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下面我们将为大家提供四期连载内容，本文为第一期，包括介绍、相关解剖和生物力学 介绍 肘关节三维结构复杂，容易发生关节僵硬，且关节不稳带来的后果比较严重。有关肘关节周围多发性骨折及软组织损伤的病例多有报道，肘关节脱位合并冠状突和桡骨头骨折之所以获得“恐怖三联征”的称号，主要归因于其治疗困难及预后较差。“恐怖三联征”常导致肘关节周围骨性结构和韧带不稳；因此，治疗必须充分恢复肘关节的稳定性以允许早期功能锻炼，从而避免关节僵直。
相关解剖 肘关节由桡骨、尺骨上端和肱骨下端构成，这三者由肱尺关节、肱桡关节和桡尺近端关节连接（图1）。肱尺关节和肱桡关节属屈戌（铰链）关节，而桡尺近端关节属车轴（枢轴）关节。恐怖三联征会导致肱骨和前臂连接不稳，但很少会破坏尺骨和桡骨（包括前臂骨间膜）之间的稳定性。 Fig.1. Bony landmarks as seen on (A) anteroposterior (AP) and (B) lateral radiographs. 图1 肘关节解剖标记：A为前后位片，B为侧位片。 虽然肘关节与肩关节都由肱骨参与组成，但肘关节不同于肩关节。相比于简单的球形盂肱关节及其复杂的周围软组织稳定结构，肘关节的三维骨性解剖较复杂，而其软组织结构（包括内外侧副韧带和前后部关节囊）则相对简单。
内侧副韧带（MCL）复合体由前束、后束和横束三部分组成（图2A）。前束和后束起于肱骨内上髁的下方，而横束并不跨越肘关节。前束止于冠状突的高耸结节，是其中最为独特和重要的。后束跨关节后面止于鹰嘴，而横束起止点均在尺骨上，起于鹰嘴前端止于冠状突。
外侧副韧带复合体同样由三部分组成：外侧尺骨副韧带（LUCL）、桡侧副韧带和环状韧带（图2B）。与内侧副韧带复合体相似，前两个韧带的止点附着于上髁，而环状韧带起止点均在尺骨上，用于维持近端尺桡关节的稳定。外侧尺骨副韧带止于尺骨旋后嵴，是抗内翻应力的主要稳定结构，有利于支撑桡骨头，防止肘关节外侧旋转半脱位。桡侧副韧带的止点不直接与尺桡骨附着，而是止于环状韧带。 Fig.2. Ligamentous stabilizers of the elbow. (A) The medial collateral ligament.(B) The lateral collateral ligament complex. 图2 肘关节的韧带稳定结构：A为内侧副韧带复合体，B为外侧副韧带复合体
生物力学 肘关节轴向负重时，主要承重的是肱桡关节（60％），而不是肱尺关节（40％）。肱尺关节高度咬合的结构，主要功能在于维持稳定而不是承重，其对肘关节整体稳定性的贡献可达50％。骨性结构的稳定，可让最简单的肘关节脱位在复位后保持稳定。当向后位移的外力作用于肘关节时，冠状突尤为重要。由于冠状突独特的解剖结构和前关节囊的附着，大的冠状突骨折块对肘关节不稳造成很大影响，甚至是很小的骨折块也意味着肘关节不稳。后者在恐怖三联征中是经常出现的。冠状突前内侧骨折相关损伤机制不同，在恐怖三联征中较少见
如上所述，肱尺关节和肱桡关节均为铰链关节，但二者屈/伸的轴线随着位置的变化而变化，大约存在3°-6°的方向变化和1.4-2.0mm的位移。通常侧位片显示，该轴线从肱骨内髁的前下部分（即MCL前束止点的前方）至所述滑车和肱骨小头的中心。该轴的位置对置入铰链式外固定架具有重要意义。在该平面的正常屈曲运动范围是0°-140°，虽然30°-130°即可满足日常生活需要。
肩关节外展可以弥补有限的旋前，而旋后的缺陷却无法弥补。前臂的旋转也会影响肘关节的稳定性。例如，肘关节旋后可以增加肱尺关节的接触应力和稳定性，从而避免肘关节脱位。然而，在肘关节外侧尺骨副韧带损伤时，旋后也会加重后外侧旋转不稳定，由此引发桡骨头后外侧脱位，反之引发尺骨顶端横向倾斜。旋前位可防止这种外侧旋转不稳。
外翻应力下，桡骨头紧靠肱骨小头，并提供肘关节整体稳定性的30％，当MCL无力时提供的稳定性增加。桡骨头的复位几乎能恢复全部肘关节的外翻稳定性。MCL的前束在伸展时紧张，后束则在屈曲时紧张，两者在肘关节整个运动中也对抗外翻应力。
假设外侧副韧带（LCL）复合体在肘关节脱位时是第一个破坏的结构。如上所述，外侧尺骨副韧带（LUCL）对防止后外侧旋转不稳非常重要，是抗内翻应力的主要稳定结构。虽然LCL复合体中每束韧带的确切贡献仍存在争议，但已经证明仅重建LUCL能可靠地恢复后外侧的稳定性，这表明LUCL是肘关节的主要和关键的稳定结构。
恐怖三联征的损伤机制是：轴向压力作用于伴有前臂旋后的相对外展的肘关节（图3）。该情况导致LUCL损伤，继而桡骨头后外侧脱位，而轴向负荷同时导致桡骨头和冠状突骨折。其实，恐怖三联征可以非常准确地概括为终极的后外侧旋转不稳。 Fig.3. The terrible triad pattern of injury is caused by a combination of valgus and axial compression with the forearm supinated. 图3 恐怖三联征是由外翻和轴向压力与前臂旋后联合所致。 附英文原文: INTRODUCTION The elbow is a 3-dimensionally complex joint where stiffness is poorly tolerated and instability is devastating. Although multiple periarticular fracture patterns and soft tissue injuries of the elbow have been described, the combination of coronoid process fracture, radial head fracture, and elbow dislocation has earned the moniker “terrible triad” by virtue of its challenging treatment and historically poor outcomes. This injury represents a failure of each bony and ligamentous stabilizer of the elbow; therefore, treatment must restore sufficient stability to permit early motion, thereby avoiding disabling stiffness.
RELEVANT ANATOMY The elbow supports the intersection of 3 bones, between which are 3 articulations: ulnohumeral, radiocapitellar, and proximal radioulnar (Fig. 1). The first two of these articulations are ginglymus (hinge) joints, whereas the last is a trochoid (pivot) joint. The terrible triad injury destabilizes the relationship between the humerus and the forearm bones, whereas the relationship between the ulna and radius (including the interosseous membrane) is rarely disrupted in this injury pattern.
While the elbow shares the humerus in common with the shoulder joint, its personality could not possibly be more different. Unlike the relatively straightforward spheroidal glenohumeral joint with its complex circumferential soft tissue stabilizers, the elbow has a complex three-dimensional bony anatomy but relatively simple soft tissue structure consisting of medial and lateral collateral ligaments as well as anterior and posterior capsular elements.
The medial collateral ligament (MCL) complex is composed of 3 bands: anterior, posterior, and transverse (Fig. 2A).The first two originate from the inferior aspect of the medial epicondyle, whereas the last one does not cross the elbow joint itself. The anterior band is the most distinct and significant of these bundles and inserts on the sublime tubercle of the coronoid. Inserting more posteriorly, on the olecranon, is the posterior band, whereas the transverse band is attached at both ends to the ulna, spanning the distance from the tip of the olecranon to the coronoid process.
Laterally, the collateral ligament complex is similarly made of up of 3 components: the lateral ulnar collateral ligament (LUCL), the radial collateral ligament, and the annular ligament (see Fig. 2B). Similar to the MCL complex, the first two components attach proximally on the epicondyle, whereas the annular ligament is a proximal radioulnar joint stabilizer that both originates and inserts on the ulna. The LUCL, which inserts on the crista supinatoris of the posterior proximal ulna, is a major stabilizer against varus stress and also supports the radial head like a sling, preventing posterolateral rotatory subluxation. The radial collateral ligament does not attach to the radius or ulna directly, but rather to the annular ligament.
BIOMECHANICS Load bearing across the elbow is predominantly at the radiocapitellar joint (60%), rather than at the ulnohumeral joint (40%). The latter, with its highly congruent configuration, is structured primarily for stability rather than for load bearing and contributes as much as 50% of the overall stability of the elbow. The stability conferred by these bony structures is what allows most simple elbow dislocations to remain stable after reduction. As displacing forces most commonly act on the elbow in a posteriorly directed manner, the coronoid is particularly vital. Large coronoid fragments destabilize the elbow considerably and even very small fractures may portend a great deal of instability by virtue of their unique anatomic shape and attachment to the anterior capsule. The latter are more common with terrible triad patterns. Fractures of the anteromedial coronoid are associated with a different mechanism of injury and are uncommon in terrible triad injuries.
As mentioned above, the ulnohumeral and radiocapitellar articulations are hinge joints, but their axis of flexion/extension varies with position, by approximately 3°to 6°in orientation and 1.4 to 2.0 mm in translation. On average, however, this axis runs from the anteroinferior aspect of the medial epicondyle (just anterior to the origin of the anterior band of the MCL) to the center of the trochlea and the center of the capitellum on lateral radiography. The location of this axis has important implications for the placement of hinged external fixators in particular. Normal range of motion in this plane is 0°to 140°of flexion, although most activities of daily living may be performed with a limited range of 30°to 130°.
Abduction at the shoulder does compensate for limited pronation, but no similar compensatory movement can substitute for supination. Forearm rotation also affects elbow stability. For example, supination of the elbow increases the joint reactive force at the ulnohumeral joint and increases stability against elbow dislocation. However, in the LUCL-deficient elbow, supination is also implicated in posterolateral rotatory instability, whereby the radial head subluxates posterolaterally, whereas the ulna tilts apex lateral. A position of pronation protects against this posterolateral rotatory instability.
In response to valgus stress, the radial head abuts the capitellum and provides approximately 30% of total elbow stability in this scenario, more so when the MCL is incompetent. Restoration of the radial head restores valgus stability to nearly that of the intact elbow. The MCL, with its anterior band taut in extension and its posterior band taut in flexion, also resists valgus stress throughout the range of elbow motion.
The lateral collateral ligament (LCL)complex is hypothesized to be the first structure to fail in dislocation of the elbow. The LUCL, as described above, is necessary to prevent posterolateral rotatory instability, and it is the major soft tissue stabilizer of the elbow, against varus stress. Although there is some controversy as to the exact contribution of each element of the LCL complex, it has been demonstrated that reconstruction of the LUCL alone reliably restores posterolateral stability, suggesting that LUCL is the primary critical stabilizer against this particular instability pattern.
The terrible triad injury pattern most commonly results from the axial loading of a relatively extended elbow with the forearm in supination (Fig. 3). This position encourages posterolateral escape of the radial head after failure of the LUCL, whereas the axial loading causes shearing of the radial head and coronoid process. In fact, the terrible triad can be conceptualized quite accurately as the ultimate posterolateral rotatory instability.
由MediCool医库软件 赵婷 陆晓玲 编译 原文来自： Terrible Triad of the Elbow Orthop Clin N Am 44 (2013) 47–58
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