异体DBM复合rhBMP-2修复兔桡骨缺损的实验研究

目的探讨异体脱钙骨基质（demineralized bonematrix，DBM）复合重组人骨形态发生蛋白2（reconstruction humn bonemorphology protein-2，rhBMP-2）修复节段性骨缺损的能力。方法48只新西兰大白兔采用桡骨15mm节段性骨缺损模型，随机分为3组，A组植入异体DBM与rhBMP-2复合材料，B组植入异体DBM，C组为空白对照组。术后4周、8周、12周、16周．进行放射学和组织学检查。结果A组：术后4周宿主结缔组织长入植骨材料内的骨小梁间，并有岛状新生软骨、骨组织形成；术后8周，新生软骨及骨形成并融合成片；术后12周，新骨改建成熟，但仍能见到植骨材料；术后16周，管状骨结构形成，髓腔再通。B组：术后4周，植骨材料周围有软骨形成；术后8周，大量软骨形成；术后12周，大片状骨形成；术后16周，有髓腔形成。C组：各时问点仅见有纤维结缔组织，只在两端有新骨形成。X片示A组成骨量大，新骨改建、成熟迅速，术后16周全部达骨性愈合。B组成骨量少，仅2例达骨性愈合。C组未见骨性愈合。结论异体DBM复合rhBMP-2材料通过骨诱导和骨传导两种方式修复骨缺损，是一种较理想、具有高效成骨活性的植骨材料。     

不同剂量rhBMP2修复兔桡骨骨缺损的比较

[目的]利用兔桡骨临界骨缺损模型，研究不同剂量的重组人骨发生蛋白2 (recombinant human bone morphogenetic protein-2, rhBMP-2)对骨缺损修复的量效关系。[方法]将36只新西兰白兔建立单侧桡骨骨缺损模型，随机分为空白组、海绵空白组、自体骨组、低剂量组（0.25 mg rhBMP-2）、中剂量组（0.5 mg rhBMP-2）、高剂量组（2.5 mg rhBMP-2），每组6只。对骨缺损给予相应处理。分别于术后4、8周，行X线检查、MicroCT检查和组织学观察评估。[结果]与术后第4周相比，8周时各组Lane Sandhu X线评分均增加，其中，空白组和海绵空白组两个时间点间差异无统计学意义（P>0.05），而自体骨组、低、中、高剂量组的两时间点间差异有统计学意义（P<0.05）。相应时间点，Lane Sandhu X线评分由低至高均为空白组<海绵空白组<低剂量组<自体骨组<中剂量组<高剂量组，差异有统计学意义（P<0.05）。与术后4周相比，8周时6组MicroCT检测的骨矿密度（bo...     

rhBMP-2/异体骨复合骨应用于兔腰椎植骨融合的实验研究

目的评价rhBMP-2/异体骨复合骨在兔腰椎后路横突间植骨融合中的效果,探讨此复合骨替代自体骨用于腰椎后路横突间植骨融合的可能性。方法30只新西兰大白兔随机分为三组,行后路腰椎横突间植骨融合术,分别植入自体髂骨条、rhBMP-2/异体骨复合骨及单纯异体髂骨条。术后喂养6周,处死动物,取出标本,分别采取盲法进行手工测试,影像学、组织学观察及单向拉伸的生物力学测试,并用图像分析系统定量分析植骨区内成骨量,取得数据后进行综合评价。结果手工测试显示rhBMP-2/异体骨复合骨组融合率(90%)明显优于自体骨(40%)及异体骨组(20%)(P＜0．05)。影像学及组织学显示rhBMP-2/异体骨复合骨组成骨速度及骨成熟程度均优于其它两组。单向拉伸生物力学测试结果表明复合骨组和自体骨组两组间无明显差别(P＞0．05),但均明显优于异体骨组(P＜0．05)。定量分析显示植骨区内新骨形成面积复合骨组和自体骨组两组间无明显差别(P＞0．05),但均明显优于异体骨组(P＜0．05)。结论在兔腰椎后路横突间植骨融合术中,rhBMP-2/异体骨复合骨可促进骨形成并提高融合率,可作为替代自体骨的理想材料。     

聚乳酸作为骨形态发生蛋白载体修复骨缺损的实验研究

目的 探讨聚乳酸（ｐｏｌｙｌｄａｃ ａｃｉｄ,ＰＬＡ）作为骨形态发生蛋白（ｂｏｎ ｅ ｍｏｒｐｈｏｇｅｎｅｔｉｃ ｐｒｏ－ｔｅｉｎ,ＢＭＰ）载体的可行性及观察其诱导成骨能力。方法 手术造成日本大耳白兔左尺骨中上段１２ｍｍ骨缺损实验模型。随机分为实验。对照及空白组,实验组植入以ＰＬＡ为载体的ＢＭＰ１０ｍｇ、对照组植入以牛松质骨基质为载体的ＢＭＰ１０ｍｇ、空白组不做任何处理,术后摄Ｘ线片观察各组不同时相骨缺损修复情况,并于术后第４、８、１２周观察各组缺损内组织学变化。图像分析骨小梁的生成量。结果 实验修复情况优于对照组,无论是骨连接发生时间还是骨成熟时间,实验组均较对照组提前２周左右,同期骨生成量也明显多于对照组,而空白组缺损内主要形成纤维组织。结论 ＰＬＡ可以作为ＢＭＰ的载体修复骨缺损,它比异种松质骨基质载体的成骨效     

冷冻同种异体皮质骨复合重组人骨形态发生蛋白-2修复兔大段负重骨缺损

我们将深低温冷冻同种异体皮质骨与重组人骨形态发生蛋白 2 (rhBMP 2 )、Ⅰ型可吸收胶原海绵 (ACS)复合 ,植入兔股骨大段缺损处 ,探讨其修复功能。一、材料与方法1.试剂与异体骨 :rhBMP 2 (北京军事医学科学院 ) ;Ⅰ型可吸收胶原海绵(ACS ,北京益而康生物有限公司 ) ;-80℃深低温冰箱保存同种异体皮质管状骨(自制 )。2 .动物分组 :健康新西兰大白兔 40只 ,体重 2 .5～ 3 .0kg ,雌雄不分。随机分成 5组 ,每组 8只兔。A组 :植入异体骨 +rhBMP 2 +ACS ;B组 :植入异体骨+rhBMP 2 ;C组 :植入异体骨 +ACS ;D组 :单纯植入异体骨 ;E组 …     

bBMP—胶原—珊瑚复合人工骨修复桡骨干骨缺损的实验研究

目的 评价牛骨形态发生蛋白（bBMP）－胶原－珊瑚复合人工骨对长骨干骨缺损的修复效果。方法 建立46只兔双侧桡骨干骨缺损模型,分为4组：1．人工骨组（18侧）、2．自体骨组（16侧）、3．单纯珊瑚组（12侧）、4．对照组（为以上各组的左侧,未治疗）。于4周及16周未分别行X线、病理学、ALP活性、四环素荧光标记及生物力学检查。结果 4周,人工骨组组织中的ALP活性高于对照组。16周,1、2、3、4组的愈合率,分别为75％（9／12）、100％（10／10）、28．6％（2／6）、31．0％（9／29）。与3组及4组相比,1组及2组的荧光带较宽,桡骨的抗弯强度较高。结论 复合人工骨有较强的修复长骨干骨缺损的能力,有望成为自体骨的替代品。     

经皮注射骨形态发生蛋白和成纤维细胞生长因子促进兔骨缺损愈合

作者报告了以聚乙烯吡咯烷酮（ＰＶＰ）作为牛骨形态发生蛋白（ｂＢＭＰ）和基因重组碱性人成纤维细胞生长因子（ｂＦＧＦ）可溶性载体，将三者的混悬液经皮注射入小鼠肌肉和兔桡骨缺损处的实验研究。经不同时间点的Ｘ线摄片，组织学检查，结果发现成骨量及骨缺损愈合明显高于对照组（Ｐ〈０．０１）。注射入小鼠肌肉后及兔桡骨缺损区，观察到与新骨伴随的血管增生。证实该两种因子的联合植入，成骨作用大于单用骨形态发生蛋白，骨成     

骨形态发生蛋白-2基因活化纳米骨浆修复兔桡骨缺损的实验研究

目的观察骨形态发生蛋白-2（BMP-2）基因活化纳米骨浆在损伤部位的局部成骨基因表达和骨缺损重建修复效果。方法新西兰白兔54只，其中48只实验动物随机分成三组（每组16只32侧），制成双侧桡骨中段15mm骨缺损模型。A组：注入hBMP-2＋纳米骨浆；B组：注入空白质粒＋纳米骨浆；C组：注入纳米骨浆。另6只动物制作左桡骨中段骨缺损，不植入材料，作为空白对照。术后4、8和12周取材行影像学检查、组织学观察、分子生物学检测和生物力学检测。结果术后12周A、B和C组骨缺损均修复，A组骨缺损处有明显BMP-2的mRNA和蛋白质表达，在ALP水平、成骨速度、新生骨量及新生骨力学强度等方面均明显优于B、C两组（P〈0．05）。空白对照组骨缺损无愈合。结论纳米骨浆复合BMP-2质粒后，具有一定骨诱导作用，植入体内后成骨速度、质量及力学强度较单纯的纳米骨浆明显增强，能够有效修复骨缺损。     

骨形态发生蛋白及其在骨缺损修复中应用进展

骨形态发生蛋白(BMP)有成骨作用,已应用于骨组织工程修复骨缺损。除成骨作用外,BMP在其他组织的发育中也发挥重要的生物学作用。目前BMP修复骨缺损的实验研究热点包括BMP复合各种有机或无机载体修复骨缺损、BMP多基因联合、BMP与其他生长因子协同作用、BMP转导或转染种子细胞后缓慢释放、诱导种子细胞向成骨细胞分化等。部分BMP已引入临床骨缺损治疗,并取得了显著疗效。大多数研究还处于实验阶段,有待进一步探索。     

rhBMP-2/CPC对骨质疏松骨缺损的治疗作用的研究

目的 探讨磷酸钙骨水泥复合rhBMP-2对骨质疏松骨缺损的治疗作用.方法 以卵巢切除法对10只成年山羊去势,低钙膳食6个月后建立骨质疏松模型;手术去除每只动物L2、L4椎体部分侧方骨质,造成约5 mm×10 mm×10mm大小骨缺损,将动物随机分成2组,一组植入rhBMP-2/CPC作为实验组,另一组植入CPC作为对照组;术后1周、9周分别采用双能x线吸收骨密度仪检测手术椎体骨密度、CT三维成像观察骨缺损愈合情况,术后9周手术椎体进行牛物力学检测,制作椎体不脱钙切片进行骨组织计量学分析.结果 术后骨密度检测实验组与对照组间差异无显著性,但实验组在骨缺损愈合状况、骨小梁微结构及骨牛物力学性能等方面均显著优于对照组.结论 应用rhBMP-2/CPC能改善局部骨质疏松,促进骨质疏松骨缺损愈合,达到治疗骨质疏松骨折骨缺损的目的 .     

重组人骨形态发生蛋白-2诱导脂肪成体干细胞成异位软骨的研究

目的探索重组人骨形态发生蛋白-2（rhBMP-2）诱导脂肪成体干细胞异位软骨的生成能力。方法将获取的兔脂肪组织机械分割，通过Ⅰ型胶原酶消化后得到脂肪成体干细胞。经rhBMP-2诱导培养14d的脂肪成体干细胞微球种植在BALB／C裸鼠肌袋内。术后4、8周各处死2只动物，取材固定、脱钙、包埋后切片染色。镜下观察。结果经过rhBMP-2连续诱导培养14d的脂肪成体干细胞已具有软骨细胞的表型（细胞基质中富含蛋白多糖和Ⅱ型胶原），并不向成骨方向分化（Von kossa染色阴性）。术后4、8周有软骨细胞形成。结论rhBMP-2具有诱导脂肪成体干细胞向软骨细胞分化的潜能。     

重组人骨形态发生蛋白-2对鼠雪旺细胞增殖及生长相关蛋白GAP-43表达的影响

目的 观察重组入骨形态发生蛋白-2( rhBMP-2)对体外培养的乳鼠雪旺细胞增殖及生长相关蛋白( GAP-43)表达的影响。方法 将纯化的雪旺细胞分两组,一组设为对照,另一种加含终质量浓度为5 μg/L rhBMP-2的DMEM/F12培养液培养,在培养后0、12、24、36、48、72 h分别用噻唑蓝(MTT)比色法检测不同时间点的A值并绘制生长曲线;用BrdU法测定雪旺细胞增殖率;用Western blot法检测GAP-43蛋白的表达水平。结果 经含5μg/L rhBMP-2培养液培养的雪旺细胞,在24、36、48 h细胞增殖率明显高于对照组,差异有统计学意义(P＜0.05);实验组中GAP-43在24、36、48 h的表达也显著高于对照组(P＜0.05)。结论 rhBMP-2有促进雪旺细胞分裂增殖和GAP-43蛋白表达的作用,可能是其促进周围神经再生的重要机制之一。     

人重组骨形态发生蛋白-2修复全层关节软骨缺损的实验研究

目的 :研究人重组骨形态发生蛋白 2 (rhBMP 2 )对全层关节软骨缺损的修复 ,观察修复效果。方法 :家犬 8只 (16膝 ) ,每个膝内外髁均做全层软骨缺损 ,内外髁共 3 2个缺损。随机分为 4组 ,每组 2只。每只犬一侧关节行胶原海绵吸附rh BMP填充内外髁缺损 ,另一侧以单纯胶原海绵填充作对照 ,不处理组为空白对照。术后 2、4、 8、 12周取材作大体、光镜、透射电镜观察。结果 :rh BMP组为类软骨细胞修复 ,而单纯胶原海绵组和空白组均为纤维性修复。结论 :rhBMP 2有效地促进关节软骨缺损的修复 ,可以作为临床上治疗关节软骨缺损的方法     

The effect of locally delivered recombinant human bone morphogenetic protein-2 with hydroxyapatite/tri-calcium phosphate on the biomechanical properties of bone in diabetes-related osteoporosis

BackgroundRecombinant human bone morphogenetic protein-2 (rhBMP-2) is particularly effective in improving osteogenesis in patients with diminished bone healing capabilities, such as individuals with type 1 diabetes mellitus (T1DM) who have impaired bone healing capabilities and increased risk of developing osteoporosis. This study measured the effects of rhBMP-2 treatment on osteogenesis by observing the dose-dependent effect of localized delivery of rhBMP-2 on biomechanical parameters of bone using a hydroxyapatite/tri-calcium phosphate (HA/TCP) carrier in a T1DM-related osteoporosis animal model.ResultsAt the 4-week time point, the LD and HD groups both exhibited significantly higher BMD than controls; at the 8-week time point, the HD group exhibited significantly higher BMD than controls. Biomechanical testing revealed dose-dependent, higher trends in all parameters tested at the 4- and 8-week time points, with minimal significant differences.ConclusionsGroups treated with rhBMP-2 demonstrated improved bone mineral density at both 4 and 8 weeks compared to control saline groups, in addition to strong trends towards improvement of intrinsic and extrinsic biomechanical properties when compared to control groups. Data revealed trends toward dose-dependent increases in peak torque, torsional rigidity, shear stress, and shear modulus 4 weeks after rhBMP-2 treatment.

Level of evidence

Not applicable.     

重组人骨形态发生蛋白-2缓释微球对成骨细胞的作用

目的　探讨甲基丙烯酸缩水甘油酯右旋糖酐 (dex GMA)重组人骨形态发生蛋白(rhBMP 2 )凝胶微球 (rhBMP2 dex HM )对成骨细胞的生物学作用。方法　将单纯rhBMP 2 (A组 )、空白dex GMA凝胶微球dex HM (B组 )和rhBMP2 dex HM (C组 )加入成骨细胞培养液中 ,用细胞计数法、噻唑蓝比色法 (MTT法 )、流式细胞仪观察细胞增殖情况 ,并检测成骨细胞上清液中骨钙素 (BGP)含量。结果　培养 1～ 2d后 ,3组细胞计数、吸光度 (A)值差异无统计学意义 (P >0 .0 5 ) ;4～ 6d时A、C组细胞计数和A值开始高于B组 ,但A、C组间差异无统计学意义 (P >0 .0 5 ) ;培养 6～ 8d后 ,C组明显高于其他组 ,差异有统计学意义 (P <0 .0 1)。14d后 ,A、B、C 3组细胞数分别为 (2 2 .97± 0 .2 3 )、(13 .89± 0 .5 7)和 (3 2 .46± 0 .67)× 10 4个细胞 /ml,差异有统计学意义(P <0 .0 1)。流式细胞仪检测结果显示 ,培养 2d后 ,A组的G2 /M +S期百分数最高 ;6～ 8d后 ,C组的G2 /M +S期百分数最高。成骨细胞上清液中BGP含量 ,C微球组最高 ,其次为A组。结论　rhBMP 2 dex HM可以较长时间持续释放活性rhBMP 2 ,作为rhBMP 2的缓释载体 ,可以明显促进成骨细胞增殖和分化。     

The short-term therapeutic effect of recombinant human bone morphogenetic protein-2 on collagenase-induced lumbar facet joint osteoarthritis in rats

OBJECTIVE: To determine whether an intra-articular injection of recombinant human bone morphogenetic protein-2 (rhBMP-2) alleviates cartilage degradation in a rat model of osteoarthritis (OA) of the lumbar facet joint. METHOD: The right-side facet joint OA model was created by an intra-articular injection of collagenase (type II) 2 weeks before treatment. The OA rats were divided into four groups: (1) no treatment, or intra-articular injection of either (2) saline, (3) rhBMP-2 10 ng, or (4) rhBMP-2 100 ng. The left-side facet joint served as the normal control. At 3 and 6 weeks after treatment, histological analyses were performed on the cartilage, synovium, subchondral bone and bone marrow. The cartilage and synovium were graded using a modified Mankin score and a synovium score system. Extracellular type II collagen was evaluated by immunohistochemistry. RESULTS: Intra-articular injection of collagenase causes OA-like changes in the facet joint. OA rats treated with rhBMP-2 at both dosages tested showed reduced severity of their cartilage lesions compared with untreated and saline-treated groups. There was a statistically significant difference in the modified Mankin score compared to the untreated and saline-treated groups. However, some rhBMP-2-treated rats at the higher dose (100 ng) showed, as a side effect, joint space obliteration caused by cartilage overgrowth. Also OA rats treated with 100 ng of rhBMP-2 displayed a significant synovium reaction at 3 weeks compared with that in other groups. Immunohistochemical analysis showed that treatment with rhBMP-2 significantly increased the content of type II collagen. CONCLUSION: This study demonstrates the potential efficacy of rhBMP-2 in the alleviation of arthritic changes in a rat model of OA of the lumbar facet joint. However, treatment with a high dosage of rhBMP-2 caused adverse side effects in some animals.     

骨形成蛋白-2转染兔骨髓基质细胞修复软骨缺损的研究

目的 观察骨形成蛋白-2(BMP-2)基因转染兔骨髓基质细胞(MSCs)复合藻酸钙修复兔膝关节软骨缺损的效果.方法 取4周龄的新西兰兔骨髓细胞,体外培养得到MSCs.选用24只成年新西兰兔,在两侧股骨髁非负重区造成全层软骨缺损模型,A组(实验组)植入BMP-2转染的MSCs+藻酸钙,B组(对照组Ⅰ)植入空质粒转染的MSCs+藻酸钙,C组(对照组Ⅱ)植入不含MSCs的藻酸钙,D组(对照组Ⅲ)旷置.12周后,观察软骨缺损修复情况及组织学评价.结果 实验组修复组织基本光滑,有大量Ⅱ型胶原蛋白表达,3个对照组修复组织Ⅱ型胶原蛋白表达量少,仍有明显缺损.实验组和3个对照组组织学评分差异有统计学意义(P＜0.05).结论 BMP-2转染兔MSCs修复软骨缺损效果优于其他对照组.     

重组人骨形态发生蛋白-2诱发黄韧带骨化的实验模型

目的 :建立脊柱黄韧带骨化的实验模型。方法 :以中国大白兔为实验对象 ,采用重组人骨形态发生蛋白 2(rhBMP 2 )作为诱导物 ,分别将rhBMP 2 /明胶海绵植入双侧黄韧带腹侧的硬膜外腔 (E1组 ) ,或直接将rhBMP 2注射到双侧的黄韧带内 (E2组 ) ,每一侧植入物中含rhBMP 2 10 0 μg。设立相应的对照组 (C1组、C2组 )。对手术节段进行X线、CT扫描及病理组织学检查。结果 :脊柱CT扫描发现E1组 4周时手术节段后正中椎板前方出现结节状高密度增高影 ,8周时密度进一步增高。病理组织学检查发现E1组手术节段韧带细胞分化为软骨细胞并发生骨化。E2组仅见黄韧带轻度增生肥厚及少量散在的软骨细胞。C1组和C2组黄韧带组织均未见明显异常改变。结论 :rhBMP 2可诱导脊柱黄韧带骨化 ;明胶海绵可作为BMP诱导成骨的载体。     

Complications of anterior cervical discectomy and fusion using recombinant human bone morphogenetic protein-2

The use of bone morphogenetic protein-2 (rhBMP-2) in spinal fusion has increased dramatically since an FDA approval for its use in anterior lumbar fusion with the LT cage. There are several reports of its use in transforaminal lumbar interbody fusion, posterolateral fusion, and anterior cervical fusion. Reports on adverse effects of rhBMP-2 when used in spinal fusion are scarce in literature. An Institutional Review Board approved retrospective study was conducted in patients undergoing anterior spinal fusion and instrumentation following diskectomy at a single center. Forty-six consecutive patients were included. Twenty-two patients treated with rhBMP-2 and PEEK cages were compared to 24 in whom allograft spacers and demineralized bone matrix was used. Patients filled out Cervical Oswestry Scores, VAS for arm pain, neck pain, and had radiographs preoperatively as well at every follow up visit. Radiographic examination following surgery revealed end plate resorption in all patients in whom rhBMP-2 was used. This was followed by a period of new bone formation commencing at 6 weeks. In contrast, allograft patients showed a progressive blurring of end plate-allograft junction. Dysphagia was a common complication and it was significantly more frequent and more severe in patients in whom rhBMP-2 was used. Post operative swelling anterior to the vertebral body on lateral cervical spine X-ray was significantly larger in the rhBMP-2 group when measured from 1 to 6 weeks after which it was similar. These effects are possibly due to an early inflammatory response to rhBMP-2 and were observed to be dose related. With the parameters we used, there was no significant difference in the clinical outcome of patients in the two groups at 2 years. The cost of implants in patients treated with rhBMP-2 and PEEK spacers was more than three times the cost of allograft spacers and demineralized bone matrix in 1, 2, and 3-level cases. Despite providing consistently good fusion rates, we have abandoned using rhBMP-2 and PEEK cages for anterior cervical fusion, due to the side effects, high cost, and the availability of a suitable alternative.     

Nitric oxide modulates recombinant human bone morphogenetic protein-2-induced corticocancellous autograft incorporation: a study in rat intertransverse fusion

A novel rat model was used to investigate the effect of nitric oxide synthase inhibition in posterior spinal fusion augmented with recombinant human bone morphogenetic protein-2. Nitric oxide (NO) has important physiological functions including the modulation of fracture healing. Recombinant human BMP-2 (rhBMP-2) enhances spinal fusion. It is not known whether nitric oxide has a role in rhBMP-2 enhanced spinal fusion and remodeling. A novel rat intertransverse fusion model was created using a defined volume of bone graft along with a collagen sponge carrier, which was compacted and delivered using a custom jig. The control groups consisted of a sham group (S, n = 20), an autograft + carrier group (A, n = 28) and a group consisting of 43 μg of rhBMP-2 mixed with autograft + carrier (AB, n = 28). Two experimental groups received a nitric oxide synthase (NOS) inhibitor, N ^G-nitro l-arginine methyl ester, in a dose of 1 mg/ml ad lib in the drinking water (AL, n = 28) and one of these experimental groups had rhBMP-2 added to the graft mixture at the time of surgery (ALB, n = 28). Rats were killed at 22 and 44 days, spinal columns subjected to radiology, biomechanics and histology. On a radiographic score (0–4) indicating progressive maturation of bone fusion mass, no difference was found between the A and AL groups, however, there was a significant enhancement of fusion when rhBMP-2 was added when compared to the A group (P < 0.001). However, on day 44, the ALB group showed significantly less fusion progression when compared to the AB group (P < 0.01). There was a 25% (P < 0.05) more fusion-mass-area in day 44 of ALB group when compared to day 44 of the AB group indicating that NOS inhibition delayed the remodeling of the fusion mass. Biomechanically, the rhBMP-2 groups were stiffer at all time points compared to the NOS inhibited groups. Decalcified histology demonstrated that there was a delay in graft incorporation whenever NOS was inhibited (AL and ALB groups) as assessed by a 5 point histological maturation score. In a novel model of rat intertransverse process fusion, nitric oxide synthase modulates rhBMP-2 induced corticocancellous autograft incorporation.