Radiography

Basic radiography has evolved from film-screen radiography, which is still in use today, to increasingly available digital and computed radiography techniques, which are more amenable to manipulation, image transfer and storage, and viewing on workstations.

Standard radiographic projections of the shoulder include an AP (anteroposterior) and lateral view ( Y -view). Correctly performed AP and lateral views allow assessment of glenohumeral and acromioclavicular alignment as well as of osseous structures at the shoulder. Radiographs are of particular value in the initial assessment of trauma where fracture or dislocation is suspected, and in the assessment of arthritis, but they are also useful in other cases such as tumor evaluation and calcific rotator cuff tendinosis with hydroxyapatite deposition disease (HADD; Fig. 14-1 ). Further views of the shoulder are also of value in certain instances; for example, a transthoracic lateral view and axillary (axial) view.

Calcific tendinosis of the rotator cuff and associated bursitis. A, Anteroposterior radiograph of the shoulder demonstrates calcific foci at the distal supraspinatus tendon consistent with calcific tendinosis or hydroxyapatite deposition disease (HADD). B, Coronal fat-saturated T2-weighted image of the shoulder in the same patient demonstrates foci of low ( black ) signal in the distal supraspinatus tendon ( arrow ) extruding into the adjacent subacromial/subdeltoid bursa with associated reactive bursitis ( fluid bright signal ).

Standard views of the elbow include AP and lateral radiographs. Oblique AP views may be of value in assessing for suspected radial head fractures not seen on conventional views.

Arthrography

Shoulder arthrography still has a role in the assessment of rotator cuff tears and adhesive capsulitis, although recently it is rarely used in isolation, being more often combined with MRI (direct MR arthrography) or sometimes CT arthrography. MR arthrography is usually performed when labral pathology is suspected and is of particular use in patients with instability signs and symptoms.

For shoulder arthrography, a spinal needle (20–22 gauge) is used to gain access to the shoulder joint, using an anterior or posterior approach under fluoroscopic guidance ( Fig. 14-2 ). The intra-articular position is confirmed with injection of a small amount of iodinated contrast medium, which is typically followed by 14 mL of dilute gadolinium when performing MR arthrography. Undiluted iodinated contrast material is injected when performing CT arthrography. Arthrography of the elbow, usually in association with MR (direct MR arthrography), is used in the assessment of medial and lateral stabilizing ligament integrity and in the assessment of cartilage loss and intra-articular bodies.

Shoulder arthrogram. For shoulder arthrography a 20- or 22-gauge spinal needle is used to gain access to the glenohumeral joint. High-density iodinated contrast material is seen flowing easily away from the needle tip into the joint, confirming intra-articular position.

Computed Tomography

The latest generation CT scanners use multiple detector row arrays. Multidetector CT (MDCT) is a major improvement in CT technology because the activation of multiple detector rows positioned along the patient’s longitudinal axis allows for simultaneous acquisition of multiple slices. This also enables acquisition of thinner slices than were previously possible, allowing generation of exquisite multiplanar reformats ( Fig. 14-3 ). In the setting of orthopedic prosthetic hardware, this technology results in decreased artifact.

Comminuted intra-articular fracture. A, Coronal 2D CT image of a comminuted intra-articular right humeral head and glenoid fracture. B, Reconstructed 3D CT image in the same patient improves appreciation of fracture extent and pattern, assisting in operative planning.

CT allows precise characterization of fractures at the shoulder and elbow, defining degree of comminution and displacement, and identifying intra-articular osseous bodies if present. CT arthrography is an alternative to MR arthrography, allowing assessment of rotator cuff tears (especially full-thickness), labral tears, and cartilage loss at the glenohumeral joint ( Fig. 14-4 ). CT may also be used for image-guided intervention.

CT arthrogram of the shoulder. In patients for whom MRI is contraindicated, valuable information can be obtained with CT arthrography. In this instance iodinated contrast medium is seen to fill the inferior axillary recess of the glenohumeral joint as expected ( curved arrow ). However, contrast material is also seen to fill the subacromial/subdeltoid bursa ( straight arrow ), secondary to a full-thickness rotator cuff tear (tear not shown).

Ultrasound

US is the medical imaging modality used to acquire and display the acoustic properties of tissues. A transducer array (transmitter and receiver of US pulses) sends sound waves into the patient and receives returning echoes, which are converted into an image.

For musculoskeletal imaging of more superficial structures (tendons, ligaments), a high-frequency beam with a smaller wavelength provides superior spatial resolution and image detail. Thus, use of an appropriate transducer is of critical importance in performing shoulder and elbow imaging. Higher-frequency transducers are now available, ranging from 7.5 MHz up to as much as 15 MHz.

The acquisition of high-quality US images depends on operator experience, but in the right hands US can be a powerful tool in the assessment of a wide range of shoulder and elbow pathologies. US has shown increased utility for diagnostic and therapeutic procedures and for specific clinical concerns by providing more infrastructural detail more cost-effectively through improved transducer technology. ^, US is best used when a clinical question is well formulated and the condition is dichotomous (e.g., Is there a full-thickness rotator cuff tear or not?). US is also excellent for assessment of injuries that are only observed during certain motions or in certain positions. For example, ulnar nerve subluxation can be documented during flexion and extension. Performing percutaneous interventions with US ensures accurate needle tip placement and helps direct the needle away from other regional soft-tissue structures and neurovascular bundles. Applications of US at the shoulder and elbow are depicted in Boxes 14-1 and 14-2 .

Magnetic Resonance Imaging

MRI is the workhorse of musculoskeletal imaging throughout the body, including the shoulder and elbow. MRI relies on the magnetic properties of the proton and does not involve ionizing radiation. It utilizes a strong magnetic field (most commonly 1.5 T) to align these protons. Their energy level is altered by a transmitted radiofrequency (RF) pulse, after which they are allowed to relax back to their original state, releasing energy. This energy is used to formulate an image based on the different relaxation properties of tissues. Various “sequences” are prescribed to focus on the different relaxation properties of the tissues in question. The main components of an MRI system include a strong magnetic field, coils (to transmit and receive RF signals), and gradients to localize signals quickly. MRI technology continues to evolve, with recent developments focusing on higher field strength magnets (3 T) and improved coils and gradients. Limitations of MRI include patient contraindications ( Box 14-3 ), metallic susceptibility artifact from hardware, and patient intolerance secondary to claustrophobia.

The principal applications of MRI of the shoulder and elbow are show in Boxes 14-4 and 14-5 . Direct MR arthrography is the favored technique for examination of possible shoulder labral tears. It involves direct injection of dilute gadolinium under fluoroscopic guidance as described earlier. It is also of value in assessing the rotator cuff and the stabilizing structures of the elbow. Indirect MR arthrography of the shoulder and elbow involves an IV injection of gadolinium, which diffuses into the joint cavity causing an “arthrographic” effect.

Box 14-4

Shoulder MRI Applications

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  Rotator cuff pathology

  
  
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  Labral or capsular injury (best using direct MR arthrography)

  
  
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  Rotator cuff interval lesions

  
  
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  Muscle and other tendon tears

  
  
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  Nerve pathology and impingement

  
  
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  Osseous and soft tissue neoplasms

  
  
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  Infection

MR, magnetic resonance.

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