The supraspinatus occupation ratios of both the ≥ 50% articular- and bursal-side partial-thickness rotator cuff tears were low and the infraspinatus occupation ratio of the ≥ 50% bursal-side partial-thickness rotator cuff tears was low.

Abstract

The purpose of this study was to analyze the relationship between the occupation ratio and partial-thickness rotator cuff tears. The study included and retrospectively investigated 683 patients with partial-thickness rotator cuff tears between 2013 and 2017. Fifty patients with impingement syndrome were also enrolled as the control group for normal-population comparison. The participants were divided into five groups: Group A, control group; Group B, < 50% articular-side tears; Group C, ≥ 50% articular-side tears; Group D, < 50% bursal-side tears; and Group E, ≥ 50% bursal-side tears. Muscle volume was evaluated by measurement of each occupation ratio of the supraspinatus and infraspinatus tendons on the most lateral view of the T1-weighted oblique-sagittal images in which the scapular spine remained in contact with the scapular body. Fifty patients were enrolled in Group A. A total of 683 patients with Partial thickness rotator cuff tear were divided and classified into the following groups: 272 into Group B, 153 into Group C, 161 into Group D, and 97 into Group E. The supraspinatus occupation ratios of all partial-thickness rotator cuff tear groups were significantly lower than those of the control group. Furthermore, the supraspinatus occupation ratios of Groups C and E (≥ 50% partial-thickness rotator cuff tears) were significantly lower than those of Groups B and D (< 50% partial-thickness rotator cuff tears). However, the infraspinatus occupation ratio of only Group E was significantly lower than that of the other groups. The supraspinatus occupation ratios of both the ≥ 50% articular- and bursal-side partial-thickness rotator cuff tears were lower than those of the other partial-thickness rotator cuff tears. Conversely, the infraspinatus occupation ratio of only the ≥ 50% bursal-side partial-thickness rotator cuff tears was low. IV.