Two in vivo surgical approaches for lumbar corpectomy using allograft and a metallic implant: a controlled clinical and biomechanical study

BACKGROUND CONTEXT: Both bone graft and metallic implants have been used in combination with the necessary anterior rod or plate instrumentation to fill the voids left by vertebral body removal, with the ultimate goal of restoring stability. One type of device that has recently been introduced is an expandable titanium telescoping cage that is designed to be used as a strut implant to fill corpectomy defects. The use of these devices has met varying success. Acceptance by surgeons and spine biomechanicians has been limited by clinical failure with subsequent loss of reduction and increase in kyphosis. In order to further improve patient care, it is critical to evaluate the use of these implants through biomechanical as well as other modes of testing. PURPOSE: To compare and contrast the spinal fusion outcome of using allograft bone versus the expandable vertebral body replacement titanium implant in a lumbar corpectomy procedure. STUDY DESIGN: Controlled biomechanical study of lumbar spine fusion using bone graft and the expandable cage in an in vivo bovine model after a 4-month postoperative healing period (n=6). ANIMAL MODEL: Twelve Holstein calves aged 4-6 months with L3 and adjacent discs removed to create a simulated lumbar corpectomy defect. OUTCOME MEASURES: Lumbar spine stability after corpectomy repair was quantified by biomechanical parameters. Strength of fusion was assessed by stiffness of ex vivo spine specimens in flexion-extension, lateral bending, and torsion obtained from biomechanical testing. Uniaxial strain at various positions on the surface of the anterior plate was measured during loading as an additional stability parameter. Loading tests were repeated after removal of the anterior instrumentation (plate and the screws). METHODS: The calves were randomly allocated to groups for corpectomy defect repair with 1) Allograft metatarsal bone and thoracolumbar spine locking plate, n=6; or 2) Expandable vertebral body replacement device, and thoracolumbar spine locking plate, n=6. After a 4-month postoperative period, anterior-posterior and lateral radiographs were taken of the spine, followed by animal sacrifice and harvesting of the lumbar spine for biomechanical and histological testing. For biomechanical testing, uniaxial strain gauges were applied to the thoracolumbar spine locking plate to measure plate deformation during loading in a custom built fixture for application of flexion-extension, lateral bending, and torsion moments in an Instron materials testing machine. These loading tests were repeated with the thoracolumbar spine locking plate removed, thereby loading solely the fused segment. RESULTS: At 4 months postoperative, the stiffness of the calf spines repaired by the metatarsal allograft and thoracolumbar spine locking plate was significantly greater than that of the spines repaired by the expandable cage and thoracolumbar spine locking plate. This finding was true for all three directions of loading (flexion-extension, left-right lateral bending, and torsion). Concordantly, the neutral zone, elastic zone, and range of motion of the spines repaired with the allograft bone were less than that of the spines repaired with the expandable cage. Greater strain values were observed from the gauges on the thoracolumbar spine locking plate of the spines using the expandable cage than the spines using allograft bone. This finding held for all gauge positions (anterior edge, anterior face, posterior edge, and posterior face at the longitudinal midpoint of the plate). After thoracolumbar spine locking plate removal and a repeat of the loading tests, a decrease in stiffness of the construct and a rise in the motion parameters were observed for both the allograft and cage groups. CONCLUSIONS: The use of allograft bone for corpectomy defect repair in the lumbar spine appears to contribute to a stiffer and perhaps more stable spine segment compared with using the expandable cage device for such a repair after a 4-month healing period in this in vivo calf model. These findings thus far are based upon the biomechanical data gathered.     

Comparison of Hydroxyapatite Granules to Autogenous Bone Graft in Fusion Cages in a Goat Model

Background

With the increased use of fusion cages to achieve lumbar intervertebral fusion, the question arises as to the potential for bone ingrowth from the host bone through the entire cage. Is it even necessary to have an autogenous graft to achieve total bone incorporation?

Methods

Nine adult male goats had fusion cages implanted into three vertebral bodies. The design was Surgical Dynamics/Ray Fusion Cage, measuring 21 mm × 14 mm. In each animal, one fusion cage was filled with autogenous graft, one with hydroxyapatite, porous granules, and the other with nonporous granules. Amount of new bone formation was determined by backscatter electron microscopy at 3 months post implantation in all animals.

Results

The histologic section shows that there was total incorporation in all specimens at 3 months. There was slightly more new bone (43%) with the nonporous granules compared with the porous granules (35%). The amount of residual void space was about the same in all specimens, indicating that the amount of new bone formation was similar and not statistically different in cages filled with hydroxyapatite granules versus granules of autogenous bone.

Conclusion

This study confirms that total incorporation by ingrowth of new bone can be expected in fusion cages. The amount of ingrowth is about the same for autogenous graft versus hydroxyapatite granules. Apparently, it is not necessary to use bone graft to achieve successful bone incorporation if an acceptable biocompatable lattice, such as hydroxyapatite granules, is used.     

双节段前路颈椎自锁式融合器融合术后矢状位影像学参数的变化

目的 :观察应用自锁式融合器行前路颈椎融合术(anterior cervical discectomy and fusion,ACDF)后矢状位影像学参数的变化。方法:回顾性分析2010年1月~2014年6月160例接受ACDF的双节段颈椎病患者,其中应用MC+融合器(单锚定组)78例,ROI-C融合器(双锚定组)82例。测量术前、术后3d、术后3个月及末次随访时颈椎侧位X线片的影像学参数,包括手术节段椎间隙高度(height of operation segment,HOS)、椎间隙角度(angle of operation segment,AOS)、C2-C7角、C2-C7矢状位轴向距离(C2-C7 sagittal vertical axis,C2-C7 SVA)及T1倾斜角(T1 slope,T1S),并应用Erk五度分级法评价术后3个月及末次随访时的植骨融合情况。采用Pearson相关性分析160例患者各时间点影像学参数间的相关性;运用独立样本t检验对比同时间点两组间各影像学参数的差异;使用配对样本t检验分别对两组组内不同时间点时各参数进行对比;两组间术后3个月及末次随访时的融合等级对比采用Mann-Whitney U检验;术后3个月及末次随访时两组组内融合等级对比运用Wilcoxon符号秩检验。结果:术后随访13.42±6.01个月(6~31个月)。术前、术后3d、术后3个月及末次随访时AOS与C2-C7角、C2-C7角与T1S、AOS与T1S、T1S与C2-C7 SVA均呈正相关(P0.01),C2-C7SVA与AOS、C2-C7角均无显著相关性(P0.01)。术后3d、3个月及末次随访时两组HOS、AOS、C2-C7角及T1S较术前均有增加(P0.05),术后3个月及末次随访时,双锚定组AOS、C2-C7角及T1S均高于单锚定组,两组比较存在统计学差异(P0.05)。两组术后3个月及末次随访时融合等级对比无统计学差异(P0.05),末次随访时两组融合等级较术后3个月时下降(P0.05)。结论:应用两种自锁式融合器行双节段ACDF均可恢复手术节段椎间隙的高度、角度以及颈椎曲度,ROI-C融合器较MC+融合器对维持术后手术节段角度及颈椎前凸更具优势。ACDF术后颈椎曲度的丢失可能引起胸椎矢状位影像学参数的变化。     

Differential responses to natural and recombinant allergens in a murine model of fish allergy

Aerosolized fish proteins are an important cause of allergic airway reactions in both the domestic and the occupational environment. The aim of this study was to investigate inhalant fish-induced allergy in a mouse model and compare immune responses generated by raw and heat-treated fish extracts as well as natural and recombinant forms of the major fish allergen parvalbumin. Mice were sensitized with raw or cooked pilchard extract and challenged intranasally with cooked pilchard extract, purified natural pilchard parvalbumin or recombinant carp parvalbumin (rCyp c1.01). Cooked pilchard extract predominantly sensitized mice to parvalbumin and induced specific IgG1 and IgE antibodies against both pilchard parvalbumin and rCyp c1.01, whereas additional allergens were recognized by mice sensitized with raw extract, including a 36 kDa allergen that was also recognized by fish processing workers and was identified as glyceraldehyde-3-phosphate dehydrogenase. Mice challenged with cooked extract and purified pilchard parvalbumin had increased Th2 cytokine production in mediastinal lymph node cells and splenocytes, whereas mice challenged with rCyp c1.01 did not. This study identifies a new IgE-binding protein that may be important in occupational allergy to fish and demonstrates the feasibility of testing recombinant allergens for immunotherapeutic potential in vivo.     

Single stage anterior reconstruction using titanium mesh cages in neglected kyphotic tuberculous spondylodiscitis of the cervical spine

Cervical tuberculous spondylodiscitis is a serious, hazardous disorder and to our knowledge, hardly any reports focused on the use of titanium mesh cages in its treatment. The aim of this work is to evaluate the efficacy of using a titanium mesh cage compared to iliac crest grafting regarding correction of the deformity, fusion rate and to report the incidence of complications. A prospective, non-randomized multicentre study of 30 patients with cervical tuberculous spondylodiscitis presenting with a neglected kyphotic deformity. The average age was 44.5 years; 18 had neurological deficits. All patients had a single stage radical debridement, decompression, and instrumentation. The anterior column was reconstructed with a titanium mesh cage in 16 patients (Group 1) and an autogenous iliac bone strut graft in 14 (Group 2). Both groups were followed for a minimum of 2 years. Group 1 showed a better sagittal profile and local kyphosis was corrected from an average of 36° (10°–62°) to an average of −6° (+4° to −16°) compared to Group 2 corrected from an average of 30° (6°–48°) to an average of −1° (+2° to −13°). Group 1 patients showed a solid bony fusion without any recurrence of infection while Group 2 showed a higher incidence of nonunion and of persistent donor site morbidity. The use of titanium mesh cages effectively restores the sagittal profile while adding immediate stability. There is no donor site morbidity, recurrence, or persistence of infection associated with their implantation.     

显微椎间盘镜下B-Twin椎间融合术治疗腰椎退变失稳型椎间盘突出症

目的探讨后路显微椎间盘镜下可膨胀性椎间融合器B-Twin植入椎间融合术治疗腰椎退变失稳型椎间盘突出症的临床疗效。方法 2005年9月~2008年6月,对32例腰椎退变失稳型椎间盘突出症行后路显微椎间盘镜联合可膨胀性椎间融合器B-Twin植入椎间融合术。手术融合节段：L2/31例,L3/43例,L4/518例,L5/S110例,均为单节段。结果植入2枚B-Twin 23例,单枚9例。术后1周VAS疼痛评分由术前8.7±0.3降至2.3±1.7（t=20.64,P=0.001）。随访时间平均25个月（24~29个月）,植骨融合率采用Suk标准：1年融合率为93.8%（30/32）,2年融合率为96.9%（31/32）,B-Twin椎间融合器无明显下沉。结论后路显微椎间盘镜联合可膨胀性椎间融合器B-Twin植入椎间融合术治疗腰椎退变失稳型椎间盘突出症创伤小,植骨融合率高,临床症状缓解满意。     

后路小切口下B-Twin椎间融合术治疗退变性腰椎不稳症

目的:探讨后路小切口下B-Twin椎间融合术治疗退变性腰椎不稳症的手术疗效。方法:2006年1月～2008年12月收治退变性腰椎不稳症患者20例,男11例,女9例,年龄33～65岁,平均44岁。腰椎前屈后伸侧位X线片显示所有患者存在腰椎不稳,其中L4/512例,L5/S18例。MRI显示不稳节段合并中央型椎间盘突出9例,侧方椎间盘突出11例;同时合并腰椎管狭窄15例,其中侧隐窝狭窄11例,中央型椎管狭窄4例。均采用后路小切口下椎间盘切除、神经根管探查减压和B-Twin椎间融合术。结果:手术时间为1.3～2.3h,平均1.8h;术中出血量为70～90ml,平均80.7ml。术中无硬脊膜损伤,术后无脑脊液漏、神经功能损伤、伤口血肿等并发症发生。失访1例,19例随访6个月～2.5年,平均1.3年。患者术前Oswestery功能障碍指数(ODI)评分为38.74±4.70分,术后第3天为12.26±2.18分,术后3个月为9.95±2.39分,末次随访为8.05±2.07分,术后各时间点与术前比较P0.01,术后3个月与术后第3天比较P0.05,末次随访时与术后3个月比较P0.05。术前病变椎间隙高度为9.73±1.49mm,术后第3天为13.53±1.63mm,末次随访为12.32±1.42mm,术后各时间点与术前比较P0.01,末次随访与术后第3天比较P0.05。10例融合器出现2mm以内沉陷,5例出现较明显沉陷(2mm),无融合器脱落。18例患者植骨融合,1例未融合但无任何临床症状。2例仍有腿部疼痛,1例予保守治疗后好转,1例为骨粒脱落所致未进一步治疗。结论:后路小切口下B-Twin椎间融合术治疗退变性腰椎不稳症的创伤较小、安全性较高、近期效果较好。     

Long term outcome and adjacent disc degeneration after anterior cervical discectomy and fusion with titanium cylindrical cages

Background  Anterior cervical discectomy and fusion (ACDF) is widely performed for the treatment of cervical spinal degenerative disease. Autogenic or allogenic bone grafts are used for interbody fusion with satisfactory long term outcomes. However, harvest of the autograft causes donor site complications and allograft is associated with low fusion rate. Threaded titanium cages (TC) have recently been introduced to cope with these disadvantages, but there is little evidence of long term results. Methods  The long term outcome was studied after ACDF using TC. Clinical and imaging follow up was performed in 41 patients for at least 5 years (range 5–8.3 years). New computer-assisted measurement methods for radiographs are proposed. Findings  ACDF with TC achieved 80% excellent or good outcome by Odom’s criteria, 95% fusion rate, and few minor complications. Asymptomatic adjacent disc degeneration was detected in 50% of the patients by our measurement methods. However, symptomatic adjacent disc degeneration occurred in 5% of the patients and only 2% required additional surgery. Conclusions  These results are comparable or better than those after ACDF with autograft or allograft. ACDF with TC can achieve rigid fixation and provide good long term results.     

屏障内独立通风笼与敞口笼饲养雄性Balb/c小鼠的比较

目的：采用独立通风笼（individually ventilated cage, IVC）饲养实验小鼠,积累运行经验和背景数据。方法80只5周龄 SPF 级雄性 Balb/c 小鼠,在屏障内同室分别饲养在换气参数为70、50和30次/h 的 IVC 系统及敞口笼内8周,各设置5只/笼和10只/笼2种饲养密度;每周逐只称重、第8周进行大体剖检,主要脏器称重;以Excel 软件绘制体重曲线,以 SPSS 软件统计各饲养组两两间差异。结果①5只/笼饲养的动物体重曲线优于10只/笼;②与设置为30和70次/h 换气的 IVC 相比,无论是5只/笼或10只/笼饲养,换气50次/h 的 IVC 饲养动物体重曲线平滑度及趋势均更加接近5只/笼传统敞口饲养;③组间体重未因饲养设施或密度因素造成显著差异（P＞0.05）;④IVC 在30次/h 换气5只/笼饲养比敞口10只/笼饲养时的肝脏系数显著高（P ＜0.05）,该参数的其它组间、及其它脏器系数值均未见组间差异显著（P ＞0.05）。结论根据实验结果,推荐该型号 IVC 换气次数设置为50次/h,饲养 Balb/c 小鼠密度5只/笼为佳。