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Neil Roach, MD
Shoulder Mri
1. What magnetic resonance imaging (MRI) planes are used for evaluating the
shoulder?
Because the scapula is attached to the chest wall at approximately 45 degrees, oblique sagittal and oblique coronal
planes are used to evaluate the shoulder. Axial images are also obtained.
2. Name the four muscles of the rotator cuff.
The supraspinatus, infraspinatus, and teres minor attach to the greater tuberosity of the humeral head. The
subscapularis tendon attaches to the lesser tuberosity.
3. What is impingement syndrome?
This condition is caused by entrapment of the supraspinatus tendon, biceps tendon, and subacromial-subdeltoid bursa
between the humeral head and coracoacromial arch. It is thought that 95% of rotator cuff tears are related to chronic
impingement. The diagnosis of impingement is made clinically.
4. In what age group do rotator cuff tears most commonly occur?
Rotator cuff tears are rare in healthy individuals younger than 40 years old. Impingement syndrome is a chronic process,
beginning at about age 25 years, that causes degeneration of the rotator cuff tendons. Rotator cuff tears can be seen in
pitchers and weightlifters before age 40 years.
5. What is the typical MRI appearance of a rotator cuff tear?
Increased T2 signal (fluid) is seen within the tendon (
Fig. 43-1
). Normal tendons have low signal intensity on all pulse
sequences.
A
B
Figure 43-1.
A and B, Oblique coronal proton density (A) and fat-suppressed T2-weighted (B) images of the right shoulder at the anterior
leading edge of the supraspinatus tendon. A small focal tear (arrow) is seen where the supraspinatus tendon (which should be dark) inserts on
the greater tuberosity. On T2, fluid is seen in the region of the tear.
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Musculoskeletal Radiology
A
B
Figure 43-2.
A, Axial fat-suppressed T2-weighted image shows an osseous defect in the anterior-inferior aspect of the glenoid, a Bankart
lesion.
B, Axial proton density image shows a defect in the posterior-lateral aspect of the humeral head (arrow), representing a Hill-Sachs
deformity resulting from prior anterior-inferior humeral dislocation.
6. Which tendon of the rotator cuff is most commonly torn?
The supraspinatus is most commonly torn. Most tears occur in the critical zone of the tendon, which is a relatively
hypovascular area of the tendon that is approximately 1 to 2 cm proximal to the insertion of the supraspinatus tendon
on the greater tuberosity.
7. What MRI features indicate that a rotator cuff tear is chronic?
A high-riding humeral head in close proximity to the undersurface of the acromion indicates a chronic rotator cuff tear.
This can be seen on radiographs or MRI. Atrophy of muscles can be seen on MRI. This is appreciated by fatty infiltration
on T1-weighted images and decreased muscle bulk.
8. What are Hill-Sachs and Bankart deformities?
Both of these deformities are secondary to anterior dislocations. The Hill-Sachs lesion is an impaction fracture of the
posterolateral aspect of the humeral head and is seen best on axial images above the coracoid process. The Bankart
lesion is defined as an injury to the anterior-inferior glenoid and can be an osseous or nonosseous abnormality. Bankart
lesions are also best appreciated on axial images (
Fig. 43-2
).
9. What other shoulder abnormalities can be diagnosed on routine shoulder MRI?
Fractures, biceps tendon tears or dislocations, glenohumeral and acromioclavicular osteoarthritis, glenoid labral tears,
joint effusion, osteonecrosis, and osteomyelitis all can be diagnosed on routine shoulder MRI.
10. What is a SLAP lesion?
SLAP stands for superior labrum anterior and posterior. A SLAP lesion is a type of glenoid labral tear that extends
anteriorly and posteriorly. It is usually seen in athletes who throw or after shoulder trauma. Subtle SLAP lesions may be
difficult to diagnose on routine MRI. Magnetic resonance arthrography (MRA) increases the sensitivity for detecting these
abnormalities.
Key Points: Shoulder MRI
1. Three primary diseases can be seen on MRI of the shoulder: osteoarthritis, rotator cuff tears, and
abnormal structures related to the clinical diagnosis of instability.
2. Radiographs should be obtained before MR images. Many times, rotator cuff tears can be diagnosed
by the narrowing of the distance between the undersurface of the acromion and humeral head.
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shouldeR MRi
11. Which is better for the detection of calcific tendinitis, radiographs or MRI?
Calcific tendinitis is a type of tendon pathology seen around the shoulder. It is formally known as calcium hydroxyapatite
deposition disease. The shoulder is the most common site of involvement. On MRI, the nodular calcium deposits show
low signal intensity on all pulse sequences. The involved rotator cuff tendons may show focal thickening related to the
calcified nodules. It can be difficult to appreciate calcific tendinitis on MRI, but this diagnosis can be clearly seen on
radiographs.
12. What is meant by glenohumeral instability?
Patients in whom the humeral head slips or subluxates out of the glenoid are said to have instability during activities.
Orthopedic surgeons describe instability by direction: anterior, posterior, or multidirectional. Instability can also be
characterized as traumatic or atraumatic. Anatomic instability refers to subluxation or dislocation of the humeral head.
Functional instability refers to pain, clicking, or locking of the shoulder. The most common glenohumeral instability is
anterior instability from a previous dislocation.
B
iBliography
[1] J. Beltran, D.H. Kim, MR imaging of shoulder instability injuries in the athlete, Magn. Reson. Imaging Clin. N. Am. 11 (2003) 221–238.
[2] J.F. Feller, et al., Magnetic resonance imaging of the shoulder: review, Semin. Roentgenol. 30 (1995) 224–240.
[3] P.A. Kaplan, R. Dussault, M.W. Anderson, N.M. Major, Musculoskeletal MRI, Saunders, Philadelphia, 2001, pp. 175–176.
[4] M. Rafii, et al., Rotator cuff lesions: Signal patterns at MR imaging, Radiology 177 (1990) 817–823.