Anterior Glenohumeral Instability Workup

Updated: Nov 29, 2015
  • Author: Amin H Afsari, DO; Chief Editor: S Ashfaq Hasan, MD  more...
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Workup

Radiography

Radiologic study of the dislocated or subluxed shoulder should include a minimum of three views: true anteroposterior (AP), scapular Y, and axillary. This combination of views provides the best evaluation of the bony structures. Although frequently only soft-tissue injury is present, bony pathology is present in 55% of traumatic dislocations.

True anteroposterior view

Also known as the Grashey view, the true AP view is obtained by placing the posterior surface of the scapula flat onto the radiography film. This results in a view that is 45° oblique to traditional shoulder AP radiography.

A successful exposure demonstrates the glenohumeral joint space, superoinferior head subluxation, joint congruity, joint degeneration, and other articular abnormalities. Disadvantages to this view exist, including anterior and posterior glenoid overlap, which can obscure Bankart lesions. Increased soft-tissue overlap compared with an AP view lessens the quality of bony detail.

Scapular Y view

The scapular Y view is obtained by aiming the x-ray beam longitudinally down the axis of the scapular spine (see the image below). The humeral head lies directly over the glenoid fossa. The Y shape is formed by the projection of the acromion, scapular body, and coracoid from the longitudinal axis.

Y-view radiograph of the right shoulder shows ante Y-view radiograph of the right shoulder shows anterior dislocation of the humeral head relative to the glenoid fossa

This view may be adequate for evaluating dislocations, but it should never replace the axillary view, which is the most sensitive for detecting subluxations. Like the true AP view, it is a poor choice for evaluating glenoid rim fractures.

Axillary view

The axillary lateral view has had many variations. Originally, as described by Lawrence in 1915, it was obtained with the patient supine, the arm abducted to 90°, and the x-ray beam aimed from inferior to superior with 15-30° of medial angulation, depending on the amount of abduction. The resulting radiograph allows detection of AP subluxation/dislocation and anterior or posterior glenoid rim fractures.

The West Point view is one variation of the axillary lateral view. It places the patient prone with the arm abducted to 90° and hanging over the edge of the table. The x-ray beam is directed 25° medially and anteriorly. This position improves visualization of the anteroinferior glenoid rim. West Point axillary views are the most sensitive for finding osseous glenoid fractures. [14]

Internal and external rotation views

Internal and external rotation views provide oblique visualization of the shoulder joint, with the humeral head overlapping the glenoid rim.

The advantage of these views is the excellent osseous detail of the scapula, clavicle, upper ribs, and soft tissues. The high-quality bony detail is the result of the low density of the surrounding soft tissue. Internal rotation of the arm in the AP view projects the lesser tuberosity medially and the posterolateral aspect laterally, providing a good view of Hill-Sachs lesions. These views are of little value in detecting anterior or posterior dislocation/subluxation.

Stryker-Notch view

The Stryker-Notch view was developed to allow visualization of Hill-Sachs lesions. It is obtained with the patient supine. The hand is placed on top of the head with the elbow flexed. The x-ray beam is directed from anterior to posterior with a 10° cephalic angulation. It provides good detail of the posterolateral margin of the humeral head.

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Computed Tomography and Magnetic Resonance Imaging

Arthrography has become obsolete since the advent of computed tomography (CT). It is no longer indicated in shoulder dislocation, though a couple of studies have shown 100% sensitivity in detecting capsulolabral pathology with double-contrast computed arthrotomography.

For most authors, magnetic resonance imaging (MRI) is the imaging modality of choice for soft-tissue injury. It has been shown to be 91% sensitive in detecting capsulolabral injury in the early postdislocation period.

Further from the injury, MRI and arthrotomography have been up to 96% sensitive and provide a better depiction of the inferior glenohumeral ligament (IGHL) than does computed arthrotomography. Keep in mind these adjunct studies are necessary only in a minority of patients.

e Souza et al evaluated the accuracy of conventional MRI in determining the severity of glenoid bone loss in 36 patients with anterior shoulder dislocation by comparing results obtained by using conventional MRI with those from arthroscopic measurements. [15] They found that interreader and intrareader correlations of MRI-derived measurements of glenoid bone loss were excellent and that the first and second observers' measurements showed strong and moderate interreader correlation, respectively, with arthroscopic measurements.

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