•AC joint sprains are generally classified into three types:
•Type I: Partial disruption of the AC joint (capsular
hyperintensity on fat suppressed MR sequences)
•Type II: Partial injury to the AC joint capsule and
coracoclavicular ligament. The coracoclavicular lig-
ament is generally seen to best advantage on oblique
sagittal or oblique coronal MR images.
•Type III: Complete disruption of the AC joint cap-
sule and coracoclavicular ligament
ELBOW
- One of the more common indications for MR imaging of
the elbow is for epicondylitis. While the diagnosis of epi-
condylitis can be made clinically, the advantage of MR
is that it can provide detailed morphologic information
about the status of the tendons, including possible tendon
tears, as well as reactive edema in the epicondyle. MR
can also exclude other possible causes of elbow pain
mimicking lateral epicondylitis, for example, such as
compression of the posterior interosseous nerve. - Epicondylitis is actually a misnomer; there is no
active inflammatory component involved (Potter et al,
1995). At histology, there is primarily neovasculariza-
tion and mucoid degeneration of the tendon (Potter
et al,1995).
•Degeneration of either the extensor or flexor tendons
about the elbow is demonstrated by thickening, hyper-
intensity, and fraying of the tendon fibers (Fig. 43-4).
In the case of lateral epicondylitis, the extensor carpi
radialis brevis tendon, with or without involvement of
the more laterally located extensor carpi radialis
longus is the primary tendon affected.- The elbow can be imaged either with the arm at the
side or with the hand over the head. Pulse sequences
260 SECTION 4 • MUSCULOSKELETAL PROBLEMS IN THE ATHLETE
FIG 43-3 Axial fast spin echo image of the shoulder at the level of the mid glenohumeral joint
demonstrates a small cyst arising from a tear in the posterior labrum (thin white arrow). Axial image
at a slightly more inferior level (left) demonstrates the multilobulated paralabral cyst (arrow).
FIG 43-4 Coronal gradient echo image of the elbow demon-
strates moderate tendinosis of the extensor tendons at the
humerus (thick white arrow). Note the normal appearance of the
medial collateral ligament (thin white arrow).