骨科英文书籍精读（97）｜肱骨髁上骨折（1）
SUPRACONDYLAR FRACTURES
These are among the commonest fractures in children. The distal fragment may be displaced either posteriorly or anteriorly.
Mechanism of injury
Posterior angulation or displacement (95 per cent of all cases) suggests a hyperextension injury, usually due to a fall on the outstretched hand. The humerus breaks just above the condyles. The distal fragment is pushed backwards and (because the forearm is usually in pronation) twisted inwards. The jagged end of the proximal fragment pokes into the soft tissues anteriorly, sometimes injuring the brachial artery or median nerve.
Anterior displacement is rare; it is thought to be due to direct violence (e.g. a fall on the point of the elbow) with the joint in flexion.
Classification
Type I is an undisplaced fracture.
Type II is an angulated fracture with the posterior cortex still in continuity.
IIA – a less severe injury with the distal fragment merely angulated.
IIB – a severe injury; the fragment is both angulated and malrotated.
Type III is a completely displaced fracture (although the posterior periosteum is usually still preserved, which will assist surgical reduction).
Clinical features
Following a fall, the child is in pain and the elbow is swollen; with a posteriorly displaced fracture the S-deformity of the elbow is usually obvious and the bony landmarks are abnormal. It is essential to feel the pulse and check the capillary return; passive extension of the flexor muscles should be pain-free. The wrist and the hand should be examined for evidence of nerve injury.
X-ray
The fracture is seen most clearly in the lateral view. In an undisplaced fracture the ‘fat pad sign’ should raise suspicions: there is a triangular lucency in front of the distal humerus, due to the fat pad being pushed forwards by a haematoma.
In the common posteriorly displaced fracture the fracture line runs obliquely downwards and forwards and the distal fragment is tilted backwards and/or shifted backwards. In the anteriorly displaced fracture the crack runs downwards and backwards and the distal fragment is tilted forwards. On a normal lateral x-ray, a line drawn along the anterior cortex of the humerus should cross the middle of the capitulum. If the line is anterior to the capitulum then a Type II fracture is suspected.
An anteroposterior view is often difficult to obtain without causing pain and may need to be postponed until the child has been anaesthetized. It may show that the distal fragment is shifted or tilted sideways, and rotated (usually medially). Measurement of Baumann’s angle is useful in assessing the degree of medial angulation before and after reduction (Fig. 24.30).
---from 《Apley’s System of Orthopaedics and Fractures》
重点词汇整理：
jagged /ˈdʒæɡɪd/adj. 锯齿状的；参差不齐的v. 使成缺口；使成锯齿状（jag的过去式）
capillary return;毛细血管回流 /ˈkæpəleri/n. 毛细血管；毛细管；微血管adj. 毛细管的；毛状的；表面张力的
suspicion /səˈspɪʃn/n. 怀疑；嫌疑；疑心；一点儿vt. 怀疑
lucency /'lju:sənsi/n. 透明；光亮
fat pad脂肪垫
In the common posteriorly displaced fracture the fracture line runs obliquely downwards and forwards and the distal fragment is tilted backwards and/or shifted backwards.在常见的后移位骨折中，骨折线倾斜地向前和向下移动，远端碎片向后倾斜和/或向后移动。
capitulum/kə'pɪtʃʊləm/n. 肱骨小头
百度翻译：
髁上骨折
这是儿童最常见的骨折之一。远端碎片可向后或向前移位。
损伤机制
后部成角或移位（95%的病例）表明是过度伸展损伤，通常是由于伸直的手摔倒造成的。肱骨在髁突上方断裂。远端的碎片向后推（因为前臂通常是旋前的）向内扭曲。近端骨块锯齿状的一端伸入前方软组织，有时损伤肱动脉或正中神经。
前移是罕见的；它被认为是由于直接暴力（如摔倒在肘部的点）和关节屈曲。
分类
Ⅰ型是不移位骨折。
后皮质仍呈角型连续性骨折。
IIA–远端骨折仅成角度的较轻损伤。
IIB–严重损伤；碎片有角度和旋转错误。
III型骨折是完全移位的骨折（尽管后骨膜通常仍然保留，这将有助于手术复位）。
临床特征
跌倒后，孩子疼痛，肘关节肿胀；后移位骨折，肘关节S形畸形通常很明显，骨标志异常。感觉脉搏和检查毛细血管回流是很重要的；屈肌的被动伸展应该是无痛的。手腕和手应该检查神经损伤的证据。
X射线
从侧面看骨折最清楚。在未移位的骨折中，“脂肪垫征”应该引起怀疑：由于血肿将脂肪垫向前推，肱骨远端前方有三角形透光。
在常见的后移位骨折中，骨折线斜向下和向前延伸，远端骨折片向后倾斜和/或向后移位。在前移骨折中，裂纹向下和向后延伸，远端碎片向前倾斜。在正常的侧位x光片上，沿着肱骨前皮质画的线应该穿过小头的中间。如果线在小头前，则怀疑为Ⅱ型骨折。
在不引起疼痛的情况下，通常很难获得正位视图，可能需要推迟到孩子麻醉后才行。这可能表明远端的碎片移位或倾斜，并旋转（通常是在中间）。Baumann角的测量有助于评估复位前后内侧成角的程度（图24.30）。