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Letter to the Editor |
Department of Radiology, Thomas Jefferson University Hospital, 111 South 11th Street, Suite G3390, Philadelphia, PA 19107. e-mail: david.karasick@jefferson.edu
Editor:
In the July-August 2004 issue of RadioGraphics, the article on musculoskeletal colloquialisms by Lee et al (1) has a serious error in the legend for figure 22 on page 1023. This case is not nursemaid elbow as stated. It is an example of congenital radioulnar synostosis. In addition, there is no radial dislocation. It is normal for the radiocapitellar line to be offset slightly on one or more views. With congenital synostosis, you can have alignment problems at the joint. My residents picked up this error, and I am surprised that it was not seen before.
References
Department of Radiology, University of Arizona College of Medicine, 1501 North Campbell Avenue, PO Box 245067, Tucson, AZ 85724-5067. e-mail: tbh@3towers.com
We thank Dr Karasick for his interest in our article and for his comments concerning our example of a nursemaid elbow (1). As Dr Karasick noted, the case illustrating the nursemaid elbow in figure 22 is not a good example of that condition. In the case shown, the patient has a proximal radioulnar synostosis at the level of the ulnar coronoid ridge. Some patients with congenital radioulnar synostosis have associated radial head alignment problems, even dislocation, and may possibly be predisposed to subluxation in cases of minor trauma. In the case illustrated, it is uncertain what role the synostosis played in the patient’s findings. We do believe there was mild radial head subluxation and subsequent relocation.
The definition of nursemaid elbow is the subject of some disagreement. As originally understood (both by us and by the authors of the reference we cited [2]), a nursemaid elbow involves actual subluxation of the radial head. However, Dr Lee Rogers believes this is not the case and states that the radiographic findings in this condition are normal (3). Stone in 1916 (4) and Salter and Zaltz (5) in 1971 found that the annular ligament is poorly attached to the radial neck in children less than 5 years old, and the radial head is not much larger than the radial neck at this age. When a young child’s elbow is suddenly pulled in extension and pronation, the radial head may slip distally beneath the annular ligament, which is partially torn from the radial neck. The ligament is then trapped in the joint, causing the typical pain and disability of a nursemaid elbow, with the child holding his or her arm in pronation. Subsequent supination of the forearm allows the ligament to be restored to its normal position with relief of all symptoms (3). This supination may occur spontaneously or be the result of a physician or someone else deliberately manipulating the child’s forearm. According to Dr Rogers, "There is no identifiable subluxation of the radial head, and the annular ligament is so thin that there is no detectable widening of the joint when it is entrapped... When the history and physical findings are typical of this disorder, there is no real reason to perform a radiographic examination" (3).
On the other hand, some do not consider the patient’s condition to be resolved unless there is a characteristic click, representing the relocation of a subluxed radial head. Boyette et al (2) believed that "Treatment consists of moderate pressure over the head of the radius with forceful supination of the hand. Successful treatment is accompanied by the characteristic click." Whether this "characteristic click" is present in all cases or only in a small percentage of them, it must signify there was a substantial subluxation of the radial head. Such a subluxation may be evident radiographically if the relative positions of the radius and capitellum are carefully assessed, although this is a matter of considerable controversy (2–5; Rogers LF, oral communication, August 2004; Valencia F, oral communication, August 2004).
It is fair to say that radiography is not indicated in most cases in which the patient history and physical examination findings are typical for a "pulled elbow." Dr Francisco Valencia, a pediatric orthopedic surgeon from Tucson, Ariz, states "The diagnosis is largely clinical since there are few bony radiographic findings. The treatment is simple. Since the injury is caused by a traction-pronation mechanism, the treatment is to flex and supinate the forearm. Most children do not require any further intervention. If a child presents with a history of repeated injuries, I will put them in a cast to allow the ligament to heal" (Valencia F, written communication, August 2004).
If one draws a line bisecting the proximal radial shaft, the line should pass through a portion of the capitellum on every radiographic view (Fig 1) (3; Rogers LF, oral communication, August 2004). Rogers recommends this line be drawn through the neck of the radius proximal to the radial tuberosity, because the radial shaft is often bowed distal to the radial tuberosity. "If the line fails to pass through the capitellum, dislocation of the radial head or displacement of the capitellum is indicated" (3). We believe the case presented in our article illustrates this phenomenon.
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In extreme cases, the patient with radioulnar synostosis may demonstrate marked radial shaft bowing and almost complete fusion of the entire length of the radius and ulna. The patient’s functional status is difficult to predict from the radiographic appearance of his or her elbow and forearm, and many patients do not report any functional impairment (6,7). The main functional problem is one of varying degrees of fixed forearm pronation with a reduced ability to supinate the forearm and hand. In most cases, there is no associated shoulder or distal radioulnar joint abnormalities. In fact, distal fusion of the radius and ulna near the wrist joint is very rare (8).
The degree of clinical disability varies, but many patients with radioulnar synostosis are asymptomatic. Radioulnar synostosis can be severely disabling if it is bilateral or if there is a severe degree of fixed pronation (6,7). The more extensive the synostosis, particularly with radial head absence, the greater the degree of fixed pronation. Rotational hypermobility of the wrist is present and helps patients functionally (7). In carefully selected cases, surgery may be warranted (6–8).
Isolated congenital dislocation of the radial head is more common than proximal radioulnar synostosis, and the two disorders may be confused with each other (8,9). In many cases, congenital dislocation of the radial head is associated with other congenital malformations and may be a feature of heritable disorders of connective tissue in which there is joint laxity (8). It is also thought to be associated with poor development of the capitellum. Wiley et al (9) reported findings for 54 patients with isolated dislocations of the radial head (bilateral dislocations in 12). Approximately half of their patients (26 cases) had radial head dislocations associated with congenital diseases, including radioulnar synostosis, and slightly more than half (28 cases) had acquired dislocations involving trauma (17 cases), neuromuscular impairment, or adaptive dislocations. In the trauma cases, closed reduction of the dislocation was successful in 16 of the 17 cases (9). Most of the congenital dislocations were posterior, and most of the traumatic dislocations were anterior, but the direction of the dislocation correlated poorly with understanding of the cases, because most patients (except for the acute trauma patients) were functionally normal. Treatment is usually not indicated for true congenital dislocation (9).
In summary, as pointed out by Dr Karasick, we should have used a different case to illustrate and discuss nursemaid or pulled elbow for our article on musculoskeletal colloquialisms. As the above discussion shows, the issue of radial head subluxation-dislocation turns out to be a fascinating, complex subject.
Financial Interest: Both authors have no financial relationships to disclose.
Footnotes
Recent eLetters to the Editor are available at http://radiographics.rsnajnls.org. eLetters that are no longer posted under "Recent eLetters" can be found as a link in the related article or by browsing through past Tables of Contents.
References
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