There are three anatomic findings that correlate with a patient risk for developing anterior acromial impingement : acromial shape, anterior downsloping of the acromion. To analyze the effect of anterior and lateral downslopings and subacromial interval to the impingement syndrome retrospectively, the authors reviewed 32 patients who performed MRI of the shoulder joint in the Dankook university hoipital.

Eighteen males & fourteen females were reviewed and the average age was 46.6 years old. There were 23 cases of impingement syndrome and 9 cases of control group. The authors analyzed oblique coronal images and oblique sagittal images in shoulder MRI.

In oblique coronal image, lateral downslopings of the acromion are -8.5° in impingement syndrome and 2.6° in control group. Difference of angles between impingement syndrome and control group is valuable in statistically (p<0.05). Subacromial intervals of shoulder MRI were 7.9 mm in impingement syndrome & 10.2 mm in control group (p<0.05). In oblique sagittal image, anterior downslopings of the acromion were 35.1° in impingement syndrome and 34.8° in control group. Difference of angles between impingement syndrome and control group is not valuable in statistically (p>0.005). The reason of this result may be due to incorrect cutting in that entire acromion can not be seen. Subacromial intervals were 7.7 mm in impingement syndrome and 10.3 mm in control group (P<0.05).

Decrease of the angle of the acromial lateral downsloping & the distance of subacromial interval may be one of the cause of the impingement syndrome.