Reduction of Radial Head Dislocation

Updated: Aug 02, 2017
  • Author: Gretchen S Lent, MD; Chief Editor: Erik D Schraga, MD  more...
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Overview

Background

Dislocation of the radial head can be congenital, related to underlying disease, or traumatic. In the emergency department (ED), most patients with acute radial head dislocations are men who have sustained a high-force injury. [1]  These dislocations typically are due to external rotational stress on the ulna. [2] Forearm fractures and dislocations, especially in children, are often misjudged, and it is important to maintain a high index of suspicion for these injuries in patients presenting after elbow and arm trauma. [3]

In children, the radial head is much more commonly subluxated than it is dislocated. (See Reduction of Radial Head Subluxation.)

Isolated radial head dislocations are exceedingly rare. [4] Some argue that they do not even exist and believe that radial head dislocations occur only with disruption of the ulna, including "plastic deformation" (described as Monteggia equivalents in children; see below). [5]  More commonly, radial head dislocations are complicated by complete elbow dislocations or fractures, as in the Monteggia complex (see below).

Radial head dislocations may be seen in association with the rare isolated interosseous membrane injury of the forearm or in association with an Essex-Lopresti injury (fracture of the radial head with concomitant dislocation of the distal radioulnar joint and disruption of the interosseous membrane). [6, 7] Radial head dislocations have also been rarely seen with associated humeral condyle fracture. [8]

The radial head can be congenitally dislocated in isolation or in conjunction with other congenital abnormalities, such as those in Steel syndrome, Rubinstein-Taybi syndrome, nail-patella syndrome (hereditary onycho-osteodysplasia), autosomal dominant omodysplasia, multiple hereditary exostosis, multiple cartilaginous exostosis, mesomelic dysplasias, radioulnar synostosis, osteogenesis imperfecta, osteochondromas, and achondroplasia. [9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

Radial head dislocations have also arisen from complications of osteomyelitis, osteochondromatosis, brachial plexus birth palsy, and arteriovenous malformations that cause osteolysis. [11, 21, 22, 23, 24]

Traumatic radial head dislocations are most often seen with associated fractures. Monteggia clinically noted and described the combination of radial head dislocation and proximal ulnar fracture in 1814, before formal radiography was available. [25] More than a century later, Bado [26, 27] further classified the Monteggia injury into four types on the basis of the angulation of the fracture and the direction of dislocation. [28, 29]

The Bado classification (see Table 1 below) is useful descriptively but not prognostically. "Monteggia equivalents" are occasionally seen in children and involve dislocations of the radial head with plastic bowing of the ulna. [30]

Table 1. Bado Classification of Monteggia Injuries (Open Table in a new window)

Classification Incidence Description
Type I 60% Fracture of the proximal or middle third of the ulna with anterior angulation and anterior dislocation of the radial head
Type II 15% Fracture of the proximal or middle third of the ulna with posterior angulation and posterior dislocation of the radial head
Type III 20% Fracture of the ulnar metaphysis distal to the coronoid process with lateral dislocation of the radial head
Type IV 5% Fracture of the proximal or middle third of the ulna and fracture of the proximal third of the radius with anterior dislocation of the radial head

Monteggia fractures may occur with other fractures (eg, Galeazzi) or other dislocations (eg, transolecranon fracture-dislocations). [25]  Radial head dislocation is often associated with significant trauma (eg, motor vehicle accidents, pedestrian–motor vehicle accidents, or significant falls). The proposed mechanism is force directed onto an outstretched, pronated arm. [31]  Other mechanisms of injury, such as hyperextension of the elbow with the forearm in midprone position, have been reported. [4]

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Indications

Radial head dislocations are easily missed on radiographs and require a high index of suspicion for diagnosis. [32, 33, 5]  Undiagnosed chronic radial dislocations lead to poor outcome, limited function, and chronic pain. [34]  The therapeutic goals are as follows [35] :

  • To maximize patient comfort
  • To recognize and treat any coexisting injury
  • To reduce the radial head dislocation within 6-8 hours of injury

Diagnosis

Physical examination

A person with a radial head dislocation typically holds his or her elbow flexed at 90º and resists passive and active range of motion (ROM) at the elbow, including pronation and supination. The elbow is often swollen and diffusely tender with increased point tenderness over the radial head (see the image below). In the case of Monteggia fracture, crepitus may be present over the proximal ulna. The radial head may be palpable in an anterolateral or posterolateral location, and the forearm may appear shortened and angulated.

Swollen elbow from radial head dislocation. Swollen elbow from radial head dislocation.

Imaging

In patients with suspected injury, standard anteroposterior (AP), lateral, and oblique radiographs should be taken of the elbow and forearm (see the images below). [11] (See Elbow, Fractures and Dislocations - Adult.) A clinician should evaluate the radiocapitellar, ulnohumeral, and radioulnar joints, as well as the entire radius and ulna, for evidence of dislocations or fractures. [25]  Consideration should be given to imaging the joint above and below for assessment of possible additional injury as needed. 

Elbow anatomy. Elbow anatomy.
Landmarks on lateral elbow radiograph: radial head Landmarks on lateral elbow radiograph: radial head (R), ulna (U), capitellum (C), and humerus (H).

The radiocapitellar line can be used to evaluate for subluxations and dislocations of the radial head. [36]  This line, drawn through the middle of the neck of the radius, normally bisects the capitellum in any degree of flexion or extension (see the image below). [37]  Deviation of this line suggests capitellar or radial dislocation.

Normal radiocapitellar line drawn down through mid Normal radiocapitellar line drawn down through middle of neck of radius should intersect capitellum.

Be sure to carefully evaluate the ulna for any fracture or plastic bowing deformity suggestive of a Monteggia complex or equivalent. [38]  In a Monteggia fracture, the apex of the ulnar fracture points in the direction of the radial head dislocation (see the image below).

Abnormal radiocapitellar line due to dislocation o Abnormal radiocapitellar line due to dislocation of radial head. Line does not bisect capitellum. Apex of ulnar fracture points in direction of radial head dislocation (anteriorly, in this case).

A novel assessment technique referred to as the ulnar bow sign can be used to assess for plastic ulnar deformities that may be found in radial head dislocations. [39]  This requires a true lateral radiograph of the ulna; the bowing might be missed on a lateral radiograph of the elbow. [11, 5]  (See the image below.)

Abnormal maximum ulnar bow is present when maximum Abnormal maximum ulnar bow is present when maximum perpendicular distance (red arrow) drawn from the dorsal ulnar border (dashed line) exceeds 1 mm.

In certain cases where the injury remains in question, computed tomography (CT), three-dimensional (3D) CT, or magnetic resonance imaging (MRI) may be indicated for further evaluation. [2, 40]

Once the dislocation is recognized, the direction of the radial head displacement (ie, anterior, posterior, or lateral) must next be noted. [41]  A reduction must be performed to restore elbow function with flexion, pronation, and supination. [41]

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Contraindications

The management of a radial head dislocation is dictated by the presence or absence of an associated fracture. If an associated fracture is present, the forearm is not considered stable; in such a case, bedside reduction of a radial head dislocation typically is not appropriate.

Whereas a conservative approach may be considered in children with Monteggia injuries, operative repair is typically recommended for adults. [42, 43, 44]  In deciding on the managment approach, the type of ulnar fracture is more important than the direction of radial head dislocation. [25]  Adolescents seem to have the best prognosis for Monteggia fractures. [25]

Open and complex radial head dislocations, as well as Monteggia fractures in adults, necessitate consultation with an orthopedic or hand surgeon. [45]  Such injuries are usually reduced with fixation in the operating room. [46, 47, 48]

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