INFERIOR DISLOCATION OF THE
SHOULDER (LUXATIO ERECTA)
Inferior dislocation is rare but it demands early recognition because the consequences are potentially very serious. Dislocation occurs with the arm in nearly full abduction/elevation. The humeral head is levered out of its socket and pokes into the axilla; the arm remains fixed in abduction.
Mechanism of injury and pathology
The injury is caused by a severe hyperabduction force. With the humerus as the lever and the acromion as the fulcrum, the humeral head is lifted across the inferior rim of the glenoid socket; it remains in the subglenoid position, with the humeral shaft pointing upwards. Softtissue injury may be severe and includes avulsion of the capsule and surrounding tendons, rupture of muscles, fractures of the glenoid or proximal humerus and damage to the brachial plexus and axillary artery.
Clinical features
The startling picture of a patient with his arm locked in almost full abduction should make diagnosis quite easy. The head of the humerus may be felt in or below the axilla. Always examine for neurovascular damage.
X-ray
The humeral shaft is shown in the abducted position with the head sitting below the glenoid. It is important to search for associated fractures of the glenoid or proximal humerus.
NOTE: True inferior dislocation must not be confused with postural downward displacement of the humerus, which results quite commonly from weakness and laxity of the muscles around the shoulder, especially after trauma and shoulder splintage; here the shaft of the humerus lies in the normal anatomical position at the side of the chest. The condition is harmless and resolves as muscle tone is regained.
Treatment
Inferior dislocation can usually be reduced by pulling upwards in the line of the abducted arm, with counter-traction downwards over the top of the shoulder. If the humeral head is stuck in the soft tissues, open reduction is needed. It is important to examine again, after reduction, for evidence of neurovascular injury.
The arm is rested in a sling until pain subsides and movement is then allowed, but avoiding abduction for 3 weeks to allow the soft tissues to heal.
---from 《Apley’s System of Orthopaedics and Fractures》
重点词汇整理：
Inferior /ɪnˈfɪriər/n. 下级；次品adj. 差的；自卑的；下级的，下等的
recognition/ˌrekəɡˈnɪʃn/n. 识别；承认，认出；重视；赞誉；公认
socket /ˈsɑːkɪt/n. 插座；窝，穴；牙槽
poke /poʊk/n. 戳；刺；袋子；懒汉vt. 刺，捅；戳；拨开
axilla /æk'silə/n. [解剖] 腋窝，[解剖] 腋下；咯肢窝
hyperabduction外展过度
fulcrum /ˈfʊlkrəm,ˈfʌlkrəm/n. [机][力] 支点；叶附属物
avulsion /ə'vʌlʃən/n. 扯开，撕裂；扯离的部分
brachial plexus 臂丛；[解剖] 臂神经丛；肱神经丛
neurovascular damage.神经与血管的损伤。
postural /ˈpɑːstʃərəl/adj. 姿势性的，位置的；心态的
百度翻译：
下脱位肩部（卢萨蒂奥·埃雷塔）
下位错是罕见的，但它需要早期认识，因为其后果可能非常严重。手臂几乎完全外展/抬高时发生脱位。肱骨头被撬出窝，伸入腋窝；手臂在外展时保持固定。
损伤机制与病理
受伤是由严重的过度外展力造成的。以肱骨为杠杆，肩峰为支点，肱骨头抬过肩胛窝下缘，保持在肩胛下位置，肱骨干向上。软组织损伤可能很严重，包括包膜和周围肌腱撕裂、肌肉破裂、肱骨近端或肩胛骨骨折以及臂丛和腋动脉损伤。
临床特征
一个病人的手臂几乎完全被绑架，这张令人吃惊的照片应该使诊断变得非常容易。肱骨头部可在腋窝内或腋下感觉到。经常检查神经血管损伤。
X射线
肱骨干显示为外展位，头部位于肩胛下。重要的是寻找相关的肩胛盂或肱骨近端骨折。
注意：真正的下脱位不能与肱骨的姿势性向下移位相混淆，这通常是由于肩关节周围肌肉的无力和松弛引起的，特别是在外伤和肩关节夹板固定后；这里肱骨的轴位于胸侧的正常解剖位置。这种情况是无害的，随着肌肉张力的恢复而消失。
治疗
下脱位通常可以通过向上拉外展手臂的线条来减少，并在肩部上方向下反向牵引。如果肱骨头卡在软组织中，就需要切开复位。重要的是在复位后再次检查，以寻找神经血管损伤的证据。
手臂外展可以休息3周，直到软组织愈合。
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