骨科英文书籍精读（47）｜骨折晚期并发症之应力性骨折（1）
STRESS FRACTURES
A stress or fatigue fracture is one occurring in the normal bone of a healthy patient, due not to any specific traumatic incident but to small repetitive stresses of two main types: bending and compression.
Bending stress causes deformation and bone responds by changing the pattern of remodelling. With repeated stress, osteoclastic resorption exceeds osteoblastic formation and a zone of relative weakness develops – ultimately leading to a breach in the cortex. This process affects young adults undertaking strenuous physical routines and is probably due to muscular forces acting on bone. Athletes in training, dancers and military recruits build up muscle power quickly but bone strength only slowly; this accounts for the high incidence of stress fractures in these groups.
Compressive stresses act on soft cancellous bone; with frequent repetition an impacted fracture may result.
A combination of compression and shearing stresses may account for the osteochondral fracures that characterize some of the so-called osteochondritides.
‘Spontaneous fractures’ occur with even greater ease in people with osteoporosis or osteomalacia and in patients treated with drugs that affect bone remodelling in a similar way (e.g. corticosteroids and methotrexate). These are often referred to as insufficiency fractures.
Sites affected
Least rare are the following: shaft of humerus (adolescent cricketers); pars interarticularis of fifth lumbar vertebra (causing spondylolysis); pubic rami (inferior in children, both rami in adults); femoral neck (at any age); femoral shaft (chiefly lower third); patella (children and young adults); tibial shaft (proximal third in 23(a) (b)23.46 Stress fracture (a) The stress fracture in this tibia is only just visible on x-ray, but it had already been suspected 2 weeks earlier when the patient first complained of pain and a radioisotope scan revealed a ‘hot’ area just above the ankle (b). children, middle third in athletes and trainee paratroopers, distal third in the elderly); distal shaft of the fibula (the ‘runner’s fracture’); calcaneum (adults); navicular (athletes) and metatarsals (especially the second).
---from 《Apley’s System of Orthopaedics and Fractures》P724
重点词汇整理：
osteoclastic 破骨细胞的
osteoblastic 成骨细胞的
breach /briːtʃ/n. 违背，违反；缺口vt. 违反，破坏；打破
strenuous/ˈstrenjuəs/adj. 紧张的；费力的；奋发的；艰苦的；热烈的
routine/ruːˈtiːn/n. 常规，惯例；生活乏味；（演出中的）一套动作；（计算机）例行程序adj. 常规的，例行的；平常的；乏味的v. 按惯例安排
recruits /rɪ'krʊts/n. 新兵；新成员（recruit的复数形式）；幼鱼v. 征募；雇佣；恢复健康（recruit的三单形式）
Compressive stresses压应力
impacted fracture 嵌插骨折
shearing stresses剪切应力
osteochondral骨软骨的
osteochondritides骨软骨炎
Spontaneous fractures自发性骨折
osteomalacia /,ɑstɪomə'leʃə/n. [外科] 骨软化；[内科] 软骨病
corticosteroids and methotrexate糖皮质激素和甲氨蝶呤
insufficiency fractures.机能不全骨折
/ˌɪnsəˈfɪʃənsi/n. 不足，不充分；机能不全；不适当
cricketer /ˈkrɪkɪtər/n. 板球队员；玩板球者
spondylolysis /spɔndi'lɔlisis/n峡部裂 滑脱 脊椎滑脱
inferior /ɪnˈfɪriər/n. 下级；次品adj. 差的；自卑的；下级的，下等的
rami /'reimai/n. 支（ramus的复数）
radioisotope scan同位素扫描
/ˌreɪdioʊˈaɪsətoʊp/n. [核] 放射性同位素
trainee /ˌtreɪˈniː/n. 练习生，实习生；受训者；新兵；训练中的动物
paratrooper /ˈpærətruːpər/n. 伞兵
navicular /nə'vɪkjʊlə/ adj. [解剖] 舟状的，船状的n. 舟骨
metatarsal /ˌmetəˈtɑːrsl/n. 跖骨adj. 跖骨的
百度翻译：
应力骨折
应力性或疲劳性骨折是发生在健康患者正常骨骼中的骨折，不是由于任何特定的创伤事件，而是由于两种主要类型的小重复应力：弯曲和压缩。
弯曲应力通过改变重塑模式引起变形和骨反应。在反复的应力作用下，破骨细胞的吸收超过了成骨细胞的形成，形成了一个相对薄弱的区域，最终导致皮质破裂。这一过程影响年轻人进行剧烈的体力活动，可能是由于肌肉力量作用于骨骼。参加训练的运动员、舞蹈演员和新兵的肌肉力量增长很快，但骨骼强度却很慢；这是这些人群中应力性骨折的高发原因。
压缩应力作用在软质松质骨上；如果经常重复，可能会导致阻生骨折。
压缩应力和剪切应力的结合可以解释一些所谓骨软骨潮汐的特征性骨软骨骨折。
“自发性骨折”在骨质疏松症或骨软化症患者和以类似方式影响骨重建的药物（如皮质类固醇和甲氨蝶呤）治疗的患者中更容易发生。这些通常被称为不全性骨折。
受影响的地点
最不罕见的有：肱骨干（青少年板球运动员）；第五腰椎关节间部（引起脊椎峡部裂）；耻骨支（儿童次之，成人双支）；股骨颈（任何年龄）；股骨干（主要是下三分之一）；髌骨（儿童和青年人）；胫骨干（23（a）（b）23.46应力性骨折（a）该胫骨的应力性骨折仅在x光片上可见，但在2周前，当患者首次抱怨疼痛和放射性同位素扫描显示脚踝上方有一个“热”区域（b）时，已经有人怀疑。儿童，运动员和学员伞兵中的第三名，老年人中的第三名；腓骨远端干（跑步者骨折）；跟骨（成人）；舟骨（运动员）和跖骨（特别是第二）。