Sports Medicine: Just the Facts

the T 1 -weighting; areas of contrast enhancement will be

bright against an overall low signal intensity back-

ground. Contrast-enhanced imaging is often used in

tumor imaging as well to evaluate for osteomyelitis.

• MR arthrography is a technique whereby gadolinium
  is injected intra-articularly. The theory of MR arthrog-
  raphy is to create a conspicuous (bright) joint effu-
  sion, that can help outline areas of potential pathology
  (Zlatkin, 1999; Beltran et al, 1997; Helgason,
  Chandnani, and Yu, 1997).
  •Patients with orthopaedic hardware ( joint prostheses,
  fracture plates, and screws) can be imaged with MR.
  Techniques to reduce regional magnetic susceptibility
  should be performed to improve image quality, such
  as using fast spin echo imaging as opposed to routine
  spin echo and fast inversion recovery as opposed to
  frequency selective fat suppression as a water sensitive
  pulse sequence (Tartaglino et al, 1994; Potter et al,
  1996; White et al, 2000; Sofka et al, 2003) as the latter
  is more sensitive to magnetic field inhomogeneities
  (i.e., in the presence of metal).

SHOULDER

• High sensitivity and specificity of MR of the shoulder
  for diagnosing rotator cuff pathology has been repeat-
  edly demonstrated (Zlatkin et al, 1989; Burk et al,
  1989; Iannotti et al, 1991). The utility of fast spin
  echo imaging with resultant decreased examination
  time for diagnosing rotator cuff tears has also been
  validated (Carrino et al, 1997).


• Normal tendons are seen as linear hypointense (dark)
  bands of tissue with no internal signal on all pulse
  sequences.
  •Tendinosis is diagnosed by observing a change in the
  morphology of the tendons, to include thickening, and
  increased signal intensity within the substance of the
  tendon.
  •Tendon tears, including those of the rotator cuff, are
  diagnosed by visualizing a discrete, focal area of
  tendinous discontinuity, often with a fluid-filled gap.


• The degree of tendon slip retraction, if any, should be
  noted as well as any possible muscle atrophy in cases
  of full thickness tears.


• Secondary signs of rotator cuff tears include fluid dis-
  tention of the subacromial-subdeltoid bursa and
  muscle atrophy, often seen in the setting of chronic
  full thickness tears.


• Muscle atrophy is diagnosed on MR as fatty infiltra-
  tion of the muscle (areas of high signal intensity on
  T 1 -weighted images) as well as thinning of the
  muscle and decreased muscle bulk (Bredella et al,
  1999).
  
  
  • Care should be taken in interpreting areas of abnormal
    signal intensity in tendons that are recently post
    repair, as areas of abnormal signal or frank tendon
    defects can persist for some time (Zanetti et al, 2000).
  
  
  • One of the most common indications for MR imaging
    of the shoulder is for cartilage evaluation, whether this
    be the articular cartilage or the fibrocartilaginous
    labrum.
  
  
  • Some authors have demonstrated good success with
    diagnosing labral tears with MR arthrography (Jee et al,
    2001); however, with appropriate pulse sequences,
    unenhanced fast spin echo imaging is highly reliable
    and accurate in diagnosing labral pathology (Gusmer
    et al, 1996; Connell et al, 1999).
  
  
  • MR imaging with appropriate imaging parameters and
    surface coils can produce high resolution images of
    articular cartilage. Areas of minimal fibrillation, soften-
    ing, or even focal cartilage defects can be evaluated,
    without the use of intra-articular contrast (Figs. 43-1(a),
    43-1(b)).
  
  
  • In the setting of the unstable shoulder, MR imaging
    can provide information as to the integrity of the
    glenohumeral ligaments, the joint capsule as well as
    any possible osseous pathology.
  
  
  • After an anterior dislocation, MR can demonstrate
    acute osseous abnormalities (Hill Sachs fractures) as
    well as soft tissue injuries such as an anteroinferior
    labral tear (Bankart lesion) (Fig. 43-2).
    •Paralabral cysts can occur in the setting of a labral tear
    or a degenerated labrum. MR arthrography is of lim-
    ited use in diagnosing a paralabral cyst as the intra-
    articular contrast does not often extend into or
  
  
  
  

258 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE

FIG 43-1(a) Oblique coronal fast spin echo image of the shoul-

der demonstrating focal chondral shearing injury at the superior

aspect of the humeral head (arrow).