Specific features of bone tissue regeneration after replacement of the defect with a synthetic implant

A synthetic implant is constructed on the basis of a biopolymer (collagen) with inorganic salts (hydroxysulfates and hydroxyphosphates of Ca, Mg, and Al) introduced into the collagen in different ways. Regeneration is monitored by roentgenophase, differential thermal, and chemical analyses, computerized tomography, and by x-ray and morphological methods. It is shown that the composition of the salt component and the salt:collagen ratio do not significantly affect the regeneration. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, No 4, pp. 435–438, April, 1995     

Repair of long intercalated rib defects in dogs using recombinant human bone morphogenetic protein-2 delivered by a synthetic polymer and beta-tricalcium phosphate

Long intercalated defects in canine ribs can be repaired successfully using porous beta-tricalcium phosphate (beta-TCP) cylinders, infused with a biodegradable polymer (poly D,L-lactic acid-polyethylene block copolymer) containing recombinant human bone morphogenetic protein-2 (rhBMP-2). We previously reported the successful regeneration of bony rib and periosteum defects using beta-TCP cylinders containing 400 microg of rhBMP-2. To reduce the amount of rhBMP-2 and decrease the time required for defect repair, we utilized a biodegradable polymer carrier, in combination with rhBMP-2 and the porous beta-TCP cylinders. An 8 cm long section of rib bone was removed and replaced with an implant comprised of the porous beta-TCP cylinders and the polymer containing 80 microg of rhBMP-2. Six weeks after surgical placement of the beta-TCP cylinder/polymer/BMP-2 implants, new rib bone with an anatomical configuration and mechanical strength similar to the original bone was regenerated at the defect site. The stiffness of the regenerated ribs at 3, 6, and 12 weeks after implantation of the composite implant was significantly higher than that of ribs regenerated by implantation of rhBMP-2/beta-TCP implants. Thus, addition of the synthetic polymer to the drug delivery system for BMP potentiated the bone-regenerating ability of the implant and enabled the formation of mechanically competent rib bone. This new method appears to be applicable to the repair of intercalated long bone defects often encountered in clinical practice.     

长骨节段性缺损修复重建的理论及应用进展

背景：长骨节段性骨缺损修复重建方法众多,各有优缺点,限制了其广泛应用,仍是一个未完美解决的骨科难题。 目的：综述近年国内外长骨节段性缺损的修复重建进展研究。 方法：第一作者应用计算机检索1990年1月至2012年12月PubMed数据库、中国期刊全文数据库、维普数据库有关长骨节段性缺损修复重建的文章,英文检索词“bone defect, long bone reconstruction, tissue engineering of bone,scaffolds,bone reconstruction,bone graft,bone tumor; tumor resection,musculoskeletal tumors,regeneration,autografts”;中文检索词“大段,骨缺损,骨肿瘤,软组织肿瘤,瘤段切除,组织工程,骨移植”。共检索到104篇相关文献,纳入52篇文献进一步研究。 结果与结论：传统长骨节段性骨缺损的修复方法包括自体骨移植、异体骨移植、骨延长、人工假体置换等。研制适用于儿童保肢需要,符合儿童生长发育特点的假体成为儿童保肢的一个挑战课题。为了解决这一问题,人们研制出可以不断延长的假体,用于儿童骨肿瘤的保肢重建。随着医疗技术的进步,各种人工骨,尤其是骨组织工程和基因治疗在骨缺损修复中的逐步应用将进一步提高骨缺损的修复效果,是未来的研究方向。     

Repair of segmental long bone defect in rabbit femur using bioactive titanium cylindrical mesh cage

A segmental rabbit femur defect was repaired using an empty bioactive titanium (BAT) mesh cage. A 10mm long titanium mesh cage was positioned in the bony defect and reinforced by intramedullary fixation. The BAT surface was prepared by chemical and thermal treatment. Pure titanium cages were used as a control. Torsional stiffness of the BAT group at 4 weeks was approximately equal to, and at 8 weeks twice, that of the intact femur. Differences between the torsional stiffness of the control and BAT groups were significant at both time intervals. Histological examinations showed that woven bone appeared around the cage by 4 weeks and transformed to lamella bone by 8 weeks. New bone bonded to the BAT surface without an intervening layer. The BAT cage enhanced the bone repairing process and achieved faster repair of long bone segmental defects.     

A synthetic bone implant macroscopically identical to cancellous bone

Macroporous hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) are widely used as synthetic bone replacement materials due to their high biocompatibility and osteoconductive properties. The level of porosity, pore size distribution, pore morphology, and the degree of pore interconnectivity in such grafts significantly influences the extent of bone ingrowth. It has been hypothesised that an ideal implant macrostructure may be similar in morphological characteristics to the inorganic matrix of the bone it is replacing. However, to date, clinically available synthetic materials differ structurally from cancellous bone.

A method is described for the macrostructural replication of cancellous bone. Reproduction involves a multistage process requiring the manipulation of positive and negative forms of the inorganic matrix. By infiltration of a wax negative mould of cancellous bone with a ceramic slip, followed by removal of the wax, and firing, it is possible to produce a positive replica of the original cancellous macrostructure.

Optimisation of slip preparation conditions (pH and percentage deflocculant addition) and sintering conditions have allowed successful replication of cancellous bone using several bioceramic compositions including HA, β-TCP, and HA/β-TCP.     

Intramembranous bone tissue response to biodegradable octacalcium phosphate implant

Previous studies showed that synthetic octacalcium phosphate (OCP) enhances bone formation coupled with its own osteoclastic biodegradation more than non-biodegradable hydroxyapatite (HA), including sintered HA ceramic, when implanted in animal bone defects. The present study was designed to investigate whether synthetic OCP in granule form has biodegradable characteristics when implanted in the subperiosteal area of mouse calvaria in comparison with non-sintered stoichiometric HA, especially in relatively short periods after implantation. OCP crystals exhibited plate-like morphology, whereas HA crystals had a sphere-like structure. Both crystals had large pore volumes >75% in total, with micropores within the granules. Direct bonding of newly formed bone was discernible in HA until 35 days after implantation by element analysis for calcium and phosphorus. However, histomorphometric analysis demonstrated that bone formation was facilitated on OCP surfaces with greater alkaline phosphatase activity than on HA up to 21 days. The surfaces attacked by tartrate-resistant acid phosphatase positive osteoclast-like cells were significantly greater than those of HA. OCP became encapsulated and replaced with new bone with prolonged implantation periods up to 180 days. The results suggest that the enhanced bone formation in mouse calvaria could be associated with the biodegradable nature of OCP, and that OCP could be used in augmenting intramembranous bone volume.     

川续断复合磷酸钙骨修复骨缺损

背景：复合磷酸钙骨植入材料的物理结构和无机成分与人体骨相似,具有良好的生物可吸收性和生物相容性。研究证实续断细粉能明显提高骨缺损修复速度。 目的：观察川续断复合磷酸钙骨复合植入材料修复骨缺损的效果。 方法：在新西兰大白兔双侧下颌骨体部制备长约1.0 cm、宽约0.5 cm、深约0.3 cm的骨缺损,右侧植入川续断复合磷酸钙材料作为实验组,左侧植入磷酸钙骨材料作为对照组。植入后4,8,12周取材,进行大体观察、CBCT检测、扫描电镜、组织学观察。 结果与结论：①大体观察：实验组成骨速度、材料降解率及硬度高于对照组。②CBCT检测：实验组材料与周围组织结合紧密度强于对照组,且材料降解速度快于对照组。③扫描电镜：两组材料与周围正常骨组织间大多由纤维结缔组织充盈,实验组比对照组更为紧密,空隙更加微小,随着时间的增加,材料与周围正常骨组织的结合更为紧密。④组织学观察：实验组成骨速度及成骨活性优于对照组。表明川续断复合磷酸钙骨植入材料具有明显加速成骨的作用。     

Repair of long intercalated rib defects using porous beta-tricalcium phosphate cylinders containing recombinant human bone morphogenetic protein-2 in dogs

A new method to repair rib defects with biomaterials containing recombinant human bone morphogenetic protein-2 (rhBMP-2) is presented in this report. We had reported previously the successful regeneration of bony rib defects by placing a short chain of small beta-tricalcium phosphate (beta-TCP) cylinders on the intact periosteum. The multi-cylinder implants were ineffective in promoting rib repair when the periosteum was absent. By adding rhBMP-2 to the beta-TCP cylinders, we were able to promote rib bone regeneration in the presence or absence of the periosteum. The osteogenic capacity of the rhBMP-2/beta-TCP composite implant and the time required to complete regeneration were evaluated in a canine model. An 8cm long section of rib bone, including the periosteum, was removed and replaced with a chain of the rhBMP-2/beta-TCP cylinders. At 6 weeks after implantation, the ribs were restored to their original configuration and mechanical strength. The multi-cylinder beta-TCP implants were degraded and replaced by new bone in 12 weeks. This new degradable bone-inducing implant material has significant clinical potential for rib repair.     

Repair of a proximal femoral bone defect in dogs using a porous surfaced prosthesis in combination with recombinant BMP-2 and a synthetic polymer carrier

Total hip arthroplasty (THA) has become an almost standard procedure for the treatment of various hip lesions. However, one of the limitations has been the mechanical loosening of the prosthesis, a condition termed peri-prosthetic osteolysis. Consequently, at revision surgery, various grades of bone defect are often noted. Alternative approaches aimed at overcoming this problem have included a special design of the revision prosthesis and allo- or autogeneic bone grafting in combination with or without biomaterials. In a further attempt to address the loosening of the prosthesis, we have combined human bone morphogenetic protein-2, produced by DNA recombination (rhBMP-2) with a new synthetic biodegradable polymer (poly-D,L-lactic-acid-para-dioxanone-polyethyleneglycol block co-polymer; PLA-DX-PEG). We present data on the efficacy of the rhBMP-2 laden prosthesis to reconstruct a bone defect in a canine model. In this model, medial half of the proximal femur was surgically resected to create a bone defect that was repaired with the rhBMP-2/PLA-DX-PEG composite. Twelve weeks after implantation, the original bone defects in the rhBMP-2 treatment groups had been repaired. Thus, this type of 'hybrid' prosthesis may provide a new modality to repair bone defects or restore lost bone mass encountered in revision arthroplasty.     

Enhanced bone regeneration at a segmental bone defect by controlled release of bone morphogenetic protein-2 from a biodegradable hydrogel

The objective of this study is to investigate the feasibility of a biodegradable hydrogel of gelatin as the controlled release carrier of bone morphogenetic protein-2 (BMP-2) suitable for enhancement of bone regeneration at a segmental bone defect. Hydrogels with three different water contents were prepared through glutaraldehyde crosslinking of gelatin with an isoelectric point of 9.0 under varied reaction conditions. Segmental critical-sized defects (20 mm) were created at the ulnar bone of skeletally mature New Zealand white rabbits, and gelatin hydrogels incorporating BMP-2 (17 microg/hydrogel) were implanted into the defects. When bone regeneration was evaluated by soft x-ray observation and bone mineral density (BMD) measurement, the gelatin hydrogels incorporating BMP- 2 exhibited significantly high osteoinduction activity compared with that of free BMP-2, although the activity depended on the water content of the hydrogels. Significantly higher BMD enhancement was observed in the gelatin hydrogel with a water content of 97.8 wt% than that with the lower or higher water content. We concluded that the biodegradable gelatin hydrogel is a promising controlled release carrier of BMP-2 for bone regeneration at the segmental bone defect.     

去抗原异种松质骨复合骨髓基质干细胞修复骨缺损

目的研制理想的能够修复骨缺损的骨材料,为其在骨缺损修复领域中的临床应用提供实验依据。方法体外扩增诱导兔骨髓基质干细胞,将其与去抗原异种松质骨复合培养。造成兔桡骨中段10mm骨缺损模型,分复合细胞组、单纯材料组、空白对照组。通过大体观察、放射学检查、组织学检查观察骨缺损的修复情况。结果去抗原异种松质骨复合骨髓基质干细胞修复兔桡骨缺损,12周时缺损区完全被新骨代替,骨髓腔完全通畅,优于单纯材料组的修复效果,单纯材料组优于空白对照组。结论去抗原异种松质骨具有良好的成骨能力,有可能成为理想的骨支架材料。     

带血管蒂腓骨移植治疗长骨骨髓炎并骨缺损

目的探讨带血管蒂腓骨移植治疗长骨骨髓炎并骨缺损的临床应用及体会。方法采用带血管蒂腓骨移植治疗大段骨缺损并慢性骨髓炎患者11例,其中肱骨6例,胫骨5例。结果 11例患者术后6~12个月回访功能恢复良好,移植骨与受体愈合,无感染,骨不愈合等发生。结论采用带血管蒂腓骨瓣移植修复是临床治疗长骨骨髓炎并骨缺损缺损的较好方法。     

钛网打压植骨重建四肢长骨节段骨缺损☆

背景：四肢长骨节段骨缺损临床上常见,一直以来是骨科修复领域的难题。 目的：介绍钛网打压植骨重建四肢长骨节段骨缺损新方法的实验研究和临床用用。 方法：第一作者应用计算机检索1990至2011年 PubMed数据库(http://www.ncbi.nlm.nih.gov/PubMed), CNKI 数据库(www.cnki.net/index.htm), 和维普数据库(http//www.cqvip.com)有关钛网打压植骨重建四肢长骨节段骨缺方面的文献,英文检索词为“segmental bone defect,titanium mesh or titanium cage”;中文检索词为“四肢或长骨,骨缺损,钛网”。排除重复性研究、非四肢长骨和Meta分析类文献。根据纳入标准,共检索到30篇文献进行归纳总结。 结果与结论：钛网打压植骨重建四肢长骨节段骨缺损无论在大动物或是小动物的实验中均取得较好的成骨效果,优于非钛网的游离植骨和大块皮质骨游离植骨;自体骨、异体骨和人工骨均是可行的填充植骨材料,以自体松质骨为主的植骨材料的成骨效果相对较好,具有生物活性钛网较普通钛网的成骨效果更好。临床上,在四肢长骨各个部位的节段骨缺损中均取得很好的治疗效果,包括骨缺损长达十余厘米的病例。钛网打压植骨重建四肢长骨节段骨缺损新方法,改变了以往认为大于 6 cm以上长段骨缺损只适宜带血运的骨移植、而不适宜无血运游离植骨的传统观点。该方法较简单、安全、有效,是一种较理想的替代治疗长骨骨干部节段骨缺损的无血运游离植骨法。     

New synthetic biodegradable polymers as BMP carriers for bone tissue engineering

Bone morphogenetic proteins (BMPs) are biologically active molecules capable of inducing new bone formation and are expected to be used clinically in combination with biomaterials such as bone-graft substitutes to promote bone repair. The carrier materials for BMPs have to not only secure the BMPs in the local area and diffuse them afterwards, but also to provide scaffolding for the newly formed bone. Since synthetic, biodegradable polymers with optimal properties are considered most desirable, we synthesized polylactic acid and its derivatives. Some of these were found to consistently induce ectopic bone formation when combined with BMP and implanted into the muscles of experimental animals. It was also found that the three-dimensional configuration of BMP-induced bone mass could be controlled. This means that our attempt to construct synthetic biomaterials which can induce controllable bone formation was successful.     

Repair of 20-mm long rabbit radial bone defects using BMP-derived peptide combined with an alpha-tricalcium phosphate scaffold

In previous studies, we have reported that the BMP-2-derived peptide KIPKASSVPTELSAISTLYL, corresponding to BMP-2 residues 73-92, binds to a BMP-2-specific receptor, and elevates both alkaline phosphatase activity and osteocalcin mRNA in the murine mesenchymal cell line, C3H10T1/2. This 73-92 peptide conjugated to a covalently crosslinked alginate gel induced ectopic bone formation in rat calf muscle, and activated osteoblasts to promote the repair of rat tibial bone defects. Here, we report repair of 20-mm long rabbit radial bone defects using the 73-92 peptide combined with a porous alpha-tricalcium phosphate (TCP) scaffold. In vitro, the 73-92 peptide was released from the porous alpha-TCP scaffold over more than one week. In vivo, radiomorphometric analysis showed that the 73-92 peptide combined with the porous alpha-TCP scaffold promoted calcification in the implanted area in a dose-dependent manner, and that 5 mg of the 73-92 peptide induced connection of 20-mm long defects, defects of critical size, 12 weeks after implantation. Histological examination revealed newly formed bone and a marrow cavity in the implanted area. The area of bone denser than 690 mg/cm(3) induced by the 73-92 peptide was nearly equal to that of the contralateral radius.     

Quantitative screening of engineered implants in a long bone defect model in rabbits

We have standardized a long bone defect model in rabbits to quantitatively compare the bone healing performance of engineered biological implants and have tested the bone healing efficiency of porous cylindrical scaffolds (?-h, 6-20 mm [diameter 6 mm, height 20 mm] porosity, 70%) that were produced from hydroxyapatite (HA), titanium (Ti), and a novel biodegradable polymer-bioceramic composite (PH70alphaTCP). Scaffolds were perfused with or without 20 x 10(6) rabbit periosteal cells (RPCs) in a bioreactor and implanted in a standardized 2 cm defect in rabbit tibiae. X-rays revealed that new bone had formed at 3 weeks after creation of the defects. At sacrifice after 10 weeks, bone corticalization was observed in the majority of animals. Although PH70alphaTCP scaffolds did not inhibit callus formation, histomorphometric analysis revealed that there was no bone within the biomaterial, in contrast to HA and Ti scaffolds (bone volume ranging from 10% to 25%). We found that Ti and HA scaffold had good osteoconductive properties, but only HA scaffolds seeded with RPCs contributed to long bone mechanical functionality, with the maximum energy and angle being 308% and 155% greater than in control defects without scaffold.     

Bone formation in a long bone defect model using a platelet-rich plasma-loaded collagen scaffold

Platelet-rich plasma (PRP), a platelet concentrate made of autogenous blood, has been used in recent years to improve bone defect healing particularly in maxillofacial reconstructions. The aim of the present study was to assess the effect of PRP on new bone formation in a critical diaphyseal long bone defect. A critical size defect (2.5 cm) in the tibial diaphysis of 16 sheep was supplied either with autogenous PRP in a collagen carrier or with collagen alone (controls). Platelets were enriched about 3.5 fold compared to normal blood in the PRP. After 12 weeks, the explanted bone specimens were quantitatively assessed by X-ray, computed tomography (CT), biomechanical testing and histological evaluation. Bone volume, mineral density, mechanical rigidity and histology of the newly formed bone in the defect did not differ significantly between the PRP treated and the control group, and no effect of PRP upon bone formation was observed. It was suggested that PRP does not enhance new bone formation in a critical size defect with a low regenerative potential. Such bone defects might require more potent stimuli, e.g. combinations of functional biomaterials or autografts, precursor cells or osteoinductive growth factors.     

Assessment of the initial viscoelastic properties of a critical segmental long bone defect reconstructed with impaction bone grafting and intramedullary nailing

IntroductionThis study compared the initial viscoelastic properties of a segmental tibial defect stabilized with intramedullary nailing and impaction bone grafting to that of a transverse fracture stabilized with intramedullary nailing.Materials and methodsSeven sheep tibiae were tested in compression (1000 N), bending and torsion (6 Nm) in a six degree-of-freedom hexapod robot. Tests were repeated across three groups: intact tibia (Intact), transverse fracture stabilized by intramedullary nailing (Fracture), and segmental defect stabilized with a nail and impaction bone grafting (Defect). Repeated measures ANOVA on the effect of group on stiffness/phase angle were conducted for each loading direction.ResultsThe Intact group was significantly stiffer than the Fracture and Defect groups in bending and torsion (p < 0.022 for both loading directions), and was marginal for the Defect group in compression (p = 0.052). No significant differences were found between the Fracture and Defect groups (p > 0.246 for all loading directions) for stiffness/phase angle. In compression and bending, phase angles were significantly greater for the Fracture and Defect groups compared to Intact (p < 0.025), with no significant differences between groups in torsion (p = 0.13). Sensitivity analyses conducted between the Fracture and Defect group differences found that they were not of clinical significance.ConclusionThe initial properties of a segmental defect stabilized with intramedullary nailing and impaction bone grafting was not clinically significantly different to that of a transverse fracture stabilized with intramedullary nailing.     

New bone formation in a bone defect associated to dental implant using absorbable or non-absorbable membrane in a dog model

The aim of this research was to determine the bone formation capacity in fenestration defects associated with dental implants using absorbable and non-absorbable membranes. Six dogs were used in the study. In both tibias of each animal 3 implants were installed, and around these 5 mm circular defects were created. The defects were covered with absorbable membranes (experimental group 1), non-absorbable membranes (experimental group 2), and the third defect was not covered (control group). At 3 and 8 weeks post-surgery, the animals were euthanized and the membranes with the bone tissue around the implants were processed for histological analysis. The statistical analysis was conducted with Tukey’s test, considering statistical significance when p<0.1. Adequate bone repair was observed in the membrane-covered defects. At 3 weeks, organization of the tissue, bone formation from the periphery of the defect and the absence of inflammatory infiltrate were observed in both experimental groups, but the defect covered with absorbable membrane presented statistically greater bone formation. At 8 weeks, both membrane-covered defects showed adequate bone formation without significant differences, although they did in fact present differences with the control defect in both periods (p>0.1). In the defects without membrane, continuous connective tissue invasions and bone repair deficiency were observed. There were no significant differences in the characteristics and volume of the neoformed bone in the defects around the implants covered by the different membranes, whereas the control defects produced significantly less bone. The use of biological membranes contributes to bone formation in three-wall defects.     

骨干骨折压力侧皮质缺损钢板内固定的生物力学研究

目的 :评价压力侧骨皮质缺损时钢板内固定的即刻稳定程度 ,明确压力侧皮质骨块复位的重要性。方法 :6具新鲜股骨标本 ,于中段造成蝶形皮质缺损 ,测定正常股骨 ,单纯钢板内固定及对侧皮质骨块复位钢板内固定的垂直压缩、三点弯曲及抗扭转能力 ,比较不同固定方法在相同载荷下的位移。结果 :正常股骨在 5 0 0N垂直压力下的垂直位移 ,3 0 0N压力下的三点弯曲位移及 10N .m下的旋转角位移分别为 0 .82mm ,1.5 6mm和 0 .82° ,仅应用钢板于张力侧内固定后的三项位移分别为 8.2 9mm ,10 .5 9mm和9.11° ,应用钢板内固定对侧皮质骨块复位后分别为 1.78mm ,5 .15mm和 6.75° ,三项指标间均有非常显著性差异。结论 :当存在压力侧骨皮质缺损时 ,钢板固定骨块复位时的稳定性较单纯应用钢板内固定时好。应重视恢复钢板对侧皮质骨块的复位 ,恢复内侧的支撑力 ,以防止内固定的失败