兔腱内与界面诱导成骨促进腱-骨愈合

[目的]探讨移植物成骨化诱导骨性连接促进肌腱-骨隧道(简称腱-骨)界面愈合的作用。[方法] 50只新西兰兔,其中30只一侧半腱肌肌腱内注入BMP愈合模型,一侧行肌腱移植物和腱-骨界面联合应用BMP(界面处理),对侧界面注射等量PBS为对照。采用X线片、大体解剖观察和组织形态学计量检测研究肌腱组织成骨化情况。[结果]术后12周时腱内处理侧肌腱组织H.E染色及Masson染色可见肌腱纤维内细胞增生明显,局部形成骨小梁样组织,部分区域还可见软骨样细胞存在。X线片检测结果显示肌腱组织钙化程度随术后时间延长而不断增加,肌腱组织钙化范围明显增大[4周:(5.51±0.45)mm~2;8周:(9.44±0.40) mm~2;12周:(20.26±0.98) mm~2,P0.01]。此外,肌腱组织高密度区域IOD值也随时间增加而显著增高[4周:(1178.56±62.71);8周:(2135.26±90.92);12周:(4726.72±374.41),P0.01]。术后12周时界面处理侧大体解剖观察可见肌腱移植物质地变硬,与周围骨组织紧密连接、局部融合。H.E染色和Masson染色结果显示肌腱移植物内部及腱-骨界面之间均可见新生骨组织形成,部分区域内新生骨组织与宿主骨组织形成骨性连接。处理侧与对照侧之间腱-骨界面愈合程度组织学评分差异有统计学意义[(6.60±0.77) vs(2.67±0.68),P 0.01]。[结论] BMP可诱导肌腱内骨化,并促进腱-骨界面形成骨性连接。     

兔自体骨膜包裹同种异体肌腱移植对腱-骨愈合的影响

目的 探讨兔同种异体肌腱表面包裹自体骨膜植入骨隧道对移植肌腱与骨隧道之间界面愈合的影响. 方法 健康4～5月龄新西兰白兔20只,体重2.5～3.0 kg,随机取一侧后肢作为实验组,另一侧后肢作为对照组.以同种异体肌腱在兔胫骨干骺端建立腱-骨固定模型,实验组骨隧道肌腱表面包裹自体骨膜,骨膜生发层朝向骨隧道;对照组骨隧道肌腱表面不包裹自体骨膜.分别于术后4、8周取标本作腱.骨界面的组织学检查(n=2),并进行最大拔出负荷的生物力学测试(n=8). 结果 术后4、8周标本大体观察,实验组骨隧道口周围新生骨较多;对照组新生骨少或不明显.组织学观察:术后4周实验组骨膜生发层内有大量间充质细胞增生,出现明显的膜内成骨,沿新生骨小梁周围可见大量骨母细胞呈栅形排列,新生骨小梁与骨膜延续:对照组腱-骨界面间无明显新生骨形成,有疏松结缔组织填充,腱-骨间连接较疏松.术后8周实验组新生骨和肌腱与骨隧道连接紧密,无间隙,新生骨量多,新生骨排列比较规则、整齐,腱-骨界面可见潮线形成,类似于正常腱-骨附着结构,骨膜内成纤维细胞增殖活跃,骨膜与肌腱间有较多纤维连接;对照组腱-骨界面局部有新生骨形成,排列紊乱,腱-骨间可见较多胶原纤维连接.术后4、8周,实验组最大拉出或拉断强度分别为(35.03±1.21)N/cm和(42.36±1.31)N/cm,对照组分别为(26.14 ±6.13)N/cm和(31.63±6.87)N/cm,两组比较差异均有统计学意义(P<0.05). 结论 兔自体骨膜包裹同种异体肌腱移植可缩短腱-骨间成骨时间,提高愈合强度,加速腱-骨间愈合.     

前交叉韧带重建术后腱-骨和骨-骨界面愈合的比较研究

目的 探讨并比较两种移植物重建前交叉韧带(anterior cruciate ligament,ACL)后早期移植物隧道界面愈合的生物学机制. 方法 55只成年新西兰大白兔,体重2.0～2.8 kg.左膝关节切取带胫骨.骨块的髌韧带作为供区,右膝关节作为自体移植重建ACL受区.移植物骨块端为骨.骨界面愈合模型,韧带端为腱.骨界面愈合模型.术后观察实验动物一般情况,术后第2、4和8周取材(n=5)行大体及组织学观察,并于第4、8周取材(n=20)进行生物力学检测. 结果 术后动物肢体活动情况良好,实验过程中ACL连续性完整,张力适中.组织学观察:术后2周骨.骨界面大部分区域为纤维组织连接,腱一骨界面主要为肉芽组织填充;术后4周骨.骨界面大部分区域骨性愈合,腱.骨界面可见成骨反应及大量成纤维细胞;术后8周骨.骨界面已完全骨性愈合,腱.骨界面部分区域可见Sharpey纤维,形成间接止点.生物力学观察:术后4周腱-骨界面拔出率为85%,骨.骨界面为15%;术后8周腱.骨界面拔出率为95%,骨.骨界面为5%;各时间点骨.骨界面拔出率与腱一骨界面拔出率比较差异均有统计学意义(P<0.001). 结论 ACL重建术后早期骨一骨界面较腱.骨界面在愈合强度和速度上具有优势.     

酸性成纤维细胞生长因子复合胶原蛋白对兔前交叉韧带重建后腱-骨愈合的影响

目的观察酸性成纤维细胞生长因子(a FGF)复合胶原蛋白对兔前交叉韧带(ACL)重建后腱-骨界面愈合的影响。方法将30只新西兰白兔随机分为实验组与对照组,每组15只,均取趾长伸肌腱作为移植物。实验组将a FGF/胶原蛋白复合物植入到重建的ACL腱-骨界面,对照组单纯行ACL重建。于术后第4、8、12周分别处死动物取材,将股骨与胫骨端分别固定于生物力学试验机上,测试移植肌腱的腱-骨界面抗拉伸强度,取其绝对值作比较;同时,将股骨隧道和胫骨隧道纵向剖开,取下标本组织学观察移植物界面愈合情况。结果术后第4、8、12周抗拉力强度实验组强于对照组,差异有统计学意义(P0.001)。两组动物均在第4周时移植物与骨隧道之间均形成了纤维结缔组织。术后第12周,实验组肌腱移植物在骨隧道内形成了纤维软骨移行带,类似于正常的纤维软骨连接,而对照组则形成了走向与骨隧道轴向垂直的Sharpey样纤维。结论a FGF复合胶原蛋白能促进兔ACL重建腱-骨界面的早期直接愈合。     

磷酸钙水泥对自体腘绳肌腱重建前交叉韧带后腱-骨愈合影响的生物力学研究

目的探讨骨形态发生蛋白结合型磷酸钙水泥(rhBMP-2-CPC)对自体腘绳肌腱重建前交叉韧带(ACL)后腱-骨愈合的影响。方法取54只成年新西兰大白兔,建立48只双膝关节ACL完全断裂的自身对照模型,24只用rhBMP-2-CPC充填移植腱-骨隧道界面(实验组),24只未用rhBMP-2-CPC(对照组),6只为生物力学试验的正常组。术后第2、4、8和12周取材进行生物力学检测。结果2、4、8和12周实验组肌腱移植物较对照组抗拉伸的最大载荷明显要大,差异有统计学意义(P<0.05)。结论实验组肌腱移植物的生物力学特性优于对照组;BMP-CPC能促进肌腱移植物在骨隧道内的早期腱-骨愈合。     

脱蛋白骨复合骨形态发生蛋白对前交叉韧带重建术后腱-骨愈合的影响

目的 探讨兔异体脱蛋白松质骨(DPB)复合骨形态发生蛋白(BMP)对前交叉韧带(ACL)重建术后腱-骨愈合的影响. 方法取96只成年新西兰大白兔,分为四组,每组24只:DPB+BMP组、DPB组、BMP组及空白对照组,分别用自体半腱肌腱进行膝关节ACL重建,DPB+BMP组在股骨隧道内植入DPB-BMP复合体,DPB组和BMP组分别在股骨隧道内植入DPB、BMP,空白对照组的骨隧道内不植入其他材料.于术后2、4、6、8周时分别处死各组中的6只动物,切取骨隧道内标本,通过大体观察及组织学观察分析腱-骨愈合进程. 结果术后2周时BMP+DBP组的骨隧道内新骨生成活跃,肌腱周围出现较多纤维软骨组织;4周时骨隧道内出现钙化的纤维软骨,肌腱末端与钙化软骨融合为一体,并见Sharpey's纤维形成;6周时隧道内出现了更多的钙化软骨,肌腱与骨的结合区出现潮线,具有正常ACL止点的结构特点;8周时肌腱与骨的连接更加成熟,钙化软骨增多.其他三组的腱-骨愈合过程均迟于DPB+BMP组.结论 DPB复合BMP能促进ACL重建术后的腱-骨愈合.     

膝关节持续被动活动对兔重建前交叉韧带腱骨愈合的影响

目的 通过兔半腱肌腱腱后固定方法重建前交叉韧带(ACL)实验动物模型,研究持续被动活动(CPM)对移植物隧道内腱骨界面的组织学转归影响.方法 对12只雄性新西兰大白兔右侧后肢膝关节行自体双股半腱肌腱移植重建ACL.术后随机分为两组:CPM组(n=6)术后第2天开始早期CPM康复6周;自由活动组(n=6)笼养.分别于术后第6、12、24周取材,采用HE和甲苯胺蓝染色观察腱骨愈合过程.结果 前侧腱骨界面纤维组织较多且较后侧腱骨界面宽;后侧腱骨界面的成骨细胞和类软骨细胞较多,新骨沉积较多.在骨道内口(关节腔入口),破骨细胞较多.与自由活动组比较,CPM组界面组织改建塑形更成熟、胶原排列更有序,潮线结构出现较早,类软骨细胞、成骨细胞和类似潮线的结构较多.结论 腱骨界面前侧张力较大,纤维较多;腱骨界面后侧压力较大,软骨较多.半腱肌腱重建ACL术后早期CPM加快移植物止点潮线结构恢复,增强移植物与骨组织之间整合.     

采用骨诱导性钙磷生物材料促进肌腱在骨隧道内愈合的组织学研究

目的通过组织学探讨骨诱导性钙磷陶瓷(OICPC)对肌腱在骨隧道内愈合的影响。方法将30只新西兰白兔制成膝关节半腱肌腱重建前交叉韧带悬吊固定模型,对照组(15只)为假手术组,实验组(15只)在隧道内植入OICPC。分别于术后4、8和12周采用HE、Masson和天狼星红染色,观察骨隧道和肌腱移植物间的界面组织学变化,界面形态采用Yamakado方法分类评价愈合类型,Masson染色切片做肌腱周围新骨形成的图像分析。结果4、8周OICPC组新骨形成大于对照组,差异有显著性意义(P<0．05)。OICPC组在8周腱-骨间可见大量Sharpey纤维形成,12周出现直接连接;而对照组在12周才开始出现Sharpey纤维。结论OICPC对肌腱在骨隧道内愈合有明显的促进作用。     

自体半腱肌复合骨形态发生蛋白和同种异体骨重建前交叉韧带后腱-骨愈合的生物力学研究

目的研究骨形态发生蛋白(BMP)复合同种异体骨(DPB)对自体半腱肌肌腱重建前交叉韧带后腱-骨愈合的影响。方法取64只成年新西兰大白兔,分成4组,建立左侧膝前交叉韧带(ACL)完全断裂模型。重建ACL时,于股骨隧道内分别植入BMP结合DPB、BMP、DPB。结果术后3、6、12及24周BMP结合DPB腱-骨愈合及移植物抗拉强度大于其他各治疗组,P<0.05。结论缓释载体DPB能延长BMP作用时间,提高移植物生物力学特性,拮抗骨吸收因子的负面效应,促进腱-骨愈合。     

促进前交叉韧带重建术后腱-骨愈合的方法学进展

近年来,应用肌腱移植物（如腘绳肌腱）行前交叉韧带重建术越来越普遍。手术的远期疗效关键取决于肌腱移植物能否在骨隧道内获得可靠的腱-骨愈合,腱-骨界面开始仅通过一些Sharpey样纤维连接,其在力学上逊于正常的纤维软骨连接,之后肌腱移植物在骨隧道内需要相当长时间才能获得可靠的腱-骨愈合。因此,在没有获得可靠的腱-骨愈合前,腱-骨界面被认为是＂弱点＂,肌腱移植物容易产生滑移甚至从骨隧道内拔出,最终导致手术失败。因此,如何促进腱-骨愈合是目前研究的热点。本文对相关文献做一综述,重点关注应用于骨隧道局部的一些方法学进展。其中干细胞技术、生长因子的局部应用、基因转染技术以及炎症反应的生物调控技术等均已获得令人振奋的研究成果。生物活性骨水泥的应用以及物理治疗方法也取得可喜的成果。组织工程技术可能成为降低供区并发症的方法 ,尽管目前的研究成果令人鼓舞,但仅基于动物实验,应用于临床实践尚需进一步随机对照临床研究。     

Enveloping the tendon graft with periosteum to enhance tendon-bone healing in a bone tunnel: A biomechanical and histologic study in rabbits

Purpose: Fixing and incorporating the tendon graft within the bone tunnel is a major concern when using grafts for ligament reconstruction. The periosteum contains multipotent stem cells and has the potential to form osteogenic and chondrogenic tissues. This study uses histologic and biomechanical analyses to examine the effect of periosteum on tendon-bone healing within a bone tunnel. Type of Study: Experimental study in an animal model. Methods: In this study, 36 adult New Zealand White rabbits were used. The long digitorum extensor tendon was transplanted into a bone tunnel of the proximal tibia. The periosteum from the proximal tibia was sutured on the surface of the tendon portion. The tendon was pulled through a drill-hole in the proximal tibia and attached to the medial aspect of the tibia. Histologic examination of the tendon-bone interface and biomechanical test for maximal pullout load were evaluated at 4, 8, and 12 weeks after operation. Results: Histologic analysis of the tendon-bone interface showed a fibrous layer formed between the tendon and the bone by the periosteum. This layer became progressively integrated with the tendon and bone surface during the healing process. At 4 weeks, the cancellous bone lining in the bone tunnel was interdigitated with the fibrous interface tissue. At 8 weeks, progressive new bone grew into the interface fibrous layer. At 12 weeks, collagen fibers anchored to the bone and organization with fibrocartilage formation developed between the tendon and bone. Biomechanical testing revealed higher maximal pullout strength in the periosteum-enveloped group at all time points, with a statistically significant difference at 8 and 12 weeks. The periosteum-treated group had a higher interface strength-to-length ratio and significant increase at 8 weeks and 12 weeks. Conclusions: The histologic and biomechanical studies demonstrated that, if periosteum was sutured on the tendon that was transplanted within a bone tunnel, it resulted in a superior healing process and better healed strength. When doing ligament reconstruction with a tendon graft, the periosteum can be sutured to the graft to enhance tendon-bone healing.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 3 (March), 2003: pp 290–296     

三七总皂苷促进腱骨愈合的实验研究

目的：研究三七总皂苷对腱骨愈合的影响。方法：取20只成年新西兰大白兔,随机分为PNS组及空白对照组,每组10只。两组动物均切断双侧膝关节前交叉韧带,以趾长伸肌腱重建前交叉韧带,制作腱骨愈合模型。PNS组骨隧道内注射三七总皂苷注射液,干预腱骨愈合。空白对照组不予干预措施。术后4周及8周每组各处死5只新西兰大白兔,获取腱骨愈合标本。通过肉眼、组织学切片观察两组腱骨愈合的变化及差异。结果：顺利完成所有手术,20只大白兔无死亡及关节感染。大体观察,两组动物4周时腱骨界面为纤维连接,8周时腱骨间隙已不容易辨认。组织学观察,PNS组腱骨界面细胞成熟度更高,sharphy纤维生长更加密集,间质钙化程度更高,新骨形成量更多。8周时界面组织形态分类,两组分布差异有统计学意义。结论：三七总皂苷能够促进腱骨界面细胞成熟,促进腱骨界面胶原生长,促进新骨形成,加快腱骨愈合速度,提高腱骨愈合质量。但本研究尚未对各项指标进行定量测量,三七总皂苷促进腱骨愈合的详细机制尚未完全明确。     

富血小板血浆复合物对腱-骨愈合界面力学性能影响的组织学研究

目的通过对健康成年新西兰大白兔行生物力学拉伸试验后标本的腱骨界面、移植物及其断裂层面进行组织学及组织化学观察,评价富血小板血浆(platelet rich plasma,PRP)复合异体脱蛋白骨(deproteined bone,DPB)对前交叉韧带(anterior cruciate ligament,ACL)重建后腱骨愈合的影响。方法 36只成年新西兰大白兔,随机分为3组,每组12只:富血小板血浆复合异体脱蛋白骨组(PRP+DPB组),异体脱蛋白骨组(DPB组),空白对照组。建立双侧自体单股半腱肌肌腱重建ACL模型,前2组骨隧道内分别植入PRP凝胶与DPB复合物、DPB,空白对照组行单纯ACL重建。术后4、8、12、24周取材行生物力学测试(单一轴向的拉伸试验)后,采用HE、Alcian blue、Masson染色及VEGF免疫组织化学观察各组腱骨愈合、移植物及其断裂层面组织学特点,分析各自的力学薄弱点。结果行拉伸试验后,术后4、8周各组标本肌腱移植物均从股骨隧道内断裂拉出,但PRP+DPB组术后8周时标本肌腱断裂处靠近股骨隧道内口,DPB组及空白对照组断裂部位位于隧道中段。术后12周时PRP+DPB组6个标本中有5个肌腱断裂部位在关节腔内部分,另2组仍从隧道内断裂拉出。术后24周时各组标本均在关节腔内部分断裂。组织学观察:术后4周时PRP+DPB组HE染色见断裂层面在腱骨结合部,可见少许疏松的纤维组织,Alcian blue染色未见细胞异染,Masson染色见肌腱断端纤维排列紊乱,VEGF免疫组化染色见较多阳性细胞表达;DPB组及空白对照组断裂层面在腱骨界面,断端见瘢痕组织。术后8周时PRP+DPB组HE染色见断裂层面在隧道内口处腱骨结合部,可见较致密的纤维结缔组织,Alcian blue染色未见细胞异染,Masson染色见肌腱断端纤维排列较前规则,VEGF免疫组化染色仍有较多阳性细胞表达,但较之前少;DPB组及空白对照组在靠近隧道中段处腱骨界面断裂,断端见疏松纤维组织。术后12周时PRP+DPB组肌腱断端见胶原纤维排列较前有序,梭形细胞散在分布,Alcian blue染色见断端有少量细胞异染,VEGF免疫组化阳性细胞数量少;DPB组及空白对照组在靠近隧道内口处腱骨界面断裂,断端见较致密的纤维组织,肌腱断端纤维排列紊乱,Alcian blue染色未见异染。术后24周时各组断端纤维排列整齐,PRP+DPB组可见椭圆形细胞,Alcian blue染色呈异染,较另2组明显,VEGF免疫组化3组均难以检出。术后4、8、12周,PRP+DPB组VEGF表达与DPB组、空白对照组有显著性差异(P<0.05),即表达增强;DPB组与空白对照组各时间点VEGF表达差异无统计学意义(P>0.05);术后24周3组标本的VEGF表达差异无统计学意义(P>0.05)。结论 ACL重建术后早期(8周以内)的薄弱点在腱骨界面,晚期在于移植肌腱。PRP可以提高腱骨间骨向肌腱内长入,从而增加腱骨愈合后的抗拉伸力。     

Effects of trypsinization and mineralization on intrasynovial tendon allograft healing to bone

The purpose of the current study was to develop a novel technology to enhance tendon‐to‐bone interface healing by trypsinizing and mineralizing (TM) an intrasynovial tendon allograft in a rabbit bone tunnel model. Eight rabbit flexor digitorum profundus (FDP) tendons were used to optimize the trypsinization process. An additional 24 FDP tendons were stratified into control and TM groups; in each group, 4 tendons were used for in vitro evaluation of TM and 8 were transplanted into proximal tibial bone tunnels in rabbits. The samples were evaluated histologically and with mechanical testing at postoperative week 8. Maximum failure strength and linear stiffness were not significantly different between the control and TM tendons. A thin fibrous band of scar tissue formed at the graft‐to‐bone interface in the control group. However, only the TM group showed obvious new bone formation inside the tendon graft and a visible fibrocartilage layer at the bone tunnel entrance. This study is the first to explore effects of TM on the intrasynovial allograft healing to a bone tunnel. TM showed beneficial effects on chondrogenesis, osteogenesis, and integration of the intrasynovial tendon graft, but mechanical strength was the same as the control tendons in this short‐term in vivo study. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:468–474, 2015.     

The effect of shock wave treatment at the tendon-bone interface-an histomorphological and biomechanical study in rabbits.

PURPOSE: This study was performed to investigate the effect of shock wave treatment on the healing at tendon-bone interface in rabbits. MATERIALS AND METHODS: Thirty-six New Zealand White rabbits were used in this study. The anterior cruciate ligament was excised and replaced with the long digital extensor. The right knees (study group) were treated with 500 impulses of shock waves at 14 kV, while the left knees (control group) received no shock waves. Histomorphological studies were performed in 24 rabbits at 1, 2, 4, 8, 12 and 24 weeks. Biomechanical studies were performed in 12 rabbits at 12 and 24 weeks. RESULTS: There was significantly more trabecular bone around the tendons noted in the study group compared with the control group at different time intervals after 4 weeks (P<0.05). The contacting between bone and tendon was significantly better in the study group than the control group after 8 weeks (P<0.05). The tensile strength of the tendon-bone interface was significantly higher in the study group than the control group at 24 weeks (P=0.018), whereas similar modes of graft failure were noted between the two groups. CONCLUSION: Shock wave treatment significantly improves the healing rate of the tendon-bone interface in a bone tunnel in rabbits. The effect of shock waves appears to be time-dependent.     

The effect of osteoprotegerin on tendon-bone healing after reconstruction of the anterior cruciate ligament: a histomorphological and radiographical study in the rabbit

AIM: Improvement of the bony incorporation of a soft-tissue graft after ACL reconstruction by local administration of Osteoprotegerin between the bone and tendon graft. METHOD: Fifteen New Zealand White rabbits underwent unilateral anterior cruciate ligament (ACL) reconstruction using an autologous semitendinosis tendon graft. We compared the effect of three OPG doses (5 microg, 50 microg, or 100 microg) at the tendon-bone interface to the controls (OPG carrier) and ACL reconstruction only. Specimens were analyzed at 3 weeks using radiology, histology and histomorphometry to investigate the effect of OPG on the bony incorporation of the tendon graft. RESULTS: Animals treated with OPG 100 microg had a significant (p = 0.007) increase in newly-formed bone around the graft compared to the control group (0.16 +/- 0.01 mm(2); 0.06 +/- 0.02 mm(2)). No significant differences were found between the controls and the other groups (tendon graft only, OPG 5 microg, and 50 microg) (p > 0.05). Bone mineral density, measured in image-pixel brightness (IPB; reference range: 0-255), along the edge of the bone tunnel was greater in the OPG 100 microg group (169.5 +/- 5.9 IPB) compared to the control group (150.3 +/- 4.3 IPB) but this was not statistically significant (p = 0.083). There was a significant decrease in the number of osteoclasts per high-power microscopic fields (HPF) lining the bone tunnel in the OPG 100 microg group compared to the control group (4.4 +/- 2.5 cells/HPF; 6.4 +/- 1.8 cells/HPF) (p = 0.022). No significant differences were found between the control group and the other groups in osteoclast numbers (p > 0.05). CONCLUSION: Since tendon-bone healing requires new bone formation and bone ingrowth around a tendon graft, OPG may improve biologic graft fixation. A potential implication could be earlier return to function or better conditions in revision surgery.     

Potential mechanisms of a periosteum patch as an effective and favourable approach to enhance tendon-bone healing in the human body

Tendon-bone healing is a progressive and complex pathophysiological process after tendon graft transplantation into a bone tunnel. A fibrous scar tissue layer forms at the graft-bone interface, which means a weak bonding of the graft in the bone tunnel. Periosteum, a favourable autologous tissue, was confirmed to be effective in promoting tendon-bone healing in the human body. The advantages of a periosteum patch for tendon-bone repair include the fact that this tissue meets the three primary requirements for tissue engineering: a source of progenitor cells, a scaffold for recruiting cells and growth factors, and a source of local growth factors. Furthermore, the periosteum can prevent graft micromotion, alleviate inflammation and deter bone resorption. In this review, we highlight the role of progenitor cells in the periosteum, which contribute to the regeneration of new bone and/or fibrocartilage at the tendon-bone interface. In summary, the periosteum has shown significant potential for use in the enhancement of graft-bone healing. Our investigations may provoke further studies on the management of allograft-bone healing and artificial ligament graft healing using a periosteum patch in future.     

Macrophages accumulate in the early phase of tendon–bone healing

A scar tissue interface forms rather than a normal ligament insertion site following attachment of a tendon graft to bone. The specific cell types that initiate the process of tendon-to-bone healing are unknown. We hypothesized that inflammatory cell accumulation following tendon-to-bone repair results in this scar interface. We used a rodent model to examine the temporal and spatial pattern of accumulation of hematopoietic lineage cells in the early phase of tendon-to-bone healing. Thirty-six Lewis rats underwent anterior cruciate ligament (ACL) reconstruction in the left knee using a flexor digitorum longus tendon graft. Six animals were sacrificed at 4, 7, 11, 14, 21, and 28 days after surgery. Serial sections were analyzed for proliferating cells (PCNA), recruited macrophages (ED1), resident macrophages (ED2), neutrophils, T-lymphocytes (CD3), mast cells, immature progenitor cells/pericytes (expressing the NG2 cell-surface chondroitin sulfate proteoglycan), and newly-formed blood vessels (Factor VIII). Neutrophils, ED1(+) and ED2(+) macrophages accumulated sequentially in the healing tendon graft, with progressive cell ingrowth from the interface towards the inner tendon. Neutrophils and ED1(+) cells were seen in the tendon-bone interface at 4 days after surgery, while ED2(+) macrophages were not identified until 11 days. These cells progressively repopulated the tendon graft. NG2-positive progenitor cells were found along the edge of the bone tunnel in the interface, but these cells did not invade the tendon. Occasional T-lymphocytes and mast cells were seen in the tendon-bone interface. There was no proliferation of intrinsic tendon cells, indicating that the tendon does not directly contribute to healing. We hypothesize that cytokines produced by infiltrating macrophages are likely to contribute to the formation of a fibrous scar tissue interface rather than a normal insertion site.