EXTERNAL FIXATION
A fracture may be held by transfixing screws or tensioned wires that pass through the bone above and below the fracture and are attached to an external frame. This is especially applicable to the tibia and pelvis, but the method is also used for fractures of the femur, humerus, lower radius and even bones of the hand.
Indications
External fixation is particularly useful for:
1. Fractures associated with severe soft-tissue damage (including open fractures) or those that are contaminated, where internal fixation is risky and repeated access is needed for wound inspection, dressing or plastic surgery.
2. Fractures around joints that are potentially suitable for internal fixation but the soft tissues are too swollen to allow safe surgery; here, a spanning external fixator provides stability until soft-tissue conditions improve.
3. Patients with severe multiple injuries, especially if there are bilateral femoral fractures, pelvic fractures with severe bleeding, and those with limb and associated chest or head injuries.
4. Ununited fractures, which can be excised and compressed; sometimes this is combined with bone lengthening to replace the excised segment.
5. Infected fractures, for which internal fixation might not be suitable.
Technique
The principle of external fixation is simple: the bone is transfixed above and below the fracture with screws or tensioned wires and these are then connected to each other by rigid bars. There are numerous types of external fixation devices; they vary in the technique of application and each type can be constructed to provide varying degrees of rigidity and stability. Most of them permit adjustment of length and alignment after application on the limb.
The fractured bone can be thought of as broken into segments – a simple fracture has two segments whereas a two-level (segmental) fracture has three and so on. Each segment should be held securely, ideally with the half-pins or tensioned wires straddling the length of that segment.
The wires and half-pins must be inserted with care. Knowledge of ‘safe corridors’ is essential so as to avoid injuring nerves or vessels; in addition, the entry sites should be irrigated to prevent burning of the bone (a temperature of only 50ºC can cause bone death).
The fracture is then reduced by connecting the various groups of pins and wires by rods.
Depending on the stability of fixation and the underlying fracture pattern, weightbearing is started as early as possible to ‘stimulate’ fracture healing. Some fixators incorporate a telescopic unit that allows ‘dynamization’; this will convert the forces of weightbearing into axial micromovement at the fracture site, thus promoting callus formation and accelerating bone union (Kenwright et al., 1991).
Complications
Damage to soft-tissue structures Transfixing pins or wires may injure nerves or vessels, or may tether ligaments and inhibit joint movement. The surgeon must be thoroughly familiar with the cross-sectional anatomy before operating.
Overdistraction If there is no contact between the fragments, union is unlikely.
Pin-track infection This is less likely with good operative technique. Nevertheless, meticulous pin-site care is essential, and antibiotics should be administered immediately if infection occurs.
---from 《Apley’s System of Orthopaedics and Fractures》P703-704
重点词汇整理：
transfixingv. （使）（因恐惧、惊愕等而）动弹不得；（用锋利器具、武器）刺穿（transfix 的现在分词）
external frame 外部支架
bilateral /ˌbaɪˈlætərəl/adj. 双边的；有两边的
excised /ek'saizd/离体的；切离的
bone lengthening 骨延长
rigid bars 坚强的棒
external fixation devices外固定支架
rigidity /rɪˈdʒɪdəti/n. [物] 硬度，[力] 刚性；严格，刻板；僵化；坚硬
and so on等等；诸如此类；以此类推
corridors /'kɔrɪdɔrs/n. 廊道，[建] 走廊（corridor的复数形式）
the entry sites should be irrigated to prevent burning of the bone电钻入口部位应该用冷水冲洗，以防止骨头因高温而坏死。
incorporate /ɪnˈkɔːrpəreɪt/vt. 包含，配有；吸收；体现；把……合并
telescopic /ˌtelɪˈskɑːpɪk/adj. 望远镜的；[眼科] 远视的；套管式伸缩的；眼力好的；有先见之明的
axial micromovement 轴向微动
tether /ˈteðər/n. 系链；拴绳v. （用绳或链）拴住
The surgeon must be thoroughly familiar with the cross-sectional anatomy before operating.外科医生在动手术前必须完全熟悉横断面解剖学。
meticulous /məˈtɪkjələs/adj. 一丝不苟的；小心翼翼的；拘泥小节的
antibiotics should be administered immediately if infection occurs.如果发生感染，应立即使用抗生素。
百度翻译：
外固定
骨折可以通过贯穿螺钉或张力钢丝固定，这些螺钉或张力钢丝穿过骨折上方和下方的骨骼并连接到外部框架上。这种方法特别适用于胫骨和骨盆，但也适用于股骨、肱骨、桡骨下段甚至手部骨骼的骨折。
适应症
外固定特别适用于：
一。与严重软组织损伤（包括开放性骨折）相关的骨折或受污染的骨折，其中内固定有风险，需要重复进行伤口检查、敷料或整形手术。
2。关节周围的骨折可能适合内固定，但软组织肿胀，不允许安全手术；这里，一个跨越式外固定器提供稳定性，直到软组织状况改善。
三。严重多发伤患者，尤其是双侧股骨骨折、骨盆骨折伴严重出血、四肢及相关胸部或头部损伤的患者。
四。未愈合的骨折，可以切除和压缩；有时结合骨延长来代替切除的部分。
5个。感染性骨折，可能不适合内固定。
技术
外固定的原理很简单：用螺钉或张力钢丝将骨折的上下贯通，然后用刚性杆将其连接起来。外固定装置有多种类型；它们的应用技术各不相同，每种类型的外固定装置都能提供不同程度的刚度和稳定性。它们中的大多数允许在应用于肢体后调整长度和对齐。
骨折可以被认为是分成几段的——简单骨折有两段，而两级（节段性）骨折有三段，以此类推。每个节段都应牢固地固定，理想情况下，半销或张紧钢丝横跨该节段的长度。
必须小心插入电线和半销。了解“安全走廊”是必要的，以避免损伤神经或血管；此外，入口部位应进行灌溉，以防止骨头燃烧（只有50℃的温度可导致骨头死亡）。
然后，通过棒连接不同组的针和线来减少断裂。
根据固定的稳定性和潜在的骨折模式，尽早开始负重，以“刺激”骨折愈合。一些固定器包含一个允许“动态化”的伸缩装置；这将把承重力转换成骨折部位的轴向微移动，从而促进骨痂形成和加速骨愈合（Kenwright等人，1991）。
难题
穿钉或穿线对软组织结构的损伤可能会损伤神经或血管，或可能拴住韧带并抑制关节运动。手术前，外科医生必须完全熟悉横切面解剖。
过度分散如果碎片之间没有接触，结合是不可能的。
针道感染这是不太可能与良好的手术技术。然而，细致的针位护理是必要的，如果感染发生，应立即使用抗生素。
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