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"There is more than meets the eye"— a nice summary of the ability of MRI to peer deep inside tissues.
If we compare MRI and arthroscopy, it is clear that the arthroscopist has an unparalleled visualization of surface anatomic features. Once the arthroscope is introduced into a joint, the surgeon has a marvelous view of the surfaces of cartilage, ligaments, bone, and soft tissue. While diagnostic arthroscopy is a powerful tool, it is important to remember that it only sees what is on the surface.
MRI does not approach the resolution that arthroscopy provides, but enables us to look inside tissues. Exclusive reliance on what is seen at arthroscopy can lead to underestimation of pathology.
In this case, a 36 year-old female with shoulder pain was referred for an MR arthrogram. Coronal T1 weighted images with fat saturation demonstrate a SLAP lesion (yellow arrows). There is also globular hypointense signal within the distal supraspinatus tendon (red arrows), consistent with an area of calcification within the tendon. Calcification in this area was confirmed by a CT scan (not shown).
At arthroscopy, the SLAP tear was repaired, but the calcification within the substance of the tendon could not be observed. It is clearly present, but because it is within the tendon, it was not apparent at arthroscopy.
In this case, there was no edema within the tendon or in the peritendinous tissues on MRI, suggesting that this was a clinically silent area of calcification, rather than active calcific tendinitis. The patient responded well to her SLAP repair, and became pain-free postoperatively.
The radiologist should remember that the surface resolution of arthroscopy far exceeds that of MRI. The surgeon should remember that all that is important does not meet the eye of the arthroscopist. Thus, MRI and diagnostic arthroscopy are complementary techniques. Melding the information gleaned from each discipline provides the orthopedic surgeon with maximal information.
Vic David MD