Which is more useful, the "full can test" or the "empty can test," in detecting the torn supraspinatus tendon?

The purpose of this study was to determine the clinical usefulness of the f ull can and empty can tests for determining the presence of a torn supraspi natus tendon. The two tests were performed in 143 shoulders of 136 consecut ive patients. In each test, the muscle strength was determined by manual mu scle testing, and the presence of pain during the maneuver was recorded. We interpreted the tests as positive when there was 1) pain, 2) muscle weakne ss, or 3) pain or muscle weakness or both. Shoulders were examined by high- resolution magnetic resonance imaging with 95% accuracy for full-thickness rotator cuff tears. There were 35 shoulders with full-thickness tears of th e supraspinatus tendon. The accuracy of the tests was the greatest when mus cle weakness was interpreted as indicating a torn supraspinatus tendon in b oth the full can test (75% accurate) and the empty can test (70% accurate). However, there was no significant difference between the accuracy of the t ests when this criterion was used. Pain was observed in 62 shoulders (43%) during the full can test and in 71 shoulders (50%) during the empty can tes t, but the difference was not statistically significant. Muscle weakness sh ould be interpreted as indicative of supraspinatus tendon tear. Using this indicator, both tests are equivalent in terms of accuracy, but considering pain provocation, the full can test may be more beneficial in the clinical setting.