Q: The MRI I had taken of my right shoulder showed that my rotator cuff tear (repaired 10 years ago) was no longer whole. Somewhere along the line, it tore again. I never felt a thing and the arm works just fine. Is it possible they misread the MRI?
A: A tendon rerupture usually shows up on an MRI as an empty space where there is a gap between the bone where the tendon should be attached and the tendon itself. The end of the torn tendon is called the tendon stump. Usually this empty space is filled with fluid (which shows up on the MRI with a specific signal intensity to identify it as a fluid-filled spot).
So, although it is possible that your MRI was misread, it's not likely. The signs of rerupture are pretty clear. Now, it is possible that the tear is only partial, in which case, you might not lose noticeable motion or strength.
In a recent study from Germany, 21 patients with an isolated subscapularis tear were followed from before to after surgery. The surprising finding from this study was that although 20 of the 21 patients had an intact repair and improved strength, one-fourth of those same patients had atrophy (wasting) of the upper portion of the subscapularis muscle.
The second half of the surprise was that none of these patients had any functional losses because of the muscle weakness. That could be the case with you as well. Sometimes when one part of the rotator cuff is deficient, the shoulder complex compensates and manages to keep everything moving in a way that seems fairly normal.
It's only over time or when under stress (e.g., lifting weights or doing heavy manual labor) that the insufficiency (weakness) becomes apparent or causes problems. Some experts advise having the tendon rupture repaired before it comes to that. Others adopt more of a wait-and-see approach.
Although not very often, mistakes can be made and the wrong MRI results are recorded. If you are truly not sure that the MRI was read properly, ask your surgeon to review the records with you.
Reference: Christoph Bartl, MD, et al. Subscapularis Function and Structural Integrity After Arthroscopic Repair of Isolated Subscapularis Tears. In The American Journal of Sports Medicine. June 2011. Vol. 39. No. 6. Pp. 1255-1262.