro comparison between three different cage types and bone cement

Interbody fusion cages are small hollow implants that are inserted into the intervertebral space to restore physiological disc height and to allow bony fusion. They sometimes cause clinical complications due to instability, subsidence or dislocation. These are basic biomechanical parameters, which influence strongly the quality of a fusion device; however, only few data about these parameters are available. Therefore, the purpose of the present study was to investigate the primary stabilizing effect of four different cervical fusion devices in in vitro flexibility tests. Twenty-four human cervical spine segments were used in this study. After anterior discectomy, fusion was performed either with a WING cage (Medinorm AG, Germany), a BAK/C cage (Sulzer SpineTech, USA), an AcroMed cervical I/F cage (DePuy AcroMed International, UK) or bone cement (Sulzer, Switzerland). All specimens were tested in a spine tester in the intact condition and after implantation of one of the four devices. Alternating sequences of pure lateral bending, flexion-extension and axial rotation moments (+/- 2.5 Nm) were applied continuously and the motions in each segment were measured simultaneously. In general, all tested implants had a stabilizing effect. This was most obvious in lateral bending, where the range of motion was between 0.29 (AcroMed cage) and 0.62 (BAK/C cage) with respect to the intact specimen (= 1.00). In lateral bending, flexion and axial rotation, the AcroMed cervical I/F cages had the highest stabilizing effect, followed by bone cement, WING cages and BAK/C cages. In extension, specimens fused with bone cement were most stable. With respect to the primary stabilizing effect, cages, especially the AcroMed I/F cage but also the WING cage and to a minor extent the BAK/C cage, seem to be a good alternative to bone cement in cervical interbody fusion. Other characteristics, such as the effect of implant design on subsidence tendency and the promotion of bone ingrowth, have to be determined in further studies.     

Stabilizing effect and sintering tendency of 3 different cages and bone cement for fusion of cervical vertebrae segments

Important requirement for spinal fusion devices for segment are that they provide sufficient stability and guarantee a low subsidence risk. An important requirement for spinal fusion devices for segments are that they provide sufficient stability and guarantee a low subsidence risk. Therefore, in the following in vitro study, the stabilizing effect and subsidence tendency of cervical fusion cages and bone cement were investigated during cyclic loading. The WING cages (Medinorm AG) and BAK cages (Spinetec) made of titanium, the carbon fiber reinforced PEEK cage from Acromed (DePuy Acromed), and bone cement (PMMA, Sulzer) were tested. Twenty-four human cervical spine specimens were first tested intact with a standardized flexibility test (+/- 2.5 Nm). Then the implants were inserted and the primary stability determined. For the simulation of the postoperative loading of the cervical spine a cyclic loading protocol with 700 loading cycles was performed. In this test pure moments +/- 2.0 Nm in 9 different loading directions in randomized order were applied together with a 50 N preload to simulate the weight of the head. The subsidence and "long term stability" was measured after 50, 100, 200, 300, 500, and 700 cycles. All implants had a stabilizing effect in all directions most obviously in lateral bending. Here the range of motion was between 20.9% (AcroMed Cage), and 62% (BAK Cage) with respect to the intact specimen (100%). In laterial bending, flexion, and axial rotation the AcroMed cage stabilized the most followed by the bone cement, WING and BAK Cage. In extension the specimens treated with bone cement were the most stable. After 700 loading cycles the specimens with the BAK cage lost 1.6 mm in height, with the WING Cage 0.8 mm, with the Acromed 0.7 mm, and with the bone cement 0.5 mm. Two Acromed Cages dislocated during the long term testing. Cages have the potential to stabilize as effectively as bone cement. A smaller contact area, however, causes a higher subsidence risk compared to bone cement but increases the fusion area, thus increasing the chance of obtaining bony fusion.     

Subsidence resulting from simulated postoperative neck movements: an in vitro investigation with a new cervical fusion cage

STUDY DESIGN: A biomechanical in vitro subsidence test of different cervical interbody fusion devices was performed using a new testing protocol that simulates physiologic conditions. OBJECTIVES: To investigate the effect of simulated postoperative neck movements on the subsidence of the new WING cervical interbody fusion cage in comparison with two other cages and bone cement. SUMMARY OF BACKGROUND DATA: Cervical interbody fusion cages sometimes cause complications because of subsidence into the adjacent vertebrae with collapse of the intervertebral space. Complications such as cage dislocation or nonunion with instability also have been reported. To prevent such complications, the new WING cervical interbody fusion cage (Medinorm AG, Quierschied, Germany) has been developed. Its area of contact with the adjacent vertebrae is supposed to be large enough to resist excessive subsidence and small enough to prevent stress protection of the tissue growing in the cage. METHODS: In this study, 24 human cervical spine specimens were tested after stabilization with either a WING, BAK/C, AcroMed I/F cage or bone cement. Then, in a new testing protocol, 700 pure-moment loading cycles (+/-2 Nm) were applied in randomized directions (lateral bending, flexion-extension, and axial rotation alone or in combination with each other) to simulate the patient's neck movements during the first few postoperative days. Measurements of the subsidence depth (total height loss) in combination with flexibility tests (+/-2.5 Nm) were performed before cyclic loading and after 50, 100, 200, 300, 500, and 700 loading cycles. RESULTS: Cyclic loading caused subsidence in all four device groups, most distinct with BAK/C-cages (1.63 mm after 700 loading cycles) followed by the new WING (0.90 mm) and the AcroMed (0.82 mm) cages. No statistically significant difference could be found among the three cage designs. However, all three cage types showed a significantly higher subsidence depth than bone cement (0.48 mm;P = 0.023 between each of the three cage-types and bone cement). A moderate correlation between bone mineral density and subsidence depth could be found only in the BAK/C group (r2 = 0.495). A large subsidence depth after 700 loading cycles was associated with a large flexibility increase in the WING (r2 = 0.786) and AcroMed groups (r2 = 0.21), but with a small flexibility increase in the BAK/C group (r2 = 0.58). CONCLUSIONS: Postoperative neck movements caused subsidence in all cervical interbody implant types. The new WING cage and the AcroMed cage seemed to have a better resistance against subsidence than the BAK/C cage. However, all three cage types had a significantly higher subsidence tendency than bone cement.     

Revision strategies for salvaging or improving failed cylindrical cages.

STUDY DESIGN: This is a review of 20 patients who experienced failure of threaded interbody fusion cages and underwent surgical correction. OBJECTIVE: To review the causes and possible treatment strategies for failed cylindrical cages. SUMMARY OF BACKGROUND DATA: Intraoperative complications have been described in the past; however, management of the postoperative patient with failure of interbody fusion devices has not been described. METHODS: In 20 patients with failed threaded titanium fusion cages (18 Bagby and Kuslich Devices [BAK; Sulzer-Spine Tech, Minneapolis, MN], 2 Ray Threaded Fusion Cages [Ray TFC; Surgical Dynamics, Norwalk, CT) who underwent revision surgery, all had failure before successful arthrodesis was achieved. Eight of the original titanium cages had been inserted anteriorly (7 laparoscopically), and 12 had been inserted for posterior interbody lumbar fusion. Before the revision surgery, five of the implants were thought to be solid by the referring surgeon, but pseudarthrosis was clearly present in all. In addition, 14 other explanted BAK devices were subjected to undecalcified histologic preparation, quantitative histomorphometry, and histopathologic analysis. RESULTS: The average length of time before revision surgery (implant duration) was 31.8 weeks (range, 1-156 weeks). The most common revision procedure was posterior exploration of the symptomatic nerve root with foraminotomy for unrecognized lateral recess stenosis (11 cases) or excision of iatrogenically herniated intervertebral disc fragments (4 cases). However, four cages inserted through posterior exposure during an interbody lumbar fusion procedure had to be removed because of migration into the spinal canal. In nine cases posterior pedicle screw instrumentation was necessary in addition to posterolateral fusion using iliac crest bone grafting. CONCLUSIONS: All 20 cages failed because of surgical technique rather than an intrinsic defect in fusion cage technology. The factors associated with failure of the original insertion procedure were failure to achieve adequate distraction of the anulus fibrosis; undersized cages, especially when placed through the posterior interbody lumbar fusion approach; cerebrospinal fluid leakage or pseudomeningocele; Type 2 diabetes mellitus; the use of local bone graft rather than iliac crest inside the cage; anterior insertion in an excessively lateral position resulting in symptoms of a far lateral disc herniation; and failure to identify the spinal midline during an anterior approach.     

Efficacy and safety of the use of titanium mesh cages and anterior cervical plates for interbody fusion after anterior cervical corpectomy

BACKGROUND: To determine the safety and effectiveness of the use of titanium mesh cages (TMCs) and anterior cervical plates (ACPs) for interbody fusion after anterior cervical corpectomy. METHODS: From June 2001 to June 2003, 15 patients underwent reconstruction with TMCs and ACPs for interbody fusion after anterior cervical corpectomy in our hospital. The mean follow-up is 13.6 months (range, 9-24 months). Subjects included those with cervical degenerative, traumatic, or pathological diseases. Titanium mesh cages were filled with autologous bone grafts taken from the corpectomy and iliac crest bone chips and were all filled with triosite (calcium phosphate ceramics). The patients' observable signs, neurological reconstruction results, and complications were fully and explicitly recorded throughout the procedure. Radiological imaging studies for measurements of coronal and sagittal angles, sagittal displacements, and settling ratio changes were performed to evaluate spinal stability. We used axial cervical computed tomography (CT) and reconstructive sagittal cervical CT to demonstrate interbody fusion within titanium mesh. RESULTS: The alleviation and frequent disappearance of the subjects' original symptoms and the significant neurological recovery obvious in most patients indicated that postoperative spinal stability could be well maintained. No significant differences in mean cage height-related settling rates, mean sagittal displacements, and mean coronal and sagittal angle changes were observed between 1-level and multilevel corpectomy. All patients who received axial and reconstructive sagittal cervical CT scan could demonstrate true interbody fusion within TMC, and no nonunions were present. Cage malplacement was observed in one subject who had neck pain and neck stiffness, rather than from radiculopathy or myelopathy. One subject died of acute myocardial infarction. There were no ceramic-related complications. CONCLUSIONS: Based on preliminary findings from this study, reconstruction involving TMC interbody fusion with ACP fixation after anterior cervical corpectomy serves as an effective and safe method for the treatment of cervical disease.     

The biomechanical significance of anterior column support in a simulated single-level spinal fusion

This study examines the biomechanical effects of interbody cages and variations in posterior rod diameter in a simulated single-level spinal fusion. A single-level spinal fusion model composed of polyethylene cylinders, posterior pedicular instrumentation, and variously positioned single or dual interbody cages was used for biomechanical testing. Constructs were tested under compressive flexural load, with measurement of stiffness, rod strain, cage strain, and intracage pressure. A strong linear correlation emerged between the mean construct stiffness and cage positioning within the sagittal plane that was inversely related to posterior rod strain. Two small titanium mesh cages were equivalent to one large cage. In a single-level spine model, the presence of and sagittal position of interbody cages significantly influences overall construct stiffness. Cage strain increased with more anterior positions and was inversely related to rod strain.     

Intervertebral fixation: clinical results with anterior cages

Anterior lumbar interbody fusion has several clinical advantages over posterior or posterolateral lumbar fusion. Interbody fusion procedures place bone grafts within the disc space at the center of rotation of the vertebral motion segment. The intervertebral area is highly vascular, and the grafts have a wide contact area in the weight-bearing axis of the spinal motion segment. The high rates of fusion associated with the use of the threaded intervertebral fusion cages may be attributed, in part, to the following: (1) removal of the cartilagenous end plates and exposure of bleeding cancellous bony surfaces, (2) reestablishment of anatomic intradiscal height and tensioning of the annulus and ligamentous structures around the disc space, (3) use of appropriately sized implants to engage the peripheral apophysis of the vertebral end plates, and (4) use of autogenous grafts. Threaded interbody constructs provide adequate strength to ensure that no plastic deformation occurs within the maximum physiologic range. Dynamic testing of these implants also has shown that these implants are able to resist cyclic fatigue within typical normal daily physiologic loading. Stability testing has shown that when inserted anteriorly, these devices reduce intervertebral motion and increase spinal stiffness.     

Segmental stability and compressive strength of posterior lumbar interbody fusion implants

STUDY DESIGN: Human cadaveric study on initial segmental stability and compressive strength of posterior lumbar interbody fusion implants. OBJECTIVES: To compare the initial segmental stability and compressive strength of a posterior lumbar interbody fusion construct using a new cortical bone spacer machined from allograft to that of titanium threaded and nonthreaded posterior lumbar interbody fusion cages, tested as stand-alone and with supplemental pedicle screw fixation. SUMMARY OF BACKGROUND DATA: Cages were introduced to overcome the limitations of conventional allografts. Radiodense cage materials impede radiographic assessment of the fusion, however, and may cause stress shielding of the graft. METHODS: Multisegmental specimens were tested intact, with posterior lumbar interbody fusion implants inserted into the L4/L5 interbody space and with supplemental pedicle screw fixation. Three posterior lumbar interbody fusion implant constructs (Ray Threaded Fusion Cage, Contact Fusion Cage, and PLIF Allograft Spacer) were tested nondestructively in axial rotation, flexion-extension, and lateral bending. The implant-specimen constructs then were isolated and compressed to failure. Changes in the neutral zone, range of motion, yield strength, and ultimate compressive strength were analyzed. RESULTS: None of the stand-alone implant constructs reduced the neutral zone. Supplemental pedicle screw fixation decreased the neutral zone in flexion-extension and lateral bending. Stand-alone implant constructs decreased the range of motion in flexion and lateral bending. Differences in the range of motion between stand-alone cage constructs were found in flexion and extension (marginally significant). Supplemental posterior fixation further decreased the range of motion in all loading directions with no differences between implant constructs. The Contact Fusion Cage and PLIF Allograft Spacer constructs had a higher ultimate compressive strength than the Ray Threaded Fusion Cage. CONCLUSIONS: The biomechanical data did not suggest any implant construct to behave superiorly either as a stand-alone or with supplemental posterior fixation. The PLIF Allograph Spacer is biomechanically equivalent to titanium cages but is devoid of the deficiencies associated with other cage technologies. Therefore, the PLIF Allograft Spacer is a valid alternative to conventional cages.     

Cervical Cage Fusion with 5 Different Implants: 250 Cases

Summary. Summary.   Background: Anterior decompression with interbody fusion is the surgical procedure of choice in cervical spondylosis. Graft harvesting complications occuring from classical fusion procedures favoured ongoing development of cage technology. To evaluate efficiency of cage fusion for surgical treatment of discogenic cervical disorders, this six-year retrospective study analyses 250 consecutive cases treated by interbody cage fusion with 5 different implants.   Methods: Indications for fusion concerned degenerative discopathies, disc herniations and selected cases of failed surgery presenting with radiculopathy (228 cases) or myelopathy (22 cases). Screwed threaded titanium cages (149 cases), impacted squared or anatomically shaped Peek cages (59 cases), and impacted titanium cages (42 cases) were used together with local graft or bone substitute. Additional plating was indicated in 16 unstable cases.   Findings: Excellent outcome for neck pain (96%) and radiculopathy (97%) was noted, but a less favourable one for myelopathy (60%). All cases were stabilised at 1 year. Complications leading to reoperation included cage migration and subsidence, adjacent level degeneration and stenotic myelopathy.   Interpretation: Cage technology simplified anterior cervical interbody fusion and proved efficient. The fact there was no graft harvesting saved operating time and hospital stay.   Statement: It is not the intention of the author to indicate material preference in this article. Published online June 20, 2002     

减压碎骨块行椎间融合治疗退变性腰椎不稳并狭窄病例对照研究

目的:探讨自体减压碎骨块在椎间融合中的价值。方法 :2014年4月至2015年5月,采用后路全椎板减压钉棒固定单侧改良TLIF入路椎间融合治疗退变性腰椎不稳并狭窄42例,男18例,女24例,其中24例单纯用自体减压碎骨块为椎间融合材料(治疗组),18例用cage加自体骨作为椎融合材料(对照组)。分析两组临床资料情况,对比两种治疗方式的骨性愈合时间、椎间融合率、椎间隙高度以及疗效的差异。结果:42例患者均获得随访,时间12~24个月,平均16个月。两组患者在发病年龄、性别比例、腰椎不稳程度及随访时间上差异无统计学意义(P0.05);两组患者在临床疗效、椎间高度丢失情况、椎间融合率的差异也无统计学意义(P0.05)。结论:利用减压碎骨块行椎间融合治疗退变性腰椎不稳并狭窄,术后融合率高,椎间隙高度维持良好,临床疗效满意,设计科学合理,并发症少,为治疗退变性腰椎管不稳并椎管狭窄提供了经济、实用、临床疗效确切的治疗方法。     

Clinical and radiographic assessment of transforaminal lumbar interbody fusion using HEALOS collagen-hydroxyapatite sponge with autologous bone marrow aspirate

Background contextStudies have suggested that the use of bone marrow aspirate (BMA) with HEALOS (DePuy Spine, Raynham, MA), a collagen-hydroxyapatite sponge (CHS), is an effective substitute for autologous iliac crest bone graft when used in fusion procedures of the lumbar spine.PurposeTo assess clinical and radiographic outcomes after implantation of BMA/CHS in patients undergoing transforaminal lumbar interbody fusion (TLIF) with posterolateral fusion (PLF).Study design/settingCase series radiographic outcome study.Patient sampleTwenty patients.Outcome measuresRadiographs/computed tomography (CT) scans.MethodsFrom September 2003 to October 2004, 20 patients (22 interbody levels) were implanted with BMA/CHS via TLIF/PLF with interbody cages and posterior pedicle screws. All patients were retrospectively identified and invited for a 2-year prospective follow-up. Plain radiographs with dynamic films and CT scans were taken, and fusion was assessed in a blinded manner.ResultsFollow-up averaged 27 months (range: 24–29). Primary diagnosis included spondylolisthesis (17 patients), scoliosis with asymmetric collapse (2 patients), and postdiscectomy foraminal stenosis (1 patient). The overall fusion rate was 95% (21/22 levels, 19/20 patients). Anteriorly bridging bone was observed in 91% of the anteriorly fused levels (20/22), of which 65% (13/20) occurred through and around the cage and 35% (7/20) around the cage only. Unilateral or bilateral bridging of the posterior fusion masses was observed in 91% (20/22), with 55% occurring bilaterally (12/22). In 4 (18%) cases, bridging only occurred either posteriorly (2 cases) or anteriorly (2 cases). Complications included one deep wound infection.ConclusionsAt the 2-year follow-up, BMA/CHS showed acceptable fusion rates in patients undergoing TLIF/PLF, and can be considered as an alternative source of graft material.     

Advances in Spinal Interbody Cages

Since the late 1980s, spinal interbody cages (ICs) have been used to aid bone fusion in a variety of spinal disorders. Utilized to restore intervertebral height, enable bone graft containment for arthrodesis, and restore anterior column biomechanical stability, ICs have since evolved to become a highly successful means of achieving fusion, being associated with less postoperative pain, shorter hospital stay, fewer complications and higher rates of fusion when than bone graft only spinal fusion. IC design and materials have changed considerably over the past two decades. The threaded titanium‐alloy cylindrical screw cages, typically filled with autologous bone graft, of the mid‐1990s achieved greater fusion rates than bone grafts and non‐threaded cages. Threaded screw cages, however, were soon found to be less stable in extension and flexion; additionally, they had a high incidence of cage subsidence. As of the early 2000s, non‐threaded box‐shaped titanium or polyether ether ketone IC designs have become increasingly more common. This modern design continues to achieve greater cage stability in flexion, axial rotation and bending. However, cage stability and subsidence, bone fusion rates and surgical complications still require optimization. Thus, this review provides an update of recent research findings relevant to ICs over the past 3 years, highlighting trends in optimization of cage design, materials, alternatives to bone grafts, and coatings that may enhance fusion.     

Early bone ingrowth and segmental stability of a trussed titanium cage versus a polyether ether ketone cage in an ovine lumbar interbody fusion model

BACKGROUND CONTEXTLumbar interbody fusion is an effective treatment for unstable spinal segments. However, the time needed to establish a solid bony interbody fusion between the two vertebrae may be longer than twelve months after surgery. During this time window, the instrumented spinal segment is assumed to be at increased risk for instability related complications such as cage migration or subsidence. It is hypothesized that the design of new interbody cages that enable direct osseointegration of the cage at the vertebral endplates, without requiring full bony fusion between the two vertebral endplates, might shorten the time window that the instrumented spinal segment is susceptible to failure.PURPOSETo quantify the bone ingrowth and resulting segmental stability during consolidation of lumbar interbody fusion using two different cage types.STUDY DESIGNPreclinical ovine model.METHODSSeven skeletally mature sheep underwent bi-segmental lumbar interbody fusion surgery with one conventional polyether ether ketone (PEEK) cage, and one newly developed trussed titanium (TT) cage. After a postoperative time period of 13 weeks, non–destructive range of motion testing, and histologic analysis was performed. Additionally, sample specific finite element (FE) analysis was performed to predict the stability of the interbody fusion region alone.RESULTSPhysiological movement of complete spinal motion segments did not reveal significant differences between the segments operated with PEEK and TT cages. The onset of creeping substitution within the cage seemed to be sooner for PEEK cages, which led to significantly higher bone volume over total volume (BV/TV) compared with the TT cages. TT cages showed significantly more direct bone to implant contact (BIC). Although the mean stability of the interbody fusion region alone was not statistically different between the PEEK and TT cages, the variation within the cage types illustrated an all-or-nothing response for the PEEK cages while a more gradual increase in stability was found for the TT cages.CONCLUSIONSSpinal segments operated with conventional PEEK cages were not different from those operated with newly developed TT cages in terms of segmental stability but did show a different mechanism of bone ingrowth and attachment. Based on the differences in development of bony fusion, we hypothesize that TT cages might facilitate increased early segmental stability by direct osseointegration of the cage at the vertebral endplates without requiring complete bony bridging through the cage.CLINICAL SIGNIFICANCEInterbody cage type affects the consolidation process of spinal interbody fusion. Whether different consolidation processes of spinal interbody fusion result in clinically significant differences requires further investigation.     

Radiographic characteristics on conventional radiographs after posterior lumbar interbody fusion: comparative study between radiotranslucent and radiopaque cages.

The problem of determining solidity of a fused spinal segment still remains. Our purpose is to evaluate radiographic findings after posterior lumbar interbody fusion (PLIF) with cages and estimate their relative value in judging fusion status. Radiographic follow-up was performed in patients after PLIF with cages of either radiotranslucent or radiopaque material. Conventional radiographs were obtained 6 weeks, 3 and 6 months, and then yearly after surgery for spinal instability for 64 patients. We differentiated between uncertain (increased density within the cage, increase of sclerotic endplates, and posterolateral fusion) and definite (trabecular continuous bone bridging within the implant and periimplant new bone formation with bridging of the intervertebral space) fusion signs. A fusion rate of 51.5% after 12 months, 61.4% after 24 months, 66.7% after 36 months, and 77.8% after 48 months postoperatively was found. We found only a slight, nonsignificant correlation between radiographic fusion and patient-assessed clinical outcome. There is evidence that radiographic fusion criteria occur in a specific chronologic order. The interpretation of fusion status is notably impaired by the use of radiopaque cages. Criteria to standardize the interpretation and evaluation of radiographic findings after PLIF are discussed.     

Comparison in the same intervertebral space between titanium-coated and uncoated PEEK cages in lumbar interbody fusion surgery

BackgroundsDisadvantages of polyetheretherketone (PEEK) cages are their smooth and hydrophobic surfaces and their lack of osteoconductivity. Titanium (Ti) coated PEEK cage has been innovated to overcome these potential concerns. However, few well-designed studies have investigated the efficacy of Ti-coated PEEK cage on interbody fusion in humans. This study aimed to evaluate the efficacy of Ti coating on bone ongrowth at bone–implant surface by simultaneously comparing Ti-coated and uncoated PEEK cages in the same intervertebral space.MethodsThis study is a prospective comparative study for the two different cages. Twenty-six subjects who underwent one-level instrumented posterior lumbar interbody fusion (PLIF) were included. Two PEEK cages [a plasma-sprayed Ti-coated (PTC-PEEK) and an uncoated PEEK cage] were inserted in the same intervertebral space. Fusion rates, cage subsidence, and vertebral cancellous condensation (VCC) around the cage, which indicates bone growth on the surface of each cage, were assessed by thin-slice computed tomography (CT) immediately (within 1 week) and at 3 months postoperatively. A functional radiograph was obtained at 3 and 12 months postoperatively.ResultsTwenty-three subjects showed solid fusion at 3 months postoperatively (fusion rate, 88%). Cage subsidence was not observed. VCC was often observed around the PTC-PEEK cage as evaluated by completely synchronized CT images between immediately and at 3 months postoperatively. Quantified VCC around the cage was significantly larger in the PTC-PEEK cage than in the uncoated PEEK cage (P = 0.01).ConclusionsThe Ti-coated PEEK cage exhibits radiographic signs, suggesting bone ongrowth, as represented by VCC around the cage compared with that around the uncoated PEEK cage. The Ti-coated PEEK cage has the potential to promote solid fusion and to improve clinical outcomes in lumbar interbody fusion surgery.     

颈椎椎间融合器翻修术

目的 分析颈椎椎间融合器(以下简称Cage)手术失败的原因，探讨颈椎Cage翻修手术的适应证、手术方式和手术效果。方法 颈椎Cage翻修术27例．其中颈椎间盘突出症4例。神经根型颈椎病2例，脊髓型颈椎病21例；单节段Cage 8例，双节段15例，三节段4例。就诊时距原手术时间2～25个月．平均10．3个月。患者表现为颈肩部不适22例，颈肩部疼痛9例，脊髓压迫症状19例，术前JOA评分平均11．6分，翻修术前颈椎曲度较原手术术后当时平均丢失7.1mm、椎间高度平均丢失3．9mm，24例出现颈椎后凸畸形．多节段者均出现两个Cage交错咬合现象，植骨不愈合6例．动态X线片显示颈椎不稳9例，CT或MRI显示减压节段仍存在压迫19例。对23例(29个Cage)行前路Cage取出、减压植骨、钢板固定，其中16例加后路侧块螺钉钢板固定植骨融合术；4例(9个Cage)行后路椎板减压、矫形固定。结果 全部病例随访4～26个月．平均11．7个月，较翻修术前颈肩部症状改善率为81％．脊髓压迫症状改善率为58％．术后JOA评分平均14.2分．前路翻修中17例植骨块于术后3个月时愈合，6例延迟愈合。颈椎后凸畸形消失，椎间高度平均增加3mm．未出现神经损伤和内固定失败病例，结论 Cage手术失败原因包括减压不够彻底、Cage沉陷产生颈椎曲度的丢失和植骨不愈合，翻修的适应证为神经症状进行性加重或出现颈椎不稳、畸形者、翻修时尽量采用前入路，取出Cage，彻底减压，植骨固定。注意保留原有的骨质和颈椎的活动节段．长节段融合时应加后路固定.     

后路椎间融合术治疗老年腰椎间盘突出症的安全性

目的探讨后路椎间融合术治疗老年椎间盘突出症的方法、应用价值及安全性。方法对89例确诊为老年椎间盘突出症的患者进行开放后路椎间融合术,包括后正中开放入路,扩大开窗、半椎板或全椎板切除,椎管扩大成形,椎弓根螺钉植入,椎间撑开切除椎间盘,刮除终板软骨层,植入经修剪的颗粒骨、大块关节突骨块、椎板骨块,或椎间Cage融合器,椎弓根螺钉系统加压固定。结果所有患者术前均经详尽检查除外绝对手术禁忌,其中约65%曾请相关科室会诊指导围手术期处理。平均手术时间为100min,平均失血量350mL。所有病例均经术后随访,随访时间为12～24个月,原有的神经压迫症状基本恢复,无间隙性跛行,下腰痛较术前明显缓解,患者满意率91%。椎间高度术前3.4～7.8mm,平均高度5.1mm,术后3个月椎间高度9.6～12.4mm,平均11.2mm。在12个月随访时平均高度为9.0～12.1mm,平均为10.8mm。12个月椎间融合率91.0%。主要并发症为:10例患者出现神经根刺激症状,4例患者出现脑脊液漏,均缓解,无一例出现严重感染或危重并发症。结论应用后路椎体间融合技术结合椎弓根钉棒固定技术治疗老年腰椎间盘突出症能够充分减压,恢复并维持椎间隙高度,重建腰椎稳定性,并具备手术安全性。     

后路椎体间微粒骨打压植骨融合

目的探讨后路椎体间微粒骨打压植骨的手术技术和临床可行性。方法对28例60岁以上腰椎退变性疾病患者、2例L1骨折脱位患者和1例T12硬脊膜瘤患者行后路椎体间微粒骨打压植骨融合。观察手术前后症状、体征、X线片腰椎前凸角、椎间隙高度指数的变化,以及手术后CT检查椎体间植骨面积。结果随访6~26个月。术前症状及体征均缓解,腰椎前凸角、椎间隙高度指数均有明显恢复,脊柱融合率达96.1%。未发生植入骨的吸收、移位和沉陷。主要有手术中硬脊膜撕裂、神经根牵拉以及手术出血等并发症。结论后路椎体间微粒骨打压植骨融合是一种可行的椎体间融合方法。     

Posterior lumbar interbody fusion (PLIF) with cages and local bone graft in the treatment of spinal stenosis

Posterior lumbar interbody fusion (PLIF) implants are increasingly being used for 360 degrees fusion after decompression of lumbar spinal stenosis combined with degenerative instability. Both titanium and PEEK (PolyEtherEtherKetone) implants are commonly used. Assessing the clinical and radiological results as well as typical complications, such as migration of the cages, is important. In addition, questions such as which radiological parameters can be used to assess successful fusion, and whether the exclusive use of local bone graft is sufficient, are frequently debated. We prospectively evaluated 30 patients after PLIF instrumentation for degenerative lumbar spinal canal stenosis, over a course of 42 months. In all cases, titanium cages and local bone graft were used for spondylodesis. The follow-up protocol of these 30 cases included standardised clinical and radiological evaluation at 3, 6, 12 and 42 months after surgery. Overall satisfactory results were achieved. With one exception, a stable result was achieved with restoration of the intervertebral space in the anterior column. After 42 months of follow-up in most cases, a radiologically visible loss of disc space height can be demonstrated. Clinically relevant migration of the cage in the dorsal direction was detected in one case. Based on our experience, posterior lumbar interbody fusion (PLIF) can be recommended for the treatment of monosegmental and bisegmental spinal stenosis, with or without segmental instability. Postoperative evaluation is mainly based on clinical parameters since the titanium implant affects the diagnostic value of imaging studies and is responsible for artefacts. The results observed in our group of patients suggest that local autologous bone graft procured from the posterior elements after decompression is an adequate material for bone grafting in this procedure.     

Vertebral bone resorption after transforaminal lumbar interbody fusion with bone morphogenetic protein (rhBMP-2)

OBJECTIVE: Bone morphogenetic protein (rhBMP-2) has demonstrated an increased rate of interbody fusion when placed in the intervertebral space. Owing to this advantage, rhBMP-2 is being implanted with increasing frequency in the lumbar spine. The purpose was to quantify and describe the presence of bone resorption within the vertebral body after transforaminal lumbar interbody fusion with placement of rhBMP-2 within the disc space. METHODS: Twenty-six patients were selected from a clinical database. Patients included in the study had undergone a transforaminal lumbar interbody fusion with BMP. Interbody implants included allograft dowels or interbody cages augmented with autograft or allograft bone. A computed tomography study of the lumbar spine a minimum of 3-month postoperatively was another inclusion criterion. Osteolytic defects were grouped into 3 categories on the basis of the size and extent of involvement in the vertebral body. RESULTS: A total of 32 lumbar levels were reviewed. Fourteen males and 12 females with an average age of 46.0 years were included in the study. Bone resorption defects were noted in 22 of the 32 levels reviewed (69%). The defects were characterized as mild in 50% (11 of 22), moderate in 18% (4 of 22), and severe in 31% (7 of 22). CONCLUSIONS: The benefit of rhBMP-2 to promote interbody fusion in the lumbar spine has been well documented. BMP has demonstrated an increased fusion rate and the ability to produce a robust fusion mass. rh-BMP-2's osseous remodeling potential may lead to bone resorption within the vertebral body.