Radiographic studies and findings

CHAPTER 8 Radiographic studies and findings



Giuseppe Porcellini, MD, Francesco Fauci, MD, Fabrizio Campi, MD, Paolo Paladini, MD



Key points



image The treatment of instability requires precise identification of the underlying lesion through clinical examination and diagnostic imaging.

image Visualization and treatment of any associated lesions are essential because the lesions are often associated with pain and poor outcomes.

image The diagnosis of shoulder instability involves a workup that begins with plain x-rays and is completed with magnetic resonance imaging or magnetic resonance arthrography.

image Dedicated views and approaches have been developed to address multiple types of shoulder lesions.


Introduction


Improvements in anatomic and biomechanical knowledge and in arthroscopic techniques now allow ad hoc management of all lesions underlying shoulder instability and restoration of the premorbid anatomy to prevent recurrences. Hence precise lesion identification through clinical examination and diagnostic imaging is needed not only to address the primary lesion but also to depict any associated lesions, which are often related to pain and poor outcomes.


Lesions change as a function of time since the first dislocation, the number of dislocations, and patient age. The diagnosis of shoulder instability involves a workup that begins with plain x-rays and is completed with magnetic resonance (MR) arthrography.



Imaging evaluation



Plain x-rays


The anterior or posterior direction of the instability is established on plain films. X-rays demonstrate bone lesions such as glenoid fracture, Hill-Sachs lesion, and fracture of the tuberosities or of the proximal humeral epiphysis. Patients presenting with an acute lesion undergo the trauma series, whereas the true anteroposterior (AP), axillary, West Point, and Stryker notch views are essential in those with chronic instability because they demonstrate any glenoid or humeral lesions (e.g., Bankart and Hill-Sachs lesions).



Standard anteroposterior view


The standard AP view is an oblique view in which the humeral head and the glenoid partially overlap because of the anterior tilt (approximately 40 degrees) of the beam directed toward the humeral head. This view can be obtained in internal and external rotation to demonstrate a Hill-Sachs lesion (Fig. 8-1).


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FIGURE 8-1 Plain x-rays, standard anteroposterior view. A, External rotation. B, Internal rotation: the dashed line outlines a Hill-Sachs fracture. C, AP x-ray in the plane of the body. An AP view in the coronal plane of the body is of limited use in the evaluation of the glenohumeral joint, the joint space, or the relationship of the humeral head to the glenoid fossa.


(Modified from Matsen FA, III, et al: Shoulder surgery: Principles and procedures, Philadelphia, 2004, WB Saunders, p 7.)



True anteroposterior (grashey) view


The beam directed lateral to the scapula (45 degrees) affords optimal visualization of the glenohumeral (GH) joint, with the overlying anterior and posterior glenoid rim highlighting the joint line. This view clearly demonstrates any erosion of the anterior glenoid rim that fails to be depicted (Fig. 8-2).


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FIGURE 8-2 A, AP x-ray in the plane of the scapula. An AP view in the plane of the scapula reveals the glenohumeral joint space and demonstrates whether the humeral head has a normal relationship to the glenoid fossa. It is most easily taken by positioning the patient’s scapula flat on the cassette and then passing the x-ray beam at right angles to the film, aiming at the coracoid process. B, A simulated x-ray view of a scapular AP view using a backlighted skeletal model. This view reveals the radiographic glenohumeral joint space and provides a good opportunity to detect fractures of the humerus or glenoid lip. C, Plain x-rays: True anteroposterior (Grashey) view. Intact glenoid rim. D, Erosion of anterior glenoid rim (dashed line).


(A modified from Matsen FA, III, et al: Shoulder surgery: Principles and procedures, Philadelphia, 2004, WB Saunders, p 7. B from Rockwood CA, et al: The shoulder, ed 4, Philadelphia, 2009, Saunders Elsevier.)



West point view (fig. 8-3)


For this variant of the AP view, the patient lies prone, arm in 90 degrees of abduction and elbow hanging over the edge of the examination table. The beam has an approximate 25 degrees anterior and medial tilt to demonstrate the anteroinferior glenoid rim. This view is difficult to obtain in noncooperative patients and in acute dislocation because of pain. The West Point view is also helpful in the workup of suspected glenoid bone loss because it provides an excellent view of the anterior glenoid rim.


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FIGURE 8-3 West Point axillary view helps provide excellent visualization of the anterior glenoid rim.


(Redrawn from Rokous JR, et al: Modified axillary roentgenogram. Clin Orthop Relat Res 82: 84–86, 1972.)



Stryker notch view (fig. 8-4)


This variant of the AP view is obtained with the patient lying supine, the arm abducted and externally rotated and the palm behind the head. The beam has approximately 10 degrees of cephalic inclination to display the posterolateral humeral head and document Hill-Sachs fractures. The Stryker notch view is important to help with evaluation of humeral head Hill-Sachs lesions. In addition, an internal rotation view also may be helpful to visualize Hill-Sachs injuries (Fig. 8-4, D).


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FIGURE 8-4 A, Apical oblique view. The shoulder is positioned as for an anteroposterior view in the plane of the scapula except that the x-ray beam is angled inferiorly at an angle of 45 degrees. This reveals the contour of the posterolateral humeral head and the anteroinferior glenoid. Solid arrow indicates Hill-Sachs defect. Dashed arrow indicates anteroinferior glenoid defect. B, Stryker notch view. C, Position of the patient for the Stryker notch view. The Stryker notch view is helpful for identification of humeral head bony injuries. The patient is supine with the cassette posterior to the shoulder. The humerus is flexed approximately 120 degrees so that the hand can be placed on top of the patient’s head. Note that the angle of the x-ray tube is 10 degrees superior. D, Defects in the posterolateral aspect of the humeral head are seen in three different patients with recurring anterior dislocations of the shoulder.


(A redrawn from Matsen FA, III, et al: Shoulder surgery: Principles and procedures, Philadelphia, 2004, WB Saunders, p 12. B redrawn from Hall RH, et al: Dislocations of the shoulder with special reference to accompanying small fractures. J Bone Joint Surg Am 41:489–494, 1959. C and D modified from the work of Hall RH, et al: Dislocation of the shoulder with special reference to accompanying small fractures. J Bone Joint Surg Am 41:489–494, 1959; appearing in Rockwood CA, et al: The shoulder, ed 4, Philadelphia, 2009, Saunders Elsevier, p 187.)



Axillary view (fig. 8-5)


The beam is directed toward the axillary cavity, with a medial tilt of approximately 15 degrees, and the arm is abducted. It depicts any anterior glenoid rim bone fragments, which may be related to a bony Bankart lesion, and erosion of the anteroinferior portion of the glenoid rim (see Fig. 8-5, C).


image image image image image

FIGURE 8-5 A, The dashed line outlines the normal shape of the anterior glenoid rim. B, The dashed line outlines the anterior glenoid bone loss. C, Patient and beam positioning for axillary view and modifications of the axillary view. An axillary x-ray reveals the glenohumeral joint space and the AP position of the humeral head and glenoid fossa. It is obtained by having the patient’s arm in abduction (e.g., holding onto an IV pole), the cassette on the superior aspect of the shoulder, and the x-ray beam passing up the axilla, aiming at the coracoids. D, The axillary view with a curved cassette, a method that is useful if the arm cannot be adequately abducted for a routine axillary view. E, The Velpeau axillary lateral x-ray technique. With the arm in a sling, the patient leans backward until the shoulder is over the cassette. F, A trauma axillary lateral radiograph. The arm is flexed on a foam wedge.


(C redrawn from Matsen FA, III, et al: Shoulder surgery: Principles and procedures, Philadelphia, 2004, WB Saunders, p 9. D redrawn from Rockwood CA, et al: The shoulder, ed 4, Philadelphia, 2009, Saunders Elsevier, p 667. E redrawn from Bloom MH, et al: Diagnosis of posterior dislocation of the shoulder with use of the Velpeau axillary and angle-up roentgenographic views. J Bone Joint Surg Am 49:943–949, 1967. F redrawn from Rockwood CA, et al: The shoulder, ed 4, Philadelphia, 2009, Saunders Elsevier, p 668.)



Transcapular (Y) view


In the Y view, the beam is trained directly onto the scapular plane, with a tilt of approximately 60 degrees compared to the AP view. This view provides information on the subacromial space and is performed in patients with posterior chronic dislocation because it demonstrates the static posterior dislocation of the humeral head with respect to the glenoid.



Dynamic x-ray examination


As suggested by its name, dynamic x-ray examination allows functional fluoroscopic study of the shoulder. The drawer test is performed with the patient awake or under general anesthesia. The contralateral shoulder also needs to be examined in patients with constitutional laxity or multidirectional instability. Anterior head movement up to 25% of its surface and posterior movement by 30% to 50% are held to be in the normal range. This examination is not easy to perform in acute conditions because of patient apprehension and pain.



Considerations


Plain films are the mainstay of the diagnostic workup for GH joint instability. Radiologist and surgeon experience and patient clinical condition and collaboration guide in the choice of views and techniques. X-rays specifically depict bone lesions, which are a common consequence of acute and chronic dislocation. Bone loss significantly affects the prognosis and management of instability, even though the extent to which it does so is debated. Hill-Sachs fractures are usually demonstrated on AP views with the arm in internal rotation, the larger ones with the arm in neutral or external rotation. Visualization of a Hill-Sachs fracture in external rotation has an adverse prognostic significance.


The true AP view affords diagnosis of superior subluxation and of other lesions of the acromioclavicular joint, collarbone, and ribs, as well as of glenoid hypoplasia, a rare congenital condition involving absence or marked reduction of the glenoid neck. Glenoid hypoplasia is often associated with recurrent dislocation; hence, there is x-ray evidence of GH arthritis, bone spurs, and intra-articular loose bodies. When excessive glenoid retroversion with respect to the humerus is the suspected cause of instability, a CT scan is the most informative examination. Finally, a ganglion cyst at the level of the lower glenoid region may be associated with pain and GH joint dislocation. In such cases, the frequent clinical finding of supraspinatus and infraspinatus hypotrophy is well documented on MRI. In overhead and thrower athletes, such as baseball pitchers, plain films can demonstrate specific lesions such as Bennett lesion, which involves a bony spur on the posterior-inferior surface of the glenoid. When Bennett first described it, in 1941, he attributed spur formation to traction of the brachial triceps on the infraglenoid tubercle and suggested a dedicated view with the beam tilted 5 degrees cephalad and the arm in 90 degrees of abduction and 90 degrees of external rotation. In fact, this lesion is due to ossification of the posterior band of the inferior glenohumeral ligament (IGHL), and the bone spur is due to the impact of the humeral head on the posterior glenoid with each throwing movement.

Related posts:

Open surgical solutions for posterior instability of the shoulder Clinical history, examination, arthroscopic findings, and treatment of multidirectional instability Recognition and management of combined instability and rotator cuff tears Open treatment of multidirectional instability—surgical technique Humeral head defects—biomechanics, measurements, and treatments Nonoperative rehabilitation for traumatic and atraumatic glenohumeral instability

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Jan 21, 2017 | Posted by in ORTHOPEDIC | Comments Off on Radiographic studies and findings

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