骨科英文书籍精读（4）｜骨折愈合的分子机制
HEALING BY CALLUS
This is the ‘natural’ form of healing in tubular bones; in the absence of rigid fixation, it proceeds in five stages:
1. Tissue destruction and haematoma formation – Vessels are torn and a haematoma forms around and within the fracture. Bone at the fracture surfaces, deprived of a blood supply, dies back for a millimetre or two.
2. Inflammation and cellular proliferation – Within 8 hours of the fracture there is an acute inflammatory reaction with migration of inflammatory cells and the initiation of proliferation and differentiation of mesenchymal stem cells from the periosteum, the breached medullary canal and the surrounding muscle. The fragment ends are surrounded by cellular tissue, which creates a scaffold across the fracture site. A vast array of inflammatory mediators (cytokines and various growth factors) is involved. The clotted haematoma is slowly absorbed and fine new capillaries grow into the area.
3. Callus formation – The differentiating stem cells provide chrondrogenic and osteogenic cell populations; given the right conditions – and this is usually the local biological and biomechanical
environment – they will start forming bone and, in some cases, also cartilage. The cell population now also includes osteoclasts (probably derived from the new blood vessels), which begin to mop up dead bone. The thick cellular mass, with its islands of immature bone and cartilage, forms the callus or splint on the periosteal and endosteal surfaces. As the immature fibre bone (or ‘woven’ bone) becomes more densely mineralized, movement at the fracture site decreases progressively and at about 4 weeks after injury the fracture ‘unites’.
4. Consolidation – With continuing osteoclastic and osteoblastic activity the woven bone is transformed intolamellar bone. The system is now rigid enough to allow osteoclasts to burrow through the debris at the fracture line, and close behind them. Osteoblasts fill in the remaining gaps between the fragments with new bone. This is a slow process and it may be several months before the bone is strong enough to carry normal loads.
5. Remodelling – The fracture has been bridged by a cuff of solid bone. Over a period of months, or even years, this crude ‘weld’ is reshaped by a continuous process of alternating bone resorption and formation. Thicker lamellae are laid down where the stresses are high, unwanted buttresses are carved away and the medullary cavity is reformed. Eventually, and especially in children, the bone reassumes something like its normal shape.
---from 《Apley’s System of Orthopaedics and Fractures》P690
重点词汇整理：
tubular bones 管状骨
rigid fixation 坚强固定
it proceeds in five stages:它分五个阶段进行
haematoma /,hi:mə'təumə, ,hem-/n. [病理] 血肿
Vessels are torn 血管撕裂
torn/tɔːrn/vt. 撕开；撕掉；扯破（tear 的过去分词）
deprived /dɪˈpraɪvd/adj. 贫困的严重匮乏的
millimetre /ˈmɪlimiːtər/n. 毫米；千分之一米
Inflammation and cellular proliferation炎症和细胞增殖
acute inflammatory reaction急性炎症反应
migration /maɪˈɡreɪʃn/n. 迁移；移民；移动
proliferation /prəˌlɪfəˈreɪʃn/n. 增殖，扩散；分芽繁殖
differentiation of mesenchymal stem cells 间充质干细胞的分化
differentiation /ˌdɪfəˌrenʃiˈeɪʃn/n. 变异， 分化；区别
mesenchymal/mɛs'ɛŋkɪməl/adj. 间叶细胞的；由间叶细胞组成的；间叶细胞样的
breached medullary canal 髓腔破裂
breached /briːtʃ/n. 违背，违反；缺口vt. 违反，破坏；打破
scaffold /ˈskæfoʊld/n. 支架；脚手架；鹰架；绞刑台
A vast array of inflammatory mediators (cytokines and various growth factors) is involved. 大量的炎症介质(细胞因子和各种生长因子)参与其中。
mediator/ˈmiːdieɪtər/n. 调停者；传递者；中介物
cytokines /'saitəu,kains/细胞因子
The clotted haematoma is slowly absorbed and fine new capillaries grow into the area.凝结的血肿慢慢被吸收，细小的新毛细血管生长到该区域。
capillary /ˈkæpəleri/n. 毛细血管
chrondrogenic 缓慢产生的
chondrogenic cell 成软骨细胞
osteogenic cell 成骨细胞
Osteoblast /'ɑstɪəblæst/成骨细胞
biomechanical /,baɪəʊmə'kænɪkəl/生物力学
cartilage /ˈkɑːrtɪlɪdʒ/n. 软骨
osteoclast /'ɑstɪəklæst /n. [组织] 破骨细胞；[外科] 折骨器
Osteoblast /'ɑstɪəblæst/n.成骨细胞
derived from 来源于
mop up 擦；用拖把拖洗;清理
immature /ɪməˈtʊr/adj. 不成熟的；未成熟的；粗糙的
callus or splint 骨痂（均可表示骨痂）
periosteal and endosteal surfaces. 骨膜和内膜表面。
periosteal/,peri'ɔstiəl/adj. 骨膜的
endosteal /en'dɔstiəl/adj. 位于骨内的；骨内膜的
woven /ˈwoʊvn/n. 机织织物v. 编织；交织（weave的过去分词）adj. 编织的
densely mineralized 密集的矿化/'mɪnərəlaɪzd/
Consolidation /kənˌsɑːlɪˈdeɪʃn/n. 巩固；合并；团结
is transformed into lamellar bone 转换为板层骨/lə'melə/adj. 薄片状的，薄层状的
burrow /ˈbɜːroʊ/n. （动物的，尤指兔子挖的）洞穴，地洞v. 挖地洞，
Osteoblast /'ɑstɪəblæst/n.成骨细胞
Remodelling （建筑物的形状或结构的）改造，重建v. 改变……的结构（或形状）；重新做；重塑
a cuff of 一节...
cuff/kʌf/n. 袖口
alternating bone resorption and formation.骨吸收和形成的交替。
Thicker lamellae are laid down where the stresses are high, 较厚的层板分布在应力较大的地方
lamellae n. 骨板；片晶；薄片，薄层；（真菌的）菌褶 （lamella 的复数）
unwanted buttresses are carved away and the medullary cavity is reformed.多余的骨痂被凿去，髓腔被改造。
buttress /ˈbʌtrəs/n. 山边扶壁状凸出部分
reassume /,riə'sʊm/vt. 再假定；再采取；再承担
百度翻译：
骨痂愈合
这是管状骨愈合的“自然”形式；在没有刚性固定的情况下，它分五个阶段进行：
一。组织破坏和血肿形成-血管撕裂，骨折周围和内部形成血肿。骨折表面的骨头，失去血液供应，会向后死亡一两毫米。
2。炎症和细胞增殖-骨折后8小时内出现急性炎症反应，炎症细胞迁移，间充质干细胞从骨膜、破裂的髓管和周围肌肉开始增殖和分化。碎片的末端被细胞组织包围，在骨折处形成一个支架。大量的炎症介质（细胞因子和各种生长因子）参与其中。凝固的血肿被缓慢吸收，细小的新毛细血管长入该区域。
三。愈伤组织的形成-分化的干细胞提供了成骨细胞和成时细胞群；在适当的条件下-这通常是局部的生物学和生物力学
环境-他们将开始形成骨头，在某些情况下，也软骨。细胞群现在也包括破骨细胞（可能来自新的血管），它们开始清理死骨。厚实的细胞团，由未成熟的骨头和软骨组成，在骨膜和骨内膜表面形成骨痂或夹板。随着未成熟纤维骨（或“编织”骨）变得更加密集矿化，骨折部位的运动逐渐减少，在损伤后4周左右骨折“愈合”。
四。巩固-随着破骨细胞和成骨细胞的持续活动，编织骨转化为板层骨。这个系统现在已经足够坚硬，可以让破骨细胞钻穿骨折线的碎片，并紧跟在碎片后面。成骨细胞用新骨填充碎片之间的剩余间隙。这是一个缓慢的过程，可能需要几个月的时间，骨骼才能足够强壮，能够承受正常的负荷。
5个。重建-骨折被一个坚固的骨袖套桥接。经过几个月，甚至几年的时间，这个粗糙的“焊缝”被不断交替的骨吸收和形成过程重塑。较厚的板层被放置在应力较高的地方，多余的扶壁被雕刻掉，髓腔被改造。最终，尤其是在儿童中，骨头恢复了正常的形状。