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Everything you need to know about Computed Tomography (CT) & CT Scanning


MDCT Arthrography of the Shoulder: Technique, Indications, and Applications with Emphasis on 3D CT

 

 

MDCT Arthrography of the Shoulder: Technique, Indications, and Applications with Emphasis on 3D CT

J Fritz, MD; E K Fishman, MD; J A Carrino, MD, MPH; K M Small, MD; C Winalski, MD; E McFarland, MD; L M Fayad, MD

The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions

 

Introduction

  • Although MR arthrography is the primary technique for the evaluation of the majority of shoulder abnormalities, computed tomography (CT) arthrography represents an accurate and powerful co-existing tool, which can be an important technique for the assessment of the rotator cuff, the capsulo-labral-ligamentous structures and the articular cartilage of the glenohumeral joint. In the post-operative patient, CT arthrography is the modality of choice.
  • CT arthrography of the shoulder requires two steps: the intra-articular injection of contrast medium and subsequent CT imaging of the shoulder. The intra-articularly injected contrast media increase the contrast resolution of CT and facilitate the visualization of intra-articular structures and conspicuity of intra-articular abnormalities. The introduction of sub-millimeter isotropic multidetector CT (MDCT) technology provided the crucial prerequisite for excellent spatial resolution and multiplanar capabilities, which markedly improved the diagnostic power of CT arthrography of the shoulder.
  • In this exhibit, we will detail essential techniques for successful MDCT arthrography of the shoulder, and review and illustrate the normal and abnormal MDCT arthrography appearances of the shoulder.

 

Indications for CT Anthrography in the Evaluation of Shoulder Abnormalities

Indications for CT Anthrography in the Evaluation of Shoulder Abnormalities

Table 1, Table 2, and Table 3 summarize the general and specific indications and the contraindications of MDCT arthrography of the shoulder.

 

Glenohumeral Injection Techniques

  • Although various non-image-guided techniques have been described for glenohumeral joint injections, the accuracy of these techniques are unclear. Because imaging-guided injections can achieve constantly high rates of intra-articular delivery of contrast media, many institutions use some type of imaging guidance.
  • Conventional fluoroscopy is frequently used because it is widely available and quick. CT-guided arthrography, however, is an accurate alternative, which confers the convenience of combining the contrast injection and CT imaging for the patient obviating the need for a fluoroscopy unit. Both modalities allow for the definite verification of intra-articular injection by direct visualization of the contrast media. Both, inadvertent injection of contrast media into extra-articular soft tissues simulating pathologic conditions and potential needle-induced injury of the cartilaginous labrum can be minimized.
  • The acquisition of standard radiographs or axial CT images of the shoulder prior to injection are helpful for the initial assessment of the anatomy, any hardware, and the presence of fractures, joint bodies and especially soft tissue mineralization, which can cause diagnostic errors by confusion with iodine contrast depositions or impede joint puncture (Figure 1, Figure 2, Figure 3).

 

Glenohumeral Injection Techniques

Glenohumeral Injection Techniques

Figure 1 (left). 32-year-old man presenting with a recent history of traumatic left shoulder injury. Axial MDCT of the left shoulder prior to joint puncture demonstrates an avulsion fracture (arrow) of the anterior inferior glenoid rim (bony Bankart lesion). An upper anterior injection was subsequently performed in order to avoid the injury.

Figure 2 (middle). 38-year-old man with remote history of football injury to the left shoulder. Axial MDCT of the left shoulder prior to joint puncture demonstrates an old avulsion fracture of the subscapularis tendon (arrow). A more medial and vertical needle path was subsequently selected for puncture.

Figure 3 (right). 44-year-old man presenting with left shoulder pain. Axial MDCT of the left shoulder prior to joint puncture demonstrates a focal soft tissue mineralization lateral to the biceps tendon (arrow), which should not be confused with contrast deposition on CT arthrography. Hence, it is helpful to acquire images prior to the injection.

 

Glenohumeral Injection Techniques

Glenohumeral Injection Techniques

Various approaches and needle access paths have been described, which can broadly be categorized into anterior and posterior approaches. The anterior joint capsule may be punctured at the upper medial third of humeral head, lower medial third of humeral head, between middle and lower thirds of glenohumeral joint space. A “classic anterior approach” with the patient in supine position is to target the centered joint space vertically at the junction of the middle and lower thirds of the humeral head (Figure 4, Figure 5).

Figure 4 (left). Fluoroscopy-guided contrast injection into the right glenohumeral joint using the “classic approach”. A: Frontal radiography scout demonstrates the target site (“X”) for joint puncture located between the upper two thirds and lower one third of the joint space. B: Frontal radiograph with needle in place confirms intra-articular contrast injection.

Figure 5 (right). CT-guided contrast injection into the right glenohumeral joint using the “classic approach”. A: CT topogram demonstrates a horizontal line intersection the upper two thirds and lower one third of the joint space. The arrow indicates the target site for puncture. B: Axial MDCT image with needle (white arrow) in place confirms intra-articular contrast (gray arrow) injection.

 

Glenohumeral Injection Techniques

Glenohumeral Injection Techniques

Because this classic approach frequently penetrates the subscapularis tendon and because of concerns of injury of primary stabilizers of the shoulder and penetration of areas where pathological lesions are frequently located, an anterior approach through the rotator interval and a posterior may be beneficial (Figure 6, Figure 7).

Figure 6 (left). CT-guided contrast injection into the left glenohumeral joint through the rotator interval. A: CT topogram demonstrates horizontal line drawn through the lower edge of the coracoid process. The arrow indicates the target site located near the medial aspect of the upper humeral head at level of the line. B: Axial MDCT image with needle in place confirms intra-articular contrast injection. B: Axial MDCT image with needle in place confirms intra-articular contrast (white arrow) injection.

Figure 7 (right). Fluoroscopy-guided contrast injection into the right glenohumeral joint using a posterior approach. A: Radiography scout with the patient in prone position and the right shoulder elevated by a wedge (Grashy view) showing the glenohumeral joint tangentially with radiopaque skin marker (arrow) indicating the skin entry site targeting the quadrant of humeral head within boundary of anatomic neck (interrupted line), thereby sparing the more medially situated glenoid labrum. B: Radiograph with needle in place (arrow) confirms intra-articular contrast injection.

Even with meticulous attention to detail, arthrography following glenohumeral joint replacement can be quite challenging. Post-surgical capsular changes may require alternative needle paths.

 

Intra-Articular Contrast Media

  • MDCT arthrography of the shoulder can be performed with single- or double-contrast technique . A single-contrast examination is most frequently performed with iodine contrast or, less often, with air. For a double-contrast examination, a smaller volume of iodine contrast is injected, followed by room air. With the latter technique, however, it may be difficult to achieve uniform coating of contrast throughout the shoulder joint. The favored technique depends on personal preference and experience.
  • The desired final iodine concentration is 150 mg/ml. Greater iodine concentrations may produce streak artifacts and cause reduced image quality. Iodinated contrast material may be diluted with saline or local anesthetic. 7-12 ml of iodine contrast solution is usually injected for a single-contrast examination, thereby avoiding capsular rupture, but ensuring good capsular distention. In adhesive capsulitis, pain during the injection may limit the total volume of contrast medium injected. For a double-contrast examination, a total of 4-8 ml of iodine contrast solution is injected, followed by 8-12 ml of room air.

 

Intria-Articular Contrast Media

  • It is advisable to obtain the CT as soon as possible after the injection to avoid resorption of contrast material, loss of capsular distension, and cartilage imbibitions. If CT cannot be performed within 30 min of the injection, 0.1–0.3 ml of a 1:1000 adrenalin solution may be added to the injectant to delay resorption. Some authors recommend passive joint motion after injection, although there is concern that this maneuver increases the risk of intra-articular fluid decompressing anteriorly into the subscapularis muscle, which may in turn decrease image quality and result in misinterpretations.

 

CT Acquisition

  • CT data are acquired with the patient in the supine position. The ipislateral shoulder should be as close to the center of the gantry as possible. The contralateral arm is preferably elevated and placed over the patient’s head to decrease beam attenuation, which helps to reduce artifacts, boost the signal-to-noise ratio and decrease radiation dose (Figure 8). If the contralateral arm cannot be elevated, the patient may be placed slightly obliquely in the z-axis in order to shift the contralateral humeral head superior to the beam path (Figure 9). Image volumes should extend superiorly from just above the level of the acromioclavicular joint to several centimeters inferior to the axillary recess (Figure 8, Figure 9).

 

CT Acquisition

  • A single standard acquisition with the ipsilateral arm adducted in neutral position or slightly externally rotated is usually sufficient for accurate image interpretation, especially using a CT dataset of isotropic resolution, as any desired display planes may be reconstructed from the original axial acquisition. Additional images in internal rotation or ABER (abduction and external rotation) position can be obtained for additional detail or if anterior instability or posterosuperior glenoid impingement is suspected (Figure 10). ABER views can improve visualization of the anterior and posterior glenoid and labrum, and deep surface of the supraspinatus tendon.
  • Respiratory artifacts can markedly degrade image quality (Figure 11). Image data acquisition should therefore be obtained in suspended respiration to limit motion artifacts. This is often easily accomplished as acquisition time on a 64 slice MDCT scanners is typically only 6 seconds.

 

CT Acquisition

CT Acquisition

Left to Right:
Figure 8. MDCT topogram prior to MDCT arthrography data acquisition of the right shoulder demonstrates the patient in supine position with contralateral arm elevated (black arrow) superior to the x-ray beam path (dashed lines) to reduce artifacts and radiation dose. White arrows indicate the thyroid located superior to the scanned sector.

Figure 9. MDCT topograms prior to CT arthrography data acquisition of the right shoulder demonstrates oblique patient position in order to move the contralateral shoulder superior to the x-ray beam path (dashed lines) to reduce artifacts and radiation dose. White arrows indicate the thyroid located superior to the scanned sector.

Figure 10. MDCT topogram prior to MDCT arthrography data acquisition of the right shoulder demonstrates ABER (abduction and external rotation) position. ABER views can improve visualization of the anterior and posterior glenoid and labrum, and deep surface of the supraspinatus tendon.

Figure 11. Coronal MDCT arthrography image of the right shoulder demonstrates wave-like artifacts (arrows) from respiratory motion.

 

MDCT Acquisition Parameters

  • When using sub-millimeter post-patient collimation for MDCT arthrography, streak artifacts from orthopedic hardware occur to a lesser degree. Additional operator-dependant parameters that can reduce streak artifacts include increasing peak voltage, increasing tube charge, extended CT scale and the use of smooth reconstruction filter (Kernel). However, the increased radiation dose, especially from increasing peak voltage needs to be considered. Frequently our proposed standard settings provide sufficient image quality.
  • Suggested standard acquisition parameters for MDCT arthrography of the shoulder are given in Table 4.
MDCT Acquisition Parameters

 

Image Reconstruction, Display and Rendering Techniques

  • Isotropic volume data sets allow optimal reformation in virtually any plane. First, standard 2 dimensional (2D) reformatted axial and corrected sagittal and coronal images are routinely reconstructed using the glenoid fossa as a reference (Figure 12). The best results are obtained with slice thickness of 2 mm and 1-2 mm distance between slice reconstructions for bone using an edge enhancing B60F sharp kernel, and slice thickness of 3 mm and 3 mm distance between slices reconstructions for soft tissues using a smooth B30 kernel.
  • Second, additional sets axial images with a slice thickness of 0.75 mm and 0.5 mm interslice distance are reconstructed in B60F sharp and B20F smooth kernels, which can be used for three dimensional (3D) evaluation on dedicated work stations and for multiplanar reconstructions, even after the raw data have been deleted. 3D evaluation using a dedicated work station is a critical part for detailed display and analysis of complex cases, and can guide further surgical management if there is need for revision of the initial surgery.

 

Image Reconstruction, Display and Rendering Techniques

  • Thin section axial slices can also be used for advanced data analysis using volume rendering and shaded surface techniques, which can deliver additional detail of complex scenarios and can be valuable in patient communication by helping patients understand their situation and the planned surgical technique and procedure (Figure 13). In addition, volume rendering technique is often capable of reducing beam hardening artifacts from orthopedic hardware.

 

Image Reconstruction, Display and Rendering Techniques

Image Reconstruction, Display and Rendering Techniques

Figure 12 (left). MDCT arthrography scout images of the left shoulder demonstrate slice orientations for standard 2D coronal (A) and sagittal (B) reformatted reconstructions. The best results are obtained with a slice thickness of 2-3 mm and 1-2 mm distance between slices.

Figure 13 (right). 68-year-old woman presenting with right shoulder pain. MDCT arthrography of the right shoulder. Volume rendered images demonstrate iodine contrast material in the subacromial-subdeltoid bursa (A, white arrow) and a full thickness rotator cuff tear (B, black arrow).

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Osseous structures MDCT superbly demonstrates the osseous anatomy of the shoulder region (Figure 14).
Figure 14. Axial MDCT arthrography images demonstrate the osseous anatomy of the right shoulder.

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Glenohumeral joint capsule and bursae
The glenohumeral joint capsule usually has two communications that are consistently present (Figure 15). The subscapularis recess communicates with the main glenohumeral joint capsule through the foramen of Weitbrecht, which is located between the superior and middle glenohumeral ligaments and/or through the foramen of Rouvière, which is located between the middle and inferior ligaments. The second communication is the opening at the bicipital groove between the humeral tuberosities for the tendon of the long head of the biceps and its synovial sheath. Detection of dislocation or disruption of the biceps tendon of the long head of the biceps is therefore easily diagnosed with CT arthrography.

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

  • The bursae of the shoulder are small pouches lined by synovium and normally contain a film of synovial fluid (Figure 16). Their purpose is to alleviate friction by creating a space between two tightly apposed structures that move relative to one another. Normally, bursae do not communicate with the glenohumeral joint capsule, although several anatomic variants exist. Familiarity with the bursal anatomy of the shoulder is important for the detection of abnormal communications, which usually indicate a pathological abnormality. The subacromial-subdeltoid bursa is the largest bursa of the shoulder. It facilitates movement between the rotator cuff tendons and the coracoacromial arch and between the rotator cuff tendons and the deltoid muscle. Medially it extends to the coracoid process. Its lateral and inferior extent beneath the deltoid muscle is more variable, and it may extend 3 cm below the greater tuberosity of the humerus. Anteriorly the subacromial-subdeltoid bursa extends to cover the bicipital groove. Accumulation of injected contrast in the subacromial-subdeltoid bursa is highly suggestive of a full-thickness rotator cuff tear.

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Muscles - The rotator cuff is composed of four muscles (subscapularis muscle, supraspinatus muscle, infraspinatus muscle and teres minor muscles) which surround the glenohumeral joint (Figure 17).
Figure 17. Axial and sagittal MDCT arthrography images of the right shoulder demonstrate muscle anatomy of the right shoulder.

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Capsulo-ligamentous structures
The lax and redundant fibrous capsule allows a wide range of motion. The capsular mechanism further consists of the rotator cuff, capsular ligaments, the synovial recesses, the glenoid labrum, and the scapular periosteum (Figure 18). Anteriorly, the joint capsule is reinforced by the superior glenohumeral ligament (SGHL), middle glenohumeral ligament (MGHL) and inferior glenohumeral ligament (IGHL), which are fibrous bands that strengthen the lax anterior capsule. There are normal variations in the development of the glenohumeral ligaments. The SGHL is the one most commonly identified. The SGHL originates from the upper pole of the glenoid cavity and base of the coracoid process and is attached to the MGHL, to the biceps tendon and to the labrum. The MGHL is the most variable. The MGHL inserts into the upper portion of the anterior labrum and directs laterally and caudally to reach the anterior region of the anatomic neck of the humerus. It may be poorly developed, totally absent, or cordlike, and its glenoid attachment may vary from directly on the labrum to the scapular neck. In the Buford complex a cord-like MGHL is associated with the absence of the anterior superior labrum. The IGHL is less variable. It is a broad ligament and composed of anterior and posterior bands, and the intervening axillary pouch.

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Figure 18. Sagittal and axial MDCT arthrography images of the right shoulder demonstrate the glenohumeral ligaments of the anterior capsule of the right shoulder.

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Hyaline Cartilage and Labrum
  • Hyaline cartilage covers the articular surfaces of the glenoid fossa and of the humeral head. The labrum is attached at the osseous glenoid fossa and likely increases joint stability. The glenoid labrum is imaged in cross section as a triangular structure, however configuration varies considerably. The base is attached to the peripheral edge of the glenoid fossa and hyaline cartilage while the apex projects laterally. The normal glenoid labrum presents with a wide variety of shapes, sizes and attachments. Usually the anterior labrum is thinner and more pointed, whereas the posterior labrum is commonly uniformly rounded in contour (Figure 19). The normal glenoid labrum is 3 mm high and 4 mm wide.
  • The long head of the biceps tendon attaches to the superior glenoid at the supraglenoid tubercle. Together with the superior glenoid labrum, it forms the biceps labral complex (Figure 20). Assessment of the int egrity of the biceps labrum complex is important because it is a major contributor to joint stability. At the superior labrum, a small separation between the hyaline cartilage and the labrum may exist and should not be interpreted as a posttraumatic lesion (Figure 21).

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

  • Occasionally the separation can be complete allowing communication between the joint cavity and subcoracoid recess (foramen infralabrum), which is located in the anterior superior location. In the Buford complex, a cord-like MGHL is associated with the absence of the anterosuperior labrum. Other anatomic variants of the anterior superior glenoid labrum are the sublabral recess and the sublabral foramen.
  • Diagnostic checklist
    A suggested diagnostic checklist for the interpretation of MDCT arthrography of the shoulder is a) osseous structures, b) rotator cuff, c) bicpes tendon and labral complex, d) glenoid labrum, e) capsular ligaments, f) glneohumeral joint, and g) extra-articular structures.

 

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Normal MDCT Anthrography Appearance of the Shoulder and Anatomic Variations

Figure 19 (left). Axial CT arthrography image of the right shoulder demonstrates the normal shape and dimensions of the anterior and posterior glenoid labrum.

Figure 20 (middle). MDCT arthrography of the right shoulder demonstrates a normal biceps labral complex.

Figure 21 (2x right). Coronal and axial MDCT arthrography images of the right shoulder demonstrate a normal biceps labral complex with a biceps labral sulcus. This sulcus should not be mistaken for detachment of the superior labrum.

 

MDCT Anthrography of the Abnormal Shoulder

Osseous structures
  • MDCT arthrography of the shoulder can readily assess shape, thickness and slope of the acromion and is very sensitive for the detection of acromioclavicular osteoarthritis (Figure 22).
  • An os acromiale is formed by joining of the acromion to the scapular spine by fibrocartilaginous tissue rather than bone (Figure 23). It is an anatomic variant with an approximate prevalence of 8% worldwide. CT is very sensitive for its detection and evaluates its size with high accuracy. An os acromiale frequently articulates with the clavicle and the acromion and can be implicated in the pathogenesis of anterior impingement syndrome and may require surgical management (Figure 24).
  • MDCT arthrography superiorly demonstrates the presence of mineralization and enthesophytes of the acromion which are potential causes of mechanical impingement of the rotator cuff, and is also helpful in the differentiation of ossification from simple thickening of the coracoacromial ligament (Figure 25).

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

Left to right:
Figure 22. 75-year-old woman with long-standing history of left shoulder pain. MDCT arthrography of the left shoulder demonstrates lateral downsloping of the acromion, which may narrow the supraspinatus outlet and contribute to impingement. Note contrast material in the subacromial-subdeltoid bursa indicating full thickness rotator cuff tear.

Figure 23. MDCT of the left shoulder in volume rendering technique demonstrates an os acromiale, which articulates with the clavicle and the acromion.

Figure 24. 38-year-old man with history of right shoulder pain arising from the acromioclavicular joint and subsequent fusion procedure of an os acromiale. Axial MDCT arthrography of the right shoulder demonstrates internal fixation of an os acromiale.

Figure 25. 51-year-old man (A) and 59-year-old woman (B), both presenting with shoulder pain. MDCT arthrography images of the left shoulder demonstrate a flat subacromial spur (a) and a spur extending from the acromioclavicular joint (b).

 

MDCT Anthrography of the Abnormal Shoulder

Rotator Cuff
  • Tears of the rotator cuff can be characterized as either complete or partial. Complete or full thickness rotator cuff tears extend through the entire rotator cuff, thereby creating an abnormal communication between the joint space and the subacromial sub-deltoid bursa (Figure 26).
  • Partial tears may involve the bursal or articular surfaces (Figure 26). Therefore, the typical MDCT arthrography appearance of a complete rotator cuff tear is intra-articularly injected contrast extending into the subacromial-subdeltoid bursa space through a defect in the rotator cuff tendons.
  • Tears of the rotator cuff can be systematically described, both on MDCT arthrography and arthroscopy. Descriptions include the affected tendons of the cuff (supraspinatus, infraspinatus and subscapularis) and the frontal and sagittal extent of the tear (Figure 27 and Figure 28). A massive rotator cuff tear involves at least two of the rotator cuff tendons.
  • MDCT arthrography detects complete and articular partial tears of the rotator cuff with a reported sensitivity of 96%, specificity of 95-100%, and an overall accuracy of 95-98%.

 

MDCT Anthrography of the Abnormal Shoulder

Rotator Cuff
  • MDCT arthrography was found to have a sensitivity of 99% and specificity of 100% for the diagnosis of supraspinatus tears, 97% and 100% respectively for infraspinatus tears, and 65% and 99% for the diagnosis of subscapularis tears.
  • MDCT arthrography has excellent diagnostic performance in the determination of the extent of rotator cuff tears when compared to intra-operative findings (Figure 38). Rotator cuff tears can be classified according to the greatest dimension as either small (<1 cm), medium (1–3 cm), large (3–5 cm), or massive (<5 cm). The dimensions of rotator cuff tears may have implications for selection of treatment and the surgical approach, postoperative prognosis, and tear recurrence.
  • MDCT arthrography can reliably measure the retraction of the tendon and assess for muscle atrophy and fatty degeneration (Figure 29). In the presence of a rotator cuff tear, together with the degree of retraction, atrophy and fatty infiltration are important prognostic factors in the anatomical and functional outcomes of rotator cuff repairs. Five degrees of fatty degeneration were described depending on the amount of fatty infiltration of the muscle. Surgical outcome is generally poor if the amount of fatty infiltration is equal to or greater than the amount of visible muscle tissue.

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

Figure 26 (top 4). 56-year-old woman presenting with right shoulder pain. Status post right arthroscopic rotator cuff repair 12 months ago. MDCT arthrography images demonstrate three dimensional measurement of the extent of a small full thickness tear of the infraspinatus muscle and subscapularis articular surface tear.

Figure 27 (bottom left). Diagram demonstrates sagittal determination of the affected tendons of the rotator cuff.

Figure 28 (bottom second from left). Diagram demonstrates the grading system for the coronal extent of a rotator cuff tear (supraspinatus) [32].

Figure 29 (2x bottom right). 52-year-old man with right shoulder pain. MDCT arthrography images demonstrate an intermediate full thickness tear of the supraspinatus muscle with atrophy and an intermediate degree of fatty infiltration.

 

MDCT Anthrography of the Abnormal Shoulder

Comparison to MR imaging
  • Because of the high spatial resolution, MDCT arthrography is very sensitive for the detection of low grade undersurface tears of the supraspinatus and infraspinatus tendon, which may be difficult to detect with MR arthrography.
  • Similar to MR arthrography using only T1-weighted images, MDCT arthrography has markedly decreased sensitivity for the detection of partial bursal surface tears and partial intrasubstance tears. In MR image examinations however, this can be compensated for by the additional acquisition of proton density-weighted and T2-weighted MR images.
  • MR imaging is more sensitive for the detection of full thickness rotator cuff tears, which are obliterated by granulation tissue, thereby preventing contrast material extension into the subacromial-subdeltoid bursa.
  • Reportedly, MDCT arthrography has lower sensitivity for isolated subscapularis tendon tears than MR imaging / MR arthrography. In our experience however, MDCT arthrography sensitivity is sufficient for the detection of this abnormality.
  • Although the degree of fatty degeneration is significantly related to the amount of atrophy of the respective muscles, CT degree of fatty degeneration correlates poorly with MR imaging findings, presumably due to inferior contrast resolution.

 

MDCT Anthrography of the Abnormal Shoulder

Capsulo-labral-ligamentous lesions and glenohumeral instability
  • Instability is defined as subluxation and dislocation of the glenohumeral joint during activities. Shoulder instability may be described according to the direction of the relative translation of the humeral head, which may be anterior, posterior, or inferior to the glenoid, or multidirectional, although anterior instability is most common. The demonstration of capsulo-labro-ligamentous lesions is essential to establish the diagnosis of anterior instability, especially when typical osseous lesions are absent. MR arthrography is the standard of reference for the labrum and the capsular ligaments, but CT arthrography provides a valuable assessment of the labrum, and to a lesser extent of the ligaments. The most reliable finding of a labral tear is the presence of contrast extending completely through the labrum, whereas a small amount of contrast undercutting the superior labrum is frequently normal.
  • MDCT arthrography of the shoulder has a high sensitivity for the detection of defects and detachment of the labor-ligamentous complex. Labral abnormalities of chronic instability include labral tears and detachment as well as absence of the labrum. The IGHL labro-ligamentous complex is most frequently torn in anterior dislocation of the shoulder.
  • MDCT arthrography of the shoulder detects capsulo-labro-ligamentous lesions with a reported sensitivity of 87-93%, specificity of 93-96%, and an overall accuracy of 90-95%.

 

MDCT Anthrography of the Abnormal Shoulder

Anterior instability
  • A Hill-Sachs lesion is a traumatic defect of the posterior, superior and lateral aspect of the humeral head related to a compression fracture of this contour against the anterior, inferior portion of the glenoid rim during dislocation (Figure 30). A Hill-Sachs lesion may be identified by radiography, but CT, MDCT arthrography and MR arthrography increase the rate of detection of small lesions and any associated cartilaginous lesions.
  • A “Bony Bankart” lesion is a traumatic anterior inferior lesion of the bony glenoid rim observed in more than 1/3 of patients who sustain direct impaction of the glenoid rim on the humeral head, or avulsion of the IGHL insertion (Figure 31).
  • MDCT arthrography of the shoulder has a high sensitivity for the detection of traumatic soft tissue Bankart lesions, which are defined as a traumatic avulsion of the anterior inferior labro-ligamentous complex, and stripping of the capsule from the glenoid (Figure 30).
  • MDCT arthrography of the shoulder is also helpful to define Bankart variants including Perthes lesions, anterior labro-ligamentous periosteal sleeve avulsion (ALPSA) lesions, glenolabral articular disruption (GLAD) lesion and humeral avulsion of the glenohumeral ligament (HAGL) lesions.

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

Figure 30 (2x left). 52-year-old man with right shoulder pain and history of right shoulder dislocation 15 years ago. MDCT arthrography images of the right shoulder demonstrate an old Hill-Sachs defect (A) and an old soft tissue Bankart lesion of the anterior glenoid labrum (A and B).

Figure 31 (2x right). 28-year-old man with history of traumatic right shoulder injury. MDCT arthrography images of the right shoulder demonstrate a surgically proven bony Bankart lesion.

 

MDCT Anthrography of the Abnormal Shoulder

SLAP lesions
  • Superior labral anterior posterior (SLAP) lesions are tears, which are usually centered to the attachment of the long head of the biceps tendon (biceps labral complex). SLAP lesions may be chronic or acute and may or may not be associated with instability. Superior labral tears may be commonly associated with persistent pain in athletes performing repetitive overhead motions (baseball, tennis, swimming) and abnormalities of the rotator cuff. Penetration of contrast material into labral defects is the most specific MDCT arthrography sign for a SLAP lesion (Figure 32, Figure 33).
  • Originally, 4 basic types of SLAP lesions were described. Over time several other types have been described and added (Table 5). Today, at least 11 SLAP subtypes have been described. The spectrum of SLAP lesions ranges from simple fraying over fragmentation of the biceps labral complex to bucket-handle and flap tears and extension of tears into the rotator cuff.

 

MDCT Anthrography of the Abnormal Shoulder

SLAP lesions
  • MDCT arthrography, MR imaging and MR arthrography frequently cannot accurately differentiate between the various SLAP types. For this reason, it may be more important to describe the positive and pertinent negative findings when reporting SLAP lesions than to accurately classify them (Table 6).
  • Because of the existence of several anatomic variants of the anterosuperior labrum (see above), differentiation from SLPA lesions may be challenging. While the presence of linear contrast in the labrum is a key finding, the orientation is important in differentiating a tear from a normal variant (Table 7). However, reliable differentiation between a normal biceps labral complex with a biceps labral sulcus anatomic variant and a SLAP lesion type 2 may not be possible.
  • Labral cysts are important secondary indicators of labral tears, however may be difficult to detect on MDCT arthrography.

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

Comparison to MR imaging MR arthrography is the standard of reference for the labro-bicipital complex and the capsular ligaments, but MDCT arthrography provides a valuable assessment of the labrum, and to a lesser extent of the ligaments. Reports using MDCT arthrography are limited, but more recent reports suggest excellent results with this technique underscore the effectiveness of MDCT arthrography both for the distinction of labral lesions from normal variants of the labro-bicipital complex and for the detection of SLAP lesions.

Figure 32 (2x left). 65-year-old man with history of remote traumatic shoulder injury. MDCT arthrography (left) and MR arthrography (right) images of the left shoulder demonstrate a tear of the biceps labral complex. Surgically proven SLAP 1. Figure 33 (right). 34-year-old man with history of acute traumatic shoulder injury. MDCT arthrography (left) and MR arthrography (right) images of the left shoulder demonstrate a tear of the anterior superior labrum with minimal displacement. Surgically proven SLAP 2.

 

MDCT Anthrography of the Abnormal Shoulder

Articular cartilage abnormalities
  • MDCT arthrography of the shoulder has excellent characteristics for delineation of the cartilage surface and detection of substantial cartilage lesions. Secondary to the intra-articular positive iodinated contrast solution, focal cartilage lesions are detectable as high attenuation filling defects, which are surrounded by low-attenuating normal cartilage.
  • Glenohumeral articular cartilage abnormalities can be graded using a modification of the Outerbridge and Noyes arthroscopy classification systems . This system is based on the following four parameters: integrity of the articular surface, depth of substance loss, location of the lesion, and diameter of the lesion (Table 9).
  • Sensitivities and specificities of MDCT arthrography of the shoulder range between 80% and 94% for the detection of grade 2 and higher cartilage lesions, and between 88% and 98% for the detection of grade 3 and higher cartilage lesions. There is favorable correlation of the grading of articular surfaces at MDCT arthrography and the grading at arthroscopy for grade 3 and higher cartilage lesions (Figure 34 and Figure 35).

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

Comparison to MR imaging
To the best of our knowledge, there are no studies comparing the diagnostic performance of MR imaging/arthrography and MDCT arthrography for the detection of articular cartilage lesions in the shoulder. One study, however, found similar diagnostic performances of MR imaging/arthrography and CT arthrography for articular cartilage of the knee. In our experience, MDCT arthrography may be advantageous for the detection of cartilaginous lesions of the shoulder, because of the variable MR signal characteristics of these lesions potentially causing difficulties in differentiating them from surrounding structures.

Figure 34 (left). 55-year-old man presenting with right shoulder pain and history of remote trauma. MDCT arthrography image of the right shoulder demonstrates a focal high grade cartilage defect in the posterior aspect of the glenoid with associated degenerative changes and subchondral cyst formation, compatible with grade 3 and higher cartilage lesion.

Figure 35 (right). 72-year-old man presenting with intractable left shoulder pain. MDCT arthrography image of the left shoulder demonstrates generalized cartilage loss of the glenohumeral joint in the setting of severe osteoarthritis, compatible with grade 3 and higher cartilage loss.

 

MDCT Anthrography of the Abnormal Shoulder

Post-operative imaging
  • MDCT arthrography of the shoulder is the method of choice for imaging patients with joint prostheses. MDCT results in minimal artifacts that allow for sufficient assessment of prosthetic and periprosthetic abnormalities, rotator cuff abnormalities and the capusulo-labral complex (Figure 36, Figure 37).
  • MDCT arthrography can be used to evaluate the post-operative rotator cuff, more easily than with MR imaging or MR arthrography when artifacts are present in the tendons or osseous surfaces due to the presence of adjacent orthopedic hardware, such as metal anchors or screws (Figure 37).
  • Of note, a repaired rotator cuff does not usually show a watertight seal at CT arthrography, and contrast material often leaks into the subacromial–subdeltoid bursa, outlining both the superficial and deep surfaces of the rotator cuff tendons, which allows evaluation of the thickness of the repaired tendon.

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

Figure 36 (top). 61-year-old man with the history of left shoulder osteoarthritis and left total shoulder arthroplasty 4 months ago, presenting with left shoulder pain. MDCT arthrography images of the left shoulder with elevated left arm demonstrate intra-articular iodine contrast surrounding the glenoid component of the shoulder prosthesis indicating loosening, which was subsequently surgically-proven. Elevation of the left arm is helpful to decrease the amount of streak artifacts created by the humeral metal component.

Figure 37 (bottom). 69-year-old woman with history of left proximal humerus fracture with plate and screw fixation five years ago, presenting with left shoulder pain and loss of motion. MDCT arthrography images of the left shoulder demonstrate an intermediate-grade partial undersurface tear of the supraspinatus tendon. Status post internal fixation of remote proximal humerus fracture.

 

Comparison to MR imaging
  • In the post-operative patient, MDCT arthrography can be more accurate in comparison to MR imaging and MR arthrography. For rotator cuff abnormalities, reported sensitivities, specificities, and accuracy for MDCT arthrography are 94%, 100% and 96%, respectively; and 19-25%, 25%, and 21-25%, respectively, for MR imaging and MR arthrography. For capsulo-labral complex abnormalities, reported sensitivities, specificities, and accuracy for MDCT arthrography are 92%, 88-94% and 89-93%, respectively; and 25%, 25%, and 25-29%, respectively, for MR imaging and MR arthrography.

 

MDCT Anthrography of the Abnormal Shoulder

MDCT Anthrography of the Abnormal Shoulder

Intra-articular bodies
MDCT arthrography of the shoulder detects chrondral, osseous and osteochondral joint bodies with high sensitivity (Figure 38, Figure 39). Intra-articular bodies may be seen in numerous conditions including degenerative joint disease, rheumatoid arthritis, (osteo)chondromatosis, osteonecrosis, calcium pyrophosphate dihydrate crystal deposition disease and osteochondritis dissecans.

Figure 38 (left). 63-year-old man with left shoulder pain. MDCT arthrography image of the left shoulder demonstrates an osteochondral

Figure 39 (right). 72-year-old man with right shoulder pain. MDCT arthrography image of the right shoulder demonstrates osteochondral joint bodies in the bice ps tendon sheath. Note full thickness rotator cuff tears and advanced degenerative changes.

 

Summary

This exhibit describes and illustrates the normal MDCT arthrography appearance of the shoulder, the technical parameters for successful MDCT arthrography of the shoulder and its numerous indications. The development of isotropic data sets and 3D capabilities have markedly improved the quality and the diagnostic potential of this technique. MDCT arthrography is the imaging test of choice for the assessment of the post-operative patient and may emerge as a superior diagnostic technique for a number of indications. At this time, MDCT arthrography remains an accurate rival to MR arthrography for the detection of a wide variety of abnormalities.
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