抄録
Objective: It has been reported that the acromiohumeral interval (hereafter referred to as AHI) narrows in rotator cuff tears (RCT). In many cases, however, it does not. In this study we re-examined the clinical significance of the AHI.
Subjects and method: AHI was studied in the f ollowing: normal shoulders, as the control group,55 cases,55 shoulders; RCT (massive: 45·46; complete: 62·64; partial: 51·52), periarthritis: 57·66, and unstable shoulder: 63·85. The AHI was measured as the distance between the humeral head and the under surface of the acromion in a standingposition A-P view (internal and external rotations and neutral position) and scapular Yview.
Results: In normal shoulders the internal rotation AHI was the widest, at 8-16 mm (average 11.3 mm), indicating a significant difference from other roentgenographic directions and measurement values. Concerning the neutal-position measurements in normal shoulders and each disease condition, the AHI was 3-12 mm (average 6.9 mm) for the massive tear group, and this represented the most narrowing found and was significantly different from all of the other groups measured.
Conclusion:
1) The AH I in normal shoulders expands with internal rotation and narrows with external rotation.
2) In AHI measurements, important considerations are consistency of the positioning and the angle of roentgenography, and the most appropriate view is the neutral position.
3) With a roentgenographic method in standing-position, the AHI measu r e ment is clinically significant only in diagnosing a massive RCT.
4) As a diagnostic standard for a massive RCT, an AHI of 6 mm or less is appropriate, but allowances should be made for 52% of false negatives and approximately 18% of false positives.
