Clinical Presentation of Glenohumeral Instability.

Last updated Tuesday, February 01, 2005

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Radiographic evaluation

Radiographs

When a shoulder is dislocated, radiographs need to demonstrate:

1. The direction of the dislocation,
2. The existence of associated fractures (displaced or not), and
3. Possible barriers to relocation.

The glenohumeral joint is most reliably imaged using three standardized views referred to the plane of the scapula: an anteroposterior view in the plane of the scapula (figure 1), a scapular lateral (figure 2), and an axillary view (figure 3). The complete series of three views oriented to the scapula provide much more information than the commonly obtained view in the plane of the body (figure 4). McLaughlin has said that the reliance on anteroposterior radiographs will lead the unwary orthopedist into a "diagnostic trap." (McLaughlin, 1952) Dorgan (Dorgan, 1955) reported that, in addition to obesity, technical factors may prevent accurate identification of the glenohumeral joint in the transthoracic lateral view.

Anteroposterior view in the plane of the scapula

Lateral view in the plane of the scapula

This view is taken at right angles to the anteroposterior in the plane of the scapula (figure 2). (McLaughlin, 1952; McLaughlin, 1963a; McLaughlin, 1963b; Neer, 1968; Rockwood, 1984) Like the anteroposterior view, it can be obtained by positioning the body without moving the dislocated shoulder. The radiographic beam is passed from medial to lateral parallel to the body of the scapula while the cassette is held perpendicular to the beam at the anterolateral aspect of the shoulder (figure 2). (Rockwood, 1984) In this view, the contour of the scapula projects as the letter "Y." (Rubin et al, 1974) The downward stem of the Y is projected by the body of the scapula; the upper forks are projected by the coracoid process anteriorly and by the spine and acromion posteriorly. The glenoid is located at the junction of the stem and the two arms of the Y. In the normal shoulder the humeral head is at the center of the arms of the Y, that is, in the glenoid fossa. In posterior dislocations the head is seen posterior to the glenoid; in anterior dislocations the head is anterior to it.

Axillary view

In this view, first described by Lawrence in 1915, (Lawrence, 1915; Merrill, 1975) the cassette is placed on the superior aspect of the shoulder. This view requires that the humerus be abducted sufficiently to allow the radiographic beam to pass between it and the thorax. Fortunately sufficient abduction can be achieved by gentle positioning of the dislocated shoulder or by modifications of the technique (figure 3 and figures 6 through 8). The axillary radiograph is critical in the evaluation of the dislocated shoulder: it not only reveals unambiguously the direction and magnitude of head displacement relative to the glenoid, but also the presence and size of head compression fractures, fractures of the glenoid, and fractures of the humeral tuberosities. The axillary view may also be helpful in judging the bony competence and version of the glenoid fossa, but the projection must be standardized to avoid misinterpretation.

In his text on radiographic positioning, Jordan demonstrated the various techniques for obtaining axillary lateral views. (Jordan, 1935) Cleaves (Cleaves, 1941; Merrill, 1975) and Teitge and Ciullo (Post, 1978) have described variations on this view (figure 8). Rockwood has pointed out that in the situation when the patient cannot abduct the arm sufficiently, a curved cassette or a rolled cardboard cassette can be placed in the axilla and the radiographic beam passed from a superior position (figure 6). Bloom and Obata (Bloom and Obata, 1967) have modified the axillary technique so that the arm does not have to be abducted (figure 7). They call this the Velpeau axillary lateral view. While wearing a sling or Velpeau dressing, the patient leans backward 30 degrees over the cassette on the table. The x-ray tube is placed above the shoulder and the beam projected vertically down through the shoulder onto the cassette.

In summary, in the evaluation of a possibly dislocated shoulder or a fracture-dislocated shoulder we recommend the three orthogonal projections of the shoulder (anteroposterior and lateral in the plane of the scapula and axillary views), which provide a sensitive assessment of shoulder dislocation. The use of fewer views or other less interpretable projections may obscure significant pathological processes. If the three views cannot be taken, if there is a question regarding the diagnosis, or if there is a need to define anatomy in greater detail, a CT scan may be of great assistance. (Kinnard et al, 1984; Ribbans et al, 1990; Shuman et al, 1983) Using modern methods of three dimensional reconstruction, anterior inferior glenoid lesions and posterior lateral humeral head lesions can be shown in striking detail (figures 9 and 10). It is of note that the patient whose shoulder is shown in these figures obtained an excellent result from non operative treatment in spite of the damage shown on the reconstructions.

Disclaimer

This resource has been provided by the University of Washington Department of Orthopaedics and Sports Medicine as general information only. This information may not apply to a specific patient. Additional information may be found at http://www.orthop.washington.edu or by contacting the UW Department of Orthopaedics and Sports Medicine.

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