ACROMIOCLAVICULAR JOINT INJURIES
Acute injury of the acromioclavicular joint is common and usually follows direct trauma. Chronic sprains, often associated with degenerative changes, are seen in people engaged in athletic activities like weightlifting or occupations such as working with jack-hammers and other heavy vibrating tools.
Mechanism of injury
A fall on the shoulder with the arm adducted may strain or tear the acromioclavicular ligaments and upward subluxation of the clavicle may occur; if the force is severe enough, the coracoclavicular ligaments will also be torn, resulting in complete dislocation of the joint.
Pathological anatomy and classification
The injury is graded according to the type of ligament injury and the amount of displacement of the joint.
Type I is an acute sprain of the acromioclavicular ligaments; the joint is undisplaced. In Type II the acromioclavicular ligaments are torn and the joint is subluxated with slight elevation of the clavicle. In Type III the acromioclavicular and coracoclavicular ligaments are torn and the joint is dislocated; the clavicle is elevated (or the acromion depressed) creating a visible and palpable ‘step’. Other types of displacement are less common, but occasionally the clavicle is displaced posteriorly (Type IV), very markedly upwards (Type V) or inferiorly beneath the coracoid process (Type VI).
Clinical features
The patient can usually point to the site of injury and the area may be bruised. If there is tenderness but no deformity, the injury is probably a sprain or a subluxation. With dislocation the patient is in severe pain
and a prominent ‘step’ can be seen and felt. Shoulder movements are limited.
X-ray
The acromioclavicular joint is not always easily visualized; anteroposterior, cephalic tilt and axillary views are advisable. In addition, a stress view is sometimes helpful in distinguishing between a Type II and Type III injury: this is an anteroposterior x-ray including both shoulders with the patient standing upright, arms by the side and holding a 5 kg weight in each hand. The distance between the coracoid process and the inferior border of the clavicle is measured on each side; a difference of more than 50 percent is diagnostic of acromioclavicular dislocation.
---from 《Apley’s System of Orthopaedics and Fractures》
重点词汇整理：
acromioclavicular /ə,krəumiəuklə'vikjulə/adj. 肩锁的
sprain /spreɪn/n. 扭伤
degenerative change退行性病变
engaged in从事于；忙于
occupation /ˌɑːkjuˈpeɪʃn/n. 职业；占有；消遣；占有期
jack 千斤顶
jack-hammers 凿岩机
vibrating tools振动工具
vibrate /ˈvaɪbreɪt/vt. 使振动；使颤动vi. 振动；颤动；摇摆；踌躇
adduct/'ædʌkt/n. [化学] 加合物vt. 使内收
subluxation /,sʌblʌk'seiʃən/n. [外科] 半脱位；不全脱位
undisplaced无移位的
inferior/ɪnˈfɪriər/n. 下级；次品adj. 差的；自卑的；下级的，下等的
deformity/dɪˈfɔːrməti/n. 畸形；畸形的人或物；道德方面的缺陷
prominent /ˈprɑːmɪnənt/adj. 突出的，显著的；杰出的；卓越的
anteroposterior /,ætərəupɔs'tiəriə/adj. 前后的
cephalic tilt头倾斜 /sɪˈfælɪk/adj. [动] 头的
axillary views腋位像 /'æksɪ,lɛri/n. [鸟] 腋羽adj. [植] 腋生的；腋窝的；叶腋的
stress view应力位像
百度翻译：
肩锁关节损伤
急性肩锁关节损伤是常见的，通常发生在直接损伤后。慢性扭伤，通常与退行性改变有关，见于从事举重等体育活动或使用千斤顶和其他重型振动工具等职业的人。
损伤机制
手臂内收的肩关节跌倒可能拉伤或撕裂肩锁韧带，锁骨可能向上半脱位；如果力量足够大，也可能撕裂喙锁韧带，导致关节完全脱位。
病理解剖与分类
根据韧带损伤类型和关节移位量对损伤进行分级。
I型为肩锁韧带急性扭伤，关节未移位。Ⅱ型患者肩锁韧带撕裂，关节半脱位，锁骨轻度抬高。在III型中，肩锁韧带和喙锁韧带撕裂，关节脱位；锁骨抬高（或肩锁压低），形成可见和可触的“台阶”。其他类型的移位并不常见，但偶尔锁骨后移位（IV型），非常明显地向上移位（V型）或向下移位在喙突下（VI型）。
临床特征
病人通常可以指受伤的部位，该部位可能有瘀伤。如果有压痛但没有畸形，可能是扭伤或半脱位。病人因脱臼而剧痛
可以看到和感觉到一个突出的“台阶”。肩部活动受限。
X射线
肩锁关节并不总是很容易被观察到；最好是前后位、头位倾斜和腋窝位。此外，压力视图有时有助于区分II型和III型损伤：这是一种前后x光片，包括患者直立的双肩，双臂并拢，每只手保持5公斤的重量。喙突与锁骨下缘之间的距离是在每侧测量的；超过50%的差异是对肩锁关节脱位的诊断。
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