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Abstract
Purpose
The shape of the acromion was analyzed radiologically to assess the effect on rotator cuff tears.
Materials and Methods
The rotator cuff tear group consisted of 91 patients with a mean age 55.6 years (range, 27-85 years) and the normal shoulder articular disease (control) group consisted of 100 subjects with a mean age of 42.9 years (range, 18-72 years). The lateral extension of the acromion and the lateral acromial angle were measured on an oblique coronal MRI, and the anterior covering of the acromionon was measured on a supraspinatus outlet view.
Results
The lateral extension of the acrominon of the rotator cuff tear group of patients and the control group of subjects was 0.70±0.07 and 0.64±0.10, respectively. The lateral acromial angle was 72.6±6.5° and 76.4±6.5°, respectively, and the anterior covering of the acromion was measured to be 0.55±0.13 and 0.51±0.14, respectively. In a comparison with the control group of subjects, the lateral extension of the acrominon of the rotator cuff tear group of patients was larger and the lateral acromial angle was smaller; these findings were statistically significant (p<0.001). In addition, the correlation coefficients of the lateral extension of the acromion to the lateral acromial angle in the rotator cuff tear group of patients and in the control group of subjects was -0.44 and -0.46, respectively; a statistically significant correlation was seeen (p<0.001).
Figures and Tables
Fig. 1
(A) Measurement of the anterior covering of the acromion from the supraspinatus outlet view. A reference line was drawn parallel to the axis of the humeral diaphysis from the anterior margin of the acromion. The anterior covering of the acromion (A/B) was defined by the ratio of the distance between the posterior margin of the humeral head to this reference line (A) over the distance between the anterior margin to the posterior margin of the humeral head (B). (B) The acromiohumeral distance on the oblique coronal MR image was measured as the shortest distance, in millimeters, between the undersurface of the acromion and the superior edge of the humeral head. (C) The lateral extension of the acromion (A/B) on the oblique coronal MR image was calculated by dividing the distance from the superior and inferior osseous margins of the glenoid cavity to the lateral border of the acromion (A) by the distance from the superior and inferior osseous margins of the glenoid cavity to the most lateral part of the proximal part of the humerus (B).
Fig. 2
The lateral acromion angle was measured as the angle between the line through the midsubstance of the acromion. The bony outline of the glenoid cavity on the oblique coronal MR image was measured immediately posterior to the acromioclavicular joint.
Fig. 3
Radiological comparison between the rotator cuff group of patients and the control group of subjects.
Fig. 4
Correlation between the lateral extension of the acromion and the lateral acromion angle. (A) The rotator cuff tear group of patients; (B) the control group of subjects. *Pearson correlation coefficient, †p-value.
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