Background: The humeral head of Japanese elderly people with rotator cuff tear is smaller in diameter than that of Westerners. The current classification, divided into 4 groups: small < 1cm, medium < 3cm, large < 5cm, and massive > 5cm, is not proper in Japanese people. The difference of classification has an influence on the results of treatment for rotator cuff tears. Moreover the method of the measurement of the torn cuff size varies. Therefore we examined the diameter of the humeral heads of Japanese elderly people and the torn cuff sizes on MRI and indicate more proper classification of the rotator cuff tear for Japanese.
Methods: We examined 93 shoulders with rotator cuff tear ( average age was 69.9y.o, 44 ∼ 89y.o ) on MRI. The diameter of the humeral heads were measured by coronal and axial view on MRI. The length (b) and width (F) of rotator cuff tears were measured and the relationship between these two was evaluated by linear regression analysis and the Pearson's correlation coefficient.
Results: The average diameter of humeral head was 4.04cm (3.21 ∼ 4.83).
The length (b) and width (F) of rotator cuff tears was 2.41cm, 1.72cm on average respectively. Linear regression analysis was b=0.7468+0.9688F. Correlation coefficient was 0.642. P < 0.001.
Discussion: We conclude that the new classification as below is more proper for Japanese elderly people with rotator cuff tear. Small tear is less than 1cm, medium is 1 to 2cm, large is 2 to 4 cm, massive is more than 4 cm. In classification, the length is easy to measure.
