小梁金属(多孔钽)在骨科的应用现状

骨科学科的发展与手术器械和植入材料的发展密不可分.小梁金属(多孔钽)是近年来出现的一种较理想的骨科植入材料,由纯商业钽制成,它克服了目前临床上常用的不锈钢及钛、镍、钴、铬等金属的合金制成的植入器械整体孔隙率低、表面摩擦系数小、弹性模量较高等缺点,具有较大的空隙率与表面摩擦力、有与人体骨质接近的弹性模量、有更低的成块硬化性、有较好的生物相容性,被认为是一种较理想的骨科植入材料[1].小梁金属虽然国内还未见使用,但在国外已广泛应用于骨科临床.本文就多孔钽的理化、生物学特性及在骨科中的应用现状作一介绍.     

多孔钽在骨组织工程中的研究进展

目的对多孔钽在骨组织工程中的研究进展作一综述。方法查阅近年多孔钽在制备、细胞生物学、表面修饰等领域的基础研究文献,并总结分析。结果多孔钽自身特有的理化性质赋予其良好的组织相容性、骨整合能力,并可诱导软骨、肌腱修复再生。目前因多孔钽制备条件苛刻、成本较高等因素,限制了其临床广泛应用;新的制备方法及表面修饰技术的发展,为拓展多孔钽的应用范围,优化其骨组织修复再生能力提供了新的路径。结论多孔钽在修复骨缺损方面具有独特优势,但仍需在材料制备及表面修饰方面有进一步突破。     

多孔钽在口腔临床中的应用与发展

半个世纪以来,钛金属作为主流骨植入材料广泛应用于临床,其力学强度优异,可满足生物安全性,但仍存在弹性模量与人体骨不匹配及易生理腐蚀的不足。国内外学者一直在寻找更为理想的生物材料,多孔钽应运而生。生物医用多孔钽突出的抗腐蚀性能,较高的延展性,极佳的生物相容性与功能性较钛金属显示出更强大的优势,引起了众多学者的关注与研究。本文就多孔钽的物理、化学、生物特性及现阶段在口腔临床中的应用与发展进行综述。     

多孔钽材料细胞毒性、生物相容性及体内成骨性研究

 目的 探讨国产多孔钽材料的细胞毒性和生物相容性,并通过兔骨内植入成骨示踪观察其成骨作用。方法 扫描电镜观察并测量多孔钽的形态学特征。来源于新西兰胎兔颅盖骨的成骨细胞以多孔钽浸提液（实验组）及完全培养基（对照组）培养,MTT法检测多孔钽的细胞毒性及其对增殖的影响。成骨细胞与多孔钽体外复合培养,观察成骨细胞的黏附、生长及增殖。雄性新西兰大白兔24只,制备股骨髁上多孔钽棒植入模型;4只动物于术后第5天和第19天分别肌肉注射荧光素钙黄绿素和茜素红,术后10 周取材,于488 nm（钙黄绿素激发光）和543 nm（茜素红激发光）波长处,激光扫描共聚焦显微镜观察多孔钽-骨界面成骨;20只动物于术后2、4、8和12 周取材行大体及硬组织切片观察。结果 多孔钽表面及断面可见均匀分布的三维立体连通孔隙结构。MTT法检测显示实验组与对照组细胞随培养时间的延长,其OD值的差异均无统计学意义。扫描电镜显示复合培养早期,细胞在多孔支架表面和孔壁上黏附,相互连接;晚期汇合成片并分泌细胞外基质覆盖材料表面。体内成骨实验显示植入的多孔钽棒与宿主骨结合紧密。硬组织切片显示术后2、4周时多孔钽-骨界面已出现新生骨及小血管,并向孔隙内生长;8、12周时多孔钽表面和孔隙内已长满新生骨组织,新生骨小梁已发育成熟并与材料直接接触。激光共聚焦扫描显微镜显示多孔钽-骨界面及孔隙内可见绿色荧光（钙黄绿素）和红色荧光（茜素红）标记的新生骨组织,红色荧光带位于绿色荧光带周围,早期均呈不连续性,晚期则融为一体。结论 国产多孔钽材料无细胞毒性,具有良好的生物相容性,多孔钽-骨界面为接触及传导性成骨并呈时间依赖性。     

多孔钽金属棒在早期股骨头缺血性坏死中的应用

多孔钽金属棒为最新采用的用于治疗早期股骨头缺血性坏死的一种方法.由于其兼具人体松质骨结构和力学支撑特性,与传统的股骨头髓芯减压结合替代多种骨移植取得了较好的早期临床效果.本文重点介绍了钽金属棒的材料特性和结构特点,应用钽金属棒的手术要点、临床效果及存在的问题.     

多孔钽理化/生物学特性及其在脊柱外科的应用进展

目的综述多孔钽制造工艺、理化性质、生物学特性及其在脊柱外科中的应用进展。方法查阅国内外关于多孔钽材料相关文献,并进行总结、分析。结果多孔钽具有高孔隙率、高表面摩擦系数、低弹性模量的特点,以及良好的生物相容性及骨整合能力,其制作方法主要有化学气相沉积/渗透技术、泡沫浸渍和粉末冶金技术以及热处理方法。多孔钽椎间融合器已应用于颈、腰椎融合术,但在颈椎融合率问题上仍存在较大争议。通过表面修饰可增加多孔钽骨整合能力,提高椎间融合率。结论多孔钽椎间融合器用于腰椎手术中疗效确切,而在颈椎手术中仍存在争议,有待扩大样本量、延长随访时间进一步观察。     

胶原膜/国产多孔钽金属双相支架修复山羊大面积骨软骨缺损的实验研究

背景:骨软骨联合病变是骨科常见疾病,一直缺乏有效的治疗手段。目的:通过使用胶原膜联合自主研发的三维多孔钽金属支架,设计构建了一种新型的仿生骨组织工程复合体,并探讨其修复山羊大面积骨软骨缺损的效果。方法:将多孔碳化硅支架通过化学气相沉积技术制备成多孔钽金属,然后采用纤维蛋白黏合剂将胶原膜及自主研发的多孔钽金属进行界面结合,得到双相支架材料;在体外通过扫描电镜观察胶原膜及多孔钽的微观形貌,并通过能谱分析测定其组成成分;万能力学测试机进行双相支架材料的力学检测。32只雄性山羊采用随机数字表法分为4组,每组各8只,于左后肢建立骨软骨缺损模型(缺损面积直径为10 mm,深度为12 mm)。单纯骨软骨缺损组不做任何治疗,其余3组分别采用单纯胶原膜、单纯国产多孔钽金属、胶原膜/国产多孔钽金属双相支架修复。植入16周后进行大体观察及硬组织切片、染色,并进行定量分析。结果:扫描电镜观察结果表明,双相支架结合面均匀、光滑、牢固。能谱分析表明,胶原膜由碳、氧、钙3种元素组成,国内多孔钽金属主要由碳、硅和钽组成。该支架具有良好的抗压强度、抗拉强度、粘结强度和抗剪强度。植入山羊负重区大面积骨软骨缺损区16周后,国际软骨修复学会评分(ICRS)及改良O'Driscoll组织学评分结果显示,与单纯多孔钽金属组、单纯胶原膜组及单纯骨软骨缺损组相比,胶原膜/国产多孔钽金属双相支架组具有明显的骨软骨修复效果(P<0.05)。结论:本研究对于在负重区的大面积骨软骨缺损的成功修复显示了临床转化的潜能。为大面积骨软骨联合病变的临床治疗提供新的组织工程思路。     

多孔钽棒植入股骨头塌陷风险与生物力学支撑效果分析

目的对研究钽棒植入手术的适宜力学参数进行细化分析,为临床应用提供科学依据。方法利用CT扫描数据建立了包含钽棒-骨质接触面的有限元分析模型,其中钽棒和股骨头坏死区采用理想弹塑性材料模拟,采用通用有限元分析软件ANSYS对多孔钽棒植入后的股骨头塌陷量进行求解。结果当坏死区域角≥120°时股骨头产生显著局部塌陷,且钽棒植入体滑移微动量增大使钽棒支撑失效。结论股骨头坏死区域过大时不宜采用钽棒植入术。     

多孔钽骨科临床应用概况

多孔钽植入物极好的生物相容性及与松质骨类似的微观结构,业已引起生物医学界的广泛关注。骨科临床应用多孔钽于股骨头坏死、全髋关节置换、全膝关节置换、椎间融合的短期疗效令人鼓舞。该文就多孔钽在骨科的临床应用作一简要综述。     

多孔钽骨科临床应用概况

多孔钽植入物极好的生物相容性及与松质骨类似的微观结构，业已引起生物医学界的广泛关注。骨科临床应用多孔钽于股骨头坏死、全髋关节置换、全膝关节置换、椎间融合的短期疗效令人鼓舞。该文就多孔钽在骨科的临床应用作一简要综述。     

Bone ingrowth characteristics of porous tantalum and carbon fiber interbody devices: an experimental study in pigs.

BACKGROUND CONTEXT: In preclinical and clinical joint replacement applications, porous tantalum has been shown to be osteoconductive and effective for biological fixation. Relatively little research has been undertaken to investigate the porous tantalum implants for potential application in intervertebral spinal fusion. PURPOSE: The current study was designed to assess the radiographic and histological performance of porous tantalum and carbon fiber devices in the porcine anterior lumbar interbody fusion (ALIF) model. STUDY DESIGN: A total of 10 Danish Landrace pigs underwent a three-level anterior intervertebral lumbar arthrodeses at L2-L3, L4-L5 and L6-L7. Each level was randomly allocated to one of three implants: a solid piece of porous tantalum, a porous tantalum ring packed with autograft or a carbon fiber cage, likewise packed with autograft. Two staples for fixation were supplemented in front of implant. METHODS: Pigs were sacrificed 3 months after operation. Specimens were evaluated by plain radiography, conventional tomography and histology. RESULTS: Bone graft filled into the central hole of the porous tantalum ring was less than that of the carbon fiber cage (p<.001). Radiolucencies around the porous tantalum solid were significantly higher than the carbon fiber cage (p=.02) and were not different between the porous tantalum ring and the carbon fiber cage. The bone volume in the hole of implants, within the pores of the porous tantalum and in the implant interface did not differ between implants. Bone volume in the hole of the porous tantalum ring did not differ from that of the adjacent vertebral bone; however, it was significantly different in the carbon fiber cage and the adjacent vertebral bone (p=.005). CONCLUSIONS: In this porcine ALIF model, the radiographic and histological appearances of the porous tantalum ring were equivalent to those of the carbon fiber cage. The high presence of radiolucencies and fibrous tissue layer at the vertebrae-implant interface suggests that an initial stabilizing biomechanical environment is important in order to achieve bone ingrowth in the interbody fusion devices in this ALIF model.     

Mechanisms of failure of total hip replacements: lessons learned from retrieval studies

The value of implant retrieval analysis in orthopaedic surgery has been well recognized. Prosthetic devices retrieved for cause at revision surgery (for implant failure) or devices retrieved postmortem from patients with clinically successful reconstructions provide a unique set of specimens that can be studied to evaluate the effect of the implant on the host environment and the effect of the host environment on the implant. A systematic analysis of retrieved components, in combination with histologic, radiographic, and clinical data can provide valuable insights into the mechanisms of failure of the biomaterials used in joint replacement applications. From the hip implant retrieval studies reported to date, it has been established that the local reaction to particulate wear debris initiates the formation of a granulomatous tissue that ultimately invades the bone-implant interface and results in aseptic loosening. Cement mantle defects, noncircumferential porous coatings, and screw holes can serve as preferential access pathways for the progression of this granulomatous process yielding distinctive patterns of implant loosening and osteolysis. Continued surveillance of retrieved devices is strongly recommended to deepen our understanding of implant failure mechanisms and to evaluate the impact of newer designs and materials on the performance of joint replacement devices.     

A new mode of clinical failure of porous tantalum rod

The area of osteonecrosis of the head of femur affected by the disease process varies from a small localized lesion to a global lesion. Without specific treatment 80% of the clinically diagnosed cases will progress, and most will eventually require arthroplasty. Therefore the goal is to diagnose and treat the condition in the earliest stage. A number of surgical procedures have been described to retard or prevent progression of the disease and to preserve the femoral head. An implant made of porous tantalum has been developed to function as a structural graft to provide mechanical support to the subchondral plate of the necrotic femoral head, and possibly allow bone growth into the avascular region. Porous tantalum implant failure with associated radiological progression of the disease is reported in the literature; however, there is no report of clinical failure of the implant without radiological progression of the disease. We report a case of clinical failure of porous tantalum implant, seven months after surgery without any radiological progression of the disease, and with histopathological evidence of new bone formation around the porous tantalum implant. The patient was succesfully treated by total hip arthroplasty.     

Is anterior cervical fusion with a porous tantalum implant a cost-effective method to treat cervical disc disease with radiculopathy?

STUDY DESIGN.: Retrospective cost-effectiveness analysis. OBJECTIVE.: To determine the relative cost-effectiveness of anterior cervical discectomy with fusion (ACDF) using a porous tantalum implant compared with autograft with plating, for single-level cervical disc disease with radiculopathy. SUMMARY OF BACKGROUND DATA.: ACDF with autograft as an interbody spacer is a generally accepted method to treat degenerated cervical discs with radiculopathy. Concerns about donor site morbidity and the structural characteristics of autograft stimulated investigations of alternative materials. Techniques may differ in their operative risks, complications, outcomes, and resource use. METHODS.: A retrospective review of clinical outcomes and total cost of illness for 5 years postsurgery was performed for 61 consecutive patients enrolled for this study. Twenty-eight patients were treated with single-level ACDF using either a stand-alone, porous tantalum implant, without graft inside the implant, and 33 patients received autograft and plating. A cost-effectiveness analysis comparing the 2 ACDF treatment methods was conducted. This article reports clinical assessments, quality adjusted life years gained, and an incremental cost-effectiveness ratio analysis. RESULTS.: Patients in both cohorts reported improved clinical outcomes, including neck disability index, visual analogue scale, Short-Form 36, Odom's clinical assessment, and patient satisfaction at 5 years postindex surgery. The mean cost of illness for the study period, including preoperative through 5 years postoperative assessments, was 6806 per patient treated with tantalum and 10,143 per patient receiving autograft and plate. Quality-adjusted life years (QALY) gained were 9.41 and 7.14 for the tantalum and control cohorts, respectively. The cost per QALY for the tantalum group was 723 and 1420 for the control group. The incremental cost-effectiveness ratio of ACDF with a porous tantalum implant compared with ACDF with autograft and plate was -1473 per patient per year for the duration of this study. CONCLUSION.: This cost-effectiveness analysis reports favorable results for ACDF procedures utilizing a tantalum implant. The data reported suggest that using porous tantalum as a stand-alone device is less costly and more effective than autograft and plate in ACDF procedures.     

Biocompatible Porous Tantalum Metal Plates in the Treatment of Tibial Fracture

Fractures of the tibia represent a common class of injuries in orthopedics. The blood supply to the tibia is poor due to the small subcutaneous muscle tissues inside. Consequently, the tibia is prone to delayed fracture healing and nonunion of the fracture after surgery. In this case, we used porous tantalum metal plate to treat nonunion of a tibial fracture and achieved satisfactory therapeutic effects. For the first time in the field, we used 3D printing technology to fabricate porous tantalum metal plates for the treatment of tibial fractures. The resulting porous tantalum metal exhibited excellent mechanical and biological properties, and improved the therapeutic effects for the treatment of a tibial fracture nonunion. Porous tantalum metal plates have great application potential as a new implant material for internal fixation.     

Mechanical Stability of Novel Highly Porous Metal Acetabular Components in Revision Total Hip Arthroplasty

Highly porous metal acetabular components have emerged for revision hip arthroplasty. However, superior mechanical stability over traditional cementless components has not been demonstrated. Three different cementless acetabular components, including 2 highly porous tantalum designs, were inserted into hemipelvis specimens with a superolateral defect. Mechanical testing was performed to failure using a servohydraulic testing machine. The porous tantalum designs exhibited superior stability over the traditional cementless implant (P < .05). There was no difference in mechanical stability between the rigid modular tantalum shell and the more flexible revision tantalum shell (P > .46). In acetabular revision, highly porous tantalum acetabular components provide superior mechanical stability. However, these results suggest that improved frictional resistance is a more important design feature over implant flexibility with this particular implant.     

Canine carpal joint fusion: a model for four-corner arthrodesis using a porous tantalum implant

PURPOSE: Interest has focused on porous materials that promote bony ingrowth. In this study a porous tantalum implant was used as an adjunct to intercarpal stabilization in a canine model of wrist arthrodesis. METHODS: A defect was created at the junction of the radiocarpal, ulnocarpal, and fourth carpal bones, analogous to a four-corner fusion site in humans. A tantalum cylinder was press-fit and stabilized with K-wires. Controls were represented by creating the defect without implant placement. Animals were killed at 4, 8, and 12 weeks. RESULTS: Histology showed bony ingrowth as early as 4 weeks and mechanical testing showed a statistically significant increase in strength of the construct over time. Controls failed to achieve union at any time point. CONCLUSIONS: The implant served as an adjunct to stabilization of the carpus in this model of four-corner fusion, suggesting a novel application of this material in conditions in which bone graft has been required previously. This study represents a preliminary investigation of the use of a tantalum device for intercarpal stabilization; it does not compare this technique with conventional methods.     

Trabecular metal endoprosthetic limb salvage reconstruction of the lower limb

Currently, porous tantalum (trabecular metal) implants are widely accepted and frequently used for primary and revision hip and knee replacement surgery. This study examines the results of porous tantalum endoprostheses used to reconstruct large skeletal defects following resection of bone tumors. Seven custom tantalum implants were used to reconstruct 7 patients following resection for skeletal sarcomas in the femur and proximal tibia. Patient ages ranged from 13 to 71, with a mean of 34 years. Minimum patient follow-up was 6 years. The average Musculoskeletal Tumor Society functional evaluation score was 95 % of normal. There were no infections, hardware failures, or adverse events. One implant was revised 98 months post insertion because of fibrosis, loss of motion and loosening. In this small clinical series, the use of porous tantalum for limb salvage reconstruction is shown to be safe, to successfully provide osteointegration and soft tissue ingrowth, and to facilitate return of limb girdle muscle function.     

Clinical applications of Trabecular Metal

Trabecular Metal (porous tantalum) offers a viable solution to several challenges in orthopedic reconstructive surgery, including monoblock acetabular cups, avascular necrosis intervention devices, and total hip reconstruction in situations of massive femoral bone loss. Porous tantalum approaches the ideal biomaterial: it is porous, strong, flexible, and biocompatible. For use in components for total hip arthroplasty, porous tantalum provides a substitute for lost bone, immediate bone loading, bone ingrowth, and soft-tissue attachment. It can be machine-shaped into custom designs in situations of massive bone loss.     

Short-term alendronate treatment does not maintain a residual effect on spinal fusion with interbody devices and bone graft after treatment withdrawal: an experimental study on spinal fusion in pigs

Purpose

Whether alendronate treatment has a residual effect on bone ingrowth into porous biomaterial in humans or experimental animals after treatment withdrawal is still unknown. The purpose of this study was to investigate bone ingrowth into porous tantalum and carbon fiber interbody implants after discontinuing alendronate treatment in experimental spinal fusion in pigs.

Methods

Twenty-four pigs were randomly divided into two groups of each 12 pigs. The pigs underwent anterior intervertebral lumbar arthrodeses at L2–3, L4–5 and L6–7. Each level was randomly allocated to one of the three implants: a porous tantalum ring with pedicle screw fixation, a porous tantalum ring or a carbon fiber cage with anterior staple fixation. The central hole of implants was packed with an autograft. Alendronate was given orally for the first 3 months to one of the two groups. The pigs were observed for 6 months postoperatively. Histology and micro-CT scans were done at the endpoint.

Results

The spinal fusion rates of each implant showed no differences between two treatment groups. Furthermore, no differences were found between two groups as for bone ingrowth into the central holes of implants and bone–implant interface in each implant, or as for the pores of tantalum implants. Trabecular bone microarchitecture in the central hole of the carbon fiber cage did not differ between two treatment groups.

Conclusion

The application of ALN, with a dose equivalent to that given to humans during the first 3 months after surgery, does not maintain a residual effect on spinal fusion with porous tantalum ring and autograft after treatment withdrawal in a porcine ALIF model.