Repair of calvarial defects in rats by prefabricated hydroxyapatite cement implants

The aim of the present study was to test the hypothesis that calvarial defects can be repaired by using preformed implants of calcium phosphate bone cement (CPBC) in rats. Sixty adult female Sprague-Dawley rats received full-thickness calvarial nonhealing defects with a diameter of 8 mm. Three different CPBCs were used: group 1: tetracalcium phosphate-based powder; group 2: a blend of amorphous and crystalline calcium phosphate precursors; and group 3: an alpha-tricalcium phosphate (alpha-TCP)-based powder. Implants were left to cure for 25-40 min at room temperature in a silicon mold of 7.9 mm and inserted press fit into the defects. Fifteen animals served as unfilled controls. After 13, 26, and 52 weeks, the material was analyzed qualitatively by using surface-stained undecalcified thick-section specimens and quantitatively by using semiautomated histometry. Kruskal-Wallis tests were applied to compare mean values of periimplant bone formation at a significance level of p < 0.05. Three implants of group 1 fractured during insertion. Resorption of CPBC without complementary bone formation was noticed in these implants. Unfractured implants were resorbed with simultaneous apposition of bone on the implant surface. After 52 weeks, the resorption rate varied between 23.1 and 39.3%. Periimplant bone formation increased continuously on average around all implant types, but it reached statistical significance only in group 2. The results showed that repair of calvarial defects can be achieved by preformed CPBC implants. The rate of resorption of preformed implants is, however, much lower than that reported for in vivo cured CPBC.     

The effect of calcium phosphate bone substitute on defect resolution around a rough-surfaced dental implants in dogs

Gap defects often exist around dental implants due to morphological differences between the natural tooth extraction socket and the dental implant. Techniques that can resolve such gap defects include implant surface modification and filling of the defects with bone substitutes. Modified surfaces are generally more effective in this regard than smooth surfaces. Favorable results have also been reported using bone substitutes. This study evaluated the effectiveness of a calcium phosphate (CaP) bone substitute for resolving gap defects around implant surfaces that have been treated with grit blasting and thermal etching. Implants were placed in edentulous areas in four mongrel dogs. Gap defects with a diameter of 2 mm were prepared surgically around the dental implants. These defects were either filled with CaP bone substitute (experimental group) or left unfilled (control group). Defects were evaluated after 8 and 16 weeks of healing. Block specimens were fixed, sectioned, and stained with hematoxylin and eosin. Histometric measurements revealed that healing in gap defects that had been filled with CaP bone substitute proceeded until 16 weeks. Total CaP degradation seemed to occur at between 4 and 8 weeks of healing. In conclusion, a more complete defect resolution was observed in gap defects filled with CaP bone substitute after 16 weeks than after 8 weeks of healing. The beneficial effects of filling in 2-mm gap defects around implants were attributed to the use of CaP bone substitute.     

Resorbable calcium phosphate particles as a carrier material for bone marrow in an ovine segmental defect

Resorbable calcium phosphate ceramics are only osteoconductive; therefore, their combination with osteogenic substances may lead to stimulation of bone healing. In the present study this combination, using autologous bone marrow, was investigated. In 31 sheep, a 3-cm tibial segmental defect was created and stabilized with an intramedullary nail. The animals were divided into four groups: empty defects (group 1, n = 7), and defects filled with 10-mL dense resorbable calcium phosphate particles (group 2, n = 8), with 10-mL particles soaked in bone marrow (group 3, n = 8), or with 10-mL autologous bone (group 4, n = 8). On evaluation after 12 weeks, significantly higher values were seen in group 3 than in group 2 for callus volume (p = .016), bone mineral density ratio (p = .03), bone mineral content ratio (p = .04), torsional strength (p = .005), and torsional stiffness (p = .01). For all end points, the outcome of group 3 was lower than that of group 4. In the histology, there was direct contact between newly formed bone and remnants of the particles. There were no signs of inflammatory reactions. Although a stimulatory effect of bone marrow was seen, the combination of resorbable calcium phosphate particles with bone marrow does not provide an alternative for autologous bone grafting.     

The effect of a fibrin-fibronectin/beta-tricalcium phosphate/recombinant human bone morphogenetic protein-2 system on bone formation in rat calvarial defects

In spite of good prospects for bone morphogenetic proteins (BMP) applications, an ideal carrier system for BMPs has not yet been identified. The purpose of this study was to evaluate the osteogenic effect of a fibrin-fibronectin sealing system (FFSS) combined with beta-tricalcium phosphate (beta-TCP) as a carrier system for recombinant human bone morphogenetic proteins (rhBMP-2) in the rat calvarial defect model. Eight-millimeter critical-size calvarial defects were created in 100 male Sprague-Dawley rats. The animals were divided into five groups of 20 animals each. The defects were treated with rhBMP-2/FFSS, rhBMP-2/FFSS/beta-TCP, FFSS and FFSS/beta-TCP carrier control or were left untreated as a sham-surgery control. Defects were evaluated by histologic and histometric parameters following a 2- and 8-week healing interval (10 animals/group/healing intervals). The FFSS/beta-TCP carrier group was significantly greater in new bone area at 2 weeks (p<0.05) and new tissue area at 2 and 8 weeks (p<0.01) relative to the FFSS carrier group. New bone and new tissue area in the rhBMP-2/FFSS/beta-TCP group were significantly greater than in the rhBMP-2/FFSS group at 8 weeks (p<0.01). On histologic observation, FFSS remnants were observed at 2 weeks, but by 8 weeks, the FFSS appeared to be completely resorbed. rhBMP-2 combined with FFSS/beta-TCP produced significantly more new bone and new tissue formation in this calvarial defect model. In conclusion, FFSS/beta-TCP may be considered as an available carrier for rhBMP-2.     

Bioactivity and osseointegration study of calcium phosphate ceramic of different chemical composition

Synthetic hydroxyapatite (HA) and tricalcium phosphate (TCP) are promising bone-substitute materials in the orthopaedic and dental fields, as their chemical composition is similar to that of bone. This study investigated the osseointegration performance of carbonated biphasic calcium phosphate (CBCP) ceramics containing carbonated hydroxyapatite and tricalcium phosphate prepared by microwave irradiation, in femoral defects of dogs. The defects were created as 3-mm holes on the lateral aspect of femur and filled with the implant material. The serum was collected postoperatively and biochemical assays for alkaline phosphatase activity levels were carried out. The animals' defective sites were radiographed at 4, 8, and 12 weeks. The radiographic results showed that the process of ossification started after 4 weeks and the defect was completely filled with new bone after 8 weeks. Histological examination of the tissue showed the osteoblastic activity inducing the osteogenesis in the defect. The complete haversian system with osteoblastic and osteoclastic activity and bone remodelling process were observed after 12 weeks. The alkaline phosphatase activity levels also correlated with the formation of osteoblast cells. This calcium phosphate ceramic has proved to work well as a biocompatible implant and as an osteoconductive and osteoinductive material for the filling of bone defects.     

Evaluation of bone regeneration at critical-sized calvarial defect by DBM/AM composite

This study investigated the bone-regenerative potential of a demineralized bone and acellular matrix (DBM/AM) composite (AlloCraft DBM) in comparison with autologous bone using an in vivo model. Critical-sized calvarial defects (5 mm) were created in athymic rats. The defects were grafted with either the DBM/AM composite or the acellular human dermal matrix (AM), and compared with the defects filled with autologous bone (positive control) and the empty defect (negative control). Histological and radiographic assessments were carried out at 4 and 8 weeks after surgery to determine the biological healing, the amount and type of new bone formation and the percentage of new bone filled in the critical defects. At 4 weeks, DBM/AM composite group had the highest percentage of the defect filled with new bone (84%), which was significantly greater than autologous bone (62%), AM (41%), and untreated control (32%) groups. At 8 weeks, the DBM/AM continued to have the highest percentage of the defect filled with new bone (91%). The autologous bone group increased the percentage of bone fill to 83%. The defects either filled with AM or left untreated still had less of the defect filled with new bone, 57% and 33%, respectively. The total healing of defects grafted with DBM/AM was comparable with autologous bone group at 8 weeks. The results demonstrated that the DBM/AM composite promoted new bone formation more rapidly than autologous bone at calvarial defect in athymic rats. The study supports that DBM/AM is a potential substitute of autologous bone for bone repair.     

医用硫酸钙与磷酸钙在创伤性骨缺损中应用的疗效观察

目的观察人工合成医用硫酸钙和磷酸钙在骨创伤中，作为骨替代物的临床疗效。方法对50例创伤骨折并存在骨缺损者，治疗除采用内固定（钢针、钢板）和外固定（石膏、外固定架）外，结合使用医用硫酸钙组24例，使用医用磷酸钙组26例。结果所有使用填充人工骨的病例，骨折均如期愈合，平均愈合时间11周（8～16周），使用硫酸钙者未出现任何异常反应和并发症，使用磷酸钙者有2例浅表渗出，经换药愈合。平均随访时间24周（16～50周），硫酸钙组平均吸收时间较磷酸钙组短约30周。结论医用硫酸钙和磷酸钙人工骨均可作为骨替代物应用，在辅助固定下具有安全，方便，副作用小以及填充效果确实，骨折愈合良好等优点。硫酸钙骨粉固化后较磷酸钙坚固，具有较强支撑作用。在内或外固定确实的情况下，二者均不失为治疗骨缺损的最佳选择。     

晶须化磷酸钙多孔生物活性陶瓷修复犬股骨髁缺损

BACKGROUND: Previous studies have demonstrated that the internal microstructure of porous calcium phosphate ceramics after the whiskering process has some changes, and obtain good mechanical properties. OBJECTIVE: To further investigate the effect of whisker-covered porous calcium phosphate ceramics in repair of canine femoral condyle defects. METHODS: Highly interconnected porous calcium phosphate ceramics was prepared by placeholder method. The whiskering of the materials was finished by hydrothermal process. Fifteen healthy adult beagle dogs were selected in this study. A 10 mm×10 mm cylindrical inclusive bone defect was made bilaterally on the lateral femoral condyle with a drill. The porous calcium phosphate ceramics after the whiskering process was implanted onto the right femoral condyle as experiment group. The porous calcium phosphate ceramics without the whiskering process was implanted onto the left femoral condyle as control group. At 2, 4, 8, and 12 weeks after implantation, X-ray and dual-energy X-ray test were conducted in the bone defect area respectively. RESULTS AND CONCLUSION: (1) X-ray: With the increase of time, the interface between bone defect and normal bone of two groups gradually blurred, disappeared, and completely fused at 12 weeks. The material in the control group was partially dissolved, while there was no obvious dissolution in the experiment group. No significant difference in the X-ray scores was found between two groups at different time points. (2) Dual-energy X-ray: With the increase of time, the bone mineral density of the two groups both increased gradually, but there was no significant difference in the bone mineral density at different time points between these two groups. These results demonstrate that the porous calcium phosphate ceramics after the whiskering process has good ability to repair the defects of femoral condyle.       

骨诱导性磷酸钙陶瓷材料修复牙槽突裂

BACKGROUND: In our previous studies, we had prepared calcium phosphate ceramics with better ectopic osteogenesis. OBJECTIVE: To explore the effect of novel osteoinductive calcium phosphate ceramics in the repairing of alveolar cleft. METHODS: Bilaterl alveolar defects were created in nine immature beagles. Three months later, osteoinductive calcium phosphate ceramics with high modular surface (experimental group) and smooth surface (control group) were randomly implanted in each side of the defect. Meanwhile, the corresponding material was implanted into the thigh muscle. New bone formation in the implanted region, osteogenesis in the implanted region and muscle, and respair results were respectively observed by fluorescence microscope, light microscope and CT at 4, 8 and 12 weeks after implantation. RESULTS AND CONCLUSION: (1) Fluorescence microscope observation: A circular permutation of red, yellow and green fluorescent strip could be observed in both two groups. (2) Light microscope observation: At 12 weeks after implantation, in the experimental group, the bone reconstruction was obvious, the implant material was decomposed gradually, the gap was filled with a large number of mature bone that combined with the rest material closely, and numerous Haversian canals appeared; the control group was similar but slightly inferior to the experimental group in the quality of new bone. The experimental group material successfully induced heterotopic osteogenesis in muscle, while the control did not. (3) CT examination: The two group materials restored the appearance and continuity of the alveolar ridge, and made no effect on the eruption of permanent teeth in both sides of the defect. To conclude, our findings suggest that the novel osteoinductive calcium phosphate ceramic exhibits advantages in alveolar cleft repair with earlier osteogenesis activation, faster osteogenesis rate and more bone formation than those traditional materials.     

Bone in-growth induced by biphasic calcium phosphate ceramic in femoral defect of dogs

Biphasic calcium phosphate (BCP) ceramics consisting of hydroxyapatite (HA) and tricalcium phosphate (TCP) has been used as a bone graft material during the last decade. In this paper, we report the bone in-growth induced by BCP ceramic in the experimentally created circular defects in the femur of dogs. This BCP ceramic consists of 55% hydroxyapatite (HA) and 45% b-tricalcium phosphate (TCP) prepared in situ by the microwave method. The defects were created as 4-mm holes on the lateral aspect of the femur of dogs and the holes were packed with the implant material. The defective sites were radiographed at a period of 4, 8, and 12 weeks postoperatively. The radiographical results showed that the process of ossification started after 4 weeks and the defect was completely filled with new woven bone after 12 weeks. Histological examination of the tissue showed the formation of osteoblast inducing the osteogenesis in the defect. The collageneous fibrous matrix and the complete Haversian system were observed after 12 weeks. The blood serum was collected postoperatively and biochemical assays for alkaline phosphatase activity were carried out. The measurement of alkaline phosphatase activity levels also correlated with the formation of osteoblast-like cells. This microwave-prepared BCP ceramic has proved to be a good biocompatible implant as well as osteoconductive and osteoinductive materials to fill bone defects.     

磷酸钙人工骨联合雷洛昔芬修复兔下颌骨缺损

背景：雷洛昔芬是第3代选择性雌激素受体调节剂,可减少骨量的丢失,增加骨组织中的矿物质含量,降低骨折风险。 目的：观察雷洛昔芬结合自固化磷酸钙人工骨修复兔下颌骨缺损的效果。 方法：在36只新西兰大白兔左侧下颌骨制作8 mm×4 mm×3 mm的缺损模型,随机分组,实验组12只植入自固化磷酸钙人工骨,并给予雷洛昔芬7.5 mg/(kg•d);药物组12只给予雷洛昔芬7.5 mg/(kg•d);人工骨组12只植入自固化磷酸钙人工骨。分别于治疗4,8,12周取下颌骨标本,免疫组织化学法观察骨形态发生蛋白2的表达,激光共聚焦显微镜观察转化生长因子β的表达。 结果与结论：实验组治疗后4,8周时的骨形态发生蛋白2免疫组织化学染色阳性细胞数明显高于药物组与人工骨组,治疗后12周时实验组骨改建基本完成,骨形态发生蛋白2免疫组织化学染色阳性细胞数目低于其他两组。实验组转化生长因子β免疫荧光染色表达为逐步升高,到第8周时达到峰值,而药物组和人工骨组的转化生长因子β免疫荧光表达从4-12周一直呈上升状态,趋近于最高峰。说明雷洛昔芬能够促进自固化磷酸钙人工骨在骨缺损过程中骨形态发生蛋白的早期表达及早期骨痂的形成,加快骨缺损修复。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

Low-level laser therapy, at 60 J/cm2 associated with a Biosilicate(®) increase in bone deposition and indentation biomechanical properties of callus in osteopenic rats

We investigate the effects of a novel bioactive material (Biosilicate(?)) and low-level laser therapy (LLLT), at 60 J/cm(2), on bone-fracture consolidation in osteoporotic rats. Forty female Wistar rats are submitted to the ovariectomy, to induce osteopenia. Eight weeks after the ovariectomy, the animals are randomly divided into four groups, with 10 animals each: bone defect control group; bone defect filled with Biosilicate group; bone defect irradiated with laser at 60 J/cm(2) group; bone defect filled with Biosilicate and irradiated with LLLT, at 60 J/cm(2) group. Laser irradiation is initiated immediately after surgery and performed every 48 h for 14 days. Histopathological analysis points out that bone defects are predominantly filled with the biomaterial in specimens treated with Biosilicate. In the 60-J/cm(2) laser plus Biosilicate group, the biomaterial fills all bone defects, which also contained woven bone and granulation tissue. Also, the biomechanical properties are increased in the animals treated with Biosilicate associated to lasertherapy. Our results indicate that laser therapy improves bone repair process in contact with Biosilicate as a result of increasing bone formation as well as indentation biomechanical properties.     

β-磷酸三钙/聚磷酸钙纤维/聚左旋乳酸支架复合骨髓基质细胞修复节段性骨缺损

背景：组织工程β-磷酸三钙/聚磷酸钙纤维/聚左旋乳酸支架材料具有良好的生物相容性。 目的：评估骨髓基质细胞与β-磷酸三钙/聚磷酸钙纤维/聚左旋乳酸复合体修复兔桡骨大段骨缺损成骨的效果。 方法：取新西兰大白兔40只,建立桡骨双侧大段骨缺损模型,其中35只右侧植入自体骨髓基质细胞与β-磷酸三钙/聚磷酸钙纤维/聚左旋乳酸复合物作为实验组,左侧植入β-磷酸三钙/聚磷酸钙纤维/聚左旋乳酸支架材料作为对照组;另5只作为空白对照不作任何处理。植入后4,8,12,16周拍摄X射线片观察骨缺损修复情况。 结果与结论：实验组术后2周可见缺损处有散在的、少量模糊状骨痂生成,术后4周可见明显骨生成影像,成云雾状,均匀分布在骨缺损区,术后8周整个缺损区均可见骨痂生成,成骨现象更加明显,部分髓腔已通,术后12~16周,缺损区已完全被新生骨组织充填,骨髓腔已完全再通,修复区较正常桡骨细,骨缺损修复效果明显优于对照组与空白对照组(P < 0.01)。说明自体骨髓基质细胞与β-磷酸三钙/聚磷酸钙纤维/聚左旋乳酸复合移植可较完全修复大节段骨缺损。     

Implantation of green tea catechin α-tricalcium phosphate combination enhances bone repair in rat skull defects

The purpose of the present study is to investigate effects of the combination of epigallocatechin-3-gallate (EGCG) and α-tricalcium phosphate (α-TCP) on bone regenerative capacity in a bilateral rat calvarial bone defect model. Materials and methods: Bilateral 5-mm-diameter calvarial defects were created in adult male Wistar rats and filled with preparations of EGCG (0, 0.1, 0.2, 0.4 mg) combined with α-TCP particles. This was done by dissolving EGCG in 100% ethanol (50 μL/14 mg) and dropping under sterile condition. The control group was left unfilled (n = 8). The animals were sacrificed at 2 and 4 weeks. Radiological images were taken, and histological analysis was done. Six animals from control (0 mg EGCG + α-TCP) group and (0.2 mg EGCG+ α-TCP) group were labeled with fluorescent dyes and histomorphometrically analyzed (n = 6) at 2 and 4 weeks. Results: Histomorphometric analysis revealed that the combination of EGCG and α-TCP at doses of 0.1 and 0.2 mg yielded significantly more new bone formation than untreated control group at 2 and 4 weeks (p > 0.05). Mineral apposition rate at 0.2-TCP group was enhanced compared with the one of the positive control α-TCP group at 4 weeks (p > 0.05). Conclusion: The combination of α-TCP particles and 0.2 mg EGCG stimulates maximum bone regeneration in rat calvarial defects, and this combination would be potentially effective as bone graft material.     

Bone formation induced by strontium modified calcium phosphate cement in critical-size metaphyseal fracture defects in ovariectomized rats

The first objective was to investigate new bone formation in a critical-size metaphyseal defect in the femur of ovariectomized rats filled with a strontium modified calcium phosphate cement (SrCPC) compared to calcium phosphate cement (CPC) and empty defects. Second, detection of strontium release from the materials as well as calcium and collagen mass distribution in the fracture defect should be targeted by time of flight secondary ion mass spectrometry (TOF-SIMS). 45 female Sprague–Dawley rats were randomly assigned to three different treatment groups: (1) SrCPC (n = 15), (2) CPC (n = 15), and (3) empty defect (n = 15). Bilateral ovariectomy was performed and three months after multi-deficient diet, the left femur of all animals underwent a 4 mm wedge-shaped metaphyseal osteotomy that was internally fixed with a T-shaped plate. The defect was then either filled with SrCPC or CPC or was left empty. After 6 weeks, histomorphometric analysis showed a statistically significant increase in bone formation of SrCPC compared to CPC (p = 0.005) and the empty defect (p = 0.002) in the former fracture defect zone. Furthermore, there was a statistically significant higher bone formation at the tissue–implant interface in the SrCPC group compared to the CPC group (p < 0.0001). These data were confirmed by immunohistochemistry revealing an increase in bone-morphogenic protein 2, osteocalcin and osteoprotegerin expression and a statistically significant higher gene expression of alkaline phosphatase, collagen10a1 and osteocalcin in the SrCPC group compared to CPC. TOF-SIMS analysis showed a high release of Sr from the SrCPC into the interface region in this area compared to CPC suggesting that improved bone formation is attributable to the released Sr from the SrCPC.     

Apatite-wollastonite containing glass ceramic-fibrin mixture as a bone defect filler

The purpose of this study was to evaluate the usefulness of a mixture of apatite-wollastonite containing glass ceramic (A-W.GC, 42-60 mesh in granule size) with fibrin as a bone defect filler. A bone defect was drilled in the proximal metaphysis of the rat tibia and was filled with (1) fibrin glue, (2) A-W.GC granules, or (3) A-W.GC-fibrin mixture. Nothing was placed in the defect of the controls. The animals were serially sacrificed until 8 weeks after the operation, and the defect site was histologically examined and histomorphometrically analyzed for quantitative evaluation of newly formed bone and blood vessels. The use of fibrin glue as the binder markedly increased the ease of handling the A-W.GC granules. In the controls, little trabecular regeneration was observed in the defect site. Early vascularization (confirmed by microangiography) increased and the repairing process was accelerated in the defects filled with fibrin. In these defects filled with A-W.GC granules, good bone formation was observed around the granules. Bone formation was accelerated in the defects filled with A-W.GC fibrin mixture. Thus, the mixture showed good osteoconductive potential as well as acceleration of the repair process. Therefore, A-W.GC-fibrin mixture is considered to be a useful bone defect filler.     

跑步锻炼大鼠缺损股骨干内的骨质生长

背景：研究已经证实,力学刺激能够促进骨折的愈合。但是,跑步锻炼所产生的力学刺激能否增加骨材料的骨传导性和促进骨缺损的愈合尚不清楚。 目的：观察跑步锻炼所产生的间接力学刺激对骨缺损愈合和骨材料成骨性能的影响。 方法：在12周龄SD大鼠左股骨远端制作一个直径3 mm、高3 mm的缺损,然后在缺损内塞入同等大小的硫酸钙支架材料。实验组于术后1周开始以10 m/min,45 min/d,5 d/周的策略进行跑步锻炼,持续3周;对照组不给予跑步锻炼。 在术后1,2,3,4周进行micro-CT扫描以观察缺损内的成骨情况。实验结束后,取股骨远端制作切片后进行苏木精-伊红染色观察骨缺损内新骨生成和骨材料降解情况。 结果与结论：通过micro-CT分析得到,术后1周时,实验组和对照组的骨缺损内已经有少量的新骨形成。在2,3,4周时,实验组骨缺损内新骨生成量明显高于对照组,差异有显著性意义(P < 0.05)。在4周时,组织学切片结果也说明实验组新骨生成情况明显优于对照组。另外,给予跑步锻炼之后,实验组骨缺损内生成的新骨骨密度高于对照组,但差异无显著性意义(P > 0.05)。结果表明,适度的跑步锻炼确实能够增加骨材料的成骨性能和加速骨缺损的愈合。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

Biocompatibility and resorption of a brushite calcium phosphate cement

A hydraulic calcium phosphate cement with beta-tricalcium phosphate (TCP) granules embedded in a matrix of dicalcium phosphate dihydrate (DCPD) was implanted in experimentally created defects in sheep. One type of defect consisted of a drill hole in the medial femoral condyle. The other, partial metaphyseal defect was located in the proximal aspect of the tibia plateau and was stabilized using a 3.5 mm T-plate. The bone samples of 2 animals each per group were harvested after 2, 4, 6 and 8 weeks. Samples were evaluated for cement resorption and signs of immediate reaction, such as inflammation, caused by the cement setting in situ. Differences regarding these aspects were assessed for both types of defects using macroscopical, radiological, histological and histomorphometrical evaluations. In both defects the brushite matrix was resorbed faster than the beta-TCP granules. The resorption front was followed directly by a front of new bone formation, in which residual beta-TCP granules were embedded. Cement resorption occurred through (i) extracellular liquid dissolution with cement disintegration and particle formation, and (ii) phagocytosis of the cement particles through macrophages. Signs of inflammation or immunologic response leading to delayed new bone formation were not noticed at any time. Cement degradation and new bone formation occurred slightly faster in the femur defects.     

快速成型聚乳酸-聚羟乙酸/磷酸三钙支架修复兔桡骨缺损

背景：理想的骨修复材料除必须具有生物相容性、可吸收性、利于血管化及迅速被新生组织替代的孔隙率,还需要有与骨组织相似三维结构。 目的：检验快速成型工艺制作的聚乳酸-聚羟乙酸/磷酸三钙支架复合骨形态发生蛋白修复兔桡骨缺损的效果。 方法：将乳酸乙醇酸共聚物溶于1,4-二氧六环中并混合粉末状磷酸三钙制备成液态的浆料,放入生物材料快速成形机TissFormTM制备出直径5 mm,长15 mm的圆柱形人工骨载体材料。按每个材料15 mg的标准,采用预湿、负压复合骨形态发生蛋白、冻干3步处理,制备出活性人工骨材料。健康新西兰大白兔20只,制备右前肢桡骨中上段15 mm骨缺损模型,实验组和对照组分别植入复合骨形态发生蛋白的活性人工骨和未复合骨形态发生蛋白的单纯支架。通过影像学、组织学、材料降解及骨密度评价修复兔桡骨缺损的效果。 结果与结论：12周时实验组骨缺损愈合,新生骨痂连接缺损断端并塑形,支架材料近于完全降解,各检测指标与对照组比较差异均有显著性意义,对照组骨缺损内未见新骨形成。结果表明复合骨形态发生蛋白的聚乳酸-聚羟乙酸/磷酸三钙支架可以很好的修复兔15 mm骨缺损,且降解速度与成骨速度匹配良好。     

Effect of low intensity pulsed ultrasound on healing of an ulna defect filled with a bone graft substitute

A 1.5 cm unilateral rabbit ulna defect model was performed in 18 adult NZ white rabbits. The defects were filled with a beta-tricalcium phosphate bone graft substitute (JAX TCP). The surgical site in half the animals was treated daily with 20 min of low intensity pulsed ultrasound (LIPUS). Animals were sacrificed at 4 weeks (n = 3 per group) or 12 weeks (n = 6 per group) following surgery for radiographic and histologic endpoints. Radiography revealed some resorption of the JAX TCP by 12 weeks in the control and LIPUS treated groups. LIPUS treatment did not accelerate this resorption. Some new bone formation was noted in the control groups at the defect margins while little bone formed in the center of the defect at 4 and 12 weeks. In contrast, radiographs revealed more new bone at 4 and 12 weeks in the LIPUS treated animals throughout the section. Bone mineral density (DEXA) revealed a statistically significant difference at 4 weeks with LIPUS while no differences were found at 12 weeks. Histology of the LIPUS treated sections demonstrated new woven bone formation on and between the JAX TCP bone graft substitute particles across the defect. VEGF expression was increased with LIPUS treatment at 4 weeks and remained elevated at 12 weeks compared with controls. CBFA-1 expression levels were elevated with LIPUS treatment at both time points. LIPUS treatment increased bone formation in ulna defect healing with a beta-tricalcium phosphate bone graft substitute.