Radiographic evaluation of the shoulder requires a minimum of two views of the area that are perpendicular to each other. The shoulder is a complicated anatomic unit made up of numerous bony landmarks, projections, and joints. The scapula, which lies on the posterolateral portion of the rib cage, rests at an angle of approximately 45 degrees to the frontal plane of the thorax. Thus the plane of the glenohumeral joint is not the plane of the thorax, and radiographs taken in the anteroposterior plane of the thorax provide oblique views of the shoulder joint ( Fig. 5.1 ). All too commonly, though, a radiographic evaluation of the shoulder consists of two anteroposterior views of the rotated proximal humerus, which are taken perpendicular to the frontal axis of the thorax.
Orthopedists do not diagnose and treat injuries in any other part of the body on the basis of a one-plane radiographic evaluation. With the exception of localizing rotator cuff calcium deposits, the two traditional anteroposterior views of the shoulder in internal and external rotation are, by themselves, inadequate for evaluating injuries and disorders of the shoulder. Rotating the humerus into internal and external rotation does not change the orientation of the scapula to the x-ray beam. Therefore radiographic evaluation of the shoulder should consist of, at minimum, both anteroposterior and lateral views. Specific oblique views may also be required for the further investigation of specific pathologic conditions of the shoulder.
Fractures of the glenohumeral joint
Recommended views
The recommended views are the trauma series of radiographs—that is, true anteroposterior radiographs in internal and external rotation and an axillary lateral or a scapulolateral view. Modified axillary laterals or a computed tomography (CT) scan may be required.
Radiographs of the injured shoulder in two planes (anteroposterior and axillary lateral or scapular lateral) are absolutely essential to evaluation of an acutely injured shoulder. McLaughlin, Neer, , Neviaser, DeSmet, Rockwood and Green, Post, Rowe, Bateman, and many others have recognized the shortcomings of the usual two anteroposterior radiographs of the shoulder and have recommended both anteroposterior and lateral views for a proper assessment of shoulder problems.
The radiographs used to evaluate traumatic shoulder problems are referred to as the trauma series . It can also be used as baseline radiography to evaluate many chronic shoulder problems.
Following are the recommended radiographs for the trauma series:
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A true anteroposterior view in the plane of the scapula with the arm in internal and external rotation
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An axillary lateral view. If an axillary radiograph cannot be obtained, one of the following views must be obtained:
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A scapulolateral view
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One of the modified axillary views
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A CT scan
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Techniques for taking the trauma series
True anteroposterior views
Because the scapula lies on the posterolateral aspect of the thoracic cage, the true anteroposterior view of the glenohumeral joint is obtained by angling the x-ray beam 45 degrees from medial to lateral ( Fig. 5.2 ; see also Fig. 5.1 ). The patient may be supine or erect, with the arm at the side or in the sling position. An alternative technique is to rotate the patient until the scapula is flat against the x-ray cassette and take the radiograph with the beam perpendicular to the scapula. Sometimes it is difficult for the technician to properly align the patient for the view. A simple technique to assist the technician in positioning the patient correctly consists of using a heavy marking pen to draw a line on the skin along the spine of the scapula. The technician aligns the x-ray beam perpendicular to the line on the skin and directs it at the cassette, which is placed parallel to the line and posterior to the scapula and glenohumeral joint ( Fig. 5.3 ). Although the scapular spine is not exactly parallel to the plane of the scapula, this technique has proved to be effective in clinical practice.
The advantage of the true anteroposterior views of the scapula over traditional anteroposterior views in the plane of the thorax is that the radiograph demonstrates the glenoid in profile rather than obliquely and, in the normal shoulder, clearly separates the glenoid from the humeral head ( Fig. 5.4 ). In the true anteroposterior view, the coracoid process overlaps the glenohumeral joint. If the true anteroposterior view demonstrates the humeral head to be overlapping with the glenoid, the glenohumeral joint is dislocated either anteriorly or posteriorly.
Axillary lateral view
Initially described by Lawrence , in 1915, the axillary lateral view can be taken with the patient supine or erect. Ideally, the arm is positioned in 70 to 90 degrees of abduction. The x-ray beam is directed into the axilla from inferior to superior, with the x-ray cassette placed superior to the patient’s shoulder ( Fig. 5.5 ). To minimize the amount of abduction required to obtain an axillary lateral view, an alternative technique was devised by Cleaves in 1941. In this technique the patient may be sitting or supine; the arm is abducted only enough to admit a curved x-ray cassette into the axilla. The radiograph is then taken from superior to inferior through the axilla. In situations when abduction is severely limited to only 20 or 30 degrees, a rolled-up cardboard cassette can be substituted for the curved cassette in the axilla ( Fig. 5.6 ).
Axillary lateral radiographs provide excellent visualization of the glenoid and the humeral head and clearly delineate the spatial relationship of the two structures. Loss of glenohumeral cartilage is clearly revealed when the joint space between the glenoid and the humeral head is decreased or absent. Dislocations are easily identified, as are compression fractures of the humeral head and large fractures of the anterior or posterior glenoid rim (see Fig. 5.17 later in chapter). Some fractures of the coracoid and acromion and the spatial relationship of the acromioclavicular joint can also be seen on this view.
If a good-quality axillary lateral radiograph can be obtained, the true scapulolateral view and modified axillary lateral views are not necessary. However, if because of pain and muscle spasm the patient does not allow enough abduction for a good axillary view, the scapulolateral or the modified axillary lateral views must be obtained.
Technique for the scapulolateral radiograph
The scapulolateral view is sometimes known as the transscapular, tangential lateral, or Y lateral view. The position of the injured shoulder, which is usually held in internal rotation (with the patient’s arm placed in a sling), is left undisturbed. A marking pen is used to draw a heavy line over the spine of the scapula ( Fig. 5.7 A). The technician then aligns the x-ray beam parallel to the line on the skin, directed at the cassette, which is placed perpendicular to the line at the anterolateral shoulder. The x-ray beam passes tangentially across the posterolateral chest, parallel to and along the spine of the scapula onto the cassette (see Fig. 5.7 A and B). The projected image is a true lateral view of the scapula and hence of the glenohumeral joint (see Fig. 5.7 B).
A lateral projection of the scapula forms a Y-shape ( Fig. 5.8 A–C). The upper arms of the Y are formed by the coracoid process anteriorly and the scapular spine posteriorly. The vertical portion of the Y is formed by the body of the scapula. At the intersection of the three limbs of the Y lies the glenoid fossa. In the normal shoulder, the humeral head is located overlapping the glenoid fossa (see Figs. 5.7 B and 5.8 D). This view is particularly helpful in determining the anterior or posterior relationship of the humeral head to the glenoid fossa.
In anterior dislocations of the shoulder the humeral head lies anterior to the glenoid fossa (see Figs. 5.7 C and 5.8 F); in posterior dislocations the humeral head lies posterior to the glenoid fossa (see Figs. 5.7 D and 5.8 E). The scapulolateral view does not define fractures of the anterior or posterior glenoid rim, but it does reveal displaced fractures of the greater tuberosity. When this view is combined with the true anteroposterior and the axillary lateral views, they together provide three views, all 90 degrees to each other, which maximizes the information available to the clinician for an accurate diagnosis.
Techniques for the modified axillary views
Velpeau axillary lateral view
Bloom and Obata’s modification of the axillary lateral view of the shoulder is known as the Velpeau axillary lateral view because it was intended to be taken with the acutely injured shoulder still in a sling without abduction.
With the Velpeau bandage or shoulder sling in place, the patient stands or sits at the end of the radiograph table and leans backwards through 20 to 30 degrees over the table.
The x-ray cassette is placed on the table directly beneath the shoulder, and the x-ray tube is positioned directly over the shoulder so that the beam passes vertically from superior to inferior through the shoulder joint onto the cassette ( Fig. 5.9 ). On this view the humeral shaft appears foreshortened and the glenohumeral joint appears magnified, but otherwise it demonstrates the relationship of the head of the humerus to the scapula.
Apical oblique view
Garth and colleagues have described an apical oblique projection that reliably demonstrates the pathology of the glenohumeral joint. The patient may be seated or in a supine position, and his or her arm may remain in a sling. The x-ray cassette is placed posteriorly, parallel to the spine of the scapula. The x-ray beam is directed through the glenohumeral joint toward the cassette at an angle of 45 degrees to the plane of the thorax and is also tilted 45 degrees caudally ( Fig. 5.10 A and B).
The resultant radiograph demonstrates the relationship of the humeral head to the glenoid and therefore identifies the presence and direction of glenohumeral dislocations and subluxations. This view clearly defines the anteroinferior and posterosuperior rims of the glenoid and is useful for detecting calcifications or fractures at the glenoid rim (see Fig. 5.10 C and D). Posterolateral and anterior humeral head compression fractures are also revealed.
Kornguth and Salazar reported that this technique is excellent for diagnosis in the acute setting.
Stripp axial lateral view
The Stripp axial lateral view, described by Horsfield and Jones, is similar to the Velpeau axillary lateral view except that the beam passes from inferior to superior, and the x-ray cassette is positioned above the shoulder.
Trauma axillary lateral view
This is another modification of the axillary lateral view and has been described by Teitge and Ciullo. , The advantage of this view over the Velpeau and Stripp views is that it can be taken while the patient is supine, as is often necessary for patients with multiple trauma. This view can be taken while the injured shoulder is still immobilized in a shoulder-immobilizer dressing. The patient lies supine on the radiograph table with the involved arm supported in 20 degrees of flexion by placing radiolucent material under the elbow. The x-ray beam is directed up through the axilla to a cassette propped up against the superior aspect of the shoulder ( Fig. 5.11 ). This view defines the relationship of the humeral head to the glenoid fossa.
Computed tomography scan
A CT scan reliably demonstrates fractures, the number of fracture fragments, and fracture-dislocations of the glenohumeral joint. However, the addition of a CT scan to the trauma series does not apparently improve the reproducibility of the Neer or Arbeitsgemeinschaft für Osteosynthesefragen fracture classifications. , The CT technique should consist of 3-mm-thick contiguous sections with a bone algorithm from the top of the acromion to the inferior pole of the glenoid. It is very important that the scan includes both shoulders so that the physician can compare the anatomy of the injured shoulder with that of the normal shoulder. Three-dimensional CT scans can provide additional information in the acute setting for the evaluation of complex or multiple shoulder girdle fractures.
Magnetic resonance imaging
A magnetic resonance imaging (MRI) scan is rarely indicated for managing fractures of the shoulder. However, MRI scans identify the presence of an occult greater tuberosity fracture and associated rotator tendon pathology in a posttraumatic situation and might also help to diagnose the pattern of postfracture avascular necrosis.
Anterior instability
Recommended views
Recommended views for anterior instability are the true anteroposterior views, the West Point axillary lateral, and the apical oblique projection. Arthrograms, arthrotomograms, CT scans, CT arthrography, and MRI scans are discussed in the later section titled “Soft Tissue Evaluation of Shoulder Instability.”
With anterior dislocation or subluxation of the glenohumeral joint, there may be bone damage or soft tissue calcification adjacent to the anterior or, particularly, the anteroinferior rim of the glenoid. The true anteroposterior view can demonstrate a fracture of the inferior glenoid that might not be visualized on the anteroposterior views in the plane of the thorax. Although the axillary lateral view may be useful for demonstrating some anterior glenoid abnormalities, the West Point axillary lateral and apical oblique views provide more information. ,
Anterior shoulder dislocations may be accompanied by fractures of the anterior glenoid rim, which may be demonstrated on a routine axillary lateral radiograph. However, in traumatic anterior subluxation, the glenoid defect almost exclusively involves the anteroinferior glenoid, which cannot be seen on routine axillary lateral views. In many cases the lesions seen on the anteroinferior glenoid rim provide the only radiographic evidence of traumatic anterior shoulder subluxation. Two techniques have been described to evaluate the anteroinferior glenoid rim: the West Point and apical oblique projections.
West point axillary lateral view
This projection was described by Rokous and colleagues when they were stationed at the US Military Academy at West Point; Rockwood has therefore referred to this technique as the West Point view. The patient is positioned prone on the radiograph table with the involved shoulder on a pad raised approximately 8 cm from the surface of the table. The patient’s head and neck are turned away from the involved side. With the cassette held against the superior aspect of the shoulder, the x-ray beam is centered at the axilla with 25 degrees of downward angulation of the beam from the horizontal and 25 degrees of medial angulation of the beam from the midline ( Fig. 5.12 A and B). The resultant radiograph is a tangential view of the anteroinferior rim of the glenoid.
The usual finding seen in the traumatic anterior subluxating shoulder is soft tissue calcification located just anterior to the glenoid rim or anteroinferior bony fracture avulsions (see Fig. 5.12 C and D). A cadaveric study revealed that a 21% glenoid bony defect appeared to be approximately 18% of the intact glenoid on a West Point axillary radiograph. Therefore the West Point axillary view provides decisive information regarding anteroinferior glenoid rim fractures and their operative treatment.
Apical oblique view
The apical oblique view clearly defines the anteroinferior and posterosuperior rims of the glenoid. Pathologic findings of the rim associated with recurrent instability—such as displaced malunited rim fractures, glenoid bone loss, or anterior inferior cartilage loss—are identified with this view ( Fig. 5.13 ). Posterolateral and anterior humeral head defects are also revealed by this view, although CT is needed to quantify the size of the defect.
Recurrent anterior glenohumeral instability
Radiographic views for recurrent anterior glenohumeral instability include the apical oblique view for anterior glenoid erosion, the Stryker notch view for a posterolateral humeral head defect, and MRI or CT arthrography for detachment of the labrum.
Posterior humeral head compression fractures associated with anterior dislocation: The hill-sachs lesion
Recommended views
The recommended views for posterior humeral head compression fractures are the Stryker notch view, the anteroposterior view with the arm in full internal rotation, and other views.
A commonly encountered sequela of anterior shoulder dislocation is a compression fracture of the posterolateral humeral head. Such a fracture can occur during the first traumatic dislocation or after recurrent anterior dislocations. This is commonly referred to as a Hill-Sachs lesion and was reported by Hill and Sachs in 1940 ( Fig. 5.14 ). However, prior to this it had clearly been described by Eve in 1880. In the period between the report by Eve in 1880 and by Hill and Sachs in 1940, it was described by Malgaigne, Kuster, Cramer, Popke, Caird, Broca and Hartman, , Perthes, Bankart, , Eden, Hybbinette, Didiee, and Hermodsson.
The indentation or compression fracture may be seen on the anteroposterior view if the patient’s arm is in full internal rotation, and it may occasionally be seen on the axillary lateral view. However, we believe that one of the best views for identifying the compression fracture is the technique reported in 1959 by Hall and colleagues ; they credited this view to William Stryker, leading Rockwood to call it the Stryker notch view.
Stryker notch view
For the Stryker notch view, the patient is placed supine on the radiograph table with the cassette under the involved shoulder ( Fig. 5.15 A). The palm of the hand of the involved upper extremity is placed on top of the patient’s head, with the fingers toward the back of the head. The x-ray beam is tilted 10 degrees cephalad and centered over the coracoid process. A positive result is a distinct notch in the posterolateral part of the humeral head (see Fig. 5.15 B).
Anteroposterior view in internal rotation
Probably the simplest view but not the most diagnostic is the one described by Adams. It is an anteroposterior view of the shoulder with the arm in full internal rotation. This reveals an indentation or compression in the posterolateral portion of the humeral head, a defect that may appear simply as a vertical condensation of bone. Pring and colleagues compared the Stryker view with the internal (60 degrees) rotation view of Adams in 84 patients with anterior dislocation of the shoulder for establishing evidence of a posterolateral defect in the humeral head. The internal rotation view was positive in 48% of patients, whereas the Stryker notch view was positive in 70%.
Other views predating the Stryker notch view have been described by Didiee and Hermodsson and are useful in demonstrating the presence and size of the posterolateral humeral head compression fractures. Although these techniques involve views of the proximal humerus with the patient’s arm in internal rotation, they are slightly awkward to obtain. The apical oblique view described by Garth and colleagues also demonstrates the compression fracture. Strauss and colleagues and Danzig and colleagues have independently evaluated the efficacy of the various views in revealing the Hill-Sachs lesion and reported that although none of these views reveals the lesion in every case, the Stryker notch view is probably the most effective. The presence of the compression head fracture on the radiograph confirms that the shoulder has been dislocated, whereas its absence suggests that the head may be subluxating rather than frankly dislocating.
After a study of Hill-Sachs lesions created in the posterolateral humeral head, Danzig and colleagues concluded that three views were optimal for defining the lesion: the anteroposterior view with the arm in 45 degrees of internal rotation, the Stryker notch view, and the modified Didiee view.
In a study of 120 patients, Strauss and colleagues reported that a specific set of views could confirm the diagnosis of anterior shoulder instability with 95% accuracy; these were the anteroposterior view of the shoulder in internal rotation and the Hermodsson, axillary lateral, Stryker notch, Didiee, and West Point views.
Whereas the Stryker notch view can document the presence of a compression fracture, advanced imaging studies with CT or MRI provide information that affects surgical decision making. CT, particularly three-dimensional CT, provides images that reveal defect orientation, width and depth, and quantitative information that specifically affects surgical planning ( Fig. 5.16 ).
Posterior instability
Recommended views
Recommended views for posterior instability are the trauma series of radiographs and modified axillary views. Arthrograms, arthrotomograms, CT scans, CT arthrography, and MRI scans are discussed in the later section titled “Soft Tissue Evaluation of Shoulder Instability.”
Techniques to evaluate posterior instability
Posterior dislocation of the shoulder is a rare problem, comprising only 1% to 3% of all dislocations of the shoulder, and it is commonly misdiagnosed. There are three reasons for missing the posterior displacement:
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Inadequate patient history
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Inadequate physical examination
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Inadequate radiographic evaluation
All too often, only two anteroposterior views with the arm in internal and external rotation are obtained. Radiographs of the injured shoulder must be made in two planes at 90 degrees to each other. The diagnosis of posterior dislocation of the shoulder can always be made if the anteroposterior view and one of the previously described lateral views are obtained. Usually the patient does not allow enough abduction to obtain the true axillary view, in which case the scapulolateral or modified axillary view (apical oblique) or a CT scan must be obtained.
Traumatic posterior glenohumeral instability may be accompanied by either damage to the posterior glenoid rim or impaction fractures on the anteromedial surface of the humeral head, the reverse Hill-Sachs lesion ( Fig. 5.17 ). Lesions of the posterior glenoid rim can usually be noted on the axillary view. CT and MRI scans are very helpful both in defining the glenoid rim fracture and in determining the size of the compression fracture of the humeral head.
Soft tissue evaluation of shoulder instability
Patients with recurrent instability often have radiographically occult soft tissue abnormalities. Although their routine radiologic examination may appear normal, a significant injury to the soft tissues is frequently present. In anterior dislocations, the anterior capsule and glenoid labrum may be stripped off the glenoid rim, with an intact periosteum forming a pseudo joint space, as originally described by Perthes in 1906, or a complete avulsion of the labral-ligamentous complex from the glenoid, described by Bankart in 1923.
Plain film arthrography, arthrotomography, and pneumotomography have all been shown to be effective in demonstrating lesions associated with instability, but these are infrequently utilized today for this purpose. CT arthrography, , , MRI, and MR arthrography have largely replaced these techniques for the evaluation of instability.
CT arthrography can demonstrate the status of the anterior or posterior labrum. Shuman and colleagues used double-contrast CT to study the glenoid labrum with a high degree of accuracy ( Fig. 5.18 ). MRI is currently the standard for imaging a suspected labral and capsular abnormality associated with anterior or posterior instability because it provides anatomic images of soft tissue structures and does not use ionizing radiation. , , MRI without intra-articular contrast provides only limited specific information regarding glenohumeral instability, and a study that is interpreted as normal—especially by radiologists with limited experience in shoulder instability—does not rule out symptomatic glenohumeral instability. Authors have reported the sensitivity of MRI without intra-articular contrast to detect anterior labral tearing to range from 44% to 100% and the specificity from 68% to 95%. , , Posterior labral abnormalities have been detected with a reported sensitivity of 74% and specificity of 95% and superior labral tearing with a sensitivity of 86% and a specificity of 100%. Capsular laxity and capsular insertion sites cannot be assessed by MRI without intra-articular contrast. The cost of MRI, initially prohibitive in many cases, is now within the same range as that of CT scans and occasionally even of plain film arthrography. Variability in the accuracy of interpretation of the images has improved, especially with improved communication between the radiologist and orthopedist, and MRI studies for the evaluation of shoulder instability are now commonplace.
MRI combined with intra-articular gadolinium or saline provides images that accurately identify labral and glenohumeral ligament anatomy and injury, associated rotator tendon tearing, biceps abnormalities, and osseous and cartilaginous abnormalities ( Figs. 5.19–5.21 ). Intra-articular injection of gadolinium–diethylenetriamine pentaacetic acid 2 mmol/L has been shown to have complete passive diffusion from the joint within 6 to 24 hours, and rapid renal elimination has led to almost no systemic side effects. A study evaluating MR arthrography of normal shoulders accurately revealed anatomic variations of the anterior labral signal intensity, form, and size; the authors concluded that only major tears or detachments of the labrum should be diagnosed. Other studies have shown accurate depiction of labral and capsular abnormalities, especially when an accurate history is taken into consideration and there is communication between the radiologist and orthopedist. , , In a prospective study of 30 patients, surgical correlation was used to show MR arthrography to be superior to CT arthrography in detecting anterior labral pathology. MR arthrography is also useful in evaluating failed anterior instability surgery, with a reported sensitivity of 100% and specificity of 60% in detecting recurrent anterior labral tears. The addition of the abduction and external rotation (ABER) position has been shown to increase the sensitivity of MR arthrography in revealing tears of the anterior glenoid labrum ( Fig. 5.22 ). Cvitanic and colleagues compared conventional axial MR arthrograms to oblique axial MR arthrograms in the ABER position and found the latter to be significantly more sensitive in revealing anterior glenoid labral tears ( P = .005; Fig. 5.23 ).
Capsular laxity remains problematic. In a study of 121 patients undergoing surgery for anterior instability, capsular laxity was missed in all shoulders, and capsular insertion sites were found to have no role in predicting clinical shoulder instability. Because MR arthrography can show labral tears and avulsions and the position of the labral ligamentous complex after injury, it is helpful for preoperative planning in distinguishing between regular Bankart lesions, Perthes lesions (which can potentially be deceptively difficult to diagnose in their chronic form), anterior labral periosteal sleeve avulsion lesions (which can also be deceptively occult with resynovialization), and humeral avulsion of the glenohumeral ligament lesions. , These lesions can have similar clinical presentations and examination findings and can be difficult to diagnose any other way.
In the past, MRI and MR arthrography were found to be limited in providing diagnostic information important to the patient’s surgical management. Close correlation with clinical history, open communication between orthopedists and radiologists, and an increase in the number of radiologists trained in musculoskeletal imaging have led to an improvement in the utility of MRI and MR arthrography in shoulder instability. However, an MR arthrogram study that is interpreted as negative does not rule out symptomatic clinical glenohumeral instability.
Imaging of the superior labrum may be difficult. However, on coronal fat-suppressed proton-density–weighted MRI, a hyperintense linear fluid signal within the superior labrum creating a 5-mm superior shift of the labrum indicates a superior labral tear. Additionally, the presence of a paralabral cyst indicates tearing of the adjacent labrum ( Fig. 5.24 ). Surgical confirmation has shown that MR arthrography reliably and accurately reveals superior labral tears. With a sensitivity of 84% to 92% and specificity of 82% to 91%, along with substantial interobserver agreement, MR arthrography is the gold standard for radiographically evaluating superior labral tears. ,
Glenohumeral arthritis
Recommended views
Recommended views for glenohumeral arthritis are the true anteroposterior views in internal and external rotation and an axillary lateral view. A limited CT scan may be required to assess glenoid erosion.
Loss of articular cartilage leads to shoulder pain from glenohumeral arthritis. The radiographic views that demonstrate joint space narrowing or articular cartilage loss are the true anteroposterior, the axillary lateral ( Fig. 5.25 ), and the apical oblique. Osteophyte formation and humeral head deformity are revealed by internal and external rotation anteroposterior radiographs of the shoulder. Posterior glenoid erosion and posterior humeral head subluxation can also be shown by the axillary lateral and apical oblique views. However, the axillary lateral view should not be relied on to determine glenoid version , the angle formed by a line between the anterior and posterior rims of the glenoid and a line perpendicular to the axis of the scapular body ( Fig. 5.26 ), because Galinat determined that up to 27 degrees of variation exists, depending on the angle of the x-ray beam and scapular rotation.
