The Journal of Bone and Joint Surgery 80:1361-1364 (1998)
© 1998 The Journal of Bone and Joint Surgery, Inc.
The Use of Ultrasonography in the Diagnosis of Occult Fracture of the Radial Neck. A Case Report*
RICHARD D. LAZAR, M.D. ,
PETER M. WATERS, M.D. and
DIEGO JARAMILLO, M.D., BOSTON, MASSACHUSETTS
Investigation performed at Children's Hospital, Boston
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Introduction
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Fractures of the radial neck have been reported to account for approximately 6 per cent of all fractures about the elbow in children; in the combined series reported by Wilkins et al., for example, 289 of 4490 fractures about the elbow in children involved the radial neck10. Fractures about the elbow in skeletally immature patients are often difficult to assess on plain radiographs because of the absence of, or variations in the appearance of, the secondary centers of ossification of the distal aspect of the humerus and the proximal aspects of the radius and olecranon. Clinical examination may be inconclusive because of diffuse swelling, the absence of localized tenderness, and the inability of a young patient to identify the site of pain appropriately.
Additional studies, such as stress radiography, arthrography1,4, and magnetic resonance imaging3, often are needed in order to diagnose the injury accurately. However, these procedures are associated with a number of disadvantages; specifically, stress radiography can be painful for the patient, arthrography is invasive and often necessitates the use of sedation or anesthesia, and magnetic resonance imaging is relatively expensive. Ultrasonography has been advocated as an alternative method for the evaluation of injuries of the elbow in children because of its non-invasive nature and relatively low cost. Barr and Babcock as well as Markowitz et al. demonstrated the usefulness of ultrasonography in accurately identifying the unossified epiphysis of the distal aspect of the humerus and the proximal aspects of the ulna and radius. Davidson et al. subsequently demonstrated the ability of ultrasonography to provide diagnostic images of physeal separations and supracondylar fractures of the distal humeral epiphysis.
This case report illustrates the usefulness of ultrasonography in the evaluation of an injury of the elbow in a skeletally immature patient who had abnormal findings on physical examination. Plain radiographs were inconclusive because of the absence of the secondary centers of ossification of the radial head (Fig. 1-A). Ultrasonography defined the nature of the injury and helped to determine the appropriate treatment.
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FIG1: Figs. 1-A through 1-F: Imaging studies and line drawings demonstrating the appearance of the proximal aspect of the radius of the patient described in the present study.
Fig. 1-A: Anteroposterior radiograph, made four weeks after the injury, showing a mild irregularity of the metaphyseal border (arrow) of the proximal aspect of the right radius. The radiographs that had been made at the time of the injury had been interpreted as normal.
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Case Report
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A twenty-two-month-old boy was admitted to another hospital for evaluation and observation after a fall from a second-floor window. Radiographs of the right elbow were interpreted as revealing no osseous abnormality, and the patient was discharged after twenty-four hours of observation. Two day later, the parents noted that the child continued to protect the right arm and that he was unable to flex or extend the elbow. Additional radiographs showed only soft-tissue swelling and no fracture. Radiographs that were made four weeks later because of persistence of the symptoms were interpreted as normal by the treating physician; in retrospect, however, these radiographs demonstrated an irregularity of the metaphysis of the proximal aspect of the radius (Fig. 1-A).
Eight weeks after the injury, the patient was referred to us because of persistent pain and limitation of motion of the right elbow. Physical examination revealed a 20-degree arc of flexion-extension (from 90 to 110 degrees of flexion). The arc of supination-pronation also was limited to 20 degrees (from 10 degrees of supination to 10 degrees of pronation), and there was pain at the extremes of motion. Ultrasonography demonstrated displacement of the proximal radial epiphysis (Figs. 1-B, 1-C, 1-D through 1-E). The diagnosis was confirmed with magnetic resonance imaging (Figs. 1-F, 1-G, and 1-H).
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FIG1-B: Fig. 1-B Coronal ultrasonographic image of the radiocapitellar joint, showing the radial metaphysis (arrows) to be contiguous with the distal humeral epiphysis. The radial head is not visualized. C = ossification center of the capitellum.
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FIG1-C: Fig. 1-C Line drawing of the ultrasonographic image shown in Fig. 1-B, depicting separation of the proximal radial physis. The shaded area corresponds to cartilage, and the dotted lines indicate osseous contours obscured by shadowing. The unossified radial head is absent, and the capitellum abuts the radial metaphysis. 1 = unossified capitellum, 2 = ossification center of the capitellum, 3 = radial metaphysis, and 4 = fascial plane.
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FIG1-D: Fig. 1-D Coronal ultrasonographic image of the unaffected, left elbow, demonstrating the normal appearance of the cartilaginous radial epiphysis (arrow).
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FIG1-E: Fig. 1-E Line drawing of the ultrasonographic image shown in Fig. 1-D. The ossification center of the capitellum is not shown. The shaded areas correspond to cartilage, and the dotted line indicates the osseous contour obscured by shadowing. 1 = unossified capitellum (partially sectioned), 2 = unossified radial head, 3 = proximal aspect of the ulna, 4 = fascial plane, and 5 = radial metaphysis.
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FIG1-F: Fig. 1-F Sagittal fat-suppressed T2-weighted magnetic resonance image of the right radiocapitellar joint, showing the capitellum (C) to be articulating with the radial metaphysis, which has an irregular border (arrow).
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FIG1-G: Fig. 1-G Sagittal fat-suppressed T2-weighted magnetic resonance image of the radiocapitellar joint of a different patient, an eighteen-month-old boy who had a non-displaced fracture of the distal humeral metaphysis (not shown), demonstrating the normal appearance of the unossified structures of the elbow. The contour of the unossified capitellum (C) is outlined by the joint effusion. The radial head (arrow) has the same configuration as that of the radial head in an adult, even though it is completely unossified.
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FIG1-H: Fig. 1-H Coronal gradient-recalled-echo magnetic resonance image of the patient described in the present study, showing an ovoid fragment of cartilage corresponding with the separated radial epiphysis (*), just distal to the capitellum (C).
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The patient was taken to the operating room for open reduction and internal fixation of the physeal fracture of the radial neck. Intraoperatively, the physis and the articular surface of the radial head were found to be completely displaced and the radial metaphysis was seen to be articulating with the capitellum. The radial head was attached to the radial neck by a thin band of periosteal tissue. The fracture was reduced, with particular care being taken to maintain the periosteal attachment in order to preserve the blood supply to the radial head. The reduction was maintained when the forearm was rotated from a position of full supination to one of full pronation, and it was stabilized with a repair of the adjacent soft tissues and the application of an above-the-elbow cast.
The cast was worn for five weeks, and a sling was used for an additional two weeks. Eight weeks after the reduction, the patient had a 90-degree arc of flexion-extension (from 30 to 120 degrees of flexion) and a 75-degree arc of supination-pronation (from 10 degrees of supination to 65 degrees of pronation). At the two-year follow-up examination, the patient had a full range of flexion-extension and a 105-degree arc of supination-pronation (from 25 degrees of supination to 80 degrees of pronation). Radiographs showed the fracture to be healed, and there was nearly normal anatomical alignment of the radial head and neck (Fig. 1-I).
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FIG1-I: Fig. 1-I Anteroposterior radiograph, made at the time of the two-year follow-up examination of the patient described in the present study, showing the beginning of ossification of the secondary center of the radial head. The radial head and neck have nearly normal anatomical alignment. There is mild widening and irregularity of the proximal radial metaphysis.
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Discussion
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It is often difficult to evaluate the nature of an injury of the elbow in a skeletally immature patient with use of plain radiographs because of the wide variation in the chronological appearance of the six cartilaginous secondary centers of ossification about the elbow7. Usually, the capitellum appears between the ages of one and two years; the radial head, between two and three years; the medial epicondyle, between five and six years; the trochlea, between nine and ten years; the olecranon, between seven and nine years; and the lateral epicondyle, at ten years11.
When radiographs of the injured elbow appear normal, radiographs of the contralateral elbow are often helpful for determining the presence of any asymmetry. Murphy and Siegel discussed the differential diagnoses that should be considered when abnormal elevation of the anterior or posterior fat pad is seen on a lateral radiograph of the elbow. Fraser described the risk of missing a displaced fracture of the radial head when the radiographic findings are interpreted as normal. Therefore, additional diagnostic studies are necessary when a fracture of the radial neck is suspected clinically. Radiographs made with the application of mediolateral stress can be considered, but the application of stress causes pain and is associated with the risk of physeal injury. An arthrogram is often useful for defining intra-articular involvement in a young patient who has an unossified condylar physeal center4. The disadvantage of arthrography of the elbow is its invasive nature, which often necessitates the use of sedation or anesthesia. Our protocol at Children's Hospital has been to perform arthrography of the elbow with the patient under general anesthesia in the operating room at the time of operative intervention.
Ultrasonography has been found to be useful for the detection of fractures involving the entire distal humeral epiphysis in neonates and infants, in whom ossification is incomplete6. An examination of the unossified radial head with ultrasonography necessitates high-resolution imaging with high-frequency linear transducers. Lateral coronal and posterior sagittal approaches best define the location of the radial epiphysis. The contralateral elbow should always be examined for comparison (Figs. 1-D and 1-E).
The case of our patient illustrates the diagnostic capability of ultrasonography in the evaluation of an injury of the elbow in a skeletally immature patient who has abnormal findings on physical examination and normal findings on radiographs. The ultrasonographic diagnosis of a completely displaced proximal radial epiphysis was confirmed with magnetic resonance imaging studies. On the basis of these findings, the patient was taken to the operating room for open reduction of the fracture. We believe that the delay in the appropriate management of our patient could have been avoided if ultrasonography had been performed earlier.
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Footnotes
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*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
Departments of Orthopaedic Surgery (R. D. L. and P. M. W.) and Radiology (D. J.), Harvard Medical School, Children's Hospital, 300 Longwood Avenue, Boston, Massachusetts 02115. E-mail address for Dr. Waters: waters@a1.tch.harvard.edu.
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References
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Introduction
Case Report